9. The system optimization criterion shall be minimum cost per kilowatt hour: both recurring and non-recurring costs shall be recovered from operational revenues. 10. Man will be utilized in space as required appropriate to the above minimum cost goal. 11. Nuclear reactors shall be of the breeder type. 12. In-space power conversion will be by thermionic diodes or closed Brayton cycle thermal engines, or by photovoltaic cells. 13. The low orbit boost vehicle shall be based on the Class 4 type from the Heavy Lift Launch Vehicle Study (NAS8-14710). 14. Launch latitude shall be assumed to be 28.5°N. 15. Radiator system metoroid resistance capability shall be such as to provide a degradation of 30% or less of the total area without repair or replacement of damaged panels, over a period of 30 years. This does not preclude such repair or replacement. 16. Program economics analyses shall be based on a 30-year investment horizon and a 7.5 percent discount rate. 17. Availability of the Space Shuttle shall be assumed. 18. Mass statements will not include a contingency factor. Requirement 6, above results in a requirement for 600 GW ground output capability by the SPS system by the year 2016. This can be supplied by either 120 5-GW units or 60 10-GW units. Requirement 15 sets an arbitrary requirement that requires 1% of the Brayton radiator systems to be repaired in each year of operation. This is not necessarily the optimum maintenance. (The optimum maintenance level would strike a proper balance between meteoroid protection mass—hence cost—and maintenance cost to yield a minimum overall cost for power.) REFERENCES 1. Electrical World, September 15, 1974. 2. Hannon, B., "Energy Conservation and the Consumer," Science, 11 July, 1975 (Vol. 189, No. 4197). 3. Hauser, L. G., "Future Trends in Energy Supply," 1974 Textile Industry Conference. 4. Moody's Public Utility Manual, 1974. 5. Electrical World, September 15, 1973. 6. "World News Beat," Electrical World, July 1, 1975. 7. Morgan, M. G., Barkovich, B. R. and Meier, A. K., "The Social Costs of Producing Electric Power from Coal: A First Order Calculation." IEEE Proceedings, Vol. 61, No. 10, October 1973. 8. Electrical World, December 1, 1976.
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