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An evaporative heat exchanger system, suitable for rejecting heat in a space environment, has been developed. The system is designed to use water as the evaporant, although other fluids are possible. The major components of the system include an evaporative heat exchanger, water spray nozzles, a back-pressure regulator, a pressurized water supply tank, and appropriate controls. The heat exchanger is a high-performance aircraft-type plate-fin design, with a proprietary hydrophilic coating applied to the evaporant-side flow passages. The hydrophilic coating promotes good contact between the evaporating water and the hot heat transfer surfaces.

A program is being performed to design, fabricate, and test a metal hydride sorption cryocooler system capable of supplying periodic refrigeration at 10 K. The system is intended to cool a focal plane array for a low-earth orbit satellite. The refrigeration is effected by sublimating solid hydrogen at 10 K. The solid hydrogen is produced in a batch process by cooling, solidifying, and subcooling liquid hydrogen formed at 30 K by a Joule-Thomson expansion. The spent hydrogen from the sublimation and Joule-Thomson expansion is absorbed by two metal hydride sorption bed assemblies.

A study is being conducted on the design, development, fabrication, integration, and testing of subsystems for an advanced extravehicular mobility unit portable life support system for evolutionary Space Station Freedom or other applications. The subsystem discussed in this paper is the heat rejection system (HRS). The function of the HRS is to remove metabolic and equipment heat loads and provide a comfortable thermal environment for a crewperson during extravehicular activity. The HRS comprises a radiator and a water evaporator. Use of this HRS results in the venting of the evaporated water. This combination of components, however, offers a significant reduction in water usage compared to a standalone evaporator or sublimator, and a significant reduction in weight compared to nonventing configurations.

A carbon dioxide reduction system is being developed for long-duration manned space missions. The system incorporates a Sabatier methanation reactor, utilizing previously developed catalyst materials, and a hollow fiber membrane unit to separate the products of reaction. Heat produced by the exothermic Sabatier reaction is absorbed by an air stream, which also regulates the reactor temperature to maximize yield. This absorbed heat can be utilized elsewhere in the carbon dioxide management system to reduce power requirements. The Sabatier process combines carbon dioxide and hydrogen to form methane and water. In a manned space environnent, the water is then either electrolyzed to form oxygen for breathing and hydrogen to drive the reaction, or recycled to the potable water system. A computer-based performance model using finite elements has been developed to evaluate reactor design and catalyst performance.

A study is being conducted to design, develop, fabricate, integrate, and test a preprototype coolant loop subsystem for an advanced extravehicular mobility unit portable life support system for Space Station Freedom. The overall function of the coolant loop is to remove metabolic and equipment heat loads and provide a comfortable thermal environment for a crewperson during extravehicular activity. The heat loads are transported by water circulating through a liquid-cooled ventilation garment. The thermal environment is regulated using thermal capacitive and/or radiative control. After use, the system must be capable of regenerating relatively rapidly. The key component in the coolant loop is the thermal sink, which is a completely nonventing unit comprising cold-plate heat exchangers, a radiator to reject a fraction of the generated heat load, and a regenerable thermal storage unit to absorb the remaining heat load. No embedded thermoelectric devices are required.