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EVA Walkback Test (EWT)
Principal Investigator
Research Area:
Biomedical countermeasures
Extravehicular Activity (EVA)
Species Studied
Scientific Name: Homo sapiens Species: Human

As lunar exploration vehicle and extravehicular activity (EVA) suit requirements mature it’s important to determine whether one or two surface rovers will be required to enable safe and efficient human exploration of the moon (1/6-g) and Mars (3/8-g). The increased mass, volume, and cost associated with the launch and transport of two rovers to the lunar surface could be considerable and might not be necessary if it is possible for the crewmembers to walk back to a habitat in response to a failed rover. As a starting point, it was assumed that 10 km would be the maximum EVA excursion distance from a habitat based on anticipated lunar surface operational concepts and results from the Apollo program. A multi-disciplinary team was assembled from the Constellation Program’s EVA Systems Project Office in collaboration with Johnson Space Center’s (JSC’s) Space Life Sciences Directorate Human Research Facility’s EVA Physiology, Systems and Performance (EPSP) Project to investigate the feasibility of performing a suited 10 km ambulation, (henceforth referred to as “walkback”) independent of whether the subject walked, jogged, loped, or ran.

This study was designed not only to determine the feasibility of a 10 km walkback, but also to collect human performance data relevant to optimizing space suit design for the targeted operational environment. The basic approach involved performing suited tests with unsuited controls with the goal that specific physiologic and biomechanical parameters of the suit could be understood across a range of gravity levels and ambulation speeds.

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De Witt JK, Edwards WB, Scott-Pandorf MM, Norcross JR, and Gernhardt ML. The preferred walk to run transition speed in actual lunar gravity. Journal of Experimental Biology. 2014. September 15; 217(Pt 18):3200-3. []

Norcross JR, Lee LR, Clowers KG, Morency RM, Desantis L, De Witt JK, Jones JA, Vos JR, and Gernhardt ML. Feasibility of performing a suited 10-km ambulation on the moon - final report of the EVA Walkback Test (EWT). Houston TX: National Aeronautics and Space Administration, Johnson Space Center; January 01, 2008. NASA Technical Publication NASA/TP–2009–214796. [NTRS]

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]

Oxygen consumption
Extravehicular activity

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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 gravity
Center of gravity
Ground reaction force (GRF), peak
Ground reaction force (GRF), peak
Maximal oxygen consumption (VO2 peak)
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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

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)
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