Weight Study of Partially Segmented Direct-Condensing Radiators for Large Space Power Systems
NASA technical note
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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An analytical investigation has been performed to provide an insight into the weight increase of a direct-condensing radiator for a potassium Rankine cycle space power system as the system size was increased from 1 to 10 megawatts electric while holding constant the component efficiencies and all cycle temperatures and pressures. The largest single contributor to the radiator weight is the armor necessary to protect fluid passages from meteoroid puncture. The two most important factors affecting armor thickness are the meteoroid population estimate and the radiator design survival probability. Design survival probabilities of 0. 9, 0. 95, and 0. 99 were used with a high meteoroid population estimate, Whipples 1961, and a low estimate, Watsons 1956, for 1, 10, 20, and 100 radiator segments. The radiator weight is sharply influenced by the meteoroid flux estimate and the design survival probability. For the unsegmented case, using Watsons 1956 flux estimate, the radiator weight ranged from 1. 5 to 3 pounds per kilowatt electric for the 1-to 10-megawatt power range for a 0. 9 radiator design survival probability, and 2. 5 to 6 pounds per kilowatt for a 0. 99 design survival probability. When Whipples 1961 flux estimate was used, the radiator weight ranged from 7 to 17 pounds per kilowatt for a 0. 9 design survival probability and from 16 to 42 pounds per kilowatt for a 0. 99 design survival probability. Segmentation of the radiator provided significant weight savings over the unsegmented radiator, especially when high survival probabilities were demanded. Generally the weight advantages of segmentation increased with increases in system power level, design survival probability, number of segments, and severity of the meteoroid flux estimate.
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