approximately 5 x 10 km for an elliptical arrangement of the power modules and a center location of the single antenna. The profile of an individual concentrator module is shown as a detail of Figure o-3. The total area of the concentrators is 322 km2, the output per module is 540 W/m2, and the total estimated mass is 221 x 106 kg. The orientation of the configuration is perpendicular to the Sun. Pertinent descriptive data for this configuration are presented in Table 5-2. An alternate configuration concept, which features end locations for the antennas, is shown in Figure 5-4. A trade study has been conducted to identify the configuration with an optimum number of modules for minimum mass and to determine the cost of the operational system. The results of this study show the optimum number of modules to be approximately 40. 5.3 NUCLEAR A typical concept of the nuclear Brayton configuration is shown in Figure 5-5. In this configuration an antenna 1 km in diameter is located between the nuclear modules and their required radiator area. A simplifying feature of the nuclear system is that occultations in orbit do not interrupt system operation. However, radiation problems make interfaces with this system complex. Also, an estimate of the mass of the nuclear system shows it to be quite heavy, approximately 300 x 106 kg. A schematic of the nuclear Brayton cycle system is shown in Figure 5-6. The concept shown utilizes a molten salt breeder reactor with continuous fuel reprocessing. The temperature limit of the molten salt limits the turbine inlet temperature and the operating efficiency of the Brayton cycle, which, in turn, affects the overall system size. The current trend is, therefore, to use a system with a gaseous fuel reprocessing system to relieve the above temperature limit constraint. 5.4 CONCEPT COMPARISON Data comparing the photovoltaic, thermal concentrator, and nuclear concepts for satellite power are shown in Table 5-3. The nuclear system, having the smaller dimensions, is the more compact of the three systems. The mass estimate for the photovoltaic system, however, shows this system to be the lighter of the three.
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