1.4 What is the basis for the claim that the satellite will have a 30-year lifetime? This is not a claim; rather a 30-year lifetime was selected as a design guideline for operation planning and costing exercises. The ever-lengthening lives of current unmanned satellites, however, together with the rather benign conditions in geostationary orbit (no gravity, no weather, very little wear, etc.) suggest that 30 years, with maintenance, may not be an unreasonable goal. Refurbishment is also part of the program planning for SPS and could extend satellite lifetime considerably beyond 30 years. 1.5 Have maintenance requirements been considered in the analysis of the reference system concept? How could maintenance be performed? Maintenance requirements have been considered in the reference system analysis as part of the reliability and lifetime analysis. Costs and manpower have been estimated; including spare parts, transportation and level of effort. Much of the maintenance associated with the rectenna would be conventional in nature, and include maintaining roads, rectenna panels and supports, the power collection and transmission systems and control center. Most of the work would entail general equipment maintenance. Estimates of labor for scheduled and unscheduled maintenance and repair of the rectenna and electric power collection system have been estimated at 64 employees^ per rectenna. To determine maintenance requirements for the satellite, eighteen SPS components were selected for detailed analysis. The components were selected for one of three reasons: 1) the component was representative of a class of components, 2) failure of the component results in significant power loss or 3) the component is highly stressed and could have a high failure rate. The number of personnel required for satellite maintenance would be a function of the amount of direct versus remote monitoring. It is currently estimated that the 60-satellite system would be maintained by about 975 workers,$ probably stationed at the GEO construction base and ferried back and forth to the satellites, as required.7 ^General Electric Space Division (GE) Solar Power Satellite System Definition Study Part 4 Phase 1 Final Report, GE 1979, reported in: "Prototype Environmental Assessment of the Impacts of Siting and Construction of a Satellite Power System (SPS) Ground Receiving Station (GRS): Project Description," ERG, (November 1979). Briefing given on Satellite and Rectenna Construction and Maintenance, "Some JSC SPS Activities," NASA JSC, November 28, 1979. ^SPS Concept Development and Evaluation Program Reference System Report U.S. DOE/ER-OO23, October 1978.
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