Passive no moving parts capillary solutions for spacecraft life support systems

Life support systems for plant, animal, and crew habitats are replete with the challenges of managing poorly wetting aqueous solutions in a low-g environment. A brief review of noteworthy on-orbit system failures provides ample renewed motivation to understand microgravity capillary phenomena to the point such failures may be avoided in the future. Historic and recent NASA-funded low-g experiments are highlighted that greatly expand our experience base and comfort level to prepare for and preferably exploit capillary forces. Our specific aim is to replace the passive role of gravity on earth with the combined passive roles of surface tension, wetting, and container geometry in space. We demonstrate a general approach highlighting high-TRL examples pertinent to urine collection and processing. From this specific example we demonstrate more specific applications to passive in-line separator devices, beverage cups, and bio-sample de-bubblers. Broader applications can be made to other challenging processes such as brine drying, condensing heat exchangers, liquid sorbent CO2 scrubbers, wet lab unit operations, and habitats for plants and animals.