Post-STS-135 OV-104 Nose Cap damage:

As part of the standard landing-day procedures, a quick assessment of orbiter Atlantis’s Thermal Protection System (TPS) was made after her successful return to the Kennedy Space Center after the 12-day capstone mission for the Space Shuttle Program.

During this runway TPS inspection, an unexpected damage site was found on Atlantis’s nose cap RCC (Reinforced Carbon-Carbon) panel where it adjoins the RCC chin strap.

As noted by the MOD (Mission Operations Directorate) presentation – available for download on L2 – “OV-104′s Nose Cap expansion seal on the R/H side was noted to have SiC damage during evaluation on the runway post landing.”

The damage was documented to be 0.3 inches in width and 1.3 inches in length.

Furthermore, “Carbon fibers were exposed and visible with a 7x hand lens. x30 – x100 magnification did not reveal oxidation of the carbon fibers.”

The presentation specifically notes that the damage to STS-135/Atlantis was completely unrelated to the identified root cause of the RCC spallation issue studied for the fleet’s Wing Leading Edge RCC panel joggle regions a few year ago.

Specifically, this SiC damage was of the same variety as noted on a previous flight of Atlantis – her STS-115 mission in September 2006 which marked her return to active duty following the resumption of Space Shuttle missions in July 2005.

Post-flight analysis and damage assessment for STS-135 indicates that the SiC coating did not liberate during flight but after Atlantis had touched down on runway 15.

While the liberated SiC coating could not be found on the runway and recovered for analysis, there was “no evidence of visible oxidation to the black carbon substrate” – evidence that supports a post-landing SiC liberation event.

The post-landing damage site was not in an area of the TPS that had been previously repaired, and all pre-flight Infrared Thermography images revealed no subsurface damages or flaws to the region during Atlantis’ OPF (Orbiter Processing Facility) flow toward STS-135.

In fact, the presentation notes that “Previous thermography of the area revealed ‘no blistering or anything that would have brought about a visual inspection.’”

Thus, it is believed that the damage was “due to mechanical loading induced by a minimum gap condition.”

The chin panel to nose cap gap was recorded pre-flight to be 0.010 inches, well inside the 0.016 – 0.086 inches requirement.

The post-flight measurements ranged from 0.010 inches to 0.020 inches.

Additionally, during post-flight gap measurements, “a piece of the seal easily liberated when accidently touched with a scale during gap measurement.”

The Leading Edge Structure Subsystem (LESS) Principal Review Team (PRT) found that the expansion seals in the nose-cap-to-chin-strap region likely shifted at some point in Atlantis’s processing after the initial measurements were taken or shifted during flight.

A review of Atlantis vehicle processing for this chin panel and RCC nose cap area showed documented work to remove and then re-install the chin strap during Atlantis’s OPF flow toward STS-132 – her penultimate flight.

The chin strap and RCC nose cap performed perfectly during STS-132.

The LESS PRT thus found that events during Atlantis’s reentry likely contributed and ultimately caused the SiC liberation.

During reentry on July 21, 2011, the chin panel to nose cap gap likely closed up due to RCC expansion from thermal effects, resulting in contact at this localized area that initiated a stress riser and caused a SiC coating crack.

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

Then, late in the reentry process, the “Type A sealant” likely started to solidify and fused the nose cap and chin panel together. At landing, the “heat soak” reached the STR and opened up the chin panel and nose cap gap.

When this happened, the “Type A sealant pulled the SiC chip away from the nose cap expansion seal causing the event.”

Therefore, the team concluded that the damage was the result of a minimum gap condition that existed between Atlantis’s nose cap RCC and chin strap RCC, and that the damage was “unrelated to the infamous WLE RCC Root cause spallation failure mode observed at the joggle region.”

The recommendation was then made to close the investigation with no change to the root cause team’s recommendations or SSP’s accepted risk.

The damage is not a concern or constraint for Atlantis’s display activities or “previous RCC root cause risk acceptance.”

The option does exist, however, to further study this issue for three to five years via current SSP funding.

To read about Atlantis and her sisters – from birth, processing, every single mission, through to retirement, click here for the links:
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Click here for the amazing MaxQ Entertainment STS-135 Mission Review Music Video:
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(Images: Via L2 presentation and L2 Photo Database.)

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STS-135 Latest:

For Wednesday, Atlantis’ 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.

APU-1 (Auxiliary Power Unit) was used to power the hydraulic systems, as Atlantis flapped her wings one final time on orbit, accompanied by the usual couple of pieces of liberating debris – otherwise known as pieces of ice, which can build up on the orbiter during their travels in the cold of space.

“FCS C/O was performed with APU/HYD System 1. The FCS C/O was nominal. Flight Controls is GO for Entry Ops: All APU 1 parameters were nominal during the FCS checkout run,” noted the Mission Evaluation Room (MER) via update presentations (L2).

“APU 1 start occurred at 201:05:16:36. The APU 1 FCS C/O run duration was 4 minutes 26 seconds, with shutdown at 201:05:21:02. Due to the short APU runtime, APU lube oil spray cooling was not required. The maximum APU lube oil outlet temperature was 206 degrees F and the maximum oil return temperature (WSB out temp) post APU shutdown was 191 degrees F.

“All Elevon Actuator Switching Valves and the RSB (Rudder Speed Brake) Switching Valve were verified to configure to the proper positions following APU 1 start (RSB PDU Switching Valve in “Primary” and all four Elevon Switching Valves to “Standby 1″). Priority valve cracking time was 0.338 seconds (spec 1 sec). The HYD System 1 bootstrap accumulator was 2336 psia prior APU 1 start and re-seat pressure was approximately 2848 psia.”

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

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

As expected, no issues were recorded with the L5L vernier jet, which had previously been noted as suffering from a minor pressure drop. Even if this thruster had failed, there would have been no mission impact as a result.

“RCS Hotfire Procedure was initiated at 201/06:04:25 GMT and terminated at 201/06:12:53 GMT,” added the MER. “All 38 RCS jets were fired at least once for at least 0.320 seconds per pulse. All thrusters have now been fired. No anomalies occurred.”

The unsung heroes of orbiter safety since Return To Flight (RTF) – the Damage Assessment Team (DAT) – also wrapped up their work with the mission by evaluating the Late Inspection imagery. As expected, they found no items of concern with Atlantis’ heatshield.

“The mission continues to proceed nominally. RCC (Reinforced Carbon Carbon) Level 2 imagery screening was completed overnight with no major issues identified,” noted the NASA Test Director (NTD) report (L2), prior to a peer review which allowed the Mission Management Team (MMT) to clear Atlantis for the return home.

Interestingly, and in a sign of just how seriously the teams take the health of the orbiter’s TPS, the imagery team were tasked with an action to look into a debris event during launch – even after the orbiter was known to have suffered no damage – in order to determine if any noticeable events on camera footage correlated with the WLEIDS (Wing Leading Edge Impact Detection System) Case A1.

That “Case A1″ detection by the WLEIDS was not of any concern. However, imagery experts at the Marshall Space Flight Center (MSFC) appear to have found a match to the event which was registered at 109.6 seconds.

Using footage taken from the cameras on the Solid Rocket Boosters (SRBs), a tiny piece of debris is seen “near” the starboard wing at 109.5 seconds, in the general location of the reported WLEIDS trigger. Although there is no conclusive impact of the debris, it is likely to be the cause of the trigger.

The debris is so small, it held no threat of carrying enough mass to cause even cosmetic damage to the RCC panel – which was of course confirmed by the Flight Day 2 Orbiter Boom Sensor System (OBSS) inspections of the Wing Leading Edges.

A completely different debris event was also noticed during the Stage EVA – which was conducted during Atlantis stay at the International Space Station (ISS).

“FOD (Foreign Object Debris) was seen by ground team members as it was leaving the payload bay during EVA1/FD5,” noted one MMT presentation (L2) on the observation. “SRMS (Shuttle Remote Manipulator System) elbow camera was the only recorded view.

“Potential candidates were reviewed by Vehicle, ISS/Payloads, EVA, and Cargo Integration. Identified candidates were not critical items, and were most likely soft goods or tape.”

Teams were able to assess that the FOD was growing larger in the frame of the camera and increasing in speed. They were also able to confirm there wasn’t enough “signature” for item to be metallic.

“This is consistent with a soft material insulator, as speculated at the time of release,” added the presentation. “The state vector has been identified and passed along.”

So a clean and highly reviewed Atlantis now spends her final hours on orbit, as preparations are made for the opening Orbit 200 option of conducting the deorbit burn and starting the trip back to the Kennedy Space Center to mark the end of the Space Shuttle Program (SSP).

Another article will follow for the deorbit burn.

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

(Images: Via L2 content and NASA.gov. Further articles on STS-135 will be produced during and after her mission, driven by L2′s STS-135 Special Section which is following the mission at MMT/MER level, surrounded by a wealth of FRR/PRCB/MER/MMT and SSP documentation/pressentations, videos, images and more.

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GPC-4 Issue:

The crew had entered their sleep period between Flight Day 7 and 8, when Atlantis annunciated the problem with GPC-4 via a master alarm, resulting in Commander Chris Ferguson heading over to the orbiter to evaluate the issue.

The GPC in question was running system management software, although no root cause to the problem has yet been noted. However, it is unlikely to be related to the problem suffered by GPC-3 ahead of docking, when a switch tease related to when the computer was physically turned on during the set expansion task for rendezvous, caused the computer to temporarily join the common set prior to then failing out.

GPC-3 returned to action via the IPL (Initial Program Load) and dump tasks – an effective reload of software into the computer – during the early part of Flight Day 4.

Commander Ferguson spent 45 minutes transferring data from the troublesome computer into GPC-2 – aided by Ground Control (GG) in the Shuttle Flight Control Room (FCR) bypassing an expected period of Loss Of Signal (LOS) by working with with assets at White Sands in New Mexico – before being told he could return to his sleep period.

The crew were then informed they would be awoken 30 minutes later than scheduled on Flight Day 8 due to the interruption.

Updating the latest status of the investigation into the GPC issue, ISS Orbit 3 Flight Director Courtenay McMillan noted more information will be known when the crew begin trobleshooting during the first half of Flight Day 8.

“We don’t know if there will be any impact (to the mission) yet. First thing in the morning there will be some troubleshooting to gain some data and see if we can recover the computer.”

Around eight hours of transfer time will be lost during the troubleshooting, according to FD McMillan – although the crew was already 15 hours ahead of the mission schedule.

However, the troubleshooting did not take long, wih GPC-4 successfully reloaded within a few hours and appears to be stable, as a root cause is evaluated (documentation on L2).

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

TPS clearance overview:

Following an as-always impressive review of launch day imagery, Flight Day 2 (FD-2) TPS inspections of Atlantis via the Orbiter Boom Sensor System (OBSS), FD-2 Hi-Res photography of Atlantis’s OMS pods, and FD-3 R-bar Pitch Maneuver (RPM) photography of Atlantis’s underbelly TPS tiles, the Damage Assessment Team (DAT) have completed their extremely thorough review of Atlantis and cleared her for reentry into Earth’s atmosphere.

With only 5 – yes, count them ONLY 5 – TPS notes, Atlantis/STS-135 will stand in history as being tied with sister Discovery as the second-cleanest orbiter to ever reach orbit: an honor she reached on STS-132 last year with only 4 areas of TPS damage – same as STS-131/Discovery.

The honor of “cleanest” post-launch orbiter in the history of the Space Shuttle Program goes to Endeavour. She made it to orbit on STS-130 with only 3, yes THREE, TPS notes and absolutely NO lower-surface, underbelly TPS tile scuffs, dings, or scrapes.

For Atlantis and STS-135, the DAT identified three (3) FI insulating blanket frays on the port OMS pod, one FI blanket fray on the forward -Y star tracker, and ONLY one underbelly TPS tile damage location.

Launch pad cameras also captured the liberation of one AMES Gap Filler ~3seconds after liftoff from LC-39A last Friday.

On orbit RPM photography of Atlantis by the ISS crew also confirmed mechanical and sensor evidence that both of Atlantis’s ET umbilical doors are properly closed and a good thermal seal present.

Verification of closure of the two ET doors gives this system a PERFECT record throughout the 135 flight history of the Space Shuttle Program.

Even more impressive here is that not only has the ET door closure system worked exactly as designed every single time, but that each and every Shuttle flight crew has undergone training for a contingency EVA to manually close the doors via a spacewalk underneath the Shuttle orbiter in the event that these doors ever failed to close properly.

Atlantis DAT review:

To begin their superb TPS clearance review, the DAT reviewed their characterization of the one TPS tile damage (more of a scuff) location.

As noted by the FD-5 TPS DAT Review presentation, available for download on L2′s dedicated STS-135 documentation database, “Analysis Dimensions: 2.49″ L x 0.40″ W.”

Further analysis showed the cavity more than acceptable for reentry – with a total damage area assessed at 2.5″L x 0.5″W x 0.84″D. Total tile thickness on the affected tile is 1.16″.

Nominal heating on this tile and its underlying structure is expected during reentry, and all aligned and cross-flow case evaluations will remain strongly positive.

Cross-flow case evaluations revealed a conservatively estimated max 263-degree F temperature in the area. The max temp allowed is 350-degrees F.

Thus, this area will not be any concern during reentry next Thursday (July 21).

The remaining four areas of interest for the DAT team were all thermal insulation blankets on the upper surfaces of Atlantis.

The only one of these blanket areas not located on the left OMS pod was on the nose of Atlantis near her -Y star tracker.

“Frayed C/P Blanket Forward of -Y Star Tracker,” notes the DAT presentation.

The damage dimensions are 2.59″L and ~1.13″H. Total blanket thickness is 0.75″ thick, and the blanket is an original build blanket making its first flight.

The damage itself is between two previous stitch and coat repairs. Furthermore, the blanket was built to withstand the spreading of fray damage with quality stitches every inch.

The fray has caused no loss of thermal protection characteristics, and ascent heat loads are significantly higher than entry loads on this area of the vehicle.

No material liberation is expected during reentry, and the area is cleared for entry.

The final three locations of interest were all on the port OMS pod, the first of which being the V070-396377-103 blanket.

Installed on December 19, 2006 during OPF flow processing for STS-117, the blanket is making its 6th flight on Atlantis. The blanket itself is 0.92″ thick.

The blanket edges in this area are stitched together to account for loose OML fabric, and – like the star tracker blanket – the blanket is designed to prevent the spread of a blanket tear.

Ascent heating loads in this area are “significantly higher” than entry loads. There are no thermal protection loses because of the blanket deformation.

No material loss is expected during reentry.

For background on the FI blankets, “sleeving stitching is used for reinforcing blanket attachment to vehicle. Sleeving securely attached and will not liberate,” notes the STS-135 TPS clearance presentation.

Thus, there is no loss of thermal protection from “loose” stitching.

The fourth TPS area examined by DAT was a “small fray/protrusion” on the V070-396377-029 blanket.

Total blanket thickness is 1.26″, and the damaged area is approximately 1.3″L x 0.9″H.

The blanket was installed on September 16, 2010 and is making its first flight on Atlantis.

The presentation notes for this blanket include a reference to “1 MR to accept chart recorder data for 4 hours – s/b 8hours. Hands on evaluation verified no bond anomalies.”

Again, the design of the blanket prevents the propagation of the fray, and all thermal limits are well maintained.

The fifth and final TPS area looked at by the DAT was located right next to an APU exhaust vent on the port-side of Atlantis near her Vertical Stabilizer.

The blanket here was observed to be protruding and frayed near the “aft hole reinforcement sleeving ‘donut.’”

The blanket, which is 0.75″ thick, was installed on July 23, 1999 and is making its 21st flight with Atlantis.

Based on turnaround flow documentation from STS-129 to STS-132, the DAT found that the blanket had damage to its “design stitches and perimeter fabric,” and that this damage was “repaired with additional stitching and C-9 coating.”

The sleeving stitching is “used for reinforcing blanket cutout for penetration hole.”

The blanket is still firmly attached to Atlantis and will not liberate during entry and landing ops next week.

The final TPS item reviewed by the DAT, but not included in the five TPS damage location number, was an AMES Gap Filler liberation event at approximately 3 seconds after liftoff from LC-39A last Friday.

“Identified as protruding ~3 seconds post launch (V070-191011-131 / -132),” notes the TPS DAT presentation.

The gap filler was making its 12th flight on Atlantis and was installed for “out of tolerance gap of 0.085 inches.”

Assessments show that there is no risk of increased heating in this area during reentry.

Thus, all six TPS areas were reviewed by the DAT, and all areas were unanimously recommended for clearance for entry. The Orbiter Project Office reviewed this information and concurred with the assessment to clear the TPS for entry.

The MMT reviewed this data as well and formally cleared the TPS for entry.

Atlantis Trivia:

Three of Atlantis’s four STS-135 crew members made their rookie flights aboard Atlantis: Chris Ferguson (STS-115), Sandy Magnus (STS-112), and Rex Walheim (STS-110).

All three of Rex Walheim’s flights have been aboard the Atlantis: STS-110, STS-122, and STS-135. With this, Rex Walhiem has actually been a member of two of Atlantis’s three “final” trips to the ISS: STS-122 and STS-135.

Sandy Magnus, with her flight on Atlantis/STS-135, is only the third astronaut to fly on all three orbiters (Discovery, Atlantis, and Endeavour) in the post-Columbia timeframe: STS-126/Endeavour (up to ISS), STS-119 (down from ISS), STS-135 (Atlantis).

Steven Bowen (STS-126/Endeavour, STS-132/Atlantis, and STS-133/Discovery) and Garret Reisman (STS-123/Endeavour up to Station, STS-124/Discovery down from Station, and STS-132/Atlantis) are the other two astronauts to have flown aboard all three orbiters in the post-Columbia era.

Atlantis is the only Shuttle orbiter to have had more than one “penultimate” and “final” flight.

Her “penultimate” flights – at the time they were flown and with the addition of STS-135 – are STS-122, STS-129, and STS-132.

Her first-last flight was STS-132. Her final-last flight is STS-135.

Atlantis is the ONLY Space Shuttle orbiter to have never suffered a post-SSME (Space Shuttle Main Engine) start RSLS (redundant Set Launch Sequence) pad abort.

The five post-SSME start RSLS aborts in the Space Shuttle Program were: STS-41D (maiden voyage of Discovery in June 1984 at T-6.4secs), STS-51F (Challenger in July 1985 at T-3secs), STS-55 (Columbia in March 1993 at T-3secs), STS-51 (Discovery in August 1993 at T-3secs), and STS-68 (Endeavour in August 1994 at T-1.9secs).

Finishing her career tied with Discovery as the second-cleanest TPS orbiter ever, it is also notable that Atlantis is also the most TPS damaged orbiter to safely return to Earth.

During her STS-27 mission in December 1988, standard post-launch imagery review revealed that portions of ablative insulation on the right hand Solid Rocket Booster (SRB) nose cone had liberated 85 seconds after liftoff and impacted the right hand side of the Atlantis, causing significant TPS damage.

From the images transmitted during the mission, it was determined that the damage was no more severe than on previous missions.

Upon landing on December 6, 1988, over 700 TPS tiles were found to be damage, and one tile was completely missing.

Luckily, and perhaps the only thing that prevented a burn through at the area of the missing TPS tile and the loss of Atlantis and her flight crew was the fact that the missing tile was located over a dense aluminum mounting plate for the L-band antenna – which provided some degree of “added” protection against a burn through.

Additionally, on the occasion of Atlantis’s real final flight, she has become the only Space Shuttle orbiter to carry an iPhone (smart phone) into orbit – thus linking the most complex machine ever built (the Shuttle orbiter) with a new generation of hand-held computing technology.

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

(Images: Via L2 content, L2′s 600mb STS-135 400mm, 800mm, and 1000mm hi res photo collection – and NASA.gov. Further articles on STS-135 will be produced during and after her mission, driven by L2′s STS-135 Special Section which is following the mission at MMT/MER level, surrounded by a wealth of FRR/PRCB/MER/MMT and SSP documentation/pressentations, videos, images and more.

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STS-135 Update:

This was Atlantis’ 19th docking to a Space Station – based on a total of seven dockings to the Russian space station MIR, and 12 to ISS – placing her in history as the single vehicle with the most space station dockings.

This was also the 36th docking of Shuttle to ISS and occurred on the 37th Shuttle mission to ISS (STS-88/Endeavour did not dock to ISS – after that mission involved the maneuvering of Unity onto the ODS (Orbiter Docking System) with the SRMS (Shuttle Remote Manipulator System) before grappling the Russian module already in orbit and mating it to Unity).

The crew awoke ahead of a busy Flight Day 3 to Mr Blue Sky by the Electric Light Orchestra, played for Atlantis’ commander Chris Ferguson, as Atlantis herself put on a light show via a serious of burns to close in on the ISS.

A minor hiccup was noted during the early part of the Flight Day, when Atlantis’ GPC-3 (General Purpose Computer) suffered a problem. However, this held no impacts for the rendezvous and docking phase of the flight, given the redundancy, and is no concern given it should return to action, along with no further GPC failures expected. Losing two GPCs would be more of a concern.

“During the set expansion for rendezvous, when the GPC3 MODE switch was taken from HALT to STBY, the GPC temporarily joined the common set then failed out of the common set,” noted the Mission Evaluation Room (MER) report.

“The crew reported that the mode switch was in the STBY position and both the MODE and OUTPUT talkbacks were barberpole.”

This was the same GPC which suffered a similar issue during Atlantis’ STS-122 flight, which also included STS-135 mission specialist Rex Walheim, allowing for a quick-witted CAPCOM Steve Robinson to joke “You can draw your own conclusions, but it’s the same GPC, on the same orbiter, and the same MS2.”

With Atlantis arriving on time on the R-Bar underneath the Station, Commander Ferguson took the controls and guided her through the 360 degree backflip, the final time an orbiter will conduct the RPM under the Station they helped to build.

As Atlantis then moved on to the TORVA (Twice Orbital Rate V-bar Approach), the orbiter was placed in front of the Station, smoothly entering final approach, prior to a perfect docking at 10:07 Central time. With leak checks carried out ahead of schedule, the joint crews opened their respective hatches for a 11:47 Central time welcoming ceremony, officially starting the docked phase of the STS-135 mission.

As to when Atlantis will depart, the likelihood the MMT will approve a one day extension is being aided by some excellent cryo management with the orbiter, currently show a margin of 1 day and 3 hours, another increase from the Flight Day 2 status on consumables.

By this time Atlantis docked, the ISS crew had already started to send the massive dump of photographs taken of Atlantis during the RPM to the DAT engineers in Houston.

The hundreds of images consisted of 400mm, 800mm and 1000mm photos (several hundred megabytes of which have already been uploaded on L2′s STS-135 Special Section).

The stock of imagery will be evaluated by the DAT over the next few days, via a Level I, Level II and Peer Review, with an aim to provide a recommendation to the MMT (Mission Management Team) to clear Atlantis for Entry, usually within a few day’s time.

Good news has already been reported to the MMT via the Flight Day 2 opening inspections via the use of the Orbiter Boom Sensor System (OBSS), after all “Regions Of Interest” were passed as no concern for the same entry of Atlantis.

UPDATE: Late on Flight Day 3 the crew were informed that, pending a peer review, the DAT engineers have found no areas which would require a Focused Inspection, confirming the orbiter has a very clean TPS. Only five minor areas will be fully evaluated over the next dat or so.

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

STS-135/Atlantis WLEIDS launch data review:

Following a stunning and emotional climb out of the Kennedy Space Center Friday morning, Space Shuttle Atlantis safely reached orbit on the power of her twin Solid Rocket Boosters (SRBs) and stalwart Space Shuttle Main Engines (SSMEs). Shortly after ascent, data from the Wing Leading Edge Impact Detection System (WLEIDS) revealed a very clean ascent in terms of potential impacts to Atlantis’ delicate WLE RCC panels.

As reported to the Mission Management Team (MMT) in the Launch +12 Hours STS-135 In-Flight WLEIDS Report, Atlantis’ WLEIDS system worked perfectly and registered only two potential impacts – both on the vehicle’s starboard wing.

As noted in the presentation, available for download on L2, “All 96 WLEIDS ascent summary data files was downloaded and down linked successfully. Eight (8) half-second windows of detailed G time histories were downloaded in order to confirm the implication of cases above 1 Grms.”

All background noise and RCC settling levels for STS-135 were in family with background levels observed on previous missions. While there have been no WLEIDS anomalies reported or identified, there was minor “noise” on the port wing 11/12 RCC (Reinforced Carbon-Carbon) panels observed late in the ascent of Atlantis. 

All WLEIDS systems and unites (except for two) activated within 0.15seconds of each other beginning at Main Engine Ignition (MEI) at T-6.6seconds. The remaining two sensor units, numbers 1086 and 110 on the port wing, activated within 0.5seconds of MEI.

On-orbit WLEIDS monitoring for Micro-Meteoroid Orbiting Debris (MMOD) began with port and starboard Group 2 WLEIDS sensors 17hours 48minutes after liftoff.

Overall, the L+12 Hour report revealed one possible impact location/event and one “questionable” indication on the starboard RCC panels of Atlantis during her climb uphill.

There were zero impact triggers on the port wing of Atlantis and zero trigger indications on both her port and starboard Chines. The one confirmed trigger that could indicate a possible impact on Atlantis’ WLE RCC panels occurred on Starboard panel 8.

The sensors on this panel – as well as sensors in the immediate surrounding areas, registered a potential impact event at Mission Elapsed Time (MET) 109.6 seconds – or 1 minute 49.6 seconds after liftoff from Pad 39A.

The impact registered on the WLEIDS with a Grms value of 3.05. This places the trigger in the “probable” category of impact.

Furthermore, all evaluation criteria – Transient, Non-Mission, Shock, Damping, Spectral, and Multi-Sensor – were met by this WLEDIS trigger.

Specifically, these six criteria are defined by the STS-135 L+12 Hour WLEIDS report as: “Transient – Sudden significant elevated response; Non-mission – Not a normal mission event, e.g. global response; Spectral – Sudden significant elevated high frequency response; Shock – Transient with characteristics of a shock response; Damping – Relatively low logarithmic decay rate of response amplitude; Multi-Sensor – Transient corroborated by sensors around indicated panel.”

With all six criteria met, a trigger indication of 3.05 Grms, the data was placed into Category IV of the probability of damage matrix, meaning the probability of damage is between 1/200 and 1/100.

Conversely, the only other WLEIDS trigger during ascent was on starboard RCC panel 20 and contained a registered Grms reading of 1.36.

The event was registered at MET 68.8 seconds – or 1 minute 8.8 seconds after liftoff – and occurred during the Max Q period of flight.

Furthermore, the trigger did not meet all six evaluation criteria. Only four criteria were met: transient, shock, damping, and spectral. WLEDIS data returned “uncertain” information regarding the non-mission and multi-sensor criteria.

However, there are no WELIDS sensors on RCC panels 21 and 22 on both the port and starboard wings, so potential corroborating evidence does not exist since there is no way to gain information outboard of panel 20.

With all this information, the second WLEIDS trigger falls in Category I of the probability of damage matrix, meaning the probability of damage is less than 1/1000.

STS-135/Atlantis L+24 Hour WLEDIS On-orbit data review:

After spending her first day in orbit, Atlantis’ WLEIDS data was once again downloaded and down linked successfully to flight controllers and engineers in Houston.

A review of L+24 Hours WLEIDS data revealed ZERO impact indications across the WLEIDS.

Nonetheless, while there were no impact indications, there was one WLEIDS trigger event at MET 18 hours 16 minutes 00 seconds.

The trigger occurred at the port RCC panels 3 and 4 interface and registered on WLEIDS sensors along the 3/4 RCC panel interface with a Grms value of 0.76, below the “questionable” and “probable” Grms limits for impact potential.

While the indication was low, it did meet five of the six evaluation criteria: transient, non-mission, shock, damping, and spectral.

It did not, however, register across multiple sensors on surrounding panels.

Comprehensive WLIELDS systems/personnel overview:

According to the STS-135 Wing Leading Edge Impact Detection System Overview presentation, available for download on L2, a ground team comprised of three divisions will be responsible for evaluating and report WLEIDS data to the appropriate divisions over the course of the mission.

The three ground team divisions for STS-135/Atlantis are: ES/Structural Engineering (or WLE MER [Mission Evaluation Room]), EV/Government Furnished Equipment (WIS GFE), and DO5/Assembly & Checkout Officer (ACO) Flight Controllers.

The WLE MER team will be further broken-down into two categories: Post-Ascent and On-orbit MMOD monitoring. Specific post-ascent duties will include providing impact summary for TPS assessment and supporting WLE survey inspections and focused inspections.

For the On-orbit MMOD monitoring portion of the flight, the Ground Team will be tasked with providing standalone results for any WLEIDS triggers and supporting late-inspection activities.

System management and evaluation will be the primary task of the WIS GFE group during the STS-135 mission, with a focus on commanding, data processing, battery life estimation, and temperatures of the system.

The DO5/ACO Flight Controllers will be tasked with keeping abreast of and developing crew procedures, overall system cognizance, Ku-Band coverage capability at critical times, anomaly resolution leadership, and system and operation status reporting to the flight crew.

However, none of this would be possible without the numerous hardware elements installed on Atlantis.

In all, 132 accelerometers (66 per wing) and 40 temperature sensors (20 per wing) are mounted behind the first 20 RCC panels on the wing spars of Atlantis.

In turn, 44 sensor units (22 per wing) are located in Atlantis’ wings. Each Sensor Unit, which is designed to gather and process data from accelerometers, has three (3) accelerometers and one temperature sensor attached to it.

Each Sensor Unit contains internal temperature and battery voltage measurements, and the units are grouped together into clusters known as “sensor farms.”

In turn, these Sensor Units will communicate via Radio Frequency (RF) with the Wing Relay Units, of which there are 2 units per wing and one per “sensor farm.”

In each wing, eight Sensor Units (units 1-8) are located on each wing glove “sensor farm” mounting plate. Units 9-22 (14 total units) are located on the wing cavity “sensor farm” mounting plate.

The wing glove “sensor farms” will communicate with their respective Wing Relay Unit on Channel A; the wing cavity “sensor farms” will communicate with their respective Wing Relay Unit on Channel B.

The Wing Relay Units are in turn connected via hardline to the Cabin Relay Units located in middeck cabin locker MA9G.

The Cabin Relay Units (2 + 1 spare) will then communicate the data received by the Wing Relay Units to the Laptop Receiver Unit via RF. The two Laptop Receiver Units will then transmit the data to the primary A31p Laptop which runs the WLES (Wing Leading Edge Sensor) software and stores the data from the Sensor Units.

In all, there are two A31p laptops, one primary and one backup. Only the primary laptop will communicate with the WLES system.

All sensor and relay units have independent battery units; thus, the entire system is not subject to the same power source and can maintain operational status even if one sensor or relay unit’s battery source is depleted prematurely during the mission.

In all, use of the WLEIDS for STS-135/ULF7 began four days before launch when KSC personnel programmed the sensor units with event files. In all, four launch opportunities were programmed into the system with emphasis on Ascent Data Collection and Assessment.

Final verification of battery charges for the system was taken at this time and the system secured in a deactivated mode.

On launch day, the system remained in the deactivated mode until SSME (Space Shuttle Main Engine) ignition at T-6.6 seconds. At this time, Atlantis’ computers triggered the activation of the WLEIDS and all 44 units began collecting 16-bit data at 20,000 samples her second. This continued through MECO (Main Engine Cutoff).

Following MECO, at MET 10 minutes, the sensor units created ascent summary data files before transitioning to on-orbit power-saving “idle” mode.

Four hours after launch, Atlantis’ flight crew set up the LAN (Local Area Network)/OCA (Orbiter Communications Adaptor) system and verified nominal WLES operation.

MCC (Mission Control) then commanded the primary A31p laptop to download all WLEIDS information from the Sensor Units at a rate of 0.4 KB/s. It took take about 1 minute to transfer a single ascent summary file and 1.5 hours to transfer ascent summary data.

After this, the raw data was downlinked to the ground for assessment. Downlink was accomplished through the Ku-Band antenna at a rate of 250 KB/s or 500 KB/s depending on the Ku-Band channel utilized.

Following a review of this data, the Mission Evaluation Room (MER) determined if any additional data should be downlinked. Their determination was that not additional data was needed.

Following the WLEIDS sensor units transition to “idle” mode to preserve battery power through their scheduled deactivation on FD-12, the sensor units will be used to monitor Atlantis for MMOD impacts during both free-flight and docked periods.

This monitoring will be accomplished by placing the sensor units into 2 or 3 monitoring groups per wing. This will enable MCC to rotate through the monitoring groups so that one group is in use for no more than 21hrs at a time.

This will allow for maximization of battery life on the system and, in turn, ensure MMOD monitoring during the highest MMOD risk periods.

A temperature of at least -40-degrees F will be maintained inside each wing structure during the on-orbit operational period of the WLEIDS to ensure proper functionality of the system.

In terms of crew procedures/interaction with the WLES during the flight, there will be three categories of interaction: nominal, off-nominal, and reconfiguration.

For nominal ops, the crew will perform activation and checkout of the system on FD-1; perform rendezvous tools checkout prep and before PILOT OPS; perform WLES recovery ops after docking and undocking; and perform deactivation of the system on FD-12 in preparation for entry and landing.

Off-nominal activities could include Laptop Receiver Unit R&R (Removal and Replacement), Cabin Relay Unit R&R, and Laptop Receiver Unit troubleshooting.

For reconfiguration activities, the crew could have to prepare for laptop transfer to a different location within Atlantis.

For crew actions toward the WLEIDS, both Chris Ferguson and Rex Walheim are trained for WLES operations, and Sandy Magnus has received the WLES ops overview class and can help with troubleshooting.

All WLES procedures are contained within the Orbit Ops Book, and nominal crew WLEIDS activities will take ~40 minutes of crew time.

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

(Images: Via L2 content. Further articles on STS-135 will be produced during and after her mission, driven by L2′s STS-135 Special Section which is following the mission at MMT/MER level, surrounded by a wealth of FRR/PRCB/MER/MMT and SSP documentation/pressentations, videos, images and more.

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

No related posts.

Click here for ENDEAVOUR UNDOCKING AND STORRM OVERVIEW ARTICLE:
http://www.nasaspaceflight.com/2011/05/sts-134-endeavour-storrm-final-farewell-to-iss/

Following the preliminary clearance of all areas of Endeavour’s TPS on FD-5, less the multi-tile gouge area between Endeavour’s Right Hand MLGD (Main Landing Gear Door) and Right Hand ET Umbilical door, Endeavour’s flight crew was instructed to proceed with a focused inspection of the damage location.

Post Undocking TPS Damage Assessment Team (DAT) clearance:

Prior to that, all Damage Assessment Team (DAT) assessment of OBSS (Orbiter Boom Sensor) data and FD3 RPM (R-bar Pitch Maneuver) photography from the ISS confirmed that Endeavour’s two ET umbilical well doors were closed, that there were no upper flight surface protrusion of any kind, and that six of the seven lower damage sites had been cleared without the need for a Focused Inspection (FI).

Following the FI of the three-tile damage location, lovingly dubbed “The Maine” damage because of its remarkable resemblance to the U.S. state of Maine, a detailed characterization of the damage was compiled.

From this, it was confirmed that all tile material was still intact in all areas with no exposed filler bar material; no cracks were identified; the dark area of TPS as seen from RPM imagery was an area of abrupt damage depth change – as expected; all thermal stress assessments revealed no structural overtemp issues for reentry; a “small area” of TPS bondline overtemp would occur during reentry but is acceptable for reentry due to its distribution over three tiles; all TPS and structural margins were well within safety limits for reentry.

Thus, the TPS DAT unanimously recommended clearing Endeavour’s entire Thermal Protection System for reentry in emergency return cases and for nominal EOM (End of Mission) reentry pending the completion of the Docked Late Inspection (DLI).

Click here for the previous five STS-134 DAT TPS Status Articles: http://www.nasaspaceflight.com/tag/tps/

Detailed Focused Inspection damage site clearance overview:

Following the detailed and fascinating Focused Inspection of the “Maine” damage site, photographic and laser measurement data revealed that the damage was 0.89 inches in depth, +/-0.04 inches, and remained above the filler bar.

This means that tile margin exists in all areas of the damage cavity, or what the post-FI inspection presentation – available for download on L2 – classed as a “dense layer.” (View Anaglyph slide left with 3D glasses).

In all, the damage location is 0.89 inches in depth, 2.95 inches in length, and 2.43 inches in width.

In fact, the TPS clearance presentation notes that there are very few areas of missing material and no cracks radiating outward or downward from the main damage site.

Furthermore, views of the damage location obtained from the OBSS’s Laser Dynamic Range Imager (LDRI) confirmed that sections – but not all – of some AMES gap fillers were missing, indicating that the “Impactor had enough energy to damage multi-layer AMES gap filler.”

However, it appears that the AMES gap fillers had an unintended positive consequence as “Adjacent tile damage size [was] reduced by the presence of AMES gap filler.”

In comparison to a similar tile damage event on the STS-118/Endeavour mission, the STS-118 damage was 3.48″ x 2.31″ x 1.12″, was located at Xo 1260 Yo 123 Zo 269, and carried a tile depth of 1.12 inches.

STS-134/Endeavour’s damage was 3.22″ x 2.49″, was located at Xo 1243 Yo 106 Zo 267, and was located on a tile with a thickness of 1.04 inches.

Based on analysis conducted during the STS-118 mission, that mission’s damage was found, based on on-orbit information analysis, to have a Mach 16.7 Boundary Layer Transition (BLT) time. STS-134′s damage is predicted to have a Mach 12 (nominal) BLT time.

All STS-134 FI damage was further found to have baseline aeroheating, BLT, Boundary Layer Wedge, Cavity Heating, Thermal Analysis, Tile Stress, and Stress indicators in Model Category “A” – indicating that “Baselined model used within model limitations or intended use.”

A maximum temperature calculation for the FI damage locations was created, and “Due to flow orientation, assessment [was] performed in both the aligned and cross-flow orientations of the simplified cavity,” notes the TPS DAT clearance overview presentation.

Based on these parameters, a maximum structural temperature of 219-degrees F and a maximum RTV bondline local temperature of 1,194-degrees F are expected during entry on Wednesday morning. The maximum structural temperature allowed is 350-degrees F, leaving high structural margin.

Nonetheless, the total RTV bondline temperature does exceed nominal limits; however, RTV bondline temperature “over 625°F is limited to 6 inches squared distributed over 3 tiles.” For the damage site on STS-134/Endeavour, the aligned flow max temperature is predicted at a modeled rate of 5.75 inches squared with an actual in-flight temp on the critical tile of 4.06 inches squared – both meeting the design requirements.

Likewise, the cross flow max temperature is predicted at a modeled rate of 6.19 inches squared with an actual in-flight temp on the critical tile expected at 3.98 inches squared – again, well within the design criteria.

Therefore, all structural margins remain positive for STS-134 and the OPO (Orbiter Project Office) and DAT unanimously recommended clearing Endeavour’s TPS for entry.

“DAT resolved issues associated with difficulties modeling complex damage, and is in good posture to support STS-135,” notes the overview presentation.

Following this assessment, Endeavour’s TPS was cleared for entry pending the results of the Docked Late Inspection, or DLI.

After completing the DLI, the DAT identified 162 regions of interest (ROI) on the vehicle’s Reinforced Carbon-Carbon wing leading edge panels.

Across the spectrum of flights from STS-121 to STS-133 – excluding STS-114 (no Late Inspection on that mission), STS-124, and STS-132 – the average ROI count was 151, with a high ROI count of 771 on STS-124 (results not included in the average since the mission could not conduct a standard post-launch OBSS inspection) and a low count on STS-133 of 52.

These ROIs were quickly cleared by the DAT and Endeavour’s TPS unanimously and formally cleared for entry.

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

But most importantly, none of this detailed assessment of the “Maine” damage location would have been possible without Endeavour’s trusty OBSS. To this end, NASA created a special presentation on the life and times of the OBSSs over their six years of service to the Space Shuttle Program – from inception, to creation, to first flight, to significant achievements in space.

And from NASA and the OBSS team to the OBSS now permanently affixed to the International Space Station, these parting words reflect the importance of all three booms in their service to the Shuttle program and its courageous astronauts: “As Shuttle says ‘goodbye’ to the OBSS and ‘thank you’ to the sensors for their outstanding service, Station says ‘welcome’ to the EIBA – Enhanced ISS Boom Assembly.

“May the EIBA serve the ISS as well as the OBSS has served Shuttle.

“Farewell, OBSS, and job well done!”

Flight Day 16 – also known as EOM-1 (End Of Mission minus one day) successfully completed the checkout of Endeavour’s Flight Control Surfaces – via the use of APU-1 – prior to a full firing of Endeavour’s Reaction Control System (RCS) thrusters.

Communication checks with ground stations were also deemed to be succesful, which were carried out after entry and landing simulations via the use of a laptop and flight stick.

The crew also recorded – after mission the window in communications – a tribute video for Endeavour, which will be edited and played back sometime on Tuesday.

Next article will be published early on Tuesday.

(Images via L2 presentations, images and content). Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

Related posts:

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

STS-134 DLI:

Normally carried out after undocking, the Late Inspections follow a similar path to that utilized on Flight Day 2, which provide the baseline for the final checks of RCC panels, along with other critical areas of her heatshield, such as the nose cap.

With the data sent down to the ground for the Damage Assessment Team (DAT) to carrying out two levels of reviews into the findings, a final peer review would then be in progress as the DAT inform the Mission Management Team (MMT) with a recommendation Endeavour is in acceptable condition to return home early next week.

As per FD2′s opening inspections, Endeavour is in great shape. Only some minor dings on her belly ramped up the skilful evaluations by the DAT, as they cleared the final area of interest via the Focused Inspection (a full review article on the clearance will follow later in the mission).

The Focused Inspection utilized the OBSS sensor suite, which is again in action with the Docked Late Inspections. Unlike the FD2 inspections, additional challenges for the robotic teams resulted in an expansive plan for the positioning and translation of the OBSS – relating to clearances between the boom’s movements and the Station hardware Endeavour is docked with.

Notably, DLI debuted with Endeavour during STS-123, as the OBSS was left on Station for use by Discovery on the following mission. This handover related to the clearances with lofting the Japanese Kibo Laboratory with Discovery, leaving no space for the OBSS to be berthed in the payload bay.

A DLI was also used by Discovery herself during STS-131, when a Ku Band failure on the orbiter called for the utilization of ISS Ku assets to downlink the vast amounts of imagery to the DAT in Houston.

The lessons learned from both of the previous DLIs allowed for extra confidence in the planning for STS-134′s inspections.

“Structural interference from the ISS prevents running the standard FD 2 autosequences, so we will utilize docked inspection autosequences developed for STS-134/ULF-6,” noted one of several presentations on STS-131 DLI plan (L2).

“These autosequences provide full LDRI (Laser Dynamic Range Imager) coverage of RCC (Reinforced Carbon Carbon), but limited IDC (Digital Camera) coverage (IDC data will not be collected).”

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

With changes to the inspection process, the DLI will take around one hour or so longer than standard Late Inspections – which are nominally a five hour process.

“Timing: We estimate the surveys will take 5-6 hours to complete: STBD (Starboard): around 2.75 hrs. NOSE: around 1 hr. PORT: around 1.5 hr. If the attitude maneuvers are required (to and from +ZVV), each will require around 1 hr for attitude handovers and the maneuvers.”

Outlining the proposed procedure, a preliminary inspection plan was produced in the main DLI presentation, starting with the Starboard Wing.

“STBD Survey: The stbd survey is divided into two parts. In the first part, the SRMS (Shuttle Remote Manipulator System)/OBSS reach over the PLB (Payload Bay) to scan the upper, forward, and some lower RCC zones. In the second part, the SRMS/OBSS reaches under the PLB to scan some lower RCC zones,” noted the presentation.

“In order to get full coverage, we will have to accept several close clearances between both the OBSS-RCC. Minimum clearance between the OBSS and RCC is expected to be 42 inches with several good available views (RSC, RMS Elbow, etc). These tight clearances require the stbd survey be heavily segmented, with several pause points with LDRI pan/tilt reconfigs as well as a few places where data is taken via a pan/tilt survey.”

Once the Starboard wing survey is complete, clearances for the two additional elements of inspections – the Port Wing and the Nose Cap – are far less restricted.

“NOSE and PORT Surveys: In the survey, the OBSS ‘wraps’ around the front of the vehicle and requires less than 5 ft clearance to completely survey the stbd side of the nose cap. The port survey requires less than 5 ft clearance to the port PLBD for some upper RCC surfaces.”

With the final plan to be sent up to the crew to allow for training briefs – which included CGI videos of the projected paths the SRMS and OBSS will take – other considerations include the attitude of the ISS during the surveys, due to the potential of LDRI shutdowns caused by the sun shining into the sensor.

The LDRI (Laser Dynamic Range Imager) is one of the stars of the OBSS sensor suite, and was involved in the earlier Focused Inspection evaluation on the small area of damage on Endeavour’s belly.

Incidentally, the LDRI raised the latest issue at the Mission Evaluation Room (MER), cited as “MER-11: LDRI Mode Timers Not Incrementing”.

“STS-134 LDRI Mode Timers: Noticed on GMT 144 that LDRI mode timers did not increment as expected. Nominally Mode 2 timer should be accumulating at least 24 hours each day. During the last mode check (GMT 144:16:14-144:16:20) the delta operational hours for all modes was 1.04 hours. Mode 2 Timer should have increased almost 42 hours,” noted a JSC Engineering presentation (L2).

“Most likely cause is an inadvertent power cycle or left in Mode 1. If LDRI is in any Mode and abruptly loses power, then all those hours of usage in that Mode are lost. Further, when the LDRI is firsts powered on, it goes into Mode 1.

“Request to perform a test of the LDRI (emulating LDRI calibration) to aid in determining the impacts, if any, to the LDRI. Data processing under very tight turn around schedule (24 hrs) due to EVA 4.”

That test was carried out at noon (Central) on Wednesday, via commands on the ground, given the crew was sleeping.

The results are being evaluated in relation to any unlikely impacts to the work to handover the OBSS to the ISS and conduct work to install it as the Integrated Boom Assembly (IBA) – its new role after supporting shuttle.

A MER report (L2) noted that similar event occurred during STS-123, after the LDRI was left in Mode 6 for 56 hrs and it resulted in a latent image. Additionally, we did not get live flat field for late inspection. These compounded events resulted in a 5 hour delay in processing the data.”

EVA-4 will be the focus of Flight Day 12, which will involve Mike Fincke and Greg Chamitoff installing the OBSS at the Starboard 0/Starboard 1 truss interface, prior to swapping out of the OBSS grapple fixtures, retrieval of the Port 6 truss segment power and data grapple fixture, and release of retention systems on the Dextre spare robotic arm.

(Images via L2 presentations, videos and images. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

Related posts:

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

EVA-2: SARJ, Dextre, and ammonia coolant work:

After beginning their day at 2126 EDT, Endeavour’s flight crew got right to work preparing for the mission’s second EVA.

After a 50-minute hygiene break for Drew Feustel (EV-1) and Mike Finke (EV-2), the two returned to the ISS’ Quest Airlock for EVA preps, spacesuit purge, and spacesuit prebreathe activities.

Following Crew lock depressurization, Feustel and Finke took their EMUs (Extravehicular Mobility Units) to battery power - officially beginning EVA-2 for the STS-134 flight, marked at 1:05am Central Time.

After egressing the International Space Station, Feustel and Finke spent the first 30mins of the EVA performing EVA setup activities and translating out the P3/P4 truss. Once there, the spacewalking spent approximately 15mins performing re-routing operations on the P3/P4 truss.

At this point, Feustel and Finke went their separate ways, with Feustel beginning the hour-long process of filling the P5/P6 EAS jumper.

Meanwhile, Finke spent 20 minutes filling the Ammonia Tank Assembly before moving on to the one hour-long task of removing covers on the port SARJ (Solar Alpha Rotary Joint).

Click here for SARJ Articles: http://www.nasaspaceflight.com/tag/sarj/

This cover removal, for which Drew Feustel will join Mike Finke after he finishes his P5/P6 EAS jumper work, will precede lubrication activities of the SARJ itself - which is a large rotary wheel designed to turn the outer portions of the Station’s truss so that the eight solar array sets can track the sun and collect as much solar energy as possible to power the Station.

During cover removal, Finke noted at least two bolts flew off the cover when they were removed with his Pistol Grip Tool (PGT). Amazingly, Finke caught both bolts as they popped out. “The bolt flew off, I have it in my hand,” noted Finke, with Feustel responding with a “Wow!”

A loose washer was also observed, floating undernearth the cover. Efforts are being made to secure the washer, which – had it entered the SARJ mechanism – could have caused potential problems for moving hardware associated with the Race Ring.

As a result of the observations – which may point to the bolts and washers on the covers being worn down by removal – only half of the covers are being removed for what became partial lube task, and the PGT was used for only part of the cover removal, with the bolts then being removed by hand.

As first noted in mid-2007 on the starboard SARJ, evaluations into problems with the starboard SARJ began after vibrations and power fluctuations were noted by ground controllers and ISS crewmembers, which led to an inspection of the hardware during STS-120′s EVAs in October 2007.

With observations of metallic shavings - consisting of 1505 Nitride material - on the hardware, engineers concluded the debris was the result of grinding on the Race Rings.

With a similar issue then noted on the port SARJ, concerns grew with the starboard SARJ when Mike Fossum observed a depression, or pit, on the Race Ring during his EVA inspection on STS-124 in June 2008.

Plans were then created to replace the Trundle Bearings Assemblies (TBAs) and grease/lube the Race Ring during STS-126′s EVAs. The results were highly encouraging.

As noted by managers in an update after the STS-126 TBA replacement and Race Ring lubrication, “Status briefing on the initial quick look results of the Starboard SARJ rotations and disturbances seen after the ring was lubricated and the TBAs were changed out: The disturbances seen by starboard SARJ motion have greatly decreased based on the two orbits of autotrack that were performed immediately post R&R.

“The team requested an extended autotrack to obtain more data and determine if the disturbances drop even lower after a long period of operation and distribution of the grease due to rotation.”

Managers then created a forward plan to lubricate the Race Rings of both SARJs over Shuttle missions throughout 2009 and 2010 - with one of those planned flights (STS-134) eventually finding itself in 2011.

After cover removals are complete, Feustel was tasked with taking detailed photographs of the SARJ and collect samples for analysis once Endeavour returns to Earth. However, camera issues were noted, so it’s unknown how many useful photos were taken.

Following directly from the SARJ cover removals, Mike Finke was tasked with the first of two SARJ lubrication activities for the EVA. By now, the EVA was running late due to the bolt issue with the covers, leading to a “big picture” plan to extend the EVA by another hour - as both spacewalkers said they felt good to continue.

Meanwhile, Feustel left Finke to his work and move on to his EAS setup/vent operation. After this, Feustel turned his attention to cleanup operations for the ammonia vent tools.

Finke completed the first SARJ lubing five minutes as Feustel worked the ammonia tool cleanup task. Finke then moved on to stow the P3/P4 jumpers - during which Feustel joined him for the remainder of the activity.

Feustel moved to the ATA and performed a venting operation while Finke tackled the S1 truss Radiator Grapple Bar Stow Beam operation.

While Finke was performing this 1hr 10min operation, Feustel installed a CLA cover on Dextre, or the Special Purpose Dexterous Manipulator. He then performed a lubing operation on Dextre with the aide of the Station’s Remote Manipulator System arm.

During the S1 Radiator Grapple Bar Stow Beam and Dextre operations, the port SARJ was rotated 200 degrees, a 45 minute operation.

After finishing their two previous activities, Finke and Feustel moved back to the port SARJ and perform the second lubrication of the joint for the EVA.

The two astronauts spent the final part of the EVA reinstalling the SARJ covers, cleaning up their worksite and tools, and translating back to the Quest Airlock to re-enter the ISS.

“That was an awesome EVA,” Commander Kelly noted, as the duo came to the end of their epic EVA, ahead of preparations to get the duo out of their spacesuits. Due to the length of the EVA, the crew moved into their pre-sleep shortly after they rejoin the rest of the crew.

Flight Day 8 will be mainly an off duty day. Monday will also mark the historic Soyuz “flyabout”, with the next article focusing on the once-in-a-lifetime event.

TPS Clearance Overview:

Following Endeavour’s brilliant ascent on Monday morning, information on the health OV-105′s Thermal Protection System (TPS) began pouring in from Endeavour’s computers, with the first indication of health coming from the Launch +12hrs (L+12 hours) Wing Leading Edge Impact Detection System (WLEIDS) report.

According to the L+12hrs WLEIDS executive summary (L2), “All WLEIDS ascent summary data was downloaded and down linked successfully. Ten (10) half second windows of detailed G time histories were downloaded in order to confirm the implication of cases above 1 Grms.

“In total, there are two indications; one Category IV indication on the starboard wing, and one Category III indication on the port wing. Both indications occurred on the 11/12 interface” - meaning they occurred at the interface region between Reinforced Carbon Carbon (RCC) Wing Leading Edge panels 11 and 12 on both the port and starboard wings.

Furthermore, “Overall, background levels for STS-134 (were) very similar to background levels of previous missions. No data anomalies (were) identified, and all (WLEIDS) units triggered on Main Engine Ignition within 0.13 seconds of each other.”

Both WLE impact indications met all six impact reportable criteria to be considered areas of interest/potential impact indications and not just normal RCC WLE settling “noises” created as the vehicle accelerates through Earth’s dense lower atmosphere.

Of the two potential impact indications, the largest was the indication from the starboard wing - which registered a Grms indication of 2.54 in Damage Likelihood Category IV.  Damage Likelihood Category IV is defined as a damage probability ratio between 1/200 and 1/100.

The second potential impact, the one on the port wing, registered on the WLEIDS with a Grms of 1.34 in Damage Likelihood Category III. This was a double transient event with the first transient falling in Damage Likelihood Category I: a damage probability ratio greater than 1/1000.

The second transient contained a damage probability between 1/500 and 1/200.

Flight Day 2′s (FD-2’s) inspection of the WLE via the Orbiter Boom Sensor System (OBSS) observed absolutely no areas of damage on the RCC at the locations identified as potential impacts sites by the WLEIDS.

The following day, on FD-3, Endeavour performed her customary R-bar Pitch Maneuver (RPM) to allow the crew on the International Space Station to photography her underbelly TPS. (Image used, 125mb “super belly” RPM photo stitch (L2))

Following this maneuver, the TPS Damage Assessment Team (DAT) released a preliminary report on the vehicle’s TPS health during FD-4. “Imagery review complete: ET doors verified closed. Five items on the lower surface have been evaluated - all QA completed. All lower surface tile (superficial) damages - four cleared by PDAT and one by comparison with OOIC.”

No gap filler protrusion were noted during RPM photography image review, and no upper surface discrepancies were identified either. FD-2 inspections confirmed that the T0 umbilical region of Endeavour suffered no damage during T0 umbilical release at liftoff.

However, the FD-4 presentation noted two areas of TPS underbelly damages that could not be cleared by the DAT and might require a Focused Inspection by Endeavour’s crew.

The first location was a multi-tile damage site on the inboard elevon with an estimated 3D damage depth of 0.3 +/-0.1 inches. The damage location itself was 6.52 inches in length x 2.32 inches in width +/-0.15 inches. Total tile thickness in this region is 1.636 inches.

This area, while initially a Focused Inspection candidate, was cleared for reentry by the DAT through an amazing series of analyses that proved that positive structural and thermal margins would be maintained in this region during entry.

Thus, the need to perform a Focused Inspection on this area was eliminated.

(Animated GIF created by NSF member Lee Jay Fingersh via the several hundred hi res RPM images available in L2).

The second area of damage that did eventually require a Focused Inspection was classed as a “large damage site.”

According the FD-4 TPS Subsystems Status presentation - available for download on L2 - “RPM Imagery: Visual indications of RTV (filler bar) and dark line (abrupt change in depth).”

The RPM imagery showed indications of “ledges/drop offs” in the TPS cavity with decreasing TPS tile thickness close to the edge of the tile.

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

Based on RPM imagery, the TPS tile damage depth was estimated at 0.6 inches +/- 0.1 inches with reduced confidence toward the tile edge.

This estimated damage depth corresponded nearly identically to the damage depth prediction on STS-118/Endeavour - the only other occurrence of deep tile damage on an orbiter post-Columbia.

On STS-118, RPM imagery yielded a predicted tile damage depth of 0.5 inches. Upon Focused Inspection of the area, the damage depth was revealed to be around 1.0 inch.

Due to these factors, the DAT and imagery support personnel were split on their interpretation of the RPM data. As such, the DAT formally recommended proceeding with a Focused Inspection of the “large damage site” on Endeavour.

Following the Focused Inspection on Saturday, the TPS DAT and Mission Management Team officially cleared Endeavour’s entire TPS for reentry.

(Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

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STS-134 Focused Inspection:

Following Friday’s successful EVA-1, the crew was set to enjoy a largely off duty day, mixed in with some robotic procedures and preparations for Sunday’s EVA-2.

However, due diligence from the MMT – based on a recommendation from the Damage Assessment Team (DAT) – resulted in a call to use the pre-planned placeholder in the flight plan to carrying out a Focused Inspection on a relatively small area of tile damage, located on the starboard side of Endeavour’s belly, between the Main Landing Gear Door and (MLGD) External Tank Door (ETD).

The damage is historically minor, but due to a need for additional data to be plugged into DAT’s extensive computational analysis models, and less than perfect imagery of the damaged area from Flight Day 3 RPM photography, the FI option is an opportunity to add confidence in what is expected to be full clearance for entry in around 24 hours.

The OBSS instrumentation package – which rides on the end of the 50 foot boom – consists of visual imaging equipment, the Laser Dynamic Range Imager (LDRI), and the Laser Camera System (LCS). The post-Columbia modification has sensors that can resolve at a resolution of few millimeters, and can scan at a rate of about 2.5 inches per second.

Thanks to Neptec’s Laser Camera System (LCS), engineers will gain detailed high resolution images and even a 3D model to provide additional data for their thermal modelling and requirements within hours of the survey.

The Focused Inspection by the OBSS will be one of its final roles with the orbiter, ahead of the Docked Late Inspection (DLI) which will then result in the Canadian superstar being handed over to the ISS for a role as the Integrated Boom Assembly (IBA).

Although imagery requirements were refined in real time, baseline Focused Inspection requirements were provided to the MMT a few days ago, providing some procedural outlines into the dual use of two elements of the OBSS package – namely the LCS and the IDC (Digital Camera).

“Priority Location 1: Large Tile Damage: Damage ID: D-134-RPM-600_2-001. Location: Starboard side between MLGD and ETD. Location X= 1243.85, Y= 106.07 , Z= 267.33. Sensors: LCS and IDC (with LDRI illumination – Mode 6, record LDRI),” outlined a DAT procedure document (L2).

“Requested Views Details: 5 total views are required for damage assessment. The first four of the five views should be optimized for IDC imaging, but LCS data is requested as well. Views 1 thru 3 have IDC/LCS positioned slightly outboard of damage site and pointed inboard (approx 5 degrees off normal).”

Those five total views are all the DAT engineers need for their data requirements, which will refine the dimensions of the damage and should result in not just imagery, but 3D computational models, as was seen during STS-118′s Focused Inspection.

“View #1: IDC approximately 6″forward (-X direction) of damage. View #2: IDC approximately even (X direction) with damage. View #3: IDC approximately 6” aft (+X direction) of damage. View #4: IDC positioned directly above the damage pointing to the damage at normal incidence,” added the DAT overview.

“View #5: LCS positioned directly above the damage pointing to the damage at normal incidence. Need to capture 20” minimum all the way around damage site. IDC is not required for this additional data acquisition.”

The robotics operations also require the crew to follow set instructions on ensuring the imagery taken with the Digital Camera on the end of the OBSS is based on the real-time environment, as the Endeavour/ISS stack race through daylight and darkness on orbit.

“Sensor Package 2 IDC Preferred Parameters: Range: 75” for Views 1 thru 4. Boom Motion: Brakes On plus 90 second dwell before beginning data collection (NO EXERCISE). IDC Scenario: “Black Tile – Day” and “Black Tile – Night”. Crew will select proper file (day or night) per real-time environment,” the requirements added.

“IDC Lighting: Daylight (direct or earthshine) or LDRI illumination at night (daylight is preferred). IDC FOV: Fixed at 16 deg x 9 deg. Notes: The engineering and imagery teams will be satisfied with a range between 66” and 84”. There is some risk that data collected between 60” to 66” or 84” to 120” will be unsatisfactory for this inspection, but it is better than no data at all (note: assume IDC in these ranges is better than ITVC at 60”).

The expansive overview provided the crew with numerous instructions, notably showing that the use of the digital camera will be IDC tasks are the most involving tasks during the Focused Inspection.

“Tasks: Move the sensor package into position. Allow boom motion to dampen out. Pointing can be confirmed by the IDC in “Scan Lo-Res”. If IDC view not used, from the LCC GUI, perform a Quickview scan to verify LCS pointing. Downlink the Desktop Downlink,” the overview notes.

“Stop IDC scan to allow LCS ops. Select the appropriate Detailed Area Scan name (as defined above), and press ‘Start Area Scan’. Restart IDC scan and select the proper scenario file. Activate ‘Acquire Set’ function. Data will finish collecting in approximately 30 seconds.

“Activate the IDC ‘Scan Lo-Res’ feature. Crew adjusts (moves/sizes) the exposure window if necessary. Check MCC. Activate “Scan Hi-Res” feature. Collect IDC data for 30 seconds. Leave the IDC on and collecting data as the boom is moved into the next view. After completion of data take, stop LDRI recorder and select ‘Power Off’ to power down the IDC to safe it from accidental exposure to sunlight.”

The Focused Inspection, which began after some troubleshooting with an associated monitor on the middeck, was completed after 55 minutes.

A similar overview was also provided for the damage on the Inboard Elevon – ahead of DAT engineers clearing it, as expected, for entry.

In fact, with the Reinforced Carbon Carbon (RCC) and all other areas of the orbiter cleared, the final clearance of the Focused Inspection area will result in Endeavour being fully cleared for Entry, pending Docked Late Inspection (DLI) results.

“Focused inspection CHIT (Documentation) developed to assess damage site: D-134-RPM-600_2-001. IDC and LCS sensors will be utilized. IDC will provide details of the tile cavities. No color,” noted a DAT presentation to the MMT (L2).

“LCS will provide point cloud data of the tile cavities and surrounding TPS. Surrounding TPS topography req’d for overlay repair option for 600_2-001. Elevon damage site removed from request based on 3D thermal model and command TPS Stress model utilized on assessment. TPS and Stress tile margins remain positive.”

The additional data will also provide managers – via computational models – with extra confidence the damaged area will still provide – as if fully expected – the protection for the underlying structure, with DAT showing numerous images of the inside of the orbiter in the damage location.

“Structure in damage region is aluminum skin with mechanically attached aluminum stringers and structural fittings. Skin panel thickness is 0.146” constant under damage with minimum thickness 0.114” within 6” inches of damage location,” the always-impressive DAT presentation added.

“Mechanically fastened stringers and fittings provide additional 0.08” to 0.23” structure thickness in portions of the damaged region. Yo105 MID Fuselage Longeron and Xo 1249 Wing Spar provide additional structure mass.”

Although no sub-system components are located on the lower skin in the wing region between Xo1191 and Xo1307 inboard of Yw167, DAT’s recommendation for a Focused Inspection is outlined in their findings.

“Initial analysis indicate that if Filler Bar is exposed, Structure temperatures will exceed 350 degrees F. Structural exceedances of 350 degrees F require detailed assessment. Detailed Stress assessment will not be available prior to Focused Inspection.

“Mitigations to overcome modeling issues for exposed Filler Bar are continuing in preparation for Focused Inspection. Damage Assessment Team split over value of determining crack tile in damage site. Portion of team recommending Focused Inspection regardless of thermal results. DAT recommends execution of Focused Inspection.”

With the FI is complete, engineers on the ground got to work on the data within hours, with Mission Management Team (MMT) chair expecting a 24 hour process to clear the area for Entry. No preparations were carried out for any further action, such as an EVA repair.

UPDATE: However, given the clear margins of safety based on the results of the point cloud data from the FI, the DAT gave a recommendation to clear the area of damage – and as a result the entire vehicle – for entry, with the MMT agreeing with no dissenting opions.

Later in the Flight Day, his Holiness the Pope addressed the astronauts aboard the International Space Station. ESA astronauts Roberto Vittori and Paolo Nespoli and their colleagues talked for 20 minutes with His Holiness Benedict XVI, who was in the Foconi Room of the Vatican Library.

During the call, the Pope asked several questions, and blessed the crew.

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

The crew then completed their proceedure reviews and tool checkouts for the second of four EVAs scheduled for STS-134, which will be the focus of Flight Day 7.

(Images via L2 documentation and videos. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

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EVA-1/FD-5 Overview:

After waking up at 2226 EDT, Endeavour’s crew got right to work preparing for the mission’s first of four spacewalks.

Upon repressurizing the Quest Airlock (where Drew Feustel and Greg Chamitoff spent the night) from its overnight 10.2 psi campout pressure, the spacewalking duo enjoyed a brief hygiene break before re-entering the airlock which was promptly depressurized back to 10.2 psi.

Spacesuit purge was then conducted about two hours after the completion of this hygiene break, and spacesuit pre-breathe commenced shortly after the spacesuit purge was complete.

Following ISS crew wake up, depressurization of the crew lock got underway. Once the crew lock was depressed, the outer hatch was opened and Feustel and Chamitoff took their spacesuits to battery power – officially beginning the EVA.

After exiting the ISS, Feustel and Chamitoff spent about 20mins setting up their various tools. Then, Feustel translated to the MISSE (Materials on ISS Experiment) 7 experiment and removed it from its current location on the Space Station and replace it with the MISSE 8 experiment.

During this time, Chamitoff translated over to the P3 truss where he worked on installing a light onto the CETA cart. After this, Chamitoff translated across the ISS’s Integrated Truss Structure to the Starboard SARJ (Solar Alpha Rotary Joint), where he installed a cover in the SARJ cover 7 position.

Meanwhile, at the tail-end of Chamitoff’s work on the SARJ, Feustel translated over to the P3/P4 truss and began work on ammonia jumper line installation.

Feustel then move on to install another ammonia jumper across the P5/P6 truss while Chamitoff stowed the P4 ammonia jumper.

Feustel next moved on to install the P6 EAS jumper before the spacewalking team tackled the Lab EWC antenna operation. However, due to a problem with Chamitoff’s CO2 sensor, 45 minutes-worth of the task has been moved to EVA-3′s timeline.

Feustel and Chamitoff split up and worked on mating various P3/P4 and P1/P2 connections for the duration of the EVA, which was the last task of the EVA.

EVA cleanup activities followed for Chamitoff, Quick Disconnect tool bag reconfiguration tasks for Feustel. After a total EVA time of 6 hours 19 minutes, Feustel and Chamitoff re-entered the Quest’s crew lock and repressurized the airlock itself.

The crew will then spend the remainder of the day conducting post-EVA servicing operations before heading to bed at 1326 EDT.

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

Endeavour Status:

Endeavour continues to perform extremely well during what is her final scheduled mission for NASA.

Mated with the International Space Station (ISS), the youngest orbiter in the fleet continues to draw power from the Station-to-Shuttle Power Transfer System (SSPTS) without issue, allowing for her cryo margins to provide excellent mission length ability.

“Subsystem performance is nominal. The PRSD (Power Reactant Storage and Distributation) O2/H2 manifold 2 isolation valves were cycled closed for crew sleep at 138:17:51 GMT and reopened at 139:03:55 GMT,” noted the latest status (L2) via the Mission Evaluation Room (MER).

“Oxygen tank 4 pressure continues to increase due to nominal heat leak; the pressure in now at 800 psia. Fuel cell 1 H2 flowmeter continues to read high and erratic (not unusual). The fuel cells continue to operate nominally at low power levels in combination with the SSPTS.

“CRYO Margins (above 16+0+2 day mission) O2 limited: 2 day 4 hours (non-SSPTS). 4 day 14 hours (SSPTS on).”

However, despite the prospect of both a Focused Inspection and a Soyuz Flyabout being included in an already packed mission, the Mission Management Team (MMT) have no plans to extend the mission past the current 16+0+2 duration at this time, mainly in the thanks to the excellent work by the planning team on the ground, according to MMT chair LeRoy Cain.

TPS Status:

While it has to be emphasized there is no risk to the vehicle or her crew, teams evaluated the potential need for a Focused Inspection on Endeavour’s Thermal Protection System (TPS).

Seven areas were flagged via FD3 RPM imagery, requiring the Damage Assessment Team (DAT) to carry out their methodical analysis to evaluate the option of carrying out a Focused Inspection.

They immediately cleared four areas, ahead of a ding on Endeavour’s starboard Main Landing Gear Door (MLGD) also being cleared from any further inspections.

Two areas remained open from an assessment standpoint going into Friday, with one – on the inboard elevon – then cleared during Flight Day 5. The evaluations have been officially tagged as “MER-7 Tile Anomalies”.

“Summary: Imagery review complete. ET (External Tank) doors verified closed. Forward viewing angle and lighting sufficient. Five items on lower surface have been evaluated – All analysis completed. All lower surface tile damages,” noted a DAT overview to the MMT (numerous STS-134 DAT presentations available on L2).

“Seven damages identified. Five of the items have been cleared. Two remaining items in work. No downstream effects.

“No protrusions or upper surface discrepancies identified. No TPS damage identified at T-0 umbilicals.

“Focused Inspection Candidates: Inboard elevon tile damage. Damage depth from 3D measurement: 0.3 +/- 0.1”. Thermal analysis in work; Stress assessment to follow.

(Animated GIF created by NSF member Lee Jay Fingersh via the several hundred hi res RPM images available in L2).

“Large Damage Site. Structural definition complete. Worst case damage prediction assessments in work. Thermal results pending. Stress to follow.”

As explained by Mr Cain via one of his excellent overviews on the vehicle’s status, the DAT engineers expect to clear the inboard elevon damage from the need for a FI, but are less confident on being able to avoid a FI on the remaining area of interest, which is located between the starboard MLG and ET door. Clearing all areas with a FI remains a possibility.

“I feel pretty confident if, in fact, we’re not able to clear it by the morning, when we get the focused inspection data we’ll be able to clear this problem and not have to do anything,” noted Mr Cain on the main area of interest. “But having said that, we’re going to go do whatever is necessary and we’re going to follow the data all the way along.”

Although the ding’s appearance is – as explained by Commander Mark Kelly during on orbit interviews – by no means any worse than previously cleared damage, the photography of the area is slightly inconclusive, which may provide the main reason why a FI is still on the cards.

“RPM Imagery: Visual indications of RTV (filler bar) and dark line (abrupt change in depth). Three Dimensional data: Indications of ‘ledges/drop off’ in cavity. Decreasing thickness as you approach the edge,” added the DAT summary overview to the MMT.

“Three Dimensional Measurements: Maximum depth of damage is 0.6” +/- 0.1”. Reduced confidence as you approach tile edge.

“Historical Three Dimensional Accuracy: Good correlation between on orbit and post flight measurements. Confined to shallower damages (0.4” deep or less). Lone case of deep damage was STS-118. Poor prediction of deep portion (abrupt drop off). Predicted 0.5” VS FI depth of around 1.0” (partially due to shadowing).

“DAT and imagery support personnel split over imagery interpretation. DAT recommends proceeding with planning for FI.”

Work being conducted by the DAT engineers includes the utilization of their many analytical tools, along with their understanding of the underlying structure which the damage tile is designed to protect, and the use of flight history.

“Cavity definition: Utilize limited point cloud data from imagery lab to generate cavity. Create ‘shoe box’ cavity for use in thermal analysis. Two cavities (3-D and bounding 3-D),” was listed as forward work by the DAT on this specific area.

“Aeroheating: Run CFD (Computational Fluid Dynamics) and engineering model to define cavity heating factors. Thermal analysis: Conservative cavity analysis (damage down to dense layer and exposed filler bar).

“Preparing model with more accurate damage dimensions. Stress Analysis. Waiting for Thermal results. Team 4 and repair support sites/personnel. Ready to support if “called up”.”

*UPDATE: DAT recommend Focused Inspection on remaining area of interest.

“Damage Assessment Team split over value of determining crack tile in damage site. Portion of team recommending Focused Inspection regardless of thermal results. DAT recommends execution of Focused Inspection,” noted Flight Day 5 MMT documentation (L2).

MMT concured with this finding.

A new article will be published later tonight overviewing the Focused Inspection plan and updated DAT information via L2 presentions.*

Flight history always plays a major role in TPS assessments, with STS-134′s ding no stranger to Endeavour from both a location, cause and appearance standpoint.

Only inches away from her STS-118 incident in 2007, the tile damage from that mission required a Focused Inspection, prior to being cleared for re-entry – a decision which was shown to be 100 percent correct, with hardly any ill effects observed on either the damaged tile or the underlying structure after examinations on the ground.

As was the case with STS-118, Mr Cain also explained that the damage is unlikely to have been related to a foam liberation event, with footage from the Solid Rocket Booster (SRB) cameras now showing what appears to be an ice liberation from an ironically named Ice Frost Ramp (IFR).

Two events around T+70 seconds have been observed on the footage, one of which is highly likely to have caused the damage on Endeavour’s belly.

With a Focused Inspection confirmed, documentation (L2) had already been drawn up on the procedures for both the Inboard Elevon damage and the aforementioned primary damage site inspections via the Orbiter Boom Sensor System (OBSS). This will now be implemented.

New article for FD6 later tonight/Morning GMT.

(Images via L2 and NASA.gov. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

Related posts:

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STS-134 Latest:

Endeavour is performing admirably on orbit, with her cryo status projections currently showing a healthy margin for her lengthy 16+0+2 day mission, with additional capacity – O2 limited – of two days and three hours baselined, extending further out with the use of her Station-to-Shuttle Power Transfer System (SSPTS) to four days and 12 hours on top of the baselined mission.

With the orbiter now docked to the International Space Station (ISS), she is able to draw power from the orbital outpost, reducing her own Fuel Cell’s dependence on her Power Reactant Storage and Distributation (PRSD) supplies. The SSPTS also aided Discovery’s twice extended STS-133 docked mission, although STS-135 will not be able to benefit from this system, given the SSPTS is not installed on Atlantis.

No additional issues are being tracked by the Mission Evaluation Room (MER) past the five minor items, all of which have no mission impact. In fact, the only additional issue – known as a “funny” – relates to the Multiple Headset Adapter Ports J1 and J2 not transmitting.

Notably, all of the orbiter’s main systems are working as advertised, including the Auxiliary Power Unit (APU) heaters – the subject of troubleshooting during Endeavour’s extended stay at Pad 39A.

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

“All APU subsystems are performing nominally. All heater systems are operating on the A circuit,” noted MER status (L2), which overviewed all systems currently being used by Endeavour, such as the following examples.

“All Life Support systems are performing nominal. O2 repress was successfully completed. Total GN2 Qty: 325.7 lbm Waste Tank Qty: 42.7 percent 73.7 lbm. Total Supply H2O Qty: 451.7 lbm. The flight controls system continues to perform nominally. There are no FSW (Flight Software) issues being worked.”

STS-134 TPS Evaluations:

The main focus for engineers on the ground is the effort to clear Endeavour’s Thermal Protection System (TPS) for entry. The process – carried out by the DAT engineers – begins with ascent footage and data, prior to moving to the scheduled inspections carried out via Flight Day 2′s scans by the Orbiter Boom Sensor System (OBSS) package.

“The STS-134 FD2 OBSS Surveys went well. OBSS grapple occurred at 2:00 am and it was unberthed from the Stbd MPM at 2:05 am Tuesday,” noted a MER review (L2) into completed task.

“The Stbd T0 umbilical and OMS pod were surveyed from 2:55-3:15 am. Stbd RCC was surveyed from 3:25 am to 4:43 am. Nose RCC was surveyed from 5:12 am to 5:43 am. Port RCC was surveyed from 6:16 am to 7:51 am. The Port T0 umbilical and OMS pod were surveyed in between Port RCC scans per procedures. The OBSS was berthed on the Stbd MPM at 8:27 am.

“Crew had to play back 1 hour and 14 minutes of the OBSS surveys since we did not get this live due to KU-Band blockage at the time the surveys occurred.”

The results of the FD2 Inspections confirmed Endeavour’s critical Reinforced Carbon Carbon (RCC) panels to be in excellent shape, along with other areas of the orbiter covered by the OBSS’ sweep.

“LESS/RCC team cleared all regions of interest. OBSS Survey started 5/17 at around 3am, and final PRT disposition occurred 5/18 at around 8:00 pm ( 29 hours). No ROI (Regions Of Interest) exhibited any damage characteristics,” noted a Flight Day 3 DAT presentation (L2).

A total of 389 areas were reviewed – one of the lowest counts since the implementation of the OBSS’s Laser Dynamic Range Imager (LDRI), with the 137 ROI count much lower than Discovery’s STS-133 count of 225.

The review of all ROIs resulted in the RCC being cleared for entry – although a second sweep will be undertaken during Endeavour’s Docked Late Inspections (DLI) ahead of departing from the ISS. The FD2 data will provide a baseline for those late inspections.

“137 ROI’s required PRT disposition. All threats cleared. No focused inspection candidates identified. As a result of this review the LESS is GO for entry,” added the DAT presentation. “FD2 results will serve as the baseline for late inspection.” 

The other major data gathering exercise was carried out ahead of Endeavour’s docking on Flight Day 3, as the ISS crew took hundreds of 400m, 800mm and 1000mm photographs (hundreds of hi res photos available on L2) of the orbiter as she was commanded through her RPM backflip.

This manuever allows of all areas of the orbiter to be photographed, and – due to the limitations of the OBSS’ reach – provided the DAT with a full sweep of Endeavour’s belly.

No major flags of concern have been raised at this time, although Endeavour does have seven cosmetic dings on her belly.

While it is likely none of the damaged tiles will be of any concern for her entry at the end of the month, the DAT engineers always carry out a full review of any areas of interest, opening with their Focused Inspection (FI) discussion, allowing them to inform the Mission Management Team (MMT) if a FI is required or not.

Most of the damaged tiles are expected to be cleared by the DAT within hours. However, three areas – more notably on the inboard elevon – are being called a FI candidate, as much as all damaged areas hold such a title until they are cleared from the closer inspection.

According to DAT presentations (L2) the elevon’s damaged area covers a length of about 6.5 inches and is 2.3 inches wide – with a margin of error of .15 inches.

The depth – one of the key parameters – of the damage is 1.63 inches, the deepest of all the damaged areas. However, its location will also be part of the discussions, given some areas are more susceptible to the heating of re-entry than others.

A FI has a placeholder on Flight Day 6 of the mission, should it be required, which would be only the second time such an inspection was called for.  Currently – according to MMT chair LeRoy Cain, actions have been taken to protect the placeholder of a FI on FD6, while another 24 to 48 hours of evaluation will continue on the forward plan.

Ironically, it was Endeavour which required the use of the OBSS’ cameras and sensors to take a look at a “gouge” on her belly during her STS-118 mission.

Notably, the FI discussion package included STS-118 presentations on the area of damage – caused by an ice impact - which required the use of the OBSS midday through her mission to the ISS, although the data gained did result in a MMT decision that no repair was required.

Post landing images of Endeavour on the Shuttle Landing Facility (SLF) showed the damage had worsened during re-entry, along with no ill effects to the underlying structure on the orbiter when the damaged tile was removed in the Orbiter Processing Facility (OPF).

Also under consideration will be the cause of the dings on Endeavour’s belly, especially after ascent imagery and photographs of the separated External Tank (ET-122) showed it enjoyed a clean ascent, with only a few minor liberations from the tank’s Ice Frost Ramps (Ice Frost Ramps).

Although the ascent review is ongoing, current information has not listed any TPS impacts from the minor liberations spotted by the camera on the ET.

More will follow.

(All images via L2. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

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