TABLE 1 (Continued) COST COMPARISON STATEMENT FOR GEOSYNCHRONOUS SPS AND LUNAR-BASED POWER SPS Lunar Cost Category Costs ($M) Costs ($M) Factors Program Management & Integration 495.0 980.0 a Totals 12,396.9 135,373.3 Power Cost (mills/kWh) 46.8 511.3 Costing Factors Key: a. Lunar cost 2 times higher because of duplicate lunar stations. b. Lunar 2 times higher due to triangular solar collection surfaces. c. Lunar 3 times higher to make up for reduced solar cell efficiency (5% vs. 15%). d. Lunar 100 times higher because of increased antenna area. e. Lunar costs 10.6 times higher using 1,070.000 klystron tubes instead of the 101,000 for SPS. f. Lunar costs identical to SPS since only 7,260 tubes perform retrodirective phasing. g. Lunar costs 25 times higher since arrays are inactive 50% of time and need warming (vs. about 2% blacked-out time for SPS). h. Lunar cost includes an additional $317.8 for indirect phasing apparatus for 1,059,300 passive subarrays on each antenna (assuming $300 per subarray). i. Lunar only 1/10 as costly assuming simplified structure and operations. j. Lunar 1/3 as costly, assuming economies in production. k. Costs assumed to be zero for lunar configuration. 1. Lunar cost 10 times higher considering personnel for lunar mining bases, construction equipment and antenna area increases. m. Lunar costs assumed identical to SPS. n. Lunar costs 3 times higher because of 3 rectennas. o. Lunar cost 4 times higher because of area increase to catch oblique beams (20 kM diameter instead of 10). p. Lunar only 1/10 as costly assuming use of predominantly lunar resources. Notes to Table 1 1. $100 million klystron cost multiplied times factors a, e (= $2,120 million). $377 million phase control electronics cost multiplied times factors a, f — assuming 99% parasitic phase control ( = $754 million). 2. For a possible way to reduce waveguide costs using open-mesh microwave, reflectors, see trade-off study in Appendix. 3. 67% cost for solar array EOTV transport in SPS assumed free for lunar (factor k). 33% cost for antenna subarray EOTV transport assumed (1/10 x 2 x 100) times higher for lunar case (factors a, d, p). as in HLLV costs. 4. $162 million SPS assumed to increase proportional to the antenna area (factors a, i and d, $3,240 million). $162 million SPS cost increases with number of power tubes (factors I, i, and e, $343.4 million). CONCLUSIONS AND RECOMMENDATIONS The concept of a lunar-based power system does not live up to the initial enthusiasm the idea generates. Configurational disadvantages such as the moon's dark phases, its tenfold increased distance from the Earth, and the inefficient interaction between multiple Earth rectennas and lunar power stations make constant, high efficiency delivery of commercial power impossible. The principal reasons for initially considering the SPS concept lay in its enhanced efficiency of power collection (eliminating weather losses and enabling 24-hour, broadside illumination) and in its continuity of supply to the power grid. Lunar-based power systems lose both of these fundamental advantages.
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