Space Systems Lab
University of Maryland
Metabolic Workload Measuring
Measurements of metabolic workload can provide useful insight to many aspects of EVA. These include quantitative assessment of suit improvements and robotic assistance, validation of neutral buoyancy simulation of EVA as a realistic training tool, sizing of next generation liquid cooling garments (LCGs) and expendables, and EVA task scheduling to maximize the productivity of an astronaut without overexertion. Real time monitoring of metabolic workload can also be utilized as part of health monitoring and can also be used to adjust task quantity and sequence during EVA as needed.
Historically, metabolic workload has been measured through LCG inlet and outlet temperatures, oxygen supply depletion rate, and heart rate measurements. All of these methods present some shortcomings and indirect calorimetry through a measurement of real time oxygen consumption (VO2) would be preferable. However, traditional VO2 techniques require the direct collection of expired air, which involves oronasal masks or mouthpieces with nose clips. The Space Systems Lab is developing a system for measuring oxygen consumption without this inconvenience. Oxygen and carbon dioxide sensors were mounted on the suit air outlet. This data, combined with the inlet flow rate, will be used to calculate VO2 and the metabolic workload.
A validation study for this system is underway. An enclosed plastic helmet is used to simulate the space suit breathing environment while allowing the subject free mobility below the neck. Test subjects perform a set of incremental treadmill exercises twice, once with the experimental helmet assembly and once with a standard VO2 measuring system as a control. Data from both sessions will be compared for system validation purposes.
The Metabolic Workload Measuring System for Space Suits is under development at the University of Maryland Space Systems Laboratory, part of the Aerospace Engineering Department and the A. James Clark School of Engineering. This research is supported through the Institute for Dexterous Space Robotics.