Flowrate Reduction Analysis of the Ventilation Loop in the Exploration Portable Life Support Subsystem
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The Exploration Portable Life Support Subsystem’s (xPLSS) ventilation loop consists of equipment designed to supply O2 and remove CO2 and H2O from the Exploration Extravehicular Mobility Unit (xEMU). This paper outlines a trade study in order to determine the effects of a change in flowrate throughout the ventilation loop where the areas of concern include the carbon dioxide washout surrounding the crewmember (i.e. the resulting inspired partial pressure of CO2), the fan speed and power, and the O2 ullage lost and power consumed by the Rapid Cycle Amine (RCA). The inspired partial pressure of CO2 is limited by the Johnson Space Center’s Chief Medical Officer’s recommendations. As such, this is the primary pass/fail criteria for this flowrate reduction analysis and is considered when analyzing the CO2 washout results for the xEMU helmet and the hard upper torso (HUT). The results from this study show that a flowrate reduction from 6 acfm to 5 acfm is possible.