Lithium Chloride Absorber Radiator for Mars Exploration

Life support systems for Mars exploration space suits will face challenging requirements for heat rejection. These systems must be light weight, compact, rugged, make minimal use of consumables, and have low impact on the Martian environment. Thermal control will be particularly challenging because water venting should be minimized. Lithium Chloride Absorber Radiator (LCAR) technology can provide thermal control with very low water venting, but earlier designs were not intended for use on the Martian surface. To reject heat to the relatively warm Martian surface, the LCAR must operate at higher vapor pressure and LiCl concentrations than prior designs. We have shown the feasibility of an innovative LCAR system that can meet requirements for operation on Mars. The system includes an innovative water vapor compressor based on proven miniature vacuum pump technology. This device will compress water vapor from the SWME and enable the LCAR to operate at temperatures up to 80°C. Compared to prior systems, the Mars LCAR will be slightly thicker with increased LiCl loading that will reduce the concentration swing during an EVA and increase its final operating temperature. We demonstrated the feasibility of this approach by producing a detailed design of the innovative two-stage vapor compressor, predicting its performance, and showing that the compressor will enable high cooling rates and high heat rejection temperatures. We demonstrated that the Mars LCAR panel can survive representative impact loads without losing containment of LiCl solution. Finally, we measured the heat rejection capability of a prototypical LCAR panel in thermal vacuum tests that simulate operation on the Martian surface and confirmed high heat rejection rates and capacity.