Molecular Sieve CO2 Removal Systems: International Space Station and Lunar-Mars Life Support Test Project

Molecular sieve carbon dioxide removal systems are a proven and reliable method for the control of carbon dioxide in a closed environment. Carbon dioxide control was provided by a molecular sieve unit for Skylab. Currently, the carbon dioxide removal assembly (CDRA) is being manufactured by AlliedSignal for Boeing and will be utilized for carbon dioxide removal on the International Space Station (ISS). Development testing has been performed on CDRA and different power saving operation modes have been investigated. Also as part of the Lunar-Mars Life Support Test Project (LMLSTP) initiative, a research four-bed molecular sieve (4BMS) system has been tested at NASA Johnson Space Center. The most recent test was Phase IIA, which was a 60-day test that focused on integration testing of representative ISS hardware with four humans living inside a closed chamber. The purpose of this paper is to discuss results from development testing of ISS CDRA, the 4BMS results from the LMLSTP 60-day test, and to describe the differences between the ISS CDRA and the LMLSTP 4BMS.