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National Aeronautics and Space Administration

EVA23Water Intrusion

disregarded, despite the fact that this type of failure almost always occurred near the end of a long EVA. No one on the team recognized the relationship between the early failure of the CO2 sensor and an abnormally large amount of water in the vent loop until much later. See Appendix A.2.3 PC102 Channelized Attention for more detail. ECFT-3.1.1.1.1 – FCT/Crew incorrectly attributed water in helmet during EVA 22 to the drink bag. (Intermediate Cause 1) Supporting Evidence: The MIB learned from the EVA 22 Debrief and interviews that the crew and ground attributed the water in the EMU 3011 helmet at the end of EVA 22 to a leak in the crew member’s drink bag. EV2 had indicated that he saw some water escape past his bite valve during repress and that maybe this had happened because his chin was resting on the bite valve while he was in a tucked position. Audio logs and interview transcripts revealed that the ground team accepted the crew’s determination of cause for the EVA 22 water leak. After EVA 22, the team perceived that additional investigation of the water leak was not necessary, because the source had already been identified and agreed upon. They also considered that a lengthy investigation could impede preparations for EVA 23. Crew and ground team training did not prepare the team with an adequate understanding of how the EMU could fail with respect to water in the helmet. Had this been done, the crew and ground team may not have attributed water in the helmet to just the drink bag. The causes for this event were discussed previously in ECFT-1.1 branch: FCT/Crew attributed Water in the helmet during EVA 22 to the drink bag. The Human Factors Analysis (Appendix A) findings support the fact that the team was predisposed to determine the drink bag was the cause of the water. See Appendix A.1.1 PC 214 Response Set for more detail on ECFT-1.1. ECFT-3.1.1.2 – Team's set of responses led to a delay in identifying the vent loop as the source of the water leak. (Intermediate Cause 13) Supporting Evidence: After the conclusion of EVA 22, the team erroneously perceived that the water in EV2’s helmet came from EV2’s drink bag. Based on the audio logs and interview data, we find that early in the course of EVA 23 events, the team began to inquire about the source of the water and the one question that was repeated by multiple team members was: “is the water coming from his drink bag?” This line of questioning was reinforced by the framework of expectations that arose from EVA 22. The early failure of the CO2 sensor provided another opportunity to suspect something other than the drink bag as the source of the water. The CO2 sensor sometimes fails during EVA ops, a fact that is generally known (and attributed to sublimator carry-over) by all ground team personnel who monitor it. It failed earlier than usual during EVA 23, because of excessive water in the vent loop. This was an off nominal event, yet the team missed its significance because of “normalization of deviance.” See Appendix 0

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ISS EVA Suit Water Intrusion Mishap Investigation Report  

Report of the NASA Mishap Investigation Board examining the high visibility close call event of July 16, 2013 when ESA astronaut Luca Parmit...

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