A Mobile Liquid Venting Membrane Separator for Carbon Dioxide, Humidity, and Waste Heat Removal from Spacesuits and Manned Spacecraft

Current spacesuit life support systems use consumable absorbents for carbon dioxide and odor control, condensing heat exchangers and high-speed rotary separators for humidity control, and easily-contaminated water-ice sublimators for waste heat removal, resulting in complex hardware with high consumables/power usage and maintenance. The Mobile Liquid Venting Membrane Separator (VMS) performs these life support functions with low logistics penalties. It exploits pressure-swing absorption and temperature-controlled evaporation to transport carbon dioxide, humidity, odor, and waste heat to space vacuum. The Mobile Liquid VMS removes carbon dioxide, humidity, and odors from air by absorption into a hydrophilic liquid circulating around a solvent loop. Waste heat is transferred from thermal sources into the solvent loop through a heat exchanger. Carbon dioxide and odors are desorbed and water is evaporated from the solvent loop to space vacuum via a flow-control valve; net water lost from the loop is replaced from a reservoir. Since the Mobile Liquid VMS uses a working fluid with very low oxygen and nitrogen solubility, air loss to vacuum is negligible. Since carbon dioxide and water vapor are vented to space vacuum and not processed exothermally within the spacesuit, it significantly lowers heat load and cooling water usage. The air/liquid and liquid/vacuum interfaces in the Mobile Liquid VMS are formed by microporous hydrophobic hollow fiber modules (HFMs). Solvent liquid flows through thousands of hollow fibers and gases are transferred to/from this liquid through the microporous fiber walls; the hydrophilic solvent does not enter the pores of the hydrophobic fiber wall material. These HFMs have very high volume-specific surface area, resulting in high gas-liquid mass transfer rates in a minimal volume. The Mobile Liquid VMS has been tested for over 200 hours at a laboratory scale and has demonstrated carbon dioxide, humidity, and waste heat removal capability. Calculation indicates that it should also remove all expected odors from spacesuit air, but this capability has not been demonstrated to date.