ET-123 may hold back STS-115

by Chris Bergin

The projected second Shuttle mission of 2006, STS-115, may be pushed down the schedule, due to a slip in the production process of ET-123.

While ET-118 – soon to be shipped to the Kennedy Space Center (KSC) – will actually fly on STS-115 with Atlantis, ET-123 is required at KSC in time to support the stand-by rescue mission (currently tagged STS-301).

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Documents acquired by point to ET-123 now hitting a critical production path, with technicians and engineers all being moved to ET-118 work, to ensure that tank makes it to KSC in time to support STS-121 with STS-300.

Added to the need for a re-work on areas of ET-123, its projected shipping date of August 7 is now under review. This situation was highlighted during last Thursday’s PRCB (Program Requirements Control Board) meeting.

Just last week, Wanda Sigur, ET Project vice president at Lockheed Martin, noted that all available workers are being allocated to ET-118.

This requirement is described as ‘jeopardizing ET-123 production’ on the acquired document.

STS-115, currently on the schedule as NET (No Earlier Than) August 28, sees Atlantis re-starting ISS (International Space Station) assembly flights, carrying the P3/P4 truss uphill to the outpost.

The supporting LON (Launch On Need) date in support of STS-115 is November 11, currently tagged STS-301, although that will revert to the STS-300 designation once STS-121 (Discovery) stands down the need for a supporting rescue mission this July.

Shuttle managers, working alongside the Michoud Assembly Facility (MAF)/Lockheed managers will have to come up with a recovery plan, which will likely come into effect once ET-118 is shipping to KSC.

However, MAF information notes the following: ‘Cell A processing, impacting critical path, due to resource allocation required to support ETs 119 and 118 and rework associated with ET-123 Intertank stringer, TPS injections and thrust panel pocket TPS spray.’ It is not clear how much time will be impacted on ET-123’s schedule with this re-work.

Live updates and information resulting from the PRCB are available on L2. Full PRCB Documentation relating to this article will be available on L2 from the weekend.

Also adding to MAF’s workload is the continuing issue of the ECO (Engine Cut Off) sensors – this time with ET-118.

Following ET-119’s R&R work, it has come to light that the current stock of ECO sensors being used in all the current ETs are from the ‘same build time frame as ET-119 and ET-120 sensors,’ and have a ‘history of measurement anomalies associated with ‘loose swage’ (possibly related to tooling fatigue) from that build time frame.’

The PRCB heard that a recommendation to replace the ECO sensors in ET-118 is the best option open to engineers, with the remaining question on whether to carry out the work at MAF or KSC.

‘ET-118 ECO sensors removal/replacement recommended due to eliminate suspect ‘loose swage’ condition,’ noted the information acquired. ‘Option 1: R&R sensors at MAF. Option 2: R&R sensors at KSC.’

Option 2 appears to be the preferred process of changing out ET-118’s sensors, as ‘ECO sensor R&R at MAF would drive completion date.’

While ET-118 is still expected to be shipped with plenty of contingency time to support STS-121 through the STS-300 requirement, the continued lack of work on ET-123 is likely to add to the schedule slip of that tank, note sources – and with it the possibility of STS-115 launching close to its current NET launch target.

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