3.5.2 Task 2 - Concept Definition Results The Task 2 findings are summarized as follows: • Low altitude assembly (190 mni) is significantly lower in cost than assembly above the Van Allen belt. • The major cost driver is the Shuttle operations cost. The most payoff for reduction of overall assembly and transportation costs would be the reduction of the per flight STS costs by introducing the Fly-Back Booster and/or heavy lift vehicle. • Recurring unit costs for Shuttles, Tugs, Space Stations, etc. represents 1/6 of the total costs for assembly. • Aluminum is the low cost material for the antenna. Composites increase cost 4 to 5%. 3.5.2.1 Transportation and Assembly The assembly and transportation system elements assumed for the low altitude and high altitude assembly site Task 2 cost estimates are presented in Fig. 3.5-3. The low altitude assembly site uses the Shuttle for transportation of materials and consumables. The Shuttle, augmented by support modules in the pay load bay, are used for crew accommodations. Detailed parts are fabricated in orbit using automated manufacturing modules. Assembly is performed using remote controlled manipulators. Solar Electric Propulsion is used for transport of the assembled SSPS to the geosynchronous orbital position. The high altitude site requires the addition of the Full Capability Tug for transport of materials and must be augmented by a crew transport module for rotation of assembly crews. A six- man space station is assumed required for crew accommodations at the high altitude site. 3.5.2.2 Fleet Size and Traffic Assessment Both fleet size calculations and the assessment of vehicle traffic are directly affected by the total weight that is transported to orbit, the assembly altitude, and the assembly time in orbit. This subsection presents the effect that these elements have on traffic rate and fleet size for three representative flight plans. All three flight plans considered in-orbit manufacture of all SSPS structural components by manufacturing modules. The three flight plans are: • Flight Plan 1 - One year assembly at 190 n mi • Flight Plan 2 - One year assembly at 7000 n mi • Flight Plan 3 - Two year assembly at 190 n mi. Figure 3.5-4 summarizes the SSPS component weights for the three flight plans listed above.
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