According to Flightglobal, a fluid that can operate within and outside the warm confines of a spacecraft's habitable volume is the goal of ongoing NASA thermal control work for its Constellation exploration systems programme. The fluid would be part of an active thermal control system to help create a suitable environment for crew and equipment on board the Orion crew exploration vehicle or lunar lander.

Historically thermal control systems have used fluid loops with cold plates to collect, transfer and reject waste heat from sources including crew life support, avionics, motors and refrigeration systems. An internal fluid loop exchanges heat with an external fluid loop, and on the Space Shuttle and International Space Station this means water internally and freon or ammonia externally. "A single failure could allow fluids to mix," says NASA, which wants to use a single fluid for internal collection and external rejection of the heat.

One candidate for the all-purpose fluid is a combination of 60% propylene glycol and 40% water. This is said to have low toxicity, and does not cause aluminium to corrode, but has a high viscosity at low temperatures.Research with alternative glycols has included flammability, compatibility with life-support equipment, potential for microbial activity, materials compatibility and low-temperature performance. Researchers are also investigating composite cold plates, multifunction vehicle structures that can act as cold plates, and related thermal interface materials.

As well as NASA's Glenn Research Center and Johnson Space Center, its Goddard Space Flight Center and Jet Propulsion Laboratory are involved with industrial participants that include, Hamilton Sundstrand, Jacobs-Sverdrup, Mainstream, Oceaneering Space Systems and Sundanzer.

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