• SPS initial operational capability is assumed to be 1995. • An SPS operational lifetime of 30 years is assumed. • A program of thirty or sixty 10 GW stations is assumed. (This report contains cost results of a sixty 10 GW station program analysis.) 14.4 METHODOLOGY 14.4.1 COST MODELING AND ESTIMATING METHODOLOGY The cost estimates presented in this report were developed from the interim MSEC SPS cost model4 utilizing parametric cost estimating techniques. Cost estimating relationships (CER) in this model were derived from historical and projected cost, technical, and programmatic data applicable to the SPS cost elements. Transportation and space construction base costs were derived in other MSFC studies and were included in the SPS cost estimate as throughputs. The interim MSFC SPS cost model is, as the name implies, at an early stage of development and will be updated next year by a more comprehensive model. Although the costs are considered to be the best possible estimate at this time, the CER's have been applied broadly and generally to SPS subsystems which are themselves in the early stages of definition. Because of these uncertainties, an overall system cost contingency of 15 percent has been included. In addition, other contingency factors including weight contingency, subsystem contingency, etc., have been used as appropriate and are so noted. These additional contingencies should reduce cost growth due to unknowns and increase the validity of the estimate. Additional cost data are now being collected, normalized, and documented so that a more accurate cost model will be available for future SPS cost estimates. 14.4. 2 ECONOMIC METHODOLOGY The primary criterion for economic evaluation of the SPS was the generation cost of electrical energy at the ground bus bar in mills per kilowatt- hour (a mill is one-tenth of one cent). As stated, generation cost refers to the cost of energy at the ground bus bar and not the ultimate cost of the energy to the consumer. (A rule of thumb is that transmission and distribution costs are 4. ''Interim Satellite Power System Cost Model,'' IN-PP03-76-2 published by the Engineering Cost Group (PP03), Marshall Space Flight Center.
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