Analysis on the Effect of Flow Interruption in the Oxygen Ventilation Loop on Inspired Carbon Dioxide



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51st International Conference on Environmental Systems


The Oxygen Ventilation Loop (OVL) of the Exploration Portable Life Support Subsystem (xPLSS) provides oxygen gas (O2) and removes water (H-2O) and carbon dioxide (CO2) from the Exploration Extravehicular Mobility Unit (xEMU). The Rapid Cycle Amine (RCA) uses two cycling beds to remove CO2 and H2O from the OVL. Flow through the OVL is interrupted when the RCA switches between the two beds. This paper discusses an analysis conducted to determine the impact of the OVL flow interruption on the inspired partial pressure of CO2 (ppCO2). The analysis uses a computational fluid dynamics (CFD) model of the upper portion of the Exploration Pressure Garment Subsystem (xPGS) to determine the ppCO2 inspired by the crewmember during the flow interruption. The impact of various parameters on the inspiration of elevated ppCO2 by the crewmember is analyzed. This analysis shows that flow interruption in the OVL causes the first inhale after the interruption to have elevated ppCO2. However, the inspired ppCO2 returns to near nominal values by the second inhale, so the impact of flow interruption on the average ppCO2 is small. The effect of the flow interruption is most significant with high metabolic rates and long flow interruption times.


Noah Andersen, HX5, LLC, US
ICES402: Extravehicular Activity: PLSS Systems
The 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.


PLSS, Oxygen Ventilation Loop, Flow Interruption, Inspired CO2, Rapid Cycle Amine, Computational Fluid Dynamics, CFD, PICO2, xEMU, CO2 Washout, RCA