Ever since the tragedy of STS-107, the main focus on shuttle safety has been concentrated on reducing foam and ice liberation from the External Tanks, primarily during first stage – and early second stage – ascent.

2008 has marked a breakthrough year for MAF, with tank performance improving mission on mission, thanks to a variety of mitigation techniques that have been implemented at the New Orleans facility.

Most of those engineering changes to the TPS (Thermal Protection System) foam has been centred around the removal of as much foam as possible from the tank in areas that could liberate and strike the vehicle – most notably from the Ice/Frost Ramps that run down the side of the tanks.

With the post ET separation photography confirming the least amount of lost TPS on post RTF record, only three minor areas of TPS loss – backed up by an extremely clean orbiter, with no notable TPS damage suffered by Endeavour – ET confidence has been added ahead of the Flight Readiness Review (FRR) season for STS-119.

“Ascent: Nominal performance for all systems – no requirement violations. (3) foam debris events observed during review of imagery assets. (2) from LH2 tank acreage TPS and (1) from Intertank acreage TPS,” added the post flight IFA (In Flight Anomaly) presentation on L2, with a fourth minor area of TPS cosmetic damage also noted.

“Debris size, mass, and time of release were consistent with expectations and within risk assessment mass limits. ET-129 post-flight assessment complete and shows performance consistent with expectations and within requirements.

“(4) observations elevated as Post Flight Assessment Reports (PFARs) and assessed as IFA candidates. No new failure modes identified. No constraints or corrective actions required for STS-119/ET-127. No IFAs recommended for STS-126/ET-129.”

All areas of foam loss are understood, and relate to either cryopumping during ascent – a known condition, or small areas of manufacturing damage suffered due to “high traffic” of engineers working in certain areas of the tank.

Each area of interest gained expansive notes and data in the IFA presentation, before being closed as “known conditions”.

The tanks will always lose a certain amount of foam during ascent, and – as per former shuttle manager Wayne Hale’s comments on one of his many ET presentations – foam loss will never be zero.

However, with a few minor areas of additional modification due to be implemented on downstream tanks, the threat to orbiter safety has been – and will continue to be – greatly reduced, thanks to the fine efforts of the ET engineering community.

“The tank looked phenomenal. ET-129 really performed great,” wrote ET manager Mark Bryant. “Three small foam losses: On Intertank acreage forward of the Liquid Oxygen feedline fairing; on Liquid Hydrogen (LH2) tank acreage just aft of the ‘+Y’ bipod; and adjacent to the Station 1528 Ice Frost Ramp on the LH2 tank – all consistent with previous flight.”

Bryant added that MMT (Mission Management Team) chair LeRoy Cain, said of ET-129 “This is just flat (out) amazing,” when given the overview of the tank’s performance.

“LeRoy asked me to give kudos to our workforce; he was that pleased with the tank’s performance, (and) hence the condition of the Orbiter.”

Bryant also added that in a post-launch performance review one week after lift=off, observers noted that the ET electrical and propulsion systems performed as expected pre-launch and post-launch. The structural and Thermal Protection Systems also performed nominally post-launch.

STS-126 was Bryant’s debut launch as ET manager, which is one of the longest shifts on L-1, due to the early tanking of the ET and the obvious need to monitor the performance of the ECO (Engine Cut Off) sensors during that procedure.

Despite this, Mr Bryant noted he wasn’t nervous – thanks to assistance from Lockheed Martin’s highly regarded ET head Wanda Sigur and Chief Engineer Jeff Pilet – as the countdown proceeded down to the T-9 minute poll.

“Wanda checked in with me often, and actually I wasn’t that nervous. You’ve trained for this. You have great people around you doing their jobs,” he added. “Chief Engineer Jeff Pilet was, as usual, on top of things and kept me apprised of the tank’s condition and the Launch Support team. The Mission Support Room and Huntsville Operations Support Center were also on their game.

“When MMT Chairman LeRoy Cain conducted the roll call before coming out of the 9-minute hold, he called us first and I was able to confidently say, ‘Lockheed Martin (ET) is GO for launch.’”

As per NASA tradition a tie cutting ceremony was performed for Bryant’s first successful launch in his new position.

Other MAF challenges during 2008 related to being able to ship the tanks to Florida in time to support the manifest. At one point, several tanks were over a month down on their required shipping dates, before MAF managers utilized the results of several Technical Interchange Meetings (TIMs), along with additional shifts for the workforce.

Before the delay to STS-125, all the tanks were back on schedule. And while the 2008 manifest remains fluid, 2009 has been relieved of all schedule concerns thanks to the hard work of the past 12 months.

Two tanks are currently in residence at the Kennedy Space Center (KSC) – ET-127, previously set to fly with STS-125, but now flying with Discovery on February’s STS-119 mission, and ET-130 – which recently arrived to take the place as the Hubble Servicing Mission ET, should STS-125 remain on target for a May, 2009 launch.

At MAF, five tanks are undergoing major production, which reaches into the 2010 shuttle schedule. All these tanks are either on or ahead of schedule, which is the first time a set of downstream tanks have had their shipping date pressure removed from the equation since RTF.

“ET-131 (STS-127): The ET is in final assembly flow, with all operations proceeding nominally,” noted the Lockheed Martin/MAF status on ET production, on L2. “Will probably work only a couple of days during holiday outage. Still checking the February 22 date for delivery of tank.

“ET-132 (STS-128): The ET is in final assembly flow, with all operations proceeding nominally. Tank was laid down out of Cell A. Has been moved into Final Assembly 3; allows them to get into some dual tank flow.

“ET-133 (STS-129): Will perform LOX intertank flange closeout spray (which has already begun), no work required over holiday period.

“ET-135 (Currently STS-131) LOX tank was moved into Cell K. After cleaning, exterior of tank has been primed. Doing inspections on that priming now.

“ET-136 (Currently STS-132): Hydrogen tank moved out for proof testing. This will take about five to seven days, and then it will move into post-proof inspections (now completed).”

In a few months time, MAF expect to know the outcome of the Shuttle Extension status, which currently calls for at least five additional External Tanks to be built.

As part of the assessment, MAF managers have worked their funding requirements and floorspace plan, the latter relating to required handover of space to the Constellation program. Their results are understood to be favorable in support of an extension.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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STS-126 is proceeding without issue, and is currently slightly ahead of the timeline. A smooth transition for the MPLM to the ISS was vital, to allow the crew to begin their series of transfers that will play a major role in providing equipment for the future six person crew on the Station.

“MPLM Docking to Node 2 Nadir: MPLM mated to Node 2 Nadir for the first time on ULF-2 (STS-126). The system functionality is the same as when berthed to Node 1,” noted an associated Flight Readiness Review (FRR) presentation.

“All procedures and flight rules have been updated to account for the change in location. Lessons learned from previous MPLM flights (were) reviewed and updated in the MPLM procedures to capture any changes/workarounds required.”

Seven tons of cargo was packed into the MPLM, which also included the utilization of the aft endcone, making STS-126 the heaviest logistics flight in shuttle history.

“MPLM and Stowage first time to berth MPLM to Node 2 Nadir. First flight of a completely full (16 racks) MPLM. First flight of MPLM Aft Endcone Stowage,” noted the mission firsts in the FRR presentation, which also noted that additional items will be returned from the ISS after the docked stage.

“Return cargo mass is less than the assumed mass used in the minimum VLA (Verification Loads Assessment). ISS Program Office (was) attempting to find more return items.”

The transfer of items from Endeavour and the installed MPLM will take up a large part of the mission, which will prove to be challenging to the crew. However, managers recently cited the maturity of the STS-126 crew to ably pace themselves to complete the required tasks.

“Transfer status: Middeck: 33hrs of around 30 hours generic requirement. MPLM: 86:15 hrs of the (around) 85 hrs previous estimated requirement. Revised estimate increases requirement to 100 hours.”

The Mission Management Team (MMT) are continuing to evaluate the huge array of imagery gained on Endeavour’s ascent on Friday, via FD2 and FD3 inspections, with several items still being worked by the Damage Assessment Team (DAT).

Items of interest include a couple of areas of minor – almost cosmetic – damage to the aft of Endeavour, such as OMS Pod tiles and the SSME (Space Shuttle Main Engine) dome heat shield. They are likely to be cleared.

“Port Side T-0 FRSI and TPS nominal – additional imagery provided data. LH2 T-0 plate 16 mm film review completed by KSC imagery Team. Identified potential of solid ice in the area – dimensions being determined,” noted a TPS presentation on L2, referencing what was initially thought to be a strip of thermal blanket.

“AFT Flight Deck Complete – OMS Pod discrepancies noted: 4 Gap Fillers protruding frayed/2 Tile Damages. LESS Carrier Panel Inspection Complete – No damages identified.”

Importantly, no damage has been observed on Endeavour’s critical TPS systems, as evaluations into RPM imagery (selection available in L2) continue.

The first area to be cleared was the starboard side of the vehicle – which was required ahead of MPLM unberthing, due to clearance issues with the OBSS (Orbiter Boom Sensor System), had a Focused Inspection been required.

“All RPM imagery has been downlinked and is being reviewed by the Damage Assessment Team (DAT). In addition, the DAT has been reviewing the SRMS survey imagery,” noted information on Monday. “The Orbiter Project Office (OPO) cleared the starboard side of the vehicle and gave Flight Control a go for MPLM unberthing on FD 4.

“The Reinforced Carbon-Carbon (RCC) Leading Edge Subsystem (LESS) had no focused inspection (FI) requirements for the starboard or port wings or the nose-cap. The DAT is analyzing the imagery to formally clear the regions of interest for the FD 4 OPO (Orbiter Project Office) meeting.

“The Thermal Protection System (TPS) had no FI (Focused Inspection) candidates on the starboard side. There are some protruding gap fillers at various locations, tile coating damage near the Left-Hand (LH) External Tank (ET) door tile with shallow damage and a broken dome heat shield tile.

“The DAT is continuing the analysis process and is confident that these areas will be cleared.”

One gap filler referenced has been observed to be slightly protruding from below a RCC panel. It’s specific location is not yet documented. Another – less protruding – gap filler is also observed further down the wing.

While these will likely be cleared for re-entry, such a process may take slightly longer than most areas, due to the computational models required for how the gap fillers will ‘perform’ during re-entry. However, as of FD4, Endeavour has been cleared from any requirement of a Focused Inspection – a sign of how clean the orbiter is of damage.

The lack of any damage to Endeavour’s RCC panels and underbelly is thanks to what appears to be an amazing performance by ET-129′s TPS. Images taken from Endeavour’s umbilical well show a pristine tank, with only three very minor areas of foam loss.

A huge amount of improvements to the ET by engineers at Lockheed Martin’s Michoud Assembly Facility (MAF) since Return To Flight appear to be paying off, with no major foam loss from the tanks since STS-121.

Modifications will continue to take place on the tanks – although some items have been cancelled due to the vastly improved performance of late - with the end goal of making the final tank to fly with the shuttle the safest ever.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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