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National Aeronautics and Space Administration

EVA23Water Intrusion

for risk acceptance, the retention rationale justifies use of the critical item in the system. The retention rationale drives the inspection, process control, and test/verification requirements for the critical items; influences operations planning (including mission planning, procedure development, and logistical and maintenance support requirements); and reports failure history. Logistical and maintenance support requirements could be impacted by acceptance of a critical item; therefore, consideration of the following should precede formal acceptance of each critical item: total crew maintenance time allocations, logistical capabilities of the system, and microgravity (probability of success) requirements. In order to be effective in fulfilling its purpose, it is essential that the FMEA be kept current with the ISS design and operational use.” From interviews and discussions with personnel, it was determined that updating the FMEA is primarily viewed by many as a paperwork exercise and a tool to be mainly used by the S&MA community. This is further evidenced in practice by the lack of time and effort taken to update and review the information when it is deemed necessary to update as well as its lack of involvement in engineering risk discussions or training. See Recommendation R-5 above. ECFT-3.1.2.1.1.2 – FMEA/CIL did not effectively quantify the amounts of water entering the vent loop from the PLSS. (Contributing Factor 7) Supporting Evidence: As discussed in ECFT 3.1.2.1.1.1, PLSS water in the vent loop is discussed in the FMEA but does not directly address the quantity of water reaching the helmet. MOD did not understand the failure mode. ECFT-3.1.2.1

EMU Hazard Report did not identify the hazard.

Minor amounts of w ater in the helmet w as normalized.

Engineering Team did not understand the failure mode.

Safety Team did not understand the failure mode.

ECFT-3.1.2.1.1

ECFT-3.1.2.1.2

ECFT-3.1.2.1.3

ECFT-3.1.2.1.4

Figure 3-51. Causes and Contributing Factors under ECFT 3.1.2.1 for reference ECFT-3.1.2.1.2 – Minor amounts of water in the helmet was normalized. (Root Cause 5) Supporting Evidence: Through interviews with ground personnel and review of data from previous EMU performance, it was clear that some water entering the helmet was considered normal by the ground teams. EMU 3005 was even referred to as the “wet” EMU since its acceptance test data indicated that its sublimator slurper was less efficient and led to a larger amount of water carryover into the vent loop. Despite the fact that water carryover into the helmet presented a known hazard of creating eye irritation due to its interaction with anti-fog agents, and also presented a potential fogging hazard, the ground teams grew to accept this as normal EMU behavior. Since these smaller amounts of water carryover had never caused a significant close call, it was perceived to not be a hazardous condition. When water began entering EV2’s helmet, the ground team discussed anti-fog/eye irritation concerns, and visibility

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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...