• Seth D Potter

One of the major constraints on the eventual deployment of solar power satellites (SPS's) is the cost of launching large amounts of material into space. Two research strategies have been pursued in order to circumvent this problem. One approach, supported by SSI for many years, is to build the SPS's out of non-terrestrial (particularly lunar) material. The March/April 1993 issue of Update contained an excerpt from Dr. Gerard K. O'Neill's book Technology Edge: Opportunities for America in World Competition, in which he points out that launching a given amount of material from the Moon to high orbit takes less than a twentieth as much energy as launching the same amount of material from the Earth. When other factors, such as atmospheric resistance on the Earth, are accounted for, the savings in launch costs from the Moon versus the Earth may amount to a factor of fifty. In 1985, Space Research Associates completed an SSI-commissioned study, in which the NASA/Department of Energy reference SPS was redesigned to take full advantage of lunar resources . It was shown that approximately 99% of an SPS can consist of lunar materials. The 8% increase in overall mass compared to an SPS built from terrestrial materials was considered to be a relatively small price to pay for this advantage.