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Spaceflight – Wikipedia

Spaceflight (also written space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay “A Journey Through Space”.[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky’s work, ” ” (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.

Spaceflight became an engineering possibility with the work of Robert H. Goddard’s publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany.

Nonetheless, Goddard’s paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun’s V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]

Tsiolkovsky’s rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union’s chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev’s R-7 Semyorka missiles were used to launch the world’s first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]

At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.

Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds.A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.

A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.

A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles.

The most commonly used definition of outer space is everything beyond the Krmn line, which is 100 kilometers (62mi) above the Earth’s surface. The United States sometimes defines outer space as everything beyond 50 miles (80km) in altitude.

Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.

For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.

Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.

Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.

However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable “mission plateau” that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.

Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171km by 169km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.

Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet “instantaneous” launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.

Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is anotherway to explain the performance penalty associated with establishing the safe perigee of a parking orbit.

Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA’s Project Orion and Russia’s Kliper/Parom tandem.

Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.

Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.

The term “transfer energy” means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]

Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle and the heat energy instead ends up in the atmosphere.

The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute.Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land.The Space Shuttle glided to a touchdown like a plane.

After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.

Unmanned spaceflight is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Unmanned spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of unmanned spaceflight are robotic spacecraft (objects) and robotic space missions (activities). A robotic spacecraft is an unmanned spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.

Unmanned space missions use remote-controlled spacecraft. The first unmanned space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where animals but no humans are on-board are considered unmanned missions.

Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.

Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]

The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.

On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth’s atmosphere, sometimes after many hours. Pioneer 1 was NASA’s first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746mi) before reentering the Earth’s atmosphere 43 hours after launch.

The most generally recognized boundary of space is the Krmn line 100km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Krmn line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Krmn line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.

Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.

A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.

Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.

Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.

Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.

Spacecraft are vehicles capable of controlling their trajectory through space.

The first ‘true spacecraft’ is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.

Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle’s mass and increase its delta-v.

Launch systems are used to carry a payload from Earth’s surface into outer space.

All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16km) away being broken by the blast.[16]

Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.

In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]

In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of “weightlessness.” Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.

Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]

In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body’s waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.

Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). “Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth’s magnetic field, and our location in the Solar System.”[20]

Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.

Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.

In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.

Current and proposed applications for spaceflight include:

Most early spaceflight development was paid for by governments. However, today major launch markets such as Communication satellites and Satellite television are purely commercial, though many of the launchers were originally funded by governments.

Private spaceflight is a rapidly developing area: space flight that is not only paid for by corporations or even private individuals, but often provided by private spaceflight companies. These companies often assert that much of the previous high cost of access to space was caused by governmental inefficiencies they can avoid. This assertion can be supported by much lower published launch costs for private space launch vehicles such as Falcon 9 developed with private financing. Lower launch costs and excellent safety will be required for the applications such as Space tourism and especially Space colonization to become successful.

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Spaceflight – Wikipedia

Space exploration – Wikipedia

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2025, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical.Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21]In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be unique, being profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The National Aeronautics and Space Administration collaborated with six American corporations to develop new technologies for space exploration. NASA invested $44 million for different projects with the six companies[43]. These enterprises are Blue Origin in Kent, Washington ($10 million), Space Systems/Loral in Palo Alto, California ($2 million), United Launch Alliance in Centennial, Colorado ($10 million), Frontier Aerospace Corporation in Simi Valley, California ($1.9 million), Paragon Space Development and Corporation in Tucson, Arizona ($1.6 million), and Astrobotic Technology in Pittsburgh, Pennsylvania ($10 million). SSL and ULA have one more project each for $2 million. ULA has a third venture at $1.9 million. Blue Origin has a second project at $3 million[44].

Said technologies have the promise to benefit the commercial space sector significantly along with future missions of the NASA such as lunar lander and deep space rocket engine technology[45]. NASA also selected 304 business proposals from small enterprises in the United States for advanced research and technology. This will be for the first phase of the institutions Small Business Innovation Research agenda as well as 44 applications for Small Business Technology Transfer. The total cost is $43.5 million in grants. Choices support the forthcoming space exploration undertakings of NASA. Offers were picked out based on viability, technical value, credentials, and facilities of applicants[46].

According to an article published in Space News, the NASA plans to procure rides on miniature commercial lunar landers before the end of 2018. The Agencys deputy associate administrator (James Reuter) explained the thrust to shift the lander service to the Moon at the soonest possible time[47]. Fortune.com mentioned that in 2017, NASA entered into partnership with the BWXT Nuclear Energy Incorporated to design a reactor (apparatus) and develop fuel (nuclear-thermal propulsion engine) for deep space expeditions[48]. The choice of these corporations was based on NASAs competitive Tipping Point Solicitation. Any technology is classified as Tipping Point if the investment meant for flight or ground demonstration will lead to development of said platform and enhance the companys capacity to promote it in the market[49].

This solicitation focused on three strategic areas. According to an article that came pout in News Sky.com, these fields are expand utilization of space, increase access to planetary surfaces, and enable efficient as well as safe transport to space.[50] NASA launched the Parker Solar Probe spacecraft on August 12, 2018 from the Cape Canaveral Air Force Station (Florida). NASA officials revealed the exploration can turn out to be the fastest-ever man-made object that will go around the sun at around 430,000 miles per hour. This is 15 times faster compared to a zooming bullet[51]. Parker Solar Probe will provide a look at solar wind regions and assist scientists in determining how the sun can affect electronics, satellites, and space environment. It is a component of the agencys Living with a Star program in exploring features of the sun and earth affecting human life and society[52]. This mission was named after a prominent solar physicist, Dr. Eugene Parker from the University of Chicago responsible for predicting in 1958 that a solar wind existed. Dr. Parker explained in a research paper printed in the Astrophysical Journal how charged particles flowed endlessly from the sun[53].

Space Force

The Trump administration proposed a so-called United States Space Force that will assume a new and autonomous branch of the armed forces by 2020. Its creation will depend on the approval by Congress. The White House cited possible threats from enemies of the USA specifically China and Russia[54]. United States Vice President Mark Pence described the Space Force as proposed Space Force as possibly concentrating on matters such as the acquisition of military satellites that will secure American spacecraft from attacks while in orbit[55]. NASA Administrator Jim Bridenstine provided a background about other projects like the $10 billion James Webb Space Telescope project. According to an article released by the European Space Agency, the new launching date of this telescope is scheduled on March 30, 2021 following the conclusion of an impartial review. It was described as the most intricate and large-scale project ever conceived. The venture is a partnership between the European Space Agency, NASA, and Canadian Space Agency[56].

Operating 1.6 million kilometers from the Earth, Webbs objective is to look at space farther and deeper into time. The NASA is also working on the Space Launch System and Orion Deep Space Exploration. The SLS rocket will propel an unmanned Orion mission going to the moon and back sometime in the second half of 2019[57]. Companies like Blue origin owned by Amazons Jeff Bezos and Space Exploration Technologies owned by Elon Musk were reported as pouring in investments to space exploration projects in line with the increasing role of the business sector in this venture. In the United States, private investments have grown in commercial space firms during the last 10 years. These investments have reached $3.9 billion globally in 2017[58].

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[59] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[60] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[61]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[62]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[63]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[64]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[65] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[66] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[67][68][69] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[70] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[71] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 290days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[73]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[74]

R & D published an article in January 2018 which detailed how Space has turned out to be a destination for research and manufacturing[75]. One of the main reasons is its microgravity environment offering a rare opportunity for scientific exploration. Microgravity transforms biological systems as well as changes basic physical occurrences that facilitate innovative experiments[76].

From November 16 to 17 (2017), the 3rd Annual 2017 R&D Conference in Orlando, Florida tackled potentials of Research and Development in space[77]. Microgravity or weightlessness (zero gravity) takes place if people do not feel the effects of gravity. Technical experts explain that gravity as the force that magnetizes two bodies to one another. However, astronauts in space normally do not feel its effects[78].

National Laboratories under the Department of Energy is one of the active institutions for scientific innovations in the USA. It deals with wide-ranging and complicated R&D through a multidisciplinary methodology. These 17 facilities address crucial concerns related to science such as the beginnings of the universe and tackling climate change[79]. The United States Congress designated this institution as a national laboratory in 2005[80].

The 2005 NASA Authorization Act[81] authorized the US section of International Space Station (ISS) as a national lab. This entity will work to enhance life on Earth, strengthen relationships among National Aeronautics and Space Administration (NASA), relevant Federal agencies, and the private sector. This entity will also help promote STEM education[82] employing its ISS capabilities in the field of microgravity.

In 2011, the Center for Advancement of Science in Space (CASIS), a non-profit NGO or non-government organization, got the job to manage the research center with the focus on developing space research for improving life on the planet earth. This development gained more interest from researchers across the academe and industry to collaborate with the ISS National Laboratory[83].

For more than five decades, space innovation concentrated on gauging technologies associated with the Apollo Program. During that era, scientists believed man can really live in the moon[84]. However, only large organizations that employed many aerospace engineers participated in these ventures. The arrival of Internet Technology overturned the commercial space sector. Moreover, the global financial downturn more than 10 years ago constrained budgets of bureaucracies which subsidized space exploration projects[85].

However, only large organizations that employed many aerospace engineers participated in these ventures. The arrival of Internet Technology overturned the commercial space sector. Moreover, the global financial downturn more than 10 years ago constrained budgets of bureaucracies which subsidized space exploration projects[86]. Space colonization got underway in October 4, 1957 with the launching of Sputnik[87] and the Apollo Program [88](Apollo 11 in 1969) that brought human astronauts to the moon. Both the USSR and the USA built their space exploration missions from scratch. This approach influenced space missions for several years.

In 2010, the father and son tandem of Luke and Max Geissbuhler (who was only seven years old at that time) from Brooklyn (New York City) launched a unique model for exploring space. They launched an amateur weather balloon carrying an iPhone with high-definition camera meant to ascend 19 miles above the Earths surface and capture images in space. According to reports, it climbed up to the stratosphere where the camera managed to take photos of the Earths curve or arc as well as the dark outer space before the balloon exploded[89].

Students from Stanford University and PolySat[90], an autonomous research laboratory based in California Polytechnic State University, utilized the same cell components to design the so-called CubeSats[91] (10x10x10 centimeter buses) made to transport their science experiments to Low Earth Orbit (LEO) at a cheap cost[92]. These young students did not appreciate the consequences of their invention right away like the engineers from the United States Defense Advanced Research Projects Agency (DARPA) who encoded the Internet Protocol and Transmission Control Protocol in 1973. Unknown to them at that time, CubeSats initiated an accomplishment that genuine scalability originated from small, and not large satellites. This discovery transformed the space industry radically[93].

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Space exploration – Wikipedia

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Mercury Space Capsule Designed to put Americas 1st astronauts in space, Project Mercury began in October, 1958 as one of the 1st programs of National Aeronautics and Space Administration (NASA). The one man capsule was created by NASA, and built by McDonnell Aircraft. A total of 20 capsules were built, but only nine would fly in space; six with humans aboard, two with chimpanzees and one unmanned. Modified Redstone and Atlas missile were used to boost the capsules into space, and they helped America get a foothold on the space frontier. This particular Mercury Capsule, serial number 10, was not flown. It is on loan from the National Air & Space Museum.

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Space exploration – Wikipedia

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2025, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical.Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21]In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be unique, being profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The National Aeronautics and Space Administration collaborated with six American corporations to develop new technologies for space exploration. NASA invested $44 million for different projects with the six companies[43]. These enterprises are Blue Origin in Kent, Washington ($10 million), Space Systems/Loral in Palo Alto, California ($2 million), United Launch Alliance in Centennial, Colorado ($10 million), Frontier Aerospace Corporation in Simi Valley, California ($1.9 million), Paragon Space Development and Corporation in Tucson, Arizona ($1.6 million), and Astrobotic Technology in Pittsburgh, Pennsylvania ($10 million). SSL and ULA have one more project each for $2 million. ULA has a third venture at $1.9 million. Blue Origin has a second project at $3 million[44].

Said technologies have the promise to benefit the commercial space sector significantly along with future missions of the NASA such as lunar lander and deep space rocket engine technology[45]. NASA also selected 304 business proposals from small enterprises in the United States for advanced research and technology. This will be for the first phase of the institutions Small Business Innovation Research agenda as well as 44 applications for Small Business Technology Transfer. The total cost is $43.5 million in grants. Choices support the forthcoming space exploration undertakings of NASA. Offers were picked out based on viability, technical value, credentials, and facilities of applicants[46].

According to an article published in Space News, the NASA plans to procure rides on miniature commercial lunar landers before the end of 2018. The Agencys deputy associate administrator (James Reuter) explained the thrust to shift the lander service to the Moon at the soonest possible time[47]. Fortune.com mentioned that in 2017, NASA entered into partnership with the BWXT Nuclear Energy Incorporated to design a reactor (apparatus) and develop fuel (nuclear-thermal propulsion engine) for deep space expeditions[48]. The choice of these corporations was based on NASAs competitive Tipping Point Solicitation. Any technology is classified as Tipping Point if the investment meant for flight or ground demonstration will lead to development of said platform and enhance the companys capacity to promote it in the market[49].

This solicitation focused on three strategic areas. According to an article that came pout in News Sky.com, these fields are expand utilization of space, increase access to planetary surfaces, and enable efficient as well as safe transport to space.[50] NASA launched the Parker Solar Probe spacecraft on August 12, 2018 from the Cape Canaveral Air Force Station (Florida). NASA officials revealed the exploration can turn out to be the fastest-ever man-made object that will go around the sun at around 430,000 miles per hour. This is 15 times faster compared to a zooming bullet[51]. Parker Solar Probe will provide a look at solar wind regions and assist scientists in determining how the sun can affect electronics, satellites, and space environment. It is a component of the agencys Living with a Star program in exploring features of the sun and earth affecting human life and society[52]. This mission was named after a prominent solar physicist, Dr. Eugene Parker from the University of Chicago responsible for predicting in 1958 that a solar wind existed. Dr. Parker explained in a research paper printed in the Astrophysical Journal how charged particles flowed endlessly from the sun[53].

Space Force

The Trump administration proposed a so-called United States Space Force that will assume a new and autonomous branch of the armed forces by 2020. Its creation will depend on the approval by Congress. The White House cited possible threats from enemies of the USA specifically China and Russia[54]. United States Vice President Mark Pence described the Space Force as proposed Space Force as possibly concentrating on matters such as the acquisition of military satellites that will secure American spacecraft from attacks while in orbit[55]. NASA Administrator Jim Bridenstine provided a background about other projects like the $10 billion James Webb Space Telescope project. According to an article released by the European Space Agency, the new launching date of this telescope is scheduled on March 30, 2021 following the conclusion of an impartial review. It was described as the most intricate and large-scale project ever conceived. The venture is a partnership between the European Space Agency, NASA, and Canadian Space Agency[56].

Operating 1.6 million kilometers from the Earth, Webbs objective is to look at space farther and deeper into time. The NASA is also working on the Space Launch System and Orion Deep Space Exploration. The SLS rocket will propel an unmanned Orion mission going to the moon and back sometime in the second half of 2019[57]. Companies like Blue origin owned by Amazons Jeff Bezos and Space Exploration Technologies owned by Elon Musk were reported as pouring in investments to space exploration projects in line with the increasing role of the business sector in this venture. In the United States, private investments have grown in commercial space firms during the last 10 years. These investments have reached $3.9 billion globally in 2017[58].

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[59] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[60] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[61]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[62]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[63]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[64]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[65] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[66] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[67][68][69] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[70] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[71] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 285days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[73]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[74]

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Space exploration – Wikipedia

Space exploration – Wikipedia

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2025, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical.Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21]In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be unique, being profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 278days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

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Space exploration – Wikipedia

Zero Gravity Flight – Space Adventures

Aboard a specially modified Boeing 727-200, G-FORCE ONE, weightlessness is achieved by doing aerobatic maneuvers known as parabolas. Specially trained pilots perform these aerobatic maneuvers which are not simulated in any way. ZERO-G passengers experience true weightlessness.

Before starting a parabola, G-FORCE ONEflies level to the horizon at an altitude of 24,000 feet. The pilots then begins to pull up, gradually increasing the angle of the aircraft to about 45 to the horizon reaching an altitude of 34,000 feet. During this pull-up, passengers will feel the pull of 1.8 Gs. Next the plane is pushed over to create the zero gravity segment of the parabola. For the next 20-30 seconds everything in the plane is weightless. Next a gentle pull-out is started which allows the flyers to stabilize on the aircraft floor. This maneuver is repeated 12-15 times, each taking about ten miles of airspace to perform.

In addition to achieving zero gravity, G-FORCE ONEalso flies a parabola designed to offer Lunar gravity (one sixth your weight)and Martian gravity (one third your weight). This is created by flying a larger arc over the top of the parabola.

G-FORCE ONEflies in a FAA designated airspace that is approximately 100 miles long and ten miles wide. Usually three to five parabolas are flown consecutively with short periods of level flight between each set.

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Zero Gravity Flight – Space Adventures

Space exploration – Wikipedia

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2025, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical.Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21]In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be unique, being profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 278days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

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Space exploration – Wikipedia

Spaceflight – Wikipedia

Spaceflight (also written space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay “A Journey Through Space”.[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky’s work, ” ” (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.

Spaceflight became an engineering possibility with the work of Robert H. Goddard’s publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany.

Nonetheless, Goddard’s paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun’s V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]

Tsiolkovsky’s rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union’s chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev’s R-7 Semyorka missiles were used to launch the world’s first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]

At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.

Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds.A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.

A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.

A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles.

The most commonly used definition of outer space is everything beyond the Krmn line, which is 100 kilometers (62mi) above the Earth’s surface. The United States sometimes defines outer space as everything beyond 50 miles (80km) in altitude.

Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.

For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.

Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.

Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.

However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable “mission plateau” that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.

Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171km by 169km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.

Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet “instantaneous” launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.

Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is anotherway to explain the performance penalty associated with establishing the safe perigee of a parking orbit.

Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA’s Project Orion and Russia’s Kliper/Parom tandem.

Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.

Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.

The term “transfer energy” means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]

Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle and the heat energy instead ends up in the atmosphere.

The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute.Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land.The Space Shuttle glided to a touchdown like a plane.

After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.

Unmanned spaceflight is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Unmanned spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of unmanned spaceflight are robotic spacecraft (objects) and robotic space missions (activities). A robotic spacecraft is an unmanned spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.

Unmanned space missions use remote-controlled spacecraft. The first unmanned space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where animals but no humans are on-board are considered unmanned missions.

Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.

Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]

The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.

On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth’s atmosphere, sometimes after many hours. Pioneer 1 was NASA’s first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746mi) before reentering the Earth’s atmosphere 43 hours after launch.

The most generally recognized boundary of space is the Krmn line 100km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Krmn line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Krmn line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.

Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.

A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.

Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.

Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.

Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.

Spacecraft are vehicles capable of controlling their trajectory through space.

The first ‘true spacecraft’ is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.

Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle’s mass and increase its delta-v.

Launch systems are used to carry a payload from Earth’s surface into outer space.

All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16km) away being broken by the blast.[16]

Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.

In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]

In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of “weightlessness.” Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.

Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]

In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body’s waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.

Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). “Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth’s magnetic field, and our location in the Solar System.”[20]

Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.

Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.

In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.

Current and proposed applications for spaceflight include:

Most early spaceflight development was paid for by governments. However, today major launch markets such as Communication satellites and Satellite television are purely commercial, though many of the launchers were originally funded by governments.

Private spaceflight is a rapidly developing area: space flight that is not only paid for by corporations or even private individuals, but often provided by private spaceflight companies. These companies often assert that much of the previous high cost of access to space was caused by governmental inefficiencies they can avoid. This assertion can be supported by much lower published launch costs for private space launch vehicles such as Falcon 9 developed with private financing. Lower launch costs and excellent safety will be required for the applications such as Space tourism and especially Space colonization to become successful.

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Space exploration – Wikipedia

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2025, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical.Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21]In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be unique, being profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 265days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

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Space exploration – Wikipedia

Zero Gravity Flight – Space Adventures

Aboard a specially modified Boeing 727-200, G-FORCE ONE, weightlessness is achieved by doing aerobatic maneuvers known as parabolas. Specially trained pilots perform these aerobatic maneuvers which are not simulated in any way. ZERO-G passengers experience true weightlessness.

Before starting a parabola, G-FORCE ONEflies level to the horizon at an altitude of 24,000 feet. The pilots then begins to pull up, gradually increasing the angle of the aircraft to about 45 to the horizon reaching an altitude of 34,000 feet. During this pull-up, passengers will feel the pull of 1.8 Gs. Next the plane is pushed over to create the zero gravity segment of the parabola. For the next 20-30 seconds everything in the plane is weightless. Next a gentle pull-out is started which allows the flyers to stabilize on the aircraft floor. This maneuver is repeated 12-15 times, each taking about ten miles of airspace to perform.

In addition to achieving zero gravity, G-FORCE ONEalso flies a parabola designed to offer Lunar gravity (one sixth your weight)and Martian gravity (one third your weight). This is created by flying a larger arc over the top of the parabola.

G-FORCE ONEflies in a FAA designated airspace that is approximately 100 miles long and ten miles wide. Usually three to five parabolas are flown consecutively with short periods of level flight between each set.

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Zero Gravity Flight – Space Adventures

Cryptocurrency News: Looking Past the Bithumb Crypto Hack

Another Crypto Hack Derails Recovery
Since our last report, hackers broke into yet another cryptocurrency exchange. This time the target was Bithumb, a Korean exchange known for high-flying prices and ultra-active traders.

While the hackers made off with approximately $31.5 million in funds, the exchange is working with relevant authorities to return the stolen tokens to their respective owners. In the event that some is still missing, the exchange will cover the losses. (Source: “Bithumb Working With Other Crypto Exchanges to Recover Hacked Funds,”.

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Cryptocurrency News: Looking Past the Bithumb Crypto Hack

Ripple Price Prediction: xRapid Shows Success, But SEC Still Holds Power

XRP Prices Hang in the Balance
Ripple bears like to claim that XRP “serves no purpose” in its technology, but recent success with the “xRapid” software says otherwise. That—plus the continual “Is XRP a security?” debate—drove Ripple prices round and round in circles last week.

I see these two forces working in opposite directions.

Investors should be happy that xRapid is providing genuine benefits to businesses that dared to take a chance on XRP. But does it matter if the U.S. Securities & Exchange Commission (SEC) designates XRP a security?
xRapid Success
For the uninitiated, Ripple has multiple offerings. One is “xCurrent,” a.

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Ripple Price Prediction: xRapid Shows Success, But SEC Still Holds Power

Cryptocurrency News: Bitcoin ETFs, Andreessen Horowitz, and Contradictions in Crypto

Cryptocurrency News
This was a bloody week for cryptocurrencies. Everything was covered in red, from Ethereum (ETH) on down to the Basic Attention Token (BAT).

Some investors claim it was inevitable. Others say that price manipulation is to blame.

We think the answers are more complicated than either side has to offer, because our research reveals deep contradictions between the price of cryptos and the underlying development of blockchain projects.

For instance, a leading venture capital (VC) firm launched a $300.0-million crypto investment fund, yet liquidity continues to dry up in crypto markets.

Another example is the U.S. Securities and Exchange Commission’s.

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Cryptocurrency News: Bitcoin ETFs, Andreessen Horowitz, and Contradictions in Crypto

Ripple Price Forecast: XRP vs SWIFT, SEC Updates, and More

Ripple vs SWIFT: The War Begins
While most criticisms of XRP do nothing to curb my bullish Ripple price forecast, there is one obstacle that nags at my conscience. Its name is SWIFT.

The Society for Worldwide Interbank Financial Telecommunication (SWIFT) is the king of international payments.

It coordinates wire transfers across 11,000 banks in more than 200 countries and territories, meaning that in order for XRP prices to ascend to $10.00, Ripple needs to launch a successful coup. That is, and always has been, an unwritten part of Ripple’s story.

We’ve seen a lot of progress on that score. In the last three years, Ripple wooed more than 100 financial firms onto its.

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Ripple Price Forecast: XRP vs SWIFT, SEC Updates, and More

Cryptocurrency News: XRP Validators, Malta, and Practical Tokens

Cryptocurrency News & Market Summary
Investors finally saw some light at the end of the tunnel last week, with cryptos soaring across the board. No one quite knows what kicked off the rally—as it could have been any of the stories we discuss below—but the net result was positive.

Of course, prices won’t stay on this rocket ride forever. I expect to see a resurgence of volatility in short order, because the market is moving as a single unit. Everything is rising in tandem.

This tells me that investors are simply “buying the dip” rather than identifying which cryptos have enough real-world value to outlive the crash.

So if you want to know when.

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Cryptocurrency News: XRP Validators, Malta, and Practical Tokens

The Epic Relation Between Bitcoin and the Stock Market

Bitcoin Prices Are Less Independent Than You Think
Inside the world of cryptocurrencies, some truths go unquestioned: 1) centralization is terrible, 2) fixed money supplies are great, 3) cryptocurrencies are uncorrelated from stocks.

The last “truth” is now in question.

Many analysts, myself included, have raised questions about Bitcoin following the stock market before, but none of us made the case as strongly as Forbes contributor Clem Chambers.

Chambers recently used intraday trade charts to show that Bitcoin prices often follow the same patterns as the Dow Jones Index. (Source: “.

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The Epic Relation Between Bitcoin and the Stock Market

Cryptocurrency News: This Week on Bitfinex, Tether, Coinbase, & More

Cryptocurrency News
On the whole, cryptocurrency prices are down from our previous report on cryptos, with the market slipping on news of an exchange being hacked and a report about Bitcoin manipulation.

However, there have been two bright spots: 1) an official from the U.S. Securities and Exchange Commission (SEC) said that Ethereum is not a security, and 2) Coinbase is expanding its selection of tokens.

Let’s start with the good news.
SEC Says ETH Is Not a Security
Investors have some reason to cheer this week. A high-ranking SEC official told attendees of the Yahoo! All Markets Summit: Crypto that Ethereum and Bitcoin are not.

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Cryptocurrency News: This Week on Bitfinex, Tether, Coinbase, & More

Ethereum Price Forecast: Big Corporate Moves Could Bolster ETH Prices

Crypto Rally Slows Down
As I write this report, cryptocurrency prices are in the middle of a vicious tug of war between the bulls and the bears. And the bears are winning right now.

Most, if not all, of our favorite cryptocurrencies trended down over the last seven days, erasing the progress they made in earlier weeks.

Short-term volatility is completely overtaking the market, making it tough for existing holders of crypto assets.

But…

If you’re someone who is looking to enter the market, a sell-off is exactly the right time. How many times have I heard investors say, “If I had bought Bitcoin two years ago, I would have made [insert insane profits.

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Ethereum Price Forecast: Big Corporate Moves Could Bolster ETH Prices

Cryptocurrency Price Forecast: Trust Is Growing, But Prices Are Falling

Trust Is Growing…
Before we get to this week’s cryptocurrency news, analysis, and our cryptocurrency price forecast, I want to share an experience from this past week. I was at home watching the NBA playoffs, trying to ignore the commercials, when a strange advertisement caught my eye.

It followed a tomato from its birth on the vine to its end on the dinner table (where it was served as a bolognese sauce), and a diamond from its dusty beginnings to when it sparkled atop an engagement ring.

The voiceover said: “This is a shipment passed 200 times, transparently tracked from port to port. This is the IBM blockchain.”

Let that sink in—IBM.

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