to be the best choice for self-powered orbital transfer. These engines are also suitable for subsequent use as thrusters for the SPS attitude control system. 11. The high launch rates required indicate that launch window and related operational considerations may become significant factors. Launch latitudes near the equator greatly expand the launch window and offer performance advantages. 12. Based on varying assumptions as to performance, construction, location, orbital transfer modes and reusability, achievable transportation costs to geosynchronous orbit are estimated to range from $71 to $294 per kilogram. The major contributor to the total transportation costs for a given program was the cost of transporting the necessary material to low earth orbit. 13. The cost of producing electricity from solar power satellites as described herein is estimated to be in the range of 29 to 115 mills/ kWhr. This range of estimates is based on the following assumptions: o An implementation of 112 10-GW satellites over a 30-year period o A range of satellite weights and transportation costs as indicated earlier o A design, development, test and evaluation (DDT&E) cost o A space hardware repair/replacement rate of 1% annually o Plant factor of 92 percent allowing for eclipses and maintenance time o Return on capital investment of 15 percent 14. The cost of producing electricity with conventional (nuclear and fossil) plants is predicted to be in the 30 to 60 mills/kWh range, in the 1995 time period, depending upon the cost, fuel, and type of power plant. The cost of producing electricity with potential ground- based power plant concepts (ground solar, geothermal, wind) are estimated to be from 28 to 121 mills/kWh. 15. The introduction of SPS in lieu of meeting an equivalent portion of the nation's energy needs with new nuclear and coal-burning electrical power plants will result in significant reduction in emissions (particulates, N0v, SO , nuclear waste). X X 16. The microwave power density at the edge of the rectenna (1 mW/cm^2) is about one-tenth of the present U.S. standard for human exposure. The
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