The Apollo program demonstrated that suit center of gravity (CG) is an important variable affecting human performance in Lunar Extravehicular Activities (EVAs). This study assessed crew performance of representative planetary exploration tasks with a single EVA suit weight with six different CG locations.
A reconfigurable back pack with repositionable weight modules was used to simulate Perfect, Low, Forward, High, Aft and NASA Baseline CG locations. All CG locations were based on the assumption of a 60 pound suit, a 135 pound Portable Life Support System (PLSS), and a standardized 6 foot 180 pound subject. These tests were conducted in NASA´s Neutral Buoyancy Laboratory and during underwater missions in the NOAA Aquarius Habitat. Subjects were weighed out for lunar gravity. Twenty-one subjects performed a task-battery that included ambulation, kneel and recovery, fall and recovery, rock pick-up, rock transfer, inclined ambulation from 10-30 degrees, shoveling, and ladder climb. Subject performance was assessed using a modified Cooper- Harper scale to assess operator compensation required to achieve desired performance.
Results suggest that CG location affects human performance. Subjects preferred Perfect, Low and Forward CG over High, Aft or Baseline (both High and Aft), which suggests that a conventional back pack PLSS may not be optimal and that alternative configurations should be considered.