The Energy Requirements and Feasibility of Off-World Mining

Space prospecting has been an enticing subject for more than half a century now and continues to capture the imaginations of extremely ambitious engineers and powerful capital allocators alike. It’s also somewhat viable: although most asteroids (and almost all of those that are considered to be “near-Earth”) have ore concentrations lower than those found terrestrially on Earth, there is a class of “metallic” (M-type) asteroids likely rich with platinum group metals (PGMs). In high demand, PGMs like Pd, Os, and Ir are difficult & pollutive to mine and thus are among the most expensive materials known to exist at >$500,000/kg.

Companies like AstroForge have recently raised millions on the business case for returning such metals prospected from asteroids, partly because of the enormous down mass potential (~20-50t) of SpaceX’s Starship. But the asteroid mining field is littered with bad ideas and failed projects. For one, Planetary Resources, a 2010s venture backed by Larry Page, thought it viable to extract volatiles from asteroids and robotically produce chemical fuel for in-space depots. Their money made it as far as a few test launches before running out and their assets acquired by a crypto company. It turns out it’s a bad idea to mine near-Earth asteroids for pretty much anything. Water is mixed in with rock and must be heated >400° C to use. Volatiles are not thermally stable and outgas in the vacuum. Metals are hit and miss. Asteroids are also more like piles of rubble, difficult to land on, and overall very small – so you’d want to land on quite a few. It turns out the moon is much better for mining, but it's still going to be tough.