The salvage value of reuse of components of a full-scale SPS satellite depends upon which specific components, subsystems and systems are available for reuse at the end of the 30-year life of the satellite. To determine specifically which ’’pieces" will be available requires a detailed reliability/replacement/repair analysis which has not yet been accomplished. In the absence of such an analysis only a rough estimate of value may be accomplished by considering the value of extending the useful life of a full-scale satellite. The value of extending the useful life may be established as the difference in the present value of the cost of a series of full-scale satellites which become operational at 30-year intervals and the present value of the cost of a series of full-scale satellites which become operational at 30 + aT year intervals. With a real discount rate of 4 percent, a one year (AT = 1) increase in life corresponds to a salvage value of 2-3 percent of the satellite cost. This increases to 17 percent of the satellite cost when AT = 10 years. 4.2 Power Supply for Non-SPS Space Activities In the same manner that the demonstration SPS satellite was viewed as a potential source of power (335 MW) for other space activities, so may the full-scale satellite be considered as a potential source of power (9.52 GW) for other space activities. The salvage value will depend upon the demand for power created by other space activities. The supply of power will be incremented by up to 19 GW per year, starting in the year 2030, and decremented by the rate of degradation of the power supplies. Since a mission model for non-SPS activities cannot be established for the mid-21 st century, it is not reasonable to compare supply and demand (as was done for the demonstration SPS satellite—see Section 3.2) to establish the salvage value in terms of the demand for space power satisfied by the SPS satelites. It is likely, however, that the supply will far exceed the demand. At
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