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The Oxygen Generator Subsystem (OGS) on the next Mars Lander will demonstrate the production of oxygen from Martian atmospheric carbon dioxide using solid oxide electrolysis. The electrolyzer in OGS is based on a Yttria Stabilized Zirconia electrolyte and operates at 750°C. The electrolyzer is thermally cycled during every sol of operation between Mars ambient and operating temperature with a maximum of 15W electrical power. A package for this electrolyzer has been designed, built, and tested. It meets all the requirements of this experiment and weighs only slightly more than 1kg.

This paper explores the possibilities of cooling a permanently inhabited lunar base with a reverse Brayton cycle Thermal Control System (TCS). Based on an initial stage outpost, the cooling needs are defined. A thermodynamic performance model for the Brayton cycle is derived using ideal gas analysis. This model includes inefficiencies and irreversibilities of the components. The free parameters in the thermodynamic model are successively removed using limiting values for efficiencies and determining operating parameters by suboptimizations. In essence a model for cooling efficiency as a function of rejection temperature alone is obtained. For every component of the system a mass model is applied and the overall mass is determined. The last remaining degree of freedom, the rejection temperature, is eliminated by an optimization for lowest overall mass. The result for minimal TCS mass is compared to a reference TCS using a Rankine cycle.

A parametric analysis is performed to compare different heat pump based thermal control systems for a Lunar Base. Rankine cycle and absorption cycle heat pumps are compared and optimized for a 100 kW cooling load. Variables include the use or lack of an interface heat exchanger, and different operating fluids. Optimization of system mass to radiator rejection temperature is performed. The results indicate a relatively small sensitivity of Rankine cycle system mass to these variables, with optimized system masses of about 6000 kg for the 100 kW thermal load. It is quantitatively demonstrated that absorption based systems are not mass competitive with Rankine systems.