NASA managers will decide on one of eight options over the next seven days, options that will mitigate the problems associated with the LH2 Feedthrough connector, which was identified as the cause of the recent ECO (Engine Cut Off) sensor/circuit issues.
Three of the options hold potential for allowing STS-122 to target launch on January 10, while the other five incur delays ranging up to around February 15.
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A brilliant engineering effort pre-empted the identification of the issue – one which was tagged as the leading culprit days ahead of Tuesday’s tanking test.
Use of the Time-Domain Reflectometry (TDR) equipment came as part of a plan that been long in the making, as engineers made a concerted effort to get to the bottom of the problem that was causing the related launch scrubs.
At the center of the efforts has been Ed Mango, a long time shuttle/orbiter manager, who was hoping his troubleshooting plan would gain the data required via similar failures during the tanking test.
‘It has been a long two weeks for many of us, but here we are ready to test our spaceship and try to determine what is going on with the ECO System. The Launch Team has done very well in getting the requirements, procedures and preps completed. The Troubleshooting Team has developed the best way to capture the failure,’ he wrote to his team ahead of the tanking test.
‘I know we are ready for tomorrow (Tuesday). The data will drive us. Evidence of a failure will be outstanding news because of the tools we have in place to capture the location and other characteristics about the condition. Lack of evidence of a failure within the ECO System will allow us to think differently about our Go Forward plans.
‘I feel honored to represent this team and am taken back by all that was accomplished in about a weeks time. A clear, methodical, ‘can-do’ attitude is what each of you had to get us to this point. The energy by everyone was contagious, and helped foster our ability to be comfortable with our test plan for tomorrow.’
Go Forward Plan:
Those ‘Go Forward’ plans are now being evaluated, ahead of a decision on which path to take by PRCB (Program Requirements Control Board) during this week – or possibily next week.
Of the eight options, only one notes a plan of leaving the connector hardware in place ‘as-is’ – an option which appears likely to be dismissed. Information following the test recommends taking the opportunity of removing and replacing (R&R) the connector to allow for forensic examination.
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Information on the available options under evaluation also note that there are only a limited number of options can be done on pad within current NET (No Earlier Than) launch target – that opens on January 10. However, that launch target has not yet been ruled out.
The options show targeted completion dates for the work involved, with all but three options allowing for the stack to remain at the pad.
The opening option – which involves further testing, but no replacement of connector hardware in the tank – allows for work to be completed by January 4. However, this option is being noted by sources as unviable.
The following two options are gaining a lot of attention, with both procedures showing completion dates in time to make the January 10 launch date. These two options (Option 2 and 3) involve replacing the external element of the connector with ‘cherry-picked’ pins/sockets from existing stock.
Further options, such as option 4, involve larger changes to the make up of the connector, replacing the external plug of the connector with an internal plug, which would eliminate the element of hardware believed to be the cause of the problem. This option, however, would not allow for work to be completed until January 25.
Option 5 has a similar schedule, involving the soldering of the external sockets – allowing for a better Pin/Socket connection. Qualification and testing takes up the bulk of the schedule with this option, but is the final option available for work at the pad.
A requirement to rollback is based around the internal elements of the connector, which would require the clean room environment inside the Vehicle Assembly Building (VAB) – last seen during the ECO sensor replacement work on two previous tanks.
A PRCB meeting on Wednesday is likely to reduce the options yet further, before making a final decision – within a week. In the interim, each favored option will have its schedule refined.
In parallel, more data is being gathered on the connector hardware via testing at the Michoud Assembly Facility (MAF) in New Orleans. This will allow for additional data not only for the mitigation efforts for STS-122 and STS-123, but for future flights down the schedule.
‘Testing is underway at MAF and at MSFC on feedthrough connectors. This testing is aimed at answering questions about the plausibility of cryopumping through the connector/wire harness assembly, nanofocus x-ray examination of connector response to cryo temps, and failure analysis of the ET-120 external connector non-metallics,’ added information.
Following the conclusion to Wednesday’s PRCB, managers decided to give the gohead to start removing foam from the aft of the tank at the manhole access point. This work will take place this weekend.
Further updates/articles will follow…
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