Last Published:  03/26/21 03:33:57 PM (Central)
Responsible Element: Human Health Countermeasures (HHC)
Status: Open
Present state of knowledge: The suits being designed for future missions will have the capability to operate at a variety of pressures, from a low pressure of 3.8 psi up to the 8.2 psi planned for use in the planetary vehicles/habitats. The higher pressure ranges will enable shorter pre-breathe times and decrease the amount of time required for preparations prior to each EVA. However, the pressure at which EVA suits operate affects the resistance experienced by crewmembers at individual joints, and can increase work load, with quicker onset of fatigue and possibly overuse as well as acute injuries, which can ultimately affect health and performance outcomes. Lower suit pressures are easier to operate in, but increase the risk of decompression sickness (DCS). Understanding the trade-offs between suit pressure, work-loads, and health and human performance outcomes such as fatigue and injuries will inform the selection of optimal suit operating pressures to be used during EVAs, as well as the design of EVA concepts of operation, and the development of countermeasures as needed.

Research approach: Most of the work under this gap is being funded by non-HRP sources within NASA, including the EVA Office, the Crew and Thermal Systems Division (CTSD), and the Human Health and Performance Directorate (HHPD). NASA’s HRP has interest in the results of these studies, in particular 1) A study that will characterize performance of isolated EVA tasks at different suit pressures to create a database of performance vs. pressure level, using the planetary EVA standard measures that are being defined in a current study. This study will quantify and compare health and human performance outcomes for human subjects operating in the space suit at a range of pressures. 2) A study that will characterize suited health and performance outcomes, as a function of EVA duration and frequency, evaluate EVA workload, and performance/physiological metrics (such as fatigue, metabolic rates, ability to perform exploration-relevant tasks, neurocognitive fatigue). The study will involve realistic full EVA simulations, comparing different pressure profile/duration/frequency scenarios (i.e. 3 x 8-hour or 4 x 6-hour simulated planetary EVAs on ARGOS or NBL within a week).

HRP will contribute funding to some of the tasks, and will fully fund a task related to understanding and modeling injury risk.
While anthropometry and suit fit are aspects of importance to injury risk, HHC does not plan to directly fund studies in the areas of anthropometry and suit fit.
Target for Closure
Results will inform the selection of suit operating pressure(s) used during EVAs (a trade between decompression stress at lower suit pressures and increased joint resistance and fatigue at higher pressures), inform surface operations ConOps development, and feed into EVA fitness-for-duty and performance standards.
Risk Risk of Injury and Compromised Performance Due to EVA Operations
You are here! Gap EVA-201: Evaluate EVA performance, physiological/cognitive metrics, and injury risk when EVAs are conducted in a variable pressure suit.

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