Table 5-2 is a mass statement for the 10 GW ground output SPS. Table 5-2. Thermionic SPS Mass Statement Although configuration variations were not analyzed, it is possible that reconfiguration of the diode heat pipe radiators could result in a lighter SPS. By changing to a heat pipe configuration similar to that shown in Figure 5-8 the diodes would be brought closer together allowing a reduction in interelectrode busbar length. Examination of Figure 4-21 can lead to a calculation indicating that the total interelectrode busbar mass is 49.6x10^ kg (1.09xl0^1bm) which is approximately 25% of the total SPS mass. Thus there is some possibility that reconfiguration might effect a net thermionic SPS mass reduction of approximately 20% below that given in Table 5-2. Fig. 5-8. Reduction of Interelectrode Busbar Mass 5.3 SOLAR LIQUID COOLED THERMIONIC (CONCEPT 2) In this concept diode collector cooling is accomplished by a separately located radiator system. Such a radiator would be similar to that used in the Brayton systems (heat pipe panels with pumped manifolds). By cooling the diode collectors with an active liquid metal loop that can in effect be coupled to a greater radiator area than is practical with fins attached to the collectors, achieve a greater temperature differential across the diode, and therefore obtain higher efficiency. Figure 5-9 shows the approach taken to interface the liquid radiator to the individual diode collectors. Fig. 5-9. Diode/Radiator Interface One problem with this concept is that the diode collectors must be electrically isolated; thus the coolant tubes require electrical insulation. However, good thermal conductivity is also required. Beryllia (BeO) saddles provide the electrical insulation. Spring systems (kept cool by being outside the insulation batting) provide pressure to hold the diode collector, the saddles and the NaK tubes in contact. Aluminum is used as a contact improver; over the 30 year design life the NaK tubes will increase in diameter due to creep, the aluminum spacer should yield to accommodate this growth. The tubes shown in Figure 5-9 would be brought together in manifolds which deliver NaK to the pump system, as shown in Figure 5-10. The diagram shows a liquid metal (NaK) heat pipe/fin radiator concept. Liquid metal is pumped from the heat source through feeders and headers
RkJQdWJsaXNoZXIy MTU5NjU0Mg==