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The US Space Shuttle on-orbit waste heat rejection is currently accomplished through a combination of radiators and a Flash Evaporator System (FES). Three of the FES units have been rebuilt to date owing to corrosion problems. In addition, the FES has experienced freeze-ups on-orbit. As part of NASA's Orbiter Upgrade Program, a Water Membrane Evaporator (WME) is being developed as a replacement for the FES. The WME will be installed on the Space Shuttle starting in the fall of 2001. It will use hydrophobic micropore membrane technology to passively control a water liquid/vapor interface. Waste heat that will be acquired from the Orbiter Freon-21 coolant loops will evaporate water at the interface. The water vapor will pass through the membrane and be vented to space. The WME program takes advantage of the recent advances in hydrophobic micropore membrane technology to provide a simpler and more robust heat rejection device than the current FES.

As part of NASA’s TransHab inflatable habitat program, a Radiation Shield Water Tank (RSWT) is being developed to provide a safe haven from peak solar particle events. The RSWT will provide an 11 ft. (3.35 m) diameter by 7 ft. (2.13 m) tall “safe haven” with a 2.26 in. (0.0574 m) thick wall of water for astronaut residence during peak solar events. The RSWT also functions as a water processing storage tank and must be capable of being filled and drained at will. Because of the unique shape of the RSWT, standard bellows and bladder designs cannot be used for inventory control. Therefore NASA has developed a bladderless tank where capillary forces govern the positioning of the liquid inventory. A combination of hydrophobic and hydrophilic membranes and wetting surfaces allows the tank to be filled and emptied as desired. In the present work, background on space-borne radiation is presented, the bladderless RSWT concept is described, and its theory of operation is discussed.