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NASA Satellite to Travel to Mysterious Zone Where Earth Meets Space – The Wire

NASA launched a satellite Thursday to explore the ionosphere, a mysterious part ofEarths atmosphereon the edge of space.

The satellite shot into orbit from a plane flying over the Atlantic Ocean off the coast of the US state of Florida.

The satellite called Icon, or Ionospheric Connection Explorer, will transmit data intended to help scientists understand the physical processes at work where Earths atmosphere interacts with near-Earth space, NASA said.

Research by scientists at NASA has identified this region of near space as being in constant flux from solar storms above and weather below.

According to NASA, the ionosphere is a fluctuating layer of electrons and charged atoms and molecules ranging from 48 kilometers (30 miles) above the Earths surface to 965 kilometers (600 miles) above the ground at the edge of space.

This dynamic region grows and shrinks based on solar conditions.

Better communications and space missions

NASA said the Icon the satellite will transmit data intended to help scientists understand the physical processes at work where Earths atmosphere interacts with near-Earth space.

This protected layer, its the top of our atmosphere. Its our frontier with space, Nicola Fox, NASAs heliophysics division director, told the Associated Press, adding that the ionosphere is influenced by energy from extreme weather like hurricanes, along with solar storms.

Also Read:NASA Releases High-Resolution Images of Chandrayaan 2 Landing Site

According to NASA, electron particles in the ionosphere normally reflect radio waves back towards the ground, which enables long-distance radio communication. However, fluctuation in the electron levels can possibly cause radio communications to fail, reduce the accuracy of GPS systems, damage satellites and harm electrical grids.

The satellite can more directly analyze how solar storms affect Earth, which has implications for astronauts, radio communication, and GPS navigation systems.

NASA administrator, Jim Bridenstine, said in a tweet that the mission will provide key support for astronauts on future missions, including potentially returning to the moon.

This article was originally published in DW. You can read it here.

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William Shatner beams in with hit TV show at 88 – Japan Today

As Captain Kirk in the original "Star Trek" William Shatner went "where no man has gone before".

And now he is doing it again with a new hit U.S. television series, "The UnXplained", at the age of 88.

Shatner beamed into Cannes in southern France on Tuesday to beat the drum for the series -- which tries to explain some of the mysteries of the world around us -- at MIPCOM, the world's biggest entertainment market.

"A friend of mine once received a call from someone who had passed away," he said. Finding answers to such strange phenomena "was what this show is all about", he told reporters.

While it also tackles questions like why the universe is expanding, Shatner has little appetite for space travel these days with climate change threatening the Earth.

"I see all those ideas of colonizing the moon and Mars as fantasies to avoid thinking about the reality of (rising seas) and of being underwater in 50 years," he told reporters.

The Canadian-born veteran presents the new show on the History Channel, which will get a second series early next year.

He said reaction to the series, a mix of "Ripley's Believe It Or Not!" and a more straight science show, has been "fantastic".

Shatner has been fitting in filming around the U.S. and and European tours of his "Beam Me Up!" show where he takes questions from Trekkies after a screening of his 1982 movie, "Star Trek II: The Wrath of Khan".

A keen cyclist, he uses an electric bike to keep up with his family and said the key to a long life was to "keep taking on projects", such as his new memoir "Live Long and... What I Learned Along the Way".

The actor also released two albums last year, a country record and his Christmas album "Shatner Claus" which also featured Iggy Pop, Utopia star Todd Rundgren, singer-songwriter Judy Collins and ZZ Top's Billy Gibbons.

Not bad for a man who admits he can't actually sing.

Shatner said his recipe for longevity was "all the cliches... good genes, eat well, don't drink, don't smoke and go biking."

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10 Of The Best Space Travel Movies Of All Time, Ranked – Screen Rant

There is a corner of the Science Fiction genre devoted to the actual event that dazzles plenty of us - traversing the cosmos! From the very first Sci-Fi film, the epic 18 minute, A Trip To The Moon all the way to last years First Man; heading to the stars opens us up to all of the other wild adventures that have happened on screen, like Star Trek and Total Recall.

Related:10 Mind-Boggling Sci-Fi Movies To Watch If You Like The Matrix

With the exception of a few films on this list, most of these movies are still fiction. But theyre based in science fact. With help from scientists like Kip Thorne and Carl Sagan, these movies also do their best to maintain the integrity of the real science that might be involved to what the movies need them to do. Here are 10 Of The Best Space Travel Movies Of All Time, Ranked.

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For most sci-fi fans, Stanley Kubricks 2001 is the pinnacle of everything a science fiction movie should be. Co-written by one of the Big Three of Science Fiction, Arthur C. Clarke and based off of his short story, The Sentinel, there was literally nothing like it in cinema ever in 1968.

No matter what you think of the films actual plot about an ominous monolith affecting human evolution, the visual beauty of the film and many of the scenes and tropes it introduced still hold up over fifty years after its release and influence many films.

One of those many films and filmmakers inspired by 2001 and Kubrick is Interstellar, directed by unabashed Kubrick devotee, Christopher Nolan. The film takes place in a not too far off future where most of our worlds food resources are depleted, real history about space is replaced to keep people from looking up and NASA is hiding.

Related:10 Worst Cancelled Sci-Fi Show Cliffhangers

Until former pilot, Cooper and his daughter stumble upon them. Coops presented with the most arduous of missions - find a suitable replacement to bring all of mankind to its new home.

What if there was a whole team working to find and bring Tom Hanks home in Castaway? The Martian features Matt Damon as an astronaut, Mark Watney stranded on Mars.

After calculating that he has four years he has to survive until the next crew will touch down, Mark goes to work, growing his own potato farm. Once he gets a Pathfinder going is when NASA realizes that hes still alive and the journey to bring him home begins.

Weve all seen that big hero shot - all of the films stars walking in slow motion getting ready to do the task at hand. That shot was originated in the astronaut movie, The Right Stuff.

The movie tells the real-life story of the military pilots, including John Glenn, who helped test and refine the space program that would lead to Project Mercury, the first US manned mission into space.

Ed Harris did such a good job at playing and astronaut in The Right Stuff, that Ron Howard had tapped him to play flight director Gene Kranz in Apollo 13.

The film features Kevin Bacon, Bill Paxton, and the incomparable Tom Hanks as the three astronauts who were set to orbit the moon. Until an explosion happens on the shuttle, turning the mission into getting back to Earth safely.

Being lost in the vastness of space sounds absolutely terrifying. Combine that with your shuttle being broken. Veteran astronaut, Matt Kowalski and Dr. Ryan Stone are aboard the Explorer tasked with repairing the Hubble Telescope.

That mission goes haywire when debris smashes the Explorer forcing Matt and Ryan to find a way to a nearby station and find a way home. But they have to work fast, the debris field is orbiting them.

Based on Carl Sagans novel, Contact is about a different type of space exploration. Instead of physically traversing the cosmos, its up to Ellie Arroway and her team to research radio emissions and waves from space looking for signs of intelligent life.

Related:10 Great TV Shows That Re-Write Time & Reality

As she is about to be shut down, a sequence appears from the Vega system, light years away. Its one of the best movies that feature the research that actually goes into helping the astronauts.

After the success of Apollo 13, director Ron Howard teamed up with Tom Hanks for the HBO miniseries, From The Earth To The Moon. The ambitious series took a look at the lives of the men and women from the early Apollo missions.

The show was memorable for its use of archive footage of prior missions and news reports, mixed in with dramatic scenes as well to give the show a documentary type of feel while still being a high-stakes drama.

Thats one small step for man, one giant leap for all mankind might be the most famous quote of the 20th century. Neil Armstrongs life has been whittled down to that one epic moment (and can you blame history for doing so?!).

Related:10 Classic Science Fiction Novels That Need A Film Adaptation

But the personal triumphs and tragedies that led Armstrong to that one moment and Kennedys We Go To The Moon speech; the death of his daughter, is something that no one should ever have to endure.

While there is absolutely zero scientific research involved in the events of Galaxy Quest. But not every movie about space travel has to be scientifically accurate or filled with soon doom and gloom. Its also not every day that a parody of Star Trek is so well received that fans of that franchise actually rank it when theyre discussing their favorite Trek movies.

While the cast of the TV series Galaxy Quest, series star Jason Nesbit is approached by several members of the Thermian race contact him to get his crew together and help them stop an evil threat. They really think that Nesbit is his character, Commander Taggart and the rest of the actors are their characters. Its up to them to now stop pretending their astronauts and save the galaxy for real.

Next:10 Science Fiction Projects Currently In Development (And 10 Rumored)

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10 Of The Best Space Travel Movies Of All Time, Ranked - Screen Rant

Elon Musk Unveils SpaceX’s New Starship, Designed To Fly To The Moon, Mars And Beyond – NPR

A prototype of SpaceX's Starship stands at the company's Texas launch facility on Saturday. The Starship spacecraft is a massive vehicle designed to eventually be able to take people to the moon, Mars and beyond. Loren Elliott/Getty Images hide caption

A prototype of SpaceX's Starship stands at the company's Texas launch facility on Saturday. The Starship spacecraft is a massive vehicle designed to eventually be able to take people to the moon, Mars and beyond.

Speaking into gusts of wind at the SpaceX launch facility in Cameron County, Texas, on Saturday night, CEO Elon Musk talked up the space travel giant's newest innovation, the SpaceX vehicle Starship.

Musk spoke in front of a 50-meter, 200-ton Starship prototype, calling it "the most inspiring thing that I've ever seen."

He described unique design features of the vehicle and outlined plans to fast-track production of a Starship fleet. His hope, Musk said, is "to reach orbit in less than six months."

Since its founding in 2002, SpaceX has been working toward the goal of making space travel cheaper and accessible to would-be space travelers.

The Starship is the company's next foray: a large vehicle that could theoretically carry people into space, land safely back on Earth and be fit to turn around and fly again. Being able to return to space multiple times with "a rapidly reusable orbital rocket," Musk explained, is key to the company's plans.

"The critical breakthrough that's needed for us to become a space-faring civilization is to make space travel like air travel. With air travel, when you fly a plane, you fly it many times," he said.

Musk noted that Sept. 28 is the 11th anniversary of the commercial space travel giant's first big victory, when it reached orbit for the first time with one of its rockets, the Falcon 1. The company hit another milestone in March 2017 when it successfully relaunched its Falcon 9 rocket, after that small rocket had previously launched and relanded in 2016.

The goal now, Musk said, is to get the larger Starship, a vehicle that could carry people, to achieve the same feat.

"This thing is going to take off, fly to about 65,000 feet that's about 20 kilometers and come back and land. In about one to two months," he said. "It is really gonna be pretty epic to see that thing take off and come back."

Musk said the company is aggressively working to build the next iterations of the Starship prototype over the next five to six months.

SpaceX CEO Elon Musk gives an update on the next-generation Starship spacecraft at the company's Texas launch facility on Saturday. Loren Elliott/Getty Images hide caption

SpaceX CEO Elon Musk gives an update on the next-generation Starship spacecraft at the company's Texas launch facility on Saturday.

"The rate at which we will be building ships is going to be quite, quite crazy by space standards," he said.

To do this, he said, the company is ramping up production of the rocket's engines to reach a production target of building one new engine a day by early next year. If all goes to plan, he said, "we could potentially see people flying next year."

Musk made a point of thanking one of his investors, Japanese billionaire Yusaku Maezawa, who announced last year that he'd booked a trip as a private passenger with SpaceX for a voyage to the moon.

The reaction from NASA to Saturday's announcement was to bring attention to another less dramatic goal of SpaceX. The company has a partnership with NASA on the Commercial Crew Program, an enterprise intended to develop safe and affordable transportation of astronauts to and from the International Space Station. NASA Administrator Jim Bridenstine tweeted Friday, in advance of the Starship announcement, that he'd like to see "the same level of enthusiasm focused on the investments of the American taxpayer," noting that the Commercial Crew Program is years behind schedule.

Musk's Saturday speech was indeed filled with enthusiasm about space travel. He alluded to his ultimate goal of creating "a self-sustaining city on Mars." He said that while many problems on Earth need solving, "we also need things that make us excited to be alive and fired up about the future."

"Becoming a space-faring civilization, being out there among the stars, is one of the things that makes me glad to be alive," Musk said.

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Elon Musk Unveils SpaceX's New Starship, Designed To Fly To The Moon, Mars And Beyond - NPR

What If We Really Are Alone in the Universe? – Jacobin magazine

This article contains spoilers.

Two possibilities exist: Either we are alone in the universe or we are not, according to Arthur C. Clarke, the author of 2001: A Space Odyssey. Both are equally terrifying.

Much science fiction of the last century has assumed the first of Clarkes terrifying possibilities, that we are not alone that the cosmos is teeming not just with life, but with intelligent life. The primary questions this literature asked, in hundreds of different ways, were those such as: What would extraterrestrial intelligence be like? How would we recognize it? What would be its response to us? What would be our response to it?

Ostensibly about little green men, these were nevertheless profound questions answered in the pages of cheap paperbacks or by screen actors suited up in wobbly rubber masks. The questions were as serious as any asked by the authors of more respectable literary fiction. They reflected some of the deepest uncertainties that have troubled humanity since our first days on the African savannah, staring up at the great river of stars of the Milky Way: Why are we here? Where do we come from? And, above all: What is it to be a human? For us to ask what an alien soul would be like requires at least an assumption of what a human soul is like.

And yet for all our neuroscience, biochemistry, and philosophy, we still dont have good answers: terms such as intelligence, mind, and sentience stubbornly resist rigorous definition; the hard problem of consciousness how this state of self-awareness arises from (we assume) non-conscious chemicals remains as much of a hard problem as ever.

But the second of Clarkes two terrifying possibilities has, with a handful of exceptions, until recently remained unexplored within popular culture, particularly within cinema.

This is understandable. Writing in 1951 at the dawn of the Space Age in his book of popular astronautics, The Exploration of Space, Clarke said that we stood then at a pivot between two eras brought about by the advent of the rocket. This was the point at which the childhood of our race was over and history as we know it began Earths solar system being relatively young compared to the age of the galaxy (and certainly the universe), and industrial modernity a mere three hundred or so years old.

If an alien civilization had its version of an industrial revolution just a million years before ours or even just a thousand years and the universe appeared to have given billions of years worth of head starts to the presumed myriad of other planets with intelligent life they would be unfathomably advanced in comparison to us. Per Clarke and so many others, our childhoods end was the moment we would take our place among the adults of the cosmos.

It was an era of optimism, even presumption, about humanitys place among the stars. Of course we would have lunar colonies by the end of the twentieth century and Martian outposts somewhere around now. What made this optimism nevertheless terrifying was the unknown of what the adults of the cosmos would be like. Would they be peaceful? Would they be so advanced that they would treat us as we treat a fruit fly or a rat, or a lab mouse, or even Laika the space dog? Would they treat us as food, the way we treat cows and pigs? Would they carry with them genocidal new diseases the way Europeans did to the Americas? Would they be the disease? Would they demolish the Earth to make way for a hyperspace bypass?

James Grays Ad Astra is one of the first films to explicitly consider the terror of Clarkes second possibility. What if there are no aliens? What if, in the end, its just us?

It is the near future, a time of hope and conflict, as the opening title card tells us. Major Roy McBride (Brad Pitt) is in his space suit at work atop the International Space Antenna in low-Earth orbit when a mysterious surge from deep space nearly destroys the structure and knocks Roy off. Roys Felix Baumgartnerstyle opening free fall sequence, beating all HALO jumps of recent cinema for its success in inflicting vertigo, seems to be the point: we start and end with sequences in which the ground has been knocked out from beneath characters.

Earth and its outposts on the moon and Mars have been badly hit by what is termed the surge. Roy, the son of hero-astronaut Clifford McBride the first human to travel to Jupiter, the first to travel to Saturn is told by US Space Command that the source of the surge is the Lima Project in orbit around Neptune.

The Lima Project had been established under the direction of Clifford to extend the up-till-then fruitless search for intelligent life to the farthest reaches of the solar system. Sixteen years earlier, all communication with the project had ceased, and Clifford and his crew were presumed dead. Long since having come to terms with the grief of losing his father, Roy is now informed by USSPACECOM that they believe Clifford is alive and possibly responsible for the surge. We then follow Roy through the solar system, visiting the moon, Mars, a ship in distress, and eventually Neptune, on his mission to reestablish contact with his father.

Roy is dispassionate, level-headed, almost emotionless. Regardless of what threat arises, his heart rate never moves beyond 80 BPM. He passes without incident all but one of the automated psychological evaluations he must regularly take. He has been picked precisely for this, well, inhuman reserve. Confronted with the claustrophobic agoraphobia of a tin can in an infinite vacuum and the thousand other extreme dangers of space travel, Roys heart is unmoved. A perfect astronaut.

The common reading of the film has been that all this is really about a sons attempt to reach out to a distant father, of the inability of us all to understand the other. What greater distance can a son and an absent father travel than that between Earth and Neptune? Only connect! as E. M. Forster insisted.

It is not so much that this is wrong, but that it is too abstract.

It is true that when Roy finally reaches his father, Clifford blankly tells him that he was content to leave his son and wife because the search for intelligent life was so much more fulfilling, so much more important. But Cliffords soliloquy also tells us why communication with Earth was disrupted, what happened to his crew, and why he has in effect gone mad.

We see flashes of Europa, Enceladus, Titan, Ganymede all the sites that in the real world today we reckon are the best hope for discovery of life in the solar system as Clifford recounts how no matter where they looked, they found no life. After years of searching, his crew wanted to concede that there was no life out there and to return home. Clifford insisted that absence of evidence is not evidence of absence and killed his crew when they mutinied, wanting the search to continue.

In a universe where we are the only intelligent life there is, that there has ever been, and the Earth the only place where any life has been, intelligent or otherwise, Forsters command to only connect becomes ever more imperative. If its only us, it makes us even more important, so much more precious than we imagined. It casts us humans not merely as one sentient species among billions, but as the sole way in which the universe became aware of itself. It is the story of the universe becoming conscious through us.

Without such consciousness, there is no point, no purpose to the universe. Nothing matters. There is no ought in physics, only an is. There is no ought in biology either, no progressive direction to evolution (what is termed orthogenesis). Even if life on earth were to continue, but continue without us, still nothing would matter, as it is true that while individual organisms struggle to continue to be, life does not care whether it exists (life on Earth, at least twice before, came close to wiping itself out). An Earth without humans but still with other life would only matter insofar as there would at least remain a chance for intelligent life to reemerge. Only intelligent life can create purpose.

There is a sequence midway through Ad Astra where Roy comes across a ship in distress, the exploration of which reveals that its crew have all been killed by raging baboons, the escaped subjects of a scientific experiment. It is something of a horror-filled series of scenes, appearing at first to be from a different, less meditative film than Ad Astra, perhaps an Event Horizon or even Alien.

Though appearing out of place, the baboon sequence could be read as an allegory for how the inhospitable environment of space will inevitably make us crazy. But a still deeper reading asks, could it not instead be a rhyme for the sheer terror of realizing that we inhabit a lonely cosmos where humans are the only intelligent life? Is such a realization any less vertigo-inducing, any less deranging?

If the film is understood this way, then the sequence where Virgin Galactic takes our hero to the moon (charging $125 for a blanket and pillow) has a more expansive meaning than at first glance. As does the brief sequence on the moon in which we see a base not filled with the scientific equipment of a 70s-era Doctor Who, Lost in Space, or Star Trek, but instead dominated by the likes of Applebees, Subway, DHL, and tourist-trap cringe. If the film were primarily a critique of the banality of a capitalism now spread throughout the solar system, much more time would have been spent by the filmmaker in this space. But these scenes are very brief.

Grays critique is indeed one that laments what capitalism is doing, as we know from his comments to the press. If we were having this conversation in 1960, we could talk about the counterweight of the communist or socialist dictatorship bloc. But today theres not really a counterweight to market capitalism, he told CNET. Its an unstoppable force. In the developed nations, the gap between the richest and the poorest is growing ever larger. And why would we project that space would be any different?

But the films concern with capitalism appears to plunge deeper. If capitalism, unconscious force that it is, would extinguish human existence so long as the commodities that threatened such extinction (such as, for example, fossil fuels) continued to be profitable in the absence of some non-market intervention, then it is not merely the human race that is threatened, but a conscious universe itself. Capitalism would turn a lonely cosmos into a soulless cosmos.

Ad Astra may be among the first films to explicitly place Clarkes lonely cosmos possibility at its heart, but a raft of hard sci-fi films in the last few years, auteur-driven works set in space such as Duncan Joness Moon, Alfonso Cuarns Gravity, Christopher Nolans Interstellar, Ridley Scotts The Martian, and Damien Chazelles First Man, have also begun to consider the same question but posed in a different way: If the rest of space is as incorrigibly inhospitable as it increasingly appears to be, does it make sense to even travel to other worlds? This is just another way of saying that there may as well be no other aliens.

Duncan Joness Moon (2009) strips the moon of all the romance and adventure of NASAs lunar landings. It is a desolate, companionless, (literally) repetitive, deadly, uninviting place. The moon is above all boring. For the solitary lunar miner clone Sam Bell (Sam Rockwell), space has never been about the extension of human freedom beyond the trap of our planets gravity well. Instead, freedom comes via escape to Earth.

Few films have so realistically described so many different threatening ways that the vacuum of space can kill us the different ways that our technological efforts to contain those threats can still kill us as Cuarns Gravity (2015). Unlike many films where the tension at least partially dissipates, the danger is unceasing until our hero, Ryan Stone (Sandra Bullock), splashes down on Earth and crawls ashore. She is finally safe to breathe without fear of her oxygen ever running out thanks to the marvel of the Earths current ecosystem. As we, the audience, feel at this point as though we can finally take a breath as well, Cuarn is telling us through our own physiology that the Earth is the only home we will ever have. In this way, Gravity is one of the most pessimistic of the recent crop of high-realist space dramas about the possibilities of the extension of human civilization beyond the Earth.

The heroes of Interstellar survey three exoplanets that are candidates for a human exodus from a dying earth, but they turn out to be an inhospitable ocean planet, a desolate ice planet, and a barely survivable desert planet. When all appears lost, the hint of some unfathomably advanced alien race saves humanity, but via a wibbly-wobbly, timey-wimey resolution drawing on the work of Nobel Prizewinning theoretical physicist Kip Thorne, we find that the aliens are actually us. While the film does not explicitly investigate the meaning of a lonely cosmos, this appears to be a background assumption.

This shift from the cosmic optimism of a Star Trek or a Doctor Who, and certainly of the days of the Space Race, about humanitys place among the stars, to a much more guarded stance or even pessimism should be no surprise. This new cosmic realism comes at a vertiginous moment for humanitys understanding of our relationship to the planet and to the rest of the cosmos.

As far back as the sixteenth century, Italian philosopher and Dominican friar Giordano Bruno argued that the stars above us were in fact stars surrounded by their own system of planets and they too could be presumed to be inhabited (for why would God go to all the bother to create a world, only to leave it empty?) a theological position known as cosmic pluralism. This extension of the Copernican heliocentric model of the solar system that toppled humanitys place at the center of the universe was of course a heresy.

The science-fiction worlds of television and film often operated according to the same presumption, albeit stripped of its theism, and enjoyed similar gravity to Earth, similar atmospheric pressure and chemistry. This is probably less a willful disinterest in planetary science than the product of it being much cheaper and more convenient to use an abandoned gravel pit as a set than to represent the much more fantastical reality of other worlds. Science-fiction novels, of course, have no such budget restrictions, and thus have always had greater imaginations.

Nevertheless, all this had been speculation until relatively recently. We didnt even know for sure if there were any planets beyond our own solar system before the first confirmed detection of an exoplanet in 1992. As of the time of writing, however, there have been some four thousand exoplanets that have been confirmed.

At first, this seems to buttress historys sequence of Copernican realizations including the recognition that our sun is just one of billions of stars in the Milky Way, the discovery of other galaxies, the development of the theory of evolution by natural selection that have repeatedly toppled humanity from the pedestal we thought we occupied, requiring us to be ever more humble. Once again, having found that stars with planets surrounding them are common, we must be ready to admit we are nothing special. As Stephen Hawking put it: We are just an advanced breed of monkeys on a minor planet of a very average star.

The question of how uncommon Earth is, and even how uncommon life is, may be resolved as soon as the next decade, when the next generation of telescopes comes online. The composition of the atmospheres of large exoplanets are already being examined via light from stars as it passes through those atmospheres. When a planet crosses, or transits, the path of light from its parent star, such starlight gets filtered through the atmosphere, allowing us to analyze the emission and absorption spectra of its gases, including biosignature gases those that are produced by life such as molecular oxygen and accumulate to levels that can be detected. Right now, we can only do this for Jupiter-size planets, but with larger observatories such as the James Webb Space Telescope expected to launch in 2021, we should be able to perform such investigations for smaller, rocky worlds in the habitable zone that come closer to Earth analogues (although likely still too big to be true analogues).

This is why MIT planetary scientist Sara Seager believes characterization of exoplanet atmospheres is such a profound endeavor: When and if we find that other Earths are common and see that some of them have signs of life, we will at last complete the Copernican Revolution a final conceptual move of the Earth, and humanity, away from the center of the Universe.

At the other end of the cosmic spectrum, from the vast down to the microscopic, biology appears to give us tremendous hope that Seager is right. Extremophile bacteria and other microbes that flourish under conditions of extreme heat, cold, dryness, acidity, alkalinity, salinity, radioactivity, pressure, and the presence of heavy metals are closely studied by astrobiologists, as their habitats may be similar to the conditions on other worlds. Everywhere we look on Earth, we find life. In the last decade or so, researchers have begun to plunge into the deep biosphere life far below the surface, drilling some 2.5 kilometers into the seafloor and some five kilometers down continental mines and boreholes. This subterranean Galpogos is home to an estimated 70 percent of the worlds bacteria and archaea, a realm where the records describing what were thought to be the absolute limits of life on Earth keep getting broken.

Nevertheless, there are researchers who reckon that perhaps this time there has been an excess of Copernican humility.

The announcement in September of the identification of the first habitable-zone planet we know to contain water outside the solar system prompted a flurry of breathless articles reporting the discovery of a supposedly habitable exoplanet and only 110 light-years away, basically next door by astronomical standards (even if it would take a probe like Voyager some 2 million years to get there). But K2-18b is estimated to be almost three times the size of Earth and have almost nine times the mass. It was almost classified as a mini Neptune rather than a super Earth, and perhaps it should have been in order to avoid media hyperbole.

The size suggests it has an extremely thick atmosphere, much of which is hydrogen gas. At its rocky core (if it has one), the pressure from that vast atmosphere would be thousands of times greater than at Earths surface, with temperatures hitting 2700C (5000F). Under these conditions, as Harvard exoplanet atmospheric specialist Laura Kreidberg has been at pains to stress, complex molecules necessary for life cannot form. Out of all the four thousand, while this is the best candidate for habitability that we know right now, according to the researchers, its still not habitable, and certainly no analogue Earth.

The infamous Fermi paradox formulated by Italian physicist Enrico Fermi asks: If there are billions of suns like ours in the galaxy, many of which are billions of years older than our solar system, and Earth is so unexceptional, then at least some of these ancient worlds must have achieved advanced technology eons before us so then where is everybody? Why, when we look up at the stars, do we not see any evidence of this? Why have we not been visited?

Various answers have been proposed, including, most darkly, that once a civilization reaches a sufficiently advanced level of technology, it inevitably wipes itself out, perhaps via nuclear weapons, perhaps by combustion of fossil fuels.

Director of the Columbia Astrobiology Center Caleb Scharf, in his 2014 book The Copernicus Complex, has another explanation. He counters Hawkings presumption about our mediocrity, noting that, in fact, the sun is not at all very average, and that the architecture of our planetary system in terms of orbits, spacings, and occurrence of types of planets is something of an outlier.

Astrophysicist John Gribbin makes a similar argument in his 2011 book Alone in the Universe, that a chain of improbable coincidences had to occur for intelligent life to exist. Any earlier in the history of the galaxy, and our planetary system would have too few metals to form life. We appear to be not just in the goldilocks zone in our local system but in the galaxy, too: if we were too near the center, itd be too crowded, with near-sterilizing events such as supernovas and gamma-ray bursts from merging neutron stars more common; if we were too far out, again, the lack of metals would sink us.

The presence of the moon and Jupiter may also play a key role in keeping us safe. Here on Earth, while life got started perhaps just a billion years after the earth was formed, it took 2 billion years between the first emergence of bacterial and archaean life and eukaryotic life (cells with true nuclei), and another billion again before eukaryotes got friendly enough to bunch up into multicellular life.

Compared to the universes 13.8-billion-year-old life span so far, 4 billion years for things to kick off hints at how unlikely this may be. And it still took until a bare 550 million years ago during the Cambrian explosion for multicellular life to proliferate into the variety we are familiar with. Gribbin reminds us that we still do not know why this most significant moment in the fossil record happened, and thus how likely it might be anywhere else.

The existence of some organisms with every higher biological complexity does appear to increase over time (in other words, the variance of complexity expands), but the most common type of complexity remains basic: the majority of species are simple prokaryotes. And within our own prehistory and history, there have been a number of unlikely events, including that some seventy thousand years ago, due to some catastrophe, humanity was reduced to just a thousand individuals. Gribbins hunch is that simple life may exist somewhere else in the Milky Way, given how rapidly life first appeared on Earth, but we are the only technological civilization in the galaxy.

Of course, there are lots of other galaxies, one might say. But given the vastness of our own galaxy, even this is still rare and precious enough. The point, in any case, is rather that we live in an interesting time, where recent discoveries push in one direction suggesting that life is utterly common and unexceptional, and other recent discoveries push in the other direction, suggesting how rare and precious life particularly conscious life truly is.

However, these discoveries by astronomers, cosmologists, and planetary scientists that are filtering their way into popular culture, sculpting our notions of what is believable on-screen, are not the only such influence.

Here on Earth, our relatively new understandings of ecosystems new at least since the Space Age and how humanity is endangering the geologically brief, ten-thousand-year window or so of conditions that have allowed us to flourish, and our even newer understanding of how the human body is an ecosystem itself, a microbiome, are surely also prompting the emergence of this new cosmic realist cinema. Certainly, many of these films address directly or indirectly climate change and related ecological challenges. We can see this in the agricultural and extreme weather background of Interstellar, the opening title card of Ad Astra speaking of a time of hope and conflict, and, most explicitly, the ecological catastrophe of the Danish-Swedish low-budget but still high-realist Aniara (2018), a melancholic tale of a Mars-bound space-faring cruise ship gone adrift for years without hope of rescue. In the latter, the passengers become addicted to a holodeck-like room powered by an artificial general intelligence that feeds them dreams of nature on Earth like how it used to be.

And if we are the only self-aware life in the galaxy, then preservation of the ecological conditions that have allowed humanity to flourish suddenly become even more important. We are not merely saving ourselves but saving a universe that is becoming aware of itself. Our series of profound global biocrises immediately have cosmic resonance.

When we think of ecology, we immediately think of external nature, but in recent years, microbiology has shown how each of us is as much an ecosystem, including human cells and microbial cells, a great many of which we cannot survive without, as we are an individual. Ecology and biology increasingly even trouble the notion of individuality, or at least recognize that biological individuality comes in degrees and can be realized at multiple levels, emerging as a product of the coming together of what were previously distinct entities. Our multitudinousness, as science writer Ed Yong puts it, connects us to the wider, global ecosystem not in some abstract or poetic way but directly. In truth, it is hard to make a hard distinction between ourselves and external nature. This, in turn, means that for any extended period of time external to the earth, it is not enough for humans to strap themselves inside one of David Bowies tin cans, but rather that we have to take our ecosystems with us, at least in some significant part.

But then how can we create mini ecosystems separated from the earth that are capable of sustaining themselves and thus us in perpetuity? We dont know yet. Efforts to create complex closed ecological systems have proven extremely difficult.

Kim Stanley Robinsons remarkable ecological novel disguised as space-based hard science fiction, Aurora, is a thought experiment about such an effort on a grand, generation-starship scale. After seven generations and 160 years, the biomes in the ship begin to break down as the rate of evolutionary change of bacteria and macroscopic organisms is hopelessly mismatched. One walks away from the book confronting the possibility that human colonization of other worlds is somewhere between impossible and formidably more difficult than our earlier science fiction ever imagined.

There are a lot of people, even powerful, influential people, who seem to think that the goal of humanity is to spread itself, Robinson says of the ideas behind Aurora. Maybe theres only one planet where humanity can do well, and were already on it.

However, the interrogation of Clarkes dilemma by Ad Astra surely imposes the opposite conclusion to that of Robinson, even if one accepts Robinsons powerful ecological argument about the profound difficulty of taking our ecosystem with us. On a geological scale, life on Earth may be robust. The planet has passed through far worse than what humanity is currently throwing at it. Instead, it is the goldilocks conditions that support humanity that are under threat as a result of the irrational production incentives of the market. But even a geological scale is puny compared to a cosmic scale. And on a cosmic scale, life on Earth is indeed precarious.

In about 600 million years, the suns increase in solar luminosity will set in chain a series of events that will kill off most plants, the support base of much complex life. Unicellular life will then predominate until about 3 billion years from now, and then it too will die out. Thus, the imperative that commands that we preserve and enhance the ecological conditions that have allowed human consciousness to flourish, in other words, to work to prevent climate change and biodiversity loss, also commands us to preserve that consciousness beyond the end of days of the earth, especially if, as Clarke and Ad Astra wonder, we are the sole conscious inhabitants of the galaxy or the cosmos.

Born in the year of the first moon landing, director Gray told CNET that he laments the loss of the tremendous aspirational power of humankinds quest for space. Elsewhere, Gray has said that the character of Clifford McBride, obsessed with finding intelligent life, wasnt just the ogre that there was also something beautiful about his dream. The tragedy of Clifford instead is that He never found beauty in the idea that human beings are what matter. The idea of striving is what matters.

The lunar landing is the greatest achievement in the history of the human race, Gray says of this striving. I think we take it for granted now ...What was lost was the will because the whole vision of space exploration was essentially motivated by the desire to beat the Russians to the moon. And once the United States did that, we stopped caring.

Grays comments are echoed by the protagonist of Interstellar. While that piece of cosmic realism may be despairing about the future of humanity on Earth, it blames this failure not on the hubris of mankind but on our abandonment of audacity. Cooper at one point laments how We used to look up at the sky and wonder at our place in the stars, now we just look down and worry about our place in the dirt. The line appears to be what remained after editing of a longer aspirational monologue that was still used in trailers:

Weve always defined ourselves by the ability to overcome the impossible. And we count these moments. These moments when we dare to aim higher, to break barriers, to reach for the stars, to make the unknown known. We count these moments as our proudest achievements. But we lost all that. Or perhaps weve just forgotten that we are still pioneers. And weve barely begun. And that our greatest accomplishments cannot be behind us, because our destiny lies above us.

And the response of Mark Watney in The Martian to the harsh indifference of Mars is not to curse his lot, but to recognize how important the work of space exploration and colonization is. At that films darkest moment, when Watney becomes all but certain that he is going to die alone on the planet, he transmits a message to his superior asking that she speak to his mom and dad about the role of his work in a vast humanist project: Please tell them I love what I do ...and that Im dying for something big and beautiful, and greater than me. Tell them I said I can live with that.

That is, this trend of cosmic realism is not only a cinematic representation of an emerging, stark realization about our possible uniqueness in the cosmos, about the universes profound inhospitable desolation, and about humanitys inseparability from our ecosystem. It responds to the psychic destabilization this realization causes not with retreat, but with a renewed commitment to humanity and to space.

Of all these films, Ad Astra is perhaps the most aptly named, taken from the Latin phrase ad astra per aspera, through struggle to the stars. Our task in this cosmos, to maintain ourselves and flourish so that the universe will continue to have meaning, will forever be riddled with challenge. The struggle will always continue.

Continued here:

What If We Really Are Alone in the Universe? - Jacobin magazine

Ad Astra shines a light on the future of space travel – The Wellesley News

James Grays Ad Astra follows astronaut Roy McBride, played by Brad Pitt, as he searches for his father and the source of dangerous power surges in deep space. The film has a beautiful visual aesthetic that harkens back to classics such as 2001: A Space Odyssey and sets itself apart from other films in the genre by venturing even farther into space. The characters journey eventually brings him to Neptune, at the edge of our solar system.

The film opens with Pitts character working on what seems to be an extension of the International Space Station (ISS). The visuals and sound editing coupled with the directionless and lethargic movement of Pitts character accurately recreate space. As our protagonist and his colleagues effortlessly float through space, one cannot help but feel the awe of their insignificant presence against the backdrop of Earth. It is not until all of the ambient noise suddenly drains out and is replaced by the low rumbling of a power surge that the audience finally realizes what structure they are working on: an antennae from Earth that is so tall, it reaches into low Earth orbit. The surge runs along the course of the structure, and Pitt watches as his colleagues are blown off of it and sent plummeting to the ground. Pitts character is forced to jump off seconds before the power surge reaches his position. In the following moments of him spinning through the Earths upper atmosphere and down towards the ground, we learn what this film has in store.

This film is very slow, both literally and figuratively. The characters move slowly as if swimming through water, as they walk along the outsides of space stations and shuttles. However, this slow feel also extends to the plot as Brad Pitt delivers meandering monologues about the nature of humanity. Though this film is technically science fiction due to its setting, there is no doubt that it is more of a drama and an intimate look at human nature. Pitts character is known for his fearlessness; however, this has made him an uncaring person who pushes others away. His wife, played briefly by Liv Tyler, barely knows who he is anymore, and he does not have any kids. Instead, he has devoted himself completely to the exploration of space; however, deep down, he does not care much for it beyond the connection it forges between him and his father. When Pitts character is finally reunited with his father, he realizes that the man is more similar to an alien than a human, as he no longer considers Earth to be home. The father so consumed with exploring space and discovering what lies in the expansive universe that when Pitt tries to save him, he untheters himself and floats off into the void.

Ad Astra uses the exploration of deep space as a vehicle to tell a story about humanity. The nuanced performances of the cast coupled with the awe-inspiring scenery raise questions about the point at which a human becomes an alien and suggest that the answers may lie in the void.

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Ad Astra shines a light on the future of space travel - The Wellesley News

Scientists extend shelf life to benefit army and space travel – Food & Drink International

Scientists have developed a way to triple the shelf life of ready-to-eat macaroni and cheese which, they say, could benefit everything from space travel to military use.

Currently, plastic packaging can keep food safe at room temperature for up to twelve months, but the Washington State University (WSU) researchers demonstrated in a recent paper they could keep ready-to-eat macaroni and cheese safe and edible with selected nutrients for up to three years.

We need a better barrier to keep oxygen away from the food and provide longer shelf-life similar to aluminium foil and plastic laminate pouches, said Shyam Sablani, who is leading the team working to create a better protective film.

Weve always been thinking of developing a product that can go to Mars, but with technology that can also benefit consumers here on Earth.

In addition to having space travel in mind, the researchers are working closely with the US Army, who want to improve their Meals Ready to Eat (MREs) to stay tasty and healthy for three years.

In taste panels conducted by the Army, the mac and cheese, recently tested after three years of storage, was deemed just as good as the previous version that was stored for nine months.

The science behind longer shelf life

The food itself is sterilised using a process called the microwave-assisted thermal sterilisation (MATS) system, developed by WSUs Juming Tang.

The food must be sterilised in plastic, since metal, like tin cans, cant be microwaved and glass is fragile and not a preferred choice of packaging for MREs. Glass is also too heavy for military or space uses.

Adding a metal oxide coating to a layer of the plastic film significantly increases the amount of time it takes for oxygen and other gases to break through.

The metal oxide coating technology has been around for almost 10 years, but it develops cracks when subjected to sterilization processes. That eventually compromises the food shelf-life, Sablani said.

WSU researchers have been working with packaging companies to develop new films that keep oxygen and vapor out longer.

The packaging films are made up of multiple layers of different plastics. These few-micron thin layers have different purposes, like being a good barrier, good for sealing, good mechanical strength, or good for printing, Sablani said.

We are excited that an over-layer of organic coating on metal oxide helped protect against microscopic cracks, he said.

Multiple layers of metal oxide coating have also increased the barrier performance. Our research guided development of newer high barrier packaging.

To ensure the process works fully, the Army plans to do testing under field conditions. So these new MREs will be stored longer, then sent to deployed soldiers to eat in the field.

If they like the taste of the packaged food there, then thats the ultimate test of new films, Sablani said.

The team doesnt wait the three years to test the results of each new film. Keeping the packaged food in a 100-degree Fahrenheit incubator rapidly speeds up the food quality changes at a consistent rate. Six months in the incubator is equivalent to three years at room temperature, while nine months is the equivalent to nearly five years, Sablani said.

The final frontier

For space travel, its not really possible to field-test for a trip to Mars. But Sablani plans to reach out to NASA to talk about how to test the WSU films to make sure that packaged food stays edible on a space mission where failure isnt an option.

NASA knows about our work, but were just now getting to the point where we can talk to them with a proven product, Sablani said.

We hope to work out a way to test these products on the International Space Station in the future to show that the food is safe after long-term storage.

NASA will require storage of up to five years for food, so thats what the team is working on now. They are currently aging other recipes that will be taste tested once they reach the five-year mark.

Several types of mission plans have been proposed for a trip to Mars. The five-year food storage includes some built-in safety requirements, Sablani said.

It may involve an approximately nine-month travel time from Earth to Mars, about five hundred days on or orbiting Mars, and a travel time of about nine months to return to Earth.

The extra storage time is necessary in case the mission is delayed and explorers must stay longer.

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Scientists extend shelf life to benefit army and space travel - Food & Drink International

Space travel across the universe could be faster than speed of light with Warp Drive – Express.co.uk

Faster Than Light (FTL) technology has been constricted to the realms of science fiction, but it is theoretically possible, according to one researcher. The research, carried out by Joseph Agnew, an undergraduate engineer and research assistant from the University of Alabama in Huntsvilles Propulsion Research Center (PRC), builds on the expertise of Mexican physicist Miguel Alcubierre. Mr Alcubierre established a concept for an FTL system back in 1994 which was built on Einsteins field equations.

Essentially, the equations dictate that space, time and energy all interact and Mr Alcubierre believed they could be manipulated to travel faster than the speed of light a staggering 299,792,458 metres per second.

Mr Alcubierres warp drive technology would involve stretching the fabric of space-time to form a wave.

Theoretically, the space ahead of the ship would contract while behind it would expand. This would mean that the ship is not moving, but moving space-time itself.

It has now become known as the Alcubierre Metric which involves riding the wave of space-time to achieve FTL travel.

The theory seemed improbable at the time, but the discovery of gravitational wave proved that space-time can warp, as per special relativity.

Mr Agnew told Universe Today: The historically theoretical nature of the idea is also itself a likely deterrent, as its much more difficult to see substantial progress when you are looking at equations instead of quantitative results.

In the past 5-10 years or so, there has been a lot of excellent progress along the lines of predicting the anticipated effects of the drive, determining how one might bring it into existence, reinforcing fundamental assumptions and concepts, and, my personal favourite, ways to test the theory in a laboratory.

The LIGO discovery a few years back was, in my opinion, a huge leap forward in science, since it proved, experimentally, that spacetime can warp and bend in the presence of enormous gravitational fields, and this is propagated out across the Universe in a way that we can measure.

READ MORE:How NASA captured supermassive black hole dance of death tornado'

Before, there was an understanding that this was likely the case, thanks to Einstein, but we know for certain now.

In essence, what is needed for a warp drive is a way to expand and contract spacetime at will, and in a local manner, such as around a small object or ship.

I believe there is a chance that once the effect can be duplicated on a lab scale, it will lead to a much deeper understanding of how gravity works, and may open the door to some as-yet-undiscovered theories or loopholes.

I suppose to summarise, the biggest hurdle is the energy, and with that comes technological hurdles, needing bigger EM fields, more sensitive equipment, etc.

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An EM field is an electromagnetic field produced by electrically charged objects. An EM Drive works by bouncing microwaves around inside a closed engine. The microwaves subsequently push against the side of the container, acting as a propellor.

Even if travelling at light speed can be achieved for reference the fastest man-made machine is NASAs Solar Probe Plus which, when it orbits the Sun, will achieve a speed of 690,000 km/h (430,000 mph), or 0.064 percent the speed of light getting across the Universe would still be problematic.

It may make travelling across the solar system a doddle, but to reach the nearest star system, Proxima Centauri which is 4.2 light-years away, it would take, well, 4.2 years.

To exit the Milky Way and reach the next nearest galaxy, the Canis Major Dwarf Galaxy, it would take a whopping 25,000 years.

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Space travel across the universe could be faster than speed of light with Warp Drive - Express.co.uk

Space-Travel Odyssey ‘Ad Astra’ Reflects on the Human Condition – Loyola Phoenix

By Lucas NaberUpdated September 25, 2019 1:12 a.m. CTPublished September 25, 2019 10:10 a.m. CT

Writer and director James Grays Ad Astra is equal parts character study and sci-fi epic, exploring both the physical and emotional isolation of its astronaut protagonist.

Set in a bleak take on the near-future, the film stars Brad Pitt (Fight Club, The Big Short) as astronaut Roy McBride, son of legendary U.S. Space Command astronaut and leader of the fictional Lima Project H. Clifford McBride (Tommy Lee Jones).

Its been 26 years since the Lima Project was formed to scour the solar system for signs of intelligent life, and 16 since the projects ship and entire crew went missing somewhere in Neptunes orbit.

Clifford and his crew have long been presumed dead, but Space Command officials reconsider when they link a worldwide series of deadly electric surges back to the Lima Projects experiments. They enlist Roy to try and contact his father, who may be alive and purposely avoiding detection.

Roy agrees to Space Commands terms and finds himself suiting up to leave Earth the way hes done his whole career.

Ad Astra, released Sept. 20, might not actually be a realistic depiction of space travel, but its rule-defined and unflinchingly logical approach is so plausible it might as well be a documentary on the subject.

Roys complicated journey through this detail-oriented world drives the plot, but the film finds its true merit in simplicity.

Roy is numb to the bureaucracy and safeguarding of Space Commands operations. Hes a machine, powering through psychological exams, ignoring repetitive safety videos and sporting a heart rate that has never risen above 80 beats per minute.

Roys character is defined by his ability to robotically excel in the structure around him. His interstellar expertise and introspective narration make the films complex trappings seem commonplace, reducing the need for expository dialogue.

Grays earnest screenplay paints Roy with plenty of emotional depth, but Pitt communicates more with his eyes than any screenplay could. Bearing a hollow fake smile and perfect posture, Pitt carries the weight of loneliness and labor spanning years inside his pupils and along his brow, expressing more with his mannerisms than his words.

Gray understands the talent hes been blessed with in Pitt, and the film reflects this. Other characters linger on the margins, but the film laser-focuses on Pitt. Roys separated wife Eve (Liv Tyler) is his only human tie to Earth, and shes reduced to a hazy memory by the void Roy faces.

As Roy navigates the stars, he reflects on his current position in life and his relationship with his father.

When the Lima Project left Earth, Roy was a teenager. By the time he found out his father wouldnt return, he was a grown man. Now in his 40s, Roy must confront the possibility that his father wasnt taken from him but instead chose not to come back.

After Clifford disappeared, he shifted from a real figure in Roys life to a security blanket. His heroism motivated Roys career path and his tragic presumed death was easier for Roy to cope with than the possibility of abandonment.

For decades, Roy has used these justifications to ignore the painfully obvious. He always wanted more from his father, even before his mission lifted off.

At two hours and four minutes long, Grays film is a masterpiece of pacing. Ad Astra handles the material of a much longer film without rushing and employs a contemplative pace without drawing things out.

The film takes a densely classical approach to its genre with great success, utilizing hard scientific logic to tell a cosmic adventure story spanning years, but this isnt where its main appeal lies.

Ad Astra understands the appeal of futuristic space travel and knowing the unknowable, but lots of films do. Its the films ability to connect its fictional concept to such innate human concerns that makes Ad Astra so special.

Ad Astra, rated PG-13, is playing in theaters nationwide.

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Space-Travel Odyssey 'Ad Astra' Reflects on the Human Condition - Loyola Phoenix

Mealtime Favorite Mac and Cheese May Be the Next to Visit Mars – ENGINEERING.com

Mac and cheese in the new plastic packaging from WSU. (Image courtesy of CAHNRS News.)

Researchers from Washington State University (WSU) have developed a process that could potentially increase the shelflife of a mealtime favorite in space. Current plastic packaging products can keep food safe at room temperature for only up to 12 months. WSU researchers have figured out how to triple the shelflife of ready-to-eat macaroni and cheese, a development that can largely benefit space travel and military use.

To survive the long travel between Earth and Mars, astronauts will need food that wont spoil during the journey and while theyre on the planets surface.

We need a better barrier to keep oxygen away from the food and provide longer shelflife similar to aluminum foil and plastic laminate pouches, said Shaym Sablani, a professor in WSUs Department of Biological Systems Engineering who lead the research.

The study took form when the team began working closely with the U.S. Army in efforts to improve the Armys Meals Ready to Eat (MREs) to have a shelflife of three years. The Army recently put together a taste panel to test mac and cheese stored for the equivalent of three years and concluded that it was just as good as the current version, which can be stored only for nine months.

The researchers worked with packaging companies to develop new films that prevent oxygen and vapor from escaping for a longer period.

The food is sterilized using a process developed by WSUs Juming Tang called the microwave assisted thermal sterilization (MATS) system. Instead of using metal, like tin cans, the food is sterilized in plastic. Since metal cannot be microwaved, it is the least preferred packaging for MREs. Similarly, glass is too fragile as well as too heavy for either military or space use.

Additionally, the researchers discovered that adding a metal oxide coating to the plastic film significantly speeds up the time it takes for oxygen and other gases to escape. Sablani notes that this compromises the foods shelflife. While metal oxide coating technology has existed for almost 10 years, it can actually be detrimental to the preservation processes, creating cracks when subjected to sterilization.

The packaging films the WSU researchers developed along with packaging companies are composed of multiple layers of different plastics. According to Sablani, each micron thin layer serves a different purpose, such as acting as a barrier or a seal, and can be used for mechanical strength or for printing.

We are excited that an over-layer of organic coating on metal oxide helped protect against microscopic cracks, Sablani said. Multiple layers of metal oxide coating have also increased the barrier performance. Our research guided development of newer high barrier packaging.

The team did not actually wait three years to test the results of each new film. The packaged food was instead kept in a 100F incubator, which rapidly speeds up the change in food quality at a consistent rate. According to Sablani, six months in the incubator is equivalent to three years at room temperature, while nine months is equivalent to five years.

WSU graduate student Juhi Patel, an author on the mac and cheese paper, puts packages of purple potatoes into an incubator, which speeds up the food quality changes at a consistent rate. (Image courtesy of CAHNRS News.)

The Army plans to conduct more testing under field conditions. If they like the taste of the packaged food there, then thats the ultimate test of new films, said Sablani.

The team has already expressed plans to put the technology to use in space, specifically for Mars. While its still not possible to field-test the films through a trip to Mars, Sablani intends to reach out to NASA to discuss how his team can test the WSU films for space missions.

NASA knows about our work, but were just now getting to the point where we can talk to them with a proven product, explained Sablani. We hope to work out a way to test these products on the International Space Station in the future to show that the food is safe after long-term storage.

For food, NASA requires storage allocation of up to five years. The WSU team is currently working on meeting this stipulation. The researchers are also exploring other recipes that will be taste tested when the foods reach the five-year mark. With several types of mission plans proposed for a trip to Mars, Sablani adds that five-year food storage will need to include some built-in safety requirements.

A trip from Earth to Mars may involve approximately nine months of travel, plus five hundred days on or orbiting Mars, then another nine months of travel to return to Earth. Having food that can withstand extra storage time is also crucial in case of unexpected delays or the prolonging of a mission.

The study can be found in the Food and Bioprocess Technology journal. The research was supported by the USDA National Institute of Food and Agriculture Research, AFRI Foundational Grant Program.

For more on the latest developments in space travel, check out how China is building a gigawatt power station in spacehere.

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Mealtime Favorite Mac and Cheese May Be the Next to Visit Mars - ENGINEERING.com

UK and Australia space agencies are developing a hypersonic ‘space plane’ – TechSpot

Forward-looking: At the UK Space Conference 2019, the country's space agency announced that it would be closely working with the Australian Space Agency on an agreement called the "world's first Space Bridge" that includes the prospect of hypersonic space travel between Australia and the UK. A possibility, thanks to the Sabre engine currently in development at the Oxfordshire-based Reaction Engines Limited.

By 2030, hypersonic flights could potentially let people travel from the UK to New York in an hour or reach Australia in four hours. That's the ambition set by the UK and Australia's space agencies as they recently signed up on a 'space bridge' agreement to collaborate and advance in the space industry.

The development took place at this year's UK Space Conference held in Wales. "A space bridge agreement will bring significant benefits to both our thriving space industries, facilitating new trade and investment opportunities and the exchange of knowledge and ideas," commented Dr Graham Turnock, CEO of the UK Space Agency. "It was a pleasure to welcome the Australian Space Agency to the UK Space Conference 2019 and to set out our intent to increase collaboration," he added.

Part of this collaboration involves working on a new hypersonic aircraft powered by UK's Reaction Engines Ltd. The Synergetic Air-Breathing Rocket Engine (SABRE) currently undergoing development at the company is said to have the fuel efficiency of a jet engine combined with the power and high-speed ability of a rocket.

"When we have brought the SABRE rocket engine to fruition, that may enable us to get to Australia in perhaps as little as four hours," said Dr Graham, adding that "This is technology that could definitely deliver that. We're talking the 2030s for operational service, and the work is already very advanced."

Reaction Engines also ran successful tests of a precooler in April this year, in which it simulated conditions at Mach 3.3 (more than three times the speed of sound). These simulations were conducted at a testing facility in the Colorado Air and Space Port in the US.

The precooler was tested to ensure that extremely hot temperatures caused by high-speed air-flow through the engine wouldn't damage any components. The company said that the precooler was able to cool gases over 1,000 C to ambient temperature in less than 1/20th of a second. "This is a hugely significant milestone which has seen Reaction Engines' proprietary precooler technology achieve unparalleled heat transfer performance," said Mark Thomas, CEO of Reaction Engines.

The company's program director Shaun Driscoll said that the Sabre engine was like a hybrid of a rocket engine and an aero engine as it allowed a rocket to breathe air. "Rockets really haven't progressed in 70 years, whereas aero engines have become very efficient, so if you can combine an aero engine and a rocket you can have a very lightweight efficient propulsion system and basically create a space plane," he said.

With over 100 million ($130 million) in funding over the past four years, Reaction Engines has garnered interest of many big names in the industry including BAE Systems, Rolls-Royce and Boeing.

A testing facility at Buckinghamshire, UK, is being finalized for construction that will serve as the location for the first ground-based demonstration of a SABRE engine air-breathing core.

Image(s) Credit: Reaction Engines

Originally posted here:

UK and Australia space agencies are developing a hypersonic 'space plane' - TechSpot

Letters: Saudi’s controversial tourism bid; space travel; and why trains aren’t always better than planes – The Times

Write to Travel and win 250 towards a holiday in Greece

Letter of the weekSaudi is a great destination for a special-interest holiday. I would start in Jeddah, with a visit to the old towns historic merchant houses and fabulous gold and spice souks, then stroll along the Corniche to see the sunset. North of Medina, you can see the remains of the Hejaz railway, the tracks, stations and rusting rolling stock lying abandoned in the desert, like a scene from Lawrence of Arabia. Continuing north through Al Ula, you come to Madain Saleh, the second largest Nabatean settlement after Petra. This necropolis has more than 131 tombs with intricate inscriptions and carvings of eagles and sphinxes. This is just a small part of the Nabatean kingdom there is much more to discover.Susan Hannis, Dorset

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Letters: Saudi's controversial tourism bid; space travel; and why trains aren't always better than planes - The Times

Space: Nasa ‘Shapeshifter’ robot could be on its way to Saturn! – CBBC Newsround

NASA

The mini robots can come together to form one big robot

Nasa are designing a shapeshifting robot that'll travel to Saturn.

They're hoping to send the new robot to one of Saturn's biggest moons, called Titan.

The robot is called Shapeshifter, and it's formed of lots of mini robots that can roll, fly, float and swim, then morph into a single machine.

This is what the robot looks like at the moment

Nasa hope they'll find out more about Titan. It's the only object in the Solar System other than Earth that has liquid on the surface.

The robot explorer is still in the first stages of production but apparently the early tests are looking promising! The prototype can roll around on the ground and split itself in half.

This is an artist's impression of how the robot might operate

One of the researches at Nasa said: "We have very limited information about the composition of the surface [of Titan]"

So the experts felt they needed to design a machine that was capable of exploring all the different parts of it and could deal with anything!

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Space: Nasa 'Shapeshifter' robot could be on its way to Saturn! - CBBC Newsround

Commercial Space Travel: How Leaving Earth Will Make You …

Maybe it will take going to outer space for renewable energy naysayers to realise the devastating impact the human race has on planet Earth.

Just this week, the United Kingdom parliament became the first in the world to pass a motion declaring an environment and climate emergency, amid mounting pressure for the region to adopt a net zero emission target before 2050.

The news follows a recent United Nations report that found seven major countries, including the United States, were well behind achieving the carbon neutral pledges they made in Paris three years ago.

The UN noted that countries were not doing enough to curb their emissions.

But perhaps commercial space travel is what we need to push people to tackle climate change more seriously?

NASA astronaut Terry Virts has spoken publicly about the perspective-altering effects of viewing Earth from above, in particular the increased awareness it brings of humankinds environmental mistakes.

Virts has spent 200 days in space at the International Space Station (ISS) and has taken more photos of Earth from space than any other astronaut.

People ask astronauts 'what's your favourite planet?' and it's not Mars or Jupiter, it's Earth, Virts said upon returning from space.

We have everything we need to survive right here. In saying that, when I tried to film Beijing I never could because all you could see was smog. And in the Amazon you can see deforestation. So there's some man-made environmental messes you can see from space. But 99 percent of the planet really does look beautiful, it's not all doom and gloom.

While 99 percent of the planet may look beautiful right now, how long will it take for emissions from fossil fuels to produce enough smog to obscure the majority of Earth from view?

And by the time commercial space travel becomes available for the likes of you and I, will we be able to capture that perfect holiday snap of Earth that Virts fondly speaks of?

Commercial Space Travel: Coming to An Airport Near You

There are few people who can say theyve been to outer space. And even fewer that can claim to have been among the first in the world to fly on a commercial spacecraft.

But in February this year Beth Moses, chief astronaut instructor at Virgin Galactic, became a household name for doing just that. Years of hard work, dedication and self belief finally paid off and Moses became the first woman to travel to space on a commercial spacecraft.

It was the first time that Moses, an aerospace engineer who had previously worked at NASA, had visited space. The purpose of Moses flight was to ensure she could fully prepare Virgin Galactics future customers, of which there are hundreds in queue, for the journey to view earth from above.

Having Beth fly in the cabin today, starting to ensure that our customer journey is as flawless as the spaceship itself, brings a huge sense of anticipation and excitement to all of us here who are looking forward to experiencing space for ourselves, Virgin Galactic founder Sir Richard Branson said at the time.

Beth Moses celebrating after the flight with the two pilots, Dave Mackay (L) and Mike Sooch Masucci (C), as well as Virgin Galactic CEO George Whitesides (R)

Mosess mission for the flight was clear; experience the flight fully to ensure there were no surprises following the three-day briefing each customer receives pre-flight, so these everyday people could focus on the life-altering view around them.

Taking Risks To Shape Perspective

Moses admits the criticism the Virgin Galactic team received for daring to dream big was unexpected.

Its an experience Moses and I share, with Power Ledger facing its own critics for daring to reimagine the financial models surrounding green energy and accelerate the takeup of renewables.

I blindly assumed the new space community would be as respected as NASA. But within my professional community people laugh about human commercial space travel, Moses told me.

Its true doubters have not been shy about sharing their views publicly.

Australian astronaut Andy Thomas called Sir Richard Bransons quest to take passengers into orbit a dead-end and dangerous technology.

And following a fatal crash in 2014, rocket propulsion expert Carolynne Campbell-Knight was quoted stating Virgin Galactic should go away and do something they might be good at like selling mobile phones. They should stay out of the space business.

Despite the mounting pressure to give up, Moses and the team at Virgin Galactic pushed on, paying close attention to their mistakes and turning them into lessons.

And slowly, some space experts started to change their tune.

In December 2018, NASA selected its own technology experiments to fly on Virgin Galactics SpaceShipTwo commercial research flight. At the time, Christopher Baker of NASAs Armstrong Flight Research Center said that regular commercial access to space will change how NASA approaches technology development, by allowing them to invest in early research validation.

This year, in its fifth supersonic-powered test flight, Virgin Galactic reached space for the second time in 10 weeks. Spaceship VSS Unity, the spacecraft Moses was on, also flew higher and faster than ever before.

Moses herself could feel the tides changing when some of the NASA colleagues, who had laughed off her decision to join the human space startup, began asking to work with Virgin Galactic.

All of a sudden they were saying wow, they did it. Now they want to come work here and they want a job, Moses says.

I like our model as it can bring it (space travel) to more people.

Author and National Geographic Society chairman, Jean Case describes the bold risk-taking behind some of the greatest discoveries and innovations humanity has made in her book Be Fearless. Case specifically calls out space travel as being able to alter culture, geography and political systems.

Big bets are the engine for countless other innovations. They can change a culture, a geography, a mindset and a political system, Case writes in chapter six.

Moses agrees; Space travel can redefine geography and political systems, it encourages a mindset that isnt regional and there is a human and emotional magic to that, she says.

We have to graduate to a sense of planetary unity that we dont have as humans.

Using A Planetary View to Fix Our Problems

Yale has already recognised the power of an outer space perspective to address Earths pressing climate issues.

Yale OpenLabs energy academy, which believes that achieving sustainability requires a collective planetary consciousness, has created an open and globally collaborative space dedicated to promoting planetary sustainability.

The program is currently in proof-of-concept phase, but promises to build an unconventional classroom and teach visually stunning journeys where natural resources are studied from the big perspective.

Our climate and energy challenge requires a population that understands the close and delicate connections between macro and micro scales; from the solar system down to cellular and molecular structures, the project explains.

Yales vision? To empower individuals and communities to re-envision the global energy system, to generate planetary consciousness and foster higher awareness in our delicate relationship to Earth.

A Vision Thats Out of This World

Moses is hopeful that the Virgin Galactic team can replicate their successes and operate from any airport, and admits she is an eternal and self-proclaimed biased optimist.

Were asking questions that have never been asked, Moses says.

I think it is time we all asked ourselves questions that have never been asked.

As that old adage goes; its better to have an impossible dream than no dream at all - if not for commercial aspirations, then at least for the sake of planet Earth.

Maybe it will take going to outer space for renewable energy naysayers to realise the devastating impacts of climate change.

But hopefully it wont take a ticket to the moon to appreciate Earth more and realise the importance of preserving its future.

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Commercial Space Travel: How Leaving Earth Will Make You ...

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. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. 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 spacecraft both when unpropelled and when under propulsion is 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. Before launch, the rocket can weigh more than 900 tonnes. The Columbia, STS-1 weighed 2000 tonnes at take off.

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 remainder heats up 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.

Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed 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.

Uncrewed space missions use remote-controlled spacecraft. The first uncrewed 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 uncrewed 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.

See the article here:

Spaceflight - Wikipedia

Human spaceflight – Wikipedia

Human spaceflight (also referred to as crewed spaceflight or manned spaceflight) is space travel with a crew or passengers aboard the spacecraft. Spacecraft carrying people may be operated directly, by human crew, or it may be either remotely operated from ground stations on Earth or be autonomous, able to carry out a specific mission with no human involvement.

The first human spaceflight was launched by the Soviet Union on 12 April 1961 as a part of the Vostok program, with cosmonaut Yuri Gagarin aboard. Humans have been continuously present in space for 18years and 168days on the International Space Station. All early human spaceflight was crewed, where at least some of the passengers acted to carry out tasks of piloting or operating the spacecraft. After 2015, several human-capable spacecraft are being explicitly designed with the ability to operate autonomously.

Russia and China have human spaceflight capability with the Soyuz program and Shenzhou program. In the United States, SpaceShipTwo reached the edge of space in 2018; this was the first crewed spaceflight from the USA since the Space Shuttle retired in 2011. Currently, all expeditions to the International Space Station use Soyuz vehicles, which remain attached to the station to allow quick return if needed. The United States is developing commercial crew transportation to facilitate domestic access to ISS and low Earth orbit, as well as the Orion vehicle for beyond-low Earth orbit applications.

While spaceflight has typically been a government-directed activity, commercial spaceflight has gradually been taking on a greater role. The first private human spaceflight took place on 21 June 2004, when SpaceShipOne conducted a suborbital flight, and a number of non-governmental companies have been working to develop a space tourism industry. NASA has also played a role to stimulate private spaceflight through programs such as Commercial Orbital Transportation Services (COTS) and Commercial Crew Development (CCDev). With its 2011 budget proposals released in 2010,[1] the Obama administration moved towards a model where commercial companies would supply NASA with transportation services of both people and cargo transport to low Earth orbit. The vehicles used for these services could then serve both NASA and potential commercial customers. Commercial resupply of ISS began two years after the retirement of the Shuttle, and commercial crew launches could begin by 2019.[2]

Human spaceflight capability was first developed during the Cold War between the United States and the Soviet Union (USSR), which developed the first intercontinental ballistic missile rockets to deliver nuclear weapons. These rockets were large enough to be adapted to carry the first artificial satellites into low Earth orbit. After the first satellites were launched in 1957 and 1958, the US worked on Project Mercury to launch men singly into orbit, while the USSR secretly pursued the Vostok program to accomplish the same thing. The USSR launched the first human in space, Yuri Gagarin, into a single orbit in Vostok 1 on a Vostok 3KA rocket, on 12 April 1961. The US launched its first astronaut, Alan Shepard, on a suborbital flight aboard Freedom 7 on a Mercury-Redstone rocket, on 5 May 1961. Unlike Gagarin, Shepard manually controlled his spacecraft's attitude, and landed inside it. The first American in orbit was John Glenn aboard Friendship 7, launched 20 February 1962 on a Mercury-Atlas rocket. The USSR launched five more cosmonauts in Vostok capsules, including the first woman in space, Valentina Tereshkova aboard Vostok 6 on 16 June 1963. The US launched a total of two astronauts in suborbital flight and four into orbit through 1963.

US President John F. Kennedy raised the stakes of the Space Race by setting the goal of landing a man on the Moon and returning him safely by the end of the 1960s.[3] The US started the three-man Apollo program in 1961 to accomplish this, launched by the Saturn family of launch vehicles, and the interim two-man Project Gemini in 1962, which flew 10 missions launched by Titan II rockets in 1965 and 1966. Gemini's objective was to support Apollo by developing American orbital spaceflight experience and techniques to be used in the Moon mission.[4]

Meanwhile, the USSR remained silent about their intentions to send humans to the Moon, and proceeded to stretch the limits of their single-pilot Vostok capsule into a two- or three-person Voskhod capsule to compete with Gemini. They were able to launch two orbital flights in 1964 and 1965 and achieved the first spacewalk, made by Alexei Leonov on Voskhod 2 on 8 March 1965. But Voskhod did not have Gemini's capability to maneuver in orbit, and the program was terminated. The US Gemini flights did not accomplish the first spacewalk, but overcame the early Soviet lead by performing several spacewalks and solving the problem of astronaut fatigue caused by overcoming the lack of gravity, demonstrating up to two weeks endurance in a human spaceflight, and the first space rendezvous and dockings of spacecraft.

The US succeeded in developing the Saturn V rocket necessary to send the Apollo spacecraft to the Moon, and sent Frank Borman, James Lovell, and William Anders into 10 orbits around the Moon in Apollo 8 in December 1968. In July 1969, Apollo 11 accomplished Kennedy's goal by landing Neil Armstrong and Buzz Aldrin on the Moon 21 July and returning them safely on 24 July along with Command Module pilot Michael Collins. A total of six Apollo missions landed 12 men to walk on the Moon through 1972, half of which drove electric powered vehicles on the surface. The crew of Apollo 13, Lovell, Jack Swigert, and Fred Haise, survived a catastrophic in-flight spacecraft failure and returned to Earth safely without landing on the Moon.

Meanwhile, the USSR secretly pursued human lunar orbiting and landing programs. They successfully developed the three-person Soyuz spacecraft for use in the lunar programs, but failed to develop the N1 rocket necessary for a human landing, and discontinued the lunar programs in 1974.[5] On losing the Moon race, they concentrated on the development of space stations, using the Soyuz as a ferry to take cosmonauts to and from the stations. They started with a series of Salyut sortie stations from 1971 to 1986.

After the Apollo program, the US launched the Skylab sortie space station in 1973, manning it for 171 days with three crews aboard Apollo spacecraft. President Richard Nixon and Soviet Premier Leonid Brezhnev negotiated an easing of relations known as dtente, an easing of Cold War tensions. As part of this, they negotiated the Apollo-Soyuz Test Project, in which an Apollo spacecraft carrying a special docking adapter module rendezvoused and docked with Soyuz 19 in 1975. The American and Russian crews shook hands in space, but the purpose of the flight was purely diplomatic and symbolic.

Nixon appointed his Vice President Spiro Agnew to head a Space Task Group in 1969 to recommend follow-on human spaceflight programs after Apollo. The group proposed an ambitious Space Transportation System based on a reusable Space Shuttle which consisted of a winged, internally fueled orbiter stage burning liquid hydrogen, launched by a similar, but larger kerosene-fueled booster stage, each equipped with airbreathing jet engines for powered return to a runway at the Kennedy Space Center launch site. Other components of the system included a permanent modular space station, reusable space tug and nuclear interplanetary ferry, leading to a human expedition to Mars as early as 1986, or as late as 2000, depending on the level of funding allocated. However, Nixon knew the American political climate would not support Congressional funding for such an ambition, and killed proposals for all but the Shuttle, possibly to be followed by the space station. Plans for the Shuttle were scaled back to reduce development risk, cost, and time, replacing the piloted flyback booster with two reusable solid rocket boosters, and the smaller orbiter would use an expendable external propellant tank to feed its hydrogen-fueled main engines. The orbiter would have to make unpowered landings.

The two nations continued to compete rather than cooperate in space, as the US turned to developing the Space Shuttle and planning the space station, dubbed Freedom. The USSR launched three Almaz military sortie stations from 1973 to 1977, disguised as Salyuts. They followed Salyut with the development of Mir, the first modular, semi-permanent space station, the construction of which took place from 1986 to 1996. Mir orbited at an altitude of 354 kilometers (191 nautical miles), at a 51.6 inclination. It was occupied for 4,592 days, and made a controlled reentry in 2001.

The Space Shuttle started flying in 1981, but the US Congress failed to approve sufficient funds to make Freedom a reality. A fleet of four shuttles was built: Columbia, Challenger, Discovery, and Atlantis. A fifth shuttle, Endeavour, was built to replace Challenger, which was destroyed in an accident during launch that killed 7 astronauts on 28 January 1986. Twenty-two Shuttle flights carried a European Space Agency sortie space station called Spacelab in the payload bay from 1983 to 1998.[6]

The USSR copied the reusable Space Shuttle orbiter, which it called Buran. It was designed to be launched into orbit by the expendable Energia rocket, and capable of robotic orbital flight and landing. Unlike the US Shuttle, Buran had no main rocket engines, but like the Shuttle used its orbital maneuvering engines to perform its final orbital insertion. A single unmanned orbital test flight was successfully made in November 1988. A second test flight was planned by 1993, but the program was cancelled due to lack of funding and the dissolution of the Soviet Union in 1991. Two more orbiters were never completed, and the first one was destroyed in a hangar roof collapse in May 2002.

The dissolution of the Soviet Union in 1991 brought an end to the Cold War and opened the door to true cooperation between the US and Russia. The Soviet Soyuz and Mir programs were taken over by the Russian Federal Space Agency, now known as the Roscosmos State Corporation. The Shuttle-Mir Program included American Space Shuttles visiting the Mir space station, Russian cosmonauts flying on the Shuttle, and an American astronaut flying aboard a Soyuz spacecraft for long-duration expeditions aboard Mir.

In 1993, President Bill Clinton secured Russia's cooperation in converting the planned Space Station Freedom into the International Space Station (ISS). Construction of the station began in 1998. The station orbits at an altitude of 409 kilometers (221nmi) and an inclination of 51.65.

The Space Shuttle was retired in 2011 after 135 orbital flights, several of which helped assemble, supply, and crew the ISS. Columbia was destroyed in another accident during reentry, which killed 7 astronauts on 1 February 2003.

After Russia's launch of Sputnik 1 in 1957, Chairman Mao Zedong intended to place a Chinese satellite in orbit by 1959 to celebrate the 10th anniversary of the founding of the People's Republic of China (PRC),[7] However, China did not successfully launch its first satellite until 24 April 1970. Mao and Premier Zhou Enlai decided on 14 July 1967, that the PRC should not be left behind, and started China's own human spaceflight program.[8] The first attempt, the Shuguang spacecraft copied from the US Gemini, was cancelled on 13 May 1972.

China later designed the Shenzhou spacecraft resembling the Russian Soyuz, and became the third nation to achieve independent human spaceflight capability by launching Yang Liwei on a 21-hour flight aboard Shenzhou 5 on 15 October 2003. China launched the Tiangong-1 space station on 29 September 2011, and two sortie missions to it: Shenzhou 9 1629 June 2012, with China's first female astronaut Liu Yang; and Shenzhou 10, 1326 June 2013. The station was retired on 21 March 2016 and remains in a 363-kilometer (196-nautical-mile), 42.77 inclination orbit.

The European Space Agency began development in 1987 of the Hermes spaceplane, to be launched on the Ariane 5 expendable launch vehicle. The project was cancelled in 1992, when it became clear that neither cost nor performance goals could be achieved. No Hermes shuttles were ever built.

Japan began development in the 1980s of the HOPE-X experimental spaceplane, to be launched on its H-IIA expendable launch vehicle. A string of failures in 1998 led to funding reduction, and the project's cancellation in 2003.

Under the Bush administration, the Constellation Program included plans for retiring the Shuttle program and replacing it with the capability for spaceflight beyond low Earth orbit. In the 2011 United States federal budget, the Obama administration cancelled Constellation for being over budget and behind schedule while not innovating and investing in critical new technologies.[9] For beyond low Earth orbit human spaceflight NASA is developing the Orion spacecraft to be launched by the Space Launch System. Under the Commercial Crew Development plan, NASA will rely on transportation services provided by the private sector to reach low Earth orbit, such as SpaceX's Falcon 9/Dragon V2, Sierra Nevada Corporation's Dream Chaser, or Boeing's CST-100. The period between the retirement of the shuttle in 2011 and the first launch to space of Spaceshiptwo on December 13, 2018 is similar to the gap between the end of Apollo in 1975 and the first Space Shuttle flight in 1981, is referred to by a presidential Blue Ribbon Committee as the U.S. human spaceflight gap.[10]

Since the early 2000s, a variety of private spaceflight ventures have been undertaken. Several of the companies, including Blue Origin, SpaceX, Virgin Galactic, and Sierra Nevada have explicit plans to advance human spaceflight. As of 2016[update], all four of those companies have development programs underway to fly commercial passengers.

A commercial suborbital spacecraft aimed at the space tourism market is being developed by Virgin Galactic called SpaceshipTwo which reached space in December 2018.[11][12]Blue Origin has begun a multi-year test program of their New Shepard vehicle and carried out six successful uncrewed test flights in 20152016. Blue Origin plan to fly "test passengers" in Q2 2017, and initiate commercial flights in 2018.[13][14]

SpaceX and Boeing are both developing passenger-capable orbital space capsules as of 2015, planning to fly NASA astronauts to the International Space Station by 2019. SpaceX will be carrying passengers on Dragon 2 launched on a Falcon 9 launch vehicle. Boeing will be doing it with their CST-100 launched on a United Launch Alliance Atlas V launch vehicle.[15]Development funding for these orbital-capable technologies has been provided by a mix of government and private funds, with SpaceX providing a greater portion of total development funding for this human-carrying capability from private investment.[16][17]There have been no public announcements of commercial offerings for orbital flights from either company, although both companies are planning some flights with their own private, not NASA, astronauts on board.

12 April 1961

Yuri Gagarin became the first Russian as well as the first human to reach space on Vostok 1 on April 12, 1961.

Sally Ride became the first American woman in space in 1983. Eileen Collins was the first female Shuttle pilot, and with Shuttle mission STS-93 in 1999 she became the first woman to command a U.S. spacecraft.

For many years, only the USSR (later Russia) and the United States had their own astronauts. Citizens of other nations flew in space, beginning with the flight of Vladimir Remek, a Czech, on a Soviet spacecraft on 2 March 1978, in the Interkosmos programme. As of 2010[update], citizens from 38 nations (including space tourists) have flown in space aboard Soviet, American, Russian, and Chinese spacecraft.

Human spaceflight programs have been conducted by the former Soviet Union and current Russian Federation, the United States, the People's Republic of China and by private spaceflight company Scaled Composites.

Currently have human spaceflight programs.

Confirmed and dated plans for human spaceflight programs.

Plans for human spaceflight on the simplest form (suborbital spaceflight, etc.).

Plans for human spaceflight on the extreme form (space stations, etc.).

Once had official plans for human spaceflight programs, but have since been abandoned.

Space vehicles are spacecraft used for transportation between the Earth's surface and outer space, or between locations in outer space. The following space vehicles and spaceports are currently used for launching human spaceflights:

The following space stations are currently maintained in Earth orbit for human occupation:

Numerous private companies attempted human spaceflight programs in an effort to win the $10 million Ansari X Prize. The first private human spaceflight took place on 21 June 2004, when SpaceShipOne conducted a suborbital flight. SpaceShipOne captured the prize on 4 October 2004, when it accomplished two consecutive flights within one week. SpaceShipTwo, launching from the carrier aircraft White Knight Two, is planned to conduct regular suborbital space tourism.[18]

Most of the time, the only humans in space are those aboard the ISS, whose crew of six spends up to six months at a time in low Earth orbit.

NASA and ESA use the term "human spaceflight" to refer to their programs of launching people into space. These endeavors have also been referred to as "manned space missions," though because of gender specificity this is no longer official parlance according to NASA style guides.[19]

On 15th August, 2018 Prime Minister of India Narendra Modi, from rampant of the Red Fort Formally announced Indian Human Spaceflight Programme. Through this Programme, India is planning to send humans into the space on its orbital vehicle Gaganyaan by the end of 2021. The Indian Space Research Organisation (ISRO) began work on this project in 2006.[20] The objective is to carry a crew of three to low Earth orbit (LEO) and return them safely for a water-landing at a predefined landing zone. The program is proposed to be implemented in defined phases. Currently, the activities are progressing with a focus on the development of critical technologies for subsystems such as the Crew Module (CM), Environmental Control and Life Support System (ECLSS), Crew Escape System, etc. The department has initiated activities to study technical and managerial issues related to crewed missions. The program envisages the development of a fully autonomous orbital vehicle carrying 2 or 3 crew members to about 300km low Earth orbit and their safe return.

NASA is developing a plan to land humans on Mars by the 2030s. The first step in this mission begins sometime during 2020, when NASA plans to send an uncrewed craft into deep space to retrieve an asteroid.[21] The asteroid will be pushed into the moons orbit, and studied by astronauts aboard Orion, NASAs first human spacecraft in a generation.[22] Orions crew will return to Earth with samples of the asteroid and their collected data. In addition to broadening Americas space capabilities, this mission will test newly developed technology, such as solar electric propulsion, which uses solar arrays for energy and requires ten times less propellant than the conventional chemical counterpart used for powering space shuttles to orbit.[23]

Several other countries and space agencies have announced and begun human spaceflight programs by their own technology, Japan (JAXA), Iran (ISA) and Malaysia (MNSA).

A number of spacecraft have been proposed over the decades that might facilitate spaceliner passenger travel. Somewhat analogous to travel by airliner after the middle of the 20th century, these vehicles are proposed to transport a large number of passengers to destinations in space, or to destinations on Earth which travel through space. To date, none of these concepts have been built, although a few vehicles that carry fewer than 10 persons are currently in the flight testing phase of their development process.

One large spaceliner concept currently in early development is the SpaceX BFR which, in addition to replacing the Falcon 9 and Falcon Heavy launch vehicles in the legacy Earth-orbit market after 2020, has been proposed by SpaceX for long-distance commercial travel on Earth. This is to transport people on point-to-point suborbital flights between two points on Earth in under one hour, also known as "Earth-to-Earth," and carrying 100+ passengers.[24][25][26]

Small spaceplane or small capsule suborbital spacecraft have been under development for the past decade or so and, as of 2017[update], at least one of each type are under development. Both Virgin Galactic and Blue Origin are in active development, with the SpaceShipTwo spaceplane and the New Shepard capsule, respectively. Both would carry approximately a half-dozen passengers up to space for a brief time of zero gravity before returning to the same location from where the trip began. XCOR Aerospace had been developing the Lynx single-passenger spaceplane since the 2000s[27][28][29] but development was halted in 2017.[30]

There are two main sources of hazard in space flight: those due to the environment of space which make it hostile to the human body, and the potential for mechanical malfunctions of the equipment required to accomplish space flight.

Planners of human spaceflight missions face a number of safety concerns.

The immediate needs for breathable air and drinkable water are addressed by the life support system of the spacecraft.

Medical consequences such as possible blindness and bone loss have been associated with human space flight.[38][39]

On 31 December 2012, a NASA-supported study reported that spaceflight may harm the brain of astronauts and accelerate the onset of Alzheimer's disease.[40][41][42]

In October 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, including a human mission to Mars.[43][44]

On 2 November 2017, scientists reported that significant changes in the position and structure of the brain have been found in astronauts who have taken trips in space, based on MRI studies. Astronauts who took longer space trips were associated with greater brain changes.[45][46]

Researchers in 2018 reported, after detecting the presence on the International Space Station (ISS) of five Enterobacter bugandensis bacterial strains, none pathogenic to humans, that microorganisms on ISS should be carefully monitored to continue assuring a medically healthy environment for astronauts.[47][48]

In March 2019, NASA reported that latent viruses in humans may be activated during space missions, adding possibly more risk to astronauts in future deep-space missions.[49]

Medical data from astronauts in low Earth orbits for long periods, dating back to the 1970s, show several adverse effects of a microgravity environment: loss of bone density, decreased muscle strength and endurance, postural instability, and reductions in aerobic capacity. Over time these deconditioning effects can impair astronauts performance or increase their risk of injury.[50]

In a weightless environment, astronauts put almost no weight on the back muscles or leg muscles used for standing up, which causes them to weaken and get smaller. Astronauts can lose up to twenty per cent of their muscle mass on spaceflights lasting five to eleven days. The consequent loss of strength could be a serious problem in case of a landing emergency.[51] Upon return to Earth from long-duration flights, astronauts are considerably weakened, and are not allowed to drive a car for twenty-one days.[52]

Astronauts experiencing weightlessness will often lose their orientation, get motion sickness, and lose their sense of direction as their bodies try to get used to a weightless environment. When they get back to Earth, or any other mass with gravity, they have to readjust to the gravity and may have problems standing up, focusing their gaze, walking and turning. Importantly, those body motor disturbances after changing from different gravities only get worse the longer the exposure to little gravity.[53] These changes will affect operational activities including approach and landing, docking, remote manipulation, and emergencies that may happen while landing. This can be a major roadblock to mission success.[citation needed]

In addition, after long space flight missions, male astronauts may experience severe eyesight problems.[54][55][56][57][58] Such eyesight problems may be a major concern for future deep space flight missions, including a crewed mission to the planet Mars.[54][55][56][57][59]

Without proper shielding, the crews of missions beyond low Earth orbit (LEO) might be at risk from high-energy protons emitted by solar flares and associated solar particle events (SPEs). Lawrence Townsend of the University of Tennessee and others have studied the overall most powerful solar storm ever recorded. The flare was seen by the British astronomer Richard Carrington in September 1859. Radiation doses astronauts would receive from a Carrington-type storm could cause acute radiation sickness and possibly even death.[61] Another storm that could have incurred a lethal radiation dose if astronauts were outside the Earth's protective magnetosphere occurred during the Space Age, in fact, shortly after Apollo 16 landed and before Apollo 17 launched.[62] This solar storm of August 1972 would likely at least have caused acute illness.[63]

Another type of radiation, galactic cosmic rays, presents further challenges to human spaceflight beyond low Earth orbit.[64]

There is also some scientific concern that extended spaceflight might slow down the bodys ability to protect itself against diseases.[65] Some of the problems are a weakened immune system and the activation of dormant viruses in the body. Radiation can cause both short and long term consequences to the bone marrow stem cells which create the blood and immune systems. Because the interior of a spacecraft is so small, a weakened immune system and more active viruses in the body can lead to a fast spread of infection.[citation needed]

During long missions, astronauts are isolated and confined into small spaces. Depression, cabin fever and other psychological problems may impact the crew's safety and mission success.[66]

Astronauts may not be able to quickly return to Earth or receive medical supplies, equipment or personnel if a medical emergency occurs. The astronauts may have to rely for long periods on their limited existing resources and medical advice from the ground.

During astronauts' stay in space, they may experience mental disorders (such as post-trauma, depression, anxiety, etc.), more than for an average person.NASA spends millions of dollars on psychological treatments for astronauts and former astronauts.[67] To date, there is no way to prevent or reduce mental problems caused by extended periods of stay in space.

Due to these mental disorders, the efficiency of their work is impaired and sometimes they are forced to send the astronauts back to Earth, which is very expensive. [68] A Russian expedition to space in 1976 was returned to Earth after the cosmonauts reported a strong odor that caused a fear of fluid leakage, but after a thorough investigation it became clear that there was no leakage or technical malfunction. It was concluded by NASA that the cosmonauts most likely had hallucinations of the smell, which brought many unnecessary wasted expenses.

It is possible that the mental health of astronauts can be affected by the changes in the sensory systems while in prolonged space travel.

During astronauts' spaceflight, they are in a very extreme state where there is no gravity. This given state and the fact that no change is taking place in the environment will result in the weakening of sensory input to the astronauts in all seven senses.

Space flight requires much higher velocities than ground or air transportation, which in turn requires the use of high energy density propellants for launch, and the dissipation of large amounts of energy, usually as heat, for safe reentry through the Earth's atmosphere.

Since rockets carry the potential for fire or explosive destruction, space capsules generally employ some sort of launch escape system, consisting either of a tower-mounted solid fuel rocket to quickly carry the capsule away from the launch vehicle (employed on Mercury, Apollo, and Soyuz), or else ejection seats (employed on Vostok and Gemini) to carry astronauts out of the capsule and away for individual parachute landing. The escape tower is discarded at some point before the launch is complete, at a point where an abort can be performed using the spacecraft's engines.

Such a system is not always practical for multiple crew member vehicles (particularly spaceplanes), depending on location of egress hatch(es). When the single-hatch Vostok capsule was modified to become the 2 or 3-person Voskhod, the single-cosmonaut ejection seat could not be used, and no escape tower system was added. The two Voskhod flights in 1964 and 1965 avoided launch mishaps. The Space Shuttle carried ejection seats and escape hatches for its pilot and copilot in early flights, but these could not be used for passengers who sat below the flight deck on later flights, and so were discontinued.

There have only been two in-flight launch aborts of a crewed flight. The first occurred on Soyuz 18a on 5 April 1975. The abort occurred after the launch escape system had been jettisoned, when the launch vehicle's spent second stage failed to separate before the third stage ignited. The vehicle strayed off course, and the crew separated the spacecraft and fired its engines to pull it away from the errant rocket. Both cosmonauts landed safely. The second occurred on 11 October 2018 with the launch of Soyuz MS-10. Again, both crew members survived.

In the only use of a launch escape system on a crewed flight, the planned Soyuz T-10a launch on 26 September 1983 was aborted by a launch vehicle fire 90 seconds before liftoff. Both cosmonauts aboard landed safely.

The only crew fatality during launch occurred on 28 January 1986, when the Space Shuttle Challenger broke apart 73 seconds after liftoff, due to failure of a solid rocket booster seal which caused separation of the booster and failure of the external fuel tank, resulting in explosion of the fuel. All seven crew members were killed.

The single pilot of Soyuz 1, Vladimir Komarov was killed when his capsule's parachutes failed during an emergency landing on 24 April 1967, causing the capsule to crash.

The crew of seven aboard the Space Shuttle Columbia were killed on reentry after completing a successful mission in space on 1 February 2003. A wing leading edge reinforced carbon-carbon heat shield had been damaged by a piece of frozen external tank foam insulation which broke off and struck the wing during launch. Hot reentry gasses entered and destroyed the wing structure, leading to breakup of the orbiter vehicle.

There are two basic choices for an artificial atmosphere: either an Earth-like mixture of oxygen in an inert gas such as nitrogen or helium, or pure oxygen, which can be used at lower than standard atmospheric pressure. A nitrogen-oxygen mixture is used in the International Space Station and Soyuz spacecraft, while low-pressure pure oxygen is commonly used in space suits for extravehicular activity.

Use of a gas mixture carries risk of decompression sickness (commonly known as "the bends") when transitioning to or from the pure oxygen space suit environment. There have also been instances of injury and fatalities caused by suffocation in the presence of too much nitrogen and not enough oxygen.

A pure oxygen atmosphere carries risk of fire. The original design of the Apollo spacecraft used pure oxygen at greater than atmospheric pressure prior to launch. An electrical fire started in the cabin of Apollo 1 during a ground test at Cape Kennedy Air Force Station Launch Complex 34 on 27 January 1967, and spread rapidly. The high pressure (increased even higher by the fire) prevented removal of the plug door hatch cover in time to rescue the crew. All three, Gus Grissom, Ed White, and Roger Chaffee, were killed.[72] This led NASA to use a nitrogen/oxygen atmosphere before launch, and low pressure pure oxygen only in space.

The March 1966 Gemini 8 mission was aborted in orbit when an attitude control system thruster stuck in the on position, sending the craft into a dangerous spin which threatened the lives of Neil Armstrong and David Scott. Armstrong had to shut the control system off and use the reentry control system to stop the spin. The craft made an emergency reentry and the astronauts landed safely. The most probable cause was determined to be an electrical short due to a static electricity discharge, which caused the thruster to remain powered even when switched off. The control system was modified to put each thruster on its own isolated circuit.

The third lunar landing expedition Apollo 13 in April 1970, was aborted and the lives of the crew, James Lovell, Jack Swigert and Fred Haise, were threatened by failure of a cryogenic liquid oxygen tank en route to the Moon. The tank burst when electrical power was applied to internal stirring fans in the tank, causing the immediate loss of all of its contents, and also damaging the second tank, causing the loss of its remaining oxygen in a span of 130 minutes. This in turn caused loss of electrical power provided by fuel cells to the command spacecraft. The crew managed to return to Earth safely by using the lunar landing craft as a "life boat". The tank failure was determined to be caused by two mistakes. The tank's drain fitting had been damaged when it was dropped during factory testing. This necessitated use of its internal heaters to boil out the oxygen after a pre-launch test, which in turn damaged the fan wiring's electrical insulation, because the thermostats on the heaters did not meet the required voltage rating due to a vendor miscommunication.

The crew of Soyuz 11 were killed on June 30, 1971 by a combination of mechanical malfunctions: they were asphyxiated due to cabin decompression following separation of their descent capsule from the service module. A cabin ventilation valve had been jolted open at an altitude of 168 kilometres (551,000ft) by the stronger than expected shock of explosive separation bolts which were designed to fire sequentially, but in fact had fired simultaneously. The loss of pressure became fatal within about 30 seconds.[73]

As of December2015[update], 22 crew members have died in accidents aboard spacecraft. Over 100 others have died in accidents during activity directly related to spaceflight or testing.

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Human spaceflight - Wikipedia

NASA: Space Travel Is Causing Astronauts’ Herpes to Flare Up

Tests show that dormant herpes viruses reactivate in more than half the astronauts who travel on the Space Shuttle and International Space station.

Dormant Viruses

Tests show that dormant herpes viruses reactivate in more than half the astronauts who travel on the Space Shuttle and International Space station, according to new NASA research — a phenomenon the space agency says could pose problems for deep space missions.

“During spaceflight there is a rise in secretion of stress hormones like cortisol and adrenaline, which are known to suppress the immune system, ” said study author Satish Mehta, a researcher at Johnson Space Center, in a press release. “In keeping with this, we find that astronaut’s immune cells — particularly those that normally suppress and eliminate viruses — become less effective during spaceflight and sometimes for up to 60 days after.”

Less Effective

In research published last month in the journal Frontiers in Microbiology, Mehta and colleagues found that astronauts shed more herpes viruses in their urine and saliva than before or after space travel. The culprit, they suspect, is just the stress of spaceflight.

“NASA astronauts endure weeks or even months exposed to microgravity and cosmic radiation — not to mention the extreme G forces of take-off and re-entry,” Mehta said in the press release. “This physical challenge is compounded by more familiar stressors like social separation, confinement and an altered sleep-wake cycle.”

Minor Symptoms

Fortunately, symptoms were relatively rare. Out of 89 astronauts the team studied, only six experienced herpes breakouts in space, according to the paper — a rate of about seven percent.

The viral shedding also got worse the longer the astronauts were off Earth, leading researchers to worry the phenomenon could represent a challenge for deep space travel.

“While only a small proportion develop symptoms, virus reactivation rates increase with spaceflight duration and could present a significant health risk on missions to Mars and beyond,” reads the press release.

READ MORE: Dormant viruses activate during spaceflight [Phys.org]

More on herpes: Immune Cells Working Together To Kill Herpes Virus Captured on Video

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NASA: Space Travel Is Causing Astronauts’ Herpes to Flare Up

Lawyer: People Could Try to Sell the Apollo Moon Footprints

Air and Space Law professor Michelle Hanlon argues that if we don't draft new laws, the destruction of landmarks that happens on Earth will repeat in space.

Interplanetary Heritage

Right now, there’s no legal framework preventing people from destroying or selling culturally-important landmarks in space.

For instance, as space travel becomes more common, an opportunistic someone could find a way to steal and auction off the first bootprints left on the moon by Neil Armstrong, warns University of Mississippi Air and Space Law professor Michelle Hanlon in an essay published Friday in The Conversation.

Earthly Precedent

Hanlon cites damage to landmarks like the Pyramids of Gaza or Terracotta Army by tourists who break off pieces to take home as evidence that people can’t be trusted to preserve landmarks of their own volition.

“There is no law against running over the first bootprints imprinted on the moon,” Hanlon wrote. “Or erasing them. Or carving them out of the moon’s regolith and selling them to the highest bidder.”

Rising Chorus

Places like Stonehenge and ancient cave paintings are protected as part of the U.N.’s World Heritage List. If landmarks in space are to survive as more nations and companies develop the capacity to leave the planet, Hanlon believes that leaders need to be proactive and protect those landmarks before anything goes wrong.

Hanlon is just one of many to recently call for more comprehensive or updated space laws. Right now, the various laws and treaties that pertain to outer space are a bit of a mess. Hopefully, before trips to the moon become commonplace, someone can sort them out.

READ MORE: Protecting human heritage on the moon: Don’t let ‘one small step’ become one giant mistake [The Conversation]

More on space law: Four Legal Challenges to Resolve Before Settling on Mars

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Air Mobility Command > Home > AMC Travel Site

Title 10 USC 2641b: Space-Available Travel on Department of Defense Aircraft

Space-available travel on Department of Defense aircraft:

Program Authorized and Eligible recipients:

(a) AUTHORITY TO ESTABLISH PROGRAM.

(1) The Secretary of Defense may establish a program (in this section referred to as the "travel program") to provide transportation on Department of Defense aircraft on a space-available basis to the categories of individuals eligible under subsection (c)

(2) If the Secretary makes a determination to establish the travel program, the Secretary shall prescribe regulations for the operation of the travel program not later than one year after the date on which the determination was made. The regulations shall take effect on that date or such earlier date as the Secretary shall specify in the regulations.

(3) Not later than 30 days after making the determination to establish the travel program, the Secretary shall submit to the congressional defense committees an initial implementation report describing

(A) the basis for the determination;

(B) any additional categories of individuals to be eligible for the travel program under subsection (c)(S);

(C) how the Secretary will ensure that the travel program is established and operated in compliancewith the conditions specified in subsection (b); and

(D) the metrics by which the Secretary will monitor the travel program to determine the efficient and effective execution of the travel program.

(b) CONDITIONS ON ESTABLISHMENT AND OPERATION.

(1) The Secretary of Defense shall operate the travel program in a budget-neutral manner.

(2) No additional funds may be used, or flight hours performed, for the purpose of providing transportation under the travel program.

(c) ELIGIBLE INDIVIDUALS. Subject to subsection (d), the Secretary of Defense shall provide transportation under the travel program (if established) to the following categories of individuals:

(1) Members of the armed forces on active duty.

(2) Members of the Selected Reserve who hold a valid Uniformed Services Identification and Privilege Card

(3) Retired members of a regular or reserve component of the armed forces, including retired members of reserve components who, but for being under the eligibility age applicable under section 12731 of this title, would be eligible for retired pay under chapter 1223 of this title.

(4) Such categories of dependents of individuals described in paragraphs (1) through (3) as the Secretary shall specify in the regulations under subsection (a), under such conditions and circumstances as the Secretary shall specify in such regulations.

(5) Such other categories of individuals as the Secretary, in the discretion of the Secretary, considers appropriate.

(d) PRIORITIES AND RESTRICTIONSIn operating the travel program, the Secretary of Defense shall-

(1) in the sole discretion of the Secretary, establish an order of priority for transportation under the travel program for categories of eligible individuals that is based on considerations of military necessity, humanitarian concerns, and enhancement of morale;

(2) give priority in consideration of transportation under the travel program to the demands of members of the armed forces in the regular components and in the reserve components on active duty and to the need to provide such members, and their dependents, a means of respite from such demands; and

(3) implement policies aimed at ensuring cost control (as required by subsection (b)) and the safety, security, and efficient processing of travelers, including limiting the benefit under the travel program to one or more categories of otherwise eligible individuals if considered necessary by the Secretary.

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Time travel – Wikipedia

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically using a hypothetical device known as a time machine. Time travel is a widely-recognized concept in philosophy and fiction. The idea of a time machine was popularized by H. G. Wells' 1895 novel The Time Machine.

It is uncertain if time travel to the past is physically possible. Forward time travel, outside the usual sense of the perception of time, is an extensively-observed phenomenon and well-understood within the framework of special relativity and general relativity. However, making one body advance or delay more than a few milliseconds compared to another body is not feasible with current technology.[1] As for backwards time travel, it is possible to find solutions in general relativity that allow for it, but the solutions require conditions that may not be physically possible. Traveling to an arbitrary point in spacetime has a very limited support in theoretical physics, and usually only connected with quantum mechanics or wormholes, also known as Einstein-Rosen bridges.

Some ancient myths depict a character skipping forward in time. In Hindu mythology, the Mahabharata mentions the story of King Raivata Kakudmi, who travels to heaven to meet the creator Brahma and is surprised to learn when he returns to Earth that many ages have passed.[2] The Buddhist Pli Canon mentions the relativity of time. The Payasi Sutta tells of one of the Buddha's chief disciples, Kumara Kassapa, who explains to the skeptic Payasi that time in the Heavens passes differently than on Earth.[3] The Japanese tale of "Urashima Tar",[4] first described in the Nihongi (720) tells of a young fisherman named Urashima Taro who visits an undersea palace. After three days, he returns home to his village and finds himself 300 years in the future, where he has been forgotten, his house is in ruins, and his family has died.[5] In Jewish tradition, the 1st-century BC scholar Honi ha-M'agel is said to have fallen asleep and slept for seventy years. When waking up he returned home but found none of the people he knew, and no one believed his claims of who he was.[6]

Early science fiction stories feature characters who sleep for years and awaken in a changed society, or are transported to the past through supernatural means. Among them L'An 2440, rve s'il en ft jamais (1770) by Louis-Sbastien Mercier, Rip Van Winkle (1819) by Washington Irving, Looking Backward (1888) by Edward Bellamy, and When the Sleeper Awakes (1899) by H.G. Wells. Prolonged sleep, like the more familiar time machine, is used as a means of time travel in these stories.[7]

The earliest work about backwards time travel is uncertain. Samuel Madden's Memoirs of the Twentieth Century (1733) is a series of letters from British ambassadors in 1997 and 1998 to diplomats in the past, conveying the political and religious conditions of the future.[8]:9596 Because the narrator receives these letters from his guardian angel, Paul Alkon suggests in his book Origins of Futuristic Fiction that "the first time-traveler in English literature is a guardian angel."[8]:85 Madden does not explain how the angel obtains these documents, but Alkon asserts that Madden "deserves recognition as the first to toy with the rich idea of time-travel in the form of an artifact sent backward from the future to be discovered in the present."[8]:9596 In the science fiction anthology Far Boundaries (1951), editor August Derleth claims that an early short story about time travel is Missing One's Coach: An Anachronism, written for the Dublin Literary Magazine[9] by an anonymous author in 1838.[10]:3 While the narrator waits under a tree for a coach to take him out of Newcastle, he is transported back in time over a thousand years. He encounters the Venerable Bede in a monastery and explains to him the developments of the coming centuries. However, the story never makes it clear whether these events are real or a dream.[10]:1138 Another early work about time travel is The Forebears of Kalimeros: Alexander, son of Philip of Macedon by Alexander Veltman published in 1836.[11]

Charles Dickens's A Christmas Carol (1843) has early depictions of time travel in both directions, as the protagonist, Ebenezer Scrooge, is transported to Christmases past and future. Other stories employ the same template, where a character naturally goes to sleep, and upon waking up find themselves in a different time.[12] A clearer example of backward time travel is found in the popular 1861 book Paris avant les hommes (Paris before Men) by the French botanist and geologist Pierre Boitard, published posthumously. In this story, the protagonist is transported to the prehistoric past by the magic of a "lame demon" (a French pun on Boitard's name), where he encounters a Plesiosaur and an apelike ancestor and is able to interact with ancient creatures.[13] Edward Everett Hale's "Hands Off" (1881) tells the story of an unnamed being, possibly the soul of a person who has recently died, who interferes with ancient Egyptian history by preventing Joseph's enslavement. This may have been the first story to feature an alternate history created as a result of time travel.[14]:54

One of the first stories to feature time travel by means of a machine is "The Clock that Went Backward" by Edward Page Mitchell,[15] which appeared in the New York Sun in 1881. However, the mechanism borders on fantasy. An unusual clock, when wound, runs backwards and transports people nearby back in time. The author does not explain the origin or properties of the clock.[14]:55 Enrique Gaspar y Rimbau's El Anacronpete (1887) may have been the first story to feature a vessel engineered to travel through time.[16][17] Andrew Sawyer has commented that the story "does seem to be the first literary description of a time machine noted so far", adding that "Edward Page Mitchell's story 'The Clock That Went Backward' (1881) is usually described as the first time-machine story, but I'm not sure that a clock quite counts."[18] H. G. Wells's The Time Machine (1895) popularized the concept of time travel by mechanical means.[19]

Some theories, most notably special and general relativity, suggest that suitable geometries of spacetime or specific types of motion in space might allow time travel into the past and future if these geometries or motions were possible.[20]:499 In technical papers, physicists discuss the possibility of closed timelike curves, which are world lines that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves, such as Gdel spacetime, but the physical plausibility of these solutions is uncertain.

Many in the scientific community believe that backward time travel is highly unlikely. Any theory that would allow time travel would introduce potential problems of causality.[21] The classic example of a problem involving causality is the "grandfather paradox": what if one were to go back in time and kill one's own grandfather before one's father was conceived? Some physicists, such as Novikov and Deutsch, suggested that these sorts of temporal paradoxes can be avoided through the Novikov self-consistency principle or to a variation of the many-worlds interpretation with interacting worlds.[22]

Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, transversable wormholes, and Alcubierre drive.[23][24]:33130 The theory of general relativity does suggest a scientific basis for the possibility of backward time travel in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed.[25] These semiclassical arguments led Stephen Hawking to formulate the chronology protection conjecture, suggesting that the fundamental laws of nature prevent time travel,[26] but physicists cannot come to a definite judgment on the issue without a theory of quantum gravity to join quantum mechanics and general relativity into a completely unified theory.[27][28]:150

The theory of general relativity describes the universe under a system of field equations that determine the metric, or distance function, of spacetime. There exist exact solutions to these equations that include closed time-like curves, which are world lines that intersect themselves; some point in the causal future of the world line is also in its causal past, a situation which is akin to time travel. Such a solution was first proposed by Kurt Gdel, a solution known as the Gdel metric, but his (and others') solution requires the universe to have physical characteristics that it does not appear to have,[20]:499 such as rotation and lack of Hubble expansion. Whether general relativity forbids closed time-like curves for all realistic conditions is still being researched.[29]

Wormholes are a hypothetical warped spacetime which are permitted by the Einstein field equations of general relativity.[30]:100 A proposed time-travel machine using a traversable wormhole would hypothetically work in the following way: One end of the wormhole is accelerated to some significant fraction of the speed of light, perhaps with some advanced propulsion system, and then brought back to the point of origin. Alternatively, another way is to take one entrance of the wormhole and move it to within the gravitational field of an object that has higher gravity than the other entrance, and then return it to a position near the other entrance. For both of these methods, time dilation causes the end of the wormhole that has been moved to have aged less, or become "younger", than the stationary end as seen by an external observer; however, time connects differently through the wormhole than outside it, so that synchronized clocks at either end of the wormhole will always remain synchronized as seen by an observer passing through the wormhole, no matter how the two ends move around.[20]:502 This means that an observer entering the "younger" end would exit the "older" end at a time when it was the same age as the "younger" end, effectively going back in time as seen by an observer from the outside. One significant limitation of such a time machine is that it is only possible to go as far back in time as the initial creation of the machine;[20]:503 in essence, it is more of a path through time than it is a device that itself moves through time, and it would not allow the technology itself to be moved backward in time.

According to current theories on the nature of wormholes, construction of a traversable wormhole would require the existence of a substance with negative energy, often referred to as "exotic matter". More technically, the wormhole spacetime requires a distribution of energy that violates various energy conditions, such as the null energy condition along with the weak, strong, and dominant energy conditions. However, it is known that quantum effects can lead to small measurable violations of the null energy condition,[30]:101 and many physicists believe that the required negative energy may actually be possible due to the Casimir effect in quantum physics.[31] Although early calculations suggested a very large amount of negative energy would be required, later calculations showed that the amount of negative energy can be made arbitrarily small.[32]

In 1993, Matt Visser argued that the two mouths of a wormhole with such an induced clock difference could not be brought together without inducing quantum field and gravitational effects that would either make the wormhole collapse or the two mouths repel each other.[33] Because of this, the two mouths could not be brought close enough for causality violation to take place. However, in a 1997 paper, Visser hypothesized that a complex "Roman ring" (named after Tom Roman) configuration of an N number of wormholes arranged in a symmetric polygon could still act as a time machine, although he concludes that this is more likely a flaw in classical quantum gravity theory rather than proof that causality violation is possible.[34]

Another approach involves a dense spinning cylinder usually referred to as a Tipler cylinder, a GR solution discovered by Willem Jacob van Stockum[35] in 1936 and Kornel Lanczos[36] in 1924, but not recognized as allowing closed timelike curves[37]:21 until an analysis by Frank Tipler[38] in 1974. If a cylinder is infinitely long and spins fast enough about its long axis, then a spaceship flying around the cylinder on a spiral path could travel back in time (or forward, depending on the direction of its spiral). However, the density and speed required is so great that ordinary matter is not strong enough to construct it. A similar device might be built from a cosmic string, but none are known to exist, and it does not seem to be possible to create a new cosmic string. Physicist Ronald Mallett is attempting to recreate the conditions of a rotating black hole with ring lasers, in order to bend spacetime and allow for time travel.[39]

A more fundamental objection to time travel schemes based on rotating cylinders or cosmic strings has been put forward by Stephen Hawking, who proved a theorem showing that according to general relativity it is impossible to build a time machine of a special type (a "time machine with the compactly generated Cauchy horizon") in a region where the weak energy condition is satisfied, meaning that the region contains no matter with negative energy density (exotic matter). Solutions such as Tipler's assume cylinders of infinite length, which are easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough,[37]:169 he did not prove this. But Hawking points out that because of his theorem, "it can't be done with positive energy density everywhere! I can prove that to build a finite time machine, you need negative energy."[28]:96 This result comes from Hawking's 1992 paper on the chronology protection conjecture, where he examines "the case that the causality violations appear in a finite region of spacetime without curvature singularities" and proves that "there will be a Cauchy horizon that is compactly generated and that in general contains one or more closed null geodesics which will be incomplete. One can define geometrical quantities that measure the Lorentz boost and area increase on going round these closed null geodesics. If the causality violation developed from a noncompact initial surface, the averaged weak energy condition must be violated on the Cauchy horizon."[26] This theorem does not rule out the possibility of time travel by means of time machines with the non-compactly generated Cauchy horizons (such as the Deutsch-Politzer time machine) or in regions which contain exotic matter, which would be used for traversable wormholes or the Alcubierre drive.

When a signal is sent from one location and received at another location, then as long as the signal is moving at the speed of light or slower, the mathematics of simultaneity in the theory of relativity show that all reference frames agree that the transmission-event happened before the reception-event. When the signal travels faster than light, it is received before it is sent, in all reference frames.[40] The signal could be said to have moved backward in time. This hypothetical scenario is sometimes referred to as a tachyonic antitelephone.[41]

Quantum-mechanical phenomena such as quantum teleportation, the EPR paradox, or quantum entanglement might appear to create a mechanism that allows for faster-than-light (FTL) communication or time travel, and in fact some interpretations of quantum mechanics such as the Bohm interpretation presume that some information is being exchanged between particles instantaneously in order to maintain correlations between particles.[42] This effect was referred to as "spooky action at a distance" by Einstein.

Nevertheless, the fact that causality is preserved in quantum mechanics is a rigorous result in modern quantum field theories, and therefore modern theories do not allow for time travel or FTL communication. In any specific instance where FTL has been claimed, more detailed analysis has proven that to get a signal, some form of classical communication must also be used.[43] The no-communication theorem also gives a general proof that quantum entanglement cannot be used to transmit information faster than classical signals.

A variation of Everett's many-worlds interpretation (MWI) of quantum mechanics provides a resolution to the grandfather paradox that involves the time traveler arriving in a different universe than the one they came from; it's been argued that since the traveler arrives in a different universe's history and not their own history, this is not "genuine" time travel.[44] The accepted many-worlds interpretation suggests that all possible quantum events can occur in mutually exclusive histories.[45] However, some variations allow different universes to interact. This concept is most often used in science-fiction, but some physicists such as David Deutsch have suggested that a time traveler should end up in a different history than the one he started from.[46][47] On the other hand, Stephen Hawking has argued that even if the MWI is correct, we should expect each time traveler to experience a single self-consistent history, so that time travelers remain within their own world rather than traveling to a different one.[48] The physicist Allen Everett argued that Deutsch's approach "involves modifying fundamental principles of quantum mechanics; it certainly goes beyond simply adopting the MWI". Everett also argues that even if Deutsch's approach is correct, it would imply that any macroscopic object composed of multiple particles would be split apart when traveling back in time through a wormhole, with different particles emerging in different worlds.[22]

Certain experiments carried out give the impression of reversed causality, but fail to show it under closer examination.

The delayed choice quantum eraser experiment performed by Marlan Scully involves pairs of entangled photons that are divided into "signal photons" and "idler photons", with the signal photons emerging from one of two locations and their position later measured as in the double-slit experiment. Depending on how the idler photon is measured, the experimenter can either learn which of the two locations the signal photon emerged from or "erase" that information. Even though the signal photons can be measured before the choice has been made about the idler photons, the choice seems to retroactively determine whether or not an interference pattern is observed when one correlates measurements of idler photons to the corresponding signal photons. However, since interference can only be observed after the idler photons are measured and they are correlated with the signal photons, there is no way for experimenters to tell what choice will be made in advance just by looking at the signal photons, only by gathering classical information from the entire system; thus causality is preserved.[49]

The experiment of Lijun Wang might also show causality violation since it made it possible to send packages of waves through a bulb of caesium gas in such a way that the package appeared to exit the bulb 62 nanoseconds before its entry, but a wave package is not a single well-defined object but rather a sum of multiple waves of different frequencies (see Fourier analysis), and the package can appear to move faster than light or even backward in time even if none of the pure waves in the sum do so. This effect cannot be used to send any matter, energy, or information faster than light,[50] so this experiment is understood not to violate causality either.

The physicists Gnter Nimtz and Alfons Stahlhofen, of the University of Koblenz, claim to have violated Einstein's theory of relativity by transmitting photons faster than the speed of light. They say they have conducted an experiment in which microwave photons traveled "instantaneously" between a pair of prisms that had been moved up to 3ft (0.91m) apart, using a phenomenon known as quantum tunneling. Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of." However, other physicists say that this phenomenon does not allow information to be transmitted faster than light. Aephraim Steinberg, a quantum optics expert at the University of Toronto, Canada, uses the analogy of a train traveling from Chicago to New York, but dropping off train cars at each station along the way, so that the center of the train moves forward at each stop; in this way, the speed of the center of the train exceeds the speed of any of the individual cars.[51]

Shengwang Du claims in a peer-reviewed journal to have observed single photons' precursors, saying that they travel no faster than c in a vacuum. His experiment involved slow light as well as passing light through a vacuum. He generated two single photons, passing one through rubidium atoms that had been cooled with a laser (thus slowing the light) and passing one through a vacuum. Both times, apparently, the precursors preceded the photons' main bodies, and the precursor traveled at c in a vacuum. According to Du, this implies that there is no possibility of light traveling faster than c and, thus, no possibility of violating causality.[52]

The absence of time travelers from the future is a variation of the Fermi paradox. As the absence of extraterrestrial visitors does not prove they do not exist, so the absence of time travelers fails to prove time travel is physically impossible; it might be that time travel is physically possible but is never developed or is cautiously used. Carl Sagan once suggested the possibility that time travelers could be here but are disguising their existence or are not recognized as time travelers.[27] Some versions of general relativity suggest that time travel might only be possible in a region of spacetime that is warped a certain way, and hence time travelers would not be able to travel back to earlier regions in spacetime, before this region existed. Stephen Hawking stated that this would explain why the world has not already been overrun by "tourists from the future."[48]

Several experiments have been carried out to try to entice future humans, who might invent time travel technology, to come back and demonstrate it to people of the present time. Events such as Perth's Destination Day or MIT's Time Traveler Convention heavily publicized permanent "advertisements" of a meeting time and place for future time travelers to meet.[53] In 1982, a group in Baltimore, Maryland, identifying itself as the Krononauts, hosted an event of this type welcoming visitors from the future.[54][55] These experiments only stood the possibility of generating a positive result demonstrating the existence of time travel, but have failed so farno time travelers are known to have attended either event. Some versions of the many-worlds interpretation can be used to suggest that future humans have traveled back in time, but have traveled back to the meeting time and place in a parallel universe.[56]

There is a great deal of observable evidence for time dilation in special relativity[57] and gravitational time dilation in general relativity,[58][59][60] for example in the famous and easy-to-replicate observation of atmospheric muon decay.[61][62][63] The theory of relativity states that the speed of light is invariant for all observers in any frame of reference; that is, it is always the same. Time dilation is a direct consequence of the invariance of the speed of light.[63] Time dilation may be regarded in a limited sense as "time travel into the future": a person may use time dilation so that a small amount of proper time passes for them, while a large amount of proper time passes elsewhere. This can be achieved by traveling at relativistic speeds or through the effects of gravity.[64]

For two identical clocks moving relative to each other without accelerating, each clock measures the other to be ticking slower. This is possible due to the relativity of simultaneity. However, the symmetry is broken if one clock accelerates, allowing for less proper time to pass for one clock than the other. The twin paradox describes this: one twin remains on Earth, while the other undergoes acceleration to relativistic speed as they travel into space, turn around, and travel back to Earth; the traveling twin ages less than the twin who stayed on Earth, because of the time dilation experienced during their acceleration. General relativity treats the effects of acceleration and the effects of gravity as equivalent, and shows that time dilation also occurs in gravity wells, with a clock deeper in the well ticking more slowly; this effect is taken into account when calibrating the clocks on the satellites of the Global Positioning System, and it could lead to significant differences in rates of aging for observers at different distances from a large gravity well such as a black hole.[24]:33130

A time machine that utilizes this principle might be, for instance, a spherical shell with a diameter of 5 meters and the mass of Jupiter. A person at its center will travel forward in time at a rate four times that of distant observers. Squeezing the mass of a large planet into such a small structure is not expected to be within humanity's technological capabilities in the near future.[24]:76140 With current technologies, it is only possible to cause a human traveler to age less than companions on Earth by a very small fraction of a second, the current record being about one-fiftieth of a second for the cosmonaut Sergei Krikalev.[65]

Philosophers have discussed the nature of time since at least the time of ancient Greece; for example, Parmenides presented the view that time is an illusion. Centuries later, Isaac Newton supported the idea of absolute time, while his contemporary Gottfried Wilhelm Leibniz maintained that time is only a relation between events and it cannot be expressed independently. The latter approach eventually gave rise to the spacetime of relativity.[66]

Many philosophers have argued that relativity implies eternalism, the idea that the past and future exist in a real sense, not only as changes that occurred or will occur to the present.[67] Philosopher of science Dean Rickles disagrees with some qualifications, but notes that "the consensus among philosophers seems to be that special and general relativity are incompatible with presentism."[68] Some philosophers view time as a dimension equal to spatial dimensions, that future events are "already there" in the same sense different places exist, and that there is no objective flow of time; however, this view is disputed.[69]

Presentism is a school of philosophy that holds that the future and the past exist only as changes that occurred or will occur to the present, and they have no real existence of their own. In this view, time travel is impossible because there is no future or past to travel to.[67] Keller and Nelson have argued that even if past and future objects do not exist, there can still be definite truths about past and future events, and thus it is possible that a future truth about a time traveler deciding to travel back to the present date could explain the time traveler's actual appearance in the present;[70] these views are contested by some authors.[71]

Presentism in classical spacetime deems that only the present exists; this is not reconcilable with special relativity, shown in the following example: Alice and Bob are simultaneous observers of event O. For Alice, some event E is simultaneous with O, but for Bob, event E is in the past or future. Therefore, Alice and Bob disagree about what exists in the present, which contradicts classical presentism. "Here-now presentism" attempts to reconcile this by only acknowledging the time and space of a single point; this is unsatisfactory because objects coming and going from the "here-now" alternate between real and unreal, in addition to the lack of a privileged "here-now" that would be the "real" present. "Relativized presentism" acknowledges that there are infinite frames of reference, each of them has a different set of simultaneous events, which makes it impossible to distinguish a single "real" present, and hence either all events in time are realblurring the difference between presentism and eternalismor each frame of reference exists in its own reality. Options for presentism in special relativity appear to be exhausted, but Gdel and others suspect presentism may be valid for some forms of general relativity.[72] Generally, the idea of absolute time and space is considered incompatible with general relativity; there is no universal truth about the absolute position of events which occur at different times, and thus no way to determine which point in space at one time is at the universal "same position" at another time,[73] and all coordinate systems are on equal footing as given by the principle of diffeomorphism invariance.[74]

A common objection to the idea of traveling back in time is put forth in the grandfather paradox or the argument of auto-infanticide.[75] If one were able to go back in time, inconsistencies and contradictions would ensue if the time traveler were to change anything; there is a contradiction if the past becomes different from the way it is.[76][77] The paradox is commonly described with a person who travels to the past and kills their own grandfather, prevents the existence of their father or mother, and therefore their own existence.[27] Philosophers question whether these paradoxes make time travel impossible. Some philosophers answer the paradoxes by arguing that it might be the case that backward time travel could be possible but that it would be impossible to actually change the past in any way,[78] an idea similar to the proposed Novikov self-consistency principle in physics.

According to the philosophical theory of compossibility, what can happen, for example in the context of time travel, must be weighed against the context of everything relating to the situation. If the past is a certain way, it's not possible for it to be any other way. What can happen when a time traveler visits the past is limited to what did happen, in order to prevent logical contradictions.[79]

The Novikov self-consistency principle, named after Igor Dmitrievich Novikov, states that any actions taken by a time traveler or by an object that travels back in time were part of history all along, and therefore it is impossible for the time traveler to "change" history in any way. The time traveler's actions may be the cause of events in their own past though, which leads to the potential for circular causation, sometimes called a predestination paradox,[80] ontological paradox,[81] or bootstrap paradox.[81][82] The term bootstrap paradox was popularized by Robert A. Heinlein's story "By His Bootstraps".[83] The Novikov self-consistency principle proposes that the local laws of physics in a region of spacetime containing time travelers cannot be any different from the local laws of physics in any other region of spacetime.[84]

The philosopher Kelley L. Ross argues in "Time Travel Paradoxes"[85] that in a scenario involving a physical object whose world-line or history forms a closed loop in time there can be a violation of the second law of thermodynamics. Ross uses "Somewhere in Time" as an example of such an ontological paradox, where a watch is given to a person, and 60 years later the same watch is brought back in time and given to the same character. Ross states that entropy of the watch will increase, and the watch carried back in time will be more worn with each repetition of its history. The second law of thermodynamics is understood by modern physicists to be a statistical law, so decreasing entropy or non-increasing entropy are not impossible, just improbable. Additionally, entropy statistically increases in systems which are isolated, so non-isolated systems, such as an object, that interact with the outside world, can become less worn and decrease in entropy, and it's possible for an object whose world-line forms a closed loop to be always in the same condition in the same point of its history.[24]:23

Daniel Greenberger and Karl Svozil proposed that quantum theory gives a model for time travel where the past must be self-consistent.[86][87]

Time travel themes in science fiction and the media can generally be grouped into three categories: immutable timeline; mutable timeline; and alternate histories, as in the interacting-many-worlds interpretation.[88][89][90] Frequently in fiction, timeline is used to refer to all physical events in history, so that in time travel stories where events can be changed, the time traveler is described as creating a new or altered timeline.[91] This usage is distinct from the use of the term timeline to refer to a type of chart that illustrates a particular series of events, and the concept is also distinct from a world line, a term from Einstein's theory of relativity which refers to the entire history of a single object.

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