Shuttle managers have concluded their meeting over the latest status of the troubleshooting efforts on ET-125, which is to receive new external LH2 Feed-through connector hardware, due to arrive on Friday.
The PRCB was presented with a forward plan that shows the new NET (No Earlier Than) launch date as February 8 – should they decide to conduct a tanking test. Without the test, they could aim for February 2. These date options are “expected” – while a protected January 24 option is deemed unlikely.
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Pre-PRCB Troubleshoot Latest:Testing at the pad and at the Marshall Space Flight Center (MSFC) has begun on the LH2 Feed-through connector hardware, in a dual troubleshooting effort to pinpoint the cause of anomalous Engine Cut Off (ECO) sensor system readings.
The external connector is now at MSFC for bench testing, with engineers aiming to install a new connector into ET-125.
Currently timelines note 25 days worth of work before United Space Alliance workers can return STS-122 into a launch configuration, for the commencement of S0007 Launch Countdown operations.
The connector hardware will be installed by a special team from the Michoud Assembly Facility (MAF), although a key factor will be the testing of ET-125’s external connector, plug and associated wiring at MSFC.
Testing on ET-120’s LH2 Feed-through connector failed to find conclusive issues with the hardware, before Onboard TDR (Time-Domain Reflectometry) instrumentation during third tanking identified open circuit condition at Feed-through location.
Work at the pad is continuing, in case the issue may be related to the internal hardware – which remains installed in the tank.
Should a problem be found with the internal connector over the coming days, to the point that it requires replacing, engineers would need STS-122 to rollback to the Vehicle Assembly Building (VAB), given no access to the internal workings of the tank can be carried out at the pad.
‘Fiberscope inspection of internal plug for evidence of corrosion, contamination and damage. Look into sockets,’ noted documentation on the current process at the pad this week. ‘Contamination sampling by KSC NDE. Perform transference burnishing on insert face and pin insertion/extraction into sockets, bag & tag for evaluation.’
‘Take X-rays of demated internal plug. Perform internal plug socket tine grip force test using sample pin and force gauge. 3 pulls per socket, all 37 sockets.’
The meeting of shuttle management, at the scheduled Program Requirements Control Board (PRCB) meeting, may also include the opening test results from MSFC on the external connector hardware.
Any culprits found during testing would provide hope that the fault is specific to the removed hardware, thus raising the chances of being just a month away from a potential launch date.
PRCB Newsflashes and decisions:
X-Ray results from the ET-125 internal feed-through connector at the pad showed no issues.
Pull tests on ET-125 internal feed-through connector showed no issues, comparable to ET-120 testing at MSFC.
ET Project to recommend to proceed with soldering of the feed-through connector pins on both ET-125, and ET-126 in the VAB, as forward plan for mitigation, due to all results to date pointing towards the external feed-through connector hardware as the most likely cause of ECO system anomalies.
‘ET Project implementing design solution that mitigates most likely root cause by soldering external harness / sockets to feed through connector receptacle pin. Redesign eliminates significant contributors to most likely root cause of STS-122 ECO circuit anomalies,’ noted Thursday’s forward plan.
‘Contamination / relative motion effects between external plug socket and feed through pins eliminated. Internal plug design unchanged as improbable contributor to anomaly – In-situ inspections / tests complete with no issues identified (i.e. contamination, hardware defects).’
New NET Launch Date for STS-122 presented to the PRCB as Feb 8 – should they decide to conduct a tanking test. If managers decide to skip the test, they could target Feb 2. (Click image for larger version).
The decision date for the Tanking Test option will be taken on January 21 – ultimately confirming which of the two NET launch date options will be taken for STS-122.
At the post PRCB teleconference, John Shannon noted a January 24 launch date being protected, before backtracking and noting that if things go as expected, they wouldn’t be launching before Feb 2. Schedules in Thursday’s presentations do not allow for Jan 24.
The above is based on several presentations reviewed by the PRCB on Thursday. A full overview article will follow on Friday.
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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