Table 4-21. Influence of Turbine Efficiency on Turbocompressor Mass Table 4-22. Influence of Recuperator Effectiveness on Turbocompressor Mass Table 4-23. Influence of Compressor Outlet Pressure on Turbocompressor Mass Table 4-24. Influence of Cycle Pressure Ratio on Recuperator, Cooler and Turbocompressor Mass Table 4-25. Reference Masses for Recuperator, Cooler and Metallic and Ceramic Turbomachines Importation of uranium is scheduled to begin before 1980. The programs in this study extend beyond the year 2040. Hence it is evident why only breeder reactors should be considered for SPS. 4.9.2 Breeder Reactor Program Concept Reactor modules would be assembled and fueled in low orbit. Sixteen modules were baselined for a 10 GWe ground output nuclear SPS. Only two to four modules need be energized to provide the electric power necessary for the thrusters needed for a 100 day transfer to geosynchronous orbit (assuming 50% thruster efficiency). Thus when "self powering" away from low orbit, and still relatively near Fig. 4-36. United States Energy Resources 4.9 NUCLEAR REACTORS 4.9.1 Necessity for Breeder as SPS Reactor Figure 4-36 gives estimates of the energy resources which probably exist within the United States. When all influence coefficients are at their nominal values the value of the factor influenced is 1.000. For example, in Table 4-24 when the cycle pressure ratio is 1.822 (the nominal value) the mass of the recuperator is equal to the reference mass (206,443 kg = 455,122 Ibm per Table 4-25). Decreasing the cycle pressure ratio to 1.75 increases the recuperator mass by 5.13%. Thus, to find the mass of any system wherein the influence coefficients are not 1.00, the values are obtained from Tables 4-7 through 4-24. They are then multiplied together to obtain a factor which is in turn multiplied by the reference masses in Table 4-25 to obtain the mass of the system under consideration. The above data were part of the total thermal engine SPS model used to optimize (obtain minimum total mass) the system. This process is described in section 5.0.
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