MAF effort sees External Tanks back on track to support STS-125

by Chris Bergin

Shuttle managers have been informed that the refined delivery dates for External Tanks ET-127 and ET-129 will support the October launch target of STS-125.

Another delay was feared last month when the shipping dates were still not within the timelines for STS-125 and the supporting Launch On Need (STS-400), but a superb effort at the Michoud Assembly Facility (MAF) has successfully moved the delivery dates back into line.

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Superb External Tank Effort:

Four tanks are deep in production at MAF, namely ET-127 (STS-125), ET-129 (LON/STS-400/STS-126), ET-130 (STS-119) and ET-131 (STS-127). It was delays to ET-127 and ET-129 that originally pushed STS-125 out to October 8 back in April.

Both tanks are required at the Kennedy Space Center (KSC) to support the dual processing flows that center around Atlantis launching from Pad 39A, at the same time Endeavour is sat on Pad 39B – ready to launch within days on a rescue mission, in the unlikely event Atlantis was seriously damaged during ascent.

A massive effort was carried out by MAF – not for the first time since Return To Flight – to find get-wells in the production schedules of the two tanks, no easy task due to restraints with the amount of workers at their disposal, and the fact the two tanks are only the second and third tanks to be built with new modifications that debuted with STS-124’s ET-128.

A TIM (Technical Interchange Meeting) resulted in an opening plan to improve the construction schedule, along with a seven days a week production plan that utilized ‘prudent’ overtime payments for the workforce.

“ET project has been closely coordinating with the SSP (Space Shuttle Program) Manifest and Scheduling office,” noted an overview presentation on making the October date for STS-125. “ET-127(STS-125) and ET-129(STS-400,STS-126) are currently under-supporting the current need-to-ship dates by 5 days and 13 days respectively.

“Production enhancement initiatives are being implemented with anticipation of bridging the delta between the current projected tank ship dates and the SSP desired ship date. Tanks are currently under 7 day/week production schedules, overtime will also be used as prudent and beneficial in order to improve on current ship commitments.

“In addition Lockheed (Martin – who build the tanks at MAF) has implemented collaborative work cells which will provide dedicated, experienced personnel supporting the manufacturing shop teams on a step to step/day to day basis, reduced the demand on technician resources via; revised Engineering acceptance criteria (primer/conathane application).

“Engineering drawing trim tolerances revision and reductions in test article processing. Current ship commitments are ET-127 – 7/15/08 and ET-129 – 8/9/08.”

Those dates have since improved by a number of vital days, courtesy of a smooth flow over the past month on the tanks – which has been key, given fears the effort would still be extremely tight to support October 8 for STS-125.

This concern could be seen via KSC’s response to the mitigation effort, which involved refining the processing schedule once the two tanks had arrived in Florida – a refinement that would have removed all contingency days from the flow involving the checks on the ETs in the Checkout Cell and through mating ahead of rollout.

“To take maximum advantage of improved ET deliveries and achieve the earliest launch dates possible, all critical path contingency has been removed from KSC processing schedules,” noted KSC as part of their efforts to keep to October 8 for STS-125.

“ET-129 delivery and processing for HST LON capability is the critical path for STS-125 HST. MAF deliveries of ET-127 and ET-129 under support KSC need dates by 4 days (each). STS-125/HST Launch to STS-126/ULF-2. Launch is a “launch to launch” duration of 33 days.

“Ground OPS has removed all contingency from their VAB, PAD, ET flows in a effort to minimize the potential launch slips. The KSC processing flows will be at “red” scheduling risk. MAF should try and ship ET-127 on 7/11 (O/D=7/18) and ET-129 on 8/5 (O/D=8/12) additional improvement could be used to restore pad contingency time.”

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With these schedules showing that MAF had to improve their shipping dates yet further to support October 8 for STS-125, managers at the Marshall Space Flight Center (MSFC) set a goal to move the shipping dates further to the left.

“Currently there is a around a one week disconnect supporting the proposed launch dates. MSFC-ET will continue to try and improve the delivery dates, some more improvements may be possible. A new planning date is needed for the other project elements or negative work will occur.

“Approve these dates (Oct 8 for STS-125 etc.) as a interim step and continue to review the schedules and monitor planning versus execution of work.”

Indications that the effort had proved to be a success were first hinted by Shuttle manager John Shannon a few days ago, when he noted: “Got a report at the schedules telecon that the ET team is back on track and appears can support the manifest with some margin. That was a great story.”

This is backed up by the latest report on the processing of the tanks at MAF, via Lockheed Martin on the Shuttle Stand-up/Integration report.

“ET-127: Tank is in final assembly. On track with all test and checkout activities. On TPS (Thermal Protection System), poured +Y LOX clam shell. Doing press and trims for aft manhole cover closeout. Continue to work LO2 feedline yoke closeouts. Prepped to do LH2 outboard support arm application.

“Continuing with final cable tray cover installations and closeouts of +/-Y vertical struts. Showing a July 14 versus July 11 need. If continue to show progress on test activity, which is primary critical path, expect date to continue migrating back to the left.”

“ET-129: Tank is in final assembly. Did sprays on both +/-Y longerons for re-design closeout activities. Will continue with those spray activities. Installed last LOX feedline section (elbow section going down into intertank), and struts were attached. This puts them into all the PDL closeout prep activities. Sprayed +Y bipod; will do trims on this. Will go into -Y bipod spray going forward.

ET-130 – in Cell A at MAF, and ET-131 – in the High Bay of the facility, are both proceeding through their various stages of construction without any schedule concerns. ET-130 had suffered a hit of several weeks earlier in the year, but this has been more than mitigated, indirectly, by the delay of STS-119 to February, 2009.

However, should there are any further delays to the tank’s shipping dates, a back-up plan is in place for additional work to be carried out after they have been delivered to Florida is available. The plan, added to the “zero contingency” days at KSC, practically ensure STS-125 can launch on schedule, bar a major delay in the flow.

“From Ground Operations: ET deliveries have improved by the combination of several successful initiatives by MAF and KSC.

“KSC personnel are being trained and certified so several task usually performed at MAF can be done for the most part in parallel with ET stand alone work at KSC. That along with resource augmentation and process improvements resulted in a much shorter ET on dock to launch template.

“STS-125 (HST) and STS-400 (LON) /126 (ULF-2) will be parallel VAB/Pad processing to provide LON capability for HST SM4.

“Advance planning for this parallel activity required careful task scheduling to manage resource limitations (availability of resources and specific skill requirements). It was also necessary to avoid facility, vehicle power/test, and flight hardware milestone movement conflicts.

“To take maximum advantage of improved ET deliveries and achieve the earliest launch dates possible, all critical path contingency (remains) removed from KSC processing schedules.”

With the launch dates now appearing solid for October 8 and November 10 for STS-125 and STS-126 respectively, managers have been able to assess various changes to the missions.

This includes a target of launching STS-126 prior to November 28, due to the beta angle cut-off.

“From Flight Operations: For STS 125 launch date change results in 550 lbs ascent performance gain. For STS 126 launch date change results in 230 lbs ascent performance loss,” noted associated information.

“This new launch date satisfies the mated beta angle constraint, however launch dates from approximately 11/28 through 12/16 will violate the mated beta angle constraint.”

“After the October 8th HST launch, Pad A post launch turn around activities and STS-126 Payload (ULF-2) delivery to Pad A will be performed in parallel with STS-400 LON standby at Pad B.

“Once released from HST LON support, the STS-126 SSV (Space Shuttle Vehicle) will roll to Pad A for Payload installation and vehicle preparations for the STS-126 launch on November 10th.”

This fine cross-center effort, which usually goes unreported, also protects the 2009 missions, which is currently scheduling five missions that will see the completion of the ISS’ assembly.

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