One day we’ll want a place humans can live beyond Earth. Mars and a number of the moons of the gas giants are prime contenders because they offer lots of space and many of the physical resources we’ll need right there—minerals and important gases locked up in ice or rock. Still, there’s a good chance that our first colonies beyond the atmosphere won’t be anchored to anything big and solid at all. They’ll probably be air-breathing environments floating free in the space between the planets. One of the five Lagrangian points, where the gravity of the Earth and the Moon are in balance, would be a good choice because once placed there, the colony would stay put. It would also be relatively close for purposes of supply, communication and, in the worst case, escape back to Earth.

Though we’ll probably place small-scale habitats in one of those spots to continue learning all we can about space living, I have a feeling that the first real colony of any size outside the Earth will be somewhere else. Like the center of a hollowed-out asteroid.

It just makes sense. We’ll be digging out the asteroid anyway, mining it for metals and anything else we can find. Depending on which rock we pick, it will probably have many of the valuable elements we’d find on a planet without the difficulties caused by planet-scale gravity. Plus man-made hollows inside a metallic rock will have plenty of natural radiation shielding. You can’t overestimate the importance of that outside Earth’s protective magnetic field. There would be drawbacks, though, including the great distance to the asteroids, the complete lack of gravity, and the difficulty of providing good lighting inside a rock.

In his inspirational book from the early 1990’s called The Millennial Project, Marshall T. Savage suggested that the best model for a space colony would be a clear giant bubble with smaller bubbles nested inside. Nice and simple. The outer bubble wall would actually be a double membrane with five meters’ thickness of water between the layers, which would allow sunlight through but block most harmful radiation. As with a hollow asteroid, though, there wouldn’t be any gravity, and we know that human muscles, bones, and organs quickly deteriorate without it. Savage believed this could be solved through a combination of electro-stimulation and exercise in special facilities spun at high speed to simulate gravity, but I have my doubts. A rigorous exercise routine helps the astronauts on the International Space Station, yet they still have to undergo months of rehabilitation when they return to Earth. Even if future space colonists never return to Earth, there are indications that microgravity over long periods of time will cause health problems.

Several concepts for space colonies are designed to spin to produce simulated gravity on their inner surfaces thanks to centripetal force (here’s a great page showing the most popular designs). The Stanford Torus is like a giant wheel, perhaps with one or more large mirrors placed nearby to reflect sunlight into the interior. In the movie Elysium the colony of this design had no roof, so shuttle craft could easily come and go. But there was no radiation protection at all, so it would only be feasible within the Earth’s magnetic field. With the Bernal Sphere concept, areas near the equator would have the highest gravity but it would weaken toward the poles, so there’d likely be a fat stripe of inhabited area with windows near one or both ends to let sunlight in. That’s a lot of mass to spin up considering so much of the surface territory would still have insufficient gravity. The O’Neill Cylinder might be the best design of the three: a large cylinder spinning on its long axis, with lengthwise sections of land area alternating with window strips to provide sunlight (actually O’Neill suggested pairs of cylinders close to each other rotating in opposite directions for reasons of physics I won’t get into here). Unless Scotty comes back from the future to give us the formula for transparent aluminum, like in the fourth Star Trek movie, the windows in the Bernal Sphere and O’Neill Cylinder would require a lot of glass or polymer, and all three of the above designs would probably still be deficient when it comes to radiation shielding.

Here’s my thought: What about using a giant bubble full of air of the kind suggested by Marshall T. Savage, but with an O’Neill cylinder spinning inside it? You’d get the radiation protection of the water (which would let you get away with thinner walls in the cylinder), lots of light, and the extra space in the bubble could be used for zero-g manufacturing and the growing of food crops that don’t mind microgravity. I realize that a wide-open wheel or cylinder wouldn’t work because of high-wind effects from the structure’s spin, but with sharply tapered ends and baffles to break up the flow of air, it should still be possible to come and go from the cylinder habitat into the rest of the bubble. Wind effects would also be less if we settled for something lower than full Earth gravity, thus allowing a slower rate of spin.

What do you think? Problems with friction effects? Static electricity? Give me your thoughts, I’d love to hear them.

It’s by playing around with such concepts that we’ll ultimately find the best solution.


Image from http://spacecolonization.wikia.com/wiki/O'Neill_Cylinder

Recent data sent by NASA’s MAVEN spacecraft is bad news for those who hope to someday open up Mars for human colonization.

We already knew that the Martian atmosphere is very thin (about 1% as dense as Earth’s at sea level). To make the Red Planet suitable for humans to live on we’ll have to drastically thicken the air and also heat it up. There were hopes that carbon dioxide, a greenhouse gas, could be freed from the soil and ice caps of Mars to produce a good atmosphere for trapping heat and feeding plants, which would then produce oxygen. It had been thought that much of Mars’ lost atmosphere had been absorbed into the soil, but the new MAVEN data (short for Mars Atmosphere and Volatile Evolution) suggests that most of that ancient atmosphere vanished into space, stripped away by the solar wind and solar explosions after Mars’ magnetic field died about four billion years ago. It’s gone and can’t be retrieved. That might not affect plans to build domed or underground cities on Mars, but terraforming the whole planet will be a lot harder.

Terraforming Mars was never a short-term project anyway, and the biggest drawbacks to colonies there include gravity and distance. We still don’t know if regular exercise and other methods will mitigate the potential health problems of living in a low gravity environment. And trying to build up the population of Martian colonies will require a lot of very long trips—about nine months one-way as technology stands, but that’s when Earth and Mars are in the right alignment, which only happens every couple of years. That’s a slow process. If our goals are to protect a sampling of the human race from potential disasters on Earth, ease population pressures on Earth, and make use of resources and manufacturing advantages that space provides, we’ll want something quicker.

If we build manufacturing complexes on the Moon, we can make the materials and air to build free-floating colonies in space, possibly in orbit around Earth or the Moon, but more likely where the gravity of the two bodies balances out at the so-called Lagrange points. That doesn’t mean that colonists would live in zero gravity (although they could get to it when they wanted to do a little recreational flying perhaps). One of the popular concepts is a gigantic rotating space wheel like in the movie Elysium that would produce artificial gravity on its inner surface from its rotation. The best-known example is called a Stanford Torus. But my preference would be a miles-long cylinder that would produce a gravity effect by spinning along its long axis. Its inner surface would alternate bands of habitable space with long windows to let in sunlight. In the 1970’s Gerard O’Neill proposed cylinders 32 kilometers long that would provide almost 1300 square kilometers of living space for several million people. Maybe my preference has to do with my love for the Arthur C. Clarke classic Rendezvous With Rama.

These colonies would avoid the concerns about low gravity and be close—only a few days travel from Earth. Research funded by NASA in the ’70’s said that such things could be built with the technology of the time, but materials, knowledge, and tech developed since then would make the job even more feasible.

So while I’m all in favour of Mars exploration for the sake of knowledge, I think the human race would be better served by focusing our colonization plans on free-floating near-Earth colonies or the Moon for the near future. If you think I’m off-base, let me know. Maybe you just have more patience than I do.

The good news this past week? NASA will accept applications from Dec. 14, 2015 through mid-February 2016 for their next class of astronaut candidates. Applications will be accepted at:

http://www.usajobs.gov . It’s only for U.S. citizens (unfortunately) but you could end up working on the International Space Station, a couple of spacecraft being produced by commercial companies, or even NASA’s Orion deep-space exploration vehicle.

The final frontier…but you know all that.