Review and Assessment of JPL's Thermal Margins

NASA’s Jet Propulsion Laboratory has captured its experience from five decades of robotic space exploration into a set of design rules. These rules have gradually transformed into explicit requirements and are now formally implemented and verified. Over an extended period of time, the initial understanding of the intent and rationale for these rules has faded and the rules are now frequently applied without further consideration. In the meantime, mission classes and their associated risk postures have evolved, coupled with tightened resource constraints and growing design diversity, bringing into question the current “one size fits all” thermal margin approach. This paper provides a systematic review of the requirements, methods, and issues involved with thermal design along the heat flow path - from the junction of an electronic part to the eventual rejection of heat to space. The work resulted in a renewed understanding of the intent behind JPL requirements for hot thermal margins and a framework for relevant considerations, which will enable better decision making when a deviation to these requirements is considered.