CO2 Removal with Enhanced Molecular Sieves

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.