An Efficient Procedure for Multiple Case Thermal Radiation Analysis of Spacecraft External Surfaces

Increasingly complex missions with reduced budgets has placed a premium on “better, cheaper, faster” system approaches for producing spacecraft. The natural consequence of this pressure to improve quality while reducing process time and expense is that activities once considered essential to design and development are now viewed as luxuries. To produce timely inputs during the condensed design phase, the spacecraft subsystem architect must continually improve the efficiency of analysis activities. This type of improvement is particularly necessary in the area of thermal analysis, which is often viewed as a peripheral activity. However, through the use of enhanced software analysis tools, the thermal engineer can ensure a comprehensive spacecraft thermal analysis that yields timely system design inputs in a cost-effective manner. This paper documents one such software tool, the Multiple Case Thermal Analysis software, developed at The Johns Hopkins University Applied Physics Laboratory to aid in the thermal analysis of spacecraft with complex mission scenarios.

This software reduces the effort needed to optimize spacecraft thermal coatings and radiator sizes for multiple Sun-angle thermal analysis. The software is a linkable module compatible with the industry-standard SINDA/G code. Typical transient impressed heat array data, as well as impressed heat flux statements, commonly found in standard SINDA/G and SINDA85 spacecraft thermal models have been completely eliminated allowing for a general algorithm that correctly impresses steady state and/or transient heat fluxes. When the surface optical properties and areas are multiplied by the heat flux, a heating rate for each surface and corresponding node is calculated. External surface (node) optical properties and areas can be modified to account for material beginning-of-life (BOL) or end-of-life (EOL) conditions by a simple call to a subroutine. These surface property changes are reflected in the heating rate calculations and corresponding radiation conductors for a given surface and SINDA node. The automated variation of Sun angles, spacecraft attitudes, and surface property conditions as a function of analysis case provides a powerful tool for analyzing the range of mission scenarios in a single batch computer run. The benefits in terms of time savings, improved accuracy due to the elimination of potential human error, and ease of use are substantial.