The goal of the experiment was to measure the effects of increased heating from an early boundary layer transition as the orbiter returns to Earth. The DTO was set to debut on STS-126, before being deferred to STS-119.

During a normal reentry, the orbiter compresses the air as it is entering the atmosphere, which creates a protective region (similar to insulation) with temperatures in the 2000-3000F degree range.

Those values are ably handled by the tiles and other protective systems on the shuttle, however,  just inches away – outside of the boundary layer – the readings can rise to 10,000 degrees

If there is any sort of interruption in that flow – such as a protruding gap filler, or damaged tile, or other rough surface – the boundary layer will be tripped sooner than expected, and the extreme heat could cause damage to the tiles, or the orbiter itself in severe cases.

Gap fillers started to become a concern on STS-28, when they were the likely cause of an early BLT (around Mach 18). Several of the gap fillers were found protruding after landing, and more than the usual amount fell on the runway after touchdown.

However a 1989 report from NASA stated that protruding gap fillers were not a flight safety concern, only an issue for turn-around for the next flight.

The STS-119 test was proposed as a means of accurately measuring the actual conditions of an early BLT by installing a specially designed tile with a 0.25” bump to Discovery’s belly. Located near the port main landing gear door, the protrusion was expected to cause a transition around Mach 15.

Specially installed tiles with Modular Auxiliary Data System (MADS) instrumentation were installed in several spots across the orbiter’s belly with the ability to measure precise temperatures.

A Navy P3 Orion was also used, flying over the Gulf of Mexico underneath the shuttle’s path to take infrared pictures known as Hypersonic AeroTHermodynamic InfraRed Measurements (HYTHIRM).

The initial review of the data – via Program Requirements Control Board (PRCB) presentations, available on L2 – indicates that if anything, the models used to determine BLT temperatures were too conservative.

Predictions of the speed at which the 0.25” protuberance would trip the boundary layer were estimated to be around Mach 15.4. However, the initial BLT occurred at Mach 15.6, 969 seconds after the start of Entry Interface (EI).

Surface temperatures in the smooth flow region – protected by the boundary layer – were measured at around 1,600 degrees F which was consistent with flight history.

The temperatures in the turbulent wedge of the nose cone area were approximately 1,900 degrees F – which was a little lower than predictions, but consistent with observations from STS-28.

The main area of concern was heating after the trip region became established. The lack of any Reaction Cured Glass (tile coating) “melt or flow” leads to the conclusion that most temperatures were less than 2,500 degrees F – with predictions of around 2,700-2,800 degrees F.

Documentation claims the peak temperature measured was approximately 2,000 degrees F, while pre-flight predictions were nearly 3,000 degrees F.

Post flight scans of the OML (Outer Mold Line) shape of the tiles in the protuberance area show no discernible change in the surface of the tiles.

One unexpected benefit of the multiple observation methods was the measurement of what’s called an Asymmetric Boundary Layer Transition (ABLT).

This occurred on the opposite side from the protuberance at Mach 10.5 – within limits for a normal BLT at Mach 11 – from some sort of “roughness” on the vehicle.

Post-flight GN&C assessments, along with data from the additional thermocouples and imagery from the HYTHIRM project, isolated the source of that ABLT to a region near the starboard side of the nose gear door.

Such high resolution data might be able to pin down the source of airflow tripping. However, given the lower speeds that such a situation can occur, ABLT is not considered a significant issue.

Next up for BLT is to increase the size of the protuberance to 0.35” – to be installed on Discovery for her STS-128 flight. The larger wedge is expected to trip the boundary layer at around Mach 18, provided information on higher levels of heat.

HYTHIRM is now preparing for the STS-125 entry, but has indicated readiness for being involved with the STS-128 experiment.

L2 members: Documentation – from which most of 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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Thrust Tail-Off Imbalance:

The first issue relating to the SRBs discussed at the SSP FRR (Space Shuttle Program Flight Readiness Review) pertained to the thrust tail-off imbalance noted during the STS-119 mission in March.

“STS-119 GN&C (Guidance Navigation and Control) Quick-look showed departures from PE flight history for roll and yaw attitude error…” notes the Reusable Solid Rocket Motor (RSRM) FRR presentation, available for download on L2.

While SRB thrust tail-off imbalance occurs on every mission, strict guidelines are used during the casting/pouring of the SRB segments’ propellant at the ATK factory in Utah to minimize all aspects of thrust imbalance during SRB flight.

However, the STS-119 event followed the STS-124 thrust tail-off imbalance in May 2008 and the less severe event on STS-126 last November.

As a result, the SSP has provided the GN&C community with all RSRM reconstruction data to support their analysis of the various flight control systems responsible for detecting this type of imbalance and taking the necessary action to correct the vehicle’s attitude/pitch/yaw accordingly.

For this, the GN&C community has been tasked with identifying any “design, process, and material factors” that could have/could be contributing to the thrust tail-off phenomenon.

In addition to the GN&C investigation, the SSP has developed a working theory, which pertains to a burn rate variation.

“Primary contributor to trace shape variation observed on STS-119, STS-124, and STS-126 is a burn rate variation and location of added mixes in the segments,” notes the presentation.

In addition to this theory, several upgrades have been added to the engineering, manufacturing, and analytical controls to “keep thrust imbalance on future flights well within CEI requirements.”

As such, an extensive review of the propellant casting process for STS-125 and subsequent flights that will use already poured SRB segments has been conducted, resulting in clearance for flight for all of those segments.

O-Ring Modification and LCC Contingency Temperatures for Heater Failure Scenario:

An additional change to the SRBs on STS-125 relates to the replacement of the fluorocarbon O-rings with a newly developed V1288 O-ring in the field joints of the SRBs.

The V1288 O-rings are new low-temperature fluorocarbon O-rings that were developed to “improve resiliency at lower temperatures with no degradation to other performance characteristics,” notes the RSRM presentation.

These new O-rings will allow the Space Shuttle to fly with higher safety margins and/or at lower temperatures.

The basis for verifying these new O-rings for flight included, but was not limited to, Anchors modeling (with showed compliance with all CEI tracking requirements), high temperature sealing capability that was equivalent to the O-rings used on STS-119 and several previous missions, splice strength that showed “no degradation with age,” and an ablation and erosion of less than half that of the previous O-ring flight model.

Additionally, five static firings were conducted to test the new O-rings. “V1288 forward field joint fired at 58 degrees F on TEM-13 (joint heaters not activated – no hot gas into J-leg),” notes the FRR presentation.

These O-rings flew successfully on ATK BSMs on STS-122, STS-123, STS-124, STS-126, and STS-119 – which added confidence to the application of these O-rings in the RSRM segment field joints on STS-125 and subsequent flights.

Furthermore, the RSRM presentation to the SSP FRR also notes changes to the minimum allowable temperatures for the SRB field joints.

Should the SRB heaters fail during the countdown, the SSP FRR presentation notes that the minimum allowable sensor temperature for the field joints will 44 degrees F, with the minimum sensor temperatures for the Igniter-to-case Joint and the Nozzle-to-case Joint at 70 degrees F and 62 degrees F respectively.

These minimum allowable temperatures will be “Automatically applied after valid (measurements violate) 86 degrees F Launch Commit Criteria (LCC) redline,” notes the RSRM presentation.

However, the J-leg has the potential to experience “low temperature performance degradation” because the J-leg becomes stiffer and shrinks in colder temperatures.

“RSRM designed to maintain J-leg axial engagement at ignition for temperatures from 90 degrees F down to 40 degrees F,” notes the SSP FRR presentation.

However, a full up test of the field joint thermal protection system has not occurred at the lower 44 degrees F limit.

In fact, the lowest tested temperature is 56 degrees F with no humidity conditioning. During those tests, there was no hot gas penetration past the J-leg tip.

This means that during a launch scenario with a 44 degrees F temperature reading, there is an increased potential for gas penetration into the J-leg because of “rubber shrinkage at colder temperatures.”

Nevertheless, while a full up test of the field joint thermal protection system at the 44 degrees F limit has not been conducted, multiple tests with intentionally flawed components have been undertaken.

Through all these tests, the RSRM presentation notes that “no capture feature O-ring failure or primary O-ring erosion” occurred; in fact, “hot gas to primary O-ring required intentional flaw alignment of every redundant feature.”

Furthermore, “Potential opening of the J-joint, caused by cold temperatures, creates a less severe environment or less severe gas impingement than a flaw focused on the capture feature O-ring,” notes the RSRM presentation.

In all, the thermal protection system for the RSRM segments is certified for flight. Intentional flaw testing and analysis shows compliance with both upper and lower temperature extremes as well as flaw size extremes that may be present as a result of the segment-mating process.

In summary, all O-ring seals and joint thermal protection systems meet all the necessary flight requirements at 44 degrees F. Therefore, STS-125 and subsequent flights are safe to fly with the new O-ring configuration under the failed heater field joint contingency temperature of 44 degrees F.

Engineer Camera Repositioning:

In addition to the internal modifications, NASA engineers have repositioned the Right Hand Forward Skirt Aft Pointing (FSAP) camera on the exterior of the SRB.

The change, which Shuttle Program Manager John Shannon noted during the FRR Briefing last Thursday, was done at the request of the Debris Integration Group.

The precise reason for the modification is to gain further engineering data on the inter-tank region of the External Tank – an area of the tank that has experience minor, yet consistent, foam loss over the last several flights.

This camera re-configuration has flown once before, on the STS-120 mission in October 2007. That repositioning was performed to gain a wider view of the newly designed Ice Frost Ramps.

Nevertheless, subsequent flights from STS-120 all utilized the previous SRB camera configuration – a configuration which debuted on STS-121 in July 2006.

For STS-125, only the RH FSAP camera will be repositioned. Both FSAP cameras will be repositioned for STS-127 and subsequent flights.

L2 members: Documentation – from which most of 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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STS-400/127 Flow:

Endeavour spent a week inside the Vehicle Assembly Building (VAB), prior to rolling out of High Bay 1 shortly before midnight local time.

Engineers were called to stations two hours ahead of first motion, after completing the retraction of platforms that had surrounded the vehicle during ET mate and Shuttle Interface testing (S0008).

“A5214 Shuttle Transfer and Mate to Pad B: “E”, “D” and “B” platform retracts are complete. S0008 Shuttle Interface Testing is complete. SRB HPU checks are complete,” noted pre-rollout processing information on L2. “The SSV has been powered down in preparation for rollout. SRB Hold-down Post Firing Line Checks are complete.”

Only three minor issues of note were worked during Endeavour’s VAB flow, two relating to orbiter camera systems, and one relating to Endeavour turning herself off during an unexpected power loss inside the famous building.

“During S0008, an unexpected power loss occurred resulting in Orbiter/SRB power down (resolved),” added processing information. “During ET Sep Camera testing, the flash module did not flash during testing,” which has also been resolved, although engineering evaluations will continue, due to similar issues with Discovery’s ET camera during STS-119.

“While attempting to download images from ET/TPS DCS Camera to A31P laptop, the following error message was received: ‘An error was detected with reading images from card, retry’,” was noted as the only other problem during the VAB flow. Further troubleshooting resolved the issue.

The Rotating Service Structure (RSS) is not due to be retracted around Endeavour until Monday, which – thanks to Atlantis’ RSS on Pad 39A being retracted on Friday – will allow for the stunning photography of both shuttles being visible on the pads, as was last seen prior to the on orbit issues with Hubble, which ultimately delayed STS-125 last year.

See more: Click here for recent STS-400 related articles
See more: Click here for recent STS-127 related articles

GUCP Testing and Status:

Once Endeavour is put through her STS-400 flow on 39B, engineers will keep a close eye on the mating and installation process of the GUCP, in order to try and gain more data on a potential root cause to the leak observed during STS-119′s opening launch attempt – which caused the launch to be scrubbed.

“STS-119 / ET-127 Performance Summary: Pre-launch: 1st loading resulted in scrub/LCC (Launch Commit Criteria) violation due to GH2 leakage at GUCA (>40,000 ppm. Flight seal/QD (Quick Disconnect) replaced,” noted a post mission IFA (In Flight Anomaly) review presentation on L2, written by the MAF (Michoud Assembly Facility).

“Leakage occurred during transition from fast fill to topping. Vent valve opened when 98 percent level sensor indicated wet. Detected by leak detectors (LD 23 & 25) located in ground umbilical shroud. Isolates leak to either ground side quick disconnect (QD) or interface with flight seal.

“Contingency plans (vent valve cycling) unsuccessful in controlling leakage within acceptable limits. Launch scrubbed, flight seal/disconnect replaced. No GH2 leakage observed during subsequent loading. No other anomalous performance observed during loading.”

No root cause has yet been found, although the leading candidate has been noted on the latest documentation relating to the incident.

“No first-time hardware changes implemented for STS-119/ET-127 GH2 vent system. 31 previous loadings with only 1 leak observed (13,500 ppm). Previous leaks also observed during fast fill to topping transition,” added the MAF presentation.

“Most probable cause identified as momentary breach in flexible flight-seal to bellows probe due to ‘thermal shock’ of GH2/LH2 with vent valve in open position.

“Significant Disassembly Observations: Lower left pad was hard against skin. Other locations were not touching (0.014 – 0.030 gap / 0.001 requirement) indicating a pull downward and to the left. Peripheral seal compressed more on left side and toward bottom of GUCP.

“Left side pivot assembly in hard contact with pivot pin (pin would not rotate). Stain observed on external surface of bellows guard and peripheral seal at 6 o’clock position. Flight-side seal asymmetrically compressed at 3, 7 and 8 o’clock positions.”

However, as per usual, engineers will ensure the problem isn’t related to another factor, such as a problem with the alignment of the hardware on the tank. In order to check their procedures, STS-400′s flow included the addition of tape markers on the alignment pins, to allow the monitoring of the hardware for any movement during the process.

“GUCP Checkout: Engineering added a dev to apply tape to GUCP alignment pins,” noted Endeavour processing information. “The tape application is complete. The procedure on the GUCP Alignment will be worked at the Pad.”

The MAF document also included a full run down on what is required when mating the umbilical and plate to the tank, which is more complex than may be assumed.

“Installation Process: GUCP installed using three (3) guide pins to align. Install / torque pyro bolt to verify distance from tank (7.0 – 7.06”) and ensure proper bellows preload. Adjust pivot assembly feet to contact the umbilical hinge bracket pins and remove guide pins (recent change from hard-down preload requirement, last year).

“Adjust pads between GUCP periphery and tank skin to lightly touch (4 places). Install QD with use of 4 guide pins. Adjust pads (4 places) to verify parallelism and take measurements (Checkout cell and integration cell). Helium leak check at around 6 psig.

“Post vent line installation. Adjust pads (4 places) to ensure around 0.001 clearance and ensure feet contact hinge pins. Helium leak check at around 6 psig.”

Engineers don’t expect the same issue to cause a problem for STS-125′s countdown in less than a month’s time, but have taken precautions on both Atlantis’ ET-130 and Endeavour’s ET-131.

“ET-130 vent disconnect hardware removed, inspected/re-built and replaced in VAB. Micro-fibers observed on flight seal emanating from corners of seal (around 1” length, 0.0003” dia., max). Fibers inherent to manufacturing process and accepted use-as-is,” added the presentation.

“Seal compression (>10x max fiber dia.) due to probe loading sufficient to either liberate or cold flow fibers into seal parent material. Similar fibers observed on seal installed and successfully flown on ET-127. No significant observations noted during disassembly and rebuilding of QD.”

“ET-131 flight seal re-inspected and replaced due to small, isolated indention on sealing surface. Indention not observed / documented during multiple visual / tactile inspections at MAF and initial inspection at KSC (cause indeterminate). Condition not consistent with observations noted on ET-127 seal.”

These precautions have already avoided the STS-119 issue from becoming a topic of concern at next week’s SSP (Space Shuttle Program) Flight Readiness Review (FRR), with managerial approval to fly as-is with the next two tanks.

“Root Cause Fault Tree Investigation and Tests In Progress .STS-125 (ET-130) and LON (ET-131) Hardware and Installation Re-Verified,” confirmed the document. “No Constraints to Flight Identified.”

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

Related posts:

1. STS-400 rolls out of VAB – STS-125 payload delay to Saturday A problem during the preparation of Atlantis’ Hubble Servicing payload...
2. STS-126: Super smooth Endeavour easing through the countdown to L-1 A loose washer on a ground support carrier plate is...
3. Dual flow ballet for Endeavour and Atlantis – De-stack debate Preliminary milestone schedules have been created for the complex dual...

Most of the issues reviewed were known about as and when they occurred during Discovery’s mission, and only a handful of elements requiring further evaluation – such as the issue with the ET Umbilical Well Camera, which failed to flash more than once, along with issues downloading any usable imagery of the External Tank post separation.

“IFAs: There were no significant issues with any of the IFAs but the flight rationale for the partial Tyvek cover release and more information on the Umbilical Well Camera Flash/Download problem will be discussed at the PRCB (Program Requirements Control Board) meeting,” noted an L2 acquired 8th Floor (MOD) summary on Monday.

“MOD (Mission Operations Directorate) presented one IFA for the Abort Light command being inadvertently sent prelaunch. There is one other potential MOD IFA for WFCR2 (GNC console) sluggish performance.

“The Loss of ISS to Ground Voice during the RPM (Rbar Pitch Maneuver) was briefed as an item of interest. MOD is tracking this item with an ISS anomaly to ensure adequate closure prior to STS-127.”

The full STS-119 IFA review consisted of 15 presentations – all available on L2 – ranging from the state of the launch pad, propulsion systems, and flight software. Below is the review of STS-119′s boosters.

RSRM IFA Review:

STS-119′s boosters performed as expected, bar a slight issue with a tail-off thrust imbalance – last seen during STS-124′s ascent last May.

The imbalance is caused when one booster loses pressure during burnout slightly faster than its opposite number, causing the stack to yaw slightly – which usually results in the SSMEs (Space Shuttle Main Engines) and/or the SRB TVC (Thrust Vector Control) system countering to keep the shuttle on the correct trajectory.

“All RSRM countdown parameters were within limits and within family. Overall performance of both RSRM motors and all ATK BSMs (Booster Separation Motors) excellent and well within requirements,” noted the ATK IFA presentation on the Reusable Solid Rocket Motors.

“RSRM tail-off thrust imbalance slightly outside of historical family (but within statistical expectation) at discreet time intervals. Overall performance of both STS-119 (RSRM-103) motors and ATK BSMs were excellent.”

The lack of dedicated section on the tail-off thrust imbalance, with only passing mentions on some of the other IFA review presentations, points to the issue requiring no further action. During STS-124′s post flight IFA review, several follow-up presentations were required for further understanding.

Elsewhere on the boosters, seven “squawks” – booster speak for an issue – were noted on STS-119′s RSRMs, which is usual and slightly lower than some recent flights.

“4 inch circumferential crack or unbond detected on the RH (Right Hand) center field joint aft RT455 ramp at approximately 250 degrees,” noted one of the squawks found on the boosters during post-retrieval inspections.

“Crack was probed and appeared to extend the full width of the ramp. Cracked area exhibited evidence of cohesive failure in the RT455 material with no evidence of a void or unbond, indicating impact rather than processing problems

“As the impact was on the aft ramp and showed an aft, moving forward orientation, this could not be an ascent concern.”

Such damage can be caused when the boosters impact the water, following their parachuted return to the ocean after the two minute assist of the shuttle during first stage flight.

However, every inch of the returned boosters are examined for any “out of family” area of interest, even if it had no detrimental effect during powered flight.

An example of which related to foreign object material found inside a safety and arming device, following it strip down after flight.

“Foreign material (fiber) was found in Arming Monitor Serial Number 0000021R12; part was refurbished in Nov 2006, prior to any recent corrective actions,” noted the presentation. “Fiber was located on switch deck insulator. Foreign Material had no effect on A-M operation.”

This device was also noted on another squawk, relating to a cracked switch (see left).

“Cracked switch upper deck was found after disassembly in Arming Monitor Serial Number 0000021R12. Recent corrective action has re-inspected all parts in inventory; however, this S&A was refurbished prior to recent corrective actions (November 2006),” the presentation added.

“Crack had no effect on Switch Deck, A-M, or S&A Operation. Cracking mechanism is understood. Brittle molding material may crack thru mold tool pinholes when removed and go unnoticed through several refurbishments.”

The other squawks related to excessive grease on a vent port plug, more foreign objects, and another crack – this time on the ignitor chamber insulation, which was not deemed to be a problem.

RSRB IFA Review:

Separate from the RSRM review are the Solid Rocket Boosters (RSRB), which were reviewed by the United Space Alliance (USA). A total of 14 squawks were found on STS-119′s SRBs.

A problem with the SWAR (Sea Water Activated Release) ‘failures to release’ was again noted, this time with three of the devices on the RH Booster – which is a known condition that has occurred on a number of flights in succession now.

The SWAR provides a method of disconnecting main parachute from SRB after splashdown, with the immersion in seawater closing an electrical circuit to release a shear pin from the riser about two seconds after immersion.

The SWAR was fully implemented in 1998 on STS-95, in order to increase diver safety by eliminating need to cut parachute lines. Since STS-122, the problem has been heavily documented on both post flight and pre-flight Flight Readiness Review (FRR) presentations.

The problem is believed to be associated with a known failure mechanism with the pyrotechnic train, when the primer fails to breach the stainless steel booster closure cup with enough energy to ignite charge in booster.

Other issues noted included: “10 sec Reefing Line Cutter (RLC) fired earlier than Lot average. A retention pin not retained in clevis hole. Booster Trowellable Ablative (BTA) delamination on Booster Separation Motor (BSM) triple mount. Several pieces of green and red tape found on various elements of the booster (making up for four squawks).

“Slice on aft Integrated Electronic Assembly (IEA) forward face center cover Thermal Protection System (TPS). Possible impact on External Tank Attachment (ETA) ring forward face. Aft Integrated Electronic Assembly (IEA) J7 code plug not safety wired.”

One highlight of the RSRB IFA presentation was the performance of the modified Hold Down Posts (HDPs), which suffered an anomaly during STS-126′s launch, spreading debris across the launch pad, including a large metal spring – which would obviously be a major debris impact hazard for the shuttle, as noted in several presentations on the incident, the modifications, and the risks.

Click Here for NASASpaceFlight.com’s articles on the HDP issue and resolution.

Interestingly, there appears to have been another failure on one of the posts, which would have resulted in an identical debris hazard as seen on STS-126, had it of not been for the newly modified Debris Containment System (DCS) on the HDPs – as was called for during the redesign post STS-126.

“Debris Containment System (DCS) on HDP 5 engaged stop blocks. Excellent support from team enabled new design implementation on STS-119/BI135. STS-126/BI136 IFA would have reoccurred without stop blocks. Stop block modification performed as designed. All debris contained.”

That secondary retention feature, which saw the addition of two tapered stop blocks, replaced the previous anti-rotation device.

The physical threat to the vehicle relates to either large pieces of debris – such as the large metal spring found in the north trench after STS-126 – or small sharp fragments of metal – such as tube lock clips – potentially impacting an OMS Pod, a SSME (Space Shuttle Main Engine), an aft Reaction Control System (RSC) “venier” thruster, or part of the vehicle’s TPS (Thermal Protection System).

Given STS-119′s lift-off saw an issue with one of the HDPs, the first live test of the modified system has – in effect – been carried out, and was found to be a huge success.

Further IFA review articles will follow.

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

Related posts:

1. SRB Holddown posts undergoing redesign evaluation ahead of STS-119 Engineers will meet in the middle of January to push...

STS-125 Processing Flow Latest:

Atlantis – preparing for her May 12 launch date to the Hubble Space Telescope – is enjoying a smooth pad flow out at 39A, as she moves into hyper servicing and payload arrival preparations.

“Will continue with S0024 preps. That will lead to a Call-to-Stations Tuesday night, and hyper servicing on Wednesday and Thursday of this week,” noted the latest Shuttle Stand-Up/Integration report on L2. “Next week preparing for the payload delivery on April 18.

“Range Safety System validation (first motion checks) are complete. Helium signature test and Ball Seal Leak Checks are complete and good; GO2 blank off plates removed.”

This week will also kick off the Flight Readiness Reviews (FRRs) for STS-125, opening with the second MOD FRR review – following the previous FRRs last September, before the mission was delayed – outlining the upcoming mission in detail.

This will also coincide with the Mission Management Team (MMT) undergoing a pre-brief, which will be headed by Leroy Cain.

“Folks have a lot of other things to do between now and STS-125, and have a lot of other meetings on the schedule. We won’t do it if it does not look necessary,” noted Mr Cain on the Stand-Up.

“On STS-125, there will be a MMT pre-brief. It will be scheduled this week. It will be a challenge to find a place to put it on the calendar with the meetings we have in place.”

Flow Control Valves:

As with STS-119, more discussion will take place on the Flow Control Valves (FCVs), following the incident observed during STS-126′s ride to orbit late last year. This in turn led to a major part of the FRR process being dedicated towards the gaining of Flight Rationale ahead of STS-119.

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

Including two Special PRCBs (Program Requirement Control Board) meetings, the launch date was delayed until managers and engineers were certain they had the right amount of confidence in flying the three FCVs on Discovery – without the requirement to standdown for a redesign, which some engineers had been calling for.

As per usual, the decision to fly with three “cherry picked” valves that had previously flown without issue has been proven to be the correct decision, with no anatomies noted during Discovery’s ascent.

That confidence has been boosted via flight inspections, proving the valves didn’t suffer from cracks – which is the driver for an eventual liberation, as found with one of Endeavour’s valves.

“On OV-103 (Discovery’s) FCVs, did get them out last week and to Vacco over the weekend and inspected,” noted the Orbiter Project at the Johnson Space Center. “Two of the three looked really good, no cracks. The other one picked up a little scratch.

“We will have to figure out where that came from, and how to get it turned around. Right now the first blush is that we might have to do some flow-balance testing on it. Will work through that. It looks like the FCVs came through pretty well.”

Due to the nominal performance of the valves, the sets of FCVs that are set to fly with Atlantis on STS-125, and Endeavour on STS-127 (and STS-400 if required), will be likely to gain the required flight rationale without the need for a major discussion at the FRRs.

A proposed metal plate that would “beef up” the most ‘at risk’ area of the downstream plumbing in the Main Propulsion System (MPS) – known as the 90 degree elbow bend – is now unlikely to have a place in future plans, due to the reduced threat of a liberation, which would have to be on a greater magnitude than that observed during STS-126 to cause damage in this area of the MPS.

In fact, the encouraging post flight inspections of the valves, from which no cracks have been found, will aid flight rationale for at least STS-125.

“The FCV data is very important, and getting those three valves off of STS-119 is the first time we’ve had a chance to look at just one flight’s performance in terms of crack growth,” added the Orbiter Project.

“It is good to see that we had no cracks on the valves within our detectability limits pre-flight, and then after flight we don’t see any as well. It is good news for our flight rationale.”

No major issues are expected to be discussed when managers close out STS-119 via what is called the post-flight IFA (In Flight Anomaly) review, to be conducted during Thursday’s PRCB meeting – thanks in part to Discovery’s clean mission.

“On STS-119 MMT debrief, do not have much to talk about. For most of the folks solicited, we really don’t have much to debrief from a MMT standpoint,” noted Mr Cain on the Stand-Up report.

Items likely to be discussed are the usual “squawks” that are noted on most Solid Rocket Booster (SRBs) IFA presentations, along with the problem with the ET Umbilical Well Camera, which failed to properly execute its flash – or download imagery – during post ET-sep.

“Still working on the ET camera off of STS-119. Got it back to JSC. Did some troubleshooting, and had the same indications as on flight with the camera,” added engineering notes. “Sent the camera on command and nothing happened; the laptop couldn’t find the camera. They opened of up the box and couldn’t find anything.”

Any items of interest found during the STS-119 post-flight IFA review will be added to the STS-125 SSP (Space Shuttle Program) FRR documentation.

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

No related posts.

The damage was first spotted late last summer during a routine imagery survey, in order to check for any damage – usually caused by MMOD (Micrometeoroid Orbital Debris) strikes – to the outside of the Station 

Imagery found that one of the eight radiator panels on the S1 array – which each have two thermal face sheets, one on each side, epoxy-glued and autoclaved to the honeycomb structure of the radiator – was observed as peeled back. These face sheets have a thermal surface coating designed to maximize heat reflection and absorption transfer to space.

The radiators are used to remove heat from the Station, via a loop filled with ammonia, supplied by the ETCS accumulator, and backed up by the Ammonia Tank Assembly (ATA).

Though the cause of the damage has not been confirmed, the survey was called after Russian spacewalkers reported one of the Service Module thruster covers had impacted the S1 radiator, after it was jettisoned during a spacewalk last year, making it the leading candidate – especially since all the other panels remain in good shape.

Initially it was thought the radiator would continue to work without issue, with the opening report last year noting: “The thermal team reported there is no significant change to the heat rejection capability so currently there are no changes to operations planned.”

However, Station managers decided to utlize STS-119′s EVA time to take a closer look. This task remained, despite Discovery’s mission content being reduced by one EVA.

During STS-119′s EVA-2, the spacewalkers took photography – including thermal imagery – of the panels to check for hot spots and allow for a closer inspection of the damage on the ground. Those evaluations have taken place and have revealed the issue as potentially serious.

“S1-3-2 Radiator Peeled Back Panel Status: Engineering and Boeing brought in a status of this situation,” noted an expansive ISS update in this week’s Space Station Program Control Board (SSPCB) meeting notes, available on L2 – before outlining some of the basics of the radiator system.

“The board was reminded that the Ammonia Tank Assembly (ATA) acts as an accumulator for the ETCS system. The built in ETCS accumulator does not have sufficient volume to be able to react to the orbital thermal environmental variation with the ATA supply valves closed.

“At this point, the structures folks indicated that with a single panel peeled back from the S1-3-2 radiator, general on orbit load cycles are now reacted at ammonia flow tube weld joints vs the skin of the panel.

“The honeycomb substructure will not react loads without the adhered panel skin. Because of this phenomenon, the engineering team believes that we are at risk for the weld to fatigue and fail and subsequently create a leak in the system.”

The report went on to outline the impacts of a leak in the loop, noting the ISS crew would be alerted by their Failure Detection, Isolation and Recovery (FDIR) system during such an event, in turn allowing for either the crew or controllers on the ground to isolate the leak.

“(However,) the board was reminded that the current FDIR only alerts the crew or ground to a potential ammonia leak when the accumulator pressure drops to 170 psia to protect the pump.

“Since there is an accumulator at the pump assembly, the entire ATA tank would be emptied prior to auto FDIR annunciating the problem and shutting down the loop. Once notified of a leak, it takes the crew around 30 minutes to manually isolate a radiator panel or the MCC around 15 minutes.

“However, current hazard constraints and flight rules inhibit isolating radiator panels under insolation to ensure that you do not over pressurize an isolated flow path.”

Should such an event take place, the Station would not be without a full supply of ammonia for long, with STS-128/17A due to carry a new ATA to the ISS this summer – a regular changeout, with another ATA set to fly on STS-131.

However, managers are required to work options for at least the interim, which includes flying a spare radiator – likely to be a full S1 replacement – on a future shuttle mission.

That option includes bringing back the current S1 radiator system for evaluation of root cause on the ground – allowing for important lessons learned as the ISS heads into the next decade.

“The board gave several actions. First was to see what it would take to fly a spare to orbit and perform an R&R (Removal and Replacement) and to bring back the failed system to determine the root cause,” added the report.

“Second, was to determine what it would take to ensure that the community was OK with venting this particular panel in the near future to protect for a loop leak.

“Third, was to investigate potential software changes, hazard waivers, etc to help MOD and the crew detect and isolate failures to individual panels with minimal loss of ammonia.

“This may require changes to the software to use ATA tank quantity/pressure vs accum pressure for detection, possible waiver of the radiator over pressurization constraint, etc.”

Such issues once again highlight how the proposed shuttle extension may provide a major benefit to the ISS, with not only the ability to carry major replacement hardware to orbit, but also the down mass capability that may be called upon, as seen with the potential option to bring the S1 Radiator back to Earth.

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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Discovery touched down on KSC runway 15 at 15:14:45 local time on Saturday, completing a successful mission installing the final solar array truss to bring the ISS to full power.

De-orbit burn, re-entry, and landing performance were all nominal, with entry controllers reporting the flagship orbiter enjoyed a faultless return home.

Once safed at the Shuttle Landing Facility (SLF), S0069 Integrated Roll-In operations picked up. Orbiter tow first motion from the SLF to OPF3 was at 18:46 local, before she was spotted in OPF-3 at 20:55. Fuel cell shutdown/ground power transfer was completed at 00:30 on Sunday.

TPS assessment began at 15:40 on Saturday, with engineers documenting most areas of Discovery’s heatshield, prior to being towed back to the OPF.

“Overall vehicle looked good. There was one protruding Ames gap filler, it was the gap filler seen on orbit,” noted the TPS assessment report on L2. “There were three instances of missing putty repairs.”

A special Boundary Layer Transition (BLT) Detailed Test Objective (DTO), which involved one tile on Discovery’s belly protruding slightly, was also inspected, with no damage reported in the local area.

“BLT protuberance did not exhibit significant slumping or erosion,” added the report. “Structural integrity was maintained. BLT protuberance tile did not appear slumped, although minor glazing was noted along the trailing edge of the fin. Streaking was noted along 3 tiles downstream of the protuberance. ”

Also reported were the thermal barriers on the Nose Landing Gear Door (NLGD), which provided close up views of an item of interest found during Flight Day 3′s RPM photography.

“On orbit ‘fray’ on Forward NLGD thermal barrier was actually frayed edge of patch, no damage to weave of fabric noted,” added the report, before listing other areas of interest on the forward section of Discovery.

“Right portion of Arrowhead Blanket was protruding .05” around attach point. Chin panel -441 gap filler had one tear on the right side approximately 1” long. Right hand side gap measurement was .180, left hand side gap measurement was .170, and the center measurement was .210.”

“Unknown marking on the V070-391035-313 tile was an orange marking approximately 2” long, no protrusion noted. Large amount of degradation seen on FRCS (Forward Reaction Control System) thermal barrier R4R. Damage was noted in previous repair location.”

For Discovery’s Main Landing Gear Doors (MLGS), the thermal barriers also appeared nominal, while a gap filler – noticed in the RPM photography, actually survived re-entry, as opposed to coming lose during Flight Control Surface checkouts on Flight Day 12, or during re-entry.

“Gap filler on the left hand inboard elevon was still present. The protrusion appeared to be the same as on orbit with no obvious effects of overtemp. The gap filler was confirmed to be 3 plies of Ames.”

“Left hand inboard elevon damage appeared to be the same as on orbit, with and estimated depth of .3-.4”. Rounding of damage edges indicates evidence of possible heating.*

Other items of interest included missing putty repairs on three tiles – which can be expected, a broken “piano key” tile on the body flap, and a protruding gap filler on one of Discovery’s OMS Pods – which have performed well since the couple of incidents with torn stitching between the tiles and the blankets.

“Discolorations noted on orbit aft of the LH ETD were not noted as abnormal on the runway,” the report added. “Piano key tile above the body flap had a large portion of the cantilever broken off.

“Tile between engines 2 and 3 had an edge broken off. Piece of material debris identified on top of the RH (Right Hand) side of the body flap. Source unknown (see left image).

“OMS protruding gap filler noted on orbit as 500-001 was visibly frayed. It is notable that this portion of the gap filler was not noted as protruding on orbit.”

Further inspections on Discovery’s TPS are being conducted in the OPF, ahead of final deservicing tasks and preparations to enter her into the STS-128 processing flow, which has technically started with post STS-119 work.

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. STS-119 L2 Section includes same collections of all MMT presentations, images and video, now over 3,000 mb in total.

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

Discovery has marked yet another issue-free mission on orbit – highlighted by the successful installation and deployment of the S6 integrated truss segment and solar array wings – with only a handful of minor items of interest for the MER (Mission Evaluation Room), with shuttle manager John Shannon previewing the weekend landing as an amazing feat.

“These are great days in space,” Mr Shannon said, opening the latest Shuttle Stand-Up/Integration report on L2. “OV-103 (Discovery) undocked from Station, giving us a chance to see the fully completed truss assembly.

“The 18 Soyuz safely lifted off, headed for Station. At this time, there are 13 human beings in low-earth orbit – an amazing feat. This flight has been unbelievably smooth. Everyone worked extremely hard getting to this launch, with many weekends worked and many hours of overtime.”

“STS-119/15A had2 a very successful docked mission,” added MMT chairman Leroy Cain, who noted he “is very proud of the whole team.”

The Soyuz TMA-14 launched on Thursday, carrying the next ISS commander Gennady Padalka, flight engineer Michael Barratt and space tourist, Charles Simonyi.

Docking at just after 1pm GMT was successful, although Padlaka had to complete the approach manually, following what appears to have been an anomoly with the KURS automated docking system.

Confirmation Discovery is safe to return came via the DAT (Damage Assessment Team) report to the MMT (Mission Management Team) on Friday, following an overview of the Late Inspections that were carried out on Flight Day 12.

No items of concern were found on Discovery’s TPS (Thermal Protection System), which has once again proved the major advancements by the Michoud Assembly Facility (MAF) and the SSP (Space Shuttle Program) in reducing foam and ice liberation from the External Tanks during ascent.

Had a major problem been found with the heatshield, Discovery was still – as pre-planned – close enough to the ISS to return to the Station and wait for rescue by the LON (Launch On Need) vehicle – which would have been Endeavour.

That LON requirement has been stood down by the successful TPS review by DAT, and Discovery’s opening task on Flight Day 14 was to perform burn to finalize the orbiter’s separation from the ISS.

The crew awoke on Flight Day 14 to a song from ABBA, before heading into deorbit preparations, which resulted in this afternoon’s SIMPLEX burn (a two-OMS retrograde burn), slowing Discovery orbital velocity and taking her out of orbit for landing just over one hour later.

L2 Members can download several high quality re-entry videos, via a handheld camcorder on the flight deck, from deorbit burn to post landing, with crew audio. *Click Here*  for free trailers.

Powering the hydraulic systems that control Discovery’s Flight Control Surfaces (FCS) – which were checked out on Flight Day 13 – were three APUs (Auxiliary Power Units), although this is based on redundancy, as only one is required for re-entry and landing.

An issue with APU 2 was noted late in the mission, although this didn’t hold any impact for Discovery’s final hours prior to her wheels stopping on the Shuttle Landing Facility (SLF)

“APU 2 heater thermostat dithering. This is a problem seen numerous times before and is characterized as a “set point” change,” noted the MER report on L2. “No impact to flight or to APU operation. May require replacement post flight.”

Discovery’s re-entry also mark a shuttle first, with data being gathered by a special Boundary Layer Transition (BLT) Detailed Test Objective (DTO) that is installed on her TPS.

The DTO will attempt to gather data during entry regarding the aerothermal effects caused by the boundary layer transitioning from laminar flow to turbulent flow at a high Mach number. The test was originally set to debut with Endeavour on STS-126.

“Boundary Layer trip induced by a protuberance placed on a lower surface tile on the port wing,” noted associated documentation on L2. “Protuberance height of 0.25 inches is expected to trip boundary layer at Mach 15. Thermocouples installed on protuberance tile and downstream tiles will capture data.”

Before this DTO was approved by shuttle managers, an extensive review was conducted to ensure that the changes would not affect the performance of the Orbiter during re-entry, and that the protuberance tile was placed in an area that would minimize the occurrence of damage to the protuberance tile by ascent debris.

Images taken from Flight Day 3′s RPM – used to take hi-res photography of Discovery’s belly – showed the tile area in question was clean and ready for Saturday’s re-entry test.

Now Discovery has landing, she will head into S0069 (roll-in) operations, ahead of being spotted in her Orbiter Processing Facility (OPF). Post flight processing will begin on Monday, starting with opening TPS inspections and the safing of her power systems.

She will then begin flight processing for her next mission, STS-128, which was originally set to fly with Atlantis, ahead of realignment of the shuttle manifest.

Targeting launch for No Earlier Than (NET) August 6, 2009, Discovery will be prepared for a 13 day, 3 EVA, mission to the ISS that will include the flight of the TriDAR AR&D Sensor Detailed Test Objective (DTO), the next Boundary Layer Transition (BLT) DTO, and the first flight of the OI-34 flight software.

Also riding uphill with Discovery will be a new crew member for the ISS – Nicole Stott – as well as MISSE (Materials on International Space Station Experiments) 6A and 6B, SIMPLEX, MAUI, and SEITI.

However, the primary payload for Space Shuttle Discovery will be the MPLM (Multi-Purpose Logistics Module) Leonardo – returned from the highly successful STS-126 mission in November – and the Lightweight Experiment Support Structure Carrier with an Ammonia Tank Assembly.

Interestingly, assessments on how to accelerate STS-128/17A are in progress, according to the latest Stand-Up report, which will be discussed after the landing of STS-119.

Two more missions are planned for Discovery, STS-131 and STS-134 – the latter awaiting final approval, with the possibility of additional flights via shuttle extension.

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. STS-119 L2 Section includes same collections of all MMT presentations, images and video, now over 3,000 mb in total.

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Final Shuttle/Station transfers took place prior to undocking, mainly relating to human samples stored in cold bags, which was the cause of the change to the plan relating to the departure timeline.

Normally the hatches would be closed the day before undocking, but to ensure the samples remained within their “thermal clock” ahead of being handed over to scientists on the ground, hatch closure was delayed to as late as was viable.

Rendezvous tools checkouts also took place ahead of the farewell between the crews of Discovery and the International Space Station, before hatch closure and leak checks.

Following undocking, Discovery performed a full, one lap, flyaround of the Station, which provided the first images of the ISS with all four of its solar arrays deployed - thanks to the successful delivery and installation of the final integrated truss segment, S6.

ISS Commander Mike Finke was asking for video of the flyaround, eager to see his newly grown Station.

Once the flyaround was completed, Discovery performed separation burns to increase the distance between herself and the ISS. 

Refer to the live update pages for up to the second events, images and video.

Final checks of Discovery’s TPS:

Late Inspections will be completed before the distance between Discovery and the ISS are too great, allowing for the orbiter to return to the ISS in the event of serious damage being found during the final check of the Thermal Protection System (TPS).

This procedure, utilizing the Laser Dynamic Range Imager (LDRI) and sensor suite package on the end of the Orbiter Boom Sensor System (OBSS), will take place on Flight Day 12.

Given the lack of damage observed during Flight Day 2′s opening inspections and Flight Day 3′s RPM (Rbar Pitch Maneuver) – which only found a handful of items that required clearance by the DAT (Damage Assessment Team) on the ground – the procedure will provide a “before and after” overview of Discovery’s heatshield, in order to check for any damage during her docked phase of the mission.

This is required in case Discovery suffered a MMOD (Micro-Meteoroid Orbital Debris) hit whilst docked. While serious damage is highly unlikely, due to the protection provided by the ISS when docked, orbiters can still be susceptible to hits, especially on their windows and radiators – as seen on previous missions.

The critical area of the RCC (Reinforced Carbon Carbon) Wing Leading Edges (WLE) also have the ability to “feel” impacts on their panels, via the WLE Impact Detection System (IDS). Daily presentations on the WLE IDS have noted no “triggers” of concern during the docked phase.

The importance of ensuring the TPS is in good condition for re-entry is obvious, with the teams on the ground literally inspecting ever inch of the heatshield.

Due to the methodical nature of the inspections, even the slightest anomaly with the scans is raised to the Mission Management Team (MMT), as was one issue during Flight Day 2.

“Picture matching at the start of Stbd (Starboard) scan 2 while at pause pt 13 to image FD2 LDRI missed coverage of lower T-Seal (R7),” opened a technical presentation to the MMT on L2, which also relates to Flight Day 12′s Late Inspections.

The missing area of coverage, caused by a slight oscillation on the sensor package, is only a matter of inches across. However, thanks to the arsenal of data gained via the RPM and the WLE IDS - and flight history since Return To Flight – engineers on the ground already know the area in question has not suffered any damage of note.

“STS-119 FD2 – Missing LDRI Coverage of Lower Tee 7R: Missing coverage likely due to LDRI Flight Unit 3’s masking, oscillations and system stack up error,” added the presentation. “No need for additional imagery in this location.

“800 mm RPM imagery showed no damage (Detection Resolution 0.3”). No ascent WLE IDS triggers at the 7/8R interface. Coating damage in this region is acceptable due to increased lock side RCC thickness and redundant RCC on the Tee. Minor corrections to late inspection will adequately cover this area.

“To reduce the risk of this reoccurring for late inspection, we will make real-time adjustments to point the LDRI more like what was flown on STS-117 and STS-123 FD2.

“Half a cross hair adjustment falls within the alignment process that we have with Crew and the Flight Control Team (use this during training sims and flights). On FD4 spoke with PDRS (Payload Deployment and Retrieval System) about our half a cross hair adjustment plans and they are okay with it.”

One of the last items to be cleared was a gap filler on the left elevon area of Discovery, which was observed to be protruding.

The concern with protruding gap fillers relates to their potential to disrupt – or “trip” – the flow of the super hot gases the orbiter will race through during entry interface. Such an event is not a crew/orbiter safety issue, instead it relates to the possibility of increased TPS re-works once she returns to her Orbiter Processing Facility (OPF).

This final item was cleared over the weekend, following a peer review to ensure the gap filler presented no concern to the orbiter.

“On the mission, the TPS was cleared on Saturday. The team did a great job of working through the gap filler,” added the Orbiter Project at the Johnson Space Center (JSC) . “Looking forward to late inspection on Thursday.”

Such has been the “clean” performance of Discovery during STS-119, Mr Shannon once again praised the teams, before rallying them to one final push to return the orbiter and crew home safely.

“We couldn’t have a better vehicle on orbit. It’s just amazing,” Mr Shannon noted. “Great mission. Let’s keep our focus. We’re going to be flying this entire week. It’s been going extremely well, and we just want to finish it up the right way. Thanks for everything you’ve done.”

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. STS-119 L2 Section includes same collections of all MMT presentations, images and video, now over 3,000 mb in total.

Related posts:

1. Progress M-66 launches, heads for the International Space Station The Russian cargo ship Progress M-66/32P has launched from the...

 EVA-3:

With STS-119 reduced from four to three EVAs, due to the need to undock prior to the Soyuz cut out, EVA-2 was also replanned.

Conducted Swanson and Acaba, EVA-2 worked on P6 Battery replacement preps, deployment of the P3 and S3 Truss Payload Attachment Systems, P1/P3 Fluid Jumper connections/Radiator Beam Valve Module Thermal Cover removal, and P6 Power and Data Grapple Fixture retrieval.

However, issues were noted when attempts were made to unstow a cargo carrier attachment system (P3 NADIR UCCAS), caused by an incorrect installation of a locking pin.

“A hardware issue during EVA 2 prevented the deployment of the P3 nadir UCCAS,” noted on of the MMT department presentations on L2. “Real time troubleshooting was unsuccessful and the associated timeline impact caused several tasks to be dropped from EVA 2.”

Work on the locking pin was unsuccessful, leading to photography being taken for further evaluation on the ground, while the hardware was tied down until an EVA in the future can look into solving the issue at a later date.

EVA-3 tasks also included the relocation of a CETA (Crew and Equipment Transfer Assembly) Cart. Currently both CETA carts are on the port side of the MT (Mobile Transporter), one will be moved to the starboard side for STS-127 activities.

“S3 Outboard/Zenith PAS deploy: deferred from EVA-2 due to issues with the P3 UCCAS,” are among other tasks, along with the get aheads of: “LEE (Latching End Effector) B Lube: Lubricate the snares or SSRMS (Space Station Remote Manipulator System) LEE B side.”

Other get-aheads include: “S1/S3 Segment-Segment Attach System BBC Panel Reconfig and the installation of the CETA Coupler.

“S1/S3 Fluid Jumper install: same for the starboard side. P1 FHRC P-Clamp release: needed if/when it becomes necessary to replace the P1 FHRC. S1 FHRC P-Clamp release: same for the starboard side,” noted some of the other get-aheads, although not all of the items could be completed due to time available in the EVA.

Discovery Latest:

The Mission Management Team (MMT) met on Monday with no new issues in work with Discovery, with only a couple of new additions on the Mission Evaluation Room (MER) list over the weekend.

One note references an increased use of propellant by Discovery for this stage of the mission based on predictions, although that could be expected, following the use of her thrusters during the S6 Solar Array deploy, where she took control of the shuttle/station complex’s attitude in tandem with the Russian thrusters on the Station.

In addition, Flight Day 8 saw the precautionary DAM (Debris Avoidance Manoeuvre) being conducted by Discovery’s Digital Autopilot (DAP), which raised the Station away from a potential conjunction threat.

“A potential conjunction with orbital debris (Object 26264- CZ-4 Debris) was identified and required that a Debris Avoidance Manoeuvre (DAM) be performed to clear the ISS/Shuttle stack,” noted one MMT presentation.

“A retrograde delta V of ~0.9 feet per second (out of a targeted 1.0 fps) was generated by holding attitude in the undock attitude (ISS 0, 0, 0 roll, pitch, yaw) for 3 hours. The stack was then maneuvered back to the nominal Torque Equilibrium Attitude (TEA) before crew sleep.”

The other issue raised over the weekend related to a pressure anomaly on a GN2 regulator located in the midbody (midfuselage).

“After GN2 Repress on FD 6 the pressure downstream of the system 2 GN2 200 psig regulator gradually climbed to 267 psig over 20 hours,” noted an associated presentation to the MMT. “Rise in pressure attributed to an in specification leakage in a closed volume.

“The crew opened the system 2 water tank regulator to increase system volume and upon a subsequent waste water dump the pressure returned to a nominal 204 psig. The pressure has been monitored since the opening of the water tank regulator and the pressure has remained at around 204 psig.”

As of Monday’s MMT, no IFAs (In Flight Anomalies) or MER level “funnies” were in need of discussion, highlighting Discovery’s superb performance on this mission.

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. STS-119 L2 Section includes same collections of all MMT presentations, images and video, now over 3,000 mb in total.

No related posts.