Last Christmas, inspired by Randall Munroe’s delightful books What If? and What If? 2, I invited the good folk of Twitter to ask me absurd hypothetical questions about the economy, to which I would attempt some serious answers. This year, we’re going to do it all again.
Alex asks: How big would an asteroid made of precious metal have to be for it to be worth doing a space mission to bring it back?To answer this question I consulted Soonish, a book by Kelly and Zach Weinersmith, which devotes a chapter to the problem. Some asteroids have much higher concentrations of metal than are typical near the surface of earth, and a decent-sized golden asteroid does sound tempting.
Alas, there are three problems: physics, engineering and economics. Engineering first. If you want to mine an asteroid, you either need to set up a refinery in space (difficult) or send huge amounts of unrefined ore back through the atmosphere to be refined back on Earth (messy).