{"id":39855,"date":"2013-05-11T17:23:50","date_gmt":"2013-05-11T09:23:50","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/successful-eva-likely-to-have-resolved-ammonia-leak\/"},"modified":"2013-05-11T17:23:50","modified_gmt":"2013-05-11T09:23:50","slug":"successful-eva-likely-to-have-resolved-ammonia-leak","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/successful-eva-likely-to-have-resolved-ammonia-leak\/","title":{"rendered":"Successful EVA likely to have resolved ammonia leak"},"content":{"rendered":"

Spacewalkers Chris Cassidy (EV-1) and Tom Marshburn (EV-2) ventured outside of the Quest Airlock on Saturday, in search of the source of an ammonia leak. The duo investigated the cooling loop of power channel 2B on the P6 Truss of the Station, and while the system appeared to be clean, the installation of a new PFCS appears to have resolved the issue.<\/p>\n

\nEVA-21 (This article was updated throughout the EVA):<\/p>\n

*Click here for the LIVE, INTERACTIVE ROLLING UPDATES*
\n*Click here for the main baseline EVA-21 article*<\/p>\n

A huge effort has been undertaken to plan Saturday\u2019s EVA, resulting in the crew being in a stance to conduct the EVA less than two days after the leak was first observed.<\/p>\n

Following pre-sleep tasks, the Expedition 35 crew helped the spacewalking duo through one of the more recent additions to life on the ISS, one that allows for spacewalkers to avoid the overnight campout in the Quest Airlock.<\/p>\n

\"ISLEKnown as the In-Suit Light Exercise (ISLE) EVA Pre-Breathe Protocol, the procedure allows for pre-EVA conditioning of the spacewalkers set to head outside of the orbital outpost.<\/p>\n

Debuted during STS-134, the procedure does not require overnight campout in Quest or CEVIS exercise, which helps conserve oxygen usage aboard the ISS.<\/p>\n

For the actual procedure, the two spacewalkers performed a 60-minute mask pre-breathe with the airlock depressed to 10.2 psi. They then donned their spacesuits (EMUs) and performed standard EMU purge before the airlock was repressurized to ISS ambient levels.<\/p>\n

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Following this, the EVA crew spent 100 minutes performing in-suit pre-breathe, 50 minutes of which will consist of light in-suit exercise with 50 minutes of resting (nominal) in-suit pre-breathe.<\/p>\n

\"EVA-21The first order of business for Cassidy and Marshburn upon egressing the A\/L was to translate out to the P6 Truss worksite.<\/p>\n

Upon arriving at the worksite, the spacewalkers told controllers on the ground they saw no obvious signs of ammonia flakes in the region.<\/p>\n

However, they did observe a \u201ccoffee stain\u201d on one element of hardware, which they took photos of once they were in a daylight pass \u2013 due to a failure of the flash on their camera. The flash was later fixed.<\/p>\n

\"PGTAfter fully setting up the worksite, the duo proceeded to begin work to remove the 2B Pump Flow Control Subassembly (PFCS).<\/p>\n

The removal was completed via the use of the Pistol Grip Tools (PGTs), driving the H1 & H2 bolts on the PFCS to close the Fluid Quick Disconnect Coupling (FQDC) ammonia valves between the PFCS and the P6 Truss.<\/p>\n

Again, the hardware was reported as looking \u201cclean\u201d \u2013 although a few specks of ammonia were observed as the H2 bolt was driven by the PGT.<\/p>\n

Next, they proceeded to drive the H3 and H4 structural bolts, allowing them to remove the PFCS from the P6 Truss Integrated Equipment Assembly (IEA). Photos were taken as the unit was removed, with no sign of ammonia in the area.<\/p>\n

\"SearchingThe PFCS was temporarily stowed on the Multi Use Tether (MUT) \u201cBallstack\u201d, following which a visual inspection was conducted of both the PFCS and the IEA to try and find a \u201csmoking gun\u201d for the source of the leak.<\/p>\n

However, once again, the report came down that the assembly looked \u201creally, really clean,\u201d according to Cassidy. \u201cI can\u2019t given you any data other than it looks nominal.\u201d<\/p>\n

With no source of the leak \u2013 or evidence of a leak \u2013 found, the spacewalkers could have re-installed the unit back into its original location, ahead of the spacewalkers heading back to the A\/L to end the EVA, while teams on the ground re-evaluate the situation.<\/p>\n

See Also<\/h4>\n