International Space Station (ISS) Extravehicular Activity (EVA) Gas Usage

International Space Station (ISS) Crewmembers perform one of three denitrogenation protocols prior to performing Extravehicular Activities (EVAs) using the International Space Station (ISS) Airlock. The three denitrogenation protocols are: a) Exercise, b) Campout, and c) In-suit. EVA gas usage is categorized into Denitrogenation, Extravehicular Mobility Unit (EMU) oxygen use during EVAs, and air loss gas usage. The amount of gas usage depends on the denitrogenation protocol that is used. Each protocol's gas usage will differ as a result of different requirements of denitrogenation and EMU support. Flight data is correlated with theoretical values when it is available. The correlation to flight data provides a validation of the analysis data.

Theoretical and actual gas usages from the ISS were calculated for EVAs out of the Airlock during Stage 7A to Stage 11A. Components of denitrogenation and EMU support gas usage are included. These components include quick donning mask, EMU purge, EMU prebreathe, EMU fill, and partial pressure control support. The amount of air loss experienced during the depressurization of the ISS Airlock Crewlock to space is also included.