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National Aeronautics and Space Administration

EVA23Water Intrusion

Figure 3-50 Causes and Contributing Factors under ECFT 3.1.2.1.1 ECFT-3.1.2.1.1 – EMU Hazard Report did not identify the hazard. (Intermediate Cause 16) Supporting Evidence: The MIB conducted a thorough review of EVA hazard reports. The EVA hazard report, EMU-13, that address water in the helmet is entitled “Contamination Control. Loss of Visibility.” Hazard Cause: Loss of visibility due to fogging of lenses (Helmet, DCM) Section E of EMU-13 hazard report applies to this failure: Water carryover into the re-circulating vent circuit and loss of SOP/Purge operation. The hazard report then goes on to list all of the relevant failure modes identified in the FMEA that can cause this hazard. The hazard level is listed as Critical. It then goes on to list all of the controls on the hazard. Nowhere in the hazard report does it mention the possibility of excessive water in the helmet resulting in a catastrophic event due to asphyxiation. Recommendation R-4: The ISS Program should ensure that updates are made to the EMU hazard reports to reflect the possibility of water in the helmet resulting in a catastrophic event due to asphyxiation. ECFT-3.1.2.1.1.1 – FMEA/CIL did not effectively describe the behavior of water entering the vent loop from the PLSS. (Intermediate Cause 19) Supporting Evidence: The EMU FMEA/CIL lists the following failure modes causing PLSS water in the vent loop that could potentially enter the helmet: •

102FM22 (LCVG Multiple Water Connector HUT half)

123FM04 (Fan/Pump/Water Separator)

123FM07 (Fan/Pump/Water Separator)

125FM02 (Pitot Actuated Valve or Pump Priming Valve)

134FM02 (Condensate Water Relief Valve)

140FM04 (Sublimator)

140FM05A (Sublimator)

141FM05 (Gas Trap)

All are considered 2/1R failures and thus are considered critical items. In each case the result of the failure mode is listed as water carryover in the vent loop and possible helmet fogging. Inconsistently, various FMEA/CILs mention the fact that there are 9 lbm of water in the PLSS and nearly all have the following or similar wording for the operational response (this particular quote is from 140FM04): “If helmet fogging occurs or significant amounts of water detected exiting helmet vent duct, terminate EVA per EVA Cuff Checklist. Open helmet purge valve to defog helmet and provide cooling to helmet area.”

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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...

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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