Comparison of Metal Oxide Absorbents for Regenerative Carbon Dioxide and Water Vapor Removal for Advanced Portable Life Support Systems 911344

Recent NASA-funded studies of Allied-Signal metal-oxide-based absorbents demonstrated that these absorbents offer a unique capability to remove both metabolic carbon dioxide (CO₂) and water (H₂O) vapor from breathing air; previously, metal oxides were considered only for the removal of CO₂. The concurrent removal of CO₂ and H₂O vapor can simplify the astronaut portable life support system (PLSS) by combining the CO₂ and humidity control functions into one component. A further benefit is that the removal processes are reversible, permitting a regenerative component. Thus, a metal oxide absorbent offers many advantages over the current system, which is nonregenerative and uses separate processes for CO₂ and H₂O vapor removal. These advantages include lower complexity, lower maintenance, and longer life.

The use of metal oxide absorbents for removal of both CO₂ and H₂O vapor in the PLSS is the focus of an ongoing NASA program. Recently, two metal oxide formulations previously shown to have promising CO₂ and H₂O vapor uptake characteristics, durability, and long-term regenerative performance were evaluated in a subscale unit operationally representative of full scale. A mixed metal oxide formulation was found to be superior to silver oxide and was selected for further evaluation in a full-scale closed-loop testing scheduled to begin in August 1991. This paper presents the test results that provide the design basis for a full-scale preprototype unit. This metal oxide system effectively performs the functions of both CO₂ and H₂O vapor removal and will significantly reduce the complexity and maintainability of a PLSS while allowing long-term reuse.