Continued Development of Advanced Sorbents for Improved RCA Performance

NASA has a strong interest in improving the method to control carbon dioxide (CO2) and humidity in the Exploration Extravehicular Mobility Unit (xEMU). Historically, the MetOx has been used to remove CO2 from the Extravehicular Mobility Unit (EMU). However, this unit utilizes a solid silver oxide sorbent which has a finite capacity and requires maintenance for thermal regeneration between extravehicular activity (EVA) missions. The technology currently planned to replace the MetOx in the xEMU is the Rapid Cycle Amine (RCA). This device utilizes a regenerable, pressure swing adsorption system which consists of two beds that alternate between adsorption of CO2 and H2O and desorption of said compounds through exposure to space vacuum. The RCA currently utilizes an amine-based sorbent to perform this function designated as SA9T. While this sorbent has significant reversible CO2 uptakes, an increase in these uptake capacities would enable the reduction of the RCA mass, volume, and power consumption while also enabling lower CO2 levels in the xEMU. In addition, the current sorbent emits low levels of ammonia which must be removed from the suit using a separate technology, and a reduction of these emission levels is desirable.

In an ongoing SBIR Phase II project, Reaction Systems developed new sorbents that have the potential to improve the performance of the RCA. Reaction Systems used a rapid screening testing method along with its expertise in the development of CO2 sorbents to identify materials that have potential to outperform SA9T. In this project, Reaction Systems tested the performance of the sorbents under realistic conditions using a twin bed CO2 control module in a full-scale ventilation loop simulator and characterized the sorbent cycle times as a function of CO2 partial pressure. These sorbents also emit less ammonia than a sorbent that has a similar composition as SA9T.