System Design for Tensioning Limb Sections in a Mechanical Counter Pressure Spacesuit

The MIT BioSuit™ is an advanced spacesuit concept under development that aims to impart pressure directly on the astronaut’s body through tensioned fabric, as opposed to gas pressurization used in all current spacesuits. Implementing this mechanical counter pressure (MCP) design eliminates the significant work required in compressing the gas volume during joint bending. In addition to reducing overall metabolic cost of suited operations, this suit design is expected to allow for near-natural body movements and to greatly enhance locomotion on reduced gravity planetary environments. The design challenge now entails minimizing the work required in deformation of the suit fabric during these movements. This paper investigates the overall BioSuit™ research goal to design a system that imparts the necessary 30 kPa of constant MCP to the entire surface of a limb by tensioning close fitting fabric. The system design consisting of a limb-longitudinal strip of Shape Memory Polymer and elastomer pair as the tensioning component and fabric as the passive tensioned component is described and results of mechanical testing of a partial fabric-elastomer system are presented. Plots of longitudinal force response under circumferential tension are obtained for various samples. The results obtained show that stiffness of the elastomer impacts resistance to joint bending, but up to a certain level of circumferential fabric tension. In essence, the results validate the design principle aimed at minimizing work required in joint bending by using low stiffness elastomers in conjunction with certain fabrics.