laser LEO-GEO transportation system. Its value in this use derives from the present value of cost savings on propellants transported to LEO plus savings in cost of capital on items that would otherwise go by slower means—electric rocket--from LEO to GEO. A laser rocket would use about 70 percent less propellant than a chemical rocket and thereby produce a propellant savings on the order to 430,000-5,140,000 kg/yr. The marginal cost of transporting this propellant to LEO by means of the Space Shuttle would be about $344 million-4.112 billion (1979$) per year. With more advanced vehicles, this cost could possibly be an order of magnitude lower. From the above arguments, it is clear that use of the Demonstration satellite as a power source for a laser LEO-GEO (and possibly to other orbits or- to earth escape) transportation system would have a pesent value, referenced to the year 2000, on the order of several billion dollars. Thus, it is suggested that this satellite be equipped with a laser suitable for both demonstration of the laser SPS concept and for powering laser rockets. With other potential "salvage” uses of the Demonstration satellite, such as power production, it becomes apparent that the effective cost of the Demonstration satellite is only a fraction of the cost of the microwave transmitting antenna. Thus, it is also recommended that the Demonstration satellite be used for these salvage purposes after its use as an SPS demonstration rather than being grown into a full-scale SPS satellite. Only the transmitting antenna should be salvaged for use on the full-scale SPS satellite. It is important to recognize that the above salvage value of the Demonstration satellite can dramatically alter the economic value of the SPS development program by effectively allowing a large fraction of the cost of the Demonstration Phase of the SPS development program to be borne by other programs. It is far more difficult to find relatively firm salvage uses for full-scale SPS satellites some half-centruy and more in the future. Nonetheless, there are some intriguing possibilities. One is to provide a power source to retrieve Amor asteriods for mining in earth orbit. This use could potentially provide a vast source of resources in earth oribt for space manufacturing, space habitats and for supplementing terrestrial resources, such as gold and platinum. A second use is as spare parts for other SPS satellites. It could also serve as much of the material necessary for a new SPS satellite. In any case, it should be recognized that there is a practical limit to the salvage value of any SPS satellite or component. This limit is the cost of replacing the SPS satellite with a new SPS satellite at the end of its useful life. Thus, for example, if the cost of replacing an SPS satellite at the end of its useful life is, say, 70 percent of its new cost (due to learning during its 30-year useful life) and the real discount rate is taken to be 4 percent per year, the "maximum" salvage value of the SPS satellite would be about 22 percent of its initial capital cost. It is possible, but unlikely that the salvage value would exeed this amount. It would exceed this amount only if the satellite were constructed of rare materials, such as gold, which could appreciate considerably over 30 years due to their scarcity value. These same limitations apply also to the Demonstration satellite. It is concluded that salvage uses of the Demonstration satellite have a value sufficient to offset most of its cost. Salvage uses of full-scale satellites are harder to predict, but it appears reasonable that the present value of their salvage uses referenced to the initial operation date of the satellite will be in the range of 10-20 percent of the satellite capital cost.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==