Influence of a Pitch Adjustable Foot Restraint on Operator Induced Loads in Zero-Gravity

The zero-gravity environment creates a need for a proper human body restraint system to maintain a comfortable posture which lessens fatigue and maximizes productivity. In addition, restraint systems must be able to meet the loading demands of maintenance and assembly tasks performed on-orbit. The Shuttle's primary intravehicular astronaut restraint system is currently a foot loop design that attaches to flat surfaces. This restraint system allows for variation in mounting locations and ease of ingress and egress. However, this design limits performance because it does not allow for elevation, pitch, or foot loop length adjustment. Several prototype foot restraint systems are being evaluated for use aboard Space Station and the Space Shuttle. A study was initiated using NASA's reduced gravity aircraft quantifying differences observed in operator performance while adjusting the pitch angle of a prototype foot restraint. Pitch angle adjustments were made from 5° to 35°. While operators performed a torque wrench task using a hand hold and foot restraint, the maximum axial forces and moments induced on the restraint systems and torque wrench were recorded. Overall this study did not see any significant difference in the force operators could place on the torque wrench or forces imparted to the foot restraint system due to the pitch orientation of the foot restraint. Thus in a work environment in which hand holds are available, no significant influence of the pitch angle existed for operator performance or forces imparted to the restraint system.