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Constellation Program (CxP) EVA Systems Test 3 - Effect of Center of Gravity on Metabolic Costs and Biomechanics of Ambulation in a Planetary Suit (IST_3)
Principal Investigator
Research Area:
Biomedical countermeasures
Extravehicular Activity (EVA)
Species Studied
Scientific Name: Homo sapiens Species: Human

Analysis of video from Apollo lunar surface extravehicular activities (EVAs) has demonstrated that astronauts experienced difficulty maintaining stability. This led to the hypothesis that spacesuit center-of-gravity (CG) is an important parameter affecting human performance. To specifically evaluate the role of CG, tests have been performed at the Neutral Buoyancy Laboratory (NBL) and during NASA Extreme Environment Mission Operations (NEEMO). Initially, six configurations framed the boundaries of potential CG locations (high, low, aft, forward, ideal, and the Crew and Thermal Systems Division [CTSD]). These configurations were evaluated for their effect on ambulation and performance of exploration tasks. Based on crewmember gravity compensation and performance scale (GCPS) ratings, these studies demonstrated that ideal and forward CGs were acceptable. The other CGs required moderate to considerable operator compensation, with the high and aft CGs being the least favorable. Subsequent NEEMO tests evaluated four additional CG configurations located within the region expected to contain the lunar spacesuit system CG. Preliminary unpublished results indicated that these CG locations were acceptable based on crew GCPS ratings.

Although it provides an insightful first look at the effect of CG on human performance in lunar gravity, the underwater environment does not permit several critical data parameters such as metabolic rate and biomechanics to be collected. The purpose of this study was to expand on the preliminary CG research from the underwater environments and evaluate the effects of varying CG on human performance in lunar gravity using the Johnson Space Center (JSC) SVMF partial-gravity offload system (POGO) with unsuited subjects.

The primary objective of this study was to evaluate whether and how a change in a system's CG affects human performance metrics (eg, metabolic rate, biomechanics, subjective ratings, stability) in simulated lunar gravity during level-ground ambulation, inclined ambulation, exploration tasks, and postural testing. It should be noted that this objective was to be tested in both the unsuited and the suited condition, but was only tested in the unsuited condition. The POGO, in its current configuration, could not offload the additional weight required to complete the test in the suited condition.

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Norcross JR, Clowers KG, Clark T, Cowley MS, Harvill L, Chappell SP, Stroud LC, Desantis L, Paloski WH, Morency RM, Vos JR, and Gernhardt ML. Effects of changing center of gravity on shirtsleeve human performance in reduced gravity. Houston TX: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center; 2010. NASA Technical Memorandum NASA/TM-2010-216127.

Norcross JR. Using analogs for performance testing of humans in spacesuits in simulated reduced gravity. Houston TX: National Aeronautics and Space Administration, Johnson Space Center. September 24, 2013. NASA Technical Publication NASA/TP-2013-20140002724. [NTRS]

Chappell SP and Gernhardt ML. Extravehicular activity testing in analog environments: evaluating the effects of center of gravity and environment on human performance. National Aeronautics and Space Administration, Lyndon B. Johnson Space Center; 2009. [NTRS]

Oxygen consumption
Gravity, altered
Extravehicular activity
Task performance and analysis

Photo Gallery
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Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

Center of pressure
Change from 1-g, percent
Completed rock pick ups
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
EPSP 01/01/2006 09/30/2010 4 years, 9 months

Human Research Program (HRP) Human Research Roadmap (HRR) Information
Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at:

+ Click here for information of how this experiment is contributing to the HRP's path for risk reduction.

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
National Aeronautics and Space Administration (NASA)