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The optimum radiator configuration in hot lunar thermal environments is one in which the radiator is parallel to the ground and has no view to the hot lunar surface. However, typical spacecraft configurations have limited real estate available for top-mounted radiators, resulting in a desire to use the spacecraft's vertically oriented sides. Vertically oriented, flat panel radiators will have a large view factor to the lunar surface, and thus will be subjected to significant incident lunar infrared heat. Consequently, radiator fluid temperatures will need to exceed ~325 K (assuming standard spacecraft radiator optical properties) in order to provide positive heat rejection at lunar noon. Such temperatures are too high for crewed spacecraft applications in which a heat pump is to be avoided.

The Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA/FLUINT) program is a thermal analyzer code which has frequently been used as a design and analysis tool, to determine the transient and steady-state response of various fluid flow and thermal networks. While this code has provided important information in the design and analysis of a variety of aerospace systems, the validation of the code has been limited to a few simple test cases, and did not examine the resistance-capacitance or fluid flow network solving capability of the code. For the current study, the predictions from several simple models were compared to their corresponding analytical solutions. The first comparison considered steady-state, one-dimensional heat conduction in a constant area fin with four different fin tip boundary conditions. The second portion of the study examined an infinitely long fin which rejects heat to the environment by a simultaneous convection and radiation process.