ET-118 heads into its critical flow

by Chris Bergin

Having arrived at the Kennedy Space Center (KSC) on Friday, External Tank ET-118’s ECO (Engine Cut Off) sensor change-out timetable has been set.

A smooth processing flow is required to ensure the tank remains within the timeline for the scheduled launch of Atlantis on STS-115 – and the standby STS-300 requirement in support of STS-121.

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Under normal circumstances, an External Tank (ET) would arrive at KSC, before being moved into a checkout/intergration cell in the Vehicle Assembly Building (VAB) for leak checks and other various testing proceedures – prior to being lifted from the transfer aisle for mating with its twin solid rocket boosters.

Due to the requirement for the LH2 ECO sensors to be swapped out, ET-118 will recieve the same convoluted proceedure ET-119 underwent upon its arrival at KSC.

United Space Alliance and Lockheed workers had evaluated the possibility of speeding up the process by conducting all the work in the vertical position, however new information – via a processing document date June 8 – shows that this appears to have been dismissed as unviable.

The document does confirm that Lockheed workers at the Michould Assembly Facility (MAF) are to head to KSC to help with the work that will involve USA technicians and engineers. ‘MAF crew being deployed to support tank processing at KSC.

‘MAF team staged to support ET-118 processing at KSC. ET DCR Preboard and Board complete, closure of open work in progress to support required milestones.’

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A number of days worth of preparation work is required before the ECO sensor R&R can begin, including LH/LO 17′ disconnect measure/adjust, the venting and purging of the tank and the building of a the clean room tent and scaffolding around the aft of the tank.
**ET 119 ECO R&R Article** 

On June 20, workers will chip away at the foam around the aft doom access hatch to allow technicians to enter the tank.

Following the replacement and leak tests, it is hoped the tank will be ready to be placed in the horizontal position for TPS repair (foam replacement) to the aft of the tank with BX-265 foam.

Loading into the intergration cell is scheduled for July 11.

Meanwhile, at MAF, ET-123 is now classed as on schedule in its processing flow, following a review to mitigate delays to the third tank to arrive at KSC this year.

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