components. An additional reduction could be achieved with development of the Fly-Back Booster. It is conceivable that a cost as low as 300 $/kw could be achieved. An aluminum antenna structure is 4 to 5% lower in cost than a graphite/epoxy or graphite/polyimide structure (Fig. 2-30). This assumes that the basic structural elements can be made of the standard 5 mil fibers. Although the cost of composites are slightly higher than aluminum, technical factors such as thermal properties, could be the influencing factors in final selection. 2.3 RECOMMENDATIONS The concepts and design options recommended for Task 3 study are listed in Fig. 2-31. Also included are concepts that show sufficient promise for further technology study. Because of the greater cost associated with high altitude assembly, the transportation mode selection can be narrowed down to use of the Shuttle at a low altitude assembly site. Advanced transportation system with increased payload (heavy lift vehicle) and development of the Fly-Back Booster could further reduce transportation and assembly costs, and should be given greater study' emphasis. The rectangular grid structural arrangement should be retained. No technology issues arose during Concept Definition that would suggest a different approach. The light weight and standardized construction of the rectangular grid structure makes this approach the best of the options studied. Materials selection cannot be clearly made at this time. Aluminum offers the lowest cost option with the least technology risk. The graphite composites are attractive in terms of thermal expansion properties and the potential to retain stiffness characteristics at high temperature (polyimides). Basic materials technology' testing of composites is recommended to determine the outgassing and ultraviolet tolerance of these materials at the expected system operating temperatures. The assembly of structure using remote controlled manipulators was found to be potentially' the lowest cost approach. This assembly' technique would minimize the man-in- space role and would therefore minimize the need for expensive life support equipments. The use of EVA in the assembly function showed the potential for increased production rates relative to remote controlled assembly. However, the cost of large support Space Stations may preclude selection of this approach. Study of man’s role in assembly of large structure is recommended for investigation outside of the MPTS study.
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