Lunar Waste Heat Radiator Design STEPHEN M. LORD & WALTER VENABLE Summary Heat rejection requirements for an advanced lunar base are estimated. Various potential designs for waste heat radiators fabricated from local materials are discussed, compared and contrasted. The various designs are found to be more or less suitable depending on base latitude. Local fabrication is found to provide a substantial advantage over importation. Introduction Demand There will be significant demand for electrical power at a prospective lunar base. Any large-scale industrial processing such as lunar oxygen production [1] requires 2-4 MW of power. The largest single portion (40%) of the mass required for power generation is for the waste heat radiator even with efficient designs such as the liquid droplet radiator [2]. Other designs such as the SP100 [3] minimize the weight penalty by operating the radiator at high temperatures, which reduces the efficiency. In fact it is recognized by French [3] that use of an SP100 for a lunar base would be improved by adding a “bottoming cycle” with its associated low temperature radiator. Distribution of the power plant mass and heat load for the liquid droplet and lunar ceramic waste heat radiators are shown in Fig. 1. The areas which require inherently low temperature heat rejection are cooling of industrial processes, agriculture, and life support. The electrical power generated to support these areas will ultimately be rejected as low grade heat. We can therefore calculate the heat rejection from these areas from knowledge of their electrical consumption and the total rejection will equal the total electrical production. Lunar oxygen plant at 1000 tons per year: 2.4 MW Agriculture for 100 people at 13 kW each [4]: 1.3 MW Life support and other services for 100 people: 0.2 MW All this heat will ultimately come from the power plant, but will be rejected at low temperatures, e.g. 90°F or 308 K (the usual temperature of cooling water on Earth) [6]. There is a demand for a low temperature, large area radiator. If such a design were cost-effective, more efficient power generation could be used either directly or via a bottoming cycle. S. M. Lord, SML Associates, 157 Rancho Santa Fe Road, Encinitas, CA 92024, USA; W. Venable, San Diego L5, P.O. Box 4636, San Diego, CA 92104, USA.
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