Using table IXD-1 and estimating 1000 to 2000 dollars per KW for the SPS would indicate that for a 10 GE plant, that 3.52 X 1010 to 4.62 X 10^0 metric ton KM would be expected to be expended in the construction of an SPS. Figure IXD-1 would yield about 2.25 X 1010 metric ton kilometers indicating that this model is reasonable. This amount less than 1 percent of the total projected for miles for the year 2000 for a single satellite. For the maximum rate of construction (7 per year) it would barely exceed two percent of the lowest projection of total ton miles for the year 2000. E. Energy Payback A preliminary study was conducted to assess the energy required for the implementation of an SPS and the time required for the SPS to generate an equivalent amount of energy. Table IX-2 lists the energy intensive materials required for the implementation of an SPS of "nominal" weight and the energy involved in its production. 6.7 X 10^0 KW hrs are required in the processing of the material for an SPS. Approximately 80 percent of the total is involved in the production of the necessary propellants and aluminum for the rectenna. Previous comments regarding the use of aluminum for the support structure of the rectenna should be noted.
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