Abstract
Equivalent System Mass (ESM) is a metric used in Advanced Life Support (ALS) studies to evaluate and compare life support system technologies. Previous crew time ESM calculations considered only the amount of crew time required to perform a particular task without any interventions (stress events), i.e., they calculated static crew time. However, variations in time spent on operating and maintaining a life support system may occur due to performance fluctuations of the crew caused by a range of stress events experienced. Simulated crew performance calculations appear to suggest that crew time varies based on how each crewmember deals with stress events. Assigning a variable that accounts for such variation in crew time can be used in the crew selection process and for crew management strategies to better deal with inevitable stress events.