Moon Mining: Just a Fantasy?

Lunar enthusiasts have advocated mining helium-3 on the moon as a potential source of energy. How realistic is this? According to an interesting article in Technology Review, these lunar plans may not be loony, but perhaps a bit unrealistic.

In the August issue of Physics World, theoretical physicist Frank Close, at Oxford in the UK, has published an article called "Fears Over Factoids*" in which, among other things, he summarizes some claims of the "helium aficionados," then dismisses those claims as essentially fantasy. *

*Close points out that in a tokamak--a machine that generates a doughnut-shaped magnetic field to confine the superheated plasmas necessary for fusion--deuterium reacts up to 100 times more slowly with helium-3 than it does with tritium. In a plasma contained in a tokamak, Close stresses, all the nuclei in the fuel get mixed together, so what's most probable is that two deuterium nuclei will rapidly fuse and produce a tritium nucleus and proton. That tritium, in turn, will likely fuse with deuterium and finally yield one helium-4 atom and a neutron. In short, Close says, if helium-3 is mined from the moon and brought to Earth, in a standard tokamak the final result will still be deuterium-tritium fusion. *

Second, Close rejects the claim that two helium-3 nuclei could realistically be made to fuse with each other to produce deuterium, an alpha particle and energy. That reaction occurs even more slowly than deuterium-tritium fusion, and the fuel would have to be heated to impractically high temperatures--six times the heat of the sun's interior, by some calculations--that would be beyond the reach of any tokamak. Hence, Close concludes, "the lunar-helium-3 story is, to my mind, moonshine."

Then again, as the article also points out, current earth-bound fusion projects, such as ITER, aren't exactly on the verge of providing useful energy either*.*

[High Five: RC]