Continuously Regenerable Freeze-Out CO
Carbon dioxide (CO2) removal technology development for portable life support systems (PLSS) has traditionally concentrated in the areas of solid and liquid chemical sorbents and semi-permeable membranes. Most of these systems are too heavy in gravity environments, require prohibitive amounts of consumables for operation on long term planetary missions, or are inoperable on the surface of Mars due to the presence of a CO2 atmosphere. This paper describes the effort performed to mature an innovative CO2 removal technology that meets NASA's planetary mission needs while adhering to the important guiding principles of simplicity, reliability, and operability.
A breadboard cryogenic carbon dioxide scrubber for an ejector-based cryogenic PLSS was developed, designed, and tested. The scrubber freezes CO2 and other trace contaminants out of expired ventilation loop gas using cooling available from a liquid oxygen (LOX) based PLSS. The device was designed for continuous regeneration, with solid CO2 being removed from the cold freeze-out surfaces, then sublimated and vented overboard. Continuous regeneration allows indefinite scrubber duration for as long as LOX is available from the PLSS.
Simplicity, reliability, and operability are universally important criteria for critical hardware on long duration Lunar or Mars missions. The cryogenic scrubber breadboard has no moving parts, requires no additional consumables, and uses no electrical power, contributing to its simplicity and reliability. It is easy to use; no operator action is required to prepare, use, or shut down the cryogenic scrubber, and it does not require charging or specific regeneration periods. The versatility of the concept allows for operation on Earth, the Moon, and Mars.
A conceptual design suitable for a PLSS was developed based on the results of the cryogenic scrubber breadboard testing.