Space Station Freedom. Freedom, which is planned to be the largest object yet put in orbit, will take NASA several years to construct. After analyzing deployable and erectable technologies with regard to large space structures, we conclude that the assembly and maintenance of solar power satellites will be of sufficient complexity to absolutely require an assembly and maintenance oriented demonstration before any system of solar power satellites can be installed. The primary purpose of this last prototype would be to show not only the ability to build the solar power satellite, but also the related but yet quite different ability to maintain it, for a period of about 5 years (based upon a desired 30- year satellite lifetime). In addition, many experiments of deployable and erectable technologies need to be performed. These can range from small scale demonstrations, like the proposed Earth to space design example that plans to use an inflatable rectenna, to larger scale experiments such as the proposed 1 MW design example, which requires manned assembly, and SPS-2000, which the Institute for Space and Astronautical Science (ISAS) of Japan plans to assemble telerobotically. Using the figure of 20,000 tonnes per GW for solar power satellite mentioned earlier, this means that one solar power satellite will have a mass of 100,000 tonnes. To put this truly tremendous amount of material into perspective, one has to realize that since the launch of Sputnik 1 in 1957, only 30,000 tonnes of payload have been placed in orbit. Also consider that if a few solar power satellites are constructed simultaneously, then both global launch rates need to increase and launch costs need to decrease by at least two orders of magnitude. Furthermore, it will have to be shown that the environmental effects of this greatly increased launch rate are minimal. Because of these assorted potential technical, financial, and environmental “showstoppers” to the building of large solar power satellites with only terrestrial materials, the use of nonterrestrial resources for space solar power has been seriously considered. Contemporaneous to the NASA/DOE studies, Gerard K. O'Neill, to whom this report is dedicated, first proposed the use of lunar materials for the construction of solar power satellites. O'Neill argued that the raw materials needed for construction of these satellites could be delivered to GEO from the lunar surface at one-twentieth the transport cost of their delivery from the Earth. This argument is based on both the Moon's substantially lower gravity well and its lack of an atmosphere, which allows the use of electromagnetic launchers called mass drivers, whose viability O'Neill also helped demonstrate. This argument, though, overlooks the problem of establishing the necessary cislunar infrastructure and the required orbital manufacturing facilities. But after examining lunar resources, and comparing them to other nonterrestrial resource options like asteroidal materials and such objects as Shuttle External Tanks and Energia Cores, we conclude that the Moon is of particular significance to space solar power and is in fact another “high leverage” issue (see Section I). The establishment of a lunar base constitutes a high-leverage issue because a lunar base represents not only a future supply of resources for satellite construction, but also a potential market for beamed power. This concept is actually the synthesis of two of O'Neill's ideas: lunar-derived solar power satellites and “bootstrapping.” Space solar power systems can benefit from “bootstrapping” by initially providing beamed power to a lunar base, which in turn could provide the system with the materials needed to build more solar power satellites. This power could be implemented in a staged way by first providing kilowatts of energy to a lunar rover from lunar orbit, and subsequently providing up to the approximately 1 MW required by a manned lunar base. A preliminary analysis of a lunar rover demonstration suggests that it might be feasible for approximately US $1 Billion. Considering the dearth of near-term Earth-based markets, beaming power to the lunar surface may be the best way to convincingly demonstrate space solar power while simultaneously enhancing its longterm economic viability
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