summer of 1988), with the selection of a lunar base to mine and transport materials for solar power satellite construction as a student design project [22]. Now that the space community is more familiar with the idea of nonterrestrial resource utilization for large-scale space projects, a review of nonterrestrial materials for solar power satellites is in order. The General Dynamics study [14] compared four different scenarios for SPS construction (Table I). The baseline scenario, with all construction materials lifted from Earth’s surface, was compared with three nonterrestrial scenarios (Fig. 2). The first nonterrestrial scenario considered use of an electromagnetic mass-driver to launch lunar soil packets to L2. The remaining two scenarios used lunar materials launched with chemical rockets, which used lunar oxygen and either Earth-imported hydrogen or lunar aluminum as propellant. The report concluded that the scenario which utilized electromagnetic launching from the Moon resulted in the lowest construction costs and minimized Earth launching to the greatest degree (Fig. 3). One of the underlying assumptions of the study was that the fundamental solar power satellite design would be the same as that for the strawman Earth-launched design, but allowing substitutions to take advantage of lunar material properties. If lunar resources were used for solar power satellite construction, these satellites would be designed from the beginning with this in mind. Therefore, the SSI set out in 1984 to design an SPS optimized for lunar materials utilization. Under contract to SSI, Space Research Associates (SRA) of Seattle, WA, designed a silicon planar solar power satellite which was comprised of over 99% lunar materials (Fig. 4). The total mass of this SPS was 8% greater than that of the Earth-Launched strawman satellite. The earth launched mass would be approximately 3% of that of an Earth launched system [23, 24]. The SSI/SRA design was primarily made up of an aluminum structure, although the possibility of using composite materials was raised. Initial studies of solar power satellite construction from lunar materials have generally assumed that any element available in relative abundance on the lunar surface can be extracted from the soil at reasonable expense. Techniques such as the HF acid leach process, studied by Robert Waldron of Rockwell International under contract to SSI [25], can, in fact, provide a wide range of pure elements from lunar soil. However, in recent years the SSI has focused on an examination of relatively
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