Living Inside Asteroids

For humans to live long-term in space we would need a healthy environment. This would mean somewhere spacious, with plenty of the comforts we find on Earth. And most importantly, we would need gravity, or at least a simulation of it.

Large space stations could be built with all of the above. With a large enough diameter they could be spun at less than two revolutions per minute, which would eliminate the uncomfortable symptoms of the Coriolis effect that would be experienced at the higher revolutions of a small rotating space station. Due to the huge amounts of material needed for construction of such stations, and the immense cost of launching it from Earth, the materials to construct the space stations would realistically have to be mined from asteroids.

A large diameter space station under construction in the Asteroid Belt. A single large asteroid will provide more than enough material for the construction of the station. Concept by Deep Space Industries.

Asteroid mining will not only provide the huge amount of construction material necessary for space habitats. If the asteroids are mined in a certain way, making large cylindrical chambers through the asteroid's centre of rotation, we could then convert the chambers into living spaces. Once mining is concluded the rotation of the asteroid could be altered until a high-enough centrifugal force provides enough artificial gravity comfortable for humans on the chambers' outer walls.

Such chambers, several kilometres in diameter, could well provide what may become the safest and most comfortable human living spaces away from the Earth.

Of course, the idea of hollowing out space inside an asteroid is not a new one.

This image was created in the 1960s by Roy Scarfo when the exploration and colonisation of the asteroid belt was being researched by Dandridge M Cole.

In the 1960s Dandridge M Cole, an aerospace engineer and futurist, was one of the first to propose hollowing out an asteroid and spinning it on its long axis to simulate gravity. Illustrated above, he envisaged a large single void within the asteroid with fields, lakes and villages. Sunlight would be reflected into the interior using mirrors. It would be a spacious and comfortable environment.

It's an impressive concept, but there are numerous problems with it, and not least the idea of a single huge chamber and relatively thin wall. It would make the asteroid habitat vulnerable to complete decompression if the wall was compromised in some way. If the rotation provided one gee of gravity the forces on the wall, especially at the asteroid's equator, would cause it to fly apart as soon as any cracks or flaws developed.

The very green and pleasant interior of Dandridge's asteroid habitat concept

It would be far better to cut several cylindrical voids, and have the outer walls very thick - several kilometres at least, depending on the overall size of the asteroid. Each chamber would be connected to the next, but with the ability to quickly seal off a particular chamber if it was compromised and at risk of decompression, or indeed some other dangerous event. Those living in the effected chamber could easily be evacuated to another chamber, making such asteroid habitats safe and with plenty of redundancy.

Once the chambers have been excavated the asteroid's speed of rotation can be increased slowly, until the right level of simulated gravity is reached. To generate an equivalent of one gee (the same as what we experience on Earth) the rotation speed would be quite substantial, and it would mean that, at the very least, loose boulders and dust would be thrown off the surface of the asteroid. It would also put considerable stress on the outer surface, which would rule out low density asteroids due to the high risk of instability.

A natural habitat for Earth life, many kilometres in diameter, created inside a hollowed out cylindrical chamber within an asteroid. Typically there would be a few such chambers. All would be linked but each could be sealed off should a disaster occur, which would protect the other chambers.

A supporting series of collars around the equatorial region of of the asteroid would negate many of the issues that such a high centripetal force would cause. It would be a huge construction task to build such collars, but no more than the excavation of the chambers themselves. Of course, the excavated material would provide everything required to build the collars, each of which could be many kilometres in width. They would be held in place by deep supports.

Visiting spacecraft would using large docking areas at the poles of the asteroid, situated at each end of the axis of rotation. People and cargo would then be transported through the asteroid along the axis of rotation. Essentially there would be zero gravity in this area. When the destination chamber is reached the visitors and cargo would be delivered to the surface using elevators. People descending in these would experience a steadily increasing sensation of weight as they approached the surface.

A diagram showing how the interior of a rotating asteroid colony could be divided up into separate chambers. This would provide higher levels of safety (colonists could be evacuated to another chamber if their own is compromised), and more structural integrity than a single large chamber.

It's likely that people arriving at the asteroid will have spent many months travelling in zero gravity so acclimatisation areas at the regular points down to the surface should be built to allow people to adapt gently to the full gravity of the facility.

As well as fairly static colonies inside asteroids in the Asteroid Belt, or in the Trojans, asteroids that are on highly elliptical orbits - that head in to the inner Solar-System and then out beyond the orbits of Neptune and Uranus - would make very useful passenger ships. As the asteroid gets close to Earth (and the probable large colonies on the Moon and Mars) passengers who need to travel to the outer Solar-System could rendezvous with it. They could then spend the next couple of years living in comfort in relatively Earth-like conditions as the asteroid's orbit takes them closer to their destination.

Ultimately, such asteroids could become our first interstellar star ships. They would make voyages lasting thousands of years, with a hundred generations or more of humans living out their lives in comfort until the asteroid is captured by the target star system. With the right energy generation technology such as nuclear fusion that could provide light and warmth during the interstellar period of the voyage, humans would have a relatively good chance of reaching their destination.

Converting asteroids into large human habitats, and then into interplanetary and interstellar spacecraft, seems to be a logical and necessary step as humans embark on colonisation beyond Earth, and it is likely to be an essential step towards securing the future of our species.

The vast resources and protection that such objects can provide must be utilised at the earliest opportunity.