Mining lunar Helium-3

The desire for helium-3 fusion energy is a noble one, but the figures let such dreamers down. You would have to excavate a volume of regolith kilometres long on each side and ten centimetres deep. All this material would have to be heated to about 700°C, causing the helium and all other volatiles to be released. If you could process a tonne every minute, it would take at least 150 days. Then you would have to separate the helium-3 from the far more abundant helium-4. (You would get 1 kilogram of helium-3 for every 2500 kilograms of helium-4.) This could be achieved by cooling it to very low temperatures, where it will fractionate because the two isotopes have different boiling points. In the process nitrogen, hydrogen, and carbon would be released, which would be very useful for a lunar colony. Given all this, exploiting helium-3 is a long way off and certainly not something that will happen within the next 50 years. But if we do ultimately achieve it, lunar helium-3 could power human civilisation at its current level of energy consumption for about a thousand years.

- David Whitehouse, Space 2069: After Apollo - Back to the Moon, to Mars, and Beyond, London, 2020, p.92

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Blog: When We Left Earth, 26 October 2009