STS-129: Atlantis receiving her ordnance – MEI evaluations continuing

by Chris Bergin

Atlantis is continuing to push towards her November 16 launch date, with the pad flow milestone of ordinance installation taking place this weekend. Meanwhile, the main focus of flight rationale clearance – the Main Engine Ignition (MEI) Acoustic and SSME (Space Shuttle Main Engine) Ignition Overpressure (IOP) Environments, relating to a stinger on the aft of the vehicle – continues to be evaluated.

STS-129 Processing Latest:

Atlantis is in the business end of her pad flow, as she continues to close in on S0007 (Launch Countdown) operations, which will begin next week. Although the 16th remains at the mercy of the Atlas V launch from Cape Canaveral, the flow is continuing to assume STS-129 will have an opening launch attempt a week from Monday.

“Orbiter OV-104 / ET-133 / SRB BI-140 / RSRM 108 (Pad A): Preps for S0007 Launch Countdown are in work. The team continues to work toward a November 16th launch date,” outlined the latest processing report from the NASA Test Director (L2). “Flight Controls final cycling and hydraulic system closeouts for flight were completed Thursday.

“The STS-129 Cryo simulation was successfully completed Thursday; the ET (External Tank) loading team is ready to support launch. Payload Bay Elbow and Wrist Camera installation and payload ROEU mates were completed Thursday. MMU (Mass Memory Unit) load, Friday.

“Preps for Final Ordnance Installation/Connection have been in work, with CTS (Call To Stations) resulting in Ordnance installation operations set to begin 1800 hrs Saturday. Orbiter aft closeouts continue; 50-1 and 2 door installation is scheduled for next Wednesday.”

STS-129 Specific Articles:

Only one issue – or Interim Problem Report (IPR) – has been listed by the NTD, relating to an issue with Atlantis’ General Purpose Computer (GPC) 1, which wouldn’t ‘boot up’ with the G9 software. G9 – often called OPS 9 – is the software used for ground processing, as opposed to OPS 1 (terminal count and powered flight), OPS 2 (on orbit operations), OPS 3 (de-orbit burn/entry) and so on. *

A4“IPR 46 (GPC 1 I Fail flag): With GPC 1 in G9 and GPC’s 2-5 in OPS 0, GPC 1 was taken to OPS 0 and an IPL (Initial Program Load) attempted. The IPL hung. It was suspected that the I Fail flag was on,” noted the processing report.

IPL – in overly simple terms – is when the GPC is booted up and loaded with system software, after which point it can be loaded with the desired OPS application software such as OPS 9, 1 etc.

“Troubleshooting power cycled GPC 1 and re-attempted the IPL. When GPC 1 was power cycled, the I Fail flag stayed on. DPS (Data Processing System) had no additional troubleshooting ready, so it was decided to get one GPC up in G9 Simplex to facilitate SRB, ET OI and Orbiter Power-down.”

Simplex mode – in this case – means the computer engineers ultimately loaded with G9 is not running as part of the redundant set (i.e. with some or all of the others running the same software) – but is running as a standalone.

“No hardware failure is suspected,” added the NTD. “This is probably a procedural/configuration issue but further engineering evaluation is in work.”

MEI/Stinger Latest:

Engineers are continuing to refine plans to gain further understanding into the stresses endured by a Reaction Control System (RCS) stinger attach point during MEI on several fronts, with a new dynamic model – required to convert acoustic environments into detailed internal loads – being worked by Boeing, evaluations into inspection footage via borescope, and plans to add sensors to the orbiter and pad ahead of Atlantis’ launch date.

See here for master baseline article on the MEI/Stinger evaluations:

A3With the previous dynamic model 25 years old, the concerns that acoustics stresses are over that of NASA’s 1.4 Factor of Safety (FS) margins are likely to be over-conservative – which would ultimately aid the path to flight rationale – as appears to be the case via early analysis.

“Main engine ignition (MEI) work: Modeling to recreate the original data is going well. Some unneeded conservatism was found, which makes the team optimistic that life predictions will improve,” noted the Orbiter Project Office (OPO) via the latest Shuttle Standup/Integration report (L2). “The first validation run with flight data was completed. Status regarding this issue will be provided to the OPO as information is developed.”

“MEI testing: Some of the fittings in the qualification units at WSTF (White Sands Test Facility) have been disassembled and removed,” added the update, referring to preliminary NDE (Non Destructive Evaluation) work that has been completed. “The equipment has been shipped to JSC (Johnson Space Center) for more in-depth NDE work.

“Have been manufacturing flight-like units for testing. These are being shipped to JSC. Test fixtures are being constructed, but represent the long-pole in completing the testing. This work is expected to be completed by next Tuesday, with results from the testing expected by next Thursday.”

A2With additional instrumentation on a very tight schedule for installation on to the orbiter and the Mobile Launch Platform (MLP) ahead of launch, continued discussions have been taking place on just how many additions can be achieved without causing a delay to STS-129’s opening launch attempt.

“Instrumentation work is proceeding well. This topic discussed at SSP (Space Shuttle Program) PRCB (Program Requirements Control Board) meeting. There are three different plans, but it is unlikely that two of the options would allow the November 16 launch date,” added the Standup.

This was elaborated on after the PRCB meeting, with the go-ahead to install instrumentation on the MLP’s Tail Service Masts (TSMs) and a WLEIDS (Wing Leading Edge Impact Detection System) related accelerometer on to the Left Hand stinger on Atlantis. However, the installation of a sensor on the Base Heat Shield (BHS) is unlikely to be within a viable timeframe to support the November 16 launch date.

A5“Main Engine Ignition Overpressure Issue Update: Several options were presented to the PRCB regarding attaching additional instrumentation to OV-104 (Atlantis) and/or the TSM’s to support the collection of Main Engine Ignition (MEI) acoustics loads data,” added an update from the NTD.

“The PRCB approved the options for Installing instrumentation in the LH2 TSM and installing a wing leading edge accelerometer inside the LH OMS/RCS stinger. Both these installations support the November 16th launch date. Additional loads analysis, due out on November 11, could indicate additional instrumentation is required.”

That November 11 meeting is the key decision date on pressing forward with the flight rationale required for the L-2 Day Mission Management Team (MMT) meeting – which is the key pre-launch managerial meeting from a paperwork standpoint.

At present, this potential issue is highly unlikely to cause a delay to STS-129, with managers simply carrying out due diligence to ensure they have a full understanding of this specific area of hardware during the acoustic stresses endured by the shuttle as her SSME’s power into life.

*Thanks to Mark Kirkman for GPC outlines used in this article.

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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