system on U.S. dependence on foreign fuel sources is noted but nowhere integrated into the cost or benefit calculations. These exclusions are consistent with the explicit use of a "market" definition of economic viability, although they may be too restrictive for potential public policy decision-making. The limited literature on the Power Relay Satellite (PRS) systems suggests that this system is not economically viable by the "market" definition since it appears to offer no costs savings over current or projected energy transmission costs at distances less than 3,500 miles (5,630 km), which would limit any potential applications to international power transfer. Furthermore, the uncertain but potentially hazardous environmental impacts appear to militate against further detailed exploration at this time (Ref. All). Little, if any, cost information is available on the proposed nuclear satellite system. Although the most conprehensive reference (Ref. A12) suggests that the system is not cost competitive, no specific cost estimates are given. The balance of this discussion will therefore be largely confined to the proposed solar-photovoltaic and solar-thermal satellite power systems. a. Conceptual Components of System Costs The major conceptual components in determining total system costs as a prerequisite to estimating costs per kilowatt hour are: • Development (DDT&E) costs • Capital costs, including manufacture, transportation, and assembly • Recurring maintenance costs • Other recurring costs, notably taxes, insurance, depreciation and profit. With the esception of the ECON report (Ref. All), the DDT&E costs are not quantified. Any attempt to integrate DDT&E costs into final per unit costs requires major assumptions about the number and timing of separate satellite systems which appear to be outside the scope of most
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