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A PC-based computer program called ITAS is presented for spacecraft thermal analysis. The code supports full Monte Carlo ray tracing and/or conventional algorithms for view factors, shadow factors, orbital incident/absorbed fluxes, radiation interchange factors, and steady-state and/or transient temperature computations for stationary or spinning spacecraft. The geometry generator is based on primitives: polygon, box, hole-in-a-plate, cylinder, cone, disc, sphere, generic surface of revolution, generic parallelopiped, and elbow. The integrated thermal analyzer allows power and temperature profiles, thermostats, temperature-dependent thermal conductivity, user-defined nodes and conductances. Automatic 2D and/or box/plate conductance generation, single-phase fluid-flow modeling, sub-models, beta angle variation with time, spacecraft foot-print on the earth, integrated libraries for optical and physical properties and interfaces with SINDA, TRASYS, and NASTRAN.

This paper compares, in detail, the two major spacecraft thermal analysis computer codes: TRASYS (Thermal Radiation Analysis System) and SSPTA (Simplified Shuttle Payload Thermal Analyzer) when applied to two sophisticated spacecraft systems, namely, SMRM (Solar Maximum Repair Mission) and Astro-1/UIT (Ultraviolet Imaging Telescope) in conjunction with the SINDA (System Improved Numerical Differencing Analyzer) thermal code. The status of TRASYS-to-SSFTA and SSPTA-to-TRASYS translating programs at Fairchild Space Company are discussed, and a methodology for the development and analysis of spacecraft thermal math models is presented using the general-purpose interactive graphics package PDA-PATRAN-G, TRASYS, SSPTA, SINDA, and numerous in-house-developed translating programs. The orbital absorbed energies and the internode radiation conductors generated by TRASYS and SSPTA, for the aforementioned spacecraft systems, are systematically compared.