feasibility of using the SSPS for this purpose and reconfiguring it once in geosynchronous orbit, proved to be extremely costly because of the additional hardware required to support reconfiguration. Manned Space Stations in geosynchronous orbit would be necessary to support the reconfiguration crew; this would impose a requirement for a Tug fleet and additional Shuttle flights to effect deployment of hardware, consumables, personnel, and Tugs. Secondly, a delay in the start of SSPS operation would be required. A separate SEPS array avoids the reconfiguration step and results in lower total program cost and a SSPS which becomes operational earlier. Results of the fleet size analyses show that 24 Shuttles are required for the one year assembly plan (Flight Plan 1) and 15 Shuttles are needed to support the two year assembly plan (Flight Plan 3). In both cases, two crew support modules are required to support the six-man crew. Eight manufacturing modules and 182 manipulator modules are needed for Flight Plan 1 and half that number for Flight Plan 2. Figure 3. 5-8 presents the detailed Shuttle/Tug flight requirements necessary to support Flight Plan 2, i.e., one year assembly at 7000 n mi. Since atmospheric drag is not a consideration at 7000 n mi, the stationkeeping module has been eliminated. The figure shows that the Shuttle is required to make approximately 1300 flights in a year. The dramatic use over the LEO assembly requirement of approximately 500 Shuttle flights can be explained by the fact that additional flights are required (at less than 100% load factor, i.e., 65000 lb payload) to get Tugs into orbit. The result is that 59 Shuttles and 37 Tugs are needed to support Flight Plan 3. 3.5.2. 3 Launch Opportunity Sensitivity to Traffic Rate The Shuttle has an ETR launch opportunity every 23.5 hours to a 190 n mi 28. 5 inclined orbit assembly site. A glance at the total number of Shuttle launches required for either of the one year assemblies (see Fig. 3. 5-9) indicates that from one to four Shuttle launches per day are required if orbit phasing is neglected. Worst case phasing conditions can exist on some of these days; this only serves to aggrevate the launch/day situation. This situation arises from the fact that under worst case phasing conditions, it is optimum to delay launch a day, and spend 16 hours phasing with the assembly area at 190 n mi. The alternative is to launch on the first opportunity, spend 40 hours phasing, and arrive at the assembly point at the same time as a vehicle that delayed launch for 1 day. Obviously, it is more advantageous to delay launch for the day and wait on the ground for better relative launch site/assembly point phasing to exist. This waiting would mean that the ETR launch rate would double on some days during the year and that from 2 to 8 vehicles would have to
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