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...

The Final Space Shuttle Spacewalk:

With Flight Day 12 (FD-12) for Endeavour and her STS-134 crew come four important and truly historic milestones: the final EVA/Spacewalk of the Space Shuttle Program, the final Station construction EVA by non-ISS crewmembers (as currently scheduled), the permanent transfer of Endeavour’s Orbiter Boom Sensor System from the Shuttle itself to the International Space Station, and the 1000th hour of spacewalking time dedicated to construction of the International Space Station.

After waking up at 1956 EDT, Mike Fincke and Greg Chamitoff emerged from the Quest Airlock where they spent the night “camping out” for their final foray into the vacuum of space.

After a brief, 30-minute hygiene break, Fincke and Chamitoff returned to Quest to begin final preparations for their spacewalk, or EVA – Extra-Vehicular Activity. Once the crew lock of Quest was depressurized to 10.2 psi, spacesuit purge was conducted as the spacewalking duo donned their tell-tale white EMUs (Extravehicular Mobility Units).

Once the crew lock was completely depressurized, Fincke and Chamitoff took their EMUs to battery power and officially began the final Space Shuttle crew spacewalk in history at 4:02 Central time.

However, per the mission timeline, just before the duo took their spacesuits to battery power, the Space Station Remote Manipulator System (SSRMS), or robot arm, reached out from the Station and grappled Endeavour’s OBSS – which itself was grappled by the Shuttle Remote Manipulator System (SRMS).

Fincke and Chamitoff began their EVA excursion with an egress from the Quest Airlock on the Station. At this same, per the written EVA timeline, the Endeavour crew commanded the SRMS to ungrapple the OBSS – marking the official handoff of Endeavour’s long-serving and extremely important OBSS from Endeavour to the Station, and by extension from the Space Shuttle Program to the International Space Station Program.

Interestingly enough, the handoff of Endeavour’s OBSS to the ISS marked the final element of Space Shuttle flight hardware to be permanently deployed on and attached to the ISS – bringing a full circle to Endeavour’s career as the Space Shuttle orbiter that both began construction of the International Space Station and completed U.S. assembly of the iconic orbiting laboratory.

Moreover, this marked Endeavour, two times over, the only Space Shuttle orbiter to launch with an OBSS and not return with it.

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

The previous mission to do so was STS-123/Endeavour in March 2008. During that flight, Endeavour’s crew (of which Greg Johnson was a part of as well) also performed a docked late-inspection of OV-105’s Wing Leading Edge Reinforced Carbon-Carbon panels before deploying their OBSS on the Station for use by the next Shuttle mission: STS-124/Discovery.

After exiting the ISS, Fincke and Chamitoff moved out to the S0/S1 truss and provide visual and audio commentary/directions as the SSRMS is used to lower and berth the OBSS to its already installed stanchions.

Once SSRMS manoeuvring ops were complete, Fincke and Chamitoff began OBSS post-berth securing operations.

Unlike the similar STS-123 EVA to attach the OBSS to the station, this mission will not feature OBSS “keep alive” activities for the dedicated sensor packs on the boom’s scanning end. Since the sensors will no longer be needed for any Space Shuttle orbiter TPS evaluations, the sensors will be allowed to “die” and decay.

After initial securing operations are complete, Fincke and Chamitoff translated over to the P6 truss and retrieved a stowed Power Data Grapple Fixture (PDGF), which they brought back to the OBSS at the S0/S1 truss.

Once back at the OBSS, Fincke and Chamitoff started to remove the boom’s End Effector Grapple Fixture – the grapple fixture which, until now, allowed the Endeavour’s SRMS to grapple and control and interface with the OBSS.

However, this Shuttle-ready interface unit on the OBSS is not compatible with requirements of the Station’s SSRMS. Thus, the EFGF was removed from the OBSS and stowed on the Station’s Tool Stowage Assembly.

Chamitoff was then tasked with installing the PDGF onto the OBSS – which will allow the SSRMS to grapple the OBSS at its end point and allow for maximum reach and utility of the OBSS as a Station-based asset for future ISS crews.

After this, Greg Chamitoff began an inspection of the OTP before joining Mike Finke at Canadian-built Dextre (or the Special Purpose Dexterous Manipulator). During their work on Dextre, Fincke and Chamitoff released a retention system on the spare robotics arm.

Interestingly enough, the final Space Shuttle crew to perform work on Dextre was a crew of Endeavour. Endeavour was the orbiter that delivered Dextre to the International Space Station on the STS-123 mission.

After this, Fincke and Chamitoff performed a few “get ahead” tasks before cleaning up and ingressing the Space Station, but not before Chamitoff paid tribute to Endeavour, the ISS and the thousands of workers involved in constructing the orbital outpost.

“This is the last flight of Space Shuttle Endeavour and it’s also the last spacewalk of shuttle crewmembers and for station assembly,” noted the spacewalker from the “top” of the Station.

“It’s kinda fitting that Endeavour is here, ’cause Endeavour was the first shuttle to begin construction of the station, and so it’s fitting that she’s here for the last mission for station assembly. 

“During this EVA we passed collectively over 1000 hours of spacewalks that is part of station assembly.

“Mike and I have the honor here to share this last spacewalk and of course for all the folks working on the ground, thousands of people helped build this – working in the shuttle and station program – we’re floating here on the shoulders of giants.

“This space station is the pinnacle of human achievement and international cooperation. Twelve years of building and 15 countries and now it’s a cornerstone in the sky and hopefully the doorstep to our future.

“So congratulations everybody on assembly complete. Ok, time to go home.”

At the completion of EVA-4, officially marking the end of a 7 hour and 24 minute EVA, Mike Fincke is ~13hrs shy of breaking the all-time American/NASA astronaut endurance record for cumulative time spent in space. Currently, the record is held by now-Chief of the Astronaut Office Peggy Whitson. Fincke is due to surpass her 377-day record at ~8pm EDT Friday.

Space Shuttle EVA History:

Since Space Shuttle EVA operations began on the STS-6/Challenger mission in April 1983, astronauts have spent thousands of hours building a space station, helping maintain MIR, saving/upgrading/servicing the Hubble Space Telescope, servicing satellites in orbit, and learning new and innovative ways to work in the confines of a large, bulky pressure suit.

Of the 162 spacewalks performed over the life of the Space Shuttle Program, 121 of those have been performed since the STS-88/Endeavour mission in December 1998 – the mission that began construction of the International Space Station.

Before the era of the ISS, only 41 Space Shuttle spacewalks were performed: a handful in support of joint Shuttle/MIR operations, a few designed to test concepts for Space Station construction, and numerous EVAs to retrieve, repair, and re-release satellites in Low Earth Orbit – including 10 dedicated to Hubble.

However, not all of the 121 ISS-era spacewalks were in support of ISS construction. In fact, 108 of those 121 spacewalks have been conducted in support of construction of the International Space Station over the course of only 36 missions.

The remaining 13 (still a whopping number) were performed over the course of three missions (STS-103/Discovery, STS-109/Columbia, and STS-125/Atlantis) in support of maintenance and upgrades to the Hubble Space Telescope.

In all, a whopping 23 EVAs were undertaken by the crews of just five Space Shuttle missions to save, service, repair, and upgrade the Hubble – our window on the universe.

But more striking here at the completion of EVA-4 for STS-134, is the coincidence – once again – with Endeavour.

Today’s spacewalk marked the 4th and final spacewalk of Endeavour’s STS-134 mission. The first time four spacewalks were conducted on a single mission was back on STS-49 in May 1992 – the maiden voyage of Endeavour.

Similarly, Endeavour was the first Space Shuttle orbiter to perform five back-to-back spacewalks on single mission – an achievement that has never been topped, only equalled.

Click here for Endeavour’s full history:
Part 1: http://www.nasaspaceflight.com/2011/04/space-shuttle-endeavour-a-new-beginning-part-i/
Part 2: http://www.nasaspaceflight.com/2011/04/ov-105-endeavour-a-long-standing-dream-realized/

Moreover, 161 of these 162 historic walks in space have been conducted with only two astronauts. Only one has ever been conducted with more than two astronauts; STS-49 (Endeavour’s maiden voyage) saw a three-person spacewalk on EVA-3 of that mission.

And while today represents a Shuttle crew’s last foray into the vacuum of space, we remember the skill and dedication of all individuals – both those in space and especially those on the ground… the hundreds of unnamed planners and trainers and supporters of our EVA undertakings – involved in all the spacewalks across the program.

But most importantly, as we mark the closing of another highly visible and significant chapter of the Space Shuttle Program, we take with us the lessons we have learned from our spacewalking enterprises, and we thank the thousands of men and woman around the world who have supported these valiant efforts in Low Earth Orbit.

(Images via L2 presentations, videos and images – plus L2 Historical 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 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...

OV-103 Release from Flight Status:

As stated in the End State Flow Review (ESFR), “At the End State Requirements Review (ESRR), the decision was made to maintain and preserve the majority of hardware [from OV-103/Discovery] in a flight mode, less select fluid system deservice and OMS Pod / FRCS (Forward Reaction Control System) removal and deservice.”

This plan, which originally proposed maintaining Discovery in or near flight condition for as long as possible following STS-133, has undergone significant analysis in the months that followed the initial review; as a result of this analysis, SSP (Space Shuttle Program) managers have revised their proposal for Discovery post STS-133.

“SSP Management has requested that we plan to release OV-103 to T&R (Transition and Retirement) at wheel-stop,” notes the ESFR – available for download on L2.

The immediate release of Discovery from flight service would be followed by the removal of her two OMS pods (Right Pod 03 and Left Pod 01, known as RP03 and LP01) and Forward Reaction Control System pod (FRC3) after her return to OPF-3 (Orbiter Processing Facility bay 3).

Once removed and sent to the HMF (Hazardous Materials Facility), the SSP has further requested that the pods be removed from flight status and handed over for T&R processing. 

“Post STS-133, upon delivery of Pods and FRCS to the HMF, request authorization to release RP03, LP01, and FRC3 from flight status to T&R processing. At that point, OMS Pods and FRCS will no longer be considered flight hardware,” notes the ESFR document.

At this time, specific risk analyses for the release of the OMS pods and FRCS pod from flight service have been performed to determine any negative effects on the Space Shuttle Program’s ability to flyout the post STS-133 manifest without these pieces of hardware. No negative affects were identified.

Furthermore, the release of further hardware from flight status upon the completion of STS-133 will be performed over the coming month and presented at the Delta ESFR.

This meeting is currently planned to occur roughly one month after Discovery’s landing on STS-133 – the time when technicians will complete down-mission processing activities on Discovery.

Moreover, alternative to the above mentioned request to remove Discovery from flight service/status at wheel-stop on STS-133, placement of Discovery into T&R could be deferred to the Delta ESFR.

Nonetheless, no matter when Discovery is placed into T&R, “a PRCB (Program Requirements Control Board) Directive will document release of the vehicle from flight status and approval to proceed into the T&R and ESSRD (End State Subsystem Requirement Document) implementation phase.”

Nonetheless, while Discovery herself may be released from flight status upon or one month after the completion of STS-133, the standard post-flight inspections and analyses will be performed to maintain fleet and post STS-133 mission safety.

This includes all standard post-flight problems tracking teleconferences and reporting, File IX review for items affecting safety, In Flight Anomaly resolution and closure, MADS data review, Micro-Meteoroid Orbital Debris (MMOD) inspections on her windows, payload bay doors and RCC (Reinforced Carbon-Carbon) panels and nose cap, and all standard TPS (Thermal Protection System) post-flight inspections.

Post Down Mission Processing Configuration for OV-103:

Following the completion of down mission processing, technicians will remove from Discovery all the necessary flight hardware that has been identified for preservation through the flyout of the Shuttle manifest, identified for future use or belonging to a payload customer, and identified as necessary for the support of another Program.

This will involve the removal of ROEU, ELC keel, DragonEYE, LWAPA, payload bay & umbilical cameras, TSA, winches, PFR, OBSS sensors, and the TCS (Trajectory Control Sensor). Conversely, most payload accommodations and CIH hardware (including wiring and panels), latches, bridges, and GAS beam will be left installed as part of Discovery’s museum display configuration.

Likewise, Discovery’s SRMS (Shuttle Remote Manipulator System – robot arm) and OBSS (Obiter Boom Sensor System) will be left installed for her museum display. This full up SRMS/OBSS configuration will also be implemented on Atlantis during her T&R processing.

Endeavour (OV-105), however, will return from her last mission without her OBSS, having left it on the ISS (International Space Station) to act as an extension arm for SSRMS (Space Station Remote Manipulator System). Endeavour, upon T&R processing, will also have her SRMS removed and sent back to Canada (the maker of the SRMSs for the Shuttle orbiter fleet) for display in Canada as recognition for their integral role in the Space Shuttle Program.

Discovery will also receive a full set of middeck lockers for display configuration. A remaining full set of lockers will be divided between Atlantis and Endeavour.

Also in terms of Discovery’s museum display configuration is the type of engines she will sport. As previously reported by NASASpaceflight.com, Discovery and sisters Atlantis and Endeavour will not carry flown SSMEs (Space Shuttle Main Engines) with them to their display locations. Instead, Replica Shuttle Main Engines (RSMEs) will be fitted to all three orbiters.

Therefore, Discovery’s SSMEs from STS-133 will be removed following her return to OPF-3.  Under previous timelines which would have seen Discovery launch during the early November 2010 launch window for STS-133, OV-103′s SSMEs would have been removed the second week of January. This schedule, however, is in flux given the now NET 30 November 2010 launch date for Discovery.

Once removed, Discovery’s three SSMEs will be transported next door from OPF-3 to the SSME Processing Facility for “for post-flight inspections and nominal turnaround flight processing.”

Then, under the now preferred option for Discovery’s display configuration (which is still under review), Discovery would be fitted with three RSMEs No Later Than (NLT) April 15, 2011 – a date which would also be in flux given the fact that Discovery is still on Pad-A.

Once the RSMEs are installed, nominal SSME close-out operations (including installation of the Engine Mounted Heat Shields and Dome Heat Shields) will be carried out on the RSMEs.

Currently, a Change Request is in the system for the design, manufacturing, and installation of the RSMEs. “RSMEs comprised of scrap SSME nozzles and newly-designed nozzle adapters; three (3) per Orbiter.”

In all, 10 “scrap” SSME nozzles have been indentified that could/would be used for the RSMEs. These nozzles would only require minor cosmetic repair. Moreover, “Establishment of requirements and preliminary design of nozzle adapters, stiff arms, and attach point brackets continues.”

Overall, under the updated preliminary timeline for all T&R activities for Discovery, the vehicle will complete down mission processing before the end of calendar year 2010. (NOTE: This timeline was based on a 1 November 2010 launch of STS-133 and does not account for the recent delay to the STS-133 mission.)

Discovery’s RSMEs would be installed in April 2011 with final closure of OV-103′s payload bay doors occurring in June 2011. Closure of the payload bay doors would be followed that same month by the final power down of Discovery.

Pyrotechnic safing would be completed by the beginning of August 2011. Discovery would then be jacked down, weighed, and her final Center of Gravity determined in October 2011. Then, in early November 2011, Discovery would be ready for transfer to her final display site.

(Under the revised multi-flow T&R timeline, Atlantis [assuming she does NOT fly STS-135 next year] would be ready for final transport to her display site in early April 2012. Endeavour would be ready for final transport to her display site in mid-June 2012.)

White Sands Test Facility OMS/RCS Post-flight Processing:

In addition to specific payload and Main Engine requirements, Discovery’s twin OMS pods and FRCS pod will need to undergo deservicing operations at the White Sands Test Facility (WSTF) in New Mexico.

To accomplish this, the pods will have to be transported over land to White Sands. As such, the pods will have to be configured for transport – a configuration that will have to meet DOT (Department of Transportation) safety regulations.

Moreover, Ground Support Equipment (GSE) for the handling and transportation of the pods will have to be manufactured/modified and pre- and post-transfer inspections of the pods will have to be performed both for their journey to WSTF and their journey back to KSC.

To begin the task of supporting the pods’ transfer, a Technical Interchange Meeting (TIM) occurred on October 12-13 that determined preliminary work to be performed at KSC for the pods transfer as well as the overall configuration of the pods for shipment.

In terms of KSC work, the OMS and RCS oxidizer and fuel suspended vapor and residual liquid will be removed, the manifolds will be “drained and educted,” the pods “[drained] to gas break in 45-degree orientation,” the RCS oxidizer and fuel propellant tanks vertically drained to “remove liquid in aft compartment,” the thruster valve/Pc transducers removed and blanking plates installed, and the OMS oxidizer tanks completely deserviced and purged to “eliminate suspended vapors.”

Once this is complete, the pods will be placed into their shipment configuration, including: a 40psia system blanket pressure propellant, a 40psia helium/GN2 (gaseous nitrogen), the closure of all valves, all feedlines purged, the OMEOME tile covered and heatshield removed, the primary OMS nozzles removed, all doors installed without carrier panels, and less than 25 lbs N204 and less than 20 lbs MMH.

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OBSS PTU Snag:

The OBSS and its sensor package are one of the unsung heroes of the Return To Flight (RTF) era, allowing for post-launch and pre-entry inspections of critical area of the orbiter’s Thermal Protection System (TPS).

Teamed with an arsenal of imagery footage and expert engineers with the Damage Assessment Team (DAT) in Houston, all post-Columbia missions have successfully returned with added – and justified – confidence in the health of the heatshield.

The evaluations into the TPS begins as soon as the shuttle launches, with ground-based cameras and radar tracking debris hazards, working in tandem with orbiter based assets, such as the ET cameras and crew photography footage of the tank – the main source of debris threats.

Flight Day 2 is highlighted by the first use of the OBSS during the mission, focusing on three primary areas; the nose cap and the port and starboard Wing Leading Edges (WLE) – ensuring the Reinforced Carbon Carbon (RCC) panels avoided damage during ascent.

STS-132′s FD2 inspections began without issue, with the OBSS unberthed, followed by the activation and calibration of the Laser Dynamic Range Imager (LDRI) on the boom’s sensor suite. A quick check for ice on the starboard T-0 umbilical was followed by a robotic translation to the start point for the starboard wing survey, which revealed an issue with the PTU.

“Background of Issue: During the beginning of STS-132 FD2 Inspection procedures, PTU readings and behavior were erratic and eventually lead to determination that it was not able to move the entire tilt range,” noted the PRCB presentation, available on L2.

Ground controllers asked the crew to reset the PTU in an effort to correct the issue, prior to the crew visually noticing a cable – known as the W601 cable – was snagged on the unit’s protruding reed sensor.

“All attempts to resolve were unsuccessful: Crew manipulation, ground control manipulation, change in PTU speed. PTU was unable to point to the tilt values required to support FD2 Inspection. A cable snag was confirmed by the crew viewing PTU motion from the Flight Deck windows.”

Despite losing the PTU’s full range of motion, most of the survey was completed, with a plan to utilize Flight Day 3′s R-bar Pitch Maneuver (RPM) – aided with additional ISS crewmembers, armed with cameras – to capture additional imagery footage for the DAT engineers.

Meanwhile, the Mission Management Team (MMT) asked KSC engineers to look into how the snag could have occurred, checking closeout photos of the OBSS PTU ahead of Payload Bay Door (PLBD) closure for flight, along with flight history and checks into replaced elements of the hardware.

“Cable Flight History: Sensor Pack 1 (SP1) with W601 Cable S/N (Serial Number) 1002 is the same unit that flew on STS-130. Prior to STS-132, SP1 assembly required a PTU change out – requires disconnect and re-connect of W601 cable (same cable, S/N 1002),” added the presentation.

“Full pan and tilt range was confirmed post re-assembly during the STS-132 Pre-Installation Acceptance (PIA) testing with no issues of a cable snag. Installation procedures and close out photos were reviewed – no indication of incorrect installation. S/N 1002 Cable has flown on STS-130, STS-128, STS-125, STS-123/124, STS-115, STS-114.”

With the MMT noting their preference for the full use of the PTU to be restored, a cable tie plan was implemented on EVA-2 of the mission, freeing and holding back the snagged cable, and ultimately allowing for a nominal Late Inspections to be carried out without issue.

“In-Flight Resolution: During EVA2, the cable was physically removed from the snag point and an additional cable tie was installed to preclude the snag from reoccurring. Full PTU pan and tilt motion was restored and Late Inspection was performed nominally.

“Photos of flight hardware post STS-132. Red circles are area of snag occurred.”

Post Flight Troubleshooting:

Once Atlantis was back inside her Orbiter Processing Facility (OPF-1), engineers began a hands-on inspection of the PTU by removing the unit from the OBSS, part of the nominal procedures for preparing the PTU for its next flight, although this time including the enforced changeout of the troublesome cable.

“Troubleshooting Plan: Post flight activities – remove from vehicle, post flight functional of LDRI, manipulate Pan and Tilt to verify proper cable movement with added cable tie, cut added cable tie, manipulate SP1 assembly to attempt and recreate snag,” the presentation continued.

“Replace W601 Cable S/N 1002 with S/N 1005, confirm W601 cable S/N 1005 cable characteristics during full pan and tilt motion. Per Pre-Installation Acceptance procedure pan/tilt values. Per on-orbit operational pan/tilt values, determine if additional cable tie required, perform STS-133 Pre-flight PIA in prep for OPF testing.”

Implementing part one of the plan, engineers cut the cable tie installed during EVA-2, and attempted to perform the movement of the PTU with the old W601 cable that snagged during FD2 inspections. Just like it did on orbit, the cable snagged several times during ground testing.

“Performed troubleshooting on 6/16/10 in lab at KSC. Verified proper cable movement during PTU motion with cable tie attached. Cut added cable tie. Cable retained some memory of the added cable tie adjusted configuration thus cable had to be manually manipulated to re-create the pre-launch configuration,” noted the presentation.

“Cable laid flush against the PTU tilt ring at +102, -252 (pan, tilt). Moved PTU pan to +85 and the cable remained against the tilt ring. When the PTU was tilted up, it was observed that the cable snagged against the fixed electronic stop (Reed Sensor).

“It was concluded that the cable had to have been laying flat against the tilt ring at +102, -252, when the crew began panning and tilting in slow rate in order for the cable to snag. Able to recreate this scenario multiple times using W601 cable SN 1002.”

Engineers then replaced the old W601 cable with a new spare, re-performed the movement of the PTU, and successfully avoided the cable snagging during the tests.

“With successful recreation of the issue, W601 cable S/N 1002 was changed out with S/N 1005. Motion of PTU and cable characteristic was verified – values per PIA procedures, which include full range of motion, and on-orbit operational values.”

Forward Plan:

As to what caused the old cable to snag on the reed sensor during STS-132, and how can such a situation be avoided in the future, engineers checked to see if the W601 cable was somehow being pressed against the PTU after the Payload Bay Doors have been closed – in other words, if hardware was breaching into the space (envelope) of where the cable was positioned.

“Envelope Measurement History: Each of the three fully assembled SP1 units were measured for dynamic envelope to confirm clearance to the radiators and to any stowed payload,” added the presentation.

“Current Active Sensor Pack 1s: S/N 1003 with W601 cable S/N 1005. S/N 1007 with W601 cable S/N 1003. During this activity, it was noticed that each W601 cable has its own characteristics with respect to routing, translation and memory.”

With those findings – showing it may be an uncontrollable issue if left as-is – the Orbiter Project Office (OPO) will test the potential of added an additional cable tie, in order to guarantee the W601 cable avoids being pressed into a position that threatens it subsequently being snagged on the reed sensor.

“OPO has requested to assess the envelope measurement with the additional cable tie. Pending confirmation of positive envelope impacts, cable tie will remain in place for flight,” confirmed the conclusions to the presentation.

Testing on the viability of adding a new cable tie will take place during the week of July 26.

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Flight Day 2 opened with the unberthing of the Orbiter Boom Sensor System (OBSS) via the Shuttle Remote Manipulator System (SRMS), in order to carry out surveys of Discovery’s wing and nose cap, before heading to the OMS Pods to check for any tile damage or protruding blankets.

Other items on the list for FD2 include EMU (EVA Mobility Unit) checkouts, ahead of their use on the mission’s three EVAs, and the extension of the Orbiter Docking Ring for FD3′s docking to the International Space Station (ISS).

Under evaluation, or as is the case with the first item on the list, the MER engineers only had one issue to deal with pre-launch, relating to a helium valve at the pad. This issue was corrected by the Red Team.

“MER-01 Pre-launch: Low range LH2 Plate Gap Delta Press was out of spec,” noted L2 mission coverage. “Helium purge to the plate gap cavity was increased via console commands and secondary system activation brought the system back within LCC (Launch Commit Criteria) limits.

“A red crew was successfully sent in to the Pad to adjust a needle valve to increase flow. A waiver to LCC MPS-48 was approved.”

Discovery’s spectacular launch has been deemed extremely clean, with no foam or debris issues of note found, bar one late release relating to a remnant of a tyvek cover at T+17 seconds into ascent. However, this has already been cleared, due to no impact noted on the vehicle.

“Tyvek F4D Cover Remnant Partial/Late Release: Ground imagery showed that when thruster F4D’s (Thruster) Tyvek rain cover released at 5.28 sec MET (~93 fps or 63 mph), a large piece remained attached to the thruster lip as shown (see main article image),” added MER on L2′s mission coverage pages.

“This piece is believed to have separated by ~17.3 sec MET (~380 fps or 259 mph). Imagery shows that the piece did not impact the Orbiter. No vehicle/mission impacts ensued nor are any crew responses required.”

The covers, which protect the orbiter’s RCS (Reaction Control System) thrusters ahead of launch, are designed to release shortly after lift-off. However, late releases can become a debris concern. Despite the remnant of the cover failing to impact the vehicle, engineers used the event to ensure no damage was possible, even if it had struck Discovery.

“Problem Impact/Significance: Testing and analysis of 5-gram Tyvek remnant releases up to 1000 fps have low risk of producing unacceptable damage; however, estimated remnant size for the present F4D failure is greater than 5 g,” added the MER report.

“Impact testing using full-sized covers on RCC samples up to 240 mph produced no damage. Similar impact testing on tile produced minor pitting for impacts between 216 and 268 mph.

“Since the F4D Tyvek piece that released at ~259 mph was enveloped by full-cover impact testing in terms of both mass and velocity, any impact damage would not be expected to be worse than these ground test results.

No TPS damage has been attributed to Tyvek cover releases to date. Any TPS damage attributable to these covers would be tracked under TPS damage assessment efforts. This failure has not affected (nor is it expected to affect) FRCS thruster performance. Thruster F4D was first fired at ET Sep and has performed nominally to date.”

Discovery’s launch came after a few months of evaluations into the Flow Control Valves (FCVs), which led to three valves – all of which had flow with Discovery four to five times previously – being ‘cherry picked’ for the ride to orbit.

Click here for NASASpaceflight.com articles on the FCV issue since STS-126.

The concern related to a liberation from one valve’s poppet during Endeavour’s STS-126 launch last year, first seen via ascent data evaluated by the MER engineers.

However, for STS-119, that data – as seen in a presentation of their data during ascent – showed all three valves performed without issue, mirroring each other’s performance via their cycles used to keep the pressurization of the tank at nominal rates.

During ascent, three indications were registered by the Wing Leading Edge Impact Detection System (WLE IDS), which are used to “feel” indications of impacts on the RCC panels.

These sensors are highly sensitive and usually detect “ghost impacts” rather than actual impacts, especially on orbit.

The three indications will be evaluated via their timing and strengths, in collaboration with ascent imagery.

“All WLE IDS ascent summary data were downloaded and down linked successfully,” noted the FD2 MMT presentation from the WLE IDS team, on L2.

“Twenty-two (22) 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 three (3) Category I indications; one (1) on the starboard wing and two (2) on the port wing.

“Overall, background levels for STS-119 are very similar to background levels of previous missions. No data anomalies have been identified. All units triggered on Main Engine Ignition within 0.13 seconds of each other, except unit 1029 on the starboard wing which triggered 0.625 seconds early.

“The primary WLES laptop failed to receive data at approximately MET 6 hours. After troubleshooting, ACO and WIS-GFE swapped from the primary to the backup WLES laptop. A complete set of summary data files was received approximately four hours later than expected.

“WLE IDS On-Orbit Monitoring is currently planned to begin at approximately MET 18 hours with Port and Starboard Group 1.”

Following MECO (Main Engine Cut Out), Discovery separated from the External Tank (ET), before a camera in the umbilical well of the orbiter takes photography of the departing tank. An issue has been noted on the apparent lack of flashes being seen from the well, which is used to enhance the images.

“The Digital Umbilical External Tank camera flash was not observed in the live video during ET separation,” added the MER. “Based on the video downlinked thus far, the analysis confirmed the observation.

“The crew was then unable to downlink the imagery from the Thermal Protection System (TPS) camera as planned. Troubleshooting was attempted, but discontinued for crew sleep.”

An issue has also been noted with Fuel Cell O2 Flowmeter measurement, which has failed Off Scale Low (OSL), which holds slight impacts to its monitoring and use. Discovery has had similar problems of the same nature during her previous flights, such as STS-116.

“The Fuel Cell 3, s/n 116, Oxygen Flowmeter Measurement Failed OSL at 075/01:57:15 GMT,” noted a report to the Mission Management Team (MMT) on L2. “The Loss of the FC 3 O2 FM is negligible impact to the crew and a slight impact to MOD/EGIL (Electrical Generation and Illumination Engineer).

“EGIL will use other parameter such as pressure decays, purge line temperatures, and fuel cell performance to verify FC 3 purge.”

The most probable cause of the FC 3 O2 Flowmeter OSL reading is a failure of one or more electronic components within the circuitry installed in the flowmeter.

“Failure analysis performed on previous flowmeters has identified a marginal design with overstressed, obsolete EEE components within the circuit.

“Redundancy: FC 3 Purge can be verified by cryo pressure decays, purge line temperatures, and fuel cell performance. The pressure decays also serve as an indication of gross reactant leakage.

“With the loss of FC 3 O2 FM, the vehicle is in a stable configuration. The FC 3 O2 FM measurement has been inhibited in the vehicle Fault Detection Annunciation to avoid nuisance alarms. No additional on-orbit trouble shooting or analysis has been planned or is required.”

This particular Fuel Cell is on its last flight, due to its operating hours closing in on the time between overhaul limit. It is scheduled to be removed during post flight processing at the conclusion of STS-119.

Other issues being reported to the MMT include the apparent loss of the Avionics Bay fan. No mission impacts have yet been noted on this particular issue. Another issue relates to the RMS shoulder brace release time, which is not deemed to have any mission impacts.

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

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The plan, which would result in the final shuttle mission returning home without the OBSS, was previously suggested for STS-133 (Contingency Logistic Flight) – the final shuttle mission manifested for the shuttle program.

However, the shuttle program is ‘very close’ to being extended by several missions, with STS-134/AMS already added to the latest “planning” document by the Flight Assignment Working Group (FAWG) – article to follow this week.

Regardless of when the OBSS would be left behind by a shuttle mission, its requirements for Late Inspections on that particular mission would follow the plan utilized during STS-123.

Due to clearance issues in the Payload Bay with STS-124′s Kibo Laboratory, STS-123 carried out a docked Late Inspection – which proved to be a successful technique – before berthing the OBSS on the outside of the orbital outpost (S1 Truss).

That again would be the plan with adding the OBSS to the Station on a permanent basis, allowing its use by ISS crewmembers, which would be especially useful during Expedition EVAs.

“Board approved the costing to enable leaving the OBSS on the S0 truss on a permanent basis,” noted this week’s MOD 8th Floor News memo on L2. “It provides funding to provide an EVA change out of the forward Shuttle grapple fixture with a SSRMS (Space Station Remote Manipulator System) compatible PDGF (Power Data Grapple Fixture.

“This allows the SSRMS to grapple the OBSS at either the mid or fwd location. Also, this implementation does not preclude adding camera equipment in the future if desired.

“The OBSS will be available for the ISS to use as a EVA crew platform for viewing or maintenance activities.”

A good example of the OBSS’ ability to aid EVA work on the ISS was seen during Scott Parazynski’s epic EVA on STS-120, when he rode a combination of the OBSS and the SSRMS to carry out repair work on the P6 4B Solar Array. Parazynski would not have been able to reach the array, had it not been for the reach provided to him by both arms.

The OBSS was added to the Shuttle Program as a Return To Flight addition of enabling a full inspection of the orbiter’s TPS (Thermal Protection System) after ascent (Flight Day 2) and post undocking (Late Inspections).

The OBSS includes an instrumentation package that consists of visual imaging equipment, this includes the Laser Dynamic Range Imager (LDRI), and Neptec’s Laser Camera System (LCS). Since RTF, the OBSS has more than proved its worth, providing additional confidence in the health of the orbiters prior to re-entry.

This was best seen during STS-118, when the OBSS was tasked with taking a closer look at a gouge on the underbelly of Endeavour.

Thanks to unique imagery and data via the LCS – which included a 3D movie of the damage – engineers on the ground were able to clear the TPS for re-entry, a decision that proved to be fully justified by the lack of damage observed in post landing inspections.

The cost of allowing the OBSS to be left on Station is understood to be around a $1m, which – compared to shipping it off to an exhibition – would more than pay for itself should ISS crewmembers require its use during maintenance work on the ISS.

In other ISS robotic related news, the Dextre Special Purpose Dexterous Manipulator (SPDM) continues to be checked out ahead of its first major role on the ISS.

Dextre was grounded during troubleshooting recently, when engineers identified a potential failure mode in the SPDM Power Switching Init (PSU). However, tests have shown the robot will be able to press forward with tasks scheduled for the Autumn.

“The SPDM continues to be checked out by the mission control team in preparation for a R&R of a RPCM (Remote Power Control Module) in the fall,” added the expansive 8th Floor ISS update. “The team operated the Space Station Remote Manipulator System (SSRMS) and SPDM.

“Operations included motion of the dexterous arm 2 shoulder roll joint, which had a hardware problem during STS-123 in March 2008. Engineers were able to correct this with a software update in the MSS 5.2 load which was uplinked in December.

“Arm 2 motion, including the shoulder roll joint, was perfectly nominal. Operations also included SPDM dexterous arm motion in Frame of Resolution (FOR) Auto-Sequence mode, SSRMS FOR Auto-Sequence (and motion) using an SPDM FOR (at a dexterous arm tip), and SPDM dexterous arms “limped”.”

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

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The docked phase of the mission involved four spacewalks, all of which focused on the cleaning and lubrication of the starboard SARJ – with EVA-4 carrying out the same process on the port SARJ. With the starboard SARJ being the problem, it also saw its Trundle Bearing Assemblies (TBAs) replaced.

A two orbit Autotrack test was carried out on the starboard SARJ, following EVA-4, with initial data proving to be positive on the improvements to the rotating joint’s health – via less vibration and lower currents required to drive the motors.

“Port SARJ returned to autotrack operation post-EVA. Drive current levels slightly less after lubing,” noted Mission Management Team (MMT) documentation on L2.

“Starboard SARJ autotrack test performed; required significantly less current to drive: currents were 0.7 – 0.9A prior to lube, currents were 0.17A average and 0.35A peak after lube.”

While the data will take up to two months to fully analysis, managers are already hopeful of the possibility that the starboard SARJ won’t require renewed cleaning and lubrication on a regular basis. More so, a long term plan for the SARJ – which was mapped out during the summer – may not be required.

That plan involved several downstream missions including SARJ ‘clean and lube’ requirements, before the long-term solution of replacing the Race Ring – a plan known as SARJ XL – was initiated.

SARJ XL is classed as “an innovative scheme to potentially take the single spare race ring and insert it between the existing spalled inboard race ring, and the other spare ‘outboard’ race ring.”

At present, engineers are pressing ahead to launch SARJ XL on one of the CLF (Contingency Logistics Flight) missions in 2010, with that mission’s EVAs dedicated towards its installation.

“Trade Study: (ISS Manager) Mr. (Mike) Suffredini had asked about accelerating SARJ XL to ULF4 from ULF5 (ULF5 is the last mission in the “current” manifest). Due to various reasons, many due to hardware availability, the SSPCB directed the SARJ XL to stay on ULF5,” noted the latest news via a MOD memo, on L2, prior to the mission.

“However, (Mr Suffredini) did indicate that he wanted hardware delivery to stay in the same May 09 time period. If for some reason the assembly sequence slips, he wants the have other mission options (ie: hardware delivery should not slip with launch date). One option discussed is whether ULF4 (Russian MRM) may end up slipping with ULF5 taking its place in the sequence.

“Spare Race Ring Viability Inspection: Boeing looked at the ring that will be used for SARJ XL. Although there were several microscopic corrosion “features”, the ring was described as being pristine.”

Due to the complexity of the downstream manifest scheduling – which is already being pushed to into a full 2010 of shuttle flights, even before the now-likely shuttle extension kicks in – removing the need for SARJ XL has numerous benefits, ranging from cost savings to allowing other tasks to take priority on the CLF missions.

The best case scenario envisioned involves a requirement to “clean and lube” the starboard SARJ – and possibly its port counterpart as aging starts to take effect – once every year or so. Such tasks could be included during space station increments, as opposed to becoming shuttle mission EVA tasks.

Once the data from STS-126′s get-well tasks is fully analyzed, engineers will have a better understanding on both their ability to use autotrack on the starboard arrays, and the maintenance timeline. The potential deletion of SARJ XL can then be decided on.

Meanwhile, back on Flight Day 15 of STS-126, another key event is the required Late Inspections of Endeavour’s TPS (Thermal Protection System). The orbiter’s heatshield has already been deemed as completely clear of any notable damage via Flight Day 2 inspections, and Flight Day 3′s RPM imagery.

While the orbiter is protected by the Station during the docked phase – thus the likelihood of any damage is very small – one final inspection is important after docking, due to the contingency of returning to the ISS, should imagery find serious damage on the orbiter.

In such a scenario. the orbiter would be re-docked with the ISS, and her crew taking up residence on the ISS until Discovery could be launched on a rescue mission. Endeavour would undock ahead of Discovery’s arrival, where she would either be commanded through either a destructive – tail first – disposal re-entry, or RCO’ed through to landing.

Such LON (Launch On Need) scenarios are very unlikely, but NASA don’t take chances when it comes to the safe ability of an orbiter to re-enter since Return To Flight – since when the TPS inspections were included into shuttle missions, inclusions that involve the use of the OBSS (Orbiter Boom Sensor System).

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 millimetres, and can scan at a rate of about 2.5 inches per second.

One small issue with the “tilt” direction of the camera suite on the OBSS was noted early in the mission, though this will not affect the ability to gain the required scans during Flight Day 15.

Classed as “OBSS ITVC Tilt Angle Offset”, the issue relates to the PTU (Pan Tilt Unit), which was noted to be offset by nine degrees in tilt and 1.5 degrees in pan. A similar issue was noted on STS-123.

“Bad PTU reset – incorrect reset could be caused either by operator error, or by a cable jam/snag,” noted one of several MMT presentations (L2) on the probable causes.

“2) Cable snag on cable tie – this is the first flight for the cable tie. The tie was incorporated in order to prevent a cable to sensor blanket snag that was observed in ground testing. Remote possibility with position of cable tie

“3) Hardware malfunction -Most unlikely cause since there isn’t any other reports of off-nominal PTU function.”

The bad reset was ruled out, following a failed solution via the reset that was carried out later in the mission as part of the troubleshooting.

“Performed Test 2 from 12:55 am to 2:13 am on Flight Day 12. Offset at -260 degrees tilt agrees with offset of ~9 degrees seen on FD2. Expect OBSS PTU behavior for Late Inspection to be similar to what was observed on Flight Day 2.”

However, with the issue known, Late Inspections can be carried out as planned, without any problems.

“Regardless of Troubleshooting: Additional Pan/Tilt resets will not pose additional risk to the hardware,” added one presentation. “Resets are performed numerous times on ground. Not a life cycle issue. Post Flight ground activities include an inspection and basic functional test.”

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

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