“Conventional” nuclear fusion reactors work by fusing deuterium and tritium to produce helium-4, a neutron and enormous heat and radiation. The heat is used to boil water and the resulting steam drives a turbine.

Several experimental nuclear fusion reactors based on this principle have been built but none has yet produced more power than it has consumed. The project leading the effort to produce commercial fusion power is the ITER project by an international consortium led by the European Union and based in Cadarache in southern France. The ITER project anticipates its first net power generation will be by 2038 with a commercial power plant by 2050.

The difficulty with these reactors is containing the heat and radiation which they produce. In effect, what they are trying to do is explode a hydrogen bomb, contain the radiation and capture the heat in order to boil water.

An alternative fusion process is based on helium-3 (He-3). When He-3 is fused, it produces a stream of protons and very little heat or radiation. An alternative process fuses helium-3 with deuterium. This produces helium-4 and a stream of protons.

The stream of protons from He-3 fusion can be used to generate electricity directly with no need to generate steam – a much safer and more straightforward process than deuterium-tritium fusion. And very little He-3 is needed – 25 tons would be sufficient to supply all of the United States’ energy needs for a year.

The problem with helium-3 fusion is that He-3 is rare on Earth, although common on the Moon and elsewhere. He-3 is produced when solar radiation strikes a planet’s surface. But the Earth’s atmosphere protects it from this radiation. On the other hand, there is enough He-3 on the Moon to supply the Earth’s energy needs for thousands of years.

While the idea of mining the Moon may seem far-fetched, it is being taken very seriously because such a small amount is needed – three space shuttle loads a year would be sufficient to meet all of the Earth’s energy needs.

India has stated that the primary purpose of its space programs, which launched its first lunar mission this month (October 2008), is to map the He-3 resources of the Moon and investigate ways of exploiting them. China has also stated that one of the main aims of its space program is to explore the possibility of obtaining He-3 from the Moon. Russia, the European Union and possibly Japan are all also believed to be developing programs aimed at exploiting lunar helium-3.

(Based on sources including space.com, Wired magazine and Wikipedia)