Space Suit CO2 Washout During Intravehicular ActivitySpace suit carbon dioxide (CO2) washout refers to the removal of CO2 gas from the oral-nasal area of a suited astronaut's (or crewmember's) helmet using the suit's ventilation system. Inadequate washout of gases can result in diminished mental/cognitive abilities as well as headaches and light headedness. In addition to general discomfort, these ailments can impair an astronaut s ability to perform mission-critical tasks ranging from flying the space vehicle to performing lunar extravehicular activities (EVAs). During design development for NASA s Constellation Program (CxP), conflicting requirements arose between the volume of air flow that the new Orion manned space vehicle is allocated to provide to the suited crewmember and the amount of air required to achieve CO2 washout in a space suit. Historically, space suits receive 6.0 actual cubic feet per minute (acfm) of air flow, which has adequately washed out CO2 for EVAs. For CxP, the Orion vehicle will provide 4.5 acfm of air flow to the suit. A group of subject matter experts (SM Es) among the EVA Systems community came to an early consensus that 4.5 acfm may be acceptable for low metabolic rate activities. However, this value appears very risky for high metabolic rates, hence the need for further analysis and testing. An analysis was performed to validate the 4.5 acfm value and to determine if adequate CO2 washout can be achieved with the new suit helmet design concepts. The analysis included computational fluid dynamic (CFD) modeling cases, which modeled the air flow and breathing characteristics of a human wearing suit helmets. Helmet testing was performed at the National Institute of Occupational Safety and Health (NIOSH) in Pittsburgh, Pennsylvania, to provide a gross-level validation of the CFD models. Although there was not a direct data correlation between the helmet testing and the CFD modeling, the testing data showed trends that are very similar to the CFD modeling. Overall, the analysis yielded results that were better than anticipated, with a few unexpected findings that could not easily be explained. Results indicate that 4.5 acfm is acceptable for CO2 washout and helmet design. This paper summarizes the results of this CO2 washout study.
Document ID
20100022055
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Augustine, Phillip M. (Engineering and Science Contract Group Houston, TX, United States)
Navarro, Moses (Engineering and Science Contract Group Houston, TX, United States)
Conger, Bruce (Engineering and Science Contract Group Houston, TX, United States)
Sargusingh, Miriam M. (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 24, 2013
Publication Date
July 11, 2010
Subject Category
Man/System Technology And Life Support
Report/Patent Number
JSC-CN-20205Report Number: JSC-CN-20205
Meeting Information
Meeting: International Conference on Environmental Sciences
Location: Barcelona
Country: Spain
Start Date: July 11, 2010
End Date: July 15, 2010
Sponsors: American Inst. of Aeronautics and Astronautics