Reply #4: Helium-3

[Emperor_Norton_II]

aka 3He, is an isotope of helium that has only one neutron, as opposed to the more common helium-4 (which is what we commoners like to stick in our party balloons). The terrestrial supply is incredibly scarce, resulting mainly as a result of decay emissions from the nuclear arsenal. The Moon, however, has been picking up tons of 3He over the years from the solar wind, one atom at a time.

"Well, great," you say, "what's that got to do with anything?"

Well. It's useful for fusion reactors. In fact, it's the best possible fuel for fusion reactors available.

The fuel we're using for our test reactors now is deuterium (aka "heavy water", a hydrogen isotope) and tritium. We use the D/T mix because the components are abundant on Earth and thus fairly cheap to refine. Now, D/T works fine and provides lots of energy, but there's a catch. The way the reaction works, every D/T fusion that happens lets loose a stray neutron. These neutrons hit the walls of the reactor chamber, and bit by bit the whole apparatus slowly becomes irradiated. So every few years, you'd have to replace your main reactor and store the old one in the approrpiate place. Not very practical.

A reaction with deuterium and 3He, on the other hand, produces no spare neutrons. It's clean, almost perfectly so. All it produces is beautiful, radiant energy. That's what makes 3He such a prize catch. We don't have commercial reactors yet, but when we do (we're getting there btw, at this point the threshold isn't breakeven, it's ignition) whoever's got the fuel is going to get to dictate prices - like how OPEC controls oil prices.

And that's why the Russians are looking at the Moon. It's the closest source (though not the most abundant; whoever figures out how to mine the upper atmosphere of Saturn is going to make the Saudis look like stone pikers. But I digress.) and the one most likely to be developed.