STS-127: Don’t worry about the schedule, let’s fix the problem – Cain

by Chris Bergin

Endeavour will launch only when engineers are happy they have a full understanding of the Ground Umbilical Carrier Plate (GUCP) leak, even if that means slipping STS-127 past the current July 11 NET (No Earlier Than) launch target. A troubleshooting plan is currently being drawn up – which is understood to include a tanking test – with the aim of finding a root cause of the leaks.

STS-127 Current Status:

Endeavour’s second launch attempt was scrubbed due to similar leak from the gaseous hydrogen system to that which was observed during the first tanking of External Tank ET-131, just a few days previous.

On both occasions, a scrub was called due to the breach of the pre-defined LCC (Launch Commit Criteria) limits, which protect against leak readings greater than 40,000 PPM – or 4 percent.

“This time the leak started during fastfill which is a signature we’ve never seen before (relating to the difference between the previous leaks, observed as the tank loading process moved from fastfill to topping/stable replenish of the LH2). During fast fill we leaked to approx. 15,000 ppm, we are allowed to get to 40,000 ppm before a violation causes safing,” noted a scrub outline on L2.

“Once we reached replenish, we violated the 40.000ppm like we’ve typically seen in the past. Leak eventually trended upward to 60,000 ppm. Subsequent vent valve cycling saw somewhat of a decrease. Test team analysis indicated that the increase is about half of that seen (on the first launch attempt).

“A troubleshooting plan will have to be formulated as this is a leak signature that has never been observed before.”

“Vehicle was powered down at 03:15L (Friday). Hooked up the OBMUU and have started the PRSD (Power Reactant Storage and Distributation) offload. Will vent the COPVs (Composite Overwrap Pressure Vessels) late on Friday,” added Friday processing information on L2. “The teams are picking up with meetings on the GUCP problem.”

Detanking of ET-131, along with the requirement for the tank to “boil off” its residual propellants, has been completed. However, engineers are not due to return to the tank until next week – pending the completion of the troubleshooting plan that is likely to open with the recording of measurements prior to any demating of the Quick Disconnect and/or replacement of the GUCP seal.

“Continuing to support the GUCP investigation, both at MSFC (Marshall Space Flight Center) and MAF (Michoud Assembly Facility),” added the Lockheed Martin/ET on the latest Shuttle Standup/Integration report (L2).

“The STS-127 flight seal that was removed at the first leak is at MAF. Working with the folks on inspection and dimensional analysis.”

a27There are several candidates for root cause, such as unique thermal conditions associated with the hardware, notably the dynamics of the cryo temperatures that may be interacting with the hardware’s hinge brackets, resulting in a misalignment during tanking.

Also under evaluation are potential software issues, and even possible issues with the leak detectors that registered the leak during tanking – as much as the latter has been ruled out as a specific reason for the scrub due to the visible observation of venting from the tank.

Another investigation path will be the evaluation of the External Tank hardware itself, as opposed to the Ground Support Equipment (GSE) of the GUCP QD, which may be the reason for the specific leak issues observed with STS-119 and STS-127’s tanks.

Such theories will be investigated as part of the root cause evaluations – which will result in a get-well plan ahead of the next launch attempt. Notably, it is understood that the resulting resolution will be tested via a tanking test, not unlike the path taken with the ECO (Engine Cut Off) sensor/LH2 Feedthrough solution ahead of STS-122’s launch.

STS-122 ECO related news content (all exclusives): *Scrub 1* – *MMT Debate* – *Scrub 2* – *Hale Memo* – *Forward Plan* – *Culprit Found* – *Tanking Test* – *Repair Options* – *MAF Plan**PRCB Debate* – *Plan Approved* – *Repair Schedule* – *Launch Date* – *New Issue* – *Hale Rallying Call* – *PRCB Launch Dates* – *New Connector Installed* – *Positive Test Results* – *Manifest Impacts* – *Optimism with forward plan* – *Flight Rationale* – *Repairs Finalizing* – *Root Cause Confirmed*

As to how long the investigation and resulting troubleshooting plan will take, managers are currently aiming to be ready to launch Endeavour once the Beta Angle Cutoff has ended – which is due around July 11.

t41“Asked to assess the July 11 beta cut-out, and if there is any flexibility in moving that back at day or two, and what the long poles are in doing that,” added JSC’s Mission Operations (L2).

However, Mission Management Team (MMT) chair and deputy shuttle manager LeRoy Cain emphasized the need to work the problem and find the solution before they can even consider setting a new launch date.

First he praised the superb efforts by engineering teams – which worked through all three shifts to replace the GUCP QD and Seal after the first scrub – to allow the team to be in a posture for the second launch attempt.

Ironically, STS-127 would not have launched even without the leak issue, due to a breach in weather conditions at T-0.

“After the scrub attempt on Friday, the teams worked really hard to get us in a posture to try to go launch again,” noted Mr Cain via the Standup report. “Even when we got there it was a challenge to be able to get to a tanking scenario, but again the teams worked really hard to be able to go do that.

“It was a go thing that we were able to tank. We’ve got a good test of our system, and we obviously have a significant issue to work that we don’t understand. So, we are assembling a team to go off and work the problem and we will figure it out. It will take us a little time to figure it out, probably. But we will figure it out, we will get it rectified, we will move on, and we’ll fly sometime in July.”

Despite some ridiculous claims made by one media outlet of late, the true nature of the shuttle program’s leadership and engineering teams was again in evidence when Mr. Cain continued by pressing home the point that there will be no pressure to launch until the engineering teams have full confidence in the resolution of the tank’s leak issues.

“Mr. Cain wants to make sure folks in the technical teams are more worried about working the problem and coming to resolution than they are worried about the schedule,” added minutes from the Standup meeting.

“We will fly when we are ready to go fly. It may or may not be July 11. July 11 is only a few weeks around the corner here. We are not going to pick a date like July 11th and work backwards from it, and try to cram all the work into that.

“We are going to put together the best plan we can to understand the problem and resolve it, and then we will go figure out the schedule, and then figure out when that means we go can fly. So that’s the approach that I’d like the team to be thinking about, and don’t worry about the schedule. We’ll fly when we are ready.

“So with that, again, really appreciate the effort by the team. And, keep your head up. This team is extremely blessed to have a lot of capability and a lot of talent. And, I think we are steeped in aptitude for solving these kinds of problems. I have a lot of confidence that we’ll be able to get there and go fly.”

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.

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