Engineering Polymers as Structural Materials in Spacecraft Water Systems
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High-performance engineering polymers, such as PEEK, PEI, and PVDF, have found increasing use as structural materials in a broad array of demanding applications, including in the aerospace, medical implant, and chemical processing fields. In many cases, they have replaced passive metals, due to cost or mass savings, improved chemical resistance and inertness, and/or ease of fabrication. As of yet, there has been little concerted investigation considering the replacement of metals in spacecraft water systems to take advantage of these developments. The decision to baseline ionic silver as the biocide of choice for future exploration-class systems motivates considering this change, as rapid Ag+ depletion to metal surfaces can result in loss of microbial control. The development of inert barrier coatings may enable the continued use of metal alloys in many applications, but introduces additional failure modes and suitable robustness has yet to be adequately demonstrated. In this early work, we began to address the myriad issues of concern associated with materials selection for performance-critical life support hardware. These include mechanical properties, failure mechanisms, design requirements, leaching into potable water, chemical resistance, radiation tolerance, outgassing, flammability, and others. We selected several engineering polymers for initial consideration and conducted Ag+ compatibility tests on a limited selection of these, including materials with reinforcing fibers or lubricant fillers. We identified useful literature regarding rational materials selection, design, and mechanical behavior of engineering polymers. We found that there is significant potential for use of engineering polymers in spacecraft water systems but note that much work remains to assemble a knowledge and experience base regarding long-term mechanical reliability of pressurized thermoplastic components and to develop relevant design/test qualification practices and standards. Finally, we suggest some directions for future research.
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Alexander Shaw, NASA AMES RESEARCH CENTER / UNIVERSITIES SPACE RESEARCH ASSOCIATION, US
Lance Delzeit, NASA, US
ICES303: Physio-Chemical Life Support- Water Recovery & Management Systems- Technology and Process Development
The 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.