1.3 Results Discussion of the results is appropriately divided into four parts: salvage value for potential salvage uses of the demonstration satellite, salvage value for potential salvage uses of full-scale SPS satellites, salvage value of rectennae and disposal costs for the demonstration and full-scale satellites. The major study results are summarized in Table 1.2. Two principal salvage uses for the demonstration satellite are apparent: growth to a full-scale satellite and use as a power supply for a laser space• transportation system. Obviously, the former use applies only if the demonstration program is a success; that is, if it is found desirable to continue the SPS program beyond the demonstration phase. If this salvage use is implemented, the salvage value of the demonstration satellite is about 80 percent of the on-orbit cost of the salvageable hardware. Since almost all of the demonstration satellite is salvageable (except perhaps the ion thrusters and associated systems used to transport it from LEO to GEO), one can take the salvage value to be essentially 80 percent of the on-orbit cost of the demonstration satellite. The reason that the salvage value of the demonstration satellite is not 100 percent of its cost is because of the time value of money (discounting) and the time delay between investment in the demonstration satellite and start of construction of the full-scale satellite. The second principal salvage use of the demonstration satellite, use as a power source for a laser space transportation system, is a viable salvage use whether the demonstration program is a success or not. The salvage value for this use derives mainly from cost savings in the cost of transporting chemical propellants from earth to LEO for use in LEO to GEO transportation of personnel and logistics. The considerably higher specific impulse of a laser rocket permits about a 70 percent reduction in the mass of propellant that must be transported to
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