power is high. Salvage value may approach as much as $200 million when other subsystems are salvaged and the demand for power is low. 3.3 Power Supply for a Laser Orbit-to-Orbit Transportation System Table 2.1 shows that whether or not the SPS program moves into an implementation phase, there is likely to be a substantial level of LEO to GEO traffic. A considerable fraction of this traffic will include man and logistics and must be transported relatively quickly, thus prohibiting the use of low thrust, electrically propelled orbit transfer vehicles. The presently planned mode for providing LEO to GEO transportation of personnel and logistics is to use a chemical rocket personnel orbit transfer vehicle (POTV). As Table 2.1 shows, the propellant requirements for the chemical POTV are considerable. These propellants must be transported from earth to LEO. The implementation of a laser space transportation system with a specific impulse of 2,000 s could reduce the propellant mass * requirements by about 72 percent. Assuming that propellant costs remain constant, and that the POTV capital cost and per flight maintenance costs are approximately equal for both the chemical and laser configurations, the principal benefit attributable to a laser space transportation system will be derived by means of cost savings in earth to LEO transportation of propellants. Furthermore, it is likely that the cost of transportation from earth to LEO will depend upon whether or not the SPS program proceeds into an implementation phase. Since transportation costs are a major fraction of total SPS capital costs, the transportation costs are likely to be low if forced by SPS technology development. They are likely to be significantly higher if SPS is not implemented thus alleviating much of the need to achieve low * Laser Rocket System Analysis, Final Report, Lockheed Missiles and Space Company, Inc., NASA CR-159521, September 1978.
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