Design and Evaluation of Regenerable Trace Contaminant Control for Advanced Portable Life Support System
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Trace contaminants that are introduced into the ventilation loop of a spacesuit via metabolic processes, off-gassing of spacesuit materials, and by-products of the amine used in the Rapid Cycle Amine (RCA) system can be removed using activated charcoal. Based on a previous study performed by NASA, the use of a Trace Contaminant Control (TCC) device is necessary in the Portable Life Support System (PLSS) ventilation loop to control ammonia and formaldehyde from potentially exceeding their Spacecraft Maximum Allowable Concentration (SMAC) levels. Although effective, the drawbacks of using activated charcoal as the TCC sorbent bed are a bulky system with low regeneration capability, a reliance on consumables, significant power consumption, and consequently high associated life cycle operating cost. The charcoal bed cannot be regenerated solely by vacuum, and thus has to be regenerated on-base at the end of Extravehicular Activity (EVA) mission. It typically requires heat treatment along with a sweep gas or vacuum to remove the desorbed contaminants. Precision Combustion, Inc. (PCI) has been developing and evaluating regenerable adsorber technologies for capturing ammonia and formaldehyde for spacesuit applications. The first technology is derived from more conventional, zeolite-based sorbents and the second technology is based on new functionalized nanomaterials. The new technology is developed using PCI’s novel adsorbent nanomaterials that have high surface area and can be designed to achieve uniquely-targeted sorbent properties including minimizing competitive sorption with water and CO2 as well as vacuum regenerability without heating. Both the zeolite-based sorbents and the functionalized nanomaterials were applied on ultra-short channel length Microlith® substrates to permit practical implementation of the sorbent for a vacuum swing regenerable TCC device. Here, the performance metrics and operational requirements from each technology will be presented and compared. These include results from performance testing at PLSS operating conditions, including removal efficiency, regenerability, and multi-cycle testing.