8.4.1 Satellite Power System (SPS) Reference Concept Description The system configuration considered in the NASA/DOE report is summarized in Figure 8.8. It consists of 60 satellites of 50,000 tons each and an output power of 5 GW, to be posted in geosynchronous orbit at a rate of 2 per year, with a pre-assembly phase in LEO (480 km) and a final one in GEO (35,800 km). A permanent construction crew of 600 was estimated. Figure 8.8 SPS GEO Construction Concept. 8.4.2 Space Transportation Systems (STS) Studied. Earth-to-Orbit vehicles. The main configurations of Heavy Lift Launch Vehicle (HLLV) were studied for the cargo payload (Figure s 8.9 & 8.10). They resulted from low cost configurations (large payloads, reusability and frequent operations) and state of the art technologies (developed for the Space Shuttle for example). The BOEING HLLV Reference concept has a payload capability of 420 metric tons to LEO and is a winged two-stage, series burn configuration designed for vertical take-off and horizontal landing. Both stages are fully reusable. The booster (first stage) uses 16 LOX/LCH4 engines with high Isp (352 sec) and a vacuum thrust of 9.8 MN each (4.7 times the SSME), with an air breather propulsion system for flyback to the launch site. The orbiter has 14 LOX/LH2 SSMEs and 4 LOX/LH2 Orbital Maneuvering System (OMS) engines. The main technology requirements for this configuration is the TPS. The conservative ideas of this system were the key factor to its selection as “HLLV Reference Concept” for the SPS project in 1980. An Alternate BOEING HLLV concept with a payload capability reduced to 120 metric tons was also proposed. Its configuration is directly derived from the previous one. The booster uses 4 LOx/LCH4 engines and 4 high thrust air breather engines for flyback. The orbiter has 6 SSMEs. Despite slightly higher recurring costs (greater number of construction crew, more propellant consumed) and more frequent flights, this configuration was recommended by Boeing because of lower non-recurring costs (more commonalty with Space Shuttle), lower facilities costs and a size more appropriate for alternative missions.
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