2.2.5 Cost The Task 2 Conceptual Design objective was to refine the cost estimates established during preliminary design. Cost estimates of transportation and assembly were increased in scope to include the entire SSPS and associated support equipments. A more refined assessment of the antenna structural cost was performed on the rectangular grid 1 km structural arrangement using aluminum, graphite/epoxy and graphite/polyimide. The following summarize the findings of these assessments: • Low altitude assembly is significantly lower in cost than assembly above the Van Allen belts (vs ) • The major cost driver is Shuttle per flight costs • Recurring unit costs for Shuttles, Tugs, Space Stations, and other support equipments represents 1/6th of the total assembly costs • Aluminum is 4 to 5% lower in cost than composites. Figure 2-28 summarizes the traffic and fleet size requirements for three flight plans. The total numbers of Shuttle flights required to assemble the entire SSPS includes flights for deployment of support equipments, transportation of personnel for monitoring the assembly operation and delivery of the consumables for the remote controlled manipulator modules. Flight Plan 1 and 3 assume one and two year assembly periods at the low altitude site, while Flight Plan 2 assumes a one year assembly time at the high altitude site. A significant difference exists in terms of total Shuttle flights needed for assembly at the high altitude site, primarily due to the added requirement to transport Tugs to and from orbit. The difference in total Shuttle flights required by Flight Plan 3 is not significantly different from Plan 1, but the average number of flights per day is within reason (1. 37 vs 0. 7 per day) particularly when considering the non-optimum launch opportunities available with a 190 n mi assembly altitude. Because of the orbital geometries, launches of as much as two to four Shuttles in one 15 minute launch window may be required with Flight Plan 1. The two year low altitude assembly plan is recommended based on the low number of Shuttle flights and reasonable launch rate. Figure 2-29 presents a cost comparison of the three flight plans. The low altitude, two year assembly period is the lowest cost option (1301 $/kw). This cost could be reduced with increase in STS performance by a factor of two if a heavy lift, deploy only launcher with a payload capability of 120, 000 lb (54,400 Kg) were developed from existing Shuttle
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