baudrunner's space: The potential of helium-3 (He-3)
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Tuesday, October 21, 2008

The potential of helium-3 (He-3)

Helium 3 (He-3) nuclei contain 2 protons and 1 neutron, unlike regular helium (He-4) nuclei, which contain 2 protons and 2 neutrons. He-3 is a light, non-radioactive isotope of helium and is very rare on the Earth, but relatively abundant on the moon, which is why the moon is being eyed as a tempting source of He-3 for fueling fusion reactions using deuterium here on Earth. Helium 3 can be extracted from the lunar dust by heating it to about 600ยบ C.

In the He-3-deuterium type of fusion reaction, He-3 readily grabs a neutron from the Deuterium atom when the two are subjected to extreme temperatures. This yields a proton and He-4. This is a strongly exothermic reaction, with the net loss of mass in the conversion given off as energy.

Extracting He-3 from the moon is not a preposterous notion. UR Rao, a former director of the Indian Space Research Organisation (Isro) has suggested that the moon might have "enough He-3 to produce energy for 8,000 years". China’s head of its Lunar Exploration Project (CLEP), or Chang’e project, has said that "each year three space shuttle missions could bring enough He-3 for all human beings across the world".

1 kg of helium-3 burned with 0.67 kg of deuterium yields about 19 megawatt-years of energy output. The space shuttle is capable of carrying about 25 tonnes of payload. That would represent enough Helium 3 to power the U.S. for one year at current energy consumption rates. Moreover, He-3 fusion reactors are safe. It actually makes sense to consider extracting He-3 from the lunar surface as a viable alternative energy project. Let the competition begin.

Just one rather sticky problem. No working fusion reactor has yet been built.

However, the serious enthusiasm which the scientific world has generated with respect to the generation of electrical energy from a safe and efficient source of fusion power is reflected in the ITER project, “a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power”. Thus far, over $12 Billion has been invested in this enterprise, with the intention of proving that the generation of energy from fusion reactions is possible.

ITER deuterium-tritium fusion reactor

The fusion reaction created by ITER is a deuterium-tritium reaction. Tritium is a radioactive isotope of hydrogen. Its nucleus contains one proton and two neutrons. Decades of research into controlled hydrogen fusion reactions have yielded no return on investment in the way of energy, just knowledge.

Abundant supplies of He-3 are needed before research into the construction of a deuterium-He-3 fusion reactor can begin. Some catch-22. *sigh*

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