Development and Testing of a 3D-Printed Spacesuit Elbow Assembly
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Over the past several years, the University of Maryland has been developing technologies for in-situ additive manufacturing of spacesuits based on AX-5-type hard suits. Past work covered technologies tested for fabrication of pressure-tight structures, and focused heavily on 3D-printed bearings and seals. This paper summarizes the culmination of this first phase of the program, leading to the mechanical and human operations testing of a spacesuit elbow assembly made almost entirely using additive manufacturing. The final module is fabricated using selective laser sintering, except for the spherical balls in the bearings and metal rings to provide low-friction rotary sealing surfaces. Seals tested include both commercial off-the-shelf rotary seals and 3D-printed seals using a Polyjet process with variable material properties to optimize seal functionality. The elbow module is a four-bearing, three-wedge assembly attached to a sealing ring at the proximal end for installation in the UMd partial pressure glove box, and to a sizing insert and standard EMU wrist disconnect to attach to a spacesuit glove. Tests performed include external actuation of the elbow joint with and without pressure to measure bending loads and hysteresis, and use by human test subjects inside a glove box depressurized to 4.3 psid. A Fitts’ Tapping test board was developed and integrated into the glove box to provide a quantitative measure of arm mobility, in conjunction with NASA Task Load Index (TLX) assessments from the test subjects. All tests were also performed with a standard EMU arm as a control. Results of the testing are presented and analyzed; the paper concludes with an assessment of the potential of this technology to scale up to a full pressure suit, and design concepts for future testing and eventual operational applications.