2.3 Requirements With each new stage of concept evolution, more numerous and more detailed requirements arise. Currently, only these general guidelines are considered: (1) Each SPS power satellite shall produce 10 Gwe. Systems may be modularized if necessary to meet this requirement. (2) The operating life cf an SPS satellite shall be 30 years. Components shall either be designed to operate the full 30-year period, or a maintenance and/or replacement schedule shall be established. (3) The system shall be capable of withstanding the brief semiannual earth occultation periods. During these periods, the system shall not be required to produce electrical power. (4) A Heavy Lift Launch Vehicle (HLLV) with a payload weight limitation of 10$ pounds shall be provided to lift the system into a low earth orbit (LEO) from which it can be propelled to geosynchronous earth orbit (GEO). The system shall be capable of being assembled in orbit (either full assembly in geosynchronous orbit, or partial assembly in LEO to provide electrical power for propulsion to GEO). Requirements relative to the thermal engine system are that it shall include a solar energy collector and absorber subsystem, an energy conversion subsystem, and a heat rejection subsystem. Interface requirements at the structural, microwave and environmental system interfaces shall be specified in more detail during concept evolution. 2.4 Options Several system design options are being considered, each relative to its appropriate subsystem. These include: (1) Energy collector-absorber device. Several collector concepts are under consideration, including inflatable, inflatable rigidi zed, Fresnel, and faceted. Absorber variations include designs for flowing the working fluid directly through the absorber, or provisions for a secondary, high-temperature fluid loop with an interface heat exchanger. (2) Conversion device. Both Rankine and Brayton cycle systems are candidates; other conversion systems are also discussed. (3) Heat rejection device. The two primary options in this subsystem are (1) gas-vs-liquid radiator, and (2) conventional-vs- electromagnetic (EM) pump in the case of a liquid metal coolant loop. These options are discussed in this report, and evaluations of the proposed Boeing system are made wherever sufficient data exists.
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