Fig. 5-10. Radiator Concept into the radiator panels. The cooled liquid metal is returned through headers and feeders to the heat source completing the cycle. An accumulator provides a positive pressure at the pump inlet. The heat pipe/fin panels are 20m x 20m (65.6 ft x 65.6 ft). A NaK header through the center of the panel carries thermal energy in the form of sensible heat. Meteoroid penetration of a heat pipe causes that pipe to stop operation, although it continues to act somewhat as a fin for adjacent heat pipes. Since the header fluid is isolated from the heat pipe fluid, heat pipe penetration does not pause loss of NaK. Leak detectors, isolation valves, and control systems associated with meteoroid punctures will not be required. A most critical parameter to be determined was the optimum radiator temperature (hence collector temperature) to be used with the baseline molybdenum emitter temperature of 1800 K (2780°F). This and other critical parameters were addressed by parametric modeling and computer optimization. Figure 5-11 shows the systems interactions model (the interdependencies of primary system elements). Parametric expression for each of these variables were coded for automatic processing by the ISAIAH (Integrated Sensitivity and Interactions Analysis—Heuristic) program. The objective function was minimum system weight. Several features of the model should be noted: 1. The radiator weight is a function of its temperature, to account for the change in material allowables with temperature. Fig. 5-11. Liquid Cooled Thermionics ISAIAH Model
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