will stationkeep at least 1 km away, while special cargo tugs transfer material pallets. GEO base crews will, of course, also be rotated as needed. At the end of the second pass, the base is then indexed sideward to mate the antenna with the center line of the energy conversion system. After final test and check out, the base separates from the satellite and is transferred to the next orbital position for SPS construction. The reference scenario requires that one 5 GW satellite is to be constructed every six months for 30 years. In order to carry out this program, nearly 450 space workers would be needed on two daily shifts (10 hours each) to perform construction, base support, maintenance, safety and base management operat i ons. BASE CONSTRUCTION SYSTEM The end builder construction system described above uses ten synchronized beam machines to automatically fabricate continuous longitudinal beams for the energy conversion system. Lateral and diagonal members of the structural assembly are fabricated with three mobile beam builder substations. The assembly sequence, as shown in Fig. 3, begins with assembly of the first end frame and its attachment to the longitudinal members. This frame is automatically indexed away as the synchronized beam builders fabricate the required length of longitudinal beam to complete the structural.bay. During these operations, solar array blankets and power busses are installed in parallel. For example, Fig. 4 shows how the solar array blankets might be temporarily anchored to the base so that they can be automatically deployed during longitudinal beam building operations. The illustration also shows two cherry pickers prepared to handle and connect opposite ends of a 667.5 m solar array support beam to the SPS frame after it emerges from the 12.7 m beam builder. NEAR TERM TECHNOLOGY EMPHASIS Constructing the large skeletal structure of the energy conversion system (5.35 km x 10.78 km x 0.47 km), including the installation and check out of its subsystems, will not be an easy task. While plausible concepts have been derived and limited development work has been started on auto-fabricat ion, a great deal of additional analysis and technology development work needs to be done before we can have confidence in the practicality of this process. For example, future dynamic analysis of the satellite construction process may show that some techniques can impose stringent load conditions on the elements of the satellite, while other techniques do not. As the reference SPS concept matures, all aspects of the construction approach must be analyzed further and periodically re-examined by considering technology issues related to the satellite design, orbit construction location, base facilities, crew and operations. These efforts should also be supported by 1aboratory investigations of SPS construction issues related to structural fabrication and assembly, construction support and subsystems assembly methods. This effort should be focused on developing technology which can lead toward SPS beam builders, SPS beam handling, subsystem assembly, mating of large space structures and techniques for dep1oying/insta11ing SPS non-structural subsystems. Subscale prototype demonstrations should be used, wherever practical.
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