[BRIEF NOTE] On the decline of the #Moon re: #helium-3 mining

[rfmcdonald]

I've frequently frequently written about the false mirage of helium-3 mining on the Moon. Helium-3, a light isotope of helium seen by proponents as an ideal fuel for nuclear fusion reactors, is present in abundance on the Moon. Proponents of space colonization have suggested that mining helium-3 from the lunar surface would provide the income necessary to support lunar settlement. This would be the case if, in fact, the massive investments in technology and infrastructure necessary to create a lunar helium-3 mining infrastructure and second-generation fusion reactors capable of enduring the intense heat would be economic (keep in mind that we don't have first-generation fusion reactors), and that there wasn't already plenty of helium-3 on Earth.

Over at Centauri Dreams, Paul Gilster made a post--"Starship Fuel from the Outer System" that james_nicoll read at about the same time that I did ("Slowly winning the war" is the title of his post). What's the war in question? (Note that the bold print is mine.)

Adam Crowl is a frequent Centauri Dreams contributor, but he’s also deep in the Project Icarus effort [to build an nterstellar probe], serving as its module lead for fuel and fuel acquisition. And fuel is the heart of the problem. Deuterium (hydrogen with an added neutron) and the isotope of helium known as helium-3 (containing one less neutron than helium-4, or regular helium) create the kind of reaction Icarus needs. The method is preferable to the fusion of deuterium with tritium because the latter releases about 80 percent of the fusion energy in the form of high-energy neutrons. To avoid that kind of heat transfer to the engine, the original Project Daedalus team focused on deuterium/helium-3, which continues to be the method of choice for the Icarus designers.

But where to get the helium-3, which is found only in tiny amounts on our own planet? You might think the Moon would be useful, given that the solar wind has deposited perhaps as much as 2.5 million tons of the stuff in the lunar regolith. But Icarus has had a long look at lunar mining, and finds that the energy needed to extract it would be greater than what it would eventually produce. That leads us back to the gas giants — Project Daedalus focused on Jupiter for helium-3 extraction, conceiving of a giant mining operation using floating factories in the atmosphere.

But Uranus may be the better choice, and that leads to quite an interesting infrastructure.

Mind, the idea of mining the gas giants of the outer Solar System may or may not economic. (I've no idea myself, and am waiting for someone to come up with the calculations.) If there is going to be a push for space colonization, the push should be based not on disproved economic dreams.