Maintaining Adequate Carbon Dioxide Washout for an Advanced Extravehicular Mobility Unit

摘要

Over the past several years, NASA has realized tremendous progress in technology development that is aimed at the production of an Advanced Extravehicular Mobility Unit (AEMU). Of the many functions provided by the spacesuit and portable life support system (PLSS) within the AEMU, delivering breathing gas to the astronaut along with removing carbon dioxide (CO_2) remains one of the most important environmental functions that the AEMU can control. Carbon dioxide washout is the capability of the ventilation flow in the spacesuit helmet to limit the concentration of CO_2 inhaled by the crew member to meet breathing requirements. CO_2 washout performance is a critical parameter needed to ens ure proper and robust designs that are insensitive to human variabilities in a spacesuit and in vehicle applications such as sleep stations and hygiene compartments. Human testing is a key tool used to evaluate and validate CO_2 washout performance but is also expensive due to the levied safety requirements. Moreover, correlation of math models becomes challenging because of human variability and movement To supplement human CO_2 washout testing, a breathing capability is being planned that will be integrated into a suited manikin test apparatus to provide a safe, lower cost, stable, easily modeled alternative to human testing. Additionally, this configuration provides NASA Johnson Space Center (JSC) the capability to evaluate CO_2 washout under off-nominal conditions that would otherwise be unsafe for human testing or difficult due to fatigue of a test subject Human testing has been under way in-house at JSC and analysis has been initiated to evaluate whether the AEMU technology provides sufficient performance in ensuring that the CO_2 is removed sufficiently and the ventilation flow is adequate for maintaining CO_2 washout in the AEMU spacesuit helmet of the crew member during an extravehicular activity. This paper will review recent CO_2 washout testing and analysis activities, planned in-house testing with a spacesuit simulator, and the associated analytical work along with insights from the medical aspecton the testing.