some type of heat-cycle engine. After comparing assembly/transfer options, LEO has been identified as the best assembly location. A low orbit assembly station would be available by 1989, with a build-up to four stations by 2000; a GEO "depot" would be available, if required, by 1990. A subscale, assembly verification program is scheduled for 1984-85 (Ref. E9). The LEO assembly facility, according to Ref. E7, would include a "man habitat or hotel," power, docking space, tools, manipulators, control center; mobility units, and all elements necessary to provide the environment necessary for man to be productive in space. Structural elements, such as truss beams, would be brought to the assembly station in a collapsed state, and extension and installation would be accomplished on orbit. Completed SPS modules, utilizing a "self-powered" concept for orbital transfer to GEO, would "dock" with other modules already in GEO (Ref. A12). (3) Overall Considerations and Requirements The three overriding requirements for the construction in space of any SPS concept evident from all documents examined are: (a) Radiation protection in the Van Allen belts for radiation sensitive materials and for manned activities (b) Development of construction/assembly approaches for large structures (c) Development of automated, or robot/teleoperator construction mechanisms With respect to the first, i.e., radiation in the Van Allen belts, Ref. A9 (a NASA briefing), states that construction would involve a high degree of remotely controlled activity from a protected environment, and that EVA would be restricted to special requirements. Several other documents discuss this, but are not so emphatic about restricted EVA. The development of construction/assembly approaches involves a number of factors. Reference A9, for example, states there is less background in construction than in any other SPS area. Further efforts
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