Body size and its implications upon resource utilization during human space exploration missions.

Area of Science:

• Space exploration
• Human physiology
• Life support systems

Background:

• Astronaut body size varies, impacting metabolic demands.
• Countermeasure (CM) exercise is used to mitigate spaceflight deconditioning.
• Accurate estimation of metabolic requirements is crucial for mission planning.

Purpose of the Study:

• To estimate the effects of body size and CM exercise on astronaut energy expenditure and metabolic byproducts.
• To determine hydration needs for space exploration missions.
• To inform life-support system design for diverse astronaut populations.

Main Methods:

• Theoretical modeling based on geometric similarity across a height range (1.50-1.90 m).
• Simulation of a four-person male crew with ISS-like CM exercise (2x30 min/day, 6 days/week).
• Utilized terrestrial data and equations where spaceflight-specific data were unavailable.

Main Results:

• Increased body size significantly elevated total energy expenditure (TEE), O2 consumption, CO2 production, and water requirements.
• CM exercise reduced the metabolic impact of larger body size.
• A 1.90-m crew exercising requires substantially more resources (energy, O2, water) and produces more waste (CO2, heat) than a 1.50-m crew without exercise.

Conclusions:

• Body size is a critical factor in life-support requirements for space missions.
• CM exercise can help manage metabolic demands but does not eliminate the need for increased resources.
• Strategies to meet elevated crew metabolic energy needs are essential for long-duration space exploration.