Mars Exploration Rover Surface Mission Flight Thermal Performance

Abstract

NASA launched two rovers in June and July of 2003 as a part of the Mars Exploration Rover (MER) project. MER-A (Spirit) landed on Mars in Gusev Crater at 15 degrees South latitude and 175 degree East longitude on January 4, 2004 (Squyres, et al., Dec. 2004)). MER-B (Opportunity) landed on Mars in Terra Meridiani at 2 degrees South latitude and 354 degrees East longitude on January 25, 2004 (Squyres, et al., August 2004) Both rovers have well exceeded their design lifetime (90 Sols) by more than a factor of 4. Spirit and Opportunity are still healthy and continue to execute their roving science missions at the time of this writing. This paper discusses rover flight thermal performance during the surface missions of both vehicles, covering roughly the time from the MER-A landing in late Southern Summer (Ls = 328, Sol 1A) through the Southern Winter solstice (Ls = 90, Sol 255A) to nearly Southern Vernal equinox (Ls = 160 , Sol 398A). This paper describes the MER rover thermal design, its implementation and performance on Mars. The rover surface thermal design performance was better than pre-landing predictions. The very successful thermal design allowed a high level of communications immediately after landing without overheating and required a minimal amount of survival heating in the dead of winter. An analytical thermal model developed for the rover was used to predict surface operations performance. A reduced-node version of this model was integrated into the mission planning tool to achieve the proper balance between: 1) desired science and communications operating profile, 2) available energy from the power system and 3) temperature limits prescribed for the hardware. One of the more challenging thermal problems during surface operations, predicting the performance of actuator and camera electronics warmup heaters, was automated by using heater lookup tables that were periodically updated based on flight telemetry. Specific MER rover thermal flight experiences are discussed in this paper. Lessons learned and suggestions for improvement of future Mars surface vehicle designs are presented.

Efficient thermal management of Li-ion batteries with a passive interfacial thermal regulator based on a shape memory alloy

“…The concept of a thermal regulator has existed for decades, but applications have been limited to a few niche markets such as thermal regulation in spaceships [17,18] and cryogenic systems [19], despite growing interest from other fields in recent years [20]. The main issues with current thermal regulators are low switch ratio (SR), large footprint, high cost, and poor cyclability.…”

“…This class of regulators typically exhibit good abruptness (thermal conductance vs. temperature approximating a step function rather than a gentle slope) due to the sharp nature of phase change, but has yet to demonstrate a sufficiently high SR for the present battery application. Another class of thermal regulators is based on opening and closing a macroscopic interface, which have shown much higher SR (~100:1 around room temperature) and seen more practical utility [17,18,29]. This type of regulator typically relies on the differential thermal expansion ( ) between two different materials to induce a geometric change and exploits the strongly nonlinear behavior of thermal conductance when the interfacial gap closes and becomes a pressure contact.…”

Research and Development of Heat Switch for Future Space Missions

“…Even when mechanical heat switches are only considered, there are different types of mechanical parts: paraffin-actuated, shape memory 4) , using two different CTE (Coefficient of Thermal Expansion) materials 5,6) . Recently, paraffin-actuated heat switches were used for temperature controls of battery systems in the Mars exploration rover Spirit and Opportunity 7) . On the other hand, gas gap heat switches were used for heat rejection from compressors of a 20K hydrogen sorption cooler in the cosmic microwave background observation Planck 8,9) .…”

“…Comparison of heat switch. 1) Mars rover (spirit, opportunity)7) , 2) Starsys Inc 1) ,. 3) Vapor modulated loop heat pipe developed by IberEspacio16) .…”

Thermal Insulators' Performances in Simulated Mars Environment

“…In these conditions, gas gaps can be successfully implemented whenever convection is inhibited [1,2], Transition between the outstanding performances of space thermal insulators in vacuum and their mild characteristics in presence of an atmospheric gas is strictly depending on the insulator structure and gas characteristics and is hard to model. In presence of an atmospheric gas, MLI insulating performances at "high pressures" are almost constant and insulators at best trap the gas.…”