Michoud workforce praised as ET-120 is finally shipped

by Chris Bergin

External Tank ET-120 is finally on its way to the Kennedy Space Center, within schedule for LON (Launch On Need) rescue mission support for Endeavour’s upcoming STS-118 mission, earning high praise for the workforce from ET Project Manager John Chapman.

The tank, which has issues with its LO2 level sensors, will fly with Discovery on her primary mission of STS-120 in October.

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The tank is one of four that were sent back from KSC for Return To Flight (RTF) modifications, a huge and complex undertaking which challenged a Michoud Assembly Facility (MAF) workforce, a workforce that is still recovering from hurricane Katrina.

The tank still has work to be conducted on it, with the previously reported ‘resistance’ problems with LO2 level sensors. At present, it is not clear which sensors – given there are many sensors representing levels of LOX propellant in the tank – are being evaluated for potential removal and replacement (R&R) at KSC, or if further evaluation will take place before that decision is taken.

It appears, however, that R&R is the forward plan at this stage, which would take place at KSC, which may include the replacement of the Helium Inject Check Valve.

‘Several liquid level sensors in the LO2 tank are showing abnormal resistance readings,’ noted a NASA HQ memo. ‘The signatures have a potential to affect tanking operations on the day of launch. Much discussion is on-going as to the failure mechanism and the impact to performing an R&R of the sensors.’

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Regardless, the tank is deemed as within schedule, just, for achieving its first role for Discovery, with the standby rescue LON mission currently targeting a ready date of October 5.

Given the tank was originally due at KSC back in May, the ability of the workforce to work through modification issues – including the late ‘poke outs’ which included the level sensors – was commended by MSFC (Marshall Space Flight Center) boss Chapman.

‘I commend you (Lockheed Martin manager Wanda Sigur) and your team for the ABSOLUTELY SUPERB job on Monday’s Noon Board presentation on ET-120 LOX Loading Sensors and Helium Inject Check Valve R&R.

‘The charts were very informative and yet very succinct… a tough ideal to achieve in this highly technical business of ours. The quality of the presentation style, crispness of the explanations and responsiveness to the questions was also outstanding.

‘I know that many members of your ET Team at MAF have not had much rest over the last few months. Please take solace in the realization that it is through THEIR tireless efforts and dedication that tomorrow ET-120 will begin its voyage to KSC to once again enter launch site processing as a full fledged flight asset.

‘The entire Space Shuttle Program, the Agency, and in fact the Nation are in awe of your accomplishment.’

The tank was finally rolled out of building 420 at MAF before 7am local time this morning, ahead of its five day journey by barge to KSC.

‘Current Schedule is to Offload ET-120 at the KSC Turn Basin on Sunday (07/29) and Lift into H/B-2 on Monday (07/30),’ confirmed processing information on Tuesday.

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