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The current Extravehicular Mobility Unit (EMU) system provides thermal control using a sublimator to reject both the heat produced by the astronaut's metabolic activity as well as the heat produced by the Portable Life Support Unit (PLSS). This sublimator vents up to eight pounds of water each Extravehicular Activity (EVA). If this load could be radiated to space, the amount of water that would need to be sublimated could be greatly reduced. There is enough surface area on the EMU that almost all of the heat can be rejected by radiation. Radiators, however, reject heat at a relatively constant rate, while the astronaut generates heat at a variable rate. To accommodate this variable heat load, NASA is developing a new freeze tolerant radiator where the tubes can selectively freeze to “turn down” the radiator and adjust to the heat rejection requirement. This radiator design significantly reduces the amount of expendable water needed for the sublimator.

TDA Research, Inc (TDA) is developing a compact lightweight emergency system that provides 30–minute life–support in the case of system or component failure in the Portable Life Support System (PLSS). This emergency system is based on a regenerable sorbent technology developed at TDA, which removes carbon dioxide (CO2) and moisture (H2O). The emergency Extravehicular Activity (EVA) system must control CO2 levels as well as humidity and temperature. Two thermal sources that must be managed are the metabolic heat from the astronaut, mostly in the form of water vapor and the heat released from the exothermic reaction of CO2 and H2O with the sorbent. Consideration of the thermal management is critical in the design of this system because it affects sorbent performance. Additionally, it is important in maintaining astronaut comfort.