In the closed environment of an inhabited spacecraft, a critical aspect of the air revitalization system is the removal of the carbon dioxide (CO2) and water vapor produced by the crew. A number of different techniques can be used for CO2 removal, but current methods are either non-regenerative or require a relatively high power input for thermal regeneration.
Two-bed CO2 adsorption systems that can remove CO2 from humid air and be regenerated using pressure-swing desorption offer mass, volume, and power advantages when compared with the other methods. Two classes of sorbent materials show particular promise for this application:
Zeolite sorbents, similar to those in the International Space Station (ISS) CO2 removal assembly
Functionalized carbon molecular sieves (FCMS), which adsorb CO2 independent of the humidity in the airstream
Pressure-swing testing of these two different sorbents under both space station and space suit conditions are currently underway. Results obtained to date, from zeolites under space station conditions and FCMS under suit conditions, indicate that a pressure-swing CO2 removal system is a competitive solution for both life-support applications.