Topic

This subtopic is soliciting development of systems to fill the base functions of an advanced portable life support system for extravehicular activity (EVA) suits on the Martian surface which could also be applicable to the lunar surface. It seeks to address deficits with previous developments as it relates to the base portable life support system (PLSS) functions: thermal control, O2 supply, CO2 removal systems, humidity control, and power supply. This list is in prioritized order based on the gap between current state of art (SOA) and estimated need for the Martian surface. -Thermal control: Current SOA thermal control philosophy is to isolate the crew from the thermal environment as much as possible, use the metabolic and waste heat to warm the crew member, and reject excess heat to the environment. Isolation of the crew from the thermal environment may not be possible in the atmosphere of Mars, with pressures between 0.09 and 0.17 PSIA and temperatures between 68°F and -220°F. Viable proposals for this include but are not limited to: advanced insulative materials, evaporative coolers, phase change material, low power/mass heating schemes, variable emissivity radiators. -O2 supply: Current SOA O2 supply relies on high pressure gaseous oxygen tanks. Recent work has suggested that liquid oxygen may be able to reduce on back mass, however this is of a much lower TRL. Viable proposals include but are not limited to liquid oxygen (LOX) systems that will work in reduced gravity, cryogenic liquid expanders that will keep up with both nominal metabolic use 0.4 g/min -4 g/min (400 BTU/hr to 3000 BTU/hr) and purge operations (7-15 g/min), and safety systems for LOX. System should be sized for 1.9 g/min consumption on average across 8 hours. -CO2 Control: Current SOA for CO2 control in spacesuits requires rejection of CO2 to the atmosphere, which will not be practical under Martian pressures (0.09 and 0.17 PSIA and 95% CO2). Viable solutions include both systems that can sequester CO2 until return to the habitat or systems that can reject CO2 to the high CO2 atmosphere. The systems should be capable of removing CO2 from the vent stream flowing at 6 ACFM and 4.3 PSI, with injection rates between 0.5 g/min and 4.35 g/min, with an average of 2.2 g/min for 8 hours. -Humidity Control: Historically condensing heat exchangers have been used, as the CO2 system generated additional water. Current SOA CO2 technology removes water as it removes CO2, however this system must be adjusted for the Martian atmosphere. Viable humidity control scheme must either be a part of the CO2 control or integrate independently with a wide range of potential CO2 technologies. Additional proposals in the areas of EVA consumables reduction and planetary protection will be considered. Given the increased gravity of Mars compared to the lunar surface or deep space, minimizing total on back mass and volume will be critical in technology viability. Minimizing mass and volume can be a result of technological developments and lightweight advanced materials selection.