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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.

In order to meet microbial reduction requirements for all Mars in-situ life detection and sample return missions, entire planetary spacecraft (including planetary entry probes and planetary landing capsules) may have to be exposed to a qualified sterilization process. At JPL, we are developing a low temperature (~45°C) vapor phase hydrogen peroxide sterilization process. This process is currently being used by the medical industry and its effectiveness is well established. In order to effectively and safely apply this technology to sterilize a spacecraft, which is made out of various man-made materials and electronic circuit boards, the following technical issues need to be resolved: 1. Efficacy of sterilization process. 2. Diffusion of H2O2 under sterilization process conditions into hard to reach places. 3. Materials and components compatibility with the sterilization process. 4. Development of methodology to protect (isolate) sensitive components (i.e. electronic ) from H2O2 vapor.

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.

The Mars Science Laboratory (MSL1) mission to land a large rover on Mars is being planned for Launch in 2009. As currently conceived, the rover would use a Multi-mission Radioisotope Thermoelectric Generator (MMRTG) to generate about 110 W of electrical power for use in the rover and the science payload. Usage of an MMRTG allows for a large amount of nearly constant electrical power to be generated day and night for all seasons (year around) and latitudes. This offers a large advantage over solar arrays. The MMRTG by its nature dissipates about 2000 W of waste heat. The basic architecture of the thermal system utilizes this waste heat on the surface of Mars to maintain the rover's temperatures within their limits under all conditions. In addition, during cruise, this waste heat needs to be dissipated safely to protect sensitive components in the spacecraft and the rover.

Mars Exploration Rover (MER) mission launched two spacecraft to Mars in June and July of 2003 and landed two rovers on Mars in January 2004. A Heat Rejection System (HRS) based on a mechanically pumped single-phase liquid cooling system was used to reject heat from electronics to space during the seven months cruise from Earth to Mars. Even though most of this HRS design was similar to the system used on Mars Pathfinder in 1996, several key modifications were made in the MER HRS design. These included the heat exchanger used in removing the heat from electronics, design of venting system used to vent the liquid prior to Mars entry, inclusion of pressure transducer in the HRS, and the spacecraft radiator design. Extensive thermal/fluids modeling and analysis were performed on the MER HRS design to verify the performance and reliability of the system. The HRS design and performance was verified during the spacecraft system thermal vacuum tests.

Passively activated thermal control valves were developed for use in a mechanically pumped single-phase fluid liquid loop (MPFL) of the Mars Science Laboratory (MSL) rover. A key approach to the thermal control of the rover with the fluid loop is to control the flow through the rover's heat generating or heat rejecting components. This is achieved by either splitting or mixing the fluid stream coming from different branches of the system at different temperatures; actively or passively controlled flow valves are typically used for such purposes. To meet the thermal control requirements of the Mars Science Laboratory (MSL) rover, a splitting and a mixing thermal control valves with gradual control capabilities using a linear thermal actuator and a spool was developed at Jet Propulsion Laboratory (JPL). The key feature of these control valves is the balancing of the flow through the various branches of the fluid loop in order to balance the heat loads of the whole thermal system.