Mechanically Pumped Fluid Loop Technologies for Thermal Control of Future Mars Rovers

Future planetary science missions planned for Mars are expected to be more complex and thermally challenging than any of the previous missions. For future rovers, the operational parameters such as landing site latitudes, mission life, distance traversed, and rover thermal energy to be managed will be significantly higher (two to five times) than the previous missions. It is a very challenging problem to provide an effective thermal control for the future rovers using traditional passive thermal control technologies. Recent investigations at the Jet Propulsion Laboratory (JPL) have shown that mechanical pump based fluid loops provide a robust and effective thermal control system needed for these future rovers. Mechanical pump based fluid loop (MPFL) technologies are currently being developed at JPL for use on such rovers. These fluid loops are planned for use during spacecraft cruise from earth to Mars and also on the Martian surface operations. These technologies include those related to mechanical pumps, working fluids, thermal control valves, mechanical fittings, and tube materials used in the fluid loops. Currently CFC-11 is being investigated for moderate temperature operation (-100 to +100 C) with various pumps, tube materials, and thermal control valves. Several test loops have been set up and are being operated at JPL to evaluate the life and performance of these fluid loop components. Material and chemical tests are being conducted to evaluate compatibility of the fluid loop material with long-term exposure to the working fluid at elevated temperatures. The paper describes the results from the life test on pumps operating in CFC-11 at room temperature and at 100 C. The performance of the various fluid loop components and the integrity of the fluid and tube materials over time of the life test are described. The results from chemical compatibility tests on materials exposed to CFC-11 at 100 C over a period of 18-months are also presented.