SPS SALVAGE AND DISPOSAL ALTERNATIVES George A. Hazelrigg, Jr. Director, Systems Engineering ECON, Inc. Princeton, NJ The satellite portion of the Satellite Power System (SPS) has a currently estimated lifetime of 30 years. The capital costs of the satellite less its net salvage value (gross salvage value less removal cost) must be amortized over that lifetime. To date, however, system cost and trade studies have been based on the assumption that the SPS satellite has zero net value at the end of that time. Many factors make this assumption inappropriate: many SPS components are replaced periodically and thus will be relatively new at the end of the 30-year satellite life; some SPS components will have lifetimes well in excess of 30 years; the SPS satellite may still be capable of producing substantial amounts of power, even in various states of degradation, that could prove useful to non-terrestrial applications; the SPS satellite represents a fairly large deposit of materials conveniently located in geosynchronous orbit; the SPS satellite represents a fairly sizeable source of refined materials that might be economically returned to earth for reuse. The first SPS satellite will reach the end of its 30-year ''useful life” at about the year 2030. Much sooner than that, about the year 2000, the Demonstration satellite will have completed its function and be available for other uses. As envisioned by Rockwell, the Demonstration satellite would be subsequently grown into a full-scale SPS satellite, thereby salvaging essentially the entire satellite, if the demonstration is successful. But it cannot be guaranteed that the demonstration will be successful--if it could, it would not be necessary. The importance of salvaging the demonstration satellite arises because it represents a very substantial cost incurred while there is still considerable uncertainty regarding successful SPS development and, thus, the SPS development program looks very much more economic if at least a major fraction of the Demonstration satellite costs do not have to be borne by the SPS program. Hence, it is important to find other potential uses for the Demonstration satellite as well. In order to determine the value of either the Demonstration satellite or full-scale SPS satellites, it is necessary to first identify their potential salvage uses and second to quantify the ''demand” for each use. This requires a space mission model for the post-2000 time period. It is, for all practical purposes, impossible to predict activities in space during the period, say, 2000 to 2060. Nonetheless, it does seem reasonable that certain generic trends can be identified, and that these trends are quite likely to occur. A basic premise is that many activities will be conducted in space simply because they are economic, independent of any government sponsorship. This leads to the conclusion that the demand for space-based capabilities will increase dramatically during the early 2000's. To accommodate this demand, space will become populated with fewer, larger spacecraft through a transition to large, multipurpose platforms. These platforms will be clustered in important orbits such as GEO and will represent very large investments, on the order of $2-10 billion (1979$). As a result, they will be serviced by a manned GEO station and are likely themselves to be manned. Concentrating only on the GEO platforms, exclusive of SPS, it is likely that there will be 15-30 multimegawatt platforms by the year 2030. These platforms will generate a LEO-GEO traffic flow of 250,000-3,000,000 kg/yr plus propellants with the lower number more likely around the year 2000 and the higher number becoming more likely toward the year 2030. About two-thirds of this mass includes people, manned vehicles and logistics which must be transported relatively quickly between LEO and GEO. Thus, one use for the Demonstration satellite would be as a power source for a
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