STS-129: MEI issue may require additional instrumentation – NBL incident

by Chris Bergin

Engineers are closing in on a plan to install instrumentation on Atlantis – in time for her November 16 launch date – in order to understand a potential issue with a stinger structure on the aft of the vehicle, which may be susceptible to the stresses of Main Engine Ignition (MEI). Meanwhile, a crewmember avoided injury during an incident that has temporarily closed the Neutral Buoyancy Laboratory (NBL).

STS-129 Latest:

Closeouts are continuing on Atlantis, as engineers push forward at a steady pace for the November 16 launch attempt for STS-129. The crew have also completed the Terminal Countdown Demonstration Test (TCDT) and will soon fly back to Houston.

The next key event for processing relates to the installation of the Atlantis’ payload into her cargo bay, which is due to take place on Wednesday.

“OV-104 (STS-129): Got the EMU functional completed. The airlock has been closed out for flight. The payload was installed to the PCR (Payload Checkout Room) on Friday. The Payload Bay Doors (PLBDs) have been opened, and installation of the payload (is due) this Wednesday.”

Processing is working alongside two items of interest that were discussed at the Agency level Flight Readiness Review (FRR) last week at the Kennedy Space Center, one of which – the replaced Waste Collection System (WCS) hardware – requires a one flight waiver to be issued.

“Mentioned at FRR that they would take a Level 3 waiver to the 20G crash requirement for the WCS bracket because they could not show it good by analysis,” noted the Orbiter Project on the latest Shuttle Standup/Integration report (L2). “Late last week, they conducted a test with a similar bracket, and showed that the bracket has greater than 20G capability, which will support the waiver.”

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Described as a “great test to pull that 20G crash load,” by NASA’s Chief Engineer on the report, the bracket on the system – which is at the center of the issue with the WCS – will be replaced by a titanium substitute after STS-129.

“The work on the WCS and all that was outstanding, and it was good to hear this weekend that the testing went well, so that we have the one flight waiver before we get our titanium bracket,” added Space Shuttle Program (SSP) manager John Shannon on the standup.

A2The bulk of SSP interest remains with the evaluations into a potential issue with a very small area of the orbiter. This area – known as a stinger – failed to be cleared by recent analysis into the concerns that recent acoustic environment analysis of the Space Shuttle Main Engines during ignition could cause stressing – and potentially cracking – in the attach pins/stinger.

The stinger is likely to be fine for the life of the program, but the SSP are using due diligence both physically – via borescope inspections which have begun – and via test articles.

“There was a suggestion last Friday that there was a discrepancy in the stinger loads analysis that did not pan out. Structures has the analysis down pretty well and is working on a new (computational) model,” added the Orbiter Project at the Johnson Space Center.

“Finished the machining of a new attach point. That is complete less match drilling, dry film lube, and coupon testing. Will try to have a few of those available for folks to pull and bend. KSC has requested one to try some NDE (Non Destructive Evaluation) techniques. Disassembly of the qualification article was ongoing over the weekend.”

“Regarding MEI activities, there will be a meeting to bring some of the broader community in regarding some of the stress and fracture work that is ongoing, and some of the ideas that have come out of the other Centers,” NASA’s Chief Engineer added.

A3Described as a “team challenge” by Mr Shannon, the forward plan still involves the possibility of installing additional instrumentation, specifically into the area in question, in order to measure the loads on the stinger during Atlantis’ launch – even though only two weeks remain in the pad flow.

“It was a very good FRR on Thursday. The team extremely well. We are the beneficiaries of a very good series of flights and not many issues in work,” noted Mr Shannon in conclusion to the Standup meeting this week.

“We have a challenge as a team. Everybody is doing extremely well on understanding the main engine ignition overpressure. Getting instrumentation on is a doable thing. It is going to challenge us, but it is the kind of thing that our team really likes to do, and excels at.

“We are hitting it from both the pad side and the vehicle side. Gathering more data is important, and it sounds like the team is doing well. Whether or not we agree there is a problem, we should go ahead and get the instrumentation on. We will not really know until we collect more data.”

A full outline – based on a large FRR presentation – will be published later this week.

NBL Incident:

Meanwhile, an incident at the NBL has closed the pool until Wednesday, following a pressure supply system issue during one of the training runs last week.

A4The giant pool is used to train spacewalkers, with mock ups of the International Space Station structures and orbiter payload bay at the bottom of the pool, allowing for training to take place in a similar micro-G environment to that on orbit. It was not mentioned which crewmember was involved in the incident, although he/she did not suffer any injuries.

“Had a NBL Facility issue last week. The pressure supply system failed to overpress a suit. They expect the NBL to be back up on Wednesday. The integrated team is working the issue,” noted JSC’s MOD on the Standup.

No major interruptions to crew training are expected, although two training runs – for STS-132 and STS-130 respectively – have been cancelled during the NBL’s shutdown.

“Did have an NBL Facilities event on October 28. The control valve failed open on a suited event, which put 7.84 psid into the suit. The crewmember was not injured,” added the EVA department on the Standup. “They did find a bad connect on the ECS (Environmental Control System).

“On Friday, they did some testing with the relief valve in the suit, and it did pass its crack and reseat. They took one off the shelf, and it also passed its crack and reseat. There will be a quarter manned test; they will take the suit 40′ down to the bottom of the pool, limit the flow into the suit at 15 SCFM to make sure the suit can stay below 8 psi, which is where the suit can get some structural failure and leakage.

“Hope to open the pool again on Wednesday. They cancelled two runs for crews STS-132 and STS-130.”

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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