Engineering Mechanical Counter Pressure Spacesuits and Compression Garments
Akshay Kothakonda, HSL graduate student
"Extravehicular activities (EVA’s) are an essential and integral part of human exploration of space, with their use ranging from performing scientific experiments on a planetary surface to assembling space stations. Spacesuits must provide an astronaut with the conditions necessary to survive an EVA for several hours and to enable them to carry out these complex tasks. One of the main factors impeding the effectiveness of EVA operations is the stiffness of the spacesuits, which is inherent in gas pressurized suits.
While there have been several engineering advances in improving the mobility of gas pressure suits, a mechanical counter pressure (MCP) suit seeks to significantly improve mobility and minimize metabolic workload by replacing gas pressure with contact pressure of a tensioned fabric against the body. Although a marked improvement in mobility of MCP suits over traditional gas pressurized was demonstrated in the 1970’s with the Space Activity Suit, engineering challenges remain before this such a suit can be used operationally. Applications of the MCP suit concept extends to compression garments for athletic and medical use, albeit at generally lower pressures.
The research presented aims to address some of the fundamental requirements of an MCP suit. These include providing uniform MCP of 29.6 kPa over the body, minimizing mechanical work during suited movements, and enabling easy don and doff. While the current research focuses on the single degree-of-freedom arm section of the suit, the work can be extrapolated to the entire body. The bidirectional actuation of two-way Shape Memory Polymers (2W-SMP) is leveraged to both provide MCP and allow for easy don/doff. Nonlinear finite element analysis (FEA) models to analyze the deformation of woven and knit fabrics under suited movements are being developed, which when combined with thermomechanical behavior of the SMP, would inform fabric patterning that imposes minimal mechanical work on the wearer, for given pressurization requirements. Finally, Mapping skin Lines of Non-Extension (LoNE’s) informs contours for inextensible cables that do not impede movements. These cables may form part of suit life support system."