ET work – positive progression

by Chris Bergin

NASA managers have been meeting on Thursday – during their weekly PRCB (Program Requirements Control Board) summit – to discuss Shuttle logistics and processing, while evaluating the status of return to flight operations.

The meeting is understood to have given positive indications that STS-121 will target a May window (stretching from May 3 to the 23rd), along with the potential for three more missions during the remainder of 2006.

This was supported by new processing data on the next three External Tanks (ETs) to ship out of the Michoud Assembly Facility (MAF).

NASA is hoping to launch a maximum of 19 flights during the final four and a half years of Shuttle operations, 18 to the International Space Station and one to service the Hubble Space Telescope (mission HSM-4). A smooth transition to regular flight operations will be largely dependant on a ‘clean’ STS-121 test flight with Shuttle Discovery.

ET retrofitting continues to progress at MAF, with ET-119 shipping out of the facility on March 3. to join Discovery as part of the STS-121 stack at the Kennedy Space Center (KSC). ET-118 – to be used on Atlantis’ STS-115 (and on standby for the STS-300 contingency shuttle crew support mission) remains to be given a firm shipping date at this time, although it is estimated to leave New Orleans on April 7.

ET-119 is currently housed in Building 420, Cell 2 at MAF, with ET-118 located in Horizontal Final Assembly, Position 1, with its PAL ramp now removed.

The complexity of preparations on the ETs go further than simply removing the protuberance airload (PAL) ramps from all ETs to be sent for flight operations, as revealed by a ‘Super Board’ meeting of the ET project at Lockheed Martin Michoud Operations late last week.

‘Right now, we’re finalizing the design of ice frost ramp extensions where we’ve removed the PAL ramp,’ said External Tank Project Vice President Wanda Sigur, in a MAF address to workers. ‘We’re in the process of validating that design on ET-94.’

ET-94 – as opposed to ET-120 – has become the main test bed for evaluating modifications to the ET, including ice frost ramp validation work and ECO (Engine Cut Off) sensor inspection.

‘Engineers and technicians are also developing test programs that will verify an ET design without PAL ramps. Testing should begin in a few weeks and take several months,’ Sigur added, before noting the obvious conflict in shipping and final testing dates, before the modifications have been fully validated.

“What’s unique about this is that we are working with our NASA customer to proceed with production and delivery in advance of a Critical Design Review (CDR),’ she added. ‘In lieu of a CDR, a number of integrated reviews will be held to assure that the hardware is appropriately designed and in process control.’

MAF engineers are currently working on sealing leak paths around the bipod wiring area on the tank, with a gluing, bonding and sealing process being actioned.

‘We’ve completed validation of the bipod harness sealing process, and production has started on ET-119, the next tank to fly,’ said Sigur. ‘The team is also working to validate the wire bonding process, which glues the wires to the tank. The team has also successfully worked some bipod insert issues at the fitting.

‘The plan now is to deliver ET-119 by March 3. ET-118 has moved up and now is the second tank scheduled to fly so ET-120 can be used for further data gathering. After ET-120’s return to Michoud in October, workers found cracks in the PAL ramps. The tank experienced two cryoloading cycles at Kennedy Space Center last spring.’

At MAF, ET-119 and ET-118 are scheduled to support a May window for STS-121, with ET-123 undergoing work in MAF Building 103, Cell 2. ET-123 is already moving along the time line, with good progress being made on Flange foam removal and Ice/Frost ramp removal tasks. That tank is set to fly with Endeavour on STS-116, currently on the manifest as a NET (No Earlier Than) date of October 1.

The impressive progress made by MAF – a testament to a workforce that has suffered a huge degree of personal turmoil and disruption following Hurricane Katrina – could be highlighted in the next STS flight manifest.

The previous manifest, the October 19th Flight Assignment Working Group (FAWG) Planning Manifest 05D-12, pointed at a 19 flight schedule, with four flights in 2006 (May, July, October, December). Should those dates remain roughly the same when the next manifest is revealed in the coming days, a wave of optimism is bound to sweep across the Shuttle program.

However, caution continues to be urged by sources associated with the Shuttle program, with a safe, clean and successful second test flight of Discovery on STS-121 being the singular focus of attention, ahead of any pre-emption of a return to regular flight operations, operations that are always prone to delays.

Useful live update threads:

PRCB and Flight Manifest latest: 

External Tank Update Thread 1:

New External Tank Update Thread:

Orbiter Specific Forum Section:

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