Unthinkable before the loss of Columbia, a contractor engineer at Lockheed Martin was able to voice his concerns over the state of Endeavour’s damaged TPS (Thermal Protection System) – all the way to Mission Management Team (MMT) chairman John Shannon – within a matter of hours.
The engineer’s concerns, with both re-entering as-is and repairing via T-RAD/STA-54, were addressed via the arsenal of analysis that gave rationale to the decision that will see Endeavour come home – now likely on Tuesday – without a repair being required on her tile damage.
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Officially, only the highly conservative JSC Engineering department dissented as a group against the MMT decision, although Shannon didn’t note – or wasn’t asked – about individual cases of dissent/concern.
While it appears the vast majority of the engineering community concurred with the in-depth analysis and testing that took place in the days after the small gouge was spotted near Endeavour’s landing gear door, it also appears that everyone felt safe to give their input, and could rely on the backing of their own management.
The engineer in question – an expert in foam impact testing – voiced his concerns on Wednesday to his boss, Wanda Sigur, Vice President of Lockheed Martin’s External Tank project at the Michoud Assembly Facility (MAF) in New Orleans.
While the engineer did not demand to speak to the MMT, Sigur immediately passed on his concerns to John Chapman, head of the External Tank project at the Marshall Space Flight Center (MSFC), effectively Sigur’s NASA boss.
‘I received an email from one of our engineers expressing concern with the potential decision to re-enter the orbiter – either as is or with a putty repair,’ Sigur wrote to Chapman, forwarding the e-mail she had received from the engineer. ‘Notes from his email are below:’
‘The damage could be worst than what it appears,’ wrote the engineer. ‘During some of the impacts tests, we have what we called shear-out failures, where some of the impacts failed the tile at the densification layer, which it is designed to do. The problem is that not all of the failures lifted the tile out of place, but only cracked it 25-75 percent through that layer, leaving a tile partially attached.
‘With re-entry loads, it could fail the remaining portion and become dislodged during entry, leaving a large cavity, thus creating a more severe thermal issue. A repair to putty this area could also be detrimental, in that this could also aggravate the situation, making it worse.
‘I know they are performing re-entry testing on the tiles that mimic the shape of the damage area at JSC (tiles were CNC machined to the damage profile based on the 3D laser imagery taken of the damaged site) but not on a tile out scenario.’
Sigur – herself a mechanical engineer by trade – highlighted the engineer’s recommendation, before asking: ‘What are the appropriate channels to identify this?’
Her answer would come just seven minutes later, as Chapman wrote back: ‘I’d send it straight to John Shannon ASAP with a copy to Steve Poulos and Bill McArthur. Be sure to include contact info for your engineer so they can get more info / clarification if needed. If possible, he needs to attend this afternoon’s MMT meeting.’
Just over an hour later, the concern had reached the inbox of Shannon and other key shuttle management, with the original e-mail and contact details of the engineer, should they wish to call him.
Ten minutes later, the e-mail had been forwarded to other members of shuttle management, with a response on what was now becoming a chain e-mail, noting: ‘Please handle this as a Shuttle Safety Hotline submission.’
Ultimately, the initial note of concern, forwarded from Sigur, had made it all the way up the chain of command to all of the shuttle management, within 90 minutes, with JSC manager Robert Doremus confirming to all on the chain e-mail: ‘We will bring this up at today’s MMT.’
While it is not known how the engineer’s concerns were abated by the MMT, the ultimate decision that Endeavour was clear to come home, was taken the following day, with only the minor dissent of JSC Engineering noted.
As to when Endeavour comes home is now the main focus of NASA evaluations, with Tuesday currently the forward plan, due to the threat of Hurricane Dean. The hurricane may force a closure of the Johnson Space Center (JSC) which is the home of the Mission Control Centers that play a vital role in mission operations and the return of the orbiters.
‘There are discussions of ending the mission early in order to get home before the hurricane,’ noted one memo on Friday, which pointed to Tuesday as the cut-off date.
While backup facilities are available, NASA may find it prudent to ensure Endeavour is on the ground by Tuesday.
L2 users refer to the 62 page presentation on reccomendations to the MMT, downloadable on L2 – added to the additional presentations and notes, totalling over 600mb. Also includes specially ‘stitched’ super sized hi res images like the sample used in the article.
L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.
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