Two cost perspectives are necessary for concept evaluation. The first involves the total cost necessary to research, develop, facilitize, and construct the first full-scale system. The program phases involved in achieving this first unit and the associated costs are discussed in reference 2. The second perspective involves the cost of replicating the initial system and thereby increasing the total power available. The work breakdown structure presented in table 1 has been utilized in developing the cost estimate. The actual structure used involves many more levels of detail than portrayed in the table. Cost estimating procedures have included conventional estimating relationships based on existing data bases coupled with a "mature industry approach" where very large production quantitites are involved. The satellite costs are those required to produce the 51,000 metric tons of material and components in earth-based facilities. Construction costs include the funds required to maintain and operate the space staging and construction facilities including salaries and supplies for the construction crews. The transportation costs involve the operation of fleets of four types of vehicles ferrying crews and cargo to the space construction facility. The rectenna costs include both the cost of the materials and components and the associated construction costs. Maintenance costs include the crews and components, transportation and facilities necessary to service the satellite and the rectenna, after operations are initiated. Table 2 presents a summary cost estimate for a particular program scenario, involving the construction of two-five gigawatt systems per year over a thirtyyear period. Cost estimates are presented for each program phase leading up to the first full-scale unit and the average cost of the succeeding fifty-nine units. The relative cost of the energy system, construction, transportation, and program management costs are presented. Concluding Remarks Accurate cost estimates for any advanced energy systems are very difficult to develop, since such estimates require technology advancement projections over an extended period of time. Nevertheless, such estimates are necessary to the preliminary evaluation of advanced concepts. The primary value of such estimate is to provide an indication of whether the concept should be pursued relative to other concepts, and to evaluate the relative cost importance of the various elements contained within the program. The estimated costs presented in table 2 were obtained from studies conducted by the Boeing Aerospace Company as part of the SPS System Definition effort. Reference 1. Reference System Report, Satellite Power System Concept Development and Evaluation Program, Department of Energy and the National Aeronautics and Space Administration, October 1978. Reference 2. Piland. R.O. SPS Cost Methodology and Sensitivities. Satellite Power system Program Review, Department of Energy and the National Advisory Committee for Aeronautics, April 1980.
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