Cost analysis including 51 separate categories indicates a production cost of $135.37 billion (1977 dollars) for a lunar based power system comparable to the baseline SPS ($12.4 billion). This represents approximately an elevenfold cost increase and would result in grid delivered power cost of 511 mills/kWh as compared to 46.8 mill/kWh estimated for the SPS. Among the individual EPS subsystems, solar array costs, rectenna costs, and microwave antenna costs all increase by factors of 3.3, 9.9, and 39 respectively. For a 5 GW LPS system, the antenna alone would cost $69.4 billion due to a requisite hundredfold increase in antenna area, and to requirements for more power tubes, smaller subarray units, emplacement of two antennas instead of one, and the extra costs of mechanical subarray steering. These figures take into account only materials and production costs and not the substantial program development costs of lunar operations. The $69.4 billion antenna expenditure occurs for a system producing a microwave beam analogous to the SPS reference system, with comparable main beam shape, sidelobe levels, grating lobes, etc. It is possible to reduce LPS antenna system cost by using lower cost radiators which also have reduced transmission efficiency. The effect of diminished radiator efficiency is to increase beam sidelobe levels above the environmental standards used in the SPS design. If microwave environmental limits are relaxed, then the LPS antennas could be built for approximately $38.5 billion with an LPS system cost of $104.7 billion as given in the Appendix. However, for this paper the more stringent environmental limits will be applied to both the SPS and the LPS. Although lunar power plants cannot compete economically with solar power satellites using conventional methods of energy transfer, lunar operations do have significant potential advantages in other applications. These potentials include: 1. Supplying power to lunar mining/manufacturing operations or to a lunar planetary launching base. 2. Providing solar cell materials to solar power satellites. 3. The use of other methods of energy conversion: i.e., solar thermal. 4. A long range possibility of supplying power to the Earth, should future development of orbital sunlight and microwave power reflectors allow the lunar configuration to overcome its inherent orbital disadvantages. It is recommended that study efforts be directed into determining the feasibility of generating solar cells quickly and efficiently from lunar-type soils. These studies could evolve into an Earth demonstration using similar soil materials. REFERENCES 1. Solar Power Satellite System Definition Study — Phase II, Vol. II: Reference System Description, Boeing Aerospace Co. (Contract NAS 9-15636), NASA CR-160443, 1979. 2. U.S. Department of Energy and National Aeronautics and Space Administration, Satellite Power System, Concept Development and Evaluation Program: Reference System Report, DOE/ER-0023, October 1978. 3. G.D. Arndt and E.M. Kerwin, Multiple Beam Microwave Systems for the Solar Power Satellite, Space Solar Power Review, 3, 301-315, 1982. 4. E.M. Kerwin and G.D. Arndt, Grating Lobe Characteristics and Associated Impacts Upon the Solar Power Satellite Microwave System, Space Solar Power Review, 3, 255-280, 1982. 5. E.M. Kerwin and G.D. Arndt, Antenna Optimization of Single Beam Microwave Systems for the Solar Power Satellite, Space Solar Power Review, 3, 281-299, 1982.
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