Failure Analysis Results and Corrective Actions Implemented for the Extravehicular Mobility Unit 3011 Water in the Helmet Mishap

摘要

Water entered the Extravehicular Mobility Unit (EMU) helmet during extravehicularactivity (EVA) #23 aboard the International Space Station on July 16, 2013, resulting in thetermination of the EVA approximately 1-hour after it began. It was estimated that 1.5 litersof water had migrated up the ventilation loop into the helmet, adversely impacting theastronaut’s hearing, vision, and verbal communication. Subsequent on-board testing andground-based test, tear-down, and evaluation of the affected EMU hardware componentsdetermined that the proximate cause of the mishap was blockage of all water separatordrum holes with a mixture of silica and silicates. The blockages caused a failure of the waterseparator degassing function, which resulted in EMU cooling water spilling into theventilation loop, migrating around the circulating fan, and ultimately pushing into thehelmet. The root cause of the failure was determined to be ground-processing shortcomingsof the Airlock Cooling Loop Recovery (ALCLR) Ion Filter Beds, which led to various levelsof contaminants being introduced into the filters before they left the ground. Thosecontaminants were thereafter introduced into the EMU hardware on-orbit during ALCLRscrubbing operations. This paper summarizes the failure analysis results along withidentified process, hardware, and operational corrective actions that were implemented as aresult of findings from this investigation.