One of the most beloved yet puzzling books everyone reads in high school English class is The Little Prince by French writer, poet and aviator Antoine de Saint-Exupéry. The little prince with the golden hair came from the house-sized asteroid "B 612" where he tended to plants and three tiny volcanoes. While English teachers focus on the puzzling ending and force students to write endless essays on whether the Little Prince survived or died, science and astronomy teachers should have borrowed the book on the day they discussed gravity and asked their students to determine what would really have happened to the Little Prince on his little asteroid – would he have lived or floated off into space. Researchers planning to mine asteroids for the expected treasure troves of rare and precious minerals it's believed they hold (the plot for thriller movies rather than English class novels) have the answer, which is why (spoiler alert) they’re planning to build a space station INSIDE an asteroid.
“In this study we present how to estimate the necessary spin rate assuming a cylindrical space station inside a mined asteroid and discuss the implications arising from substantial material stress given the required rotation rate. We estimate the required material strength using two relatively simple analytical models and apply them to fictitious, yet realistic rocky near-Earth asteroids.”
Thomas Maindl, an astronomer at the University of Vienna, led the study which was published but not yet peer-reviewed in arXiv. The need for an internal rather than surface asteroid station stems from the ideas that asteroids have insufficient gravity to hold a mining station and even if one did, the lack of an atmosphere and magnetic field would expose workers to deadly radiation. The math behind the proposal certainly makes it feasible – Maindl estimates that a solid stone asteroid at least a few hundred meters in diameter rotating at a very fast rate of one to three times per minute would create sufficient sub-surface gravity to allow miners and mining tools to safely hammer out minerals in a gravity similar to Mars or about one-third that of Earth. The asteroid would need to be larger than the Little Prince’s house-sixed B 612 to keep it together as the space for the station was drilled out and the severe hammering caused asteroid-quakes far stronger than B 612’s little volcanic eruptions.
The proposal makes sense but, as David Letterman liked to ask, will it float?
“The border between science and science fiction here is sort of blurry.”
That’s not exactly a vote of confidence, Dr Maindl. Spacecrafts that have landed on asteroids to date are often tiny rovers designed for bouncing in extremely low gravity. That’s how Osiris-Rex is expected to pick up rocks and dust on Bennu later this year before returning to Earth. But that’s not the kind of mining the greedy minds of industry have in mind as they learn more about the mineral riches many asteroids hold. While Maindl estimates that it could be decades before a mission to build a space mining operation inside an asteroid takes place. Big business will no doubt push for much sooner. Who needs space hotels when there’s gold and diamonds to be dug up?
What would the Little Prince say?
“You become responsible, forever, for what you have tamed.”