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Endeavour already has her game face on at Pad 39A, with no Interim Problem Reports (IPRs) of note – at least from her own hardware perspective – for some time now.

The lack of issues has also aided what continues to be a nominal pad flow, which has seen the completion of ordnance installation and the beginning of preparations for the pressurization of the Main Propulsion System (MPS).

“OV-105/SRB BI-145/RSRM 113/ET-122 (Pad-A): LOX storage tank sampling was completed last Friday. ET Camera battery charging was also completed Friday. S0007, Launch countdown preps continue,” noted the NASA Test Director (NTD) report (L2).

“S5009, Final ordnance installation is complete. Range safety system testing was completed. Orbiter/SRB PIC tests and ignition S&A rotation are in work at the time of this writing. It is anticipated that the pad should be re-opened at approximately 0730 EST this morning. S0071 Hyper/MPS pressurization preps call to stations is scheduled for 1600 EST tomorrow. GO2 recharge is scheduled for Wednesday.”

Endeavour’s mission continues to be refined, with one recent memo outlining the current plan for the working mission timeline, one which holds the option of being extended past the 14 day flight into a maximum 16 day primary mission.

“To avoid any confusion, we have removed all what-if timelines, and have left only the official 14+2+2 Flight Plan for you to peruse,” noted one MOD memo (L2). “Once the calm settles in, we will work to re-post the +1 and +2 versions. Until it all changes again.”

STS-134 Specific Articles: http://www.nasaspaceflight.com/tag/sts-134/

Also mentioned was the latest trajectory data, utilizing the middle ground of 15+1+2 as the baseline. The data relates to Endeavour’s rendezvous with the International Space Station (ISS) and departure – the latter of which will include the STORRM (Sensor Test for Orion Rel-Nav Risk Mitigation) Detailed Test Objective (DTO).

Designed to collect detailed data during rendezvous, proximity ops, and (un)docking, Endeavour’s crew will document, via photographs, all STORRM targets for photogrammetry objectives following Shuttle/ISS hatch opening and prior to Shuttle/ISS hatch closure.

“This trajectory data was generated using the L-25 days ISS vector. It includes a 15+1+2 mission duration and an ISS phasing strategy which results in a STS-134 rendezvous altitude of 187 nm,” added the memo. “The Orbiter ephemeris includes a FD14 midnight undock, followed by a 27 min Vbar separation, a 46 min fly around, a 1.5 fps SEP1 burn (3 fps effective) and STORRM DTO maneuvers starting with SEP2.”

To accomplish the STORRM DTO, just after undocking from the ISS, Endeavour’s Commander and Pilot will perform the standard back out and ISS Flyaround maneuvers through the Sep 1 burn. However, in terms of nominal Shuttle/ISS undockings, Flyarounds, and separations, this is where the similarity for STS-134 will end.

Endeavour’s Sep burns 2 and 3 (including all the mandatory STORRM burns) have been redesigned to facilitate a mini re-rendezvous with the ISS to “accomplish the STORRM re-rendezvous objectives” before completing the flyout of Endeavour to a point “in front” of the ISS in terms of the vehicles’ orbital trajectories and relative positions.

Storm Damage Evaluations:

It was a different type of Storm which gained attention at the latest Program Requirements Control Board (PRCB) meeting – ahead of its subsequent promotion to the Flight Readiness Review – with the recent severe storm weather damage evaluated and found to be of no concern ahead of Endeavour’s final launch.

A large amount of concern was forthcoming via four evaluation presentations (all available on L2), which reviewed the lightning strikes observed near the pad. Thankfully, none were classed as direct strikes, via the array of instrumentation and protection which is in-situ at the pad complex.

“One Lightning Strike Determined to be within 0.45NM, but not within 0.30NM. GSE (Ground Support Equipment) Walkdowns for Lightning. GSE/Facility Lightning Strike Walkdowns – were performed and Complete for 30 March 2011 Strikes,” noted one of the presentations.

“31 March Lightning Strike confirmed (by OTV – TV cameras) to be at Sea, away from LC-39. Did not Trigger 2nd Run of Seq 12, but Walkdowns occurred after both Events. No Damage Found.”

“Lighting assessment: Lightning was detected in the vicinity of KSC LC-39 on March 30 and 31, 2011. Concurs with the April 5 joint ERB conclusions that there are no issues, and retests are not recommended for SSP systems due to that lightning.”

High winds from the storms were also evaluated, this time focusing on the associated hardware with the Ground Umbilical Carrier Plate (GUCP). The concern relates to the wind loads on the vent arm potentially translating on to the GUCP, causing a potential misalignment to form – something which engineers would wish to avoid given the recent leaks from the hardware, including STS-133′s ET-137.

“Winds on 3-30-2011 at Pad A were recorded to 78.7-knot from the Southwest (2200-2600). The following concerns due to the high winds will addressed:. Concern 1: Did the high winds move the vehicle outside of the tested excursions? Concern 2: Are the loads induced into the Umbilical including 7-Inch QD/GUCP by the high winds a concern?”

Thankfully, the evaluations resulted in positive results, as the analysis showed the 78.7-knot gust was within tested limits, noting the Haunch Pivot Arm angle was within tested limits and that the axial load into 7-inch QD, GUCP and Pyrotechnic bolt were all within the required parameters.

“Analysis shows the 78.7-Knot gust recorded is well within the tested system limits. Pivot Arm and Vent Line angles are less than tested excursions. Pivot Arm angle controls axial load in Vent Line. Calculations show a 5.25 safety factor at the 7-In/GUCP Interface,” added the GUCP specific presentation.

“The peak gust was 30 degrees perpendicular to vent line centerline (perpendicular wind used in calculation). Inter-tank access arm helps protect the vent line from winds (not used in calculations). 2 g’s dynamic factor very conservative.

“Pending completion of nominal planned work, the GH2 vent line including 7-in QD/GUCP are ready to support STS-134 launch countdown.”

The final evaluation related to the hail damage to the top of ET-122, which only resulted in minor Thermal Protection System (TPS) damage, well within acceptable limits.

“Assessment: External Tank assessment of 03/30-03/31 severe weather event and affect on ET-122,” noted the Lockheed Martin presentation on the tank. “Actions Taken: Performed visual and hands on inspection of ET hardware. Impacts primarily on the -Y / -Z quadrant. No indications / impacts observed on composite nose cone.

“Visual indications / minor damage observed on LO2 tank and Intertank acreage TPS and components. Majority of TPS impacts < 0.10” deep. Characterized as superficial or witness marks (no discernible depth). Performed sampling of ‘worst-case’ depths using scale (defects >0.10” deep). Performed loads evaluation of 78.7 kt peak wind. Peak wind condition exceeds design certification environment (74.5 kt).”

Although the flight rationale was always expected – given the lack of any noticeable damage – the depth of the evaluation is a testament to the amount of data and flight history the Shuttle Program utilizes to ensure they are confident the flight hardware is in an acceptable condition.

“Rationale for Acceptance Summary: Composite hardware is damage tolerant. No visual indications. Testing at 20 ft-lbs impact energy result barely visible damage. Max impact energy for ET-122 hail event is 0.62 ft-lbs (0.47” hail at 107 mph winds),” the presentation added.

“Bounded by ET-124 Max impact energy of 5.92 ft-lbs. Residual hail defect locations do not provide a leak path across the GO2 Vent Seal Land surface. Similar to condition accepted after launch scrub (after vent hood retraction). No continuous leak path over face of dock seal land. Aero recession performance assessed to be nominal.

“ET-122 damage is bounded by ET-124 hail damage testing. Surrounding TPS analyzed at higher recession rates around the cavity. Residual crushed foam ablates at nominal rates as demonstrated by test (crush damage 5, 10, 15 and 20 percent for 1” thick TPS). Crushed foam liberates as normal ablation products. Thermal assessment. No impact to ascent or entry requirements.”

ET-124′s data is highlighted by the evaluations, due to the damage it suffered from a hail storm ahead of the STS-117 launch in 2007, resulting in the rollback of the stack for repairs in the Vehicle Assembly Building (VAB). However, the presentation also used data from ET-129 as part of the rationale. Even post-Return To Flight data was used to back up the readiness of the tank to fly.

“Condition enveloped by similar condition analyzed for STS-126 / ET-129. No impact to icing and launch probability requirements. Configuration of ET-122 hail damage sites would be encompassed by the icing tests done for ET-124 hail damage to meet an 85 percent Launch Probability requirement. No impact to propellant quality requirements. Insignificant quantity of impact sites to affect propellant quality.

“TPS Debris Assessment: Undetected crushed foam due to collateral damage was a major emphasis during RTF II. Large amount of mechanical property and performance testing previously performed to understand performance of both detected and undetected crushed foam. Results of tests showed no impact to TPS performance for crush levels (up to) 20 percent (visually detectable).”

With the ERB debating the status of the vehicle ahead of the PRCB, along with the PRCB then providing the documentation to clear the tank to fly, the Agency FRR did not have to spend much time in concurring with the evaluations, and passing ET-122 to fly as-is.

Another article will follow on the specifics of ET-122′s FRR documentation, including the previous tank (ET-137) performance during STS-133′s launch - and the history of the 10 year old tank which is set to fly with Endeavour.

(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: All via L2 content and L2 presentations).

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Over the weekend, S0009 Launch Pad Validation tasks were completed, following Discovery’s return to Pad 39A last week. Discovery is tracking an opening launch attempt on February 24 – providing the Ariane 5 ECA launch with ATV-2 launches on its opening attempt on February 15.

Tasks over the last few days included the removal and replacement of a Range Safety battery, a GPS retest, SSME (Space Shuttle Main Engine) Ball Seal leak checks and a temperature transducer mass spec leak check on Discovery’s Main Propulsion System (MPS), allowing for the transition into S0024 operations on Monday morning.

The loading of the toxic hydrazine fuel into the Hydraulic Power Units (HPUs) on the SRBs – which requires the pad clearing of workers for specialist engineers to carry out the loading in their Self-Contained Atmospheric Protection Ensemble (SCAPE) suits – began at 9am local.

“S0024 SRB HPU hyper load: The orbiter is powered up and being configured for remote ops. HPU load call to stations should be completed shortly,” noted Monday’s NASA Test Director (NTD) report (L2). “Pad A is scheduled to be cleared by 0800L this morning. HPU hydrazine load is scheduled to begin at 0900L this morning.”

Three relatively minor Interim Problem Reports (IPRs) were also listed; one of which is already in the process of being closed, another relating to troubleshooting on a flight cap on a SRB and one issue on Space Shuttle Main Engine 1 (ME-1) likely to receive a waiver. IPRs at this stage of the pad flow are common.

“OV-103/SRB BI-144/RSRM 112/ET-137 (Pad A): New IPR 0083 to MPS. During Engine FRTs (Flight Readiness Tests), ME1 (SSME Number 1) Reg B pressure exceeded OMRSD (Operational Maintenance Requirements and Specifications) limit twice (Actual was 782.2 psia, OMRS limit is 780 psia.),” the NTD added. 

“Engineering plans to discuss regulator transducer R&R and/or OMRS waiver. Constraint: S1287 Op 30-105.

“New IPR 0084. During the modified un-commanded extend for HYD-257, ET actuator extension did not stop as expected. Engineering is evaluating a troubleshooting plan. Constraint: S1287 Op 30-105 (Current plan is to close the IPR as an explained condition).

“New IPR 0085. While removing the left tilt GN2 press & purge QD (Quick Disconnect) flight cap, techs noticed vapors as well as liquid coming from the poppet. The poppet was sniffed hot, therefore the techs flushed with IPA and reinstalled the flight cap.

“TVC’s (Toxic Vapor Concentrations) with the cap installed are 0.0 ppm. PC goal does not show any pressure deltas during the time of cap removal. The system was drained prior to rollback to the VAB and any commodities present are just residual vapors. Engineering plans on troubleshooting today after getting into SCAPE ops. Constraint is to left tilt system loading.”

STS-133 Specific – Including ET Stringer Issue – Articles: http://www.nasaspaceflight.com/tag/sts-133/

Other work which was completed prior to hyper loading included the Orbiter Mid Body Umbilical Unit (OMBUU) mate/leak checks, ET camera functional test, 1st motion test, and the GUCP leak checks.

No issues with the GUCP were listed during the early Monday NTD report, however sources noted that later in the morning a call to disassemble the GUCP at the pad was made by mangers, due to what was noted as a failed leak check.

While the system can detect leaks in realtime via instrumentation, the tank is unpressurized and won’t reach cryo temperatures until the day of launch during tanking, meaning engineers can only carry out ambient temperature tests on the hardware – as per scheduled.

Sources have noted that Friday’s leak check did result in a small leak, so small that it was initially thought to be nothing more than noise in the detection system, though it is possible that due to the troublesome history of the GUCP of late, managers decided the system should be dismantled to be absolutely sure everything appears as it should.

UPDATE: Although note of a separate leak – after Friday’s schedule leak checks and ahead of Monday morning – was listed at this time. The NTD did cite a small leak being noted during helium leak checks on Monday.

GUCP leaks caused scrubs on both STS-119 and STS-127 in 2009, prior to being the reason STS-133 scrubbed during the transition from reduced fast fill to topping of the LH2 tank during tanking, when a leak was detected – exceeding the 40,000 PPM limit in the Launch Commit Criteria (LCC – HAZ-9).

While the observed cracks on ET-137′s LO2/Intertank flange stringers – seen after the scrub was called – have been the main focus of attention since the scrub, a root cause for the GUCP leak was successfully found via concentricity measurements, which spotted a misalignment in the system.

With engineers called to “clock” the GUCP’s placement on the tank – and a new two-part flight seal installed – engineers were provided with “free” test of the GUCP via December 17 Tanking Test. This test was called for to aid the investigation into the stringer cracks, but showed the GUCP did not leak at any point during the tanking, adding confidence to the mitigation procedure.

It is likely that the call to disassemble the GUCP at the pad is solely to protect against any potential issues during the tanking for launch next month, with enough contingency time in the pad flow to allow the work to take place without any impact to the NET (No Earlier Than) February 24 launch date.

Once the hardware has been re-installed, engineers will be able to carry out another leak check to confirm the health of the system.

(Further updates and articles will follow. Refer to live coverage threads linked above. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used, Larry Sullivan MaxQ Entertainment/NASASpaceflight.com and via L2 acquired PRCB presentations).

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Now returned to the huge building, Discovery is likely to spend two to three weeks inside the VAB, allowing access to the 360 degree circumference of the two flanges – the upper LO2 area and the lower LH2 area – on the intertank.

At present, the data gained from the Tanking Test may have provided the required confidence that both the two doubler stringers – which replaced the S6 and S7 stringers, both of which suffered from two cracks each – acted in the required manner during tanking and pressurization during the test.

An option to add additional strength via modifications is open to managers, should the Tanking Test and ground test data call for it.

At the Pad, engineers cut the instrumentation wiring from the tank, allowing for rollback. The array of sensors – located in two areas of the tank – will be fully removed once the stack inside the VAB. Foam repairs will then follow, with the ultimate goal of returning the STS-133 stack in a nominal condition for the early February launch attempt.

“OV-103/SRB BI-144/RSRM 112/ET-137 (Pad-A): ET Instrumentation post ops are scheduled. Work will be performed to prepare the instrumentation for rollback and later removal in the VAB,” noted the NASA Test Director (NTD) via processing latest (L2) ahead of rollback.

“S0038/A5217 Rollback to the VAB: The vehicle will be rolled back to the VAB to perform 360 degree NDE (Non Destructive Evaluations) of LO2 and LH2 flanges, remove instrumentation, and repair foam areas associated with the instrumentation.”

STS-133 Specific Articles (click for numerous background content relating to this article): http://www.nasaspaceflight.com/tag/sts-133/

Although the rollback was scheduled for 00:30 on Tuesday morning, first motion was pushed back by delays in removing the hydrogen vent system arm from the tank – a process which has to be completed carefully, in order to avoid any troublesome misalignments to the GUCP on the end of the arm.

However, a problem with the Crawler Transporter resulted in a decision to postpone the rollback for the night. Troubleshooting is focusing on the D-Side of the CT, with scanner conversations noting a potential contact between the D-Side and a cable tray when in transit to underneath the MLP – which may have affected the Jacking, Equalization and Leveling (JEL) hydraulic system.

The NTD noted the issue was pinpointed to a faulty transducer, which has been replaced in time for another rollback attempt to take place around 10pm Eastern. Following a smooth operation, the CT began first motion at 10:48 local, arriving back at the VAB at 7am, with the completion of rollback pending harddown.

Meanwhile, checking the GUCP was classed as a “free” test during Friday’s tanking, which was dedicated towards the gaining of data on ET-137′s stringers. Had the GUCP leak been the only problem with ET-137, a Tanking Test wouldn’t have been carried out. Regardless, the lack of leaks during the tanking has provided a level of confidence that the system will behave once Discovery undergoes another launch attempt.

“S0037 ET Tanking Test: The tanking test was completed successfully on Friday. Good data was collected from all instrumentation installed on the ET. The data is under engineering evaluation but a preliminary assessment shows that the tank performed nominally with actual data closely matching predictions,” added the NTD.

“GUCP repairs were also proven successful with no hydrogen leaks detected. De-tanking, boil-off, and securing from S0037 were completed over the weekend.”

Notes from the Mission Evaluation Room (MER) during the Tanking Test confirmed the GUCP provided no issues to controllers on Friday, with the main focus on the key transitional periods of the loading process.

During tanking, and once the chilldown has been completed, both tanks enter a slow fill, avoiding the cyro-shocking of the feedlines. Loading then transitions into Fast Fill, from which the tank volume is partially filled with LH2, with ullage gas consisting of mixture of GHe and GH2 concentration.

The vent valve begins cycling – the point at which STS-133′s first launch attempt in November was scrubbed – with a tank pressure target of between 32.9 and 43.2 psia.

During the transition to topping, the valve opens and vents high concentration of GH2 and some LH2 into the vent line to be burned off at the Flare Stack. The vent line/umbilical interface is exposed to rapid cryo cool-down and pressure. Once topping has been completed, stable replenish is used to compensate for the natural boil off of the propellant.

“We have started the LO2 and LH2 loading portions of the Tanking Test, on time. All ET Stringer Instrumentation is working properly. Also, now that we’ve started tanking, we will not scrub for any future ET Stringer Instrumentation failures,” added MER notes, confirming the status of tanking (L2), with only one minor IPR (Interim Problem Report) noted during the process, relating only to instrumentation.

“Both LO2 and LH2 are in the Fast Fill portion of ET Loading. Loading is proceeding nominally except for a minor IPR (80) taken for the LO2 replenish valve located on the MLP. Both open indications did not turn on after the valve was opened. A secondary cue (a potentiometer indicating 99 percent open) has verified the valve did, indeed, open when commanded.”

Confirming no leaks from the GUCP at either the time of the previous incident, or closer to topping – the usual time for previous leaks from the GUCP – controllers classed the loading portion of the Tanking Test as nominal.
 
“LH2 has transitioned to the topping phase of loading, which will bring the LH2 tank load to 100 percent. The ET GH2 Vent Valve has been opened with no leakage occurring at the GUCP. The ET Instrumentation verbal report says all data looks “nominal” with no failed data,” added MER notes.
 
“We have reached Stable Replenish for both the LO2 and LH2 systems. Other than the Replenish valve indication issue (which, due to a thermal increase from the Sun now indicates OPEN), this has been a nominal ET load.”

The Final Inspection Team (FIT), plus one member with a telescope, then inspected the tank, as is usual post-tanking. Later, managers gained a “quick look” of the test results, all of which showed expected data on the stringers.

GUCP Investigation Results:

Although the stringers were the primary focus of the test, the amount of work that has gone into ensuring the GUCP is no longer an issue for ET-137 is staggering, and typically NASA.

All had been proceeding to plan during the November 5 launch attempt, 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 (six times) – 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.

With a vast amount of experience from previous GUCP leaks, previously observed during STS-127 – engineers went to work on methodically evaluating the root cause of STS-133′s leak via a fault tree.

“Evaluation: STS-133 troubleshooting plan as compared to the STS-127 Fault Tree. STS-133 GUCP Leak Investigation Team has developed a troubleshooting plan to address the STS-127 GUCP Leak Fault Tree. Residual risk still exists for dynamic characteristics of the system that are not fully understood,” outlined one of a host of expansive – and impressive – presentations on the STS-133 GUCP troubleshooting, available on L2.

“Mitigated through bench leak checks, disassembly and inspection, and analysis. Leak Through QD (Quick Disconnect) Assembly. Sealing surface defects and material properties of the Flight Seal, Bellows Probe and ET Carrier Assembly (ETCA). Materials testing of Bellows Probe and Flight Seal still in work, however considered unlikely contributor…

“…Eccentricity Mismatch Between Seal and Probe. Probe dimensions included for STS-133 Concentricity Assessment. Sealing Surface Contamination including ice and FOD (Foreign Object Debris). Flight Seal Deformation. Flight Seal Retaining Ring Loose. Improper Probe, Flight Seal, and ETCA Build Dimensions ETCA Movement (Intertank movement /vibration including Shuttle).”

With the likely causes pinpointed to a deformation of the flight seal, or a misalignment of the hardware (concentricity), an investigation team found that a misalignment was a leading candidate, following observations of movement in the GUCP ahead of tanking.

“Ground Umbilical Carrier Plate (GUCP) Investigation Team was reconvened. Detailed disassembly of the Ground Umbilical Carrier Assembly (GUCA) and Vent Line Assembly was performed. Observed no anomalies in the vent line assembly,” added another presentation.

“Observed that the GUCP had shifted since the final measurements taken prior to S0007 (Launch Countdown). The plate was originally offset (0.049”) to the 8 O’clock position. Shifted an additional amount toward the 7 to 8 O’clock position. First post disassembly concentricity value was 0.061” to the 8 o’clock position.”

The other leading candidate for the leak was the flight seal, which contributed to the previous GUCP leaks, resulting in a change of design to a more capable two-part flight seal. Initially, engineers checked the seal out at the pad.

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

“Flight Seal observations. Tactile and visual inspections performed (3 independent inspections). Some circumferential deformation at the 7 to 9 O’clock position. Gap of the seal edge to retainer ring appeared smaller at the 7 to 9 O’clock position,” the presentation continued.

The Flight Seal was removed from the hardware and sent to the KSC lab – and later to the Michoud Assembly Facility (MAF) – for analysis, which included Chemical and Nondestructive examinations. Those evaluations revealed some observations of interest, but no anomalies which could have contributed to the leak.

“Chemical analysis was perform on wipes taken during tactile inspection and on debris captured prior to seal removal and on debris captured. Wipes analysis revealed unidentifiable materials that were organic in nature. Debris analysis revealed variety of small metallic and organic particles. Magnified visual inspection of both pieces of the flight seal revealed no anomalies.

“Dimensional analysis of the seal found one minor dimension to be slightly undersized. Dimensional analysis of the metallic outer spring found its diameter to be slightly undersized (is 0.116 s/b 0.120 +/-.002). This dimension was consistent around the diameter indicating the spring was not out-of-round.”

A misalignment soon became the root cause, or major contributor, to the leak, confirmed by concentricity measurements on the SN2 plate used by ET-137, and backed up by previous investigation notes that loads on the vent line can cause the GUCP to shift slightly in one direction. This shift – by only 0.061 inches – provided a gap for the leak to manifest.

“GH2 vent system is composed of numerous components (flight and ground) that combined together on STS-133 to provide a tolerance stack-up towards the 7-8 o’clock position. GUCP to ETCA and to QD Concentricity,” noted the findings presentation.

“Previous GUCP investigation uncovered tendency for ground GH2 vent line loads to affect carrier plate position by pulling the plate towards the 7-8 o’clock. First opportunity for concentricity measurements during disassembly corroborates this tendency. SN2 was found offset 0.061” towards 7-8 o’clock direction.”

While the misalignment itself was an initial leading candidate for the leak, the shift in this particular direction wasn’t expected. However, it provided an immediate solution.

“Significant previously unaccounted for variable of QD concentricity discovered during STS-133 GUCP leak investigation. Clocking QD during installation uses this variable to our advantage. Controlling the variables we can optimize (GUCP & QD concentricity) in a manner that helps us mitigate loading (7-8 o’clock) will provide greater compliance to the system as a whole.”

Such was the confidence in the findings, the presentations also confirmed there was no need for a Tanking Test specific to the GUCP. However, with the stringer crack investigation providing a free opportunity to monitor the GUCP via the associated Tanking Test, managers decided to add reference marks – to be observed by two cameras – to the hardware to facilitate measuring movement of the GUCP/QD during tanking.

“Use imagery to detect movement at GUCP/ETCA Interface during Tanking. Expect to measure approximately 1/10” movement at plate with six Degrees of Freedom (translation and rotation). Reference Marks Requirements: 6 marks on GSE (Ground Support Equipment). 42 marks on ET TPS,” confirmed the recommendation of the Program Requirements Control Board (PRCB).

With the understanding of the issue, and the subsequent replacement of the hardware (carrier plate, flight seal etc) ahead of the Tanking Test, managers are confident the GUCP leak issue is finally behind them.

“The STS-133 Ground Umbilical Carrier Plate and QD concentricity offsets were considered the major contributors to the GUCP leak. The GUCP and QD have been replaced with a set that minimizes the concentricity offset,” added summary notes.

“Analysis of the fault tree identified residual risk due to the relative motion between the GUCP/QD and flight seal due to vent line loads and dynamics, bellows spring force, bellows binding/interference, and the pyro bolt assembly. However, the expectation is that the currently optimized GUCP and QD should eliminate the issue.”

The troubleshooting effort also earned praise from NASA manager LeRoy Cain, who thanked the NASA and contractor teams for their attitude, which he classed as exceptional.

“Thanks to all the folks who have been working the cracked stringer issue, as well as the issue to resolve the GUCP leak. Mr. Cain stated for the ET Project and Lockheed-Martin, the effort being put into this by the team is outstanding across the board,” added notes on the Shuttle Standup/Integration report. 

“The attitude is exceptional; it is really a model for other folks to watch and pay attention on how to work through issues like this.”

(Further updates and articles will follow. Refer to live coverage threads linked above. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used, Lead: Larry Sullivan, MaxQ Entertainment/NASASpaceflight.com. Within the article: via L2 acquired PRCB presentations).

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Delayed by two days due to cold weather and high winds interrupting the engineering efforts to install instrumentation into two locations on the tank, the realigned target of entering Call To Stations (CTS) on Wednesday night was achieved thanks to the completion of foam application tasks, covering nearly 100 sensors, and returning the tank to a nominal configuration.

“OV-103/SRB BI-144/RSRM 112/ET-137 (Pad-A): S0037 ET Tanking Test: Acceptable enclosure, ET skin/substrate, and Conex box temperatures were maintained allowing conathane and foam applications to be completed. The foam (was then) in cure,” noted the NASA Test Director (NTD) reports on pre-Tanking Test preparations (L2).

On Wednesday morning, technicians started to trim the new BX foam on the two stringer locations, prior to adding markers which will be monitored via OTV cameras and later by the Final Inspection Team (FIT) during the tanking process.

“Winds at Pad A finally relaxed enough to allow photogrammetry dot placement to be performed. Dot placement completed early this morning on panel 6 of the -Z side of the ET utilizing the scaffolding on the intertank access arm.”

The next task was to remove the enclosures used to install the instrumentation and reapply foam on the tank, prior to testing the sensors – which proved to be successful. Upcoming key events open with the retraction of the Rotating Service Structure (RSS) on Thursday night, ahead of the start of the Tanking Test at 7am on Friday.

STS-133 Specific – Including ET Stringer Issue – Articles: http://www.nasaspaceflight.com/tag/sts-133/

“ET Instrumentation: The intertank was closed out Wednesday for the Tanking Test. ET sensor channelization test completed Thursday. S0037 ET Tanking Test: LO2/LH2 ET load preps will begin Thursday morning. RSS rotation to park is scheduled for 2130L tonight. Tanking is scheduled for 0700L tomorrow morning.”

Classed as a ‘free’ test, the loading of ET-137 will provide confirmation that the engineering work to resolve the GUCP leak has been successful, following a root cause investigation determining a misalignment of the GUCP assembly – which has since been corrected.

“During the transition from reduced fast fill to topping of the LH2 tank, a leak exceeding 40,000 PPM was detected. Measurements and inspections were performed at each step of disassembly. Measurements showed that the GUCP had shifted since the final measurements were taken prior to S0007 (Launch Countdown),” outlined investigation notes (L2). 

“The GUCP and the QD (Quick Disconnect) probe had an offset clocked in a direction that contributed to the leak. The investigation identified 8 key factors in obtaining a successful mate of the GUCA QD to the External Tank Carrier Assembly (ETCA) – GUCP concentricity, QD probe/flange concentricity, 2 piece seal, GUCA QD’s inconel bellows, vent line loads, ETCA flight carrier plate alignment, hinge support brackets alignment, and the pyro bolt. 

“Of these 8 factors, the GUCP concentricity and the QD probe/flange concentricity can be adjusted within limitations. The GUCP and QD were replaced and the QD clocked to minimize the concentricity offset. Analysis of the fault tree identified residual risk due to the relative motion between the GUCP/QD and flight seal due to vent line loads and dynamics, bellows spring force, bellows binding/interference, and the pyro bolt assembly.” 

Although the engineering community is in agreement that they are in the best posture they can be without changing certified processes and procedures, the Tanking Test will provide the opportunity to watch for any movement during loading, especially in relation to any leak detections.
 
“STS-133 Tanking Test: Baseline GUCP measurements taken before tanking test. High definition camera 4 is installed on Intertank access platform haunch. LH2 and LO2 will be loaded per nominal timelines. Like standard tanking if a GUCP leak is detected the loading team will implement steps to maximize the amount of time the 98 percent sensors stay Wet facilitating vent valve cycling,” added the Tanking Test presentations (L2).

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

“Based on GUCP performance loading may continue to standard stable replenish configuration and beyond. LCC (Launch Commit Criteria) HAZ-09 is a Tanking Test mandatory LCC. Current limit of 40,000 PPM remains applicable for Tanking Test. Team will initiate new IPR (Interim Problem Report if reading is above 20,000 PPM.”

Following the Tanking Test, a 48 hour review of the data will be carried out, while preparations pick up for the rollback of the STS-133 stack to the Vehicle Assembly Building (VAB) for another key milestone in returning the tank to flight status – the full 360 degree scanning of the two flanges on the Intertank.

“S0038/A5217 Rollback to the VAB: Following the Tanking Test, the vehicle will be rolled back to the VAB to perform 360 degree NDE (Non Destructive Evaluation) of LO2 and LH2 flanges, remove instrumentation, and repair foam areas associated with the instrumentation,” added the NTD report.

“Preps for rollback are tentatively scheduled to begin on Monday, December 20. First motion for rollback is tentatively scheduled for 0001L Tuesday, December 21. S0072 HPU (Hydraulic Power Unit) Offload is scheduled for 1100 EST on Sunday, December 19 following LH2 boil-off.”

The STS-133 stack will be returned to the VAB for the Christmas holidays by Crawler Transport 2 (CT-2), following a problem with CT-1.

“Crawler Transporter (CT-1): A PR (Problem Report) was picked up on CT-1 for an intermittent PLC input/output fault and unplanned shut down. As a result, CT-2 will substitute and be moved to the Pad-A gate this morning to support STS-133 rollback to the VAB.”

The stack is scheduled to return to Pad 39A early in January.

(Further updates and articles will follow. Refer to live coverage threads linked above. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used, Lead: Larry Sullivan, MaxQ Entertainment/NASASpaceflight.com. Within the article: via L2 acquired PRCB presentations and NASA KSC).

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STS-133 Latest:

Discovery’s tank is on the right path to complete the required repairs on both the Ground Umbilical Carrier Plate (GUCP) and the cracked stringers/foam, although the schedule is “tight” to fully complete the procedures in time for the start of the countdown – which was to include either an embedded Tanking Test or begin nominally on November 27.

Due to the progress made on the GUCP side of the repairs, a decision has already been made to cancel the Tanking Test which would be part of a six day countdown, with a telecon on Wednesday noting confidence in the GUCP performing as advertised during the nominal tanking on launch day. An option remains for a Tanking Test during S0007 (Launch Countdown Operations), followed by a 48 hour scrub turnaround.

The last time a Tanking Test was conducted came during STS-127′s troubleshooting on what was a second successive GUCP leak during tankings.

Following the GUCP related scrub suffered by STS-133 on November 5, engineers and technicians have successfully reinstalled a new flight seal, along with an alternative carrier plate.

“Disassembly was performed incrementally, taking measurements along the way to compare to installation and historical data. The replacement GUCP and flight seal were installed on Friday and concentricity offset measurements taken,” noted an update to MOD managers (L2).

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

The Quick Disconnect (QD) hardware has also been “clocked”, following the known misalignment found via concentricity measurements.

“OV-103 / SRB BI-144 / RSRM 1 112 / ET-137 (Pad-A):  Ground Umbilical Carrier Plate (GUCP) leak:  GUCP 7” QD installation was completed. The QD was clocked as advertised to take advantage of its known offset. Measurements were taken following QD mate and no movement of the carrier plate was detected,” noted the NASA Test Director (NTD) processing report (L2).

“Because the QD had been reclocked, the spotface on the QD for the vent line bond jumper was in the wrong position for installation of the ice suppression shroud. The jumper was re-spotfaced from the 7 o’clock to the 10 o’clock position, and the Aerogel blankets and shroud were installed correctly.

“Installation of the 3/8” QD’s at the top of the GUCP and GH2 vent line mate were completed. GH2 vent line alignment measurements were good. Vent line leak checks for GUCP retest – No leaks were detected. GUCP retest was successfully completed last night.”

The four cracks in two of the tank’s stringers continues to be the main driver of the schedule, with a repair schedule (L2) showing work will be carried out on the flange area between the Intertank and LOX tank through until later this month. It is also hoped that no further defects are found via the high resolution backscatter and computed radiography x-ray scans that are being conducted on a portion of tank.

“ET Foam Crack: The area of cracked foam was dissected and the underlying structure exposed to gain insight into the cause of the crack. Two cracks on the underlying stringer and two cracks on an adjacent stringer have been identified. The plan is to replace the cracked section of the stringers and utilize a doubler plate to cover the area where the new section and existing section meet,” informed the MOD update.

“Two types of non-destructive evaluation (NDE), high resolution backscatter and computed radiography x-ray, are being discussed as potential data gathering efforts. The repair plan and procedures are being finalized. Investigation into root cause and determination of flight rationale is in progress.”

With the removal of the cracked stringers and the fabrication of the doublers completed, preparations were in work to begin the installation of the doublers on to tank during Wednesday.

“ET LO2/IT stringer cracks: The final fasteners from stringers S6 and S7 have been removed. ET surface preps for doubler installations are in work. Borescope of the remaining 3-4 holes on stringers 6 and 7 is complete. Damage was found on 2 upper holes on both stringers. As a result, ET Mechanical initiated a Problem Report (PR) for drill witness marks on the LOX aft dome,” added the NTD report.

“NDE dye pen on the grinder nicks on stringer S7 were performed with no cracks found. Mold impressions of the nicks on stringer S6 were taken and the nicks were sanded. NDE Backscatter x-ray scanning of the +Y area of the LO2 interface flange picked up and will continue through Thursday on a non-interference basis to ongoing repair work.”

While Stringers 6 through 19 have been scanned, Stringers 1 through 5 were not accessible. The results of the inspections are still being checked as of Thursday morning. Also, one of the doublers required some additional work, after it was found to be too long for its installation on to the tank.

“The S6 doubler was found to be too long, so it was sent to the shop for trimming and is now dimensionally correct and ready for installation,” noted the NTD report on Thursday.

Once the doublers have been installed, BX foam will be sprayed on to the area, which will then mark the start of a three/four day cure time. The required environmental conditions have been satisfied for the spray and cure, via a tent hood being installed around the repair area.

In tandem with the ongoing repair work, managers and engineers are being tasked with the ultimate requirement of creating flight rationale – something which may be very challenging to achieve in time for the upcoming launch window.

It is understood that ET-137′s stringer cracks do not share commonality – or suffered from a “different mechanism” – compared with the history of 38 cracks that have been observed during the production of the tanks at the Michoud Assembly Facility (MAF) – all repaired at the New Orleans factory – an issue that has been suffered by 20 tanks since the switch to a lightweight aluminum-lithium alloy as part of the transition to the Super Light Weight Tank (SLWT).

ET-137 is also understood to be the first tank to suffer from stringer cracks at the pad, at least to the point where it caused a visible crack to the Thermal Protection System (TPS) foam. Sources note that the crack was observed on a camera during tanking/de-tanking on November 5, with the crack instantaneously “popping” into view.

Daily meetings are being conducted to discuss both the repair effort and the root cause, building a knowledge base towards flight rationale.

A joint Shuttle Engineering Review Board (SERB)/Systems Integration Control Board (SICB) was conducted on Tuesday, with Thursday’s all-powerful Program Requirements Control Board (PRCB) meeting likely to provide a major update. (10 Presentations from the meeting now uploaded into L2 during).

Managers will then meet in a Flight Readiness Review (FRR) style Launch status briefing, (UPDATE: Now delayed to Monday, November 29), prior to updating reporters on the state of play.

Discovery was aiming for opportunity to launch in a window which ranges from November 30 to December 6 – although there may be refinements available over the coming days. Those refinements came on Thursday, with a slip (although no real date had been previously set) of the launch date to NET (No Earlier Than) December 3 through to December 7.

“If we slip 133 past the December window, then we will be in February, because there is a big beta cutout and cutout for HTV,” noted MOD Director Paul Hill in recent notes, before conversations this week spoke of what is currently only a potential option to create another window in December.

STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/

Created by the SSP, ISS managers have been asked to assess the preliminary option of a window opening on December 17. Challenges would include the need to offload around 600 lbs of payload from the mission, in order to provide the required ascent performance margin during such a window.

It is not clear how long such a window would last, which would be key for the potential of Discovery being on orbit on through to New Years Day, as this would trigger the YERO (Year End Roll Over) consideration. YERO is a problem which was first highlighted when Discovery’s STS-116 launch window was restricted to launching before the mission could overlap the change of year.

The problem relates to the shuttle orbiter’s computers needing to reset through a change of year, which could cause a glitch on orbit. While a contingency was already in place – involving the orbiter remaining docked to the International Space Station (ISS) during a YERO event – a final solution was requested by previous shuttle manager Wayne Hale.

“When (the shuttle computers) were originally programmed – the basic operating system was built back in the 1970s – it was not envisioned that we would fly across the end of the year, so we didn’t handle it very well,’ noted Hale during the pre-flight briefing three years ago.

“We’re making some changes to the way the software works, which will be fairly simple and easy. So if we need to at the end of this year, fly across the end of the year, we will be able to do that.”

Despite the solution being found, as documented by the PRCB, it has always remained a contingency in the unlikely event an orbiter was on orbit, and undocked from the ISS, during the change of year. It is possible that managers will plan a mission – should the notional second window in December be taken – to avoid such a scenario.

A range of options is always the norm for NASA, with the goal continuing to be one which aims for launching Discovery in the initial December window.

(Further updates and articles will follow. Refer to live coverage threads linked above. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used, via NASA.gov and L2 documentation).

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STS-133 Latest:

Discovery continues to track a preliminary NET (No Earlier Than) launch date of November 30 – based on the opening of the next available window – although an actual launch date is likely to remain unset until at least November 22, when a full managerial meeting on the status of Discovery’s tank is held.

Resolving the two main issues with STS-133 – both on the External Tank – will continue to drive the ability for NASA to either push forward towards the short window that runs through the first week of December, or standdown until the next window late in February, in turn delaying STS-134.

The actual repairs of the tank – as it stands – have a fair chance of being resolved in time. However, the required confidence, or Flight Rationale, on the cracks in the tank’s stringers, remains the main question which currently lacks a root cause.

At present, Discovery is enjoying the resolution of a few issues which wouldn’t of stopped the original launch, such as the Main Engine Controller (MEC) problem, which gained the required flight rationale ahead of November 5′s scrubbed attempt.

“OV-103 / SRB BI-144 / RSRM 1 112 / ET-137 (Pad-A):  OV-103 (Discovery) remained powered down over the weekend in support of Panel L-4 R&R (ahead of this week’s power up and retest). Forward Mission Event Timer (MET): The forward MET was replaced last Friday. Retest will follow with power up,” noted the opening NASA Test Director (NTD) report for the week (L2).

“Main Engine Controller circuit breaker: Following replacement off all 18 circuit breakers and certification tests, panel L-4 will be re-installed back in the ship. The panel R-2 circuit breaker checkout was successfully performed last Friday.”

The Ground Umbilical Carrier Plate (GUCP) leak is likely to be the lesser of the two issues with the tank, following NASA’s previous experience with such incidents, and a potential root cause already found via concentricity measurements on the Carrier Plate – mirroring findings via STS-131′s leak.

Engineers have already begun the process of installing the replacement hardware on to the tank, starting with the flight seal, to be followed by the Quick Disconnect (QD) – although the reinstallation is being staged, with Engineering Review Board (ERB) meetings ensuring each element of hardware is fully analyzed prior to rejoining the tank.

“Ground Umbilical Carrier Plate (GUCP) leak: The replacement GUCP was installed on Friday and concentricity measurements recorded were greater than the engineering community believed they should be. The ERB on Friday afternoon gave concurrence to install the flight seal, but not the QD. The flight seal was installed on Friday night.

“In addition, the SN4 ground QD was tested in the lab with nominal results. Body seals were verified installed and no abnormalities were detected visually during disassembly. Another ERB (continues) to discuss the reassembly plan.”

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

The big driver on bringing ET-137 back to flight status is the four cracks observed in the two stringers, found after a crack in the Thermal Protection System (TPS) foam was noticed during detanking after the GUCP leak caused the November 5 scrub.

Four cracks, two on each stringer, were found and are at the center of managerial discussions on the forward plan. The actual repair is already underway on the first stringer to suffer from two cracks, via it’s removal and fabrication of a stringer doubler plate, ready to be installed in its place. The second damaged stringer was also being removed on Monday night.

“LO2/IT stringer crack:  Two cracks have been discovered on the stringer adjacent to and left of the previous cracked stringer. The original cracked stringer has been removed. Additional foam may be removed to continue the evaluation,” added the NTD report.

“The stringer doubler plate for the first cracked stringer was fabricated over the weekend and procedures are being finalized.”

So far, no additional cracks have been found under the foam, raising hopes just the two stringers were affected, a result which was expected due to the stress loads that appear to have been specific to that area of the flange.

Technically, engineers could proceed with a full repair of the area this week, with an environmental enclosure built-up over the weekend to provide the required conditions for the respray of BX foam over the doubler plates, with specialist engineers from the Michoud Assembly Facility (MAF) on site.

However, the main consideration that is being debated by managers is aimed at an assurance the rest of the intertank stringers are free from defects. In order to check the rest of the stringers, managers have been discussing the use of backscatter and x-ray techniques, performed around the circumference of the tank, which is challenging due to the restricted access at the pad.

“Two types of non-destructive evaluation (NDE), high resolution backscatter and computed radiography x-ray, were evaluated and determined to be feasible for use on ET-137 at the pad. Further discussion on these potential data gathering efforts,” noted the NTD report.

According to sources, meetings discussed whether they need to check the entire intertank, or just the orbiter facing side of the tank. Such evaluations are focusing on a scan from the outside of the tank, although requests on the ability to scan from within the intertank itself are also being discussed.

Should all go to plan, with the intertank stringer repair and GUCP reinstallation, a preliminary plan has been created for an extended countdown (S0007 operations), with a Tanking Test embedded into the preparations towards launch.

Such a Tanking Test – as last seen with STS-127 following two GUCP leak scrubs - would provide a large amount of data in the event of additional problems, or indeed a large amount of confidence, should the tanking proceed nominally.

Based on a November 30 launch attempt in the the preliminary S0007 schedule – and elaborated on within a 21 page barchart presentation (L2) of the entire “S0007.200/with Tanking Test”, the countdown would begin on Wednesday, November 24 at 0200 EST, a full six days ahead of the target T-0.

The count would then proceed in a nominal fashion with all the nominal Built In Holds (BIH) and pad operations through the T-6 hour and counting mark, at which point the Mission Management Team (MMT) would execute a full up Tanking Test on ET-137 beginning at 1841 L Friday, November 26, ending at 0011 L Saturday, November 27.

During the Tanking Test, once LH2 and L02 stable replenish have been obtained, the nominal count would deviate with the elimination of Discovery’s cabin configuration and crew ingress activities, with a scrub being declared at the end of the Tanking Test, placing the teams into the execution of a 72-hr scrub turnaround plan inside of the countdown operations.

LH2/L02 drain is expected to be completed within 4.5hrs of the initiation of the 72-hr scrub turnaround; LH2 boil off will be completed by 2000 L November 27 and the vehicle will be configured for the remainder of the S0007 count over the initial 50 hours following the end of the Tanking Test.

The countdown would then be recycled to the T-11 hours and holding mark following the 72hr scrub call, resuming from the T-11 hours mark at 1141 L on Monday, November 29 and proceed in a nominal fashion. ET tanking for launch would then commence at 1841 EST Monday, November 29, all of which targets a T-0 launch time on Tuesday, November 30 of 0401 EST.

UPDATE: A key meeting schedule has been outlined via MOD’s 8th Floor News (L2), noting a joint Shuttle Engineering Review Board (SERB)/Systems Integration Control Board (SICB) meeting that is taking place on Tuesday.

This will be followed by a Program Requirements Control Board (PRCB) meeting, which may be similar to the Special PRCB conducted for the Flow Control Valve  (FCV) issue ahead of STS-119.

The result of the week’s meetings will move forward into the key Launch Status meeting on November 22.

STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/

(Further updates and articles will follow. Refer to live coverage threads linked above. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used, via L2).

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STS-133 Latest:

Discovery was powered up at the pad to provide sampling data, before being put back to sleep, as relatively minor troubleshooting continued on a couple of Interim Problem Reports (IPRs) on the orbiter.

With a replacement Mission Event Timer (MET) being installed on Friday – after one of its digits wasn’t displaying – along with work on the Main Engine Controller (MEC) on ME-3, engineers are taking the opportunity to work on problems that were previously cleared for flight by the Mission Management Team (MMT).

“OV-103 / SRB BI-144 / RSRM 112 / ET-137 (Pad-A): OV-103 (Discovery) was powered up and down this morning to perform FCP H20 sampling. In addition, SRBs and ET/OI were powered up to take data,” noted the NASA Test Director (NTD) report (L2). “IPR 0054 Forward Mission Event Timer (MET): The forward MET will be replaced today.

“IPR 0058 Main Engine Controller C/B (Circuit Breakers): Troubleshooting yesterday revealed no observed large resistance imbalances, but several CB closures revealed noisy signals on phases B and C. Further analysis to come. Panel L4 removal is complete and the panel is being sent to the NSLD. The plan is to reinstall the panel on Monday.”

STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/

Discovery will be re-awakened from her slumber on Monday to provide assistance to the MEC retest, as engineers press forward with what may be a potentially smooth resolution to the Ground Umbilical Carrier Plate (GUCP) leak – with the root cause now pointing to the carrier plate as the culprit for the leak during tanking.

“IPR 0068 Ground Umbilical Carrier Plate (GUCP) leak: Engineering analysis of the data was performed Thursday and the team’s conclusion was that the concentricity measurements of the SN2 Carrier Plate at the 7-8 O’clock position (where the vent line at Pad A tends to pull on the GUCP) were the greatest out of spec measured to date,” added the NTD.

Interestingly, the flight seal has become less of a concern, and despite initial findings pointing to it being “asymmetrically compressed”. This may aid evaluations into the root cause, with only one obvious part of the GUCP hardware being confirmed as out of spec.

“In addition, the NASA Lab also completed the majority of their NDE (Non Destructive Evaluation) analysis of the removed 7” flight seal,” added the NTD report. “There were no abnormalities detected at the lab with respect to the seal.”

With the current findings in hand, managers met on Friday to discuss the forward plan (meeting were ongoing at time of publication, updated to note a go to proceed), one which centers around replacing the suspect carrier plate.
(Click here to see an exclusive super slow mo 8mm movie of the GUCP releasing at launch)

The goal would be to begin the reinstallation of the GUCP hardware to the tank over the weekend, with a further decision on if to conduct a Tanking Test – as was conducted on STS-127′s tank after a second GUCP-related scrub.

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

“The team is ready to begin installation of the SN3 GUCP. An ERB (Engineering Review Board) (will) discuss the initial concentricity measurements of the SN3 GUCP. Based on that discussion, the ERB will either give a go or a no-go to proceed with flight seal and ground QD installation,” the NTD noted.

“The plan remains to have the GUCP R&R complete over the weekend and ready for retest once panel L-4 (related to the MEC) is reinstalled on Monday.”

Following the observation of two cracks on either side of one of ET-137′s stringers – likely responsible for the defect noted in the intertank flange foam shortly after the scrub was called – plans have been drawn up on both access and repair options.

With a plan approved to complete all the required repairs at the pad – thus avoiding what was always an unlikely rollback to the Vehicle Assembly Building (VAB) – engineers decided to install a doubler to the defect area prior to refoaming the areas with BX foam.

“The ET/IT door was removed yesterday (Thursday) in order to get access to the inner-tank for the stringer repair. Equipment is being staged on the -Y platform to start building the enclosure required to support the foaming operations.”

As noted, engineers opened an Intertank access door, allowing them to ingress the tank’s structure – which is located in are area between the LH2 and LOX tanks. At the same time, additional foam was removed from the stringer area, in order to check adjacent stringers for any additional defects.

“IPR 133V-0072 ET LO2/IT stringer crack: Additional foam trimming was performed. Some additional foam trimming will be performed Friday to expose adjacent stringers making sure no additional cracks exist,” the NTD noted on Friday morning.

That proved to be a wise decision, as a third crack was observed on the stringer to the left of the original defects.

The latest crack does not appear to be as “bad” as the other two defects, via hi-res photos acquired by L2 – likely because it has failed to “open out” along the fracture line, potentially pointing to less stress involved when compared to the original two cracks.

Further updates will be added when additional information is forthcoming.

UPDATE 1: GUCP Carrier Plate installation ongoing, requiring two torque operations. Doubler installation ongoing, with set-up for TPS foam spraying operations in work. Flight Seal is installed.

UPDATE 2: Four cracks (in the two stringers) observed. First stringer is removed for R&R. ERB to discuss further foam removal on Monday. Will be a new article later on Monday.

All images via L2 and NASA.

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STS-133 Latest:

Discovery continues to undergoing a dual effort to troubleshoot the two main issues which are restricting her from conducting the final launch of her esteemed career, resulting in a delay to at least November 30. However, making that window is becoming more hopeful, as the chances of rollback appear to remain highly unlikely.

While engineers take advantage of the delay to conduct work on replacing circuit breakers associated with the Main Engine Controller (MEC) on ME-3, regarded as an Unexplained Anomaly (UA) but cleared for flight by the Mission Management Team (MMT), another Interim Problem Report (IPR-54) – relating to a missing digit on the Forward Mission Event Timer (MET) is also being resolved.

“IPR 0058 Main Engine Controller: Panel L4 removal is scheduled to begin Friday morning. Once routed to the NSLD (NASA Shuttle Logistics Depot), 18 circuit breakers will be replaced. L4 is expected to be back by Tuesday, when installation will begin,” noted the NASA Test Director (NTD) report on L2.

“On Wednesday, the ERB (Engineering Review Board) agreed and approved additional troubleshooting on Panel R2. The forward plan minimizes retest and will not create an OMRS (Operational Maintenance Requirements and Specifications) violation/waiver condition and will not require access into the aft. The SCAN retest will be picked up the next time we perform the engine controller checkout.

“IPR 0054: Forward Mission Event Timer (MET): The forward MET will be replaced on Friday.”

STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/

Engineers have found a – or even the – potential root cause for Friday’s scrub, with inspections of the flight seal, which show it to be “asymmetrically compressed”, along with uneven marks on the Quick Disconnect probe. Inspections confirm the condition of the hardware does not match the observations documented when it was installed on the tank inside the Vehicle Assembly Building (VAB).

“IPR 0068: GH2 Ground Umbilical Carrier Plate (GUCP) leak: On Wednesday, the 7” QD was de-mated, the flight seal was inspected and then removed. The Carrier Plate assembly (SN 2) was also removed. The flight seal was found to be asymmetrically compressed. Similarly, an uneven witness mark was identified on the ground QD probe corroborating what was observed on the flight seal,” added the NTD report.

“Concentricity was also measured while the seal was installed to provide a comparison to the measurements taken during initial QD installation in the VAB. Preliminarily, the concentricity measurements seem to indicate that we are less concentric following the leak then when we first had measured concentricity during QD installation in the VAB.

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

Changing out the hardware – centered around a replacement carrier plate and new flight seal could begin as early as Friday, with planning taking place through Thursday to confirm the forward plan.

“The new carrier plate (SN 3) was previously fit checked on ET-137 at MAF and yielded substantially better concentricity values than was obtained with SN 2. SN 2 carrier panel will undergo laser scanner operations and those results will be compared with the SN 3 panel.

“The test/repair team will spend a good majority of the day today pouring over the data collected last night, the new data expected Thursday from the lab on the seals, and the laser scan data on the two carrier panels. The general consensus at this point is to install the SN 3 carrier panel on ET-137. The team hopes to bring a plan together later today that supports re-assembly as early as Friday.”

It is also likely – but unconfirmed – that the forward plan would involve a Tanking Test on the reinstalled GUCP hardware, as was previously seen after the second STS-127 scrub. Managers will use the experience of the STS-127 Tanking Test as the baseline, should they opt to press forward with loading the tank to confirm the leak has been resolved.

“ET Tanking Test Planning: An engineering requirements meeting was kicked off Wednesday. The team performed a quick overview of the expected vehicle/GSE (Ground Support Equipment) configuration baselined from the STS-127 test configuration.

“The team members were given two days to review the configuration, document any additional deltas to that configuration, and review the preliminary copy of the STS-133 Tanking Test OMRS. The second and final requirements meeting will be held Friday. The purpose of this effort is to put KSC into a position to support a tanking test in the event the Program direction is given to perform the test.”

UPDATE: The latest information points to the main problem being with the carrier plate, as opposed to the seal itself.

In support of a Tanking Test – though a nominal pre-launch operation – five tankers are scheduled to arrive Pad 39A to replenish the LH2 storage tank.

Getting to the point of a Tanking Test will depend on the successful repair of the two cracks – and subsequent Thermal Protection System (TPS) foam repair – in the area of the Intertank/LOX tank flange.

Officially characterized as “definitely a result of a structural failure of the stringer“, the cracks are likely to be the contributor to the defect observed in the foam – which has since been removed, in turn revealing the damage in the stringer.

The stringers are manufactured using a lighter weight, stronger material of Aluminum Lithium, which was initially incorporated with the Super Light Weight Tank (SLWT) on ET-96 and first flown on STS-91. While the material is stronger and lighter in weight, it is more brittle and has resulted in increased cases of cracked stringers in the areas noted.

Had Discovery completed a nominal tanking and launched last Friday, analysis shows the intertank would have had sufficient structural capability for the launch and ascent environments with the cracks in a single stringer. NASA also note that although the foam was firmly attached to the damaged structure, it is undesirable to launch in this configuration – a likely reference to the potential threat of foam liberation impacting the orbiter.

The plan to repair the area still concentrates around in-situ work at the pad, allowing engineers to install a second piece of aluminum known as a doubler to the damaged area – as was previously conducted on ET-138 during its production at the Michoud Assembly Facility (MAF).

BX foam then will be sprayed over the newly repaired stringer, requiring approximately four days to cure. However, Friday’s key meeting will decide on the viability of the plan, with previous notes stressing the need for an environment tent/hood to be placed over the worksite, as a condition of spraying foam on to the tank.

“IPR 0072: ET LO2 IT foam crack: During the foam removal, two cracks were found on the stringer on both the left and right side along the fastener points. The cracks are approximate 9″ in length with gap of approximately 0.05″. The foam has been removed, so the full extent of the visible crack has been exposed,” noted the NTD.

“Photos are under review. Engineering review and analysis is in work. Lockheed Martin is developing procedures to repair the cracks at the Pad. ET-138, which is the ET for STS-134, had similar cracks in the stringer and was repaired at MAF by adding a doubler.”

A full update will be forthcoming on Friday via a new article.

(Images via NASA.gov and STS-133′s L2 Coverage)

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STS-133 Latest:

Discovery has completed full safing operations, following last Friday’s scrub, with the disconnection of ordnance on her Solid Rocket Boosters (SRBs) and depressurization of her numerous Composite Overwrap Pressure Vessels (COPVs) used by her Main Propulsion System (MPS) and Reaction Control Systems (RCS).

“MPS/SSME and OMS/RCS COPV Depress: COPV depressurization complete. The 59-1/2 and 28-1/2 doors were removed and the QDs (Quick Disconnects) will be mated,” noted the NASA Test Director (NTD) processing report (L2). “Work to disconnect the SRB ordnance in the forward skirts and the aft IEAs completed.” 

The delay, to an interim launch date of November 30, is focusing on the GUCP troubleshooting, along with the repair to cracks found on the flange area of the ET – between the LOX tank and the Intertank – with work progressing to plan on both issues.

“IPR 68: GH2 Ground Umbilical Carrier Plate (GUCP) leak: The ET/IT Arm was extended and the extendable platform was partially deployed providing access. The GUCP and T-0 lock bolt ordnance disconnects are complete,” added the NTD.

“The team disconnected the QD from the GUCP, recording measurements as they go for engineering analysis once the hardware removal is complete.”

Measurements were taken – with an aim to check for any potential misalignment of the hardware – prior to the removal of the flight seal, the two leading candidates for the gaseous hydrogen leak observed during the fast fill process of Friday’s tanking.

“More GUCP alignment measurements were taken with the vent line lifted and lowered. The measurements are under engineering evaluation. The 7” QD will be de-mated this morning and the flight seal will be inspected and removed,” the NTD added on Wednesday. “Axial and concentricity measurements will also be taken.”

Given the size of the leak is being claimed as the largest engineers have ever seen from the GUCP, it is hoped that an obvious fault will soon be apparent, allowing for a speedy root cause to undergo mitigation.

The other major problem being worked on is the repair on the crack on the flange area of the tank – consisting of one large crack and several smaller, associated cracks – with the aim to confirm engineers can access the area, and then create the required environmental conditions to carry out the reapplication of new foam to the flange.

Access options appear to be positive, with the Engineering Review Board (ERB) giving the go for engineering to carry out the dissection of the damaged foam, which has begun.

“ET LO2 IT foam crack: The ERB concluded that there is adequate access at the Pad on the -Y ET access platform to inspect and repair the crack,” confirmed the NTD. “MAF (Michoud Assembly Facility) will perform NDE (Non Destructive Evaluation and then develop a dissection plan for defect analysis. At this time, the team is not clear exactly when work will be complete.

“Four strips were cut out of the foam for dissection analysis. Engineering is evaluating to determine failure root cause. ET Mechanical will perform an ET LO2 Feedline inspection using the +Y access platform.”

However, once some of the damaged foam was removed from the tank, two cracks were observed on the actual structure of one of the stringers.

Managers are evaluating how serious the defects are, along with a forward plan – which includes the continued effort to bring the tank back to flight status without a rollback.

UPDATE 1: Initial plans noted by NASA include the potential to repair the area via the use of Doublers, which would cover what is now being described as two nine inch cracks in the aluminum, prior to the reapplication of foam.

As of the latest update, managers were set to make a final decision on being able to reapply foam over the dissected area by Friday, potentially utilizing a hood structure over the area in order to provide the environmental needs for the spraying of foam and its stable cure whilst out at the pad.

ET-138, the last “new” tank to be produced by MAF also suffered from a cracked stringer during production, prior to undergoing a repair.

“In cell J.  Had an intertank cracked stringer,” noted a Shuttle Standup/Integration report (L2) a year ago. ”That mechanical repair is complete, less the TPS closeout.”

Further updates will follow.
(Images all from L2′s STS-133 Coverage)

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STS-133 Latest:

Discovery has completed turnaround operations, following Friday’s scrub – caused by a leak from the GUCP, which breached Launch Commit Criteria (LCC), and ultimately pushed STS-133′s launch date out to a NET (No Earlier Than) November 30 target, although the actual launch date remains under evaluation.

Work is set to begin on disconnecting the vent arm, ordnance and connections on the GUCP from Tuesday, which will lead to the removal and examination of the flight seal – one of the leading suspects for the gaseous hydrogen leak. Engineers will also take the opportunity to confirm the correct alignment of the hardware, with a misalignment also one of the likely causes of Friday’s scrub.

In preparation for this task, Discovery was safed and prepared for her extended stay at Pad 39A, with the Rotating Service Structure (RSS) moved to mate, along with the draining of her Power Reactant Storage and Distributation (PRSD) system, along with preparations for the depressurization of the orbiter’s Composite Overwrap Pressure Vessels (COPV).

An External Platform (ESP) has also been raised around the Space Shuttle Main Engines (SSMEs), which would allow for an opportunity to take a closer look at ME-3′s Main Engine Controller (MEC) during the delay.

“OV-103 / SRB BI-144 / RSRM 112 / ET-137 (Pad-A): Significant Processing Operations: ET drain and boiloff is completed. RSS has been moved to mate position, Orbiter Weather Protection is extended. SSME ESP is in place but the SRB (Solid Rocket Booster) ESPs remain lowered,” noted the NASA Test Director (NTD) processing report (L2).

“PRSD commodities were drained and systems secured. Ordnance remains connected but is planned for safing on Wednesday morning. Hyper system COPV tanks remain pressurized so the Pad is open for scheduled work items only. MPS (Main Propulsion System) COPV tanks are vented to nominal pressure.”

STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/

Two presentations (L2) were created for review on Monday, ahead of the GUCP work, referencing the testing facility that is likely to play a role in the mitigation process, which noted encouraging test results prior to STS-133′s scrub, when changing (increasing) the purge flowrate to reduce hydrogen concentrations during the next tanking.

There are also notes of “Significant GUCP movement” during the STS-133 leak, suggesting something was seriously wrong with the hardware during tanking (an article will be forthcoming).

“IPR-68: Engineering is working an effort to review the fault tree from previous investigations while preserving the evidence of the hardware. An ERB this morning is anticipated to establish the initial steps in troubleshooting the problem with work to start tomorrow (Tuesday),” added the NTD report.

For all NASASpaceflight.com articles related to the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

Foam Cracks:

However, the crack on the LO2 intertank flange area of Discovery’s tank is also a large driver for the get-well plan to allow STS-133 to return to a launch posture.

“IPR-72: During the drain operations a large crack was observed on a closeout area of the External Tank. The issue developed during the de-tanking operation and was inspected on Saturday,” noted the NTD.

“Engineering took measurements and recorded observations of the area. The evaluation effort is (continuing) with discussions centering on repair options available while at the pad.”

The crack was overviewed on Monday morning by the KSC Engineering Review Board (ERB), noting the time the crack appeared and the opening forward plan.

The initial goal centers around TerraHertz and BackScatter scans of the crack in the tank’s Thermal Protection System (TPS) foam, prior to dissecting the area.

“The crack appeared at 7:08 am EDT, which was a few minutes prior to the initiation of the GUCP LH2 leak. A plan to dissect the defective area will begin no earlier than Wednesday morning,” noted ERB notes (L2).

“Non-Destructive Evaluation (NDE) using TerraHertz and BackScatter equipment will be performed in parallel to the dissection plan to determine if there is any metal substrate damage that may have caused the TPS defect to form. Access to this area is difficult, but an access platform will allow the work, described above, to occur.”

A decision on the ability to repair the tank at the pad will be made by the end of the week, with the main considerations relating to the environmental conditions required for the new foam to be sprayed on to the tank, along with the cure period once applicated.

It has already been suggested that a plan involving a hood structure – located around access platforms – would need to be devised to provide such acceptable conditions.

“On Friday, after the dissection/NDE data has been collected, the teams are expected to reconvene to determine if the ET can be repaired at the pad.  Environmental conditions, such as temperature and humidity levels, must be controlled to allow a ‘spray-in-place’ plan to occur,” added the ERB notes.

“Some sort of ‘hood’ structure would have to be built around the ET/access platform to provide this environmental control. The KSC team is also working to develop a preliminary TPS R&R schedule.”

Further information is listed in a presentation, created on Monday and acquired by L2, which notes the crack is on Station Location Xt-862 and is surrounded by several other cracks.

“During STS-133 Post Drain walkdown a large crack/divot was observed in the LO2-I/T Flange TPS closeout. Location – Xt-862, +Z/-Y Quadrant – PHI angle -51deg. Timing – occurred at ~0708 hrs Local (captured by camera OTV 041),” noted the presentation.

It was also confirmed that there wasn’t any visual evidence of a foam anomaly via the photography taken of the tank before it left the Vehicle Assembly Building (VAB) – a total of three photography runs.

Engineers will likely work a modified plan to access this area of the tank, based on the pull-plug tests that were called for after a number of foam liberations from the intertank stringers several flights ago.

The pull tests have successfully added confidence that the intertank foam has the required adhesive properties to stop the foam from liberating during ascent.

“Closest Access: (Based on Intertank Foam Bond Adhesion Check): Scaffolding access to -Y “trapezoid” (high risk) areas – no reach. Stow position of -Y Pad Access Platform – adjacent,” the presentation added.

Once the issue of access has been mitigated, an opening plan to dissect the damaged foam has already been presented by the Michoud Assembly Facility (MAF) in New Orleans, who will have a Kennedy team already on station to provide support for the three final tanks – ET-137, ET-138 and ET-122 – which are all now located in Florida.

“MAF developing a Dissection Plan for defect analysis. Cut/excavate loose TPS in horizontal sections along gridlines. Document condition of separation plane (e.g., knitline debond, thin fuzzy film, etc.). Sample any exposed primed substrate for contaminants. Perform offline dissection analysis of removed sections.”

Meetings will continue through Tuesday, focusing on access, TerraHertz and BackScatter NDE scans, and refinements to the repair plan ahead of Friday’s decision on if they will be able to proceed with the repair at the pad.

(Follow L2′s STS-133 Special for up-to-the-minute engineering updates, and the forum’s STS-133 troubleshooting thread. All images via L2 presentations).

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