Transportation System Fleet Size Figure 6-8 Transportation System Fleet Size 6.2 Space Segment Sensitivity Analyses Sensitivity analyses were performed to determine the impact of key space segment parameter values and assumptions on the performance and cost of what the case studies determined to be the most economically attractive SSP concepts and markets. The concepts include: (1) a GEO-based SolarDisc architecture, each system with capacity to deliver 5GW of continuous power to a large city or timeshare the power to several smaller markets within its effective beam-steering range; (2) a MEO-based SunTower constellation delivering 250 MW per satellite for Mega-town and smaller markets; and (3) a SunTower constellation operating in Sun-Synchronous LEO orbits, each system capable of delivering 50 MW peaking or cycling power to cities or towns during the prime hours near the dawn terminator. These three concepts correspond to Case Studies 4, 16 and 13 respectively. The key parameter sensitivities that were examined include (1) transmission frequency, (2) beamsteering capability, (3) power conversion efficiencies, (4) various hardware cost assumptions and (5) various hardware mass assumptions. The findings are discussed below. 6.2.1 Transmission Frequency One of the reasons for selecting 5.8 GHz over 2.45 GHz as the preferred transmission frequency for the system concepts, was the expected reduction in the required size of both the transmitting and receiving arrays at the higher frequency. With this in mind, the results of Cases 4, 13 and 16 were compared to results obtained for the same cases using a transmission frequency of 2.45 GHz. To focus attention on frequency alone, all other system factors, including the use of 10 Watt solid state devices with equivalent efficiency, were kept constant. The comparison of results shown in Table 6-11 indicate the advantages
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