CRITICAL REVIEW OF SATELLITE POWER SYSTEMS (SPS) SPACE TRANSPORTATION COST ESTIMATES R. W. Earhart, C. W. Hamilton, K. Maher, R. R. Teeter Battelle Columbus Laboratories, 505 King Avenue, Columbus, Ohio 43201 Satellite power systems must be economically competitive with alternative terrestrial methods to achieve broad success. As part of a comparative assessment of power generation costs in the SPS time frame, investigations of the SPS cost estimates have been undertaken. The results reported here cover the SPS space transportation requirements and costs for the current Reference Design. (1) The vehicle design and theoretical first unit costs estimated by the contractors are reasonable. The learning assumptions made are also reasonable, but the use of the average unit costs for the initial vehicles is questioned. The chemical propulsion vehicles have uncertainties, inherent in the methodology of cost estimating relationships, of ten to twenty percent in the stated costs. This low uncertainty is predicated upon successful completion of the Space Shuttle and an active NASA space program pursuing vehicle technology. (2) The SPS program costs for transportation are based on an ambitious scenario which assumes 100 percent reliability for the vehicles. An increase in recurring transportation costs of about ten percent, to allow for additional vehicles and related efforts to insure the ability to maintain the proposed SPS platform construction rate of two per year is recommended. The exact level of the reserve vehicles depends upon determining acceptable program risks. Until this is accomplished, a reserve of 10 percent, in analogy to airlines, should be used. (3) The special development of the Personnel Launch Vehicle (PLV) Booster for use in the SPS is questioned. The use of a personnel module aboard the Heavy Lift Launch Vehicle (HLLV), if acceptable for safety, would avoid the booster development expense and have a lower recurring cost than the PLV. The appropriate use of the Shuttle or its derivatives is, however, still an open question. (4) The Electric Orbit Transfer Vehicle (EOTV) has the highest cost uncertainty of the vehicles in the Reference System because experience in the technologies needed, especially space structures, is not as advanced as experience in other vehicle technologies. The large size of the EOTV indicates a potential problem of a significant collision rate and the need of structural and other redundancies to permit survival with only slightly degraded capabilities. Achieving the EOTV cost estimates is predicated both on demonstrating successfully the vehicle technology through applications such as a Solar Electric Propulsion Stage and also on the successful development of the SPS platform design itself. The EOTV is viewed as a section of the SPS platform with the power directed to ion engines rather than a microwave antenna. The uncertainty of the EOTV cost can therefore only be rated as "very high" for which the value -15 percent to +100 percent is assigned to compute the potential quantitative impact on overall transportation costs. Detailed findings are summarized in the Table.
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