Masses of the diode assembly and the associated heat pipe radiator were given in Tables 4-5 and 4-6. Figure 5-4 gives masses for the three types of panel used to comprise the cavity absorber. Fig. 5-4. Panel Masses The diode and power converter panels have been explained; the blank panels are necesary as fillers to complete the cavity absorber as shown in Figure 5-5. Fig. 5-5. Cavity Absorber is Formed From Panels A cylindrical cavity was selected for the thermionic SPS for these reasons: 1. There is apparently no impact on efficiency relative to a sphere. 2. There is no point in placing diodes on the bottom of the cavity since the solar concentrator would block much of the view to space of the heat pipe radiators. A tall cavity (large ratio of length to diameter) minimizes the bottom area. Figure 5-6 shows one module of the thermionic SPS. It is sized to provide 4.37 GW to the main bus (a total of 17.49 GW). The output of the rotary transformer would be 17.37 GW; the rectifier/filter assemblies on the transformer will accept this power level. This 16.43 GW is available under the optimum illumination conditions (solstices); at the equinoxes the output falls to 16.17 GW which is the minimum required to provide the 10 GW ground output (see Figure 4-89, the microwave efficiency chain). Fig. 5-6. Thermionic SPS Module Per Section 4.5, the optimum reflector facet count is 17,000. The "spine" is a triangular, insulated structure carrying the 382,000 v.a.c. Figure 5-7 is a general arrangement of the SPS configuration. It can be seen that the central spine stiffens the structure and provides a convenient path for power transfer. This spine would be parallel to the polar axis of the earth as the satellite flies "perpendicular to the orbit plane" (POP). Fig. 5-7. Thermionic SPS Configuration Some additional parameters relative to this configuration are given in Figure 5-8. Ground output 10 GW Orbit busbar 17.43 GW Orientation Perpendicular to orbit plane Number of modules 4 Total number of diodes 17,473,008 Total number reflectors 70,000 Total number power convertors 1,292 Geometric concentration ratio 2,450 Cavity area ratio 68 Interior cavity temperature 1,800K (2,780°F) Diode heat pipe temperature 900K (1,160°F) Diode efficiency 0.24 Fig. 5-8. Thermionic SPS Parameters
RkJQdWJsaXNoZXIy MTU5NjU0Mg==