systems for the transporting of massive payloads from LEO to GEO or other intermediate orbital points. Consequently, low thrust electric propulsion becomes a prime candidate for the transporting of a self-powered solar power satellite from a low Earth assembly orbit (435 km) to a geosynchronous position. The theoretical feasibility for implementation of this very complex problem has been demonstrated; however, the challenge is so great that the complexities and anomalies involved are unequaled by any space venture that has been attempted. 7.1. 5. 2. 2 MISSION PROFILE A projected mission profile for LEO to GEO orbital transfer will have to take into consideration a number of trades to arrive at the optimum set of initial orbital parameters that will in effect define the assembly orbit for the construction of the SPS. Outstanding among these trades are: 1. HLLV and electric propulsion performance penalities and limitations 2. Thermal cycling (loss of thrust due to shadowing) 3. Solar array (Van Allen Belt transit) degradation 4. Economics associated with long versus short trip times 5. Aerodynamic drag in LEO 6. Thrust load limitations on SPS structures. Several iterations of these trades have been performed, and trends are developing such that a tentative or preliminary mission profile and associated assumptions may be stated at this time. A first significant assumption is that a nearly total sunlit orbit is assumed for the transfer phase of the mission. Assumption of an SPS assembly orbit of 435 km and 55° inclination will eliminate the necessity and cost of a chemically augmented (hybrid) propulsion system while utilizing only low thrust propulsion for orbital transfer. Opportunities for sunlit orbit interception and SPS transfer occur at this point. However, an HLLV performance penalty of approximately 25 percent (with an analogous increase in launch cost) will be incurred for 55° inclination launches when compared to due East (28. 5°) inclination launches. Some study data indicate that this penalty may be reduced to less than 10 percent for multistage HLLV's, but this must be further substantiated. If an SPS assembly orbit of
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