Mining the Moon for Helium-3 Aneutronic Fusion Energy

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• published: 15 Nov 2013
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An educational movie from the early 90's explaining how lunar mining of the Helium-3 isotope (along with water and other gases) from lunar regolith could be accomplished. Helium-3 is a fuel source for an aneutronic fusion reaction with deuterium, which releases no harmful neutrons decreasing the hazard of nuclear fusion considerably. Deuterium is common on the earth, (158 ppm in seawater), however Helium-3 is scarce on the Earth and can only be made by nuclear fission in small amounts. 4 Billion years of solar wind bombardment has left lunar soil one of the richest sources in the solar system of Helium-3, although the gas giant planets such as Jupiter and Saturn are richer, having absorbed more Helium-3 from the nebula that formed the solar system. Titanium dioxide, TiO2, is one of the key components of lunar soil and rock, has the largest capture cross-section for helium-3 and can trap and contain the gas for billions of years, allowing it to build up in high concentrations. High resolution mapping of TiO2 abundances on the Moon, which was done using the Hubble Space Telescope in 2007, may be an important tool for locating ideal mining sites. Moreover, the far, or "dark", side of the moon is particularly rich in Helium-3 as this side of the moon always faces away from the earth meaning that it has had a steady buildup of the stable He-3 isotope for 4 billion years. The near side also has significant quantities, however it is decreased as the earth's magnetic field and the earth itself would have decreased the particle flux from the sun reaching the moon. Hence, people who appreciate the moon for its natural beauty need not panic as it may be convenient to mine the far side of the moon if we chose to mine it at all, leaving the natural beauty of the near side alone. As we never see the far side, it will be unnoticeable from the earth that we are mining the moon at all as will not have to make track lines over any any natural features of the moon as seen from earth. Even so it would take thousands of years to make any significant changes to the moon. Craters could even be swept of external regolith and smoothed to make giant radio telescopes, as the Earth's radio noise and atmosphere make certain radio frequencies inaccessible from earth-based observatories but this would not be a problem on the far side of the moon. Optical observatories could also be built on the moon to sizes and resolutions impossible to achieve on earth and even on earth orbit, as the low gravity, lack of atmosphere and lack of glare from light reflected off the earth itself would mean giant, stable mirrors could be built and observe a truly dark and clear sky. Moreover the deepest craters are found on the far side of the moon. Since water can only be found in significant quantities on the moon in deep craters where it can remain semi stable inside of rocks most of the water may be on the far side of the moon, or at least at the poles, embedded in the lunar soil in such craters. Therefore the economic and scientific centers of the moon may be on the side which never faces the earth! Earth's supplies of Helium-3, a substance with a net worth of $3 Billion per metric ton (over 80 times more valuable than gold) are dwindling rapidly, with sources now 6 times less than in the 1980's. Lunar soil has rich deposits of Helium-3, which would not only pay for the trip expenses but would also allow the nation(s) that go for it to dominate the Moon and make series headway to Mars, having a lower gravity to launch from. NASA should be seriously considering lunar mining as Helium-3 can not only be used in advanced physics experiments, such as neutron spin polarization spectroscopy for characterizing new materials such as superconductors but can also be used in MRI scans for observing lung cancer and most importantly generating a clean form of nuclear fusion, known as aneutronic fusion. Helium-3 can be created on the earth as a decay product of Hydrogen-3 (Tritium) or when Lithium is bombarded with neutrons under certain cross-sections. At a price of 3 billion US dollars per tonne, mining the moon for this resource is highly economical. About 20 tonnes of helium-3, which would fill a single oil truck, would power the US for a whole year. Aside from a fuel source for fusion, Helium-3 is also used in neutron spin polarization spectroscopy which measures the magnetic properties of nanomaterials, such as superconductors. This is due to unique spin-dependent absorption cross-section of Helium-3. The isotope is also used in cryogenics to achieve nanokelvin temperatures in dilution refrigerators making it an crucial material for science and industry. Helium-3 reserves are critically low worldwide and unless there are efforts by the nuclear industry on earth to replenish them by producing more tritium then the moon seems to be the best option economically to harvest this precious resource.