Tanks very much Lockheed and MAF

by Chris Bergin

With most of the data now analysed, Lockheed Martin and the Michoud Assembly Facility (MAF) have noted their pleasure in the performance of ET-119, which rode uphill with Shuttle Discovery during STS-121’s ascent on July 4.

While it was crucial for the tank to perform without issue – to allow the re-start of regular Shuttle flights – managers ensured their workforce didn’t go unpraised, many of whom are unsung heroes of NASA’s successful second test flight.

Only a few minor issues have been noted thus far, with electrical, propulsion, structural and thermal protection sytems all performing well.

Critical areas that were closely watched was the LH2 pre-pressurization ratios/counts – data which is still being analysed, plus the ECO (Engine Cut Off) sensors – with all replaced sensors working within their parameters. While an ‘old’ 5 percent sensor failed, a simple bypass ensured it would not play any role in affecting the launch.

Importantly, as noted in Lockheed’s Mission Success Bulletin, ‘The bipod and bellows heaters worked well, with no ice/frost noted. One bipod heater temperature sensor approached Launch Commit Criteria limits on the first launch attempt (July 1), but was switched to a manual control mode without issue.’

While the full suite of Developmental Flight Instrumentation (DFI) was not flown on this tank, important data was gained on how the tank reacted to the removal of its PAL (Proturberance Airloads) ramp.

‘Instrumentation data were successfully gathered from three of four Enhanced Data Acquisition System boxes on the Solid Rocket Boosters,’ added the report. ‘Available data are currently in review. Structural systems performed as expected as well, and ET disposal in the Pacific Ocean, south of the Cook Islands, occurred as forecasted.

‘Performance of the Thermal Protection Systems (TPS) received considerable attention and preliminary reviews suggest ET performance was good. Pre-launch TPS performance was nominal, and all ice conditions fell within required levels.

‘The two weekend launch attempts scrubbed due to weather conditions resulted in minor instances of crushed foam, cracks and minor erosion. What was expected to be a quiet Monday after two launch attempts changed suddenly with the discovery of a crack and subsequent small foam loss in the TPS on the inboard strut of the LO2 feedline. After a day of examination and analysis, NASA accepted a use-as-is disposition.’

‘The LO2 ice frost ramps (IFR) saw popcorning and typically minor erosion on about one-half of the ramps. No divots were observed. The Intertank IFRs experienced typical popcorning on two ramps and light to moderate erosion on most. As on the LO2, no divots were noted on the Intertank IFRs.

‘On the 16 LH2 IFRs, foam loss was typically isolated to minor popcorning on a majority of the ramps and light to moderate erosion on about one-half. Divots appeared in five areas, but all were within the allowable debris size. Probable causes include delta pressure, secondary impacts or void in PDL foam.’

The success of ET-119’s performance wasn’t just essential, but critical to the future flow of the remaining Shuttle manifest. Such was the media and industry attention on the tank, the pressure on a clean flight was clearly being focused on the workers involved with the fabricating, modifying and certification of the tank for flight.

However, what is often forgotten is that those very workers, especially the ones at MAF’s facility in New Orleans, have been to hell and back, following last year’s Hurricane Katrina. Not only did Mother Nature destroy infrastructure, but she systematically attempted to wreck the personal lives of the very people who – in a lot of cases – put their job roles with the Shuttle program before their own personal problems away from work.

‘The performance of ET-119 during ascent showed extraordinary improvement and is a direct result of tireless efforts of the entire ET team,’ said Wanda Sigur, vice president of the ET Project at Lockheed/MAF, who didn’t need to overplay the contributions made, given the team attitude that has been consistent throughout the last 12 months.

‘My thanks and appreciation go to everyone involved in supporting the STS-121 mission. It’s great to have a tangible sign that our hard work is paying off. STS-121 and the performance of ET-119 is that sign.’

However, simply ensuring ET-119 was ready for safe flight wasn’t the only concern that had to be address. ET-118 also have to stay within its scheduled flow, ready to be used on LON (Launch On Need) support, in case Discovery’s mission had gone seriously wrong, and required Atlantis to rescue the crew from the International Space Station.

Arriving at KSC (Kennedy Space Center) with a large amount of work incomplete, nearly 100 MAF workers travelled to Florida to ensure the tank complied with STS-330 LON requirements. With five days lost on the shipping date, and with its ECO sensors requiring the complex Remove and Replace (R&R) work inside the VAB (Vehicle Assembly Building), schedules placed just one day of contingency in the flow, raising concerns the tank was struggling to meet its deadlines.

However, MAF workers managed to turn the situation around, immediately setting about venting the Intertank foam, finishing external shakedown activities, completing Non-Conformance Documents deferred to KSC, and removing and replacing engine cut-off (ECO) sensors, beating their own deadline by six days.

‘When we were down before, we had to send all the data and photos back to Michoud where they crunched the numbers and sent it back to us at KSC,’ said MAF Business planner Bill Gilbert. ‘So we were losing a lot of schedule time getting dispositions.

‘This time we said why not bring all of our people with us up front, let’s attack all these areas, get all our dispositions and do our repairs. It’s on the spot, real-time processing.

‘The team was able to concentrate on high traffic PAL ramp removal and bipod areas to finish the tank shakedown three days quicker. Likewise with the ECO sensors, the team saved schedule time by getting all the mechanical and quality engineers to KSC early to review the paper with United Space Alliance and NASA, to decide the exact scope of work and to assign who was responsible for each task.

‘When ET-118 was moved to the horizontal position on the transporter after ECO sensor removal, the team made up more time by combining three hand packs of super light ablator into one on the bolts, the leakport and the attach points after the manhole cover had been reattached. This plan saved several cure times of 24 hours.

‘The crews averaged 70 workers from Michoud each day. In all, approximately 100 employees cycled through KSC to do their part, working two 12-hour shifts, seven days a week.’

Gilbert was coordinating with production manager Mike Holcomb, who noted that the trip to Florida only had one goal in mind, as opposed to the goals a lot of people travel to Florida for.

‘Not a lot of beach time,’ joked Holcomb. ‘(It was) a miraculous effort by everybody – TPS, ME’s, QE’s, QC’s and technicians. They all pulled together and worked in an out-of-position environment, having to go up and down 20 to 30-foot scaffolding. It was a real challenge.’

MAF workers who remained at KSC for the final elements of work on the tank did get some just rewards, however. 30 of the workers got to cheer Discovery – and their ‘other’ tank – launch uphill from the vantage point of next to the VAB, before returning to MAF to join in with work on the next tank to ship from the facility, ET-123 – set to fly with Discovery at the end of this year.

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