h. Development Program No detailed development program is spelled out in the available documentation but an overall program schedule has been set-up and is shown in Exhibit 12. Development starts in 1978 with the first satellite on line in 1991. Peak power production occurs in 2011 when 62 satellites are on line. The program phases out in 2041. 3. Nuclear The orbiting nuclear reactor power plant concept described below is based almost entirely on the work performed by Boeing Aerospace Company for the Marshall Space Flight Center as reported in References A12, A17, and E9. Exhibit 13 is a highly simplified representation of this concept. The satellite is located in geosynchronous orbit, and the nuclear power source is a molten salt breeder reactor (MSBR). Two energy conversion systems are considered: (1) the closed Brayton cycle system which involves rotating machinery, and (2) the thermionic system which is passive except for coolant pumps. The resultant electrical energy is converted to RF by a microwave converter and transmitted to an earth-based rectenna via a microwave beam. Reference A17 states that a quite recent finding is that the nuclear- thermionic SPS concept is not feasible with projected 1985 technology. The reason given for this is that the temperatures involved would limit the efficiency of the thermionic diodes to 23%, thus 77% of the total energy would have to be dissipated as waste heat and this would require more pumping power than the electric power produced. Nevertheless, for the sake of completely reporting efforts to date, a description of the nuclear-thermionic concept is provided below. The primary salt mixture in the MSBR contains both fissile fuel (the energy source) and fertile fuel. The fertile fuel breeds to become fissile fuel for subsequent use. A small secondary salt flow is continuously passed through a fuel process system. This system removes the protactinium and wastes which would "poison" the reactor by excessive neutron capture. The fuel process system introduces fertile fuel and removes bred fuel. The MSBR is a unique breeder concept in that a single fuel mixture contains
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