Monthly Archives: May 2017

Enlarge / Home, sweet colony. Saturn's moon Titan.

For a while now, there's been a debate in the US over how to direct NASA's next major human spaceflight initiative. Do we build an outpost on the Moon as a step towards Mars, or do we just head straight for the red planet? Which ever destination we choose, it'll be viewed as the first step toward a permanent human presence outside of the immediate neighborhood of the Earth.

All of that indecision, according to a new book called Beyond Earth, is misguided. Either of these destinations presents so many challenges and compromises that attracting and supporting anything more than short-term visitors will be difficult. Instead, Beyond Earth argues, we should set our sights much farther out in the Solar System if we want to create a permanent human presence elsewhere. The authors' destination of choice? Titan, the largest moon of Saturn.

Colonizing Titan seems like an outrageous argument, given that the only spacecraft we've put in orbit around Saturn took seven years to get there. Why should anyone take Beyond Earth seriously? Well, its authors aren't crackpots or mindless space fans. Amanda Hendrix is a planetary scientist who's worked at the Jet Propulsion Laboratory and the Planetary Science Institute. For the book, she's partnered with Charles Wohlforth, an environmental journalist who understands some things about establishing a livable environment. And the two of them have conducted extensive interviews, talking to people at NASA and elsewhere about everything from the health complications of space to future propulsion systems.

An interview with the authors about colonizing Titan

The resulting book is a mix of where we are now, which problems need to be solved to make a home elsewhere, and a future scenario that drives us to solve those problems. In this sense, Beyond Earth is a bit like the recent National Geographic effort Mars, which blended present-day documentary with a fictionalized future. But the book is a little easier to swallow then the miniseries, which shunted viewers between footage of real-life rockets and CGI dust storms.

So, why Titan? The two closer destinations, the Moon and Mars, have atmospheres that are effectively nonexistent. That means any habitation will have to be extremely robust to hold its contents in place. Both worlds are also bathed in radiation, meaning those habitats will need to be built underground, as will any agricultural areas to feed the colonists. Any activities on the surface will have to be limited to avoid excessive radiation exposure.

Would anyone want to go to a brand-new world just to spend their lives in a cramped tunnel? Hendrix and Wohlforth suggest the answer will be "no." Titan, in contrast, offers a dense atmosphere that shields the surface from radiation and would make any structural failures problematic, rather than catastrophic. With an oxygen mask and enough warm clothing, humans could roam Titan's surface in the dim sunlight. Or, given the low gravity and dense atmosphere, they could float above it in a balloon or on personal wings.

The vast hydrocarbon seas and dunes, Hendrix and Wohlforth suggest, would allow polymers to handle many of the roles currently played by metal and wood. Drilling into Titan's crust would access a vast supply of liquid water in the moon's subsurface ocean. It's not all the comforts of home, but it's a lot more of them than you'd get on the Moon or Mars.

There is the distance thing, which Hendrix and Wohlforth acknowledge, but they argue it's a bit besides the point. The radiation and lack of gravity that make long-range space travel a risk would all bite anyone we sent to explore Mars. NASA assumes it'll find solutions, but the authors are critical of the Agency promoting a journey to Mars without already having solved them. Whether we go to Mars or Titan, the solution is speed: less time in space means less risk. And, if we could rocket along fast enough so that a round-trip to Mars with time spent exploring was safe, then we could do a one-way trip to Titan.

So, Beyond Earth is a good look at the current state of human space-exploration technology, as well as how that will hold us back from doing the things we want to do. It's both thoughtful and thought-provoking.

Mixed in with that, however, is a scenario under which Earth will get its act together and do what needs to be done to overcome these technological hurdles. That scenario is driven in part by a very believable desperation, caused by unaddressed climate change that drives wars and radicalization. Low Earth orbit becomes cheap, and then an efficient new thruster is developed. (Unfortunately, the thruster of choice in this scenario is unlikely to ever work.)

The Earth's governments bands together in a massive effort to send colonists to Titan, who almost immediately begin to view themselves as pioneers who boldly settle a new world with no help from anyone. Tensions and cultural differences ensue. This part of the book is a fun yarn, and plenty of it involves believable extrapolations from our current state. Whether it adds to Beyond Earth overall will probably be a matter of personal taste.

While the focus of the book is on leaving Earth, it's hard to escape the sense that Beyond Earth is an extensive argument for staying put. As Hendrix and Wohlforth repeatedly drive home, there's no place we could go in our Solar System that offers anything close to what the Earth provides for us. Going anywhere else would involve a cost that could go a long way toward making our existence here much more sustainable. While I'm all for eventually establishing a presence elsewhere, it would be nice to do so by choice, rather than end up being forced to do so due to our carelessness on Earth.

Continued here:
Forget Marslet's go colonize Titan! - Ars Technica

Al Globus and Joe Strout have an analysis that space settlements in low (~500 km) Earth equatorial orbits may not require any radiation shielding at all. This is based on a careful analysis of requirements and extensive simulation of radiation effects. This radically reduces system mass and has profound implications for space settlement, as extraterrestrial mining and manufacturing are no longer on the critical path to the first settlements, although they will be essential in later stages. It also means the first settlements can evolve from space stations, hotels, and retirement communities in relatively small steps.

This huge reduction in total mass compensates for the greater energetic difficulty of launching materials from Earth to ELEO as opposed to launching from the Moon to L5, the design location of the Stanford Torus. In the early studies, the EarthMoon L5 point was chosen as the location of a settlement for the energetic advantage of launching materials from the Moon. Going from the Moon to L5 requires a delta-v 3 of 2.3 km/sec, and going from Earth to 500 km ELEO is 10 km/sec [Cassell 2015]. Using the velocity squared as our energy measure , Earth to ELEO requires 19 times more energy per unit mass. Analysis suggests that at least 19 times less mass is needed if no radiation shielding is required. Thus, the energetic advantage to launching the mass of a settlement with deep space radiation shielding from the Moon to L5 is balanced by launching far less mass from Earth if no radiation shielding is necessary.

A 500 km circular ELEO using polyethylene shielding was analyzed. Even at 10 kg/m2 shielding, the equivalent of which is very likely to be provided by any reasonable hull, the 20 mSv/yr and 6.6 mGy/yr are met. Indeed, with no shielding at all the general population limit is met and the pregnancy limit is very nearly met. This has an interesting consequence: spacewalks in ELEO may be safe enough from a radiation point of view to be a significant recreational activity.

The total mass of the 4 rpm unshielded (56 meter diameter Stanford Torus, 123 person) space colony could be launched from Earth with about 40 Falcon Heavy vehicles.

The space settlement rotation rate recommendations of [Globus 2015] are: Up to 2 rpm (rotations per minute) should be no problem for residents and require little adaptation by visitors. Up to 4 rpm should be no problem for residents but will require some training and/or a few hours to perhaps a day or two of adaptation by visitors. Up to 6 rpm is unlikely to be a problem for residents but may require extensive visitor training and/or adaptation over a few days. Some particularly susceptible individuals may have a great deal of difficulty. Up to 10 rpm adaptation has been achieved with specific training. However, the diameter of a settlement at these rotation rates is so small (under ~40 meter for seven rpm) its hard to imagine anyone wanting to live there permanently, much less raise children. Rotation at high rates, however, may be useful for a dedicated radiation study station in ELEO.

Note that there are two classes of people that must be accommodated: residents and visitors. For residents a few days of feeling ill at the beginning of a multiyear stay is of little concern. However, if a settlement expects many short term visitors it may be best to keep the rotation rate under about 4 rpm.

The Kalpana One space station design at 4 rpm requires 17 tons/person. The cheapest advertised price today for delivering mass to orbit is the Falcon Heavy, in development, at $90 million for 53 tons to LEO [SpaceX 2015], or $1.7 million per ton. For 17 tons that is about $29 million.

The cheapest advertised price to launch people to LEO is a bit over $26 million/seat on a Falcon 9/Dragon which includes a stay at a Bigelow space station [Bigelow 2015], also in development. It should be noted that this cost must be incurred for settlers going to any space location.

Combining these two costs gives us (rounding up) $60 million per person. This does not include materials, construction or resupply costs. We assume that government or space tourism businesses will conduct most of the research and development cost other than actually building a settlement.

To get the transportation costs to close to one million dollars, leaving some small number of millions for everything else, we need to reduce the cost of launch by about a factor of 50 to around $1.2Million/person. Notice that these are extremely rough calculations, but are sufficient for planning purposes.

Elon Musk is trying to make hundreds of flights per year economic by launching and maintaining a network of 4000-20,000 internet satellites.

To reach a 50 times price reduction will almost certainly require fully reusable launch vehicles, much improved technology and a very high flight rate, probably in the tens of thousands per year. The reusability and technology requirements are generally recognized but for some reason flight rate is often ignored. However, with fewer than 100 launches per year today, a single reusable vehicle capable of two flights a week could, theoretically, satisfy the entire launch market! Even 1,000 flights per year would only require 10 such vehicles. Large reductions in price will not come if vehicles are built in such small numbers. Launch vehicles only make money when they fly, so we need a very high flight rate, probably over 10,000 flights/year.

There are only two applications that, at the right price, could create a market requiring a flight rate of ten of thousands or more per year: space solar power (SSP) and tourism. SSP requires a very large investment up front before any income is generated and is vulnerable to terrestrial competition, particularly as batteries improve.

Tourism was a $2.3 trillion/year industry in 2014.

The rest is here:
Towards an Economically Viable roadmap to large scale space ... - Next Big Future

Moon Express is one of only two teams in the Google Lunar XPRIZE competition with a verified launch contract for its 2017 lunar mission. In October 2015, Moon Express announced that it had signed the worlds first multi-mission launch contract with Rocket Lab USA for 3 lunar missions between 2017 and 2020.

Moon Express sees the moon as critical for humanity to become a multi-world species, and that our sister world, the Moon, is an eighth continent holding vast resources than can help us enrich and secure our future.

MoonEx had been planning to place the International Lunar Observatory (ILO) on the Moon as early as 2018. The plan calls for placement of both a 2 meters (6 ft 7 in) radio telescope as well as an optical telescope at the South Pole of the Moon.

Rick Tumlinson, chairman of Deep Space Industries, plans to land its first prospector on an asteroid by 2020.

Deep Space Industries will use small scouts to explore and study prospective targets. A larger robot will land on high value asteroids to mine and process material. It will use solar power to evaporate and capture water from the sample.

Water, we believe, is relatively easy to harvest from asteroid materials, said Tumlinson.

By 2025 they could be producing serious quantities of resources.

Deep Space Industries and the University of Tennessee were awarded NASA Innovative Advanced Concepts (NIAC) program funding for developing technology to slow spacecraft carrying asteroid resources as they return to Earths orbit.

The purpose of asteroid mining is to collect fuel and building materials harvested from near Earth asteroids and provide them to commercial and government missions. One major challenge to making asteroid mining a reality is slowing down the returning mining spacecraft as they approach Earth. Returning from distant destinations, these spacecraft will be traveling at high speeds, so slowing them down enough to slip into orbit is quite difficult.

Current braking methods call for the returning asteroid mining spacecraft to expend a great deal of propellant to slow itself down enough to achieve low Earth orbit insertion. However, propellant is heavy and valuable, so if another way of slowing the spacecraft could be devised, it would significantly help the economics of asteroid mining missions.

The NASA grant will research the manufacturing of an aerobrake system from the asteroids regolith (soil) collected from mining operations. The idea is that the fully laden asteroid mining spacecraft will use the collected material to manufacture a braking system during its journey back to Earths orbit. The aerobrake system would act as a large heat shield that would allow the spacecraft to pass through Earths atmosphere, creating enough drag to slow down the payload without using propellant.

Using aerobrakes instead of propellant will expand by 30 to 100 times the number of asteroids where water and other supplies can be affordably delivered to markets in Earth orbit, said Dr. John S. Lewis, chief scientist at DSI. In the near future, explains Lewis, asteroid resources will support space stations, expeditions to the Moon and Mars, and the transfer of payloads from low orbit to geosynchronous orbit by space-based tugs refueled with asteroid propellant.

Planetary Resources is also focused on water.

You can concentrate that solar energy and heat up the surface of the asteroid and literally bake off the water in the same way youd bake a clay pot, says CEO Chris Lewicki.

Both Lewicki and Tumlinson want to supply building materials in space, which could allow for the construction of super-massive floating structures that would be ungainly to launch from Earth.

This was the old L5 colonization vision.

National Space Society has updated analysis of the enormous growth potential of orbital space colonization and near earth settlement. If the single largest asteroid (Ceres) were to be used to build orbital space settlements, the total living area created would be well over a hundred times the land area of the Earth. This is because Ceres is a solid, three dimensional object but orbital space settlements are basically hollow with only air on the inside. Thus, Ceres alone can provide the building materials for uncrowded homes for hundreds of billions of people, at least.

Original post:
Moon as unprospected eighth continent that will produce trillionaires ... - Next Big Future