Mars Science Laboratory Mechanically Pumped Fluid Loop for Thermal Control - Design, Implementation, and Testing 2009-01-2437
The Mars Science Laboratory (MSL) mission to land a large rover on Mars is being prepared for Launch in 2011. A Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) on the rover provides an electrical power of 110 W for use in the rover and the science payload. Unlike the solar arrays, MMRTG provides a constant electrical power during both day and night for all seasons (year around) and latitudes. The MMRTG dissipates about 2000 W of waste heat to produce the desired electrical power.
One of the challenges for MSL Rover is the thermal management of the large amount of MMRTG waste heat. During operations on the surface of Mars this heat can be harnessed to maintain the rover and the science payload within their allowable limits during nights and winters without the use of electrical survival heaters. A mechanically pumped fluid loop heat rejection and recovery system (HRS) is used to pick up some of this waste heat and supply it to the rover and payload. During warm conditions, the same HRS works in reverse to pick up the heat dissipated by the rover electronics and payloads and reject it to the Martian environment via radiators. The large heat capacity of the flowing fluid in the HRS also serves to create a nearly isothermal interface temperature for the components controlled by the HRS. During cruise to Mars, the thermal management of the MMRTG waste heat is also a big challenge. A second mechanically pumped fluid loop is used to pick up the MMRTG waste heat and transport it to large radiators on the cruise stage. Both the HRS fluid loops use CFC-11 (Freon) as the working fluid.
Both of these HRS fluid loops pose significant technical challenges in terms of their design, qualification and implementation. The spacecraft and rover are currently going through final testing. The design and implementation of the two HRS fluid loops have been completed during the last three years and the testing of the spacecraft is in progress. This paper describes the HRS design developed to overcome the technical challenges posed by the MSL mission and the results of the tests performed to characterize them. This paper builds on the paper presented at the 2005 International Conference on Environmental Systems in Rome that dealt primarily with the architecture of the HRS for MSL.