MAF History:

Michoud has played a vital role in building rocket hardware for many decades, best known to the current generation for its assembly of the large External Tanks that flew with the Space Shuttle.

Its history ranges as far back as the 1940s, building planes and landing craft during World War II, before switching its focus to building engines for Sherman and Patton tanks for use during the Korean War.

MAF entered the rocket business in 1961, when NASA tasked the facility with the construction of first stages for the Saturn IB and Saturn V launch vehicles, prior to their shipment by barge to the Kennedy Space Center (KSC).

Undergoing a similar transition to what it is today, Michoud had its attention switched to the construction and assembly of the Shuttle External Tanks.

The first of the 136 tanks, ET-1 for STS-1, rolled out of the door in June, 1979 – one of only two tanks to have its thermal protection system foam covered in white paint.

The latter period of its ET production role was filled with both tragedy and success, as STS-107′s External Tank became the focus of investigations into the loss of Columbia, after it shed a large piece of foam from its bipod ramp, critically damaging the ill-fated flagship.

The painful Return To Flight efforts resulted in major modifications to the External Tank, placing new demands on Michoud’s workforce, only for the region to be decimated by 2005′s Hurricane Katrina.

With large numbers of the MAF workforce displaced – some with their homes completely destroyed – the downstream ET manifest was under severe strain, just as NASA were hoping to pick up the pace on ISS assembly missions to complete the Shuttle’s final major role in space.

Under the leadership of key managers, such as the highly respected Wanda Sigur, the workforce rallied, adding shifts and working Technical Interchange Meetings (TIMs) to streamline the production practises, all while improving the safety of the tanks.

Their work proved to be successful, as confirmed by the “clean” performance of the ETs during the vast majority of RTF launches.

The MAF workforce managed to keep the ET schedule on track – aided by some misbehaving orbiters extending processing flows at KSC – and even returned one tank back into the mix. ET-122 was set to fly earlier in the program, before being damaged by Katrina. It successfully flew on STS-134 with Endeavour.

However, by the time the Shuttle Program was slowing down, the workforce already knew the promise of transitioning their careers into the Constellation Program (CxP) were dashed. As as result of CxP’s eventual cancellation, the vast majority of the MAF workforce were laid off as the final External Tank headed out into the Gulf of Mexico.

A large number of workers could have seen their careers saved, had it not been for the delays in implementing the plan for a Heavy Lift Launch Vehicle (HLV), outlined in the 2010 Authorization Act as the flagship of a realigned exploration program.

MAF leaders had hoped for an announcement within a timescale that may have allowed them to save a large number of workers, as was seen in their actions to extend the period prior to handing out WARN notices, several times, before finally losing patience with the politically motivated stalling tactics in Washington DC.

The impact to the facility was severe, as only a small group of skilled workers remained, spending their days removing equipment to make way for a line of Hollywood production companies to use the wide open floor space to film scenes for movies, such as GI Joe 2 (Retaliation).

MAF Fightback:

Signs of Michoud returning to life were small, with the BP oil company taking control of Building 451 – otherwise known as the LH2 proof test building – to store the blow out preventer that caused the Gulf oil spill in 2010, while Boeing utilized the MAF machinery to build a small pathfinder tank.

The last remaining ET – an old and usable LWT named ET-94 – was moved into storage in Building 103, while several part tanks – such as ET-139, which provided a test bed for work surrounding the Stringer crack issue suffered by STS-133′s ET-137 near to the end of the program – were sold to scrap merchants.

Elsewhere in the facility, work began on Orion, resulting in the construction of the Exploration Flight Test -1 (EFT-1) vehicle, which has since shipped to KSC for outfitting. All future Orions will be born at Michoud, with work on the Exploration Mission -1 (EM-1) Orion scheduled to start as early as next year.

Orion will also gain a neighbor in the form of new Dream Chasers, following a deal between Sierra Nevada Corporation (SNC) and Lockheed Martin that included MAF in the role of building the composite airframe for new spacecraft that will be launched atop of an Atlas V.

However, the bulk of MAF’s future work will be on the huge SLS rocket, with large-scale efforts now taking place to modify several buildings to host the fabrication and assembly of the HLV at the facility.

Multiple projects are scheduled through 2014, involving modification and construction projects in Buildings 103, 110, 114, 115, 131 and 451.

Under the watchful eye of ET-94 in Building 103, Michoud’s main manufacturing building – encompassing 42 acres under its roof – is being modified to welcome the Robotic Weld Tool 3. Scheduled for completion by May, the tool will be used to make dome components for SLS, and will be known as the Enhanced Robotic Weld Tool when in operation.

This large factory floor space will also host the segmented ring tool, dedicated to fabricating L and Y rings for the SLS vehicle. These rings are used to make barrel-to-barrel and dome-to-barrel connections within the SLS rocket’s structure.

The tooling installation work – which has already seen circular steel structures rise out of the floor – should be completed this month, with test and checkout procedures to follow immediately.

Repurposing the facility since the demise of the Constellation Program can be seen in Building 115, as engineers modify the high-bay manufacturing building by installing weld tooling that will fabricate the barrel components for SLS. Known as the Vertical Weld Center, the friction-stir-weld tool will stand about three stories tall once fully assembled. The work is scheduled for completion in June.

Over in Building 110, the demolition work on Cells B and C – which once hosted fully constructed External Tanks for TPS foam application – has been completed.

Preparations are in now full swing for the installation of the Vertical Assembly Center (VAC), a location where dome assemblies and the tank barrel sections will be joined together to complete the “dry structure assemblies”.

This huge piece of hardware should be in place by March, 2014 – becoming the world’s largest friction stir weld machine.

In Building 131 – previously used for the cleaning and primer application for the Shuttle ETs – repurposing work is taking place enable it to host massive SLS sections for foam application.

Because SLS is so large, the roofline of the building is being extended north. Engineers are currently breaking up the tarmac in front of the building and adding to the existing foundation in preparation for the building work.

Notably, the SLS stages will depart from MAF without any white paint, despite NASA images showing a “Saturn V” type paint scheme for the monster rocket. As such, SLS will have an “orange” core, with the appearance of a large Shuttle External Tank.

Roofline and foundation extensions are also taking place in Building 451, similar to building 131, allowing for additional space for proof testing of the LH2 tank on SLS’ core stage. Space in the building is being created by removing what is known as the “beer can,” a barrel-shaped structure for holding the structure in place during testing.

While KSC continues its efforts to attract several vehicles to be part of its “multi-user spaceport” aspirations, MAF has already secured its place as a facility that will be birthplace of both commercial and government vehicles for the decades to come.

(Images: Via NASA and L2 content from L2′s ET and SLS specific L2 sections, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site.)

(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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SLS Core Material:

In 1998 – after a challenging four year development program that kick-started NASA’s knowledge about Al-Li alloys – STS-91 flew the first SLWT.

This tank had been re-engineered to use Al-2195 and Al-2090 extensively, which were stronger and lighter than the Al alloys on LWT (Al-2219, etc).

Together with the first use of an orthogrid structure – on the LH2 tank’s barrel – this lightened the structure and improved payload, especially to the high-inclination orbit of the International Space Station (ISS).

However, those new alloys were also more brittle and difficult to weld, and experience showed a maintenance overhead. All of the dome and ogive sections were reverted back to aluminum over three subsequent revisions – first flown on STS -116, -119, and -130 respectively.

At the same time, SLWT experience allowed the LH2 orthogrid to be further optimized and lightened from STS-119.

But the Space Shuttle Program (SSP) wasn’t finished with problems with Al-Li – the intertank stringers which failed during STS-133 tanking and had to be reinforced, were Al-2090.

Notably, SLS will move completely away from the stringer design for its intertank, which carries much higher loads supporting a larger LO2 tank, an upper stage, payload and PLF – all at higher G’s, and with greater aero and bending loads than the ET.

The new design will have integrally machined stiffeners instead of riveted sheet metal stringers.

Similarly, the components which failed during a recent pressure test of the Exploration Flight Test -1 (EFT-1) Orion flight article were also Al-2195.

Meanwhile, a Shell Buckling Knockdown Factors (SBKF) project has been running at NASA Langley since 2007, funded by the SLS Advanced Development Office since Q3 FY12.

Launch vehicles need to allow substantial margins to avoid their tanks, intertanks and interstages buckling during launch. Rules for this were set by experiments in the sixties, but the state-of-the-art in analysis and construction has moved on a long way since then.

The engineering team are re-writing the rules for large vehicles via a combination of analysis and experimental verification, leading to a 2011 “can crush” test where they used a million pounds of force to buckle an “External-Tank-like Test Article”, which was 8.4m in diameter and 6.1m tall.

The team has already produced a first draft of their guidelines. In addition, since early 2012, they have been working closely with the SLS team on design of the core.

It is in this light that the SLS program recently reported a wholesale switch from Al-2195 to Al-2219 on the core. This “was based on a trade study that reduced payload mass by 3 t,” – taken from project reserves – “but that will result in approximately $30 million per flight savings.”

L2 sources confirm that Al-2195′s brittleness was the limiting factor when trying to beef up the structure for SLS.

Orthogrids – or possibly isogrid (as shown in the image to the left) – on the tank barrel are machined from flat plates, leaving stiffening ribs that ideally are tall (for strength, or more accurately, stiffness), allowing them to be thin (for lightness).

However, the ET was already using the thickest plate that could survive being formed to the tank’s 8.4m diameter.

Al-2219 is less brittle, so they can use thicker plate which can be reliably formed, and the thicker orthogrid actually results in a lighter structure overall.

Information also notes that the SBKF project has also been doing preliminary work on a new alloy. AL-2050 adds magnesium for an Al-Mg-Li mix, and “is already used extensively in several commercial aircraft”. This promises plates and orthogrids three times thicker than Al-2195 – up to six inches – with weight savings of as much as 20-30 percent.

This effort has been spun off into a Small Business Innovation Research project “to investigate material properties and structural design optimization for heavy lift LV cryotanks”.

It is possible that one day this could become the basis of a Super Light Weight upgrade to SLS.

(Images: Via NASA, TerraBuilder, Inc and L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site.)

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The GUCP:

The GUCP is a critical element of hardware, located at the end of the gaseous hydrogen vent arm. Attached to the External Tank, a plate holds a large-diameter pipe that collects excess hydrogen gas from the tank as it’s being filled with liquid hydrogen on launch day.

The venting system funnels it to a larger pipe that takes it down the fixed service structure and out to a flare stack that burns the excess hydrogen off safely. At liftoff, the GUCP retracts away from the tank, cutting off the connection.

Due to the importance of the GUCP’s connection to the tank ahead of lift-off, the hardware has sensors in place to watch for hydrogen leaking from the point of tanking operations, through to launch.

These readings are closely monitored by the team in the Launch Control Center (LCC) Firing Room, with any readings outside the limits resulting in the Launch Director, the NASA Test Directors (NTDs) and Mission Management Team (MMT) making a decision based around Launch Commit Criteria – often resulting in a scrub for the day and the detanking of the ET.

Click here for the list of GUCP-related articles: http://www.nasaspaceflight.com/tag/gucp/

This was the scenario that impacted three missions in the post-RTF era.

GUCP History – STS-119 (All “L2-tagged” materials can be found in the L2 GUCP Section):

The first leak put an end to Discovery’s opening launch attempt on STS-119 back in March 2009, using ET-127. The leak was observed at the point of the actual transition into topping, as the ET was almost full to its brim.

With readings alerted to the Booster console inside the LCC, the leak rate appeared to decrease when the vent valve was closed. This led to an initial effort to troubleshoot via the procedure of cycling the valve to clear any potential ice in the hardware, but this effort failed to stop the leak.

“STS-119 / ET-127: Pre-launch: 1st loading resulted in scrub/LCC violation due to GH2 leakage at Ground Umbilical Carrier Assembly (>40,000 ppm). Leakage occurred during transition from fast fill to topping. Vent valve opened when 98 percent level sensor indicated wet. Detected by leak detectors (LD 23 & 25) located in ground umbilical shroud,” documentation noted at the time (L2). “Isolates leak to either ground side quick disconnect (QD) or interface with flight seal.”

Once engineers accessed the GUCP, no obvious cause of the leak was found. The decision was made to changeout the seal, along with a focus on the retorquing of the hardware.

Engineering notes at the time pointed to a potential problem with the “left and right pivot seat”, which wasn’t fully connecting to the ET’s pin receptacle sleeve at the bottom of the GUCP.

“There was some damage to the flight seal, but we’re not sure that’s the cause,” noted launch director Mike Leinbach in review of the STS-119 troubleshooting. “There was a bit of discoloration on the QD (Quick Disconnect), but that might have been to the hydrogen flowing where it shouldn’t have been.”

With a new seal and the “tightening” of the hardware completed, STS-119′s second tanking was conducted without issue and no leak detectors tripped.

As a result, managers could be forgiven for thinking the issue was a one-off, solved by the replacement of the flight seal and the re-alignment of the pivot seats.

Click here for STS-119 news articles: http://www.nasaspaceflight.com/tag/sts-119/

As is typical for NASA, an investigation was still conducted into the STS-119 scrub, which noted that out of the previous 31 loadings only one leak was observed (and only at 13,500 ppm). The investigation also noted the potential for issues with the flight seal being part of the root cause, along with the misalignment on the pivot seats – resulting in the hardware being “pulled” down and to the left.

“Most probable cause identified as momentary breach in flexible flight-seal to bellows probe due to ‘thermal shock’ of GH2/LH2 with vent valve in open position. Significant Disassembly Observations: Lower left pad was hard against skin,” noted the findings (L2).

“Other locations were not touching (0.014 – 0.030 gap / 0.001 requirement) indicating a pull downward and to the left. Peripheral seal compressed more on left side and toward bottom of GUCP. Left side pivot assembly in hard contact with pivot pin (pin would not rotate). Stain observed on external surface of bellows guard and peripheral seal at 6 o’clock position. Flight-side seal asymmetrically compressed at 3, 7 and 8 o’clock positions.”

Changes were then implemented to ensure the alignment issue wouldn’t reoccur, with additional focus placed on both the installation of the GUCP hardware and observations of any movement once the stack was out at the pad. STS-119 launched without any further issues.

With the next mission, STS-125, avoiding any leaks during tanking, STS-119′s GUCP-related scrub continued to appear as a one-off issue, with additional confidence in future tankings gained by the aforementioned mitigation procedures. However, STS-127 would see the problem return.

GUCP History – STS-127:

Interestingly, STS-127′s GUCP issues began before Endeavour had even rolled out to the pad with ET-131, with documentation showing work to install the hardware on the tank – carried out inside the Vehicle Assembly Building (VAB) – had been problematic, ultimately requiring a changeout of the GUCP and a redesign to its installation hardware.

“Interference between GUCA (Ground Umbilical Carrier Assembly) and ET-131 right hand hinge support observed during mate GUCP (Ground Umbilical Carrier Plate) installation in VAB,” noted STS-127 SSP (Space Shuttle Program) FRR (Flight Readiness Review) documentation (L2).

Such an interference is not permitted at the hinge location due to the fact that there is potential to induce un-intended loading on the pyro-bolt assembly – which could affect that separation mechanism at T-0. In order to correct the interference, the GUCP was removed and a different unit was installed. However, after this was accomplished, the interference remained.

Visual and Laser inspections revealed the slight misalignment between the centerline of the plate and the hinge bracket, leading to a modification to the pivot assembly, which was successfully installed by “locally machining outboard surface (0.1” removed) to create the required gap (0.03” gap provided),” according to the FRR documentation.

How much relation those changes had to the subsequent leak during STS-127′s tanking remained unknown.

The first tanking of STS-127 registered a leak at the same time as STS-119′s detection, leading to the scrub and call to dismantle the GUCP hardware once the tank was inert.

Once the vent arm was removed and engineers removed the flight seal, observations pointed to a potential root cause via small gaps on the right hand side of the seal.

It was also thought the tank’s GUCP may have suffered from being mated and then unmated at Pad 39B, before being mated once more at Pad 39A, as Endeavour switched rolls from being STS-125′s Launch On Need (LON) vehicle (STS-400) to her primary role with STS-127 – requiring the pad switch.

This was a potential candidate for being part of the root cause because the seal is a hard teflon ring with no resiliency, and thus presents a sharp corner edged to a smooth tapered metal probe. Any bump, dent or mis-alignment of the probe during installation could result in a leak caused by damage to the teflon edge on the seal.

“GH2 vent seal inspection results: rolled edge around entire circumference with worst case from 4 to 10 o’clock position,” noted one log report on the status of the old seal at the time of troubleshooting (L2). “No inclusions and no scratches observed.”

Click here for STS-127 news articles: http://www.nasaspaceflight.com/tag/sts-127/

With the seal replaced, it was hoped that STS-127 would enjoy a smooth tanking at the second attempt, similar to STS-119 once the GUCP seal was changed-out. Unfortunately, the June 16, 2009 tanking once again registering a leak.

The leak was observed 25 minutes prior to topping and appeared to increase at the end of fast fill operations, with the leak detectors observing the peak leak rate of 60,000 ppm.

“This time the leak started during fast fill which is a signature we’ve never seen before (relating to the difference between the previous leaks, observed as the tank loading process moved from fast fill to topping/stable replenish of the LH2). During fast fill we leaked to approx. 15,000 ppm,” noted the STS-127 attempt 2 scrub outline on L2.

“Once we reached replenish, we violated the LCC like we’ve typically seen in the past. Leak eventually trended upward to 60,000 ppm.”

Initial theories pointed to several candidates as the root cause, such as unique thermal conditions associated with the hardware, notably the dynamics of the cryo temperatures that may be interacting with the hardware’s hinge brackets, resulting in a misalignment during tanking.

Also under evaluation were potential software issues, and even possible issues with the leak detectors that registered the leak during tanking – as much as the latter was ruled out as a specific reason for the scrub, due to the “visible” observation of venting from the tank.

Another investigation path pointed to the External Tank hardware itself, as opposed to the Ground Support Equipment (GSE) of the GUCP QD, as the reason for the specific leak issues observed with STS-119 and STS-127′s tanks.

However, the key area of interest is related to the two mounts, or feet, located on the tank where the GUCP hinge points attach. One of these mounts (right) was deemed to be offset from its preferred location.

“Have many folks across Agency supporting GUCP investigation. Appears to be going well. Appreciate folks at KSC showing us the hardware there. It looks like the ETCA plate that mounts (manually installed) to the ET is not properly aligned with the ET,” noted an Engineering overview presented via a Shuttle Standup meeting (L2) at the time.

“There are a couple of feet, below where the GUCP rotates off during separation, which are not mounted exactly correctly relative to the ETCA. When the GUCP is put on, there are forces between the pyro bolt, the large QD and the seat. If the alignment is not correct on the ET, the seat may be shifted as everything is tightened.”

This problem was also found on six other tanks set to fly, although the misalignment on ET-131 was classed as “the worst”.

“Two adjustments were made to get additional clearance to allow centering and alignment, but after both attempts, the feet and brackets were found way over to the right side and we were not able to align properly,” added notes, again pointing to a problem being suffered at the actual time the tank transitioned into a cryogenic state.

With the second scrub resulting in a several week standdown, NASA’s engineering teams were put into full investigation mode, resulting in a hugely impressive mitigation drive involving several centers.

Test articles were put to use – such as the GUCP rig at the Marshall Space Flight Center (MSFC) – working on the main candidate that a misalignment was causing the leaks, along with a drive to use a new two part flight seal, one which would be more forgiving to small misalignments, and hopefully mitigate unacceptable leak levels.

The two part seal also allows the tank to “burp” – without the need for vent valve cycling – which had previously cleared a minor leak on a previous loading earlier in the program.

The two part seal had only been installed in two previous tanks ahead of the problems with STS-119 and STS-127, one of which leaked, but was successfully mitigated via the “burp”, allowing the launch to proceed.

A tanking test in June 2009 was called for, testing out the changes and allowing for additional data to be gained – via strain gauges on the feet of the GUCP hardware – during the loading of the cryogenic propellants, with the ultimate aim of conducting a successful test and allowance to proceed with STS-127′s launch.

“The engineering teams, after much analysis of the measurement data between the 2nd scrub disassembly and the 1st scrub disassembly, have high confidence that misalignment is the issue,” noted documentation ahead of the tanking test (L2).

In order to mitigate misalignments, a redesign to the “fitted feet” on the GUCP was implemented on to STS-127′s tank. This design – along with the two part seal – was implemented into all future tanks that were under construction at the Michoud Assembly Facility (MAF).

The tanking test proved to be a success with no leaks detected, allowing for Endeavour to proceed towards another launch attempt, which also suffered from no leaks during tanking. Ironically, Endeavour was delayed by weather constraints and took a total of six attempts to finally launch on her mission to the International Space Station (ISS). No further leaks were observed on her tankings after the tanking test success.

The successes provided additional confidence that the engineering work on correcting and mitigating what was then confirmed to be an alignment issue of just 0.357 degrees in the counter-clockwise direction, has been successful.

The amount of work that went into fixing the issue was listed in a 47 page presentation to the all-powerful Program Requirements Control Board (PRCB), dated July 7, 2009 and acquired by L2 at the time.

The presentation provided what was claimed at the time to be the closure of the GUCP leak IPRs ahead of STS-127′s successful launch, a path that appeared to be confirmation the problem was behind them.

“Present the GUCP GH2 leak fault tree status, IPR closure (STS-119 and STS-127), and results of root cause assessment including affected materials, process/procedure/technique changes, and other associated relevant data. Present results to the PRCB,” prefaced the presentation.

“Identified 21 scenarios using inputs from community, new fault tree, timelines. Collected evidence to support/refute each scenario. 11 scenarios are fully (4) or partially (7) mitigated by the actions taken. Evidence reviewed by team ruled out 10 scenarios.”

Following an extensive review, engineers confirmed the misalignment was to blame. However, the a flight seal issue – since replaced with the “more forgiving” two-part seal – may have also contributed.

“Root cause: plate misalignment resulted in gapping at flight seal/bellows probe interface. Contributors: As-built flight hardware misalignment ETCA & hinge pin brackets. Insufficient controls during assembly to account for off-nominal ET geometry,” the presentation noted.

“Measurements, Alignment pins, Flight/ground plate relative motion (lateral) during assembly. Reduced capability to accommodate motion at interface during operations due to stiffer Inconel bellows. Unexplained Anomaly, possible contributors include: Flight seal defects and/or damage during assembly. Potential plate misalignment.

“Leak mitigation: Tighter tolerance alignment pins (0.515”). Tailored GUCP feet (0.180” & 0.230” offset). analysis shows adequate strength. Hinge pin washers restrain GUCP lateral motion. 2-piece flight seal has greater resiliency and provides additional capability for misalignment. 2-piece seal tested to 0.050”. Concentricity and other measurements during assembly show minimal motion of GUCP. Successful tanking test. Tanking test observations show minimal motion of GUCP feet.”

However, the PRCB investigation into the STS-119 and STS-127 leaks admit that “A lack of root cause for STS-119 and partially mitigated failures scenarios demonstrate some residual leak risk still exists,” but “recommended MMT action closure”.

GUCP History – STS-133:

STS-133′s ET-137 proved to be a rather troublesome tank, following a double issue during its loading on launch day.

Discovery saw her final mission delayed, following the recording of IPR-68 (Interim Problem Report) during the countdown, when leak detectors at the pad observed the gaseous hydrogen leak from the GUCP.

All had been proceeding to plan – with the tank “fast filled” during tanking, with no issues recorded with either the loading process, or the Low Level/Engine Cut Off (ECO) sensors via their customary SIM checks – until the first leak indication was revealed.

Firstly, a 33,000 ppm leak – below the 40-44,000 ppm (HAZ-09 limit in the Launch Commit Criteria – LCC) – was recorded, before reducing to a level below 20,000 ppm. The leak was only being observed during the cycling of the vent valve to “open” – to release the gaseous hydrogen from the tank and through the vent arm plumbing to the flare stack, as designed.

With controllers deciding to stop the cycling of the valve – in order to increase the pressure and attempt to force a seal – before attempting to complete the fast fill process and transition into “topping”, the leak spiked and pegged at the highest 60,000 ppm level, indicating a serious problem with the GUCP’s seal.

With cycling of the valve resumed – as part of the troubleshooting efforts to clear any potential obstructions such as ice from the hardware – and no resolution forthcoming, a scrub was the only outcome.

Click here for STS-133 news articles: http://www.nasaspaceflight.com/tag/sts-133/

“Pegged leak detectors at topping. Violation. Scrubbed for today. Configuring for drain,” flashed the confirmation (L2), as controllers moved into emptying the External Tank, leading to the ECO sensors registering “dry” at 13:53 local time.

However, after the scrub was called, cameras at the pad picked up another serious problem, with cracks observed on the foam surrounding ET-137′s LO2/Intertank flange stringers.

It took around a day for the tank to become inert, allowing engineers to prepare towards disconnecting the vent arm and the large amount of lines and ordnance on the hardware, prior to taking their first look at the potentially suspect seal and any potential alignment issues – the two leading candidates for the leak.

At the same time, meetings were conducted to assess the reason for the crack, later found to be caused by the stringers themselves becoming cracked underneath the foam.

Ultimately, a huge amount of work was carried out, both to investigate the root cause of the cracks – found to be via a “mottled” batch of stringers at MAF, leading to a rollback and the installation of radius blocks to strengthen the local structure.

While this work was completed, engineers were called to “clock” the GUCP’s placement on the tank – and a new two-part flight seal installed. The team were provided with “free” test of the GUCP via a Tanking Test, called for to aid the investigation into the stringer cracks. The test showed the GUCP did not leak at any point during the tanking, adding confidence to the mitigation procedure.

With STS-133 launching successfully, the last two missions of the Space Shuttle Program did not suffer from any issues, either with the ET’s stringers or GUCP.

GUCP – SLS:

NASA managers often speak of “lesson’s learned” – the ability to draw on their vast experience in the rocket business, aided by their database of mitigation procedures. A shining example of this process was highlighted in a presentation that reviewed the aforementioned incidents with the GUCP and its relation to SLS.

Relating to how SLS will have commonality with ET hardware – given the SLS core is Shuttle-like ET, bar obvious changes due to the in-line design of the HLV – the experiences of the Shuttle Program are notably apt.

However, there will be differences between the Shuttle and SLS hardware, specific to what was the GUCP on the ET. Firstly, the ongoing design process has moved further away from a direct match with the Shuttle ET GUCP, instead opting for a Core Stage Inter-Tank Umbilical (CSITU).

According to the Ground Systems Development and Operations presentation (available on L2), “Final cost and schedule impacts to … baseline for change from ET Vent Line reuse to new swing arm umbilical” are pending final approval.

The new design will provide commodity services to the SLS’s Core Stage Inter-tank region. The umbilical arm will be 45 feet in length, 8 feet in width, and 15 feet in height.

An added benefit will come via the umbilical and ground carrier plates being mated in the VAB – due to no pad access for umbilical mating – allowing them to remain connected to the vehicle until liftoff. This will help avoid any problems that can occur with mating the hardware at the pad.

For previous SLS Articles, click here: http://www.nasaspaceflight.com/tag/hlv/

The umbilical plate size is now expected to be 34 inches x 54 inches, although it will still consist of a seal at its heart as the protective element against scrub-causing leaks.

This is where a team effort – between NASA Engineering (NE) and Team QNA Engineering personnel – is working towards a goal of providing support for the Umbilical Systems Development project, which is funded by Advanced Exploration Systems (AES) and 21st Century Launch Complex.

Reviewing the Shuttle issues with the GUCP, and consulting with the SLS team for their recommendations, an associated presentation noted that several “lesson’s learned” will be implemented for the HLV.

These recommendations included the development of a concentricity tool, to help alignment during assembly of flight side components. The use of Parallelism Retainer Clips, Ground Support Equipment bolts and clips that will maintain parallelism at the seal face during assembly of QD to launch vehicle. And the use of a Self-Aligning Probe, to accurately guide and centre the QD and the tank vent as they are brought together during the integration flow.

They also reviewed the old two piece seal designs, proposing three new alternative seal designs – to be down-selected after more detailed tests/analysis.

The end result of these early evaluations will hopefully avoid launch fans having to head back home after a launch day scrub caused by the detection of unacceptable levels of leaking gaseous hydrogen from a small vent on the side of the vehicle.

(Images: Via L2 content from L2′s GUCP section and L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other image via NASA)

(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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The Last Of The External Tanks:

While ET-94 will never have the opportunity to launch as part of the shuttle stack for the eight and a half minute ride uphill, its role in the Space Shuttle Program (SSP) was hugely important.

As a Light Weight Tank (LWT), its role in the upmass-hungry latter stages of the program was always highly unlikely, with Super Light Weight Tanks (SLWTs) – weighing 58,500 pounds, a 7,500-pound weight saving from the LWT version – aiding missions tasked with carry modules into orbit, for the assembly of the International Space Station (ISS).

However, due to it being the sister production tank of ET-93 – the tank that shed the chunk of Thermal Protection System foam from its bipod ramp, ultimately causing the Columbia disaster – it provided vital data into both the understanding of surprisingly complex phenomenon of foam loss and the highly successful modifications that led to vastly improved safety for the final run of shuttle missions.

While ET-94 sat around the New Orleans facility, watching brand new tanks take shape, prior to riding on the Pegasus Barge to the Kennedy Space Center, the numerous efforts to extend the Space Shuttle Program past STS-135 did – albeit slightly – raise the tank’s hopes of flying.

The discussions evaluated the timescale involved with providing ETs for STS-136 and beyond, with a tradeoff between opening with ET-94, or “simply” restarting construction of the tanks at MAF.

It was deemed that ET-94 would require a huge amount of modifications to bring it up to the post-RTF (Return To Flight) level of requirements, while the mission would also lose a large amount of payload capability when compared to a mission with a SLWT.

With parts of three new SLWTs already on site at MAF – namely ET-139, ET-140 and ET-141 – the extension studies decided on utilizing those tanks, prior to the final drive to save the Shuttle program ending last year.

All options relating to the production of additional ETs suffered heavily from the shutdown of suppliers and the loss of skilled workers over the latter years of the program, resulting in estimates that it would take a full two years, from the point of an extension being approved, before a new tank would be available at KSC for a mission.

For other ET articles, click here: http://www.nasaspaceflight.com/tag/et/

While ET-139 provided a test bed for work surrounding the Stringer crack issue suffered by STS-133′s ET-137 near to the end of the program, the part-built spare tanks at MAF have since been sent for scrap.

Pictures of ET-139′s parts, acquired by L2 (LINK) – show the tank had almost all of the required hardware on site, as much as it was yet to be welded together.

With those tank parts now scrapped, the giant facility is left with just a few pieces of tank hardware – mainly being used to refine measurements on new tooling – and ET-94, a tank that is yet to find out its fate.

However, on September 15, the Manufacturing Support and Facility Operations Contract team at the facility performed what was classed as the final critical lift of the Space Shuttle’s External Tank Program, as ET-94 was moved from its storage cell at the VAB to Building 103, translating it from its the vertical position, and prior to gently placing it horizontally into its wheeled carrier.

Michoud’s VAB stands 210 feet high and has served both the Apollo and Shuttle Programs. The removal of ET-94 allows for construction crews to begin modifying the VAB to install new tools for manufacture of the core stage booster of the Space Launch System (SLS). This work will begin immediately.

“It’s a historic moment and the lift team performed flawlessly,” said Robert Champion, NASA deputy director of Michoud. “This is the last external tank to leave our VAB, and while it marks the final critical lift of external tanks at the facility, it clears the way for the facility modifications needed to build the Space Launch System rocket.”

There is some hope ET-94 won’t suffer the fate of ET-139-141, with MAF noting the tank is being kept in a climate-controlled environment and “monitored to preserve it for future testing or display.”

Technically, the tank could find a role with the SLS program, previously associated with the Sidemount SD HLV option, but now potentially as part of a Main Propulsion Test Article (MPTA) during ground testing in the coming years. However, no decision has been taken on an official level.

Sources note (See L2 Link) the tank is in somewhat of a sorry state, after its umbilicals and feedlines were removed, along with large amounts of foam missing due to dissection activities.

A lot of the tank’s cable trays have been removed, and it is not clear if ET-94′s LO2 and LH2 tanks were kept pressurized during recent years, when storage requirements during the Shuttle program required both tanks to be pressurized to 6.0 PSIG, with nitrogen to keep the tanks dry internally. This may impact its ability to become a test article.

The tank now belongs to Jacobs Technology, who hold the Manufacturing Support and Facility Operations Contract at MAF, under the management of the Marshall Space Flight Center (MSFC).

Images: Via L2 content and MAF.)

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SLS SDR/SRR Step 1:

Development of the Heavy Lift Launch Vehicle (HLV) appears to be proceeding smoothly, with all schedule milestones – towards its debut in 2017 debut as part of the Exploration Mission -1 (EM-1) test flight – hitting their marks.

While that should be expected, problems within the now-defunct Constellation Program (CxP) were being noted almost from the opening day of its development cycle – not least with the Ares I launch vehicle.

The latest milestone to be passed was the opening phase of the combined System Requirements Review (SRR) and System Definition Review (SDR) – a milestone to allow engineers to further nail down the scope of the system design and evaluate the vehicle concept based on top-level program requirements.

“The reviews include setting launch vehicle requirements for crew safety and interfacing with the Orion Multi-Purpose Crew Vehicle to carry it to deep space as well as the ground operations and launch facilities at NASA’s Kennedy Space Center,” noted NASA. “Additionally, the reviews set cost and schedule requirements to provide on-time development.”

As noted by SLS teams, this stage of development confirms the OML (Outer Mold Line) of the vehicle – at least the Block 1 70mt version – meaning the “shape” of the SLS is now set to that depicted in the latest documentation.

“It’s exciting to see how far this program has come in such a short time,” said Todd May, SLS program manager at NASA’s Marshall Space Flight Center (MSFC) in Huntsville, Alabama. “Completion of this first step of reviews moves the nation’s first deep space rocket from concept development to preliminary design.”

The milestone reviews are two in a series of life-cycle reviews advancing the vehicle from concept design to flight readiness. Step one included a focused technical review of the program requirements with information on cost, schedule and risk. Step two, which will begin in early summer, will include an integrated assessment of the technical and programmatic components fully evaluating cost, schedule and risk involved with the program.

“This checkpoint gives us a mature understanding of the requirements, solidifies the vehicle concept design will meet all the requirements of the program and mission and signals that SLS is ready to begin engineering design activities,” added May. “We’re moving forward to deliver a new national capability to get America exploring space again.”

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SLS Won’t Be Fazed By Scrubs:

While SLS will be able to rollout and launch within seven days, according to its Concept Of Operations (Con Ops) Document (Available on L2 – Link), problems for any vehicle during the launch pad flow can be expected.

Having a set of parameters for what the vehicle can cope with during a troublesome pad flow – not least during the countdown – is important for the controllers and managers in the Launch Control Center (LCC) that will eventually launch the monster rocket.

As such, SLS engineers have already provided a preliminary outline of SLS’ capabilities in the latest rev of the Space Launch System Program Launch Vehicle Specification document (Available on L2 – Link).

In the order listed by the Specification document, SLS will have a capability of four hours hold time. How useful such an amount of time will be will depend on the mission, with specific targets – such as the International Space Station (ISS) – resulting in the Space Shuttle only having a short window of minutes – as opposed to hours – prior to having to scrub for the day.

“Launch Countdown Hold: The SLS vehicle shall be capable of remaining in a countdown hold, in a stable, replenish mode, for at least 4 hours,” noted the document. “Rationale: Examples of drivers for this requirement include weather holds, range safety holds, etc.

“The launch vehicle will need to be capable of accepting the launch commands from ground control at any point within the window defined. This will include cryo boil-off and re-supply as needed. The expectation is that the launch countdown is in a condition where stable replenish is available throughout the launch window with stable replenish cut-off prior to tank pre-pressurization. This includes provision of any required purges, thermal support, etc.”

The SLS is a Shuttle Derived (SD) launch vehicle, and will sport a core stage developed from the technology of the Space Shuttle’s External Tank (ET). It is likely to be the commonality between the two “fuel tanks” that helped provide the rational for the Specifications document to cite the HLV will be capable of at least 13 cryo cycles.

The large amount of cycles is important, not least when referring to some of the Space Shuttle’s recent history with weather and technical related scrubs.

Recent non-weather related issues that have required several cryo cycles included the problems with the Engine Cut Off (ECO) sensors ahead of STS-122′s launch. However, it was the double whammy of the problem relating to the Ground Umbilical Carrier Plate (GUCP) leak and Stringer crack on Discovery’s ET-137 ahead of STS-133 that proved to be the last big challenge for the Space Shuttle Program (SSP).

The problem arose on the morning of the November 5, 2010, when ET loading operations picked up on time and continued nominally, until the hydrogen vent valve in the ET was opened to allow boiled-off gaseous hydrogen to vent from the tank. At this time, a leak indication was detected at the GUCP.

Initially, the launch team responded by cycling the vent valve in an attempt to reseat the GUCP/ET Carrier Assembly seal. However, the leak soon breached the 44,000ppm Launch Commit Criteria limit – spiking to at least 60,000ppm: the maximum reading on the sensors at the pad.

While this incident caused the immediate scrub of STS-133′s launch attempt, a much more serious issue would present itself. During de-tanking operations, a stringer on the ET intertank structure snapped under cryogenic stress loads, thereby cracking and deforming the TPS foam on the external tank in the immediate area.

With the leak of the GUCP and the crack to the ET foam, mission managers determined that Discovery would not be able to launch for what turned out to be several months.

With the failed stringers replaced and a fix to the GUCP leak found, NASA managers elected to perform an instrumented Tanking Test on Discovery’s ET-137 in mid-December of that year. The test served two purposes: validate and verify GUCP leak resolution and monitor and determine stringer stress at the ET LOX/intertank flange area under both cryo and pressurized environments.

With the tanking test complete, NASA managers pressed forward with plans to roll Discovery back to the VAB for a complete inspection of all stringers on ET-137′s intertank region.

Discovery was rolled back on December 22/23 to the VAB where a complete inspection revealed three cracked stringers on the “backside” of the tank.

In January 2011, NASA engineers succeeded in determining root cause for the stringer crack issue – a bad batch of “mottled” stringer material. This information led to the decision to implement Radius block doubler installations on a vast majority of the stringers at the ET LOX/intertank flange.

Completion of these modifications allowed NASA managers to set a NET launch date of February 24th for STS-133, which resulted in Discovery launching without issue.

While the issues with ET-137 – and two other earlier tanks from the GUCP leak standpoint – are now understood and “closed”, the results will feed into SLS – which will also sport a GUCP on its core stage – another advantage of a Shuttle Derived system.

However, should the SLS suffer from its own problems – weather related or technical – it will have the ability to be put through at least 13 cryo cycles, a healthy margin considering the Shuttle’s scrub history once the ET has completed tanking operations and is under cryogenic conditions.

“Rationale: For the purposes of this requirement, a cryo plus pressure cycle is post-tanking of propellants and tank pressurization which puts the system in a launch-ready state,” added the Specifications document.

“This requirement ensures that the fully operational launch vehicle will be able to support a minimum number of launch attempts without fatigue life issues. Useful life is defined as the item’s total life span including servicing life and shelf life with normal preventive maintenance, servicing, repair, and replacement of parts before item is considered unacceptable for further usage.”

The SLS will also be able to weather the ever-changeable conditions out on its seaside launch pad (39B) for at least half a year, a scenario also likely related to allowing engineers time to troubleshoot the stack without requiring rollback to the Vehicle Assembly Building (VAB).

“The SLS vehicle shall withstand the natural environments at the launch pad for a minimum of 180 days from first exposure, excluding wind loading effects, which are covered by the vehicle coupled loads,” the document added.

“Rationale: The design of, and materials chosen for, the vehicle shall consider the effects of exposure to the natural environments such that material properties used in analysis of the hardware can reflect the actual hardware condition after the minimum exposure time, i.e., either degraded material properties should be defined and used in analyses or materials should be chosen such that properties can be shown to not degrade during that time.”

The document also noted that the vehicle – once stacked – can remain in its launch configuration for no less than 200 days. This specification aids the launch flow, especially during the multi-launch campaigns for deep space missions, allowing – for example – one SLS to be out at the pad, while another SLS is stacked and waits patiently inside the VAB.

“The SLS vehicle shall be capable of remaining in a stacked configuration for a minimum of 200 calendar days without the need for vehicle destacking,” the presentation stated.

“Rationale: Requirement is to provide operability for scenarios where remaining stacked allows flexibility in meeting downstream launch schedules. This also provides flexibility and avoids operations re-work within the vehicle integration facility to resume the launch flow in an expedited manner. Vehicle stack time does not include integrated element time.”

As noted in SLS documentation, the current spacing between SLS launches is 121 days. The low launch rate is understood to be budgetary related, although this has not been officially stated.

However, it has been claimed that SLS’ top of the range mass-to-orbit capability makes up for a large amount of this disadvantage, when compared to the fleet of medium lift launch vehicles it would require to achieve the same upmass ability, prior to taking the payload dimensions into account.

(Images: Via L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV, available on no other site. Other images via NASA.)

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MAF:

Working under the motto of “Finish Strong”, the Michoud managers, engineers and technicians proved to be the unsung heroes of the final phase of the Space Shuttle Program (SSP).

Fighting back from the tragedy of Columbia’s loss, caused by a piece of hardware from one of their own External Tanks – as much as a series of events outside of their control contributed to the disaster – the MAF team and center became one of the focal points for the implementation of Return To Flight (RTF) modifications – L2 link.

Initially, this proved to be anything but smooth sailing, with the first tank to fly since Columbia’s launch liberating a large slice of its PAL (Protuberance Air Load) ramp during Discovery’s STS-114 ascent – resulting in further changes via the complex science of mitigating foam loss during the ride uphill.

Further finite modifications were made to the tank’s Thermal Protection System (TPS) as the fleet began to up the pace, itself a massive challenge, with each change to a highly refined system carefully studied and refined further.

One such example was the modifications made to the LH2 Ice Frost Ramps (IFRs), which were fine-tuned over a number of flights, based on their performance during actual launches. The LO2 IFRs were also monitored through to the end of the program.

These numerous changes, in tandem with an improving flight rate, resulted in additional challenges, such as achieving the delivery dates for the tanks based on the projected flight manifests created by the Flight Assignment Working Group (FAWG) – L2 Link.

Via the mix of ingenious management brainstorming at numerous Technical Interchange Meetings (TIMs), the dedication of the Michoud workforce working seven days a week and solid leadership from Lockheed Martin’s ET boss Wanda Sigur, refined delivery dates supported the desired manifest – as seen ahead of the flagship STS-125 mission to service the Hubble Space Telescope.

Click here for numerous ET news articles: http://www.nasaspaceflight.com/tag/et/

More importantly – not least in the case of Atlantis’ Hubble mission – the tanks started to enjoy a run of increasing success in the mitigation of foam liberation from the critical areas of the tank, resulting in mainly “clean” orbiters – no serious TPS damage caused by foam loss) – especially in the latter missions for the fleet.

Michoud even managed to add a tank to the manifest, namely ET-122, allowing for the addition of STS-135, a mission which has proved to be extremely vital for the International Space Station’s logistical health, especially during what has proven to be a problematic year for the Russians.

ET-122, damaged by Hurricane Katrina in 2005 when it was located in Cell-A of MAF’s Vehicle Assembly Building (VAB), required a large amount of work, both from a repair standpoint, but also via the requirement to implement the numerous RTF modifications.

And Katrina didn’t just damage the tank, but also displaced large amounts of the MAF workforce, some of whom were technically homeless at the time NASA needed them the most during the comeback from negative delivery dates.

Sadly, most of that workforce fell foul of NASA’s ongoing transition, as much as most saw it coming since the decision was made to retire the Shuttle fleet once ISS assembly was complete - although the since-cancelled Constellation Program (CxP) was a hammer blow to the facility. Just a handful of ET engineers remained at MAF by the end of August, with the rest of what is now a small workforce working on Orion and other contracts.

The official end of ET work at MAF resulted in the spare tanks – such as ET-94 – no longer being serviced by Lockheed Martin. They have been turned over to the ownership of Jacobs Technologies.

A number of workers might of been saved, had NASA administrator Charlie Bolden announced the Space Launch System (SLS) when lawmakers had requested it. MAF leaders had hoped for an end to the delays earlier this year, extending the period prior to the handing of WARN notices to a number of workers several times, before finally losing patience.

Now the SLS program is up and running, MAF are hoping to be involved in the resulting contracts, with one of the main contractors likely to be building the core stage, Boeing, already noted to have utilized the facility for their SLS-related Pathfinder tank. Meanwhile, other major weld tooling has been placed into storage.

MAF At The Movies:

Ironically, some of the remaining workforce found themselves with job sheets that had nothing to do with the space program, as they spent some of their days removing equipment to make space for a string of production companies to use the facility to film parts of their blockbuster films, per L2 information.

The first of which was GI Joe 2 (Retaliation) – which has now completed filming inside MAF, ahead of its summer 2012 release date.

This movie stars Bruce Willis – who is no stranger to space hardware, following his staring role in the blockbuster movie Armageddon, which filmed at numerous NASA centers, including the Johnson Space Center (JSC) and the Kennedy Space Center (KSC).

Universal Pictures will arrive in January to film two movies (the titles of which are being kept secret), while Disney and MGM are also in the process of negotiating the use of MAF’s 101 building for filming purposes.

Despite the major handover to Jacobs, Lockheed Martin still had control of final assembly position 3. However, current MAF employees have been told to clear out all equipment to make room for yet another studio. At this time all four final assembly positions, the entire VAB, and the 420 building at Michoud are now classed as movie sets.

It has also been noted that the BP oil company has also taken control of BLDG 451 – otherwise known as the LH2 proof test building – to store the blow out preventer that caused the Gulf oil spill in 2010.

It is hoped that sometime in 2012, MAF will see the work being carried out on the Orion which will fly on the Exploration Flight Test (EFT-1) being joined by work on commercial vehicles and the SLS, as opposed to providing a large indoor facility to Hollywood.

Please note: Clickable links with (L2) references point directly to cited L2 content. Such content is only available to L2 members (please ensure you are logged in). All other clickable links point to NSF articles and open content.

Images: Via L2 content. Other images via NASA.)

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SLS Work:

August has been a relatively busy month for SLS, with NASA centers and contractors almost ignoring the delaying tactics in Washington DC, by pushing on with planning work surrounding the winning configuration of the Heavy Lift Launch Vehicle (HLV) – as much as NASA’s top brass continue to avoid announcing it.

At the Marshall Space Flight Center (MSFC), the new SLS DAC (Design Analysis Cycle) cycle officially started this month, a process which will take the vehicle design to the SRR (System Requirements Review)/Checkpoint Review in October.

Managers have already presented their teams with kickoff charts, showing what is now the well-known Shuttle Derived (SD) HLV, along with pointers towards a forward plan to develop the Upper Stage design simultaneously with the core stage.

While no Upper Stage hardware will be built at this stage, given the lack of funding, the current process of developing the US with the Core will provide an engineering advantage, given the integrated vehicle loads can be developed in a way which will allow the Core Stage to be designed for the appropriate Upper Stage from the outset.

With SLS concept development providing support of the SRR/SDR (System Design Review) and core stage procurement activities, the path is laid out for the SLS to progress to the PDR (Preliminary Design Review) stage. Once the core stage prime contract is awarded, the work will transition to more of an insight and vehicle integration role.

Boeing – who officially class themselves as “pursuing work on NASA’s Space Launch System to provide heavy lift capability for exploration beyond Low Earth Orbit” – have already completed testing their manufacturing processes via a sub-scale tank, known as the “Pathfinder”.

For SLS/HLV Articles, click here: http://www.nasaspaceflight.com/tag/hlv/

The Boeing team at MAF in New Orleans, class the Pathfinder as a “major milestone toward the future of space exploration”, adding the tank is a “key demonstration of NASA’s readiness to immediately transition into the Space Launch Systems (SLS) program”.

The Pathfinder Liquid Oxygen tank is a 5.5 meter diameter lightweight aluminum lithium design, demonstrating state of the art manufacturing and welding approaches developed as part of the Upper Stage Production Contract (USPC), allowing engineers to work on a 5.5m tank – per development on Ares I’s Upper Stage – via technologies and techniques will be applied to the 8.4m diameter SLS.

“State of the art production tools, developed by Boeing in partnership with NASA and the University of New Orleans National Center for Advanced Manufacturing, provided efficiencies not previously available at MAF for this type of manufacturing. The pathfinder is also representative of a Liquid Oxygen tank that is extensible to the Space Launch System,” noted a Boeing overview (available on L2).

“The use of a Liquid Oxygen tank originally designed for Upper Stage Production Contract enables an efficient transition of subsystems such as the Main Propulsion System and Thrust Vector Control from USPC to Space Launch Systems.

“Work on the Space Launch Systems enables Boeing to expand into a natural adjacency, leveraging decades of experience in manned space flight into possible future business.”

Interestingly, further evaluations have recently begun into the MPS which will ride with SLS, with the potential for the three retired Shuttle orbiters to donate their MPS’ for the opening three flights. (Another article will follow on this evaluation next week).

The lightweight aluminum-lithium design features a spun-formed dome, a gore panel dome, and a barrel welded together with two circumferential self-reacting welds. The team managed to complete the fabrication six weeks ahead of schedule.

“Preparing the Pathfinder for production (was) a major step toward production of the nation’s next generation human-rated launch systems,” said Steve Ernst, Boeing’s Exploration Launch Systems Manufacturing Development leader on the Boeing information

“The completed work is a balance between safety, reliability and cost forged by an innovative NASA-Boeing partnership that is paving the way for SLS.”

The information also notes how Boeing worked with NASA’s MSFC in developing the manufacturing processes, in order to prepare the Boeing engineers and technicians with the skills and techniques necessary to employ state of the art techniques for safe, reliable, and cost efficient production of future launch vehicles.

“(This was a) significant advancement of MAF activation by completing key training and certifications for task leaders and weld operators; establishing detailed approaches and processes for kitting, staging, and shipping and receiving; and emphasizing a significant focus on a healthy safety culture and process with the completion of job hazard analyses and lift plans.”

Boeing also confirmed that in order “to support Congressional direction to NASA for development of the Space Launch Systems”, Boeing prioritized work in its existing USPC and Instrument Unit Avionics contracts to work on items that advanced the technical baseline of technologies and manufacturing approaches for the new Heavy Lift Launch system.

“We recognized that we needed to identify opportunities to earn value for NASA and reduce risks associated with the transition to SLS,” added Rick Navarro, Boeing Michoud Site director.

“Working with NASA, this vision resulted in developing the concept to manufacture the Pathfinder tank which not only enabled the team to demonstrate technologies extensible to SLS, it also focused the team on establishing the necessary Boeing production infrastructure at Michoud to prepare for SLS production.

“As a result, the team at Michoud found a way to start up operations and begin a functional production system.”

Boeing teams at the Kennedy Space Center also assisted the MAF Boeing team in establishing the necessary stock of production supplies for the production of the Pathfinder, while the the team at Boeing’s Huntington Beach operations played a key role in development and fabrication of tooling that was used for the Pathfinder.

Other Boeing sites such as San Antonio, Heath, and Charleston also assisted in defining and obtaining the necessary infrastructure to monitor production activities. A number of suppliers, stretching from the northeast United States to the west coast, also supported the Pathfinder effort.

The Pathfinder milestone comes at a time of painful transition for MAF, with WARN notices – extended several times in the hope NASA would finally push forward with its SLS contract awards – finally activated, resulting in the official end to ET operations at the facility.

Just a handful of ET engineers will remain at MAF after Friday, with the rest of what is now a small workforce working on Orion and other contracts.

The official end of ET work at MAF has resulted in the spare tanks – such as ET-94 – no longer being serviced by Lockheed Martin. They have been turned over to the ownership of Jacobs Technologies.

It is unknown what Jacobs will do with the ET hardware. However, their MSFOC group has begun unwrapping ET “major weld” tooling, placed into storage after the final ET was constructed.

These tools are the 5018 and 5019 (LO2 Weld and LH2 Weld) machines – which have been in preservation for a couple of years – and are the major weld fixtures for the LO2 tank and LH2 tanks (horizontal). Currently, the 5019 LH2 fixture has been unwrapped, with the LO2 5018 machine set to follow.

Once the tools are back in place, Lockheed and Boeing engineer will take measurements of the tools to evaluate their conversion from arc plasma welding to stir friction welding.

This also appears to be preparation work for the construction of SLS tank hardware.

(Images: Via MSFC, Boeing, MAF and L2 content - driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV available no where else on the internet).

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ET camera ascent performance (STS-135) and history:

As was the case 21-times before, the ET engineering camera on the LOX feedline of the External Tank functioned perfectly through pre-launch and launch activities during Space Shuttle Atlantis’ historic and sentimental journey to Low Earth Orbit on July 8.

During the launch of STS-135, the ET camera provided NASA managers and DAT (Damage Assessment Team) personnel with an early look at the tank’s performance as well as any areas of Atlantis’ TPS (Thermal Protection System) that might have been dinged by small foam liberations from the tank.

In all, the quick-look assessment enabled by the ET camera led to the understanding that this was one of the most - if not THE most - clean External Tanks in the history of the Shuttle Program: an in-flight tribute to the hard work and dedication of thousands of NASA engineers and the honorable workforce at the production facility in New Orleans, Louisiana.

This quick-look assessment of Atlantis’ TPS was confirmed on FD-2 and FD-3 of the STS-135 mission when it was revealed that Atlantis had sustained only one lower-surface TPS ding from ET debris.

But while the camera (a Sony XC-999) and its systems worked perfectly on every single one of the 22 post-Columbia Shuttle missions, the camera actually debuted on STS-112, providing images up to SRB separation when debris covered the camera lens and prevented further clear image downlink.

STS-135 Specific Articles: http://www.nasaspaceflight.com/tag/sts-135/

Moreover, the camera’s primary use on STS-112 - a mission by Atlantis in October 2002 - was for PAO launch coverage purposes and not for engineering assessment of the Tank’s TPS performance - an ironic use considering the rather significant foam liberation event that occurred on STS-112 and subsequent foam liberation event on STS-107/Columbia that ultimately made the camera mandatory for tank engineering assessment purposes.

Debuting in what would be its nominal configuration on the STS-114 Return To Flight mission by Shuttle orbiter Discovery in July 2005, the ET engineering camera was the first step in a scaled build-up of the Enhanced Launch Vehicle Imaging System, which eventually included four total cameras on the SRBs, an orbiter ET Umbilical Well camera for post-ET/Orbiter separation imagery, and a “lipstick” camera on the orbiters’ forward-facing pilot’s windows to capture LO2 Ice Frost Ramp foam liberations during ascent.

Over the course of their use by the Shuttle Program, the 22 post-Columbia ET engineering cameras proved their worth time and time again.

Using a 3.5 mm lens to provide a near 100-degree field of view, the cameras captured both amazing ascent footage and carried out their primary task of observing and timing any TPS foam liberations from the tank and any resulting impacts on the orbiter by offering a look at the vicinity of the tank’s bipod attachment area, the portion of the External Tank where the liquid hydrogen tank and intertank flange areas are adjoined, and a portion of the bottom side of the Orbiter.

The cameras themselves, from STS-114 through STS-135, were mounted inside the ET’s liquid oxygen (LOX) feedline fairing - a metal covering that protects the area where the fuel feedline penetrates the inter-tank structure and begins its journey down the exterior, orbiter-facing side of the ET.

Moreover, a section of the 1500 page INCO systems handbook - available for download on L2 - states, “The ET LO2 feedline fairing camera is powered and controlled automatically from the electronics package mounted on a support beam located between the LO2 and LH2 (Liquid Hydrogen) tanks.

“The camera’s field of view includes the bipod assembly region, Orbiter left and right wing (except as obstructed by the bipod strut), Orbiter -Z TPS beginning 12 inches forward of the bipod fitting and continuing aft. The camera captures images at the National Television System Committee (NTSC) frame rate of 30 frames per second (fps) and can see debris/divots that are 2.0 x 2.0 inches or larger at a distance of under 20 feet.”

Furthermore, each camera’s battery pack included 20 nickel-metal hydride batteries, which provided approximately 28 volts DC to the camera.

The batteries themselves were designed to function for about 70 minutes to allow for three launch attempts prior to recharging/replacing of the batteries. Nonetheless, the camera systems were designed to automatically switch the system off 15 minutes after liftoff - regardless of battery life potential.

To enable transmission of live images from the camera, each camera was attached to two “blade” S-Band antennas with a frequency range between 1.55 to 3.9 gigahertz.

Each S-Band antenna was about 2.5 inches long, transmitted a 10 watt signal to ground stations, and was located on the opposite side of the ET from the Orbiter - +/- 47.5-degrees to the side of the ET’s centerline.

During ascent, video from each camera was downlinked from the ET to several different NASA data receiving sites before being relayed for broadcast on NASA TV.

The last of these receiving ground stations along the Shuttle stack’s flight path was Wallops Flight Facility on the eastern shore of Virginia.

STS-135 ET camera mods and pre-launch single acquisition assessments:

While it was never a certainty that the extended transmission of video from the ET-138′s LOX feedline camera would prove fruitful, the effort to attempt to gain never-before-seen images of the External Tank after its separation of an Orbiter was undertaken by Michoud Assembly Facility (MAF) engineers at the request of the Space Shuttle Program.

According to the Extended STS-135 ET LO2 Feedline Video Transmission/Acquisition presentation, available on L2, “PRCB request to assess feasibility of leaving LO2 feedline camera on and recording the downlink TV signal for as long as possible until ET entry and/or breakup.”

To accommodate this request, a “best effort” was made to A) carry out a modification on ET-138’s camera without installing new hardware and B) secure acquisition stations along the ET flight path to “receive and record analog FM TV signals.”

The actual modification to the ET camera was made with relative ease in late-June by the “clipping” of a single wire in the EP to “disable the timing circuit” used to deactivate the camera 15 minutes after liftoff.

However, from the very beginning, the PRCB request presentation made it clear that actually obtaining video from the camera after the tank passed downrange of Wallops was going to be extremely troublesome.

“Two parts to the problem: Coordinate with countries regarding transmitting in airspace and Identify and secure receiving stations along ET flight path.”

To this end, by June 16, agreements had only been reached with the Department of Defense and Germany, and work had just begun to re-active the Diego Garcia (REEF) ground station and assess the potential use of “Navy ship-based assets.”

Additional ground stations in Dongara and Perth, Australia were evaluated but ultimately dismissed since they lay too far north of the ET’s projected flight path.

Furthermore, “A potential lead was pursued for a US Army base in Kuwait (Camp Arifjan), but they [were] not configured to receive analog FM TV from orbit,” noted the Signal Acquisition presentation.

Aircraft usage via the HYTHIRM project from the Langley Research Center were presented, but no aircraft were available for a July 8 launch.

Finally, teams looked at acquiring the camera’s transmissions via the TDRS (Tracking and Data Relay Satellite) network, but the satellites were not capable of being configured to receive an analog FM TV signal.

In all, part of the problem in planning to acquire the transmission from the ET was in the designed flight path of the ET over open ocean.

Specifically, each Shuttle mission’s ascent profile was specifically designed so that the bulk of the ETs flight paths were over the ocean.

More so, each Shuttle mission’s ascent profile was carefully designed to ensure that the ET would destructively reenter Earth’s atmosphere over the ocean and avoid, by a large degree, any populated land masses and heavy-use shipping lanes.

For the majority of the Shuttle Program, this resulted in the destructive disposal of the External Tanks over the Indian Ocean and the southern Pacific.

One notable and recent deviation from this was the disposal path for the ET from the STS-125/Atlantis mission to the Hubble Space Telescope in May 2009.  That disposal path tracked a few hundred miles southeast of the Hawaiian islands to a few hundred miles west of the western coast of Mexico.

But the flight and disposal paths were not the only thing that played against the odds for the STS-135 endeavor; the considerable lack of knowledge regarding the ET’s post-Orbiter separation attitude also factored into NASA’s effort.

As noted by the PRCB presentation, “There is no attitude control for the tank during entry. Shortly after Orbiter sep, the tank is regularly observed displaying a slow 3-axis random tumble.

“The unstable attitude is presumed to continue until Entry Interface and breakup.”

Thus, any TV reception of the tank would have been unpredictable and intermittent at best - as proved by a very, very brief and static-filled image received as the ET tumble over Europe about 25 minutes after launch.

Additionally, “It is presumed that after EI a plasma sheath will envelope the tank and either prevent or make very difficult any subsequent TV signal transmission and reception,” notes the PRCB presentation.

“A basic assumption has been made that any meaningful TV reception apparatus must be positioned upstream of EI.”

Because of the lack of knowledge of ET death dynamics, NASA was unable to confirm if a plasma blackout condition would interrupt TV transmission signals from the ET prior to its breakup.

Nonetheless, while clear live video was never obtained from Atlantis’ ET after it passed downrange from Wallops, the attempt to do so marked a tremendous effort on the part of NASA to document the tank’s reentry and “death.”

To read about Atlantis and her sisters – from birth, processing, every single mission, through to retirement, click here for the links:
http://forum.nasaspaceflight.com/index.php?topic=25837.0

Click here for the amazing MaxQ Entertainment STS-135 Mission Review Music Video:
http://forum.nasaspaceflight.com/index.php?topic=26178.0

(Images: Via L2 presentations and NASA.gov. Further articles on Atlantis will be produced during her down processing, driven by L2′s STS-135 Special Section which is continuing to folow the mission at MMT/MER level through to post flight IFA, surrounded by a wealth of FRR/PRCB/MER/MMT and SSP documentation/pressentations, videos, images and more.

(As with all recent missions, L2 is providing full exclusive level mission coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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STS-135 Latest:

Following the completion of the final S0017 Terminal Countdown Demonstration Test (TCDT) for the Space Shuttle Program (SSP), STS-135′s flow is now officially into preparations for the Launch Countdown (S0007 operations), as Atlantis closes in on her July 8 launch date target.

A sign the launch date is getting closer is usually marked with waves of tankers heading to the pad, with Friday no exception as two convoys of LH2 tankers replenished the Liquid Hydrogen tank at the pad complex.

With Atlantis safely tucked away inside the Rotating Service Structure (RSS), a final walkdown of her payload was also carried out on Friday, while the Sensor Package 1 (SP1) was re-installed and retested on the end of the Orbiter Boom Sensor System (OBSS) after showing signs of a problem last week.

At the top of the stack, technicians have wrapped up their Non Destructive Evaluations (NDE) on the circumference of the LO2 and LH2 flanges at the top and bottom of the Intertank.

The X-Ray and Backscatter inspections checked the support beams – known as Stringers – ensuring they remained crack-free, following the recent Tanking Test, which was called for after STS-133′s ET-137 suffered from cracked stringers ahead of Discovery’s first launch attempt last year.

No issues were expected, given ET-138 had already been modified with radius blocks, a proven mitigation procedure to strengthen the Stringers as they endure the stresses of cryo temperatures and pressure cycles during tanking.

“ET NDE operations: NDE X-rays on the LH2 flange were completed and are in review. This completes the ET NDE x-rays barring any required re-shoots,” noted the NASA Test Director (NTD) report (L2). “No problems have been detected on the x-rays that have been analyzed to date.”

ET/Stringer Specific Articles: http://www.nasaspaceflight.com/tag/et/

Work will continue over the weekend to remove the NDE equipment from the pad, pending the confirmation all the required data has been gathered.

No notable Interim Problem Reports (IPRs) have been charged to Atlantis of late, with the latest – IPR-50, relating to a SSME-2 GN2 heater issue – only requiring a micro-switch adjustment and solder joint repair.

STS-135 Specific Articles: http://www.nasaspaceflight.com/tag/sts-135/

SSME-3 MFV Update:

The main IPR of interest – IPR-49, relating to the MFV on SSME-3 – is close to being resolved, as much as the real test will come on launch day when cryogenic propellant is once again rushed through the system. It was that environment during the Tanking Test which found the problem with the MFV, as outlined at the crew briefing provided by engineers during the TCDT.

“Problem: Engine 3 Main Fuel Valve leakage experienced during the ET tanking on 6/15/11. A contingency procedure was worked to isolate the fuel system (close all LH2 prevalves, LH2 recirculation iso valves and the LH2 hi-point bleed valve) that allowed us to continue with the tanking test,” noted the Crew Briefing presentation (available on L2).

The MFV is a ball valve with a 2.5-inch tubular flow passage and is flange-mounted between the high pressure fuel duct and nozzle diffuser. The valve controls the flow of fuel from the HPFTP (High Pressure Fuel Turbopump) to the coolant circuits and preburners.

Notably, a root cause of the leak is yet to be confirmed – something NASA engineers always prefer to have in the bag ahead of launch. It is hoped an obvious problem will be spotted by engineers at the MFV’s home in California, where the removed hardware was sent to this week, allowing for an overview to be provided at the L-1 Mission Management Team (MMT) meeting.

“Root Cause: Cause of valve leakage unknown until a failure analysis completed,” added the presentation. “Resolution: Valve removed, replaced and retested (but not under cryogenic conditions) before launch. An update on this issue will be given at the LCD L-1 briefing. Impact to this flight: None anticipated.”

The issue was also covered in depth via the STS-135 SSP Flight Readiness Review (FRR) presentation for the SSMEs, which covered how the issue was spotted during the Tanking Test, as it breached the Launch Commit Criteria (LCC) limitations. As a result, the issue would have scrubbed the launch day countdown, showing a bonus side-effect of finding the problem during the Tanking Test.

“Issue: STS-135, ME-3 (2045) Main Fuel Valve (MFV) skin temperatures indicated a MFV leak during the early stages of STS-135 tanking test. Temps violated minimum limit (LCC SSME-02). Tanking test continued with engines isolated from the fuel supply,” noted the FRR presentation.

The reference to the skin temperatures relates to sensors mounted to the outside wall of the downstream duct of the MFV to detect leakage during chill. Low temperatures are indicative of a MFV leak. The LCC limits are based on the vast flight experience of the Shuttle Program.

Although – as mentioned in the Crew Briefing presentation – no root cause has yet been found, a likely suspect failure path was presented to the SSP FRR.

“Most Probable Cause – MFV ball seal leak: Data appears real. Characteristics match previous ball seal leaks,” added the SSME FRR presentation for STS-135. “Scenarios assessed as unlikely: Liquid nitrogen dripping on sensors. Inconsistent with data characteristics and time in chill. Damaged instrumentation. Inconsistent with data characteristics and visual inspections.”

The FRR presentation also noted that there have been two other MFV leaks in the flight history of the Space Shuttle, listed as STS-2 – where metallic contamination found upon disassembly, and STS-73 – attributed to transient contamination (solid N2).

In addition to the above, 20 pre-start MFV leaks have observed during ground tests, half of which are attributed to solid N2 contamination, which is usually caused by an intermittent helium fuel system purge, allowing the solid N2 to form on the MFV.

By way of mitigation, a continuous purge was implemented into the procedures, meaning STS-135′s SSME-3 MFV issue is the first such leak since efforts were made to prevent sold N2 build up.

Almost immediately after the suspect leak was observed during the Tanking Test, engineers knew they would have to replace the MFV, resulting in a plan of action for work to take place at the pad.

“KSC Plan of Action: Ambient ball seal leak check completed – Zero leakage. Aft access Saturday, June 18. Detailed inspection in the area at KSC & Valve Room (on MFV and above MFV skin temp sensors). Valve removal midweek. Ship to Canoga, Californian for investigation,” added the FRR presentation.

“Borescope and visual inspection of fuel system. Replace with spare MFV. Perform standard system checkouts. Bubble soap leak checks. Valve and actuator functional tests. Helium signature and ball seal leak checks. FRTs Saturday, June 25. Helium Signature test Sunday, June 26.”

All work up to the weekend’s testing was completed on schedule, allowing for the Flight Readiness Test (FRT) to take place on Saturday, after the Dome Heat Shield around SSME-3 was re-installed.

“IPR 0049 SSME 3 Main Fuel Valve (MFV) R&R update: SSME 3 MFV electrical mates were completed. Heat shield installation is in work,” added the NTD report – with L2 updates noting the shield is now back in place. “MFV retest is scheduled for this weekend and will include SSME 3 FRT on Saturday and He Signature test on Sunday.”

UPDATE: Due to an unspecified hydraulic leak on the vehicle, the helium signature test has been delayed until at least 4am Monday. The issue is being tagged as IPR-53, pointing to two additional IPRs over the weekend. A full overview of the latest IPRs are expected via the NTD report on L2 around 7am Monday.

UPDATE 2: Leak was minor and SSME-3 MFV retests have been successfully completed.

These tests include the use of a mass spectrometer device, which will sniff for any helium leakage as the MFV is purged. Should no leak be detected, it is highly unlikely a leak will be suffered during launch day.

As such, the SSP FRR accepted the flight rationale for the engines to proceed to the Agency FRR at the Kennedy Space Center (KSC) on Tuesday, pending the successful conclusion of testing on the newly installed MFV.

SSME Specific Articles: http://www.nasaspaceflight.com/tag/ssme/

“Flight Rationale: LCC SSME-02 in place to protect for excessive MFV leakage. Safing procedures in place for hydrogen leak. SSME GN2 purge and helium fuel system purge dilute MFV leakage. Worst case impact is launch scrub. Pending results of valve and engine inspections. The Atlantis Main Engines are in a ready condition for STS-135.”

This article will be updated as information arrives on the weekend testing progress.

Fun Item:

Known by some of her engineers to be somewhat of a diva during some of her flows, with some of her dedicated workforce nicknaming her “Britney” (Spears) and others nicknaming her “the penguin”, both for seperate reasons which may become apparent when googling both names – Atlantis should now have a clear path for a managerial approval of the July 8 launch date.

She may also be on her best behaviour, after the Crew Briefing presentation noted Atlantis will be carrying an extra item into orbit next month, in the form of a man’s gold wedding band, which was listed as one of the items lost and unrecovered during her STS-135 flow.

Listed as one of five items on the “Lost, Not Found” pages of the Crew Briefing presentation, the gold wedding ring was noted as lost on the orbiter – in the Crew Module - back on March 7. Efforts to find the item have proven to be in vain and now will remain on board until Atlantis undergoes post-mission deservicing.

While the owner of the ring may have received an ear-bashing from his wife, the engineer can look forward to proudly announcing he was reunited with the space flown ring by Atlantis when she returns to her Orbiter Processing Facility (OPF)… providing she doesn’t take the opportunity to propose to another vehicle whilst on orbit.

(Images: Via L2 presentations and NASA.gov (KSC). Further articles on STS-135′s status in work, driven by L2′s fast expanding STS-135 Special Section which is already into the FRR content and live flow coverage, plus more. As with all recent missions, L2 is providing full exclusive level flow and mission coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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STS-135 Pad Flow Latest:

The TCDT – otherwise known as S0017 operations – is a full scale dress rehearsal for the big day, allowing the STS-135 crew to conduct Emergency Egress Training, along with suiting up and ingressing Atlantis for a simulated countdown. The operations began at 7:30am local time on Wednesday, ending with a simulated countdown to T-0, marked at 11am local on Thursday.

Atlantis’ engineers also met with the crew at the TCDT L-1 meeting on Wednesday, briefing the astronauts on the health of their orbiter. The meeting discussed the brake fire from Endeavour’s landing on STS-134 – of which there are no real concerns – through to ongoing work with the Main Fuel Valve (MFV) replacement on SSME-3 (Space Shuttle Main Engine). 

The engineering teams also presented Commander Chris Ferguson and his crew with a large cardboard key to the orbiter with all the systems engineers signatures on it.

Meanwhile, teams are continuing to secure Atlantis’ payload, known as S0600 Vertical Payload Operations. This included work on the Orbiter Boom Sensor System (OBSS), which was observed to have an issue with a camera on Sensor Package 1.

“The Remotely Operated Electrical Umbilical (ROEU) mate/functional checkout and the Pico-Sat Solar Cell (PSSC) installation were completed,” noted the NASA Test Director (NTD) report (L2). OBSS Sensor Pack 1 and 2 update: During testing of OBSS Sensors, problem with camera on SP1. I Iris will open and close manually but will not respond in auto.

“Potential removal of SP1 and return to Flight Crew Lab to verify whether the Test controller box or the Camera that is discrepant. There is a spare camera on site if it is required.

“There was a galled nut plate discovered during the installation of the RMS Sideview Camera (RSC), and it has been repaired. As a result, the RMS side view camera and thermistor testing have been rescheduled to Friday.”

Technicians are also carrying out methodical inspections of ET-138′s flanges, scanning the Thermal Protection System (TPS) foam for signs of cracks in the underlying stringers. The checks are being carried out after last week’s Tanking Test, so as to ensure the radius block modifications have provided the expected protection against the problems suffered by sister tank ET-137.

“Supported the successful tanking test. Electrical, propulsion and thermal were all nominal performance. There is no evidence of any off-nominal structural performance at this time,” noted ET management on the Shuttle Standup/Integration Report (L2). “The Failure Investigation Team (FIT) inspection did not show any anomalies.”

So far, NDE (Non Destructive Evaluation) inspections – carried out via the use of X-Rays and Backscatter equipment – have found no issues with the LO2 flange, which is the main area of interest. Scans are now taking place on the lower LH2 flange on the Intertank, which are expected to wrap up by the end of the week.

“ET NDE operations: NDE X-rays are in work and will continue through the week. The NDE on the LO2 flange was completed,” added the NTD report. “The equipment and ET access platforms were re-positioned and NDE on the LH2 flange is in work. No problems have been detected on the x-rays that have been analyzed to date.”

While the Tanking Test found a problem with the MFV on SSME-3 (see left), with work continuing on installing a replacement valve, another smaller problem was found with an indicator on LO2 17 inch disconnect valve.

“Had a small valve problem during the tanking test on PD #1, which is the LO2 17” disconnect. It has two position indicators for the “Open” state. The “B” indicator did not come on. It was working last week. It was cycled a couple of times, but still did not work,” noted the Orbiter Project Office (OPO) on the Standup report.

“The team will troubleshoot the problem to try to recover the indication. If they cannot, LCC (Launch Commit Criteria) is one of two, so it would still be “GO” for launch.”

This issue, charged as IPR-45 (Interim Problem Report), now has a root cause, found by engineers out at Pad 39A during their investigations into the problem, while preparations are being made for the retests on SSME-3′s MFV (IPR-49).

“IPR 0045 PD1 LO2 17” disconnect open B indicator update: Troubleshooting revealed faulty wiring. R&R of the connector and associated wires in work,” added the NTD. “IPR 0049 SSME MFV R&R update: Replacement MFV installation was completed. The wire harness connector and associated wires were R&R and reconnected to the valve. The retest is scheduled for next Wednesday.

“MFV retest is currently scheduled for this weekend and will include SSME 3 FRT and He Signature test.”

STS-135 Specific Articles: http://www.nasaspaceflight.com/tag/sts-135/

ET Camera Mod:

As previously reported by this site, managers have approved a modification to the External Tank camera which is mounted inside the tank’s liquid oxygen (LOX) feedline fairing. The modification will allow for continuing footage of the tank, after separation from the orbiter, through to re-entry.

The modification involved the rewiring of the camera’s battery pack – specific to the G-Switch timer activation – allowing it to film from lift off, through ascent to MECO, but then allowed to continue operating through until the ET breaks up – depending on how long the camera survives as the tank re-enters.

This modification work has since been carried out at the pad during the continuing NDE inspections of ET-138′s stringers, with retests conducted on Thursday.

“PRCB request to assess feasibility of leaving LO2 feedline camera on and recording the downlink TV signal for as long as possible until ET entry and/or breakup,” outlined a Program Requirements Control Board (PRCB) presentation on the modification’s approval. “Receiving facilities must be able to receive and record analog FM TV signal.

“Two parts to the problem: Coordinate with countries regarding transmitting in airspace. Disable ET FL Camera timer that would otherwise turn the camera off at L+15 mins. Identify and secure receiving stations along ET flight path.”

Due to the lack of TDRS ability as an “overhead option” – given they are not configured to receive analog FM TV – a Special Temporary Agreement (STA) was submitted to National Telecommunications and Information Administration (NTIA) for 30 days beginning July 8 for European airspace transmission, with an agreement reached with DoDand Germans.

Work had also begun to re-activate Diego Garcia (REEF) ground station, while Navy ship-based assets are still being investigated. Aircraft options, such as the P3 Orion, were classed as unavailable.

With the aforementioned work in place, and the camera transmitting through until the tank’s destruction, the opportunity to gain first-of-its-kind imagery of a tank’s death plunge is now on the cards. However, it is questionable as to the quality of the footage.

“It is presumed that after EI (Entry Interface) a plasma sheath will envelope the tank and either prevent or make very difficult any subsequent TV signal transmission and reception,” noted the PRCB presentation. “A basic assumption has been made that any meaningful TV reception apparatus must be positioned upstream of EI.

“We have not yet been able to analytically confirm if a plasma blackout condition will present a TV reception problem prior to breakup.”

Another problem will be the tank’s tumble, given there is no attitude control for the tank during entry.

“Shortly after Orbiter sep, the tank is regularly observed displaying a slow 3-axis random tumble. The unstable attitude is presumed to continue until EI and breakup,” the presentation continued.

“Any TV reception will most likely be unpredictable and intermittent. It is unknown if the tank assumes a more stable aero attitude during entry. A fusion tool analysis has been requested using STS-134 crew handheld HD video to quantify tank tumble rates.”

From an engineering standpoint, the actual modification work on the ET camera was relatively simple, requiring only a single wire to be clipped in the electronics box to disable the timing circuit.

“Description of Change: Crit. 3 ET camera system electronics box modified to allow operational run time beyond currently designed run-time (15 minutes after g-switch activation),” noted STS-135′s ET-138 SSP FRR Presentation (all FRR presentations available on L2).

“Change requested by SSP to provide extended video of tank during re-entry / break-up. Change requires deactivating timer circuit by removing g-switch signal to logic board (g-switch wire clipped, insulated and taped). Camera operation now limited by battery life (~90 minutes).”

The approval for the modification came after the work was successfully demonstrated on a spare box at the Michoud Assembly Facility (MAF) in New Orleans.

“Rationale for Acceptance: Modification demonstrated on spare unit at MAF. G-switch verified operational prior to modification. Electronic box output verified beyond 15 minutes run time (>40 minutes before manually shut down),” added the FRR presentation.

“Electronics box lid to be re-installed per engineering requirements. RTV sealant applied to mating surface. New fasteners / loctite. Camera system open-loop functional test planned to re-verify system operation. Battery re-charged prior to launch.”

The FRR presentation also listed the expected problems with the footage, adding that technicians will attempt to record the video feed, as opposed to feeding it live to NASA TV, etc.

“Performance Expectations. Camera lens / visibility may be obscured due to TPS erosion during highheating re-entry environments. Real-time video coverage limited by ground tracking station availability. Majority of data expected to be recorded and not live feed.”

However, the PRCB presentation did add that the video of the footage will be made available, likely prior to an edit, similar to other videos recorded on orbit, prior to transmission on NASA TV.

In summary, the FRR approved the change – pending no dissent at the Agency FRR next week – with hope a good level of unique footage will be captured via the modified camera system.

“Camera System Modification Provides Robust Option to Provide Video. Coverage of ET During Re-entry,” summarized the ET-138 FRR presentation. “Modification Demonstrated on Spare Unit. Change will be Implemented via Field Engineering Change.”

(Images: Via L2 PRCB and FRR presentations. Further articles on STS-135′s status will be provided as information arrives, driven by L2′s fast expanding STS-135 Special Section which is already into the FRR content and live flow coverage, plus more. As with all recent missions, L2 is providing full exclusive level flow and mission coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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