Assessment and preliminary model development of shape memory polymers mechanical counter pressure space suits

Abstract

This thesis seeks to assess the viability of a space qualified shape memory polymer (SMP) mechanical counter pressure (MCP) suit. A key development objective identified by the International Space Exploration Coordination Group, the development of a superior space suit with greater mobility and environmental robustness is necessary to support long-range human space exploration, specifically a mission to Mars. Conceptualized in 1971, a spacesuit utilizing MCP would fulfill these goals but its development was halted due to inadequate mechanical analysis and material limitations at the time. Since then, new active materials have been assessed to potentially further the development of a space qualified MCP space suit, which include quantitative thresholds for minimum pressure production, durability, pressure distribution, mobility range, and ease of garment donning and doffing. Guided by these criteria, a SMP biaxial tubular braid applying MCP through active compression was designed and the prototype manufacturing processes were outlined. To predict the pressure production of this garment, the thermo-mechanics of a SMP was combined with the textile mechanics of a biaxial tubular braid and simulated within design parameter ranges consistent with the design criteria and practical considerations. The pressure production was controllable with the design parameters SMP elastic modulus, garment radial deformation, textile fiber spacing, and operational temperature. Assuming reasonable model accuracy, a SMP garment could achieve the necessary pressure production for a space qualified MCP suit, however, the durability of such a garment would be questionable considering the creep sustained from consecutive spacewalks of four to eight hours. Recommendations are made for methods to increase model accuracy, suggested SMP actuation mechanisms, and alternative textile architectures.