Thermal Architecture and Design of the Cruise Heat Rejection System of Mars Sample Retrieval Lander

NASA and the European Space Agency are planning a Mars Sample Return campaign that would bring Martian regolith and rock samples, collected and cached in tubes by the Perseverance rover, back to Earth for scientific investigation. The Mars Sample Retrieval Lander (SRL) would carry the Mars Ascent Vehicle (MAV) that would launch samples tubes into Mars orbit to be collected by an Earth Return Orbiter (ERO) and placed into an Earth Entry Vehicle (EEV) for return and landing on Earth. The current baseline design of the SRL spacecraft uses a mechanically pumped fluid loop as primary means of thermal control during cruise to Mars. The heat rejection system (HRS) would be similar to those on previous JPL missions such as Mars Pathfinder, Mars Exploration Rovers, Mars Science Laboratory, Mars 2020, and Europa Clipper. It uses a centrifugal pump to circulate CFC-11 working fluid through the system. The fluid picks up heat from the lander and the cruise avionics and rejects it to radiators located on the cruise stage. The HRS also uses a thermal control valve to modulate fluid flow to the radiator and control heat rejection rate by the system in response to variation in heat dissipation from the avionics as well as changes in the thermal environment. The loop services hardware with varying temperature limits making it challenging to accommodate hardware on the loop with different temperature limits. Heat exchanging would be achieved through the use of flanged tubing bonded to the lander avionics module plate that hosts all the avionics and the battery. This paper discusses the tradeoffs performed before choosing a mechanical pumped loop as the thermal control system. It also describes the analysis, design, and predicted performance of this system.