The Myth and Reality of Space Mining: Challenges and Limitations
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From Ellen Ripley in Alien and Dave Lister in Red Dwarf, to Sam Bell in Moon and Naomi Nagata in The Expanse, the grittier end of interstellar drama always involves aproned engineers and their mineral-processing operations. Space mining is such an alluring idea that real money has been invested in it. Alphabet’s Larry Page and Eric Schmidt, and Hollywood filmmaker James Cameron, all invested in Planetary Resources Inc., which raised venture finance with its mission of mining high-value minerals from asteroids, which have almost no gravity when compared to a planet, and refining those minerals into metal foams that could be shot back down to Earth. Deep Space Industries Inc., a rival startup, also had bold plans to exploit asteroids and comets. Though both companies have now been bought out and their projects put into mothballs, the idea of a space mining industry refuses to die.
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It’s wonderful that people are shooting for the stars — but doubters were right about the fundamentals. Space mining won’t get off the ground in any foreseeable future. Gravity is the factor that rules out most space mining at the outset. Escaping Earth’s gravitational field makes transporting the stuff needed in a mining operation hugely expensive. On Falcon Heavy, the large rocket being developed by Elon Musk’s SpaceX, transporting a payload to the orbit of Mars comes to as little as $5,357 per kilogram — a drastic reduction in normal launch costs. Still, at those prices just lofting a single half-ton drilling rig to the asteroid belt would use up the annual exploration budget of a small mining company.
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Power is another issue. The international space station, with 35,000 square feet of solar arrays, generates up to 120 kilowatts of electricity. That drill would need a similar-sized power plant — and most mining companies operate multiple rigs at a time. Power demands rise drastically once you move from exploration drilling to mining and processing. Bringing material back to Earth would raise the costs even higher, albeit by a small multiplier. Japan’s Hayabusa2 satellite spent six years and 16.4 billion yen ($157 million) recovering a single gram of material from the asteroid Ryugu and returning it to Earth earlier this month. What might you want to mine in space? Water has potential as raw material for hydrogen-oxygen fuel that could be used for a return journey to earth. The discovery in October of ice molecules in craters on the Moon intrigued many. But the concentrations of 100 to 412 parts per million are extraordinarily low by terrestrial standards. It is the same with copper wherever its deposits are evidenced.
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The more promising commodities are platinum, palladium, gold and a handful of rare related metals. Because of their affinity for iron, these so-called siderophile elements mostly sunk toward the metallic core of our planet early in its history, and are relatively scarce in the Earth’s crust. Estimates of their abundance on some asteroids, such as the enigmatic Psyche 16 beyond the orbit of Mars, suggest concentrations several times higher than can be found in terrestrial mines. Still, human ingenuity is all about cutting our coat according to our cloth. If such platinum-group metals are going to justify the literally astronomical costs of space mining, they’ll need to count on sustained high prices for the decade or so that would be needed to get such an operation up and to keep it running — and that sort of situation is all but unheard-of in the materials industry.
