Managers delay STS-134 ET/SRB mate ahead of tank allocation options

by Chris Bergin

With STS-135 heading into mission planning for a June 28, 2011 flight – pending the required funding being passed by lawmakers – managers have opted to delay the mating of STS-134’s External Tank (ET) and Solid Rocket Boosters (SRBs) to December, in order to allow a potential tank swap between ET-138 and ET-122. Meanwhile, a role for ET-94 has again received a mention.


The decision allows for the option to fly the “last newly constructed” ET with STS-135, which would move the refurbished ET-122 to STS-134 with Endeavour.

“We’ve moved back the date for the 134-ET/SRB mating to early December which will give us the option of either putting ET-122 or ET-138 on the STS-134 flight,” confirmed the latest Staff Senior Meeting Notes (L2).

ET-122 – scheduled to be ready to ship next month – was damaged when Hurricane Katrina impacted on the Michoud Assembly Facility (MAF) in the New Orleans region. With the addition of the STS-134 flight with Endeavour to the Shuttle manifest, ET-122 won back its ticket for a ride uphill.

STS-134 debuted on the latest FAWG (Flight Assignment Working Group) manifest in 2008 as the LON (Launch On Need) support for STS-133. Once Endeavour’s mission was baselined with the AMS payload, ET-122 – partnered with Atlantis – was assigned as the LON support of STS-134, under the designation “STS-135, LON Support for STS-134” – soon to change to the STS-335 call sign.

ET-122 had already been pre-empted for a potential return to the NASA manifest by Lockheed Martin’s ET Program Manager Wanda Sigur in 2008.

“Hurricane Katrina damaged ET-122 in Cell A when concrete fell from the roof and hit some areas of the tank,” noted Sigur at the time. “We’ve been asked to put together a proposal about ET-122 to determine how and when the tank could be returned to the fleet for NASA to evaluate.

“We are working on that. ET-122 could be used possibly as a launch-on-need tank or for other NASA objectives in the future.”

With ET-122 now coming to the conclusion of its production phase at MAF – which has included the Return To Flight (RTF) modifications – the option to fly ET-122 with Endeavour on STS-134 may be prudent. While the tank will clearly be safe, STS-135 will be the first post-Columbia mission to be without Shuttle LON support.

The likelihood of the move also increased via the latest SSP “FAWG – Flight Assignments Working Group” manifest (L2), which shows ET-122 with STS-134 and ET-138 with STS-335/135 – a mission that reflects the latest decision to push forward with the flight pending the political process, via the payload change to mission content.

Atlantis’ role will technically remain that of a LON flight until STS-134 safely lands, providing the potential for a Contingency Shuttle Crew Support (CSCS) replenish for the International Space Station (ISS), after hosting the STS-134 crew in the highly unlikely scenario of a major problem with Endeavour’s health on orbit.

Rationale for utilizing the pristine ET-138 for the final mission – STS-135 – is also based on an unlikely event, relating to damaging foam/ice liberations during ascent. Should that highly unlikely event occur on STS-134 with ET-122 – Atlantis would at least be ready to aid with the rescue of the crew, with the brand new ET-138.


With the political refinements ongoing for NASA’s FY2011 budget proposal, the forward plan for Shuttle is starting to look a little more certain, with both the Senate and the House supporting the addition of STS-135. However, the Senate bill does leave the door slightly open for an actual shuttle extension.

Admittedly, an extension is unlikely at this stage of negotiations. However, with the all-but certain political approval of STS-135, and the continued move towards the immediate implementation of a development path for a Shuttle Derived Heavy Lift Launch Vehicle (SD HLV) in 2011, a level of viability exists for extra shuttle missions.

Three new tanks – at various stages of construction – exist in storage at MAF; ET-139, ET-140 and ET-141. However, none of these tanks could be completed ahead of 2012 according to the Space Shuttle Program (SSP).

One completed tank also resides in the New Orleans facility, known as ET-94. This “old” Light Weight Tank (LWT) would require refurbishment, such as the list of RTF modifications, but would also cost several thousand pounds in lost upmass, if it launched with a very notional STS-136 mission.

Regardless, that mission remains an option – as noted by managers this month – be it via a shuttle extension, or more likely playing an early role as part of the SD HLV test program.

“There have been a lot of questions about ET-94 which is our older light weight tank built in 2001,” added the Staff Senior Meeting Notes. “It’s been under configuration control and we’ve been working cost numbers for refurbishing it for either a flight unit or being modified into a Main Propulsion Test Article (MPTA) for whatever heavy lift vehicle comes next.”

Documentation (L2) associated with the HEFT (Human Exploration Framework Team) – a key body involved with the creation of NASA new exploration roadmap – also points towards an inline SD HLV configuration, with the Shuttle ET Diameter core and an identical make up as the Jupiter-246 HLV (article pending).

Along with the other SD HLV candidate – the Sidemount SD HLV – which also utilizes a Shuttle ET, having ET-94 ready to become the MPTA would ease the development cycle ahead of the completion of ET-139 for use with a Block I SD HLV.

For the interim, NASA managers are simply placing all their cards on the table as options, ahead of the conclusion of the political process, which will finally result in NASA gaining a solid and viable direction for the upcoming years.

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