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/)

No related posts.

Highlighting the second half of 2009 for NASA was the resolution of the Gaseous Hydrogen leaks at the Ground Umbilical Carrier Plate on the Shuttle launch pad (which resulted in the successful launch of STS-127/Endeavour in July), the midnight ride of Discovery on STS-128 in August, the amazingly successful test flight of the Ares I-X rocket in October, the discovery of water on the moon in October/November from the Lunar CRater Observation and Sensing Satellite and the Lunar Reconnaissance Orbiter, and the logistics run of shuttle Atlantis to the ISS in November.

*See also 2009 Review Part 1*

The Gaseous Hydrogen Leaks and the STS-127 – LRO/LCROSS Range Debate:

Kicking off the second half of 2009 for NASA were the launch campaigns for shuttle Endeavour’s STS-127 mission to deliver the Japanese exposed experiment facility to the ISS and the Lunar Reconnaissance Orbiter (LRO) and shepherding spacecraft Lunar CRater Observation and Sensing Satellite (LCROSS) on the Atlas V rocket.

Initially targeting a June 13 liftoff for STS-127, the main constraints facing NASA for Endeavour’s launch window were the scheduled June 17 launch of the LRO/LCROSS mission – a mission which only had a 3-day launch window before standing down until early July – and an imposing Solar Beta Angle Cutout with the ISS that began on June 20 and ran through July 10.

Given the Eastern Range’s need of roughly 48-hours to reconfigure all their tracking and communication equipment between the various vehicles launched from the Cape Canaveral area, Endeavour was constrained to a 3-day launch window in the early morning hours of June 13, 14, and 15 in order to allow LRO/LCROSS to launch on June 17.

This plan was thwarted, however, in the evening hours of June 12 as launch personnel were nearly finished fueling Endeavour’s External Tank (ET) with over 500,000 gallons of Liquid Oxygen (LOX) and Liquid Hydrogen (LH2).

Just before the LH2 tank of the ET entered stable replenish mode, launch personnel noted an abnormally high concentration of gaseous hydrogen around the Ground Umbilical Carrier Plate (GUCP) assembly – a system used to vent the extremely flammable gaseous hydrogen (caused by LH2 boil off inside the LH2 tank) safely away from the Shuttle stack.

Following the scrub of Endeavour’s first launch attempt, NASA mangers reported that the signature of the leak was “nearly identical” to the leak seen during the first launch attempt of STS-119 in March. Since the Removal and Replacement (R&R) of the GUCP Quick Disconnect seals fixed the leak back in March, NASA managers decided to repeat the R&R procedure after obtaining critical data on the area of the leak for a root cause investigation.

However, the R&R of the seals meant that launch of Endeavour would not be possible until the early morning hours of June 17 – two days past the end of Endeavour’s launch window because of the Eastern Range launch conflict with the scheduled June 17 launch of LRO/LCROSS.

Nonetheless, engineers pressed forward with the R&R of the GUCP Quick Disconnect seals while the Agency as a whole began discussions on which mission now had priority.

Ultimately, through cooperation between the Space Shuttle Program, the LRO/LCROSS team, and the Eastern Range, a compromise was reached in which Endeavour would be given a launch opportunity at 5:40a.m. on June 17 while the LRO/LCROSS team would proceed toward a late afternoon/early evening June 18 launch with the understanding that if Endeavour launched on June 17, LRO/LCROSS would have to be delayed until June 19 – the last day of the LRO/LCROSS’ June launch window – because of Eastern Range reconfiguration time constraints.

Per the terms of the agreement, should Endeavour launch on June 17, LRO/LCROSS would take an additional one day delay and launch on June 19. However, should Endeavour scrub for any reason prior to 12 midnight June 17 (a scrub on calendar day June 16), the Eastern Range would undertake a 36-hour reconfiguration effort to allow LRO/LCROSS to maintain its ~5p.m. June 18 launch date/time.

As it would be, the GUCP leak reoccurred during ET fueling on June 16/17 and the launch was officially scrubbed at 1:55a.m. EDT. Later, Shuttle Program managers stated that they would not try to launch Endeavour before July 11 to allow for an investigation into the GUCP leaks.

However, the scrub came nearly two hours after the midnight deadline for LRO/LCROSS on June 18. Nonetheless, the Eastern Range undertook the reconfiguration effort and completed these operations on time for the June 18 launch of LRO/LCROSS. That day, during the final minute of the launch window, the Atlas V rocket carrying LRO/LCROSS lifted off from its seaside launch pad, returning NASA to the moon.

In the days that followed the second scrub of STS-127, engineers focused their attention on a minor misalignment between the GUCP and the External Tank Carrier Assembly (ETCA), the component on the ET to which the GUCP is mated.

In the end, the ETCA was realigned using high fidelity 0.515″ alignment pins and the Flight Seal in the GUCP was replaced.

Once the R&R procedure was complete, a tanking test was performed on July 1 to verify the integrity of the repair and confirm that no leaks were present. The tanking test was a success and no leaks were detected.

This paved the way for the July 11 launch attempt of Endeavour, which was postponed prior to fueling because of extra time needed to clear all of Endeavour’s systems following a lightening strike within the Pad-A perimeter the previous day.

Launch was rescheduled for July 12 but was scrubbed at the T-9 minute and holding mark due to unacceptable weather around the Kennedy Space Center. The launch was further scrubbed on July 13 – again at the T-9 minute and holding mark – due to adverse weather.

NASA stood down on July 14 to replace the Tyvek covers on Endeavour’s Reaction Control System jets and retargeted launch for July 15. The countdown on July 15 was uneventful and at 18:03:10 EDT (6:03:10p.m.) Endeavour lifted off from Pad 39A – on the third Shuttle mission of the year – one day shy of the 40th anniversary of the Apollo 11 launch from the same pad.

In all, STS-127 was the longest Shuttle flight of 2009 lasting nearly 16-days. During the course of the mission, Chris Cassidy became the 500th person to fly into space, a record 13 people lived and worked on the ISS during Endeavour’s docked mission (thanks to the increase of the permanent ISS crew from three people to six people at the end of May 2009), five EVAs (spacewalks) were performed, the Japanese experiment exposure facility was installed to the Japanese Kibo module, and six P6 truss batteries were R&R on the ISS.

Endeavour and her seven member international crew landing safely at the Kennedy Space Center at 10:48a.m. EDT on July 31st on the mission’s first landing opportunity, completing a 15day 16hour 44minute 58second flight.

STS-128 – ET Foam Loss Investigation and PV-12 Fill and Drain Valve Discussion:

With the successful completion of STS-127, attention turned to the next Shuttle mission: the STS-128 logistics flight of Discovery scheduled for late-August.

STS-128′s ground processing flow proved to be extremely interesting, with engineers working through issues with a Solid Rocket Booster Check Valve Filter Assembly, an ET Ice Frost Ramp foam void indication, a Main Bus Controller anomaly, and an Ordnance Cable issue on the ET Vent Arm System.

However, it was the numerous foam liberations from the Intertank region on Endeavour’s External Tank during her July 15 launch that kick started an investigation into why the foam liberated – an investigation that once again highlighted NASA’s strict standards of safety when it comes to the Space Shuttle fleet.

While plug pull tests on Intertank foam from Discovery’s ET confirmed the integrity of the foam bond to that tank, NASA managers demanded that they have all the information possible before clearing Discovery for flight.

In fact, the standard one day Space Operations Mission Director (SOMD) Flight Readiness Review (FRR) at the Kennedy Space Center – the FRR that formally approves each mission for launch – required an additional half day to complete all the necessary discussions.

As such, the possible root cause scenarios for the foam loss coupled with the extremely positive results from over 100 plug pull tests on the backside of the Intertank region on Discovery’s ET gave NASA managers the confidence needed to proceed with launch.

In the end, Discovery was approved for liftoff on August 25 at 1:36a.m. EDT. The countdown was uneventful from a technical perspective; however, heavy rains and lightening over the launch pad and in the KSC area resulted in a scrub of the August 25 attempt at the T-9minute and holding mark.

Launch was reset for the following day. Nonetheless, during fueling operations of the External Tank, the inboard LH2 PV-12 fill and drain valve on Discovery did not close when it was commanded to do so.

Launch Director Pete Nickolenko followed the Launch Commit Criteria (LCC) to the letter, calling a scrub and ordering the draining of Discovery’s ET.

For a stuck “open” fill and drain valve, LCC prevent launch personnel from attempting to cycle the valve under cryogenic conditions (meaning in the presence of Liquid Hydrogen or Oxygen). The theory behind this LCC is that – if there is a serious problem with the fill and drain valve – the launch team does not want to put themselves into a situation where they cycle the fill and drain valve closed and then cannot get it open again.

While the launch team followed these procedures to the letter, there were indications from sensors – both upstream and downstream of the PV-12 fill and drain valve – that the valve had indeed closed when commanded, and that the “open” indication was a sensor error in the valve itself.

As such, engineers conducted multiple ambient (meaning without the presense of Liquid Hydrogen) cycles of the valve. During these tests, the valve performed nominally.

This allowed Shuttle mangers to approve a third launch attempt for Discovery 22-minutes after midnight on Friday, August 28 while they reviewed a potential revision to the current LCC document (actually a reversion to a previous LCC rule) that would allow them to cycle the PV-12 valve under cryogenic conditions should they receive a sensor indication that the valve failed to close on the Friday morning attempt.

Nonetheless, extensive engineering conversations took place in regard to this LCC change and the possible scenarios that could occur if they launched with a PV-12 valve that was only partially closed or a valve the became stuck “closed.”

“Based on a concern with galling failure mode within the valve driver mechanism, the previous LCC was amended to preclude valve cycling under cryo conditions,” noted a NASA processing report on the engineering analyses.

“Previous LCC allowed for a repeat valve cycle attempt given the following conditions were met: No Sustained reg-out demand occurs. No sustained increase in Aft Haz Gas helium concentration. Initial move time <5.0 seconds. All the above parameters were satisfied.”

In the end, NASA managers decided they needed additional time to review all the information and complete closeout paperwork on the PV-12 valve issue. To this end, launch of STS-128 was postponed 24-hours to 23:59 EDT (11:59p.m.) on Friday, August 28 – the second launch opportunity of the calendar day but technically a 24-hour delay to the launch.

The final countdown on August 28 was uneventful and the PV-12 valve “closed” when it was commanded to do so.

In fact, the countdown went exactly as expected and at 11:59:37p.m. on August 28 Space Shuttle Discovery lit up the midnight sky of Central Florida, becoming the only manned mission to launch on one calendar day and reach orbit on the next.

Two days later, Discovery docked to the International Space Station 25 years to the day after the launch of her maiden voyage: STS-41D. That day, Nicole Stott – who launched on Discovery – officially transferred to the ISS crew, becoming the final person to rotate up to the ISS on the Space Shuttle.

During the course of the docked mission, Discovery’s crew delivered a second treadmill to the ISS as well as numerous new science experiments and new science racks via the Multi-Purpose Logistic Module Leonardo.

After a highly successful mission, Discovery and her crew undocked from the ISS and received final Thermal Protection System clearance for landing. The first two landing attempts on September 10 were waved off due to bad weather at the Kennedy Space Center.

Discovery was ultimately cleared for landing on September 11 and performed the second Boundary Layer Transition DTO (Detailed Test Objective) during her reentry into the Earth’s atmosphere.

Discovery and her seven member crew landed safety at Edwards Air Force Base, CA at 20:53 EDT (8:53p.m.) on September 11, completing a 13day 20hour 54minute 55second mission.

Ares I-X – Proving Concepts for the Future of Manned Space Exploration:

It was a mission nearly 4-years in the making. The Vision of Space Exploration, set forth by President George W. Bush in January 2004, committed NASA to returning men to the moon and continuing on to Mars – an endeavor that required a new launch architecture system.

Unlike the Space Shuttle, which underwent its first integrated test flight with a crew onboard, NASA’s new Ares I crew transportation rocket was designed to have multiple test flights before launching a crew into orbit.

The first of these test flights was dubbed Ares I-X.

The rocket, a virtually identical model of the Ares I vehicle, was designed to test the avionics and control systems of the Ares rocket during the first stage of flight – a two minute propulsion period powered only by a single Solid Rocket Booster (SRB).

As the Ares I design evolved, the SRB grew from a four-segment SRB (as used on the Space Shuttle) to a five-segment SRB. The addition of a fifth segment to the SRB required changes to the SRB’s nozzle, changes that could not be implemented into the design of the Ares I-X test rocket in time for all the data the test flight was meant to gain to be useful to Ares I engineers.

Since the Ares I-X test was meant to demonstrate the ability and performance of the Ares I design, not simulate a full up 5-segment SRB thrust test – a fifth segment simulator was added to Ares I-X to give the rocket the appropriate height and to accurately simulate the airflow over the entire length of the vehicle during the 2-minute powered portion of the flight.

Receiving and integration of the Ares I-X’s Upper Stage Simulator began in early 2009 on the floor of VAB High Bay 4, with full up stacking of the vehicle (SRB and all) beginning in July in High Bay 3 – directly across from High Bay 4.

After stacking of the vehicle was complete in mid-August, nearly two months of integration testing and sensor diagnostics took place, ensuring that over 700 sensors and the avionics and control assemblies of the Ares I-X vehicle were working perfectly.

Then, one week after Shuttle Atlantis/STS-129 was rolled out to Pad-A, the Ares I-X vehicle emerged from the VAB in the early morning hours of October 20 – marking the first time since 1975 that a vehicle other than the Space Shuttle was rolled out of the VAB.

One week of launch pad operations and processing followed for Ares I-X – a timeframe that was increased from the original four day pad flow to accommodate the dual pad flow nature of I-X processing with the ongoing processing of Space Shuttle Atlantis on nearby Pad-A.

In fact, Ares I-X shared many of the pad workers who were also busy processing Shuttle Atlantis for STS-129 in November. As a result, these workers undertook the second dual pad flow of 2009 – accomplishing both flows in time for Ares I-X’s and Atlantis’ respective launch windows.

With the countdown beginning at 1a.m. on October 27 for a launch window of 8a.m. through 12p.m., the Ares I-X launch team configured the vehicle and, after waiting out the weather and a cargo ship in the SRB recovery zone, gave the go to resume the countdown and launch Ares I-X.

The countdown resumed from the T-4 minute and holding mark and counted down to T-2minutes 39-seconds – at which point Ares I-X weather officer Kathy Winters ordered a hold due to a violation of the triboelectrification weather rule.

The resulting hold mandated a recycle of the countdown to the T-4 minute and holding mark, a milestone that was accomplished in a timely manner. The launch team then waited on the weather, before eventually scrubbing the October 27 launch attempt and announcing that a second launch attempt would be made on October 28.

On the morning of October 28, the countdown once again began at 1.a.m. EDT for an 8a.m. through 12-noon launch window. During the course of the morning, the T0 time was continuously realigned to reflect changing weather conditions.

Finally, a go was given by the launch team to proceed with launch at 11:30a.m. EDT – in the center of a patch of good weather.

The countdown resumed at 11:26a.m. and proceeded without issue. At 11:30a.m. on the nose, the Ares I-X’s SRB ignited, propelling the vehicle off of Launch Pad 39B and off onto a due east trajectory from the Kennedy Space Center.

Two minutes later, the SRB burned out and successfully separated from the Upper Stage Simulator, parachuting into the Atlantic Ocean 130 nautical miles east of KSC.

Ares I-X managers and NASA hailed the test flight a smashing success. All five the flight’s primary test objectives were accomplished, giving NASA invaluable data on the performance of a single SRB first stage powered launch vehicle.

Despite the uncertain nature of the Ares I rocket’s role in whatever the future of NASA’s manned space endeavors becomes, the test flight of Ares I-X proved the concept of the Ares I first stage design and provided the engineering community with copious amounts of scientific data that can be used in the development of future U.S. launch vehicles.

Water on the Moon! – LRO and LCROSS’s Enormous Discovery:

On October 9, the LCROSS satellite and its Centaur Upper Stage impacted the moon’s south pole in the Cabeus crater. Their mission was to expose the unseen material beneath the surface of the Cabeus crater – looking for signs of water, of the past presence of water, beneath the moon’s surface.

Trailing its Centaur upper stage by four minutes, the LCROSS conducted hundreds of scientific observations of the ejecta plume created by Centaur’s impact before it too impacted the Cabeus crater, creating a second ejecta plume of denser material for analysis by the Hubble Space Telescope and Lunar Reconnaissance Orbiter.

On November 13, the preliminary results of the impacts were released by NASA, and the answer to the age old question of whether water currently exists on other bodies in our solar system was finally put to rest.

The answer was a resounding yes. Water exists in the permanently shadowed crater Cabeus on the moon’s southern pole.

“We’re unlocking the mysteries of our nearest neighbor and by extension the solar system. It turns out the moon harbors many secrets, and LCROSS has added a new layer to our understanding,” said Michael Wargo, chief lunar scientist at NASA Headquarters in Washington D.C.

In fact, the LCROSS results have shed light on the mystery surrounding the large concentrations of hydrogen observed on the moon in the past decade. Given the current evidence, NASA suspects that water may be far more prevalent and exist in much larger quantities on the moon than originally theorized.

But just how much water is on the moon is still unknown. “Multiple lines of evidence show water was present in both the high angle vapor plume and the ejecta curtain created by the LCROSS Centaur impact,” stated Anthony Colaprete, LCROSS project scientist and principal investigator at NASA’s Ames Research Center in Moffett Field, California. “The concentration and distribution of water and other substances requires further analysis, but it is safe to say Cabeus holds water.”

The results of the LCROSS experiment hold significant implications for the current NASA plan to establish a permanent, manned colony near one of the moon’s poles. If water is present in large quantities beneath the moon’s surface, future inhabitants of a lunar colony could make use of that water, providing valuable lessons on how to use natural materials/substances around the colony – lessons that could be applied to future manned missions into the solar system.

STS-129 – Stockpiling the Space Station:

Continuing on the theme of preparing for the future, 2009 came to a close for NASA with the highly successful flight of Space Shuttle Atlantis on the STS-129 mission.

After initial worries and conversations about range conflicts with an Atlas V and Delta IV rockets, both vehicles encountered launch delays – giving Atlantis the full duration of her short launch window in mid-November, a launch window that was constrained by a Solar Beta Angle Cutout from November 20 – December 5.

Officially approved for a launch on November 16, Atlantis’ processing teams saw double work with the dual pad flow of Atlantis and Ares I-X. After the successful launch of Ares I-X, work proceeded in earnest on Atlantis with installation of the Express Logistics Carriers (ELCs) -1 & -2 into Atlantis’ payload bay as Program engineers and managers worked through a Main Engine Ignition (MEI) overpressure issue.

The issue, relating to the acoustic environment present at the aft of the vehicle during SSME (Space Shuttle Main Engine) ignition was brought to the attention of Program managers when it was discovered that bolts used to attach the aft stinger pods to the OMS Pods might not be sufficient to counter the acoustic environment.

Through an aggressive engineering review of all information pertaining to the MEI acoustic environment and the stinger pod bolts, Program managers were able to clear Atlantis for flight after installation of several new sensors on Atlantis and the Mobile Launch Platform to obtain as much data as possible during the vehicle’s launch.

With launch officially approved, Atlantis’ countdown began on Friday, November 13 at 13:00 EST (1p.m. EST) for a targeted 14:28 EST (2:28p.m.) liftoff on November 16.

Atlantis’ countdown was uneventful and – with the lowest number of PRs (Problem Reports) in the history of the Shuttle Program – STS-129 lifted off at 14:28:09 EST November 16 on its first launch attempt, making Atlantis the only Orbiter to launch on her first attempt for both of her 2009 missions.

After docking with the ISS, Atlantis’ six member crew installed both ELCs onto the Integrated Truss Structure of the Space Station – thereby delivering nearly 30,000 lbs of spare parts that will enable the ISS to remain operational well into the next decade.

Three EVAs were also performed on STS-129 and Nicolle Stott transferred to the Atlantis crew before orbiter undocked from the ISS the day before the Thanksgiving holiday in the U.S.

After performing the customary late inspection of their vehicle’s Thermal Protection System (TPS), Atlantis’ crew enjoyed Thanksgiving on orbit before receiving final TPS clearance to land.

On Friday, November 27, Atlantis and her now seven member crew glided to a perfect landing at the Kennedy Space Center at 9:44:22a.m. EST, completing a 4.4 million mile mission in 10days 19hours 16minutes and 13seconds.

In all 2009 was a year of tremendous accomplishments for NASA and its dedicated workforce.

As Mike Moses, KSC Launch Integration Manager, stated “this was really about the teams and their ability to go above and beyond what we asked of them. When you think about the fact that we worked through the Flow Control Valve issue, the hydrogen leaks, and many more things and still flew five successful Shuttle missions, had two dual pad flows (three if you count the first STS-125/STS-400 flow last year), launched an experimental rocket, and mated Endeavour for STS-130 next year – all within one calendar year – that’s pretty amazing.

“It really shows the level of dedication of the teams out here and their ability to remain flexible.”

For a video review of NASA outstanding year, see Max-Q Entertainment’s Year In Review video click here

For NASA, 2010 begins with preparations and Flight Readiness Reviews for Space Shuttle Endeavour’s STS-130 mission, currently targeted to launch at 4:39a.m. on February 7.

No related posts.

STS-130:

The ever-reliable SSMEs are recycled and reused for numerous missions, with engine 2047 – for example – set for a 14th flight with Atlantis on STS-132, following its successful flight with Discovery on the recent STS-128 mission.

With the SSMEs are already installed on Atlantis for the STS-129 mission in November, the upcoming engine milestone relates to STS-130 with Endeavour – which will actually include a first flight engine (SSME 2061), after it became the final engine to be delivered to the Kennedy Space Center (KSC) at the end of last year.

The engine has already had an eventful life, after testing found the Fuel Preburner FG1a elliptical ring was observed to be cracking, following an acceptance test. The FG1a elliptical ring provides access to fuel preburner (FPB) and HPFTP (High Pressure Fuel Turbopump) turbine for post hot fire borescope inspections.

“Cracking of elliptical ring, weld and/or liner is not uncommon,” explained the documentation presented to a recent Flight Readiness Review (FRR). “Borescope inspection of ring and weld required post every hot fire.

“Rules limit life of FPB liner and ring to 24,224 seconds with pump out visual inspection of ring at 6,056 second intervals. Erosion, pitting and/or cracking is unacceptable and results in liner and ring replacement.

“Concern is loss of piece greater than critical impact mass (0.142 g). No significant loss of mass experienced in program history. Multiple cracks required to liberate a particle of significant size.”

Also adding confidence was the overall test result for engine 2061, which was deemed to be ‘in family’ for its requirements. The HPFTP was replaced to ensure the engine is ready to fly.

“Engine 2061 Assessment: Detailed post test inspections noted no other hardware anomalies. Engine performance (temps, pressures, flow rates, speeds, etc.) and measured dynamics all as expected and ‘in family’,” confirmed the FRR presentation.

The reason cracks warrant an extensive evaluation is due to the threat of FOD (Foreign Object Debris) which would be a serious problem, should a crack liberate FOD into the super fast spinning turbine blades. However, such is the safety record of the SSMEs during flight and testing, a probability of that threat being realized is a staggering 1 in every 150,000 flights.

This engine will become engine number 2 on Endeavour for STS-130, joining SSMEs 2059 and 2057 – which are flying on their fourth and fifth flights respectively – although Thermal Protection System (TPS) work on engine 2 is being conducted ahead of its installation.

“SSME (Pratt & Whitney Rocketdyne/KSC): The next major milestone is engine installation on October 19, STS-130. Have allocated engines 2057, 2059, and 2061,” noted information on the latest Shuttle Standup/Integration report on L2.

“In the engine shop, 2057 and 2059 are in walkdowns so they are through all their major milestones. Engine 2061 is through the major milestones, but need time to put the nozzle TPS on since that was a brand new nozzle and was hot-fired without any TPS.

“It will take 3+ weeks to finish the TPS on 2061, but are targeting to have that engine ready for October 19.”

STS-127 SSME 1 Nozzle Update:

The failure investigation team – set up to evaluate why STS-127′s SSME number 1′s nozzle was found to have hundreds of small leaks post-flight – have revealed the leading candidate root cause.

“During the post-flight work of STS-127/2JA, while performing nozzle tube leak checks, Engine 1 (SN 2045) had 340 tube leaks,” noted an update on the latest Shuttle Standup/Integration report on L2.

“The total result for H2 loss is fairly small, as these are pinhole leaks. Four areas in the nozzle were sectioned and sent to Canoga Park for evaluation. The mechanism driving the corrosion is understood.”

The problem was caused by the sulfur contained in the adhesive tape that is applied to the throat plug area of the engine nozzle. The sulfur has been found to interact with the nozzle’s nickel finish under the extreme temperatures endured during their ascent role, causing embrittlement and then tiny cracks and corrosion of the A286 iron which the SSME nozzle tubes are made from.

Corrosion was already noted on the engines ahead of Endeavour’s flight, although engineers thought they had found the nozzle to be in good shape after the rust-like substance was cleaned from the hardware.

“The problem stems from the application of Tacky Tape to seal the throat plug during the 1990′s. The tape adhesive contained sulfur, and when this interacted with the nickel finish of the nozzle at temperatures in excess of 1000 degrees Fahrenheit, it embrittled the nickel, causing cracks,” added the Standup report.

“These cracks, in turn, allowed moisture to enter and attack the A286, resulting in the corrosion and pitting.

“In 1999, cylohexane was used to clean the sulfur residue, but the nickel finish was already compromised. To combat this problem, a corrosion inhibitor and clear-coat finish was applied. The Tacky Tape was originally applied 3-6” below G15, with the corrosion inhibitor and clear-coat applied 1-8” below G15 to fully cover the area.

“The 340 leaks that were discovered appear to have the same mechanism (crack through the nickel caused by embrittlement, followed by pinhole corrosion pits that caused the leak).”

The 340 leaks on SSME 1 was not a critical issue, as the combined leakage from the pinhole cracks was well below that of – for example – STS-93′s eventful ascent.

Endeavour suffered no ill effects from the leakage during her ascent, while Discovery is also believed to have suffered from leaks during STS-128′s ascent – though far less than STS-127 – and again the engine performance has been deemed as nominal.

A forward plan is being worked by engineers, which may include pumping dry air into the nozzles in order to protect the hardware from the Florida humidity.

“The Failure Investigation Team will meet to discuss actions that could be taken to protect the nozzle hotwall surface when it is outside of a controlled environment,” added the Standup report. “This could include plumbing dry air or N2 into the nozzle cavity, using some additional close-out covers like those used during rollout to protect from the warm, humid Florida air that attacks the A286.”

The damaged nozzle has now been removed from the SSME and will be substituted by a flight spare. The nozzle will be sent back to Canoga Park for either a repair or scrapping.

“From a total asset point, there are 16 nozzles at KSC – but 12 have been exposed to the Tacky Tape. These were treated with the corrosion inhibitor and clear coat. On engine SN2045 with nozzle unit 2031, the nozzle has been separated from the power head and the spare nozzle unit 4026 will be used to return the engine to the processing cycle.

“Nozzle 2031 will be shipped from KSC, because the amount of work required to repair the 340 leaks exceeds what the shop is capable of doing.

“Will cut a few more tube samples from the nozzle from STS-127 that had the 340 leaks, and get those back into the lab. Once get good lab data from those samples, the plan is to ship that nozzle back to Canoga Park to start either additional investigation or repair of those tube leaks.”

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

No related posts.

Endeavour/STS-130 Latest:

Following her STS-127 mission, Endeavour has been in processing inside Orbiter Processing Facility 2 (OPF) for the February 4, 2010 flight to carry Node 3 and Cupola to the International Space Station (ISS).

This week has seen work being conducted on replacing Fuel Cell 3 – which will be completed after the holiday weekend – and reinstalling her Orbiter Boom Sensor System (OBSS)

“Orbiter: OV-105 (OPF Bay 2): Fwd Sep Pyro Harness Installation was completed yesterday. APU (Auxiliary Power Unit) catch bottle drain SCAPE operation was completed this morning,” noted Friday processing information on L2.

“Fuel Cell hydrogen separator R&R work continues and should complete today. Fuel Cell 3 R&R work picked up yesterday with mechanical de-mates and the removal of the replacement fuel cell from its shipping container.

“Electrical de-mates are scheduled for today, and the R&R is scheduled for (next) Tuesday. OBSS installation into the Orbiter is scheduled for today.

SSME 1 Leaks:

As part of the normal processing flow, all three SSMEs were recently removed from Endeavour, ready for their turnaround on a future flight. However, one engine will require a new nozzle – following inspections.

“Were working post STS-127 Engine inspections in the engine shop. On Engine #1 (2045), got into nozzle tube leak checks,” noted the first memo on the observations (L2). “Ended up with over 100 leaks on the hot wall side of that nozzle.”

This engine (2045) is set for turnaround in order to be ready to fly with Discovery on STS-131 next year. It is also designated as being on standby for installation on Atlantis for STS-335 – the Launch On Need (LON) mission in support of STS-133, which is currently the final mission on the shuttle manifest.

The memo confirmed the engine in question was the SSME that required specialist cleaning ahead of STS-127, when a brown – rust-like – contamination was observed on the nozzle out at the pad.

“Corrosion/contamination has been noted on two SSME nozzles at Pad A for STS-127 (engines 1 and 3). ME2045 (Main Engine) has a significant amount in the first few inches downstream of the MCC/nozzle interface joint G15, and ME2054 has a minor amount approximately 10 inches below G15,” noted a pad flow report ahead of STS-127.

“Completed polishing. During normal nozzle inspection, identified two issues: engine 1 and 3 have some corrosion at G15 area. It looks unusual, and have asked corrosion expert from Canoga Park to look at it.”

Those experts deemed the engine to be in good shape, confirmed by successful leak checks at the pad.

The SSME nozzle tubes are made of A286 iron based steel and are nickel plated primarily to make the brazing of the tubes to operate nominally. It is deemed to be completely normal for these tubes to rust in the Florida coastal pad environment. However, the tubes – which are put under 6000 psig pressure during engine operation – are at risk of rupturing if corrosion has reduced their integrity.

An example of tube damage on the SSME nozzles was seen during STS-93’s infamous launch, where three tubes were damaged by a blown injector pin, leading to the engine controller assuming more hydrogen was being burned and compensated by injecting additional LOX – ultimately resulting in the ECO (Engine Cut Off) sensors shutting down the engines slightly ahead of time, leading to an underspeed at MECO (Main Engine Cut Off).

While Columbia’s engine only suffered from three punctures on her SSME during STS-93, a tube split or rupture would be a more serious event. **Click here for clips from the L2 STS-93 Internal Loop Video of Columbia’s ascent**

How close Endeavour’s number one engine came to suffering a major problem is unknown, with no performance issues noted in the post flight IFA (In Flight Anomaly) review on the SSMEs. However, with the engine passed as fit to fly, before failing leak checks upon its return is under investigation.

“2045 is the engine that had brown contamination prior to STS-127, which was cleaned a couple of times. That came as a surprise because they did not think that the brown contamination would pit the nozzle tubes,” added the memo.

“Will have some folks come out this week to take a good look at it. They have taken carbon tape samples, and done some digital microscopic work on the nozzle tubes. Engine 3 also had some brown residuals. (However,) post-flight leak checks look within family, nominal.”

A later memo noted engineers had then conducted a full mapping of the engine to get an exact count of leak areas. More than triple the original number were found.

“SSME (Pratt & Whitney Rocketdyne/KSC): On Engine 2045 that came out of position 1 for STS-127, had over 100 nozzle tube leaks on that nozzle,” added the latest Shuttle Standup/Integration report on L2. “Finally completed mapping that nozzle, and had a total of 340 tube leaks of various classes.

“Have a team, formed, working through a fault tree and a history of that nozzle to find out how it turned up in the corroded state we have here. Will report on that information once the failure investigation team is concluded.”

Further articles will follow as the investigation produces its findings and any potential impact on the remaining SSMEs set to fly.

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

No related posts.

Pad Processing:

“The team continues to work Launch Countdown preps supporting a S0007 Call to Stations for 2230L tonight,” noted Friday processing information on L2. “Launch is scheduled for 8/25, with a nominal T-0 at 0136L.”

Yesterday, Gaseous Nitrogen offload in support of a CHIT from JSC (Johnson Space Center) regarding Weight and Center of Gravity requirements was completed, as was replenishment of the LH2 (Liquid Hydrogen) storage tank at 39A via eight tankers.

Meanwhile, engineers have been working the pressurization Discovery’s OMS (Orbital Maneuver System), RCS (Reaction Control System), Gaseous Helium, and Gaseous Nitrogen systems for flight.

“OMS/RCS GHE/GN2 pressurization to flight mass and MPS/SSME helium tank fill to flight pressure began at 0022 EDT. It continues and should be complete on 2nd shift.”

During this OMS/RCS pressurization process, the final portion of the FPCA3 (Forward Power Control Assembly) retest was conducted - with all information pointing to a successful retest of the Main Bus Controller.

“IPR (Interim Problem Report) 56 update: The OMS/RCS portion of the FPCA3 retest will take place during stage 2 pressurization (approx. 1300 EDT), in parallel with S0071 (Hyper/MPS pressurization).”

Once these pressurization efforts are complete, Pad 39A will be reopened to necessary processing personnel and Orbiter aft closeouts for flight will resume. On tap for early Saturday morning is the installation of the 50-1 and 50-2 flight doors.

Furthermore, the teams also worked two minor issues, one with Discovery’s SSMEs (Space Shuttle Main Engines) and one with the Shuttle Landing Facility (SLF) Auto-Transfer Switch 94.

“Inspections during Aft Closeout revealed the need to remove and replace two SSME harnesses,” noted processing information.

Both harnesses have been replaced at this time. A retest of the system is expected later today/early tomorrow morning after Hyper/MPS pressurization is complete. The issue with the Auto-Transfer Switch at the SLF (Shuttle Landing Facility) has similarly already been corrected.

“Launch preparations at the SLF revealed Auto-Transfer Switch 94 would not function properly impacting the South Ball Bar Lighting,” added processing information. The problem was traced to a bad transfer motor. The motor was repaired and retested yesterday with no issues identified.

Kennedy Space Center Special Topics:

As part of the standard post-launch inspections, workers at the Kennedy Space Center have compiled a list of IFAs (In-Flight Anomalies) and Special Topics that were reviewed by program and agency managers during Discovery’s/STS-128′s Flight Readiness Review process.

Following STS-127 last month, “All 127 KIFAs (KSC IFAs) have been baselined at the KSC Engineering Review Board (ERB) and Integrated IFAs have been partnered with Safety Engineering & Integration (SE&I).”

In all there were eight pad debris items noted by KSC engineers, five FOD (Foreign Object Debris) items, and one Ground Support Equipment (GSE) item for a total of 14 items.

“KSC Opened 14 STS-127 IFAs,” notes the SSP (Space Shuttle Program) FRR Special Topics presentation – available for download on L2. “Thirteen debris IFAs have been addressed at the ERB and the integrated IFA review was presented to the SE&I community on July 31st with 14 debris items.”

The presentation notes that the debris liftoff risk matrix remains unchanged after STS-127 (classed as infrequent, catastrophic) and no STS-127 KIFAs are a constraint to Discovery.

In fact, since KSC began keeping records (STS-117 in June 2007), STS-127 is tied with STS-122 for the second-least General Pad debris items (8) found post-launch. The flight that had the least General Pad debris items was STS-123 (five items).

Furthermore, STS-127 had the least System Specific Debris items (5) and the second-least System Specific GSE items (with only one logged GSE specific item identified).

The presentation also notes that STS-127 had the lowest overall number of KIFAs since records began with STS-117 – demonstrating the intense care that is taken by the engineers.

The second of three special topic items pertained to NASA managers was the T-0 Umbilical Ice formation observed on STS-119, STS-125, and STS-127.

“Observation: During the last three launch attempts, ice formation was detected on the bottom of the LH2 T-0 umbilical,” notes the FRR presentation.

An engineering analysis performed prior to the start of Countdown operations for Endeavour’s (STS-127′s) July 11th launch attempt detected a leak in the Ground Cooling Unit.

A waiver was accepted for the launch attempts on the 11th, 12th, and 13th of July. However, during the 48-hour scrub turnaround between the 13th and the 15th a “sniff check” was performed at the T-0 umbilical. This “sniff check” detected Freon – which was noted on past launches as having generated ice formations.

After Endeavour successfully launched, an audible leak was detected from the MLP-3 Freon Return Quick Disconnect.

A similar test was performed on Endeavour after her landing at KSC on July 31st. That leak check did not reveal any Freon in the area, confirming that the leak was from the ground and not from the vehicle.

The presentation further notes that all of Discovery’s flight Quick Disconnects have new internal seals and T-0 mate leak checks “were nominal.”

The final Special Topic discussed was the LH2 T-0 peripheral seal ice formation.

“Observation: During previous missions, ice formation has been detected in areas internal and external to the LH2 T-0 umbilical,” notes the Special Topics presentation.

T-0 exterior ice was also noted. “T-0 Exterior Ice forms on the vehicle when cold gas escaping from the peripheral seal interacts with expected ambient humidity or condensate on the vehicle.”

This ice formation does represent a debris concern even though ice formation/accumulation on the T-0 GSE is considered normal.

As such, multiple mitigation techniques have already been implemented while the root cause investigation continues.

“Installed Room-Temperature Vulcanized (RTV) ‘Water Diverters,’” notes the presentation. “Peripheral Seal corners have RTV applied to the per designed holes in place of fabricated water diverters that were used for STS-125 and STS-127.”

Additionally, verification of proper seal configuration post-rollout to the Pad-A was performed to ensure that the vibrations associated with rollout did not dislodge the water diverters.

Other inspections included verifying that the Felt Reusable Surface Insulation is free of contaminants and that that RTV sealant is installed at the peripheral seal top splice plate – which is the location where a water leak path was discovered on STS-127.

KSC Post-127/Pre-128 Information:

Other KSC information presented to NASA managers pertained to the SRB Main Flame Deflector and STS-128 Launch Countdown Turnaround Options/Constraints.

For the SRB Flame Deflector, “Several sections on the SRB side of the Flame Deflector had missing Fondu Fyre or had indications of subsurface damage following the STS-127 launch,” notes the KSC presentation.

The entire flame trench was inspected after STS-127′s launch with all suspect areas of Fondu Fyre identified and reported to the KSC ERB. Inspections for hollow areas were also performed.

In all, 215 sq. ft. of Fondu Fyre were replaced after STS-127 – with no areas of concern or interest remaining ahead of STS-128.

In all, 65 percent of the SRB side of the Main Flame Deflector has been replaced since Shuttle flights resumed from Pad-A in June 2007. Pre-planning work for the beginning of resurfacing of the SSME side of the Main Flame Deflector prior to STS-129 is in work at this time as well.

The final piece of information presented to the FRR by KSC pertained to the Launch Countdown Turnaround options/constraints for STS-128.

Currently, Discovery’s PRSD (Power Reactant Storage Distribution) system load (the onboard Fuel Cell reactants) is expected to result in 7-days of Pad Hold Time for Liquid Oxygen (LO2) and 10-days of Pad Hold Time for Liquid Hydrogen.

Additionally, 450 lbs of Liquid Oxygen will be offloaded to assist with Ascent Performance Margins. This operation will add five hours to the PRSD load schedule during the countdown.

This PRSD load will eliminate the need to perform a 48-hour single commodity top-off operation. Instead, a 72-hour dual commodity top-off with offload would be performed instead.

However, all top-off scenarios are moot points since the LO2 Pad Hold Time exceeds the duration of Discovery’s launch window.

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

No related posts.

ET-131:

If External Tanks could survive their return to Earth, ET-131 would have found itself being placed on the naughty step inside the Vehicle Assembly Facility.

Two scrubs, caused by gaseous hydrogen leaks at the Ground Umbilical Carrier Plate (GUCP), forced STS-127′s launch to slip from its targeted launch date.

After realigning to acceptable weather conditions a month later, ET-131 shed an unusually large amount of foam during Endeavour’s ride uphill – mainly from the intertank region.

Notably, none of the liberated foam managed to cause anything more than cosmetic damage to Endeavour. However, Lockheed Martin – involved in ET-131′s manufacture at the Michoud Assembly Facility (MAF) – classed the tank’s performance as “on the outer edge of our family of experience.”

That classification came during the STS-127 IFA (In Flight Anomaly) review, which was dominated by ET-131′s events, partly due to the lack of any other issues with the highly successful flight to the International Space Station (ISS).

GUCP Leaks:

This issue is likely to be a thing of the past, after an investigation into ET-131′s leaks identified a misalignment of the “feet” – by a very small fraction – on the carrier plate, enough for the tiny hydrogen molecules to leak through the flight seal.

Following a realignment during re-installation, the addition of a more forgiving two-part flight seal, and a confidence check via a tanking test, no further leaks were detected on the subsequent loadings.

“STS-127-I-003: LH2 Leak at ET Ground Umbilical Carrier Plate (GUCP). LH2 leakage at the GUCP rose above the launch commit criteria limit and caused launch scrubs on two attempts,” noted expansive notes on the STS-127 Integrated IFA presentation – one of 11 IFA presentations presented to the Program Requirements Control Board (PRCB) meeting, and available to download on L2.

“Associated Hazard Report: ISPR-02 – ET Vent Arm System (ETVAS) Umbilical Malfunction. Cause Y – ETVAS Umbilical H2 Fluid System Failures Prior to T-0 Separation due to leakage.”

ET-132 will still find itself under the spotlight for STS-128′s late August attempt, with the manufacturing changes not sure to kick in until STS-129′s ET-133 tank. However, lessons learned from ET-131′s leaks will be incorporated into ET-132′s GUCP installation and tanking.

“GUCP leak: (Engineering changes) written and implemented on ET-132 to incorporate countermeasures from ET-131. Enhanced process for installation incorporated for KSC. Design change implemented for ET-133 and up,” added the specific ET-131 IFA presentation.

For all 20 NASASpaceflight.com articles on the GUCP, click here: http://www.nasaspaceflight.com/tag/gucp/

Foam Losses:

Three main areas of foam loss were observed during the ride to orbit, not unusual for a shuttle launch, but out of character for tanks that have flown since Return To Flight – due to the massive improvements in mitigating foam liberation by the ET engineering workforce.

“STS-127-I-004 – ET TPS Loss at LO2 Ice Frost Ramp (IFR) 718. Foam loss at IFR 718 exceeds risk baseline,” noted the integrated IFA presentation for STS-127 on the first area of foam loss placed under focus.

“Associated Hazard Reports: IDBR-01 – Ascent debris impact to SSV (Space Shuttle Vehicle). Cause I – External Debris Impact to the SSV During Ascent. Due to ET Foam (PDL-1034/NCFI-26-007/BX-265). Located at the LO2 Tank Ice/Frost Ramps and BX-265/BX-250/PDL-1034/NCFI-26-007 (type of foam) located on the LO2 Feedline Bellows PDL Drip Lip.”

A large amount of work has taken place on the IFRs on the tanks, but mainly with the LH2 ramps. As with most of the ET mitigation efforts to reduce liberations, foam has been reduced on the main threat areas, thus lowering the potential mass of the foam losses that could impact the orbiter. Such has been the success, many future modifications are no longer required.

It is not known if any additional modifications can be made to the ramps, although it is still rare for the IFRs to shed foam that has a direct threat to the orbiter during ascent.

However, to add confidence the foam loss was a rare event, checks – including X-rays – have been carried out on Discovery’s ET-132, in order to ensure the foam has no underlying problem.

“LO2 Ice Frost Ramp Loss: Additional NDE (Non Destructive Evaluation) options pursued for ET-132 at KSC included X-ray and THz,” added the ET-127 IFA presentational to the PRCB, noting good news on the health of ET-132′s ramps – and further mitigation on the downstream tanks in New Orleans.

“All observations were within performance expectations. LO2 IFR TIM (Technical Interchange Meeting) at MAF on July 29-30 to review design, process, and inspections (complete).

“Planning to increase BSx/ THz NDE inspections to include (location/station) Xt718 (minimum) for tanks at MAF.”

The second area of foam loss that made the IFA review related to a section of ET-131′s Bipod closeout foam, a liberation that has not been observed on most of the recent tanks to fly uphill with the shuttle.

This area of foam has been greatly reduced, with the elimination of bipod ramp TPS (Thermal Protection System – Foam) – a large area of foam which liberated during STS-107′s ascent, resulting in the fatal damage to Columbia’s Reinforced Carbon Carbon (RCC).

No association – other than the location – can be made to the loss of a suitcase sized ramp that damaged Columbia, and the much smaller areas of closeout foam that remains near the bipod struts on post Return To Flight tanks.

Also, the loss is only being investigated due to the “potential” for an impact with the orbiter – as no impact was observed via the array of cameras that carefully track the shuttle during ascent.

“STS-127-I-006 – ET TPS Loss Outboard Section of the –Y Bipod Closeout. Foam loss exceeds risk baseline,” noted the Integrated IFA presentation.

“Associated Hazard Reports: IDBR-01 – Ascent debris impact to SSV. Cause O – External Debris Impact to SSV During Ascent. Due to ET Foam Located at the Bipod Closeout and Bipod Jackpad Closeout – PDL-1034/NCFI-26-007 / BX-265 (type of foam).”

Once again, engineers double-checked the health of the TPS application in the specific area of ET-132, and found no issues – again pointing to a one-off incident with Endeavour’s ET-131 tank.

“Y Bipod loss: Risk assessment required to accept increase in mass beyond (previously defined) limits,” added the ET-131 IFA presentation. “ET Project planning to re-assess wire bonding process to ensure technique is meeting design intent. Additional NDE performed on ET-132 revealed no anomalies as expected.”

However, it was the intertank losses that provided the most “dramatic” images of foam loss from ET-131, due to the visible streaks of missing foam seen on the ET photography by the crew after ET sep, and the ET Umbilical Well photography that were later downloaded to engineers on the ground.

“STS-127-I-005 – ET Intertank TPS Foam Losses: Multiple foam losses exceed risk baseline,” noted the Integrated IFA presentation.

“Associated Hazard Reports: IDBR-01 – Ascent debris impact to SSV. Cause G – External Debris Impact to SSV During Ascent. Due to ET Foam – NCFI 24-124 (type of foam) located on the Intertank Acreage.”

Again, impacts with the orbiter failed to cause any concern to engineers on the ground, from an orbiter damage standpoint. Only minor cosmetic damage noted on Endeavour’s starboard Chine area.

However, no chances are being taken, with an investigation into the incident relating not only to the root cause with ET-131, but checks into the health of ET-132′s intertank foam.

“Intertank losses: Special investigation kicked off to drive to root cause. Fishbone (investigation) problem solving technique being used to perform root cause investigation,” noted the ET-131 IFA presentation.

“No unique root cause identified to date – requires updated risk assessment. Detailed assessment of ET-131 / STS-127 and ET-132 / STS-128 as-built process data in progress. Extensive adhesion tests performed on ET-132 to provide confidence for flight.”

Although no “unique” root cause has been found, leading candidates have already been noted, such as dust/contamination finding its way on to the intertank structure, prior – or during – the automated foam applications at the Michoud Assembly Facility.

The tank was also put through its paces ahead of launch, via the GUCP and weather related scrubs, resulting in six cryo cycles. While the tanks are certified for 13 cryo cycles, this was the most a tank has endured for many years.

“Number of Cryo Loadings – 6: Fleet leader for SLWT (Super Light Weight Tank) – tied with ET-35 (1990 launch) for first overall,” added Lockheed Martin’s overview in the IFA presentations.

“Number of Pressurization Cycles – 7. Tied for first with ET-120/STS-120 (tied for 5th overall). On-pad stay time (days) – 90. ET-131 on-pad time follows only ET-127/STS-119 (108 days) for current SLWT foam system.”

STS-127 Specific Articles, including all scrubs: http://www.nasaspaceflight.com/tag/sts-127/

ET-132 Investigation/Checks:

Opening results, gained from the ET-132 Intertank Bond Adhesion Tests and LO2 Ice Frost Ramp / –Y Bipod NDE Analysis effort that have taken place on Discovery’s tank inside the VAB. found no candidates that would suggest ET-132 is suffering from the similar issues observed with its predecessor.

Those checks, mainly surrounding pull tests to check the adhesive properties between the foam and the tank structure – which may have been downgraded via the dust/contamination theory – have been taking place in stages, all of which have found no issues with Discovery’s tank.

The inspections also took a closer look at the other areas on ET-132, which shed during ET-131 ride uphill.

“Purpose: Provide results of additional tests and inspections performed on ET-132 / STS-128 at KSC,” noted a specific investigation presentation to the PRCB at the end of last week – and available to download on L2.

“Additional bond adhesion data needed to provide confidence in the as-sprayed TPS integrity for ET-132. THz inspection of LO2 Ice Frost Ramp and –Y Bipod performed to identify whether any unacceptable conditions exist.”

As noted by the IFA presentations, no unacceptable conditions have been found on the Bipod closeouts and the Ice Frost Ramps, and no issues have been found on the intertank pull tests – although those tests have been continuing to the point rollout of the STS-128 stack has been delayed to Tuesday.

Initially, tests on just 26 areas of ET-132′s intertank were called for – all showing good results, as the foam only broke loose when the pull far exceeded the stresses expected during ascent.

However, managers then called for 126 additional tests – again showing good results, prior to a final test drive on the final quadrant of the intertank. Those results are still being evaluated, as repairs to the pull test areas are carried out ahead of rollout to Pad 39A.

“Bond Adhesion Test Results: 26 bond adhesion pull tests initially performed on ET-132 / STS-128 to provide confidence in Intertank TPS application integrity,” noted the specific Analysis presentation to the PRCB.

“Twenty-six (26) tests with samples from each panel (8 panels). Tests planned on stringer top and sidewall leading / trailing edges. 26 cohesive failures – 2 low tensile pulls due to crooked pulls.

“126 additional tests performed on –Z (panels 7 and 8). 125 cohesive failures. One adhesive failure with a high tensile result at 52.4 psi. Chemical wipe performed for analysis. Results revealed no indications of contamination.

“Forward Work: Completion of TPS cause investigation. Perform bond tension tests of ET-133 (STS-129) at KSC to support flight rationale development.”

Flight rationale, which is being created for the upcoming Flight Readiness Reviews (FRRs), does not have to include specific root cause, given such an effort is near-impossible for a tank that was mainly destroyed during its re-entry.

However, the best possible understanding of both the events surrounding ET-131, and the status of ET-132 – in order to ensure the incidents do not reoccur – is the driving force behind having the best possible data for the FRRs.

Just how much work has been undertaken can be seen in X-ray and Terahertz scans on ET-132, which show a level of evaluation most humans would be lucky to receive.

“IFR inspections via BSX & THz Stations: 760 through 1851 (currently assessing more forward access).

“NDE performed on ET-132 LO2 Ice Frost Ramp. Process assessment of ET-132 Sta. 718 IFR Terahertz scan identified no issues. No anomalies noted (voids, cracks, etc.). Scans limited (whole ramp not scanned),” added the investigation presentation.

“Observations noted were either outside ramp volume or on metallic substrate features.”

X-rays were also used on the bipod closeout. Again, no issues were found on ET-132.

“NDE performed on ET-132 –Y Bipod Closeout: Process assessment of ET-132 –Y Bipod Terahertz scan identified no issues.

“Scans were as expected, dominated by hardware/geometric features (wires, adhesive bonds, fittings, flange, etc. However, No anomalies noted (voids, cracks, etc.). Foam Knitline features noted.

“Summary: NDE inspection of LO2 Ice Frost Ramp sta 718 and –Y Bipod completed. Engineering Assessment: No unexpected results. No apparent unacceptable conditions exist.”

It was always the general assumption that ET-131 performed like a rogue tank, given the huge strides that have been made in reducing foam liberation since the last major foam loss incident during STS-114′s Return To Flight – itself never specifically blamed on the tank, and more likely accidental damage at MAF.

The amount of evaluations that have taken place on ET-132 should add confidence that NASA is not willing to take such assumptions as flight rationale when it comes to the safety of their shuttle fleet – even when related to an incident that failed to cause any damage to the orbiter.

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

No related posts.

STS-127 Latest:

Following the clearance of the orbiter’s Thermal Protection System (TPS) by the Damage Assessment Team (DAT), Endeavour had two opportunities to land on Friday – both at KSC.

The first opportunity was taken, which called for a deorbit burn at 9:42am Eastern for a landing at 10:48am. Only KSC – the preferred landing site – was made available for Flight Day 17, with Edwards Air Force Base and White Sands added to the list on Flight Day 18. Sunday opportunities would have only been used in the event of a technical wave off on Saturday.

This is a nominal timeline for bringing an orbiter home, with consumables limited by LiOH canister (CO2 scrubbing) availability on board the orbiter for a +2 EOM (End Of Mission) schedule.

“All Life Support systems are performing nominally. There are no issues being worked at this time,” according to Mission Evaluation Room (MER) notes on L2. “GN2 Total: 323.8 lbm Total Supply Water: 526.5 lbm Waste Water Total Qty: 71.7 percent 121.6 lbm.”

The final Orbit Adjust (OA) burn was successfully carried out on Thursday, involving a short burn of multiple Reaction Control System (RCS) thrusters.

“OA was a PRCS Multi Axis burn (F1F, F2R, F2U, F3F, F3D, F4D, L1U, L4D, L3L, R1U, R3R, and R4D) occurring at TIG of 211/11:24:09 GMT,” noted Mission Management Team (MMT) notes on L2. “The burn time was 21.7 seconds with a delta V of 5.4 fps. The resulting orbit was 174.4 x 184.1 nmi. No Trim was required.”

However, it was during the Flight Control Surface (FCS) checkouts that one thruster – F2F – behaved off-nominally. This incurs no mission impact, due to redundancy and lack of use during re-entry.

“RCS Hotfire Procedure was initiated earlier than originally planned per crew request. Procedure was initiated at 211/08:36:46 GMT and terminated at 211/08:55:38 GMT,” added MMT notes.

“All 38 RCS jets were fired at least twice for at least 0.240 seconds per pulse with the exception of F2F. All thrusters have now been fired.

“F2F Failed Off on the first attempted pulse. Failure was annunciated by RM at 211/08:48:51 GMT. Jet is a third priority and not required for entry.”

Debris was also photographed by the crew during the FCS checkouts, although it is not understood to be anything other than ice.

Evaluations of the images on the ground have ruled out a similar incident to that observed by Discovery during the same checks on STS-124 – when a Rudder Speed Break (RSB) tab liberated from the aft of the vehicle.

Fleet-wide checks of that particular piece of hardware have since been carried out.

“Imagery of Debris During FCS Checkout,” noted one MMT presentation by the Orbiter Project Office. “Taken by the Crew with hand-held still cameras. Imagery reviewed by DAT (Damage Assessment Team) and can not associated with Orbiter hardware.”

Update: This has since been classed as ice.

Endeavour continues to perform extremely well, with only a handful of issues noted on the Mission Evaluation Room (MER) “funny” list, most of which are not specific to the orbiter herself.

“Loss of HUD Mini-cam Video (Bad Cable). Initially could not get HUD video. The crew eventually found the faulty cable and routed around it. Should be no impact,” was one example of the latest “funny” to make the list.

The Late Inspections provided a clear assessment of the vehicle’s TPS health during the docked phase of the mission, and confirmed a very “clean” orbiter. This resulted in the DAT engineers to allow the Mission Management Team (MMT) to give a go for re-entry.

“Overall coverage was very similar to the ‘as-designed’ coverage. The few areas that had slightly worse predicted coverage (some carrier panel tiles and a small section of the nosecap) were previously cleared or had adequate coverage, just less than ideal angle of incidence,” noted the DAT assessment notes on L2.

“The Imagery Analysis team has reviewed all of the images and the LESS/RCC team has cleared all late inspection regions of interest, giving a ‘GO’ for re-entry. This data was presented at the OPO (Orbiter Project Office) and MMT meetings, who concurred with the ‘GO’ for re-entry.”

A total of 141 Regions Of Interest (ROIs) were observed on Endeavour’s heatshield, which is below the average of 153 per flight – an average based on OBSS (Orbiter Boom Sensor System) availability since Return To Flight.

“LESS/RCC team cleared all late inspection regions of interest,” noted the DAT findings presented to the MMT. “Level 1 completed. Level 2 completed. Final disposition complete. No ROI exhibited any damage characteristics. The LESS PRT is GO for entry.”

Also notable was the lack of triggers on the Wing Leading Edge (WLE) Impact Detection System (IDS), a suite of sensors embedded into the leading edges of the orbiter’s wings which are used to “feel” any impact on the WLEs. The system is mainly used for ascent, but can also be used for on orbit monitoring for potential MMOD impacts.

During the latest monitoring phase – called for during Late Inspections – no triggers were noted.

“Wing Leading Edge Monitoring. Around 8.5 hrs monitoring on FD 15 during late inspection,” noted the DAT assessments. “No triggers observed. WLE completed the WLES deactivation and teardown.”

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

Related posts:

1. Endeavour and her SCA piggyback ride arrive in Louisiana, via JSC flyoverThe Shuttle Carrier Aircraft (SCA) and Endeavour departed from Edwards...

STS-127 Latest:

End Of Mission minus one day (EOM-1) involved the checkout of Endeavour’s systems for her return to Earth, including the Reaction Control System (RCS) jets and aerosurfaces.

The Flight Control Surfaces (FCS) checkout is a vital element of ensuring Endeavour can conduct the DAP (Digital Auto Pilot) stage of re-entry – as she changes from a spaceship into an aircraft.

The RCS will also be involved for the first part of re-entry, helping Endeavour control her attitude and positioning before and after deorbit burn, and also through entry-interface.

“FCS Checkout & Deorbit/Entry Operations: Nominal FCS Checkout. APU 1 (Auxiliary Power Unit) will be used for aerosurface drive and secondary actuator check. RCS Hotfire will invoke 2 pulse technique (based on propellant margins),” noted the Mission Management Team (MMT) plan.

One RCS thruster behaved off-nominally during the checkout – specifically F2F – although that holds no mission impact, as it is not used during re-entry.

The vehicle was – as expected – cleared for re-entry at the MMT, following the DAT (Damage Assessment Team) evaluations into the imagery gained from the Late Inspections. A few Regions Of Interest (ROIs) were noted, but that is to be expected.

Endeavour will target two attempts on Friday – both for her home base of the Kennedy Space Center. Friday looks hopeful on the weather front, and even better on Saturday, raising hopes she will not require a ferry ride home from California, unlike her older sister at the conclusion of STS-125.

“The weather forecasts for EOM, +1 and +2 was briefed. We have a decent shot at KSC on Friday and an even slightly better shot on Saturday. EDW (Edwards Air Force Base) and NOR (White Sands) forecasts are solid GO’s for all three days,” noted the MMT meeting notes on L2.

Consumables – as always – determine how long Endeavour can stay on orbit, in the event of landing wave offs. Currently, the deadline is Sunday, due to LiOH limitations related to CO2 removal. Sunday will be reserved as a technical wave off day, in the event problems with Endeavour force the crew to stay in space for an additional day.

“In addition, the MMT heard the Entry briefing. LiOH is the limiting consumable with only EOM+2 capability. Cryo margins are about 16 hrs above 16+2. Prop, N2 and water margins exceed +3 days. Only KSC will be called up on Friday, and all three sites will be called up on Sat since that will be our pick’em day,” noted the latest MMT presentation, available on L2.

“Planned EOM is Friday, July 31. Consumables support through EOM+2 (Sunday, August 3). LiOH supports EOM+2 and is the limiting consumable.

“Supply Water supports 7 opportunities over 4 days. Cryo can support 15 hours over EOM+2. OMS/RCS margin over 3-3-3 is: 100 lbs FRCS, 460 lbs ARCS, 980 lbs OMS. Group B powerdown nominally planned for wave-off days. N2 supports well beyond EOM+3.”

Once again, cameras will keep an eye on the four radiator retract hoses, during Payload Bay Door closure on Friday. This was called for following incidents with a couple of flights that suffered from kinks in the hoses, as seen during post flight processing, and in the pad flow ahead of launch.

“Nominal Deorbit/Entry operations: Deorbit Prep procedures will capture video of 4 radiator hoses during payload bay door closing,” added the MMT presentation.

“Edwards Permanent runway ready to support on EOM+1. Lakebed status: EDW 15/33 green. Northrup lakebed: green.”

Discovery STS-128 Latest:

Meanwhile, Discovery’s STS-128 launch date has slipped to NET (No Earlier Than) August 26, as the stack waits to leave the Vehicle Assembly Building (VAB) next week.

Mission Management Team (MMT) manager Leroy Cain noted the launch date will be “around” August 25, but a good idea of the real target will depend on when Discovery rolls out to 39A.

Discovery is now hard mated to her External Tank (ET-132) as part of S0004 Orbiter/ET mate operations.

“S0004 Orbiter/ET mate continues: Crew Module hatch functional was successfully completed. LO2 and LH2 umbilical ordnance installation, stud tensioning, and exterior closeouts are complete. LO2/LH2 Monoball installations and mates are in work,” noted processing information on L2.

This operation found a problem with the monoball electrical mate connections, which will require a repair.

“During LH2 monoball electrical mates connector 50P523 was found to have galled extension threads,” added processing information on Thursday. “Will probably have to demate the connector for repairs and then remate. Engineering is evaluating.”

Thursday involves the Shuttle Interface Test being carried out on the stack, while the STS-128 payload is scheduled to make its journey out to Pad 39A tonight. Discovery herself is set to move to the pad on August 3, for a 23 day pad flow prior to launch.

“The team continues to work toward payload move to Pad-A tonight; first motion is planned for 2000L. Payload Canister lift operations are scheduled to begin early (3rd shift) tomorrow. SSV (Space Shuttle Vehicle) rollout from the VAB to Pad-A remains planned for August 3. Terminal Countdown Demonstration Test is now scheduled for August 6-7.”

Related posts:

1. Endeavour and her SCA piggyback ride arrive in Louisiana, via JSC flyoverThe Shuttle Carrier Aircraft (SCA) and Endeavour departed from Edwards...

STS-127 Latest:

Endeavour and her crew have enjoyed a highly successful docked mission, highlighted by the completion of the Kibo laboratory, and five EVAs – the last of which was conducted on Monday.

Following the checkout of Endeavour’s rendezvous tools, the crew departed the International Space Station (ISS) and closed the hatches between the Station and the orbiter.

After undocking Endeavour was commanded through a full lap flyaround of the station – providing stunning imagery of the ISS - ahead of the final separation maneuver/burn.

Flight Day 15 opened with the Late Inspection surveys on Endeavour’s TPS, including her port and starboard RCC (Reinforced Carbon Carbon) wing leading edges, and a full survey of her nose cap. As has been typical for the STS-127 crew, the task was completed two hours ahead of the timeline.

The results of the survey will be downlinked to engineers on the ground, as the DAT (Damage Assessment Team) check for any new areas of damage to the orbiter since the pre-docking inspections. Clearance for the vehicle to re-enter usually takes around 24 hours.

If – in the highly unlikely event – serious damage is found, Endeavour would still be able to return to the ISS, where the crew would take up safe haven until Discovery is launched as the LON (Launch On Need) rescue vehicle.

FD15′s current plan includes a burn known as SEITE-1 (Shuttle Exhaust Ion Turbulence Experiments). An OA (Orbital Adjustment) was required to lower orbit to meet Flight Rule rationale for acceptable relative position of deployable payloads with ISS.

Those payloads are DRAGONSAT and ANDE-2, which are currently housed in Endeavour’s payload bay. They will be deployed on Flight Day 16.

“DRAGONSAT: The Dual Autonomous Global Positioning System (GPS) On-Orbit Navigator Satellite (DRAGONSAT) payload is a new endeavor into establishing autonomous spacecraft rendezvous and docking capabilities and is primarily focused on data collection for future control algorithms,” noted FRR documentation on L2.

“The payload is cosponsored and operated by Texas A&M University and The University of Texas at Austin.

“ANDE-2: The Atmospheric Neutral Density Experiment (ANDE) ‘Risk Reduction’ (RR) was first flown on STS-116 as one of the Space Test Program – H2 (STP-H2) experiments.

“Similar to its predecessor, ANDE 2 will be flown on a shared flight as a secondary payload by the National Aeronautics and Space Administration (NASA) and the Department of Defense (DoD) STP on STS-127.

“The two goals of the ANDE 2 mission are to provide high quality satellites with stable and well-determined coefficient of drag, for calibrating techniques and models for precision orbit determination; and to provide atmospheric composition for validating Air Force sensors.”

STS-127 remains on track for a Friday landing at the Kennedy Space Center (KSC), with the Mission Management Team (MMT) discussing the landing opportunities for the first tine, now that Endeavour has departed from Station.

“No issues were raised at the meeting. The weather office provided a preliminary look at landing weather for Friday and Saturday,” noted MMT notes on L2. “They are predicting that drier air will be coming in from the Southeast and assist in setting up good landing weather.

“There is a slight chance of showers at KSC on Friday and Saturday but the weather generally looks favorable at this time. Entry Flight Director Mr Lunney will provide the entry briefing at the MMT tomorrow (Wednesday).”

ET-131 Foam Loss Investigation:

As the PRCB (Program Requirements Control Board) prepare to meet on Thursday for STS-127′s IFA (In Flight Anomaly) review – a key milestone that aids the next flight’s Flight Readiness Reviews (FRRs) – the topic of ascent debris is homing in on a root cause for the ET-131 foam loss events.

ET-131 lost several areas of foam from its Intertank region during ascent. None of the liberation events caused anything more than cosmetic damage to Endeavour’s starboard Chine.

Pull tests were carried out on ET-132, set to fly with Discovery on STS-128, all of which came back with good results on the adhesive properties between the foam and the tank’s structure.

Those results add confidence that ET-131′s foam loss events were a one-off, and are unlikely to repeat on ET-132 or other downstream tanks.

“Foam Loss Investigation Team Update: The Fishbone Team worked all last week and through the weekend looking to identify the possible causes and failure modes,” noted an update on the latest Shuttle Standup/Integration report on L2.

A candidate for the foam loss has been found, specifically dust, or substrate contamination, on the tank’s structure ahead of the application of foam.

“The failure mode is being attributed right now to the low-to-no foam bottom-line integrity in their focus and on the failure modes observed on ET-131, which was foam loss with exposed primer. No one has said they didn’t see any primed surface yet.

“Right now the most likely causes are substrate contamination (e.g., dust) prior to foam application. Looking at cleaning and primer touch up processes, which all are in Cell G (at the Michoud Assembly Facility).

“Other observations/findings to date are: No obvious violations to process found in paperwork. Some of the cleaning techs during that time were new employees, although certified and trained. Had a large amount of primer touch up.

First intertank sprayed after return-to-flight. Tank sat around plant and was moved several times. Did paper spray on tank prior to checking out the cell.

“Later this week, are looking to have a package to bring forward on the most likely causes to start briefing the communities and the independent review team.”

It is understand that a root cause is not required for STS-128′s Flight Rationale at the FRRs, although understanding the reasons behind the foam loss would allow for the swift closure of the IFA.

STS-128′s SSP (Space Shuttle Program) FRR will take place at the Johnson Space Center on August 11 and 12, before the STS-128 Agency FRR, on August 18, will confirm the launch date.

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

Related posts:

1. Endeavour and her SCA piggyback ride arrive in Louisiana, via JSC flyoverThe Shuttle Carrier Aircraft (SCA) and Endeavour departed from Edwards...

EVA-5:

As is the case with the ever-changing nature of manned space exploration, changes to planned mission timelines are a routine occurrence. 

Given the highly complex nature of the STS-127 assembly mission to the International Space Station (ISS), EVA-5 was planned into the mission timeline to be a catch up day for any mission EVA (Spacewalk) objectives that, for whatever reason, could not be accomplished in their originally planned slots.

This concept has proved to be invaluable for astronauts Chris Cassidy and Tom Marshburn, who completed the mission’s fifth and final spacewalk on Monday.

Working on a revised EVA schedule, Marshburn and Cassidy were tasked with installing a patch on a panel on the Z1 truss (Cassidy) and removing covers from Canada’s Special Purpose Dexterous Manipulator (Marshburn).

They also installed the forward and aft cameras (or Vision Equipment as they are called) on the Japanese Exposed Facility (both Cassidy and Marshburn), and were set to move the S3 Zenith Outboard PAS into its deployed cofiguration.

However, that latter task was deleted during the EVA due to a 5 hours 30 minutes restriction on Cassidy’s METOX limitations. The PAS task would have taken 90 minutes to complete, as a get-ahead task. Several foot restraint tasks – in order to help STS-128 – were completed instead.

The contents of EVA-5 had to be replanned primarily because of delays encountered during EVA-3 and the P6 truss battery R&R (removal and replacement) activities. 

EVA-3 was supposed to see the R&R of four P6 batteries with EVA-4 seeing the completion of the battery R&R (two batteries) and other scheduled tasks.

However, after just two batteries had been installed on EVA-3, the spacewalk was terminated due to rising CO2 (Carbon Dioxide) levels in Chris Cassidy’s spacesuit.
 
Therefore, EVA-4 was devoted to the completion of the battery R&R with other previously planned tasks for EVA-4 slipping into EVA-5.

To accommodate these objective into EVA-5, several get-head tasks originally planned for the spacewalk were deferred until a later time. EVA-5 was set to be scheduled for about six and half hours in duration, but ended after 4 hours and 54 minutes - due to great progress on the opening tasks and the METOX limitation.

Fuel Cell 3 Update:

As noted previously by this site, Shuttle Mission Managers discussed a potential issue with Endeavour’s Fuel Cell 3 (FC-3) in the hours before her launch on July 15.

According FD-2 (Flight Day 2) MMT briefing materials - available for download on L2 - “Pre-launch tests conducted to verify FC-3 KOH values remain within operation limits when FC-3 is loaded at an expected on-orbit SSPTS (Station to Shuttle Power Transfer System) lower power level.”

These tests indicated that FC-3 could be operated at the lower power level without causing “cell flooding.”

However, as Mike Moses, chairman of the pre-launch MMT at the Kennedy Space Center, explained during a pre-launch interview on Wednesday, “At the pad, water was cycled through the Fuel Cell to verify that we could transfer for drinking water. If we don’t drain the water, it’ll build up. Too much water would let the electrolyte compound (KOH) into Fuel Cell and end up drying out the Fuel Cell,” which would render it inoperative.

Furthermore, Moses explained that “We can’t monitor the exact KOH concentration on orbit, but we can on the ground. When we run the SSPTS system on orbit, it takes off a lot of the load from the Fuel Cells. That means we don’t dry the fuel cells out enough and the temperatures in the Fuel Cells increase.

“If we can’t drain the Fuel Cells, then we can’t take as much power from the SSPTS and we lose some mission duration.”

Following this assessment, the Mission Evaluation Room (MER) processed and approved a request from Electrical, General Instrumentation, and Lighting Engineer to operate FC-3 below the 29 percent KOH limit set by the Combined Environmental Test document rules.

With this new procedure, FC-3 functioned as expected until FD-8.

According to the FD-10 MMT briefing materials – available for download on L2 – “FC3 sustaining heater remained powered longer than expected (Mission Elapsed Time 7-days 21-hours 19-minutes 48-seconds to 7-days 21-hours 41-minutes 12-seconds) while the Fuel Cell was at low power levels.”

To preclude the possibility of another heater becoming stuck in the ‘on’ position, the load on FC-3 was increased by “taking Main C Bus Tie” to the off position.

As of FD-10, the forward plan was to perform a Main A to B Bus Tie to obtain improved power transfer abilities while still maintaining FC-3 at the higher power level to prevent heater “sticking.”

While this new issue with FC-3 was identified quickly, the stuck heater has caused an impact to Endeavour’s consumable (liquid hydrogen and liquid oxygen fuel for the Fuel Cells) status.

According to the preliminary calculations at the end of FD-9, Endeavour’s consumable status with the Station to Shuttle Power Transfer System (SSTPS) was 1-day and 22-hours above the baselined 16+0+2 day mission and 1-day above the baseline without SSTPS.

However, at the end of FD-11, that margin was down to only 22-hours above the baseline with SSTPS and 14-hours without SSTPS.

While this does not affect Endeavour’s mission at the Station, it does affect the time Endeavour can stay on orbit in the event of unfavorable weather at her landing sites or for a unforeseen systems error after undocking.

As of now, Endeavour only has two weather waive off days before her onboard fuel status (consumables) would force Flight Directors to land her at the earliest available Primary Landing Site in the U.S. (either the Kennedy Space Center in Florida, White Sands Space Harbor in New Mexico, or Edwards Air Force Base in California).

While this consumable status is perfectly acceptable - as all Shuttle flights are planned around the potential for at least two weather waive offs - Flight Directors and Mission Managers always prefer to have a little more consumable margin than just the prescribed minimum.

As such, Mission Managers do not want to violate/eliminate that two day contingency time.  As noted in the FD-10 MMT update, “Should the heater fail on permanently there will be a large margin impact and the FC3 will not be considered usable as a last fuel cell.”

As a result, a request has been submitted to further refine the acceptable KOH concentration levels for FC-3.

“Change KOH concentration lower instrumentation limit from 29 to 24 percent,” notes the MMT FD-10 update.

“Based on the Fuel Cell 3 operational data observed during the Pre-launch FC Low Power test, the Fuel Cell can be operated at lower power levels without the Condenser Exit Temperature set point causing cell flooding.  The Fuel Cell was operated over an extended period of time (~1 hr) with the calculated KOH concentration below the 29 percent instrumentation limit without any indications of cell flooding.”

At the time of the FD-10 MMT update, the KOH concentration of FC-3 was holding at ~28.5 percent.

Pad 39A Status Update:

Following the successful launch of Endeavour on July 15, technicians began the process of the turning Pad 39A around to prepare it for the arrival of Space Shuttle Discovery and her associated payload.

These initial inspections revealed two areas of damage on the SRB (Solid Rocket Booster) flame deflector.

“The SRB Main Flame Deflector liberated fondu-fyre during launch.  Two areas, measuring 7′ x 12′ and 3′ x 4′, were identified.  These are located on the mid and upper eastern half of the Main Flame Deflector,” noted a daily processing report on L2.

After initial pad inspections were complete, and pad repairs underway, the Mobile Launch Platform (MLP-3) that Endeavour launched off of was moved off the pad to the east refurbishment site to the north side of the VAB.

The final operations performed at Pad 39A included upper and lower jackscrew replacement on the Gaseous Oxygen Vent Arm, replenishment of the Liquid Hydrogen and Liquid Oxygen storage facilities, and SCAPE operations of various fuel meters and systems around the pad area.

As of now, Discovery’s payload (the MPLM Leonardo) is expected to arrive at Pad 39A during the early morning hours of Friday, July 31st with Discovery rolling out to the pad in the early part of the following week.

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

No related posts.