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Testing of the International Space Station (ISS) U.S. Laboratory baseline configuration of the Atmosphere Revitalization Subsystem (ARS) by NASA's Marshall Space Flight Center (MSFC) has been conducted as part of the Environmental Control and Life Support System (ECLSS) design and development program. This testing addressed specific questions with respect to the control and performance of the baseline ARS subassemblies in the ISS U.S. Laboratory configuration. The test used pressurized oxygen injection, a mass spectrometric major constituent analyzer (MCA), a four-bed molecular sieve carbon dioxide removal assembly (CDRA), and a trace contaminant control subassembly (TCCS) to maintain the atmospheric composition in a sealed chamber within ISS specifications. Human metabolic processes for a crew of four are simulated according to projected ISS mission timelines. The Integrated ARS Test (IART) builds upon previous integrated ECLSS testing conducted at MSFC between 1987 and 1992.

Analyses have been conducted to assess the capability of the Atmosphere Revitalization Subsystem to control ambient CO2 levels of the Space Station Freedom (SSF). The adequacy of the Carbon Dioxide Removal Assembly (CDRA) performance to meet design requirements has been evaluated. Analyses considered transient effects of crew location and metabolic loading on SSF Restructure configurations. The analyses consisted of computer simulations of on-orbit conditions using both supplier provided and adjusted CO2 removal performance approximations along with derived crew metabolic activities and locations. Results show that while the current performance of the CDRA will maintain CO2 levels within specifications for Man-Tended Operations, it cannot maintain the SSF atmosphere below specifications during Permanently Manned Operations. Potential design options are discussed and other relevant analyses are summarized.

Computer model analysis is an integral part of the space station Environmental Control and Life Support System (ECLSS) development program. Systems level computer models are being developed to address key parameters in the design of the Air Revitalization (AR), Temperature and Humidity Control (THC), and Atmosphere Control and Supply (ACS) subsystems of the space station ECLSS. The models are being used to resolve design issues related to appropriate control methodology, flow distribution schemes, and optimum sequencing of the AR, THC, and ACS components. The Computer Aided Systems Engineering and Analysis (CASE/A) program, in continuing development at the Marshall Space Flight Center (MSFC), is being used to develop these models. Data made available through hardware testing at the MSFC Core Module Integration Facility (CMIF) was used extensively during verification of these models.