Thermal Amine Scrubber-- Operational Status, Optimization & Improvements

The carbon dioxide (CO2) removal flight experiment known as "Thermal Amine Scrubber" (TAS), developed collaboratively by Collins Aerospace and Johnson Space Center, has been operating and scrubbing metabolically produced CO2 from the International Space Station (ISS) over the past 3 years. Since publication of the previous ICES paper, TAS has demonstrated CO2 removal performance close to exploration mission goals and there have been multiple lessons learned for more reliable and effective operation of TAS in the ISS flight environment. Efforts to optimize on-orbit CO2 scrubbing capabilities have included adjustments to system valve programming and CO2 bed thermal cycle characteristics, installation of new hardware for enhanced metrics on performance, and redesign of the system process air blower to yield additional flow-DP performance using the CST-100 fan controller. New hardware including (1) a spare Bulk Water Save valve assembly, (2) inlet and cabin CO2 sensors, and (3) a product CO2 sampling assembly were developed, built, tested, and delivered for launch on Northrop Grumman-14 (NG-14) (1 and 2) and SpaceX-21 (SpX-21) (3), respectively. These components were installed in the payload by crew on the ISS at the end of 2020. In 2021, additional spare hardware was launched on NG-16 and SpX-23, including a new Desiccant Wheel Assembly with an improved gearbox assembly which was installed and activated in September 2021. Anomaly investigations and lessons learned are also discussed including an undersized valve drive motor gear-set and ball valve leakage issue which suspended operation for periods of time. Lastly, further candidate enhancements will be identified along with plans for continued operation of TAS.