The materials considered in this initial assessment included: • Aluminum (Alzac coating) • Graphite/epoxy (white paint coating) • Kevlar polyimide (white paint coating) The two structural arrangements evaluated were the "rectangular grid" and "radial spike" designs discussed in Reference 16. Antenna diameters of 1.4, 1.0 and 0.7 km were assessed. Figure 3.5-1 and 3.5-2 summarize the Task 1 preliminary estimates of weights and costs for the "rectangular grid" and "radial spike" design options. Figure 3.5-1 shows weight and cost variations for antenna diameters between 0.7 and 1.4 km and for aluminum, graphite/epoxy and Kevlar/polyimide. Figure 3.5-2 shows the radial spike design for a 1 km diameter antenna using the same three materials. Only two of the four flight modes (e.g., Cryo Tug, Mode ID and Shuttle/low orbit assembly, Mode IV) are presented. The performance of the Transtage IUS was found to be insufficient to deliver assembly crews to a site of 7000 n mi altitude. Assembly at low altitude shows a significant cost benefit over assembly at 7000 n mi. On the average, a 40 to 60% decrease in costs can be achieved with the lower altitude assembly site. Kevlar/polyimide is potentially the low cost material for assembly at 7000 n mi altitude. This cost advantage over aluminum or graphite/epoxy will be greater if it can be shown that the thermal variation of polyimide would be sufficient to withstand the expected environment without coatings. Aluminum is the low cost material for low altitude assembly, with Kevlar polyimide the second choice. Aluminum structure will be approximately 25% less costly than graphite/epoxy and 20% less than Kevlar for the low altitude case. The rectangular grid (1 km) antenna was selected for concept definition during Task 2. Aluminum and graphite/epoxy or polyimide was selected for more in-depth assessment. Further evaluation of the assembly altitude selection was recommended to determine the impact on cost: • Support Equipments • SEPS transportation costs '• Assembly costs of the entire SSPS.
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