Electrical Arc Ignition Testing of Spacesuit Materials

A frayed wire was found inside the extravehicular mobility unit (EMU) spacesuit, which led to concerns that it may be possible to ignite materials in the EMU by electrical arcing. As a result, the NASA Johnson Space Center (JSC) White Sands Test Facility was requested by JSC to conduct arc-ignition tests on multiple EMU materials placed in varying oxygen concentrations. Because understanding the ignitability of materials requires simulating the worst-case scenario, three test methods were developed to understand what conditions were the most severe. The most severe method was then used to characterize the materials presently used in the EMU by determining the minimum levels of current necessary to initiate combustion at a given voltage. These arc-ignition tests were performed in 100 % oxygen at 23.5 psia and in 50 % oxygen at 50 psia. The following materials were tested: cotton fabric; polyester fabric; polyurethane cable jacket; Gore-Tex® woven polytetrafluoroethylene (PTFE) fabric; nylon/Lycra® knit fabric; moleskin; nylon/spandex knit fabric; nylon tricot fabric; cotton-flocked Rucothane;® urethane-coated nylon; Kerlix® cotton dressing, Estane® polyurethane; and Capilene® hollow fiber polyester fabric.