[LINK] "Moonshine"

[rfmcdonald]

Charlie Stross tackles the idea that helium-3--an isotope of helium that supposedly will be good fuel for fusion reactors and, by virtue of its concentration on the lunar surface, could support space colonization--could, well, support space colonization.

Firstly, nobody's built a commercially successful fusion reactor yet. ITER plan to build a working test-bed; it's logical successor would be a working prototype first generation power reactor. There are huge obstacles to overcome, not least in developing neutron capture techniques and breeding D/T fuel; but there are gigantic engineering problems to overcome (sorry, annoying paywall). And that's before we look to a speculative second generation reactor, running on a different type of fuel, that — because of the higher Coulomb barrier between He nuclei — requires a far higher temperature (on the order of 500M to 1Bn degrees celsius, rather than the relatively chilly 100M degrees C required for D/T fusion).

Given the average generation time for a new reactor technology of 20-30 years, we won't be even thinking about prototyping an He3 reactor until 2060 at the earliest.

Secondly, there's very little He 3 in the lunar regolith. The amount is non-zero, but we can also breed the stuff on Earth: Neutron bombardment of Lithium, Boron, or Nitrogen targets, or decay of Tritium are currently used. Breeding He 3 requires a high neutron flux, but unless the plan is to automagically shift us all over to a "clean" He 3 power cycle instantly, He 3 reactors will be coexisting with "dirty" high-flux fission or fusion reactors for many decades.

Is it really going to be cheaper to send monster trucks to the moon, than to build a couple of special-purpose high neutron flux reactors optimized for mass production of Tritium (and thereby for production of He3 as a decay product)?

He suggests that the fixation on helium-3--something I've blogged about in the past--as a way to pay for space colonization, to make it an economic endeavour as opposed to an ideological one, can't end well. I wonder: What economic incentive could work for space colonization?