STS-127’s External Tank (ET-131) has completed a tanking test on the realigned Ground Umbilical Carrier Plate (GUCP) and a two-part seal, with no leaks detected. As a result, NASA is officially a go for a launch attempt of Endeavour on July 11.
Engineers were ready for the tanking test, despite the late retraction of the Rotating Service Structure (RSS), impacted by poor weather in the local area earlier in the flow.
“GUCP Troubleshooting: Ambient leak check of the vent line, shroud closeouts final purge were completed. Vent line flange bolt retorque was successfully performed, ” outlined processing information on L2.
“LOX and LH2 preps and checkout of the GUCP were completed on Monday. GUCP interface electrical retests were completed with nominal results.
“Final measurements and data collection of the plate position in flight configuration was completed. ET/IT GSE (Ground Support Equipment) door removal, closeout inspections and flight door installation complete. Strain gauge removal has been performed.”
For all 18 NASASpaceflight.com articles on the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/
The bad weather over the Kennedy Space Center (KSC) also produced two lightning strikes to Pad 39A, which resulted in an Engineering Review Board (ERB) evaluation of Endeavour’s electrical systems – which were found to be unaffected.
“S0018 Adverse Weather Update: Just prior to S0037 CTS (Call To Stations) a very active weather system rolled through the LC39 area,” added processing information.
“Pad-A experienced a lightning strike to the Catenary Wire system just under 0.1 nautical miles from Pad Center and another at 0.37 nautical miles from Pad Center.
“Appropriate operations in S0018 (were) kicked off to begin investigation and data gathering.
“Walk-downs needed to be competed ASAP due to pad clears for PRSD (Power Reactant Storage and Distributation) Load. An ERB for data review has (been conducted).
At one point earlier this week it was deemed likely the tanking test would be moved to Thursday. However, engineers managed to complete all the required tasks on time.
Following no leaks during the tanking test, confidence has been restored for ET-131, with the processing flow now moving towards a launch attempt of STS-127 on July 11.
“At Pad A, over the weekend continued with work on the ET GUCP. On Friday, the redesign of the fitted feet was worked. Over the weekend, got them fabricated and installed early Monday morning,” added KSC Integration and Engineering notes on the latest Shuttle Standup/Integration report (L2). “That took a little longer than the original plan.
“Once completed, got the vent line reconnected and got the 3/8” QDs installed. Running down to the plan that they went into the weekend with. Will press on with that plan and the tanking test Wednesday at 07:00. It is running a little tight but think have some room to get there.
“Really pleased to see everything come together with feet alignment. The team has been working really hard over the weekend. Looks like we will be ready for Wednesday.
“In support of the tanking test, if we are on for Wednesday, will have a tanking weather telecon at 06:30 before the tanking at 07:00. That will be a quick meeting, with no donuts or coffee. L-1 is planned at 09:00 a.m. on July 10.”
Making Wednesday for the tanking test wasn’t critical to the target of a July 11 NET (No Earlier Than) launch date for STS-127, with Mr Shannon noting some margin exists in the flow between the two dates – although engineers will be required to work through the upcoming holiday period.
“John Shannon confirmed there is some margin between Wednesday and making the July 11 attempt. They would just have to work over the holidays,” added the Standup report.
“Mr. Shannon added there was nothing magical about Wednesday. If the weather doesn’t work out, or if we run into any problems, we are not going to push it, we will just do it at the right time.”
Should all proceed to plan with the tanking test, the results are likely to be discussed at Thursday’s Program Requirements Control Board (PRCB) meeting, which is usual for major troubleshooting efforts – previously seen with the Flow Control Valves (FCVs) which called for a “Special” PRCB review.
“The GUCP Steering Committee will meet and nail down all the forward actions they have,” added the forward plan. “If they do go to a tanking test on Wednesday, will probably try to report out at PRCB on Thursday.”
Interestingly, the tank may still leak. That in itself would not be a major setback, given the two-seal design that is now installed on ET-131 has leaked previously. The difference being such a leak is characterized as a “burp” and can be controlled even without cycling the valves.
“Mr. Shannon clarified that we have loaded tanks with this two-part seal twice before, and one time we had a leak but we could cycle the vent valve and control it, and the other time it didn’t leak,” added the Standup. So, if it leaks it won’t be a big surprise.
“It was clarified that the tank “burped”, which was within requirements, and the vent valve did not need to be cycled.”
However, should the tank leak in the same manner as seen twice with ET-131, and once on ET-127 (STS-119’s first launch attempt), it may result in the STS-127 stack being rolled back to the Vehicle Assembly Building (VAB) for a tank swap.
This article will be updated during the tanking test – see live update pages for up-to-the-second live coverage.
L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.