The GUCP:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

GUCP History – STS-127:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

GUCP History – STS-133:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

GUCP – SLS:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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Captain Poindexter:

After being selected as an astronaut candidate in June 1998, Captain Poindexter served in the Astronaut Office in the Shuttle Operations Branch at Johnson as the lead support astronaut for NASA’s Kennedy Space Center in Florida.

His first taste of space came with Atlantis after being selected as pilot for the STS-122 mission. During final preparations for the launch of STS-122 in December 2007, Atlantis – or more specifically her External Tank – would make Capt. Poindexter and his crewmates wait as engineers worked to nail down and fix the vexing ECO (Engine Cut Off) sensor anomalies that had plagued the Shuttle fleet since STS-114 in 2005.

After two months of testing and fixing of the ECO sensor issue, Atlantis launched on the STS-122 flight on 7 February 2008, exactly seven years to the day after her STS-98 mission.

During STS-122, Atlantis and her crew delivered the first Laboratory to ISS since the U.S. Destiny lab (STS-98). STS-122 marked the beginning of construction of the international partner laboratories with the delivery of the European Space Agency’s Columbus research module to the ISS.

The mission also marked the celebration of NASA’s 50th anniversary and the 50th anniversary of the first US unmanned orbital flight.

After 8 days and 16 hours of docked operations, Atlantis undocked from the International Space Station on 18 February 2008, with Captain Poindexter performing a flyaround maneuver of the orbital outpost.

Atlantis triumphantly returned to Earth on 20 February 2008 with a mid-morning landing under the control of Captain Poindexter and Commander Stephen Frick at the Kennedy Space Center.

Of Captain Poindexter on STS-122, fellow crewmate Leland Melvin said, “Alan and I joined the astronaut corps in 1998 and flew together on STS-122, which was truly an incredible experience. He was a passionate, caring and selfless individual who will be missed by all.”

Following STS-122, Captain Poindexter then gained the command of his own orbiter after being selected to the STS-131 crew. The orbiter was the flagship, Discovery, tasked with her penultimate mission.

After a near-flawless countdown, Discovery lifted off on STS-131 on Monday, 5 April 2010 at 06:21:22 EDT – 49 minutes before sunrise and 17 minutes after a long, visible pass of the ISS over the Kennedy Space Center.

With Poindexter at the helm, STS-131 and Discovery marked the final nighttime launch of the Space Shuttle Program, the first time that four women worked together in space (three on Discovery, one on ISS), the last flight of the Space Shuttle to carry rookie astronauts, the last flight of a Japanese astronaut on the Space Shuttle, and the first time that two Japanese astronauts were in space together (one on Discovery, one on ISS).

During the 15 day 2 hour flight, Discovery delivered nearly 20,000lbs of internal cargo to the ISS via the MPLM Leonardo, and three EVAs were conducted at the Station.

Following one weather wave-off day and a single orbit wave-off due to weather concerns, Discovery returned to the Kennedy Space Center on 20 April following a descending node reentry over the heartland of the United States, landing on Runway 33 15 days 2 hours 47 minutes and 11 seconds after launch.

With this, STS-131 stands as Discovery’s longest flight, resulting in Captain Poindexter having a special bond with the flagship, commanding her in space for her longest single mission period.

Reflecting on her time as Poindexter’s fellow astronaut and boss, Peggy Whitson, chief of the Astronaut Office at NASA’s Johnson Space Center in Houston, said, “We in the astronaut family have lost not only a dear friend, but also a patriot of the United States. He proudly served his country for 26 years as a fighter pilot, test pilot, astronaut and commander of a space shuttle.

“I am proud to have both flown in space and worked with him for so many years. Dex will be deeply missed by those of us at Johnson and the entire NASA family.”

Poindexter obtained an undergraduate degree with highest honors from the Georgia Institute of Technology in Atlanta and a graduate degree from the Naval Postgraduate School in Monterey, California.

After STS-131, he retired from NASA and the astronaut corps in December 2010 and returned to serve in the United States Navy as Dean of Students at the Naval Postgraduate School.

“Dex was a wonderful human being and a pleasure to have in the astronaut office,” Janet Kavandi, fellow astronaut and Director of Flight Crew Operations said. “His good-natured demeanor made him approachable to his crews and the many people at Johnson and Kennedy who enabled his missions.”

RIP.

(Images via NASA)

If you wish to post your condolences: http://forum.nasaspaceflight.com/index.php?topic=29320.0

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SSMEs Shipping Out:

The change of home from the Kennedy Space Center (KSC) to NASA’s Stennis Space Center (SSC) in south Mississippi is a natural transition for the 15 engines, not least because the SSMEs underwent testing at Stennis ahead of their flight roles with the orbiters.

However, it’s their future role of becoming part of the SLS test program which has breathed new life into the famous engines, some of which will actually gain the honor of going out in style, launching one last time with the SLS during the first few missions.

Their transition from KSC will take place one engine at a time, as they travel to Mississippi by truck. Once at SSC, the SSMEs will join SLS’ Upper Stage J-2X engine – which is being tested at the facility – allowing for all SLS engine assets to be in one location, leveraging the existing knowledge base, skills, infrastructure and personnel.

“The relocation of RS-25D engine assets represents a significant cost savings to the SLS Program by consolidating SLS engine assembly and test operations at a single facility,” said William Gerstenmaier, NASA’s associate administrator for Human Exploration and Operations Mission Directorate.

The relocation also frees up the Space Shuttle Main Engine Processing Facility at KSC, which became part of a commercial deal with Boeing – in collaboration with NASA and Space Florida – to being exclusively occupied  by the company, along with Orbiter Processing Facility 3 (OPF-3) and the Processing Control Center, as they ramp up operations for their CST-100 spacecraft.

“This enables the sharing of personnel, resources and practices across all engine projects, allows flexibility and responsiveness to the SLS program, and it is more affordable,” said Johnny Heflin, RS-25D core stage engine lead in the SLS Liquid Engines Office at Marshall.

“It also frees up the space, allowing Kennedy to move forward relative to commercial customers.”

SSME: End Of A Shuttle Era:

The RS-25s have an amazing flight record with the Space Shuttle – with only one engine suffering a problem during the entire 30 years of the program.

*To read about all three orbiters - from birth, processing, every single mission, through to retirement - click here for the links:
http://forum.nasaspaceflight.com/index.php?topic=25837.0*

That single issue occurred during STS-51F with Challenger, when one of two high pressure fuel turbopump turbine discharge temperature sensors for SSME-1 failed, leaving only one sensor active on the engine. Two minutes 12 seconds later, at Mission Elapsed Time 5mins 43secs, the second sensor failed, triggering the immediate shutdown of SSME-1.

The shutdown of SSME-1 significantly lowered the thrust profile for Challenger and triggered the only in-flight abort in Shuttle Program history: an Abort To Orbit (ATO) which allowed Challenger and her seven-member crew to reach a lower-than-planned but safe and stable orbit.

Nonetheless, before Challenger could complete her prolonged ascent (nearly 9mins 45secs in duration due to the lost thrust from SSME-1), an identical high pressure turbopump temperature sensor failure occurred in SSME-2.

Booster Systems Engineer Jenny M. Howard in Mission Control Houston acted immediately, instructing the crew to inhibit any further automatic SSME shutdowns based on readings from the remaining sensors. This quick action prevented the loss of another engine and a possible abort scenario far more risky or far worse than the already in-progress ATO.

When Challenger finally reached orbit, several aspects of the mission were retooled to account for the lower-than-planned orbital altitude.

Click here to read recent articles on the SSMEs: http://www.nasaspaceflight.com/tag/ssme/

As per the In Flight Anomaly (IFA) reports for the final three missions, all nine of the SSMEs performed admirably, as they assisted the orbiters for the ride uphill into orbit.

For STS-133, all three of Discovery’s SSMEs last flew with Atlantis during STS-129, although in different positions – after they required removing and re-installing in different positions, in order to allow a changeout of ME-1′s Low Pressure Oxidizer Turbo Pump (LPOTP) early in the flow.

Discovery flew with Main Engine 1 (ME-1) – serial number 2044, ME-2 – 2048 and ME-3 – 2058. All their related hardware was the same as that which flew with Atlantis, bar a couple of elements, such as a new nozzle for ME-1.

The only notable issue with the SSMEs occurred pre-launch, relating to a power issue with the redundant Main Engine Controller (MEC) on SSME 3.

The SSME controllers provides complete and continuous monitoring and control of engine operation. In addition, it performs maintenance and start preparation checks, and collects data for historical and maintenance purposes.

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

The controller is an electronic package that contains five major sections; power supply section, input electronics section, output electronics sections, computer interface section, and digital computer unit.

Pressure, temperature, pump speed, flowrate, and position sensors supply the input signals. Output signals operate spark igniters, solenoid valves, and hydraulic actuators. The controller is dual redundant, which gives it normal, fail-operate, and fail-safe operational mode capability. The problem was specific to the redundant controller on ME-3.

Actions taken during troubleshooting included the installation of a breakout box and the testing of three single phase circuit breakers for SSMEC 3B on Panel L4. Although this inspection was limited by access, engineers pro-actively replaced all 18 SSMEC circuit breakers at the recommendation of management.

The problem soon became clear when CB 109 was inspected, with a clear observation of non-conductive debris on the hardware, a key candidate for the original problem seen with SSME 3′s redundant MEC.

After the troubleshooting was signed off at the Flight Readiness Review (FRR), all three engines – and controllers – performed without issue during ascent.

“Engine operation was nominal. ME-1 2044, ME-2 2048, ME-3 2058 – No SSME IFA Identified,” noted the STS-133 SSME IFA presentation (L2 Link to Presentation). “SSME observations are encompassed by previous flight and/or test experience and identified as no impact.

For STS-134, Endeavour’s ride into orbit was aided by a noisy trio that were no stranger to the aft of the youngest orbiter in the fleet, after pushing her uphill during STS-130.

The engines were installed for one final trip with Endeavour in the following positions on the orbiter: ME-1 – 2059, ME-2 – 2061, while 2057 was ME-3.

Only one item of interest made it into the FRR documentation for the SSMEs ahead of STS-134′s mission, referencing the incident when an ELSA (Life Support) bottle fell from the entrance level near the 50-2 door and hit Main Engine 2 (ME-2) during Vehicle Assembly Building (VAB) processing operations.

“STS-134 Endeavour ME 2 ELSA Bottle Damage Inspections: Issue: Possible handling damage to ME-2. Background: ELSA Bottle dropped from above ME-2 to heat shield adjacent to controller during VAB processing. Damage observed above and adjacent to engine,” noted the STS-134 SSME SSP FRR presentation (L2 Link to Presentation).

“Dent in Orbiter GN2 Line. Dent on edge of Heat Shield near ME-2 controller. Witness statements and damage indicate no engine impact. Assessment conducted around 4.5 Ft assuming possible engine contact.”

With this issue cleared, Endeavour launched on her final mission without incident and successfully completed her mission on June 1, 2011.

As what became a regular observation, the 14-15 IFA presentations per mission (all acquired by L2 –  link to presentation collection) reviewing the mission post flight included a very short SSME presentation, noting no anomalies (L2 Link to Presentation).

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

For STS-135, Atlantis’ engines were ME-1 – 2047, ME-2 – 2060 and ME-3 – 2045.

Again, the only incident of note came before the engines were fired up at launch, when IPR-49 (Interim Problem Report) noted a problem with the Main Fuel Valve (MFV) on SSME-3, spotted during a tanking test to check the integrity of the modified stringers on the stack’s External Tank (ET-138).

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

The issue – the observation of a leak – was also covered in depth via the STS-135 SSP Flight Readiness Review (FRR) presentation for the SSMEs (L2 Link to Presentation), which covered how the issue was spotted during the Tanking Test, as it breached the Launch Commit Criteria (LCC) limitations.

As a result, the issue would have scrubbed the launch day countdown, showing a bonus side-effect of finding the problem during the Tanking Test.

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

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

The MFV was replaced out at the pad and put through a series of leak checks. While those passed, the real test came during launch day, when the system was put through the cryogenic environment of tanking. Again, the skilled KSC and SSME engineers were shown to have successfully fixed the problem, as Atlantis launched for the final time without issue.

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

Now these stalwart engines – which includes the spare flight set: ME-1 – 2052 ME-2 – 2051 and ME-3 – 2054 – plus three others, are departing KSC once again – this time by road.

SSME To SLS Core:

Their potential role with the SLS was noted during the final flights of the Shuttle, as the 2010 Authorization Act reversed the FY2011 budget proposal which would not have seen any involvement of the RS-25s.

With a Shuttle Derived (SD) version of the Heavy Lift Launch Vehicle (HLV) consistently winning during trade studies, which once again pointed at a configuration which used RS-25s as the preference, the Program Requirements Control Board (PRCB) took action to protect the engines.

While NASA’s “White House-aligned” leadership continued to avoid pressing forward with the confirmation of the SD HLV SLS configuration, the PRCB stepped in to “preserve the SSME flight engines for future Agency use” (L2 Link to Presentation)- adding to a previous action to slow down the Transition and Retirement (T&R) of the contractor ability to manufacture flight spares for the RS-25s.

The PRCB also provided the approval for the orbiters to gain Replica Shuttle Main Engines (RSMEs) – previously scrapped nozzles installed via an adaptor – for when the vehicles retire to exhibitions, freeing up the flight flown SSMEs.

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

With the orbiters also donating large elements of their Main Propulsion System (MPS) – a heavily related collection of plumbing and lines – to the SLS program, a large amount of the HLV’s core guts will be from the orbiters for at least the testing/pathfinder stage, through to the opening launches.

The ongoing trades taking place at the Marshall Space Flight Center (MSFC) are also working through the core’s configuration for the three versions of the SLS, namely the Block I – 70mt, the Block IA – 100mt, and the Block II – 130mt vehicles.

Technically, SLS could launch with three, four or five RS-25s from the outset. However, with three engines on the core, and the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration – using four engines would allow the vehicle to fly fully fueled in all configurations, saving the extra calculations/testing for an under-filled three engine core.

Per the meetings – as much as no decision has been made at this time ahead of the key Systems Requirements Review (SRR) and Systems Design Review (SDR) – it appears four engines on the first stage would be best prescribed for the SLS from the start, per sources.

SLS will naturally evolve after the opening flights of the Block I SLS, with SSME contractor Pratt & Whitney Rocketdyne (PWR) producing RS-25E engines for the rest of the SLS’ lifetime. The RS-25E – based on the reusable SSME (RS-25D) – is expendable and thus requires less long-life hardware items, in turn making it cheaper to produce.
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OV-103/Discovery – The final voyage of the veteran workhorse:

For the final year of the Space Shuttle Program, operations in 2011 began where all Shuttle missions have: in the Vehicle Assembly Building.

After enduring a rollback from LC-39A in late-December 2010, because of cracks on the stringers of her External Tank’s (ET) intertank structure, Space Shuttle orbiter Discovery, OV-103, spent the first month of 2011 in the VAB undergoing ET intertank repairs and strengthening activities while the various NASA centers conducted numerous simulations to nail down the cause of the ET stringer cracks. (L2 Link).

Discovery, the third operational Shuttle orbiter and fourth overall Shuttle orbiter constructed by NASA, was preparing for her 39th and final mission in November 2010 when the stringer crack issue presented itself during the mission’s first launch attempt on November 5, 2010.

Following the discovery of this issue, NASA mission managers refused to set a launch date for the flight in a concerted effort to allow the engineering analysis teams to have the time they needed to properly and safely address the issue without feeling a push toward launch fever. 

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

On January 4, NASA identified the potential root cause for the stringer issue – a mottling on the stringers themselves.

As noted by an investigation report, “Some material used for the stringers was found to be ‘mottled,’ with a different surface appearance than the standard material. Testing revealed this mottled material had lower fracture toughness than the nominal material and exhibited unstable crack growth.

“All of the cracks found during tanking as well as cracks fixed during manufacturing were located on stringers made with this mottled material.”

Furthermore, engineers were finally able to recreate the stringer crack failure seen on Discovery’s ET using the stringers from the partially-built ET-139 at the Michoud Assembly Facility (MAF).

By January 6, the all-powerful Program Requirements Control Board (PRCB) had directed teams to proceed forward with the radius block modification on well over 100 of Discovery’s tank stringers – a decision that further emphasized the drive for safety and understanding over launch date pressure.

With that, Discovery’s launch date was penciled in for February 24 or 25 as negotiations began with other ISS partners – specifically ESA (the European Space Agency) which was planning to dock their ATV-2 vehicle to the ISS at the same time that Discovery would now be ready for launch.

After negotiations concluded, it was decided that ATV-2′s docking on the morning of February 24 would permit the launch of Discovery later that day – something that had previously been ruled out due to communication and on-orbit requirements of the two vehicles and the ISS crew.

But as repairs to Discovery’s stringers kicked into high gear and things looked to be settling out for the veteran space vehicle, STS-133/Discovery crewmember Tim Kopra was injured and had to be removed from the mission as a result.

Within three days, Steve Bowen was assigned to the mission as Tim Kopra’s replacement, and NASA, in making the crewmember switch announcement, made it clear that Bowen’s experience on the previous Shuttle mission, STS-132/Atlantis, meant that he would need only moderate refresher training to perform the EVA activities originally assigned to Kopra.

As a result, Discovery would keep her February 24 NET launch date, and Nicole Stott and Al Drew would split the Flight Engineering responsibilities for launch and entry that Kopra was originally assigned.

By the end of January, Discovery’s stringers were modified and reviews had cleared the vehicle to return to the launch pad.

On the night of January 31/February 1 – the 8th anniversary of the loss of sister Columbia – Discovery was returned to the launch pad for what would be the 20th post-Columbia mission.

By all would not be as smooth sailing as hoped. The GUCP once again showed its temperamental side by failing an ambient leak check at the pad. (L2 Link).

The GUCP was disassembled, inspected, its two-part flight seals replaced, and reassembled. Subsequent ambient leak checks revealed a healthy GUCP, and all pad activities continued on schedule.

On February 15, the Ariane 5 launch vehicle successfully delivered the ATV-2 ESA resupply vehicle for the ISS into orbit – paving the way for a 24 February docking of ATV-2 to ISS and subsequent launch of Discovery later that same day.

With all approvals in place, the three-day countdown began on Monday, February 21.

The countdown proceeded flawlessly, and fueling of Discovery’s External Tank yielded absolutely no issues with the modified stringers or the GUCP.

Following the successful docking of ATV-2 to the ISS on the morning of 24 February, final preparations continued, the crew boarded Discovery, and the Countdown reached T-9mins and holding.

And then… it happened: the Eastern Range suffered a computer anomaly that prevented them from seeing the necessary safety information readouts from Discovery.

As the Range team worked the issue, the minutes continued to tick toward the end of the day’s short launch window.

At T-9mins and holding, Launch Director Mike Leinbach and his team decided to pick up the count and then hold at T-5mins if the Range issue had not yet been resolved.

With concurrence from all involved, Discovery’s Commander, Steve Lindsey, told the millions watching to “get ready to witness the majesty and the power of the Shuttle Discovery as she lifts off one more time.”

The launch countdown picked up and was indeed held at T-5mins for just over 3mins as the Range continued to work the issue.

In a heart-pounded final seconds, the launch team moved, with esteem calm and professionalism, to resume the countdown in time once the Range issue was cleared.

In the end, the team successfully resumed the countdown with only 1 second of LOX drain back hold time – the limiting launch window factor that day – remaining before a scrub would have had to have been called for the day.

But that one second was all that was needed.

To thunderous applause, numerous tears, an on-hand spectator number reaching close to a quarter of million people, and under crystal clear skies, the Space Shuttle Discovery began the display she and her sisters were best known for when she gracefully lifted off from LC-39A at the Kennedy Space Center at 1653.24 EST and made one final reach for the stars.

A true tribute to America’s space workforce, Discovery executed a flawless ascent and safely, successfully, and with pride delivered her six-member crew and mission payload to LEO.

Discovery docked to the ISS for the final time on 26 February 2011.

With her docking, a historic milestone was reached for the ISS – a complete family moment with the ISS supporting all of its support vehicles: Shuttle, Soyuz, Progress, HTV, and ATV.

During the mission, Discovery delivered thousands of pounds of external spares via the Express Logistics Carrier ELC-4 and thousands of pounds of internal supplies for the Space Station via the newly minted Permanent Multipurpose Module (PMM) Leonardo – a former Multi-Purpose Logistics Module (MPLM).

The addition of PMM Leonardo marked the final, permanent, pressurized module to be delivered to the ISS by the Space Shuttle fleet and NASA.

After nearly nine days of joint-docked operations, the ISS bid a final farewell to Orbiter Discovery after 13 missions to the orbital outpost.

On March 9, just before 12-noon, Discovery announced her triumphant return to the Kennedy Space Center before flying effortlessly over her Florida home and easing down onto Runway 15 at 11:58:14 EST.

By the time Discovery rolled to a stop on the Florida spaceport runway, she had achieved the distinction of having spent a cumulative total of 365 days (a full year) in space.

She was also the oldest-surviving Shuttle orbiter in the fleet upon completion of her final mission as well as the first Space Shuttle orbiter to successfully complete every single one of her missions – including all three Return to Flight missions following the losses of her big sisters Challenger and Columbia.

Discovery’s service to the human race began on 30 August 1984 with the launch of the STS-41D mission and ended on 9 March 2011 having lasted 26 years 6 months 6 days and 39 missions.

OV-105/Endeavour - An emotional high for the baby of the fleet:

For Endeavour, the 2011 calendar year began with direct knock-on effects from the on-going stringer crack issue of her sister Discovery’s ET.

The Space Shuttle Endeavour, the fifth and final space-worthy orbiter and sixth and final overall Space Shuttle orbiter constructed by NASA, began 2011 in her OPF-2 home as NASA hammered out a fix to the stringer issue on the External Tank.

Following the identification of root cause of the issue and implementation of the radius block modification, NASA made the decision to modify ET-122 – the External Tank Endeavour was to use on her final mission – despite the fact that ET-122 was an earlier-constructed tank than Discovery’s and was not constructed from the same material batch as Discovery’s mottled stringers were.

Nonetheless, the decision was made to ensure the highest safety factor for Endeavour and her returned-to-service ET.

In many ways, Endeavour’s final journey to space was a story of perseverance and rising above the odds.

Endeavour herself had always been a symbol of triumph from the throes of tragedy as her existence is owed entirely to the loss of Challenger, the sister she never knew.

Called upon for multiple important missions during her storied career, Endeavour was the Space Shuttle Orbiter that saved the Hubble Space Telescope in 1993 and the Orbiter that began construction of the International Space Station in December 1998 when she launched on the STS-88 mission to join the US’s “Unity” module with Russia’s Zarya module.

For Endeavour’s final mission, her Commander was none other than veteran Shuttle flier Mark E. Kelly – who, like his vehicle, was an amazing source of strength, hope, and inspiration throughout the early months of 2011 and throughout the STS-134 mission.

But the perseverance on STS-134 did not end with Endeavour or her crew.  Despite the fact that the STS-134 mission was the first of the final two missions to be added to the end of the Shuttle manifest (and the first of the final Shuttle missions whose flight was specifically mandated by Congress), her External Tank was a major source of pride for the NASA workforce.

Built in 2002, ET-122 was damaged during the landfall of Hurricane Katrina near the New Orleans MAF construction facility for the tanks. In fact, ET-122 was so damaged by the hurricane that it was completely removed from flight status.

Originally, Endeavour’s mission was supposed to use ET-138 – the final completed External Tank in the numerical sequence.

However, the addition of the STS-335 Launch On Need rescue mission for Endeavour mandated the need for another tank. Rather than complete fabrication and assembly of a new tank, ET-139, the MAF workforce was directed in November 2008 to restore ET-122 to flight status.

In addition to all the hurricane repair work that needed to be made, MAF workers also had to implement most of the RTF (Return To Flight) modifications mandated by NASA in the wake of the Columbia accident.

By early 2011, NASA decided to move ET-122 to STS-134/Endeavour’s mission so that Atlantis, if the STS-335 rescue mission was needed, could fly with a perfectly clean tank instead of the patched-up, but extremely safe, ET-122.

With Endeavour fitted with ET-122 and her SRB set, the entire stack arrived and LC-39A on March 10 with a target April 19 launch to the International Space Station.

With a rather traumatic opening week to her last visit to Pad-A, Endeavour’s flight managers were forced to review TPS damage zones on the baby of the Orbiter fleet after a tool was accidentally dropped from the RSS (Rotating Service Structure) and impacted Endeavour before landing on the zero-level deck of the MLP (Mobile Launch Platform).

The damage was very minor and no repairs were carried out on Endeavour.

At this time, as well, Endeavour was also cleared to proceed toward her April 19 launch date when Russian space officials confirmed that their Soyuz launch would only be slipping to April 4 and not deeper in April like originally thought.

But by the end of March, Russia and NASA were once again into negotiations on Endeavour’s launch date as a conflict between Russia’s Progress M-10M spacecraft and Endeavour’s missions arose.

Endeavour eventually lost the fight and was forced to move to an April 29 launch date – which she continued processing toward despite multiple rounds of adverse weather at the launch pad that triggered evaluations of the stack for storm damage.

Also at this time, NASA managers decided to cancel plans for a Soyuz fly-about of the docked Endeavour/ISS stack because of crew impact concerns should the Soyuz fail to re-dock to the ISS. (L2 Link).

By April 13, NASA formally extended Endeavour’s swan song mission by one day. With a newly extended mission, Endeavour entered what was thought to be her final launch countdown on April 26.

On launch day, as Endeavour’s crew prepared for their journey to the launch pad, an APU-1 heater issue presented itself. Initial attempts to troubleshoot the issue did not prove successful, and Launch Director Mike Leinbach scrubbed the April 29 launch attempt.

In the following week, the APU-1 heater issue was quickly traced to the Aft Load Control Assembly (ALCA-2) box. The ALCA-2 was Removed and Replaced, where a blown driver was subsequently focused on as the cause of the heater issue. (L2 Link).

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

With a new ALCA in place, Endeavour’s launch was retargeted for May 16.

For the final time, the countdown for the launch of Space Shuttle Endeavour began on Friday, May 13.

Thanks to the delay in the launch date, and agreements with Russia to undock the Soyuz TMA-20 for a nominal end of Soyuz mission landing during Endeavour’s docked mission, the formal plan to use the departing Soyuz to capture imagery of the docked Endeavour/ISS stack returned to mission planning.

On May 16, even though the weather looked borderline at best, all launch commit criteria aligned, leading to a final, unanimous “GO” for launch decision.

From the cockpit of Endeavour, Commander Mark Kelly said, “We endeavor to build a better life than the generation before and we endeavor to be a united nation. It is in our DNA to reach for the stars and explore. We must not stop.”

And mere minutes later, under overcast, grey, dreary skies, the Space Shuttle Endeavour roared to life for the 27th and final time as she thundered from the launch pad to begin her 25th and final voyage.

To many on the ground, including the launch team, Endeavour seemed to take just a little longer than normal to rise from the launch pad, turn, and begin her historic final mission to space – giving the 500,000 to 750,000 people in personal attendance the feeling of being able to see her for just a bit longer in all her glory.

Her launch was a moment of historical coincidence as well. Endeavour lifted off for the final time exactly 19 years to the day (May 16) after she landed to conclude her maiden voyage, the STS-49 mission in May 1992.

As she had 24 times before, Endeavour dutifully delivered her crew safely to orbit and performed a flawless docking to the ISS two days later.

Her mission marked the delivery of the premiere and exciting Alpha Magnetic Spectrometer to the ISS – an experiment designed to search for evidence of the existence of dark matter, anti-matter, and dark energy in our universe.

The mission also saw the delivery of ELC-3 – the final large delivery of external spares for the ISS – to the Station.

And, as we all remember and cherish, the mission also provided the stunning photography and video of Endeavour docked to the International Space Station from the vantage point of the departing Soyuz spacecraft. (L2 Link to 271 hi res flyaround photos)

But the greatest milestone of all came toward the end of Endeavour’s docked mission: US Assembly Complete of the International Space Station - achieved when Endeavour’s crew transferred and berthed Endeavour’s OBSS (Orbiter Boom Sensor System) to the orbiting outpost.

Thus, Endeavour was the orbiter that began and completed US assembly of the International Space Station.

(Animated image resized from hires/full screen version and sequence photo dumps on L2′s STS-134 Flight Day image section - several hundred megabytes strong – L2 Link.) 

After 11 days 17 hours 41 minutes of docked operations with the ISS, Endeavour bid a fond farewell to her orbital child.

Two days later, under the cover of darkness, Endeavour gallantly swooped down over her Florida home to end her career on 1 June 2011 at 0235 EDT.

To the very end, Endeavour was and always will be an iconic symbol of hope, a ship that inspires pride, awe, the quest for knowledge, and the determination to pick ourselves up and continue forward when adversity would rather us surrender.

After 19 years 24 days 6 hours and 55 minutes of service (May 7, 1992 at 1940 EDT to June 1, 2011 at 0235 EDT), Endeavour officially ended her tenure with the Space Shuttle Program. But she still remains our hope for a new tomorrow, an era when humans will regularly explore the space beyond the confines of our home world and push our boundaries of scientific knowledge and our quest of exploration.

OV-104/Atlantis - The Grand Finale of an American icon:

STS-135: The flight that wasn’t even manifested at the start of 2011.

Included in the NASA Authorization Act of 2011, which was signed into law on 11 October 2010, funding for the STS-135 mission remained in limbo while Congress remained incapable of reaching an agreement on the exact nature of the Fiscal Year 2011 calendar budget.

To this end, NASA continued procurement of mission hardware and software for the STS-335 contingency LON rescue mission which would have been used in the event that Endeavour became disabled during STS-134.

On 20 January 2011, NASA officially changed the mission designation number for STS-335 to STS-135 on internal documentation only (L2 Link), allowing teams to proceed with mission training and planning operations so that the continuing appropriations battle in Washington D.C. would not impact flight operations.

Finally, on 13 February 2011, NASA announced and confirmed that STS-135 would fly to the International Space Station regardless of whether or not appropriations from Congress materialized.

At this point, STS-135 became an officially manifested flight, making it one of the quickest missions to go from manifestation to liftoff in Shuttle Program history.

Undergoing a near one-year OPF-1 flow for STS-335/135, Space Shuttle orbiter Atlantis was mated to her ET/SRB stack.

Arriving at the launch pad at the same time as her sister Endeavour landed a few miles away to complete her last mission on June 1, Atlantis began a one month eight day pad flow.

On 15 June,  a tanking test was performed on the Atlantis/STS-135 stack to confirm a solid fix to Atlantis’s Tank’s stringers – which underwent the same modifications as Discovery’s and Endeavour’s tanks had.

The Tanking Test revealed a healthy tank and modified stringers while also revealing a hydrogen fuel valve issue in Main Engine #3 that, if it had occurred on launch day, would have resulted in a multi-day scrub.

Replacement of the valve was completed on 21 June, just one day after Atlantis’s payload was installed into her payload bay.

Despite a dismal weather forecast with only a 40 percent chance of acceptable weather, NASA launch managers decided to proceed with the launch attempt on 8 July.

Tanking operations began right on time at 0201 EDT and wrapped up three hours later with no issue.

In fact, Atlantis performed flawlessly during her countdown, with the only concern being the weather.

One hour before the scheduled liftoff, weather conditions improved and went GREEN, falling within Launch Commit Criteria rules. However, post-flight launch weather rules governing Return To Launch Site (RTLS) abort weather requirements could not be satisfied by the strict by-the-word standards.

However, the commitment clause for “Good Sense” allowed Launch Integration Manager Mike Moses to issue a formal waiver for the RTLS weather restrictions – giving all stations a GO status for launch – since the weather violation would have cleared by the time of an RTLS landing.

After Launch Director Mike Leinbach wished the crew “Good luck … on the final flight of this true American icon,” the countdown resumed and proceeded nominally from T-9mins to T-34seconds.

At T-34seconds, the Ground Launch Sequencer issued an automated hold at T-31seconds and inhibited Atlantis’s onboard computers from taking control of the countdown.

Prior to this, the final mission of the Space Shuttle to the ISS, the last time a Shuttle launch countdown was held at T-31secs was on the STS-88 mission – the very first Shuttle mission to ISS.

For Atlantis and STS-135, the hold was issued due to the failed indication of a complete retraction and latch of the Gaseous Oxygen vent arm.

The launch control team, one final time, demonstrated their extreme commitment to safety and professionalism as they calmly worked through the issue and used close circuit TV cameras at the launch pad to verify that the GOX vent arm was indeed fully retract and latched against the FSS (Fixed Service Structure) – thus confirming that the failed retraction and latching indication was a sensor error.

The glitch was ironic in many ways, as the GOX vent arm had never given the launch team an issue during the 150+ countdown retractions it was placed through during the life of the Program.

Furthermore, the GOX vent arm was a complete afterthought for the Shuttle Program and was only installed on the FSS after pad validation testing using test Shuttle Enterprise in 1979 revealed the need for the arm and vent system to prevent the build-up of dangerous ice at the top of the External Tank during the countdown.

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

With the issue resolved, the launch team released the hold, and Atlantis’s onboard computers took control of the vehicle and countdown. The time was 11:29:03.9 EDT on 8 July 2011.

In front of a world-wide audience and crowd of one million people at the Kennedy Space Center and surrounding cities and beaches, the Space Shuttle Atlantis came to life, majestically rose from her seaside launch pad, stretched her wings one final time, and went transonic as she punched through the cloud deck and disappeared from view – leaving only the sound of her engines as evidence of her flexing her muscles for the last time.

Atlantis, like her sisters, delivered her crew safely to orbit and docked to the ISS for the final time on 10 July 2011.

The mission saw the Atlantis crew deliver thousands of pounds of internal spares and supplies to the Station – stockpiling the outpost for several years to come.

The mission also delivered the Robotics Refueling Depot to the station, an external experiment deigned to help test robotic refueling technologies for future spacecraft and satellites.

On the final full day of docked operations, Atlantis Commander Chris Ferguson – at the farewell ceremony on the ISS – presented the ISS crew with a small American flag that was flown on the STS-1 mission by Shuttle Columbia on April 12-14, 1981.

The flag was fastened to the inner wall of the ISS and flanked by the STS-1 and STS-135 mission patches – a symbolic gesture signaling the end of the Shuttle program.

On July 19, Atlantis undocked from the ISS and performed a modified flyaround maneuver of the Space Station.

As she backed away from ISS for the last time, Atlantis silently slipped into the darkness of orbital night, the lights turning off on the historic program.

On July 21, Atlantis navigated her way through the fierce outer atmosphere of Earth, taking aim on the Kennedy Space Center for a pre-dawn landing on runway 15.

(Animation created from some of the 114 hi res photos (all available in L2) taken by Mike Fossum on the ISS)

Less than 10 minutes before landing, the ISS made a breath-taking visual pass directly over the Kennedy Space Center in a final salute to the Shuttle Program, heralding Atlantis’s arrival to her permanent home city.

At 05:57:54, Atlantis descended from the darkness and touched her wheels to the pavement at the Shuttle Landing Facility for an emotional finale to her legacy and the legacy of the Space Shuttle Program.

Upon “wheels stop,” the final Shuttle Commander thanked all the men and women who worked on the program and the vehicles over the preceding 30+ years. And in a touching moment, Commander Ferguson also thanked the five flight vehicles themselves for protecting their crews and enabling the expansion of our knowledge and quest for science.

Less than 30 minutes after landing, Atlantis fell silent for the final time.

It was over.
 
Final Reflections on a legend:

With that final Shuttle landing came a moment of joy, sadness, grief, prolonged contemplation, but above all PRIDE in an amazingly complex set of vehicles that inspired countless numbers around the world, flew more people to space than any other spacecraft thus far (and for many, many decades to come), and helped bridge the gap between nations and forge unprecedented alliances in space.

For 30 years, 3 months, 8 days, 22 hours and 57 minutes (April 12, 1981 at 0700EDT to July 21, 2011 at 0557 EDT), the five space-worthy Shuttle orbiters spent a combined total of 1,332 days 1 hour and 36 minutes in space, completing 21,152 orbits of Earth over 548.2 million miles.

All five Shuttle orbiters deployed a combined total of 66 satellites, completed 46 rendezvous with an orbital space station (9 to MIR and 37 to ISS), and carried a combined total of 827 crewmembers (some more than once) into space.

For the final breakdown:

Discovery (OV-103): 39 missions; 365days 12hrs 53mins in space; 5,830 orbits of Earth; 148.2 million miles travelled; 31 satellites deployed (including the Hubble Space Telescope); 14 space station dockings; 252 crewmembers.

Atlantis (OV-104): 33 missions; 305days 7hrs 47mins in space; 4,848 orbits of Earth; 125.9 million miles travelled; 14 satellites deployed; 19 space station dockings (a world-wide record she will keep for decades to come); 207 crewmembers.

Columbia (OV-102): 28 missions; 300days 17hours 41mins in space; 4,808 orbits of Earth; 125.5 million miles travelled; 8 satellites deployed; 160 crewmembers.

Endeavour (OV-105): 25 missions; 299days 3hrs 19mins in space; 4,671 orbits of Earth; 122.8 million miles travelled; 3 satellites deployed; 12 space station dockings and one space station rendezvous and grapple; 148 crewmembers.

Challenger (OV-099): 10 missions; 62days 7hrs 56mins in space; 995 orbits of Earth; 25.8 million miles travelled; 10 satellites deployed; 60 crewmembers.

And while the Shuttles’ missions are behind them, and their engines and APUs forever silent, we wish them and all who have flown aboard them, and all who have worked on them, and all who dedicated theirs lives to making them fly Godspeed in whatever the future may hold.

The Space Shuttle Program, the five orbiters, and their dedicated workforce leave behind an unprecedented legacy of achievement – and a legacy that must never be forgotten, a legacy where all were taught by example “To strive, to seek, to find, and not to yield.”

But moreover, the five Shuttle orbiters made a thousands-strong workforce incredibly proud.

To all of the NASA engineers, all of the astronauts, the entire NASA workforce (including those contractually employed by Pratt & Whitney, Boeing, ATK, Lockheed, USA), and all those whose names we never heard but nonetheless worked silently and many times without recognition in support of a program that you whole-heartedly believed in, we give you our resounding thanks and gratitude.

Without you, this program would not have been what it was.

The Shuttle program has come to an end, but the legacy of the program and those who worked and flew aboard the Shuttle, as well as those who will continue the dream of human space exploration, will forever carry on.

And so, for the final time, to Enterprise (1977-1985), Columbia (1981-2003), Challenger (1983-1986), Discovery (1984-2011), Atlantis (1985-2011), and Endeavour (1992-2011), you will always have our eternal thanks and gratitude for all that you have enabled the human race to learn and discover about not only the universe and our home planet, but also about ourselves and our ability to work together to achieve common and mutually-supportive objectives.

It was an incredible journey. And those of us who were a part of this great program, no matter how small a part, will never forget a single part of it or the Orbiters and people who made it all possible.

Thank you.

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

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

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

(Images: Via Larry Sullivan and Brian Papke, MaxQ Entertainment/NASASpaceflight.com, L2 and L2 presentations and NASA. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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SRB BI-144 flight IFA and Squawk review:

In all, post-flight inspections of the twin SRBs used to propel Shuttle orbiter Discovery toward space on February 24 of this year turned in a smashingly clean performance across the board. 16 IFA presentations are available to download on L2.

Only seven squawks were noted on the STS-133 SRB IFA review – one of which gained classification as an In-Flight Anomaly.

For this one IFA, the presentation notes, “Squawk 133-001: Loss of Video for ET Observation and Main Parachute Deployment Cameras.”

The anomaly occurred on the Right Hand (RH) SRB’s Data Acquisition System (DAS) and resulted in no ET video observation and only partial parachute video capture. “VCR started recording after frustum separation and main parachute deployment,” notes the IFA review.

The video recording began approximately 6secs before the first parachute disreef and ended abruptly 18secs after slash down into the Atlantic.

The IFA classification was declared by the SRB post-flight inspection team to document the failed video capture; an Anomaly Resolution Team (ART) was subsequently formed to further investigate the failure.

To this end, initial testing revealed an intermittent “electrical connection between [the] LANC/Control-L adapter and LANC shorting plug” as well as “contamination on pins and sockets.”

The ART determined that the contamination’s cause was two-fold: the adapter potting material leaked around “hollow rolled pins” and particles were likely loosened during previous flights.

For STS-134/Endeavour, this issue will be corrected via the fabrication of new LANC adapters and shortening plugs. The same procedure will also be used for STS-135/Atlantis.  The LANC adapter hollow pins will also be replaced with solid pins, and pre-potting sealing techniques will be used to prevent leakage.

Thus, the SRB system is cleared for flight on STS-134 and subsequent flight due to the replacement of the discrepant hardware and the fact that video recording of the ET and of parachute deployment is only a Crit III mandate.

Aside from this sole IFA, the six remaining items noted in the SRB IFA presentation for STS-133 included an impact indent on the forward portion of the Froth-Pak foam on the External Tank Attachment (ETA) ring.

According to the IFA presentation, “Indent on forward surface and located at 330-degrees.” The indent measured 0.25 inches in diameter and 0.5 inches in depth – an indication of “potential secondary debris.”

The expected (or calculated) debris generation and impact tolerance was within specification, and the most likely cause of the debris was ice.

No sampling of the impact area was requested; the impact had no effect on SRB hardware or booster performance.

Likewise, a suspect area of ETA Ring Froth-Pak “foam pop-off” had no impact on booster hardware performance. The three areas of foam pop-off (all on the RH SRB) occurred at 45-degrees, 290-degrees, and 330-degrees – with the 45-degrees pop-off carrying the heaviest weight at 0.0013 lbm.

A review of RH SRB ETA foam processing found that all pop-off areas had received seal coat application. Furthermore, these types of liberations have been seen on numerous previous flights; the liberation mechanism is understood to be void delta-P loading.

For STS-134/Endeavour, the application process of the ETA foam has been changed and “clarified trimming requirements and eliminated seal coat” updates have been placed into effect.

The third SRB squawk from STS-133/Discovery relates to corroded Bipod Strut Assembly End Rods. In all, five of the 12 Bipod Strut Assembly End Rods were observed to have corroded (two on the LH SRB and three on the RH frustum). These particular Rods were not expected to corrode.

Despite the corrosion, the structural integrity of the Rods was found to be unaffected since the corrosion was only surface-level. Since the Struts only provide lateral support, they are not a concern for ascent. Nonetheless, the investigation is still ongoing and the issue is classed as “open” for STS-134.

The fourth squawk was opened to document an inconsistent installation of the Frustum CDFA (Confined Detonating Fuse Assembly). “Observed CDFA bundle crossing structure member with and without aluminum tape,” notes the IFA presentation.

“Drawing note requires tape to prevent cuts in CDFA braid, to maintain acceptable bend radius requirements, or to ensure a snug fit in clamps.”

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

Initial investigations showed that this inconsistency could have been a result of a misinterpretation of a general note v. flag note with tape callout in the frustum CDFA installation rules.

Closeout photos show similar inconsistencies on STS-134′s and STS-135′s RH frustums.

However, there is no technical concern over these inconsistencies as there are multiple layers of protection within the CDFA design. However, as noted by last week’s SSP FRR (Space Shuttle Program Flight Readiness Review) SRB presentation (available for download on L2), this is still considered an “open” item by the SRB community and NASA.

Similarly, the SRB IFA document for STS-133/Discovery documents the incorrect installation of a Frustum Flotation Foam Block.

“Flotation block F/N 22 installed in F/N 21 location.” While the flotation foam blocks are cut differently, primarily to allow the F/N 22 block to accommodate a Frustum bracket, the F/N 21 location does not include a Frustum bracket, so the error was not flagged upon installation.

The presentation notes that the foam blocks were likely “kitted incorrectly at refurbishment and subsequently installed incorrectly.”

Lastly, corroded coupling nuts on the Aft Tunnel Cable Connectors were discovered post-flight. The corrosion was found on both ends of the cable and was not previously documented as a Problem Report.

Squawks of this nature have been taken on “multiple previous flights.” The corrosion had no effect on the cable’s functionality, although investigations into the connector date of manufacture and condition are underway. This issue is still classed as “open” as of the SSP FRR for STS-134.

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

Furthermore, of particular note for STS-134/Endeavour is the fact that this flight will represent a “decrease in risk due to alternate Phase II Fuel Pump implementation on 4 of 4 locations.”

RSRM motor set 112 STS-133 IFA review:

Following on from the impressive performance of the SRB systems from STS-133, the performance of the RSRM systems was “excellent,” as stated by ATK – with no recorded IFAs at this time and only four squawks.

According to the RSRM IFA presentation, available for download on L2, “4 squawks have been written and have been reviewed for PRACA and IFA applicability per NSTS (National Space Transportation System) 08126: LH Center FJPS RT-455 Separation, RH Aft Exit Cone/Nozzle Join 1 Foreign Material, Pink Foreign Material in the RH Nozzle-to-Case Joint, and LH Igniter Chamber Discoloration Gasket Foot Print Area.”

The first issue was noted as: Left Hard Center FJPS (Field Joint Protection System) RT-445 Separation at 305-degrees.

The location and appearance of the remaining FJPS material indicates that the damage was caused during SRB descent.

“On the exposed RT445 to case bondline, separation was noted, extending circumferentially along the FJPS in both directions.” The separation ended approximately 6 inches from the impact site.

“Thermo-structural analysis shows that an extreme bounding condition would maintain positive margins through ascent and separation,” notes the presentation. No flight concern was identified for this issue.

The second squawk dealt with the presence of foreign material on RH Joint 1′s primary O-ring. “Foreign material (fiber/hard) observed during the removal of RH primary O-ring. A witness mark was present in the grease outside of seal footprint; no witness mark/impression was seen on the O-ring surface (indicates material was not in seal area).”

The material in question was partially encapsulated in RTV backfill, which means it was present in the assembled joint and not introduced to the area upon SRB disassembly.

The material was later determined to be a hair, 1-millimeter in diameter.

Furthermore, no issues were observed with the primary or secondary O-rings or the sealing systems. All pre-flight leaks checks were within family. The mostly likely introduction of the hair was during KSC mating operations which do not occur in a clean-room environment.

The errant hair does not affect flight safety rationale for STS-134 and subsequent flight.

The penultimate squawk for STS-133′s RSRMs was for a pink foreign material found in the RH booster’s Nozzle-to-Case joint. “Foreign material was observed on the fixed housing near the 180-degree axial bolt through hole location.”

Analysis determined the material to be polyethylene, with the most-likely source of introduction being processing materials.

The material was clearly present since assembly and was located outside of the joint seal area. Each joint is leak checked after assembly to “ensure integrity of the seal. No mechanism exists for contamination to migrate into seal area after joint assembly and leak test.”

Finally, the last RSRM issue from STS-133 was a discoloration of the LH Igniter Chamber Gasket Footprint Area. “Discoloration was observed on the igniter chamber seal surfaces, intermittently full circumference,” notes the RSRM IFA review presentation.

Analysis showed that the discoloration was not corrosion or caused by exposure to hot gas, which eliminates pre-flight and in-flight conditions.

“Likely cause is post-fire heat soak causing deposition of gasket rubber on steel or heat effects on the grease used during assembly.”

This type of discoloration has been noted on “several previous igniter chambers.”

(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Refer to STS-133 L2 section for the IFA presentations. Images used: Larry Sullivan MaxQ Entertainment/NASASpaceflight.com and L2 Presentations).

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Discovery Post Career Latest:

Officially tagged as Transition and Retirement (T&R) operations, Discovery still has many more months of work to undergo at KSC, including one more trip to the Vehicle Assembly Building (VAB).

She headed back to her OPF with applause and tears from many of the crowd gathered at the space center last week, but it was notably pure professionalism from her workforce – in a sign of respect for the orbiter which many of her engineers regard as highly as the astronauts. 

Even official documentation shows the love that is embedded into the workforce for the veteran orbiter, as they prepare her for one more final flight, this time to a place of honor at an exhibition.

“Discovery (is) back on the ground and ready to begin her final processing flow. Although none of us are ready to put Discovery into retirement, the time has come for us to share her with the public,” noted one deservicing note (L2). “The official decision for where Discovery will be displayed has yet to be made, but we are anticipating the announcement in mid-April.

“After landing, we will spend approximately a year preparing Discovery to be able to be safely accessed by the public. Many of you may not be intimately familiar with the Transition & Retirement plans for Discovery so I wanted to give a brief description of what will be occurring over the next 11 months.”

Notably, with one Orbiter Processing Facility (OPF) soon to be handed over to what is rumored to be one of the USAF’s X-37Bs, only two OPFs will be available for what will be the deservicing of three orbiters, as Endeavour and Atlantis complete their final missions over the next few months.

As such, Discovery will undergo Down Mission Processing (DMP) work in OPF-2 for two months, during which time she will be stripped of her Orbital Manuevering System (OMS) pods and Forward Reaction Control System (FRCS), prior to being rolled over to High Bay 4 (HB-4) of the VAB. 

“Roll in to OPF-2 (Please note: OPF-3 is being prepared for turnover to a future customer so we will be processing all T&R activities out of OPFs 1 & 2). Spend about two months performing standard Down Mission Processing activities and removing the OMS pods and FRCS,” added the information.

“The OMS Pods and FRCS will be sent to the HMF (Hypergolic Maintenance Facility) for initial safing and then transported to WSTF (White Sands Test Facility, New Mexico) for decommissioning. Roll OV-103 (Discovery) to VAB HB-4 for approximately 1 month of storage while OV-105′s (Endeavour) Down Mission Processing occurs in OPF-2.”

A game of musical chairs will continue with the orbiters, as Discovery then moves to OPF-1 for a series of final T&R activities, which continues to follow a relatively recent plan to use Space Shuttle Main Engine (SSME) simulators, in order to save and preserve Discovery’s own SSMEs for a potential future role with the Space Launch System (SLS) – as was previously revealed by this site.

It was back in October of last year when a Program Requirements Control Board (PRCB) meeting recommended the orbiters should instead gain Replica Shuttle Main Engines (RSMEs) -  previously scrapped nozzles installed via an adaptor – for when all three of the vehicles retire to exhibitions.

However, it remains uncertain that the SLS will be a Shuttle Derived Heavy Lift Launch Vehicle (SD HLV), flying with SSMEs – which would use the current stock of RS-25Ds, before moving to a cheaper expendable RS-25E version. Agency and political evaluations are continuing on the ability to create the SLS both on cost and schedule.

“Once OV-104 (Atlantis) rolls out of OPF-1, OV-103 will roll into OPF-1 to complete the remainder of the T&R flow,” the forward plan for the orbiters continued, “which includes: End State Safing – removing hazardous commodities and components from the vehicle.

Preparation for Display – installing OMS pods, FRCS, and SSME simulators as well as preparing for ferry.

“Display Site Ops – load onto the SCA (Shuttle Carrier Aircraft), ferry to display site, offload from SCA, and perform final display site configuration activities.”

While the orbiters would be rolled to the Shuttle Landing Facility (SLF) to be mated atop of the SCA – not unlike the days where orbiters would be ferried to Palmdale, California, for Major Modification Periods (MMPs) – only KSC and Dryden Flight Research Facility (DFRC) have the Mate-Demate Facility available for the purpose of loading and indeed offloading an orbiter from a SCA.

This would mean the final location for the orbiters would require two large cranes to help them off the SCA, as previously seen when Enterprise was delivered to the Smithsonian National Air and Space Museum in Washington, D.C.

The current plan is expected to see the exhibition swapping the Enterprise test orbiter with the historic Discovery.

It is not known where Enterprise would be relocated to, other than a large amount of engineering evaluations were carried out on her structure, so as to ensure her ability to be ferried to a new location.

The results were deemed to be acceptable, showing the pathfinder was in a better-than-expected condition.

It is possible that the final locations may start to be announced from mid-April, with a battle set to take place to attract one of the national treasures to their city.

For now, Discovery is undergoing the opening work on the T&R plan, which is mainly related to the continued – and usual – safing of the vehicle, following her excellent performance on the STS-133 mission to the International Space Station (ISS).

STS-133 News Articles (over 120 articles): http://www.nasaspaceflight.com/tag/sts-133/

“OV-103 (OPF Bay 2): Roll-in operations are proceeding as planned. Fuel Cell cool down completed and SSME bearing drying has begun. PRSD (Power Reactant Storage and Distributation) Cryogenic Tank drain was completed,” added the NASA Test Director (NTD) report (L2).

“OMS/RCS and OME post-flight operations picked up. OMS trickle purge activation was completed over the weekend. Payload Bay Doors will be opened late Monday. FRCS helium tank vents will be performed late Monday evening.”

Praise for Discovery’s performance, the crew’s over-achievement of their mission objectives, and the safe conclusion to the flight was never lacking from managers, nor has praise for the overall team’s effort both before, during and after the mission, which specifically earned remarks from Space Shuttle Manager (SSP) manager John Shannon.

“Discovery’s landing was an outstanding end to an amazing mission. STS-133 installed the last permanent pressurized module on the ISS, provided a large amount of logistics and critical spares, and positioned the ISS to aggressively pursue its function as a research laboratory,” noted Mr Shannon in an address to the workforce (L2).

“The preparation for this mission really challenged the team. The issues that we had during the initial attempt in November were difficult and time-consuming to solve. The External Tank and Center Engineering teams did a terrific job in developing new testing and analysis methods that demonstrated that the tank was safe to fly. The training of a new crew member late in the flow challenged our schedule.

“Through all of these issues, the team rose to the challenges and made good decisions. I couldn’t have been more proud of the team when Discovery lifted off the pad – we truly “earned” this one through our careful pre-flight work.”

As noted, managers were impressed by the professionalism of Discovery’s teams, as they greeted her on the SLF with the same dedication and attitude she had come to expect during all of her previous missions. Although this was clearly an emotional time, the orbiter crews – despite the looming end to their careers – continue to “finish strong”.
 
“I was really struck by the “business as usual” attitude of the dedicated team that takes care of our Orbiters. Even though this was the last flight for Discovery, there was no visible negative emotion. Instead I saw extreme dedication to making sure that we do the job right and that we preserve this Program’s legacy,” added Mr Shannon.

“It is vitally important that all elements of the program maintain this same attitude for our remaining two launches. We must stay focused, maintain our rigor, and make good decisions. The decisions we make as a team over the next several months will not only preserve the Shuttle legacy, but they will also demonstrate that this team is ready for the next challenge in Human Space Flight.

“To those team members that have flown their last flight with us – You should walk away with your head held very high. You have built and kept safe a unique capability in the most extreme of environments.

“I can only hope that others that come after us will look back at the Space Shuttle team and emulate the dedication, perseverance, and excellence that this team represents. If they do, we will have an outstanding human spaceflight program. For those team members remaining.

“Let’s go finish this program strong.”

(Further articles will follow, as we follow Discovery all the way to the exhibition. L2 members refer to L2′s ongoing coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: Lead: Larry Sullivan/MaxQ Entertainment/NASASpaceflight.com. All other images via L2, bar Ferry and OPF shots – via NASA.gov).

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STS-133 Landing:

Following Flight Day 13′s checkout of the systems Discovery will use to aid her return, the veteran orbiter is scheduled to depart from her Low Earth Orbit (LEO) playground with only 10 MER (Mission Evaluation Room) items to her name – most of which are not system related from an engineering standpoint.

She suffered zero issues that required any level of evaluation from the Mission Management Team (MMT).

The latest of the minor issues came after the power up of Auxiliary Power Unit 1 (APU1) for the checks on the orbiters Flight Control Surfaces (FCS) and the Reaction Control System (RCS) hotfire task – ensuring all 38 of her primary jets are in working order – when a hiccup was noted on ATVC (Ascent Thrust Vector Control) Channel 1′s Power Supply, which failed to restart during cycling.

The space shuttle ascent thrust vector control (ATVC) portion of the flight control system directs the thrust of the three SSMEs (Space Shuttle Main Engines) and the two SRB (Solid Rocket Booster) nozzles to control attitude and trajectory during lift-off and ascent.

Commands from the guidance system are transmitted to the ATVC drivers, which transmit signals proportional to the commands to each servoactuator of the main engines and SRBs.

In the case of STS-133 – and its use during the return to Earth – the ATVC is responsible for repositioning the SSMEs to allow for the drag chute to be deployed without catching on the SSME bells, and also post landing, allowing the SSMEs to position for post flight operations on the Shuttle Landing Facility.

The ATVC in question did soon return to a nominal state, although the system involves four independent flight control system channels and four ATVC channels – meaning the system is quad redundant even in the event of a problem.

With the weather looking great in Florida, the de-orbit burn was given a go for the first KSC landing opportunity, with the deorbit burn following at 1052 EST. Discovery’s landing at KSC was perfect at 1158 EST. 

More will follow, and Discovery’s post flight time at KSC will be covered throughout (next article this week) - refer to the live event thread for live information.

STS-133 News Articles (over 110 articles): http://www.nasaspaceflight.com/tag/sts-133/

Thermal Protection System clearance for reentry:

With Discovery ready to come home, her Thermal Protection System (TPS) is ready to protect her from the scorching 2,500-degree temperatures she will battle as she makes her way to Florida.

To ensure that the TPS is in the best possible condition (health), a team of imagery and TPS experts conducted a thorough and inspiring review of numerous images obtained of Discovery’s RCC (Reinforced Carbon-Carbon) Wing Leading Edge and nose cap panels, flight control surfaces, and underbelly TPS tiles during the first two days of the STS-133 mission.

By Flight Day 6 (FD-6), the DAT (Damage Assessment Team) were able to rule out any major damage to Discovery’s RCC and underbelly tiles – aided through the FD-2 OBSS (Orbiter Boom Sensor System) scans and FD-3 R-bar Pitch Maneuver (RPM) photography by the ISS crew.

This quick clearance of any major or concerning damage locations on Discovery not only highlighted the amazing job of the DAT but also of the Michoud Assembly Facility (MAF) workforce who has been unbelievably successful in eliminating large-scale and potentially damaging foam releases from the External Tank.

To the end, the DAT included in their presentation a specific reference to the foam loss event witnessed at T+3mins 50secs: “No indication of damage at point of initial contact or rebound contact” of External Tank foam. “Based on comparison to previous impact testing, higher impact energy would be required to initiate in-plane tile cracks.”

No in-plane tile cracks were observed on RPM photography.

Moreover, there was only 1 (yes, one) TPS underbelly tile that received very, very, very MINOR scuffing.

In all, only 8 items were recorded for TIIMS evaluation: 2 lower surface features (one TPS tile scuff and one protruding AMES gap filler) and 6 upper surface features (including a protruding gap filler, a nicked OMS pod TPS tile, a Forward RCS thermal barrier protrusion, a tile nick near an RCC panel on the wing tip, the partial loss of a FI blanket, and a slightly lifted FIB sleeve).

For the two lower surface features, the AMES gap filler was quickly identified as one that was installed following the 14th flight of Discovery in the mid-1990s and one that has since flown with her for her last 25 missions.

The gap filler, which is 1.3-inches tall and 3 plies thick, is currently protruding from Discovery’s surrounding TPS tiles by 0.29-inches (+/-0.1-inches) as observed through the assessment of 1000mm images.

All predicted early transitions for this gap filler are bound by the previous Mach 18 assessment. As related by the master FD-6 DAT assessment presentation, available for download on L2, “Thermal bounded by previous analysis that showed transition at Mach 18 acceptable in this area. Partial transition load comparison based on aeroheating heat loads.”

Nonetheless, a “partial transition analysis” was performed with “Mach 5 and Nz2.0-6fps load conditions at Nominal, Mach 18, Mach 21, and Mach 25 heating.”

This testing confirmed that a partial transition will affect areas of Discovery’s right main landing gear door, wing, and aft fuselage but that all safety margins remain well within the positive range.

There is no predicted TPS or structural over temps as a result of this gap filler, and there are no concerns for reentry.

Similarly, the only other lower surface area to gain attention was on one TPS tile.

Labeled as “Damage: 700_2-001,” tile V070-191017-205 was quickly cleared by PDAT. The tile was observed to have damage dimensions of 1.14-inches in length X 0.85-inches in width.

Switching to the upper surface areas of the review, the first TPS tile damage location was noted on the right OMS pod. This tile was found to contain a 1.43-inch long x 0.25-inch wide scar. The site was quickly cleared with “area comparison to on orbit inspection criteria,” notes the master DAT presentation.

Likewise, the last of only three tile damage locations was found to have a 0.99-inch long x 0.23-inch wide defect. Cleared by “comparison to heat load from nearby lower surface tile location,” the area was found to have no damage over the structural bond line and to be thicker than and receive one-fourth of the heating than its comparison tile.

Also affecting the upper surface of Discovery was a protruding gap filler sleeve. “Protrusion limited to OML sleeving of design gap filler” with “17 of 21 inches of stitch line remain intact.”

This protrusion is similar to ones observed on previously flights with the body of the gap filler continuing to seal the tile-to-tile gap, thus maintaining primary sealing.

This particular gap filler was installed in May 2009 using new procedures including an increased pull load requirement and an increased allowable recession.

A potential cause for this gap filler sleeve’s protrusion was preliminarily traced to the removal of an adjacent carrier panel during the right OMS pod’s flow for STS-133.

“Gap filler fabrication process limits propagation of stitch failure,” notes the comprehensive DAT presentation. “Carrier panel installation likely contributed to the anomaly by damaging the stitches and stretching the sleeving.”

The protruding sleeve is not expected to liberate during reentry since ascent loads in this area are three (3) times higher than entry loads.

However, should it liberate, the possibility exists that it could impact the Rudder Speedbrake (RSB).

But even if this unlikely scenario were to play out, the analysis community is highly confident that the RSB would be largely unharmed and that any impact to the RSB would not compromise the crew’s ability to safely land Discovery.

Likewise, the next area of analysis on the upper surface also yielded positive safety margin results for the potential (though unlikely) liberation event of a portion of an FI blanket patch, which is located on the port OMS Pod.

The blanket patch is 1.94-inches thick, and roughly 3-inches x 0.5-inches were observed missing during FD-3 RPM image review.

As noted by the DAT assessment presentation, the blanket will still maintain its insulating properties even in its damaged condition and is not expected to liberate during reentry since the “tear site is heavily coated with Ceramic coating and the blanket is quilt stitched OML to IML.”

This is also a good example of just how minor the items of interest were for the DAT engineers during STS-133.

Again, should the remaining portion of the patch liberate (unlikely), potential damage to the surrounding TPS and the “face sheet/core” of the RSB is possible, but not enough to prevent the perfectly safe execution of landing ops.

The fourth item of interest on Discovery’s upper surface was a frayed patch on the F4R thruster. As noted by the DAT, the frayed thruster patch is protruding by ~0.49-inches, but the “Thermal barrier will continue to provide compression between tile and thruster.”

No liberation or propagation of this damage is expected since ascent loads in the area are twice as high as entry loads.

Lastly, a lifted FIB sleeve was observed on the vehicle. The sleeving is securely and the DAT is confident that it will not liberate during entry since the entire perimeter is stitched through the blanket.

Further articles will follow. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers – for full and extensive live Flight Day coverage during the mission. Images used: All via L2 photo collections (engineering) and L2 STS-133 presentations).

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End of Mission -1 day:

With final clearance of Discovery’s extremely clean Thermal Protection System (TPS) for reentry, Discovery’s STS-133 Flight Crew is spending the day preparing Discovery for her last hurrah in Earth’s atmosphere.

After converting their good ship into an orbital craft following launch on 24 February, Discovery’s crew is repeating the procedures in reverse order, leaving only a few tasks to perform in the hours between wake-up and the Deorbit Burn tomorrow.

For today, Discovery’s crew conducted a pre-programmed series of tests on the vehicle’s Flight Control Surfaces (FCSs) to ensure that they can attain the necessary positions for a nominal reentry profile tomorrow.

Additionally, the crew conducted a “hot fire” test of Discovery’s RCS (Reaction Control System) thrusters. These thrusters will be used during the initial periods of Discovery’s reentry profile to maintain proper vehicle attitude until enough atmospheric pressure will allow the FCSs to take control of Discovery’s attitude commanding.

Following these events, Discovery’s crew will participate in the final on-orbit tribute for the flagship of NASA’s Space Shuttle fleet.

With that, the crew will power down Discovery’s Ku-Band antenna and stow it for reentry.

STS-133 News Articles (over 110 articles): http://www.nasaspaceflight.com/tag/sts-133/

Discovery and STS-133 – A clean ascent ahead of a clean landing:

With such a phenomenal performance on-orbit, a direct link to Discovery’s mission mangers’ ability to extend the mission by two flight days was the launch with as much cryo consumables as possible.

Following PRSD (Power Reactant Storage Distribution) system load on L-2 (Launch -2days), a full quantity of LH2 (Liquid Hydrogen) and LO2 (Liquid Oxygen) was registered in Discovery’s 4 PRSD tank sets.

In all, Discovery launched with 98.8% (90.9lbs) of LH2 in tank 1, 97.9% (90.1lbs) of LH2 in tank 2, 98.8% (90.9lbs) of LH2 in tank 3, and 98.8% (90.9lbs) of LH2 in tank 4. For LO2 quantities, Discovery launched with 95.7% (747lbs) of LO2 in tank 1, 95.2% (744lbs) of LO2 in tank 2, 96.1% and (751lbs) of LO2 in tank 3, and 95.2% (744lbs) of LO2 in tank 4.

According to the Ascent Summary Report, available for download on L2, “The average prelaunch boiloff rates were 0.068 lbm/hr-tank for LH2 and 0.23 lbm/hr-tank for LO2. The PRSD tank boiloff rates were nominal, indicating that the vacuum of each tank annulus is good.”

For the Fuel Cells themselves, which are fed by the PRSD, “Fuel Cell 3, ‘pin sharing’ was observed on cells 41/42 and 95/96 during pre-launch. Pin sharing was observed on these same 2 cell pairs during the Tanking Test and is of negligible impact.”

Likewise, Fuel Cell 2′s hydrogen meter was observed to be “biased high.” However, this condition was also previously seen during the Tanking Test and was also of no consequence for countdown and launch.

Furthermore, an ADTA 2 total temperature bias (on the low end of the scale) was observed during the countdown. In this case, the issue was a known and pre-existing condition, and the measurement in question was not used.

The FSW also experienced a minor issue that was of no consequence to the ascent and initial on-orbit phase of the mission.

“At approximately MET 22:00, IDP 1′s status word 1 had a one bit toggle for one second. This appears to be a telemetry issue rather than a real error.”

Moreover at 17:15:41 EST, “MIAMI showed a ‘Non Critical Error Logged to MSU.’ The MEDS (Multifunctional Electronic Display System) Status Words show the error condition in Status Words (SW)1-3 = 00F0 0000 0000; nominal status is SW1-3 = 0070 0000 0000. This indicates a 1-bit change for one second. The changed bit indicates the Non Critical Error Present bit is set.”

The reason why this issue appears to be solely telemetry-based is because of a lack of change in the other status words at the time as well as the lack of display issues in Discovery’s crew cabin.

The situation could have resulted in a class D error, which is defined in the Ascent Summary Report as an error “where crew action is not required and the correctness of the display is not suspect but warrants archiving for post mission analysis. Note that an indication will be provided to the ground to initiate analysis of the MSU/VM.”

However, this type error can only occur if 20 DAS status changes have been experienced by the IDP when those changes could not be communicated to the GPC (General Purpose Computers).

“If the IDP-to-GPC communication is lost, the MDU (in this case CRT1) would show a Big-X/Poll Fail indication and a GPC I/O Error would be annunciated. Crew reported no such (glaring) anomaly and there was no Downlist indication of a GPC I/O (input/output) Error; therefore, this Category D error can be discounted as the cause for the ‘Non Critical Error Present’ scenario in this preliminary analysis” – further leading preliminary thought to the idea of a telemetry-noise error.

Shifting gears to the GPS (Global Positioning System) navigation aids, “OV-103 GPS receiver (MAGRS-3S) #2 was powered up at @ GMT 055\16:52:58 and was able to obtain valid key shortly afterward. As expected, for the next 2+ hours, GPS #2 remained in PVA (unaided mode) due to erroneous Shuttle Onboard time which still [had] I-Loads with values corresponding to last year’s launch attempt.”

An uplink was performed prior to T0 to correct the onboard time. This resulted in a correction of the disparity between the GPS time and the onboard time to only a 242-millisecond difference and the transition of GPS #2 to INS (valid aiding) mode.

Nonetheless, GPS#2 experienced issues during ascent in terms of maintaining a 4-satellite navigation lock due to blockages from the SRBs and External Tank – an issue that corrected itself following the roll heads-up maneuver at ~T+5mins 45secs.

All in all, Discovery performed a nominal ascent despite the later-than-planned launch time. T0 was registered at 16:53:24 EST with MECO (Main Engine Cutoff) following at 17:02:15 EST.

At liftoff, “Peak to peak lateral acceleration … was about 0.11 g which is less then the value of 0.19 g’s that could indicate a stud hang-up at liftoff. Final evaluation of hold down bolt performance depends on strain gauge analysis and launch pad and booster skirt inspection but there is no early indication of any issues.”

During SRB-powered flight, all SRB performance indications were right down the center line. As noted by the Ascent Summary Report, “SRB performance is indicated to be nominal as shown by a value of +0.092 seconds for TDEL_ADJUST which is within the dead band for Adaptive Guidance and Throttling of +/-0.21 seconds.”

Likewise the first stage throttle bucket was a nominal bucket of 104/104/72/104%. Maximum dynamic pressure was approximately 714 psi based on the L-4hr 50min balloon.

The RCS window protect firing for SRB separation occurred nominally at 16:55:30.1 EST. The total duration of the burn was 2.08 seconds utilizing thrusters F1U, F2U, and F3U.

Likewise, the dual OMS engine assist burn was nominal. Ignition of the OMS engines occurred at 16:55:41.4 EST; shutdown was registered at 16:58:13.6 EST.

Following MECO, a nominal ET separation was observed with all 10 down-firing PRCS (Primary RCS) jets firing.

The ET sep maneuver was a nominal 10 thruster translation that lasted for 7 seconds. The +X maneuver was then performed to specifications at 17:02:17.9 EST. This was a 10 second, 4 thruster translation.

Orbiter pitch-over for ET photography occurred at 17:03:00 EST. OMS-1 was not required and OMS-2 was performed nominally at 17:31:54.2 EST for a duration of 63.4 seconds resulting in a delta-V of 96.5 fps.

With that, Discovery’s ascent was, for all intents and purposes, flawless. A repeat, flawless performance is expected tomorrow as she gracefully descends into Earth’s atmosphere and glides to a landing at her home at the Kennedy Space Center.

(Further articles will follow. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers – for full and extensive live Flight Day coverage during the mission. Images used: Lead and within the article via L2′s large collection of unpublished STS-133 mission photos. Also photos via MaxQ/NASASpaceflight.com and Jacques van Oene, Spacepatches.nl).

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STS-133 Departure:

Discovery’s crew – who had closed the hatches between the Shuttle and Station on Sunday – woke up to a specially recorded version of the original Star Trek theme, which had been re-voiced by actor William Shatner in tribute of Discovery, after gaining the second amount of votes in an online wake up song contest.

“Space, the final frontier. These have been the voyages of the Space Shuttle Discovery,” narrated Shatner – well known for his role as Captain Kirk in the sci-fi show. “Her 30-year mission: To seek out new science. To build new outposts. To bring nations together on the final frontier. To boldly go, and do, what no spacecraft has done before.”

In preparation for undocking, the ISS’ Solar Alpha Rotary Joints (SARJ) were locked, and the four giant arrays were feathered, so as to protect the arrays from plume impingement as Discovery pulses her Reaction Control System (RCS) jets to move gently away from the orbital outpost.

The arrays on both the European ATV-2 (Automated Transfer Vehicle) and those on the Russian segment, were also feathered for the same reason.

In providing the required approval for the undocking, the Mission Management Team (MMT) met to discuss any hardware issues with the veteran orbiter – of which there are none.

“The MMT met briefly today to review the orbiter systems and mission progress. Discovery continues to perform flawlessly and the teams are working no issues. The MMT gave an unanimous go for Undocking,” noted the managerial meeting.

“The MMT was thankful for a superb docked mission. The teams went above and beyond expectations. This is a testament of the outstanding teamwork both up on the ISS/Shuttle complex and the ground. Enjoy the view of the Flyaround!,” added notes in the FD12 Executive Summary.

Led by STS-133 Flight Director Bryan Lunney, Discovery and her crew performed the complex undocking and seperation profile without issue.

“Separation profile designed to minimize plume impingement and propellant usage. Initial separation sequence combines attitude control firings and +Z burns to achieve opening rate,” outlined a STS-133 flight profile presentation (L2).

“ALT DAP (Digital Autopilot) mode with 0.08 sec. on time limit and variable 10 sec. delay required for attitude control. DAP B and 10 sec. intervals required for +Z translations inside 75 ft. Timing and burn size constraints imposed to protect solar arrays of the Russian docked vehicles.

“Prior to 50 ft., single -X jet configuration continues to be used to avoid requiring a new Loads jet-firing  database. 8 degree corridor separation along the +Vbar. Inside 150 ft., ±Y pulses restricted to DAP B. LOWZ between the ranges of 75 ft. and 1000 ft.

“If prop available, a 1 lap Twice Orbital Rate Separation/Flyaround (TORS/TORF) performed for photographic  survey of ISS. Flyaround required to be outside 600 ft. range for plume loads. After TORF, perform Vbar separation sequence.”

As noted, Discovery carried out a full flyaround of the ISS she helped build over the latter years of her 39 mission career, providing an amazing view of a station, which is host to number docked vehicles, such as ATV-2, the Japanese HTV-2, and several Russian vehicles.

There had been some hope for a unique view of the Station with Discovery docked, that was to be provided by a Russian Soyuz “Flyabout” during the docked mission. However, despite what is understood to be split opinion between Russian managers (RSC Energia and Roscosmos), the decision was to opt against the historic event due to the risk of using what is effectively a test flight of an upgraded Soyuz.

With Discovery departing the Station, ISS crewmembers have only a few housekeeping items on their schedule, prior to a well-deserved rest after hosting the STS-133 crew.

“Overview: Shuttle undocking is early in the crew day. The Shuttle crew performs fly-around and late inspection using OBSS. The ISS crew performs standard post undocking activities to stow the BPSMU, depress PMA2 and remove the CO2 remediation ventilation ducting,” noted a Flight Plan Walkthrough document (L2).

“After all the undocking day activities have been complete, the ISS crew is scheduled for a full off duty day.”

Lead by Commander Scott Kelly, the ISS crew gave Discovery a fitting departure from the Station, following up Flight Day 11′s traditional US Navy dedication of “We’re going to miss Discovery. A great ship. We wish her fair winds and following seas (FWAFS),” with a four bell salute to the departing flagship of the fleet.

STS-133 News Articles (over 110 articles): http://www.nasaspaceflight.com/tag/sts-133/

Late Inspections:

Discovery crew still had a busy Flight Day 12, with a several hour task of carrying out Late Inspections on the orbiter’s critical Reinforced Carbon Carbon (RCC) panels and areas of her Thermal Protection System (TPS). This operation mirrored Flight Day 2′s survey via the Orbiter Boom Sensor System (OBSS), providing imagery for the Damage Assessment Team (DAT) to clear the vehicle for Entry.

“TPS Surveys: All RCC (Reinforced Carbon Carbon) is inspected during the OBSS Starboard Wing, Nose Cap, and Port Wing surveys. The two wing surveys also cover most of the areas of the crew cabin. The OMS Pod is inspected using a handheld camera to take pictures from the aft flight deck windows,” noted Flight Readiness Review (FRR) mission outline documentation (L2).

The OBSS survey procedures incorporate the use of supplemental IDC (Digital Camera) images during LDRI (Laser Dynamic Range Imager) scans, thus reducing the likelihood of needing Focused Inspection. The OBSS unberth procedure incorporates the LDRI 3D calibration and the starboard survey the flat field calibration.

Three crewmembers are required continuously during the surveys, two for the SRMS/OBSS ops and one to operate the situational awareness cameras and sensors. Only two crewmembers are required during unberthing and berthing operations (non-laser ops).

There haven’t be any repeat issue with the OBSS cables, following mitigation after STS-132′s issues.

Scans of the entire starboard wing are scheduled first, given they are not easily performed, or are impossible to perform while docked – providing a challenge should a docked late inspection be required. The surveys are scheduled to continue through the night passes, but the crew may elect to pause if the night time visuals are not sufficient.

“The LDRI survey attitude requires no sun within a +/-20 degree field of view (FOV) of the laser bore-sight. Additionally, no sun can be within a 10 degree half-cone directly behind the instrument; however it is highly desired to keep the sun at a 90 degree half cone behind the instrument as long as it’s not directly behind,” added the FRR overview.

The surveys were completed without issue.

In the highly unlikely event of a major problem being found on Discovery’s TPS, the orbiter will be able to return to the ISS under a safe haven scenario, allowing the crew to await rescue from Endeavour next month.

Discovery is currently scheduled to return to Earth on Wednesday, with the opening landing opportunity resulting in touchdown at 11:58am Eastern at the Kennedy Space Center (KSC).

(Further articles will follow. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers – for full and extensive live Flight Day coverage during the mission. Images used: Lead and within the article via L2′s large collection of unpublished STS-133 mission photos. Graphics via L2 presentations).

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STS-133 Latest:

When Discovery began suffering from launch delays, due to problems with her External Tank (ET-137), some people joked the orbiter had conspired with her problematic orange friend from New Orleans, in order to resist her impending retirement date. Ironically, Discovery’s superb performance on orbit has resulted in just that, with two additional docked days added by the Mission Management Team (MMT).

The allowance for the additional docked days on the ISS is based mainly on the performance of the Fuel Cells, as they demand sustenance from the orbiter’s PRSD (Power Reactant Storage and Distributation) tank loads, eased by the help from the Station-to-Shuttle Power Transfer System (SSPTS).

Some achievement, given Discovery had been slightly handicapped by the removal of one of her PRSD tanks ahead of the mission during her processing flow, in order to make allowances for the heavy payload she was tasked with delivering to the International Space Station (ISS).

“The MMT approved an additional day on-orbit at the meeting. The first landing opportunity at KSC is now targeted for Wednesday, March 9 at approximately 11:59 EST,” noted the MMT (L2). “An orbit adjustment is anticipated (in the calculations) and could affect the landing time. The new landing time will be posted once it is available.”

The change to the mission timeline will also allow Discovery to achieve yet another historic milestone, one of being in space for a full one year period over her career of 39 flights.

“The Orbiter Discovery’s performance continues to be outstanding,” opened one of the numerous Mission Evaluation Room (MER) reports (L2) on Discovery’s docked mission, which recently included a reboost of the station via the orbiter’s Reaction Control System (RCS) thrusters.

“The crew started the reboost at 062/14:03:37 GMT (6/16:10:12 MET) and terminated the burn at 062/14:32:26 GMT (6/16:39:01MET). The reboost resulted in a total velocity change of 3.3 feet per second (when including the attitude maneuvers) and an altitude increase of 0.92 nautical miles,” added MER notes.

“The right RCS fuel pressure reached a secondary lockup pressure of 263 psia eight hours before the reboost. Following reboost, fuel pressure dropped down to 248 psia. Leak rate will be recalculated after right pod stabilization.”

Although classed as an extremely minor issue, with zero mission impact, the Right RCS Fuel Helium Primary Regulator Creep is the only MER item which can be classed as related to Discovery’s primary hardware. It will continue to be monitored, as it was during the nominal reboost.

“RRCS Fuel primary reg creep continues to be monitored. Eight hours prior to reboost activity, leakage appeared to stop while pressure was at 263 (secondary Lock up pressure). Following Reboost, ullage pressure was at 248 psia. At this time the pod environment is still stabilizing therefore leak rate will not be calculated.”

At the latest count on MER documentation, 25 of 38 primary thrusters have been fired. All required RCS thrusters will be fired – as planned – during the routine checkouts on EOM-1 (End Of Mission -1 day), as the crew prepare to take Discovery back through the atmosphere one final time.

Before that historic return takes place, the crew still have a large amount of work to do on Station, as the goal of leaving the giant laboratory in the best possible configuration continues to be achieved.

With the two extra docked days, the strain on post STS-133 stage operations is being greatly reduced, with the advantage of six extra crewmembers aiding the outfitting of the newly delivered PMM (Permanent Multipurpose Module) Leonardo.

Although there is a large amount of public, media – and event Presidential – interest in seeing the crew rush into the unpacking of the newest member of the ISS team – Robonaut 2 (R2) – the primary goal of outfitting includes the transfer of launch hardware used to protect the PMM’s cargo from the stresses of Discovery’s ride uphill.

The materials include foam packaging, which is being transferred to the HTV-2, ahead of its planned departure from the ISS for a pre-programmed entry into a disposal corridor. Supplies from the HTV-2 also have to be transferred via carefully choreographed procedures, in order to maintain the correct center of gravity in the modules.

These operations continued on Flight Day 10, as work elsewhere on the Station took place, relating to maintenance on the Oxygen Generation Assembly (OGA), which has been waiting for the arrival of Discovery to deliever a remediation kit, whilst providing a ride home to Earth for the OGA’s hydrogen dome in Discovery’s middeck.

Work also took place on the Lab Carbon Dioxide Removal Assembly (CDRA), while the Russians also evaluated problems with their own CO2 scrubber – the Vozdukh – which once again failed late on Flight Day 9.

Once Discovery departs the orbital outpost, she’ll be leaving the Station with a parting donation of spare oxygen. Although it is hard to calculate exactly how many pounds of O2 the Station will be left with – due to changes in tank pressures relating to solar beta angles the ISS flies through – the Station will be left in a very healthy situation.

“On the math from the Environmental Control and Life Support System (ECLSS) officer, we’ll leave with the O2 tanks full on ISS when Discovery departs,” noted ISS Lead Flight Director Royce Renfrew at the latest Mission Status Briefing on Flight Day 9.

The crew are also tasked with adding to the ISS’ water supplies, with the usual shuttle mission task of filling Contingency Water Containers (CWCs). According to MER status, two of the CWC bags were filled with water and iodine on FD 8 as an example of the operation. CWC-I number 7 was filled with 41.4 lbm water and CWC-I number 8 was filled with 42.7 lbm water.

Saturday was the last full day the STS-133 crew will spend on the ISS, as they prepare for their farewells and hatch closure between the two vehicles on Sunday (Flight Day 11). Discovery is scheduled to undock from the ISS at 6:03am Central on Flight Day 12.

(Numerous articles will follow. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers – which is now into full and extensive live Flight Day coverage during the mission. Images used: Lead via NASA.gov. Graphics via L2).

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