2. All systems/equipments/components require substantial further definition to provide the engineering specifications required for cost projections. In many instances, current technology does not allow for dramatic cost reductions and does not guarantee the anticipated step-function improvements -- technology breakthroughs -- needed to reach the desired goals. The specific conclusions pertaining to the six areas assessed may be summarized as follows: 1. Costs for the rectenna construction (explicityly excluding the receiving diodes and rectifiers (which were not reviewed in this study) and the electrical distribution and conversion system noted in Conclusion 5 do not represent current construction technology, methods and site management. The optimisms characterizing the costs are not supported by current construction experience and overall are low by a factor of three to five times. 2. The GFRTP structures proposed are not defined sufficiently to identify the retired graphite fiber constituents and the methods of fabrication. Current costs for graphite fibers range from relatively modest $25/lb to very high — $1,000/lb. Structural cost uncertainties are consequently high and the potential cost range very large. 3. Costs for GaAs photovoltaics are extremely optimistic measured against existing technology. Breakthroughs are assumed to occur to achieve the conceptual design goals for weight, performance, and costs. 4. Costs estimated for Si photovoltaic systems are less optimistic than those projected for GaAs, but still require cost.reductions of 20 times to meet the DOE goals for 1986, performance improvements of 40 percent, and production capability increases of 100 times, to achieve the SPS objectives. The costs using the DOE goal of $0.50/Wp gives SPS solar cell costs three times higher than those estimated. 5. Current definition status of the slip ring design and number required does not permit a confident appraisal of materials, construction methods and operational capability. 6. Review of the satellite electrical system is limited to identification of necessary design features which may significantly alter the cost relationships estimated in the system definition and reference design studies. Insufficient detail is given in the studies reported to make a direct determination of the credibility of costs presented or whether all needed items are costed and included.
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