In order to conserve mass and volume, it was proposed that the International Space Station (ISS) control the level of carbon dioxide (CO2) in the Space Shuttle Orbiter while the Orbiter is docked to the ISS. If successful, this would greatly reduce the number of lithium hydroxide (LiOH) canisters required for each ISS-related Orbiter mission.
Because of the impact on the Orbiter Environmental Control and Life Support Subsystem (ECLSS), as well as on the Orbiter flight manifest, a Space Shuttle Program (SSP) analysis was necessary.
STS-108 (ISS UF1) pre-flight analysis using the Personal Computer Thermal Analyzer Program (PCTAP) predicted that the ISS would be able to control the level of CO2 in the Orbiter (and throughout the stack) under nominal conditions with no supplemental LiOH required. This analysis assumed that the Carbon Dioxide Removal Assembly (CDRA) located in the U.S. Lab would be operating in its off-nominal “single bed” mode, and that the Vozdukh CO2 removal system located in the Service Module would be in its highest performance mode of operation.
Post-flight analysis was also conducted in order to fine-tune and expand the pre-flight analysis.
This paper will assess the assumptions and predictions of the PCTAP analysis, explain any discrepancies between the analysis and flight data, provide suggestions for improvement of the analysis, make predictions for future flights based on changes in Environmental Control and Life Support (ECLS) hardware performance or system configuration, and suggest performance improvements for future missions.