Asteroid miners might be best off working inside-out.聽A new analysis suggest we could place a space station inside a rotating asteroid to provide simulated gravity for the mining equipment.
The past few years have seen an increased interest in mining asteroids. The idea is to send probes聽to distant space rocks, remove chunks of resources like precious metals, and bring them back to Earth or use them to build in space.
One major problem is that you can鈥檛 just jackhammer an asteroid: most of them have such weak gravity that a hammer or digger is likely to just bounce off into space.
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Thomas Maindl and his colleagues at the University of Vienna in Austria have come up with a potential solution. If you put a space station inside a rotating asteroid, the spinning would create artificial gravity while also protecting the mining rig from the dangers of the space environment on the asteroid鈥檚 surface, particularly radiation.
Round and round
The team modelled their space station as a cylinder inside a round asteroid that was a few hundred metres wide. Depending on the particular asteroid, this could be anything from聽a craft聽like the International Space Station to just a cavern cut out of the rock. 鈥淚f we find an asteroid that鈥檚 stable enough, we might not need these aluminium walls or anything, you might just be able to use the entire asteroid as a space station,鈥� says Maindl.
They assumed that the asteroid was made of solid stone, and that the space station would require 38 per cent of Earth鈥檚 gravity, which is about as much as we would experience on the Martian surface. That would be enough to allow asteroid mining astronauts or robots to orient themselves and stay upright.
The asteroid would have to be rotating about one to three times per minute to create the necessary centrifugal force, the researchers found. All this spinning would create stress on the asteroid, risking the whole thing flying apart, but聽Maindl and his team calculated that聽solid rock should be strong enough to hold together.
Cracks in the foundation
That doesn鈥檛 mean we could just turn any asteroid into a space station. We would need a lot of information about a particular space rock聽before we could be confident that putting a space station inside wouldn鈥檛 crack it apart.
鈥淲e do not know physical characteristics of the vast majority of objects in this size range,鈥� says Peter Vere拧 at the International Astronomical Union鈥檚 Minor Planet Center, which tracks asteroids. From what little information we do have, it seems like many of them are probably floating piles of rubble rather than single huge boulders, he says.
And even if the asteroid starts out structurally sound, digging a cavern for the space station and then continuing to excavate material could make it more likely to fall apart. Constantly changing the asteroid鈥檚 mass distribution by mining would make it hard to maintain a constant spin rate, too.
鈥淭here are challenges to keeping it spinning that way,鈥� says Haym Benaroya at Rutgers University in New Jersey. 鈥淎s people or robots were working inside and moving around, that could destabilise the rotation.鈥�
Overall, Benaroya says, while the idea might be possible for a small population of asteroids, it isn鈥檛 the easiest way to mine an asteroid 鈥� an industry that itself is probably decades from becoming real.
鈥淭he border between science and science fiction here is sort of blurry,鈥� says Maindl. 鈥淢y gut feeling is that it will be at least 20 years before any asteroid mining happens, let alone something like this.鈥�
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