STS-134 Processing Latest:

Endeavour is being processed inside her OPF-2 (Orbiter Processing Facility), ahead of her February, 2011 mission to carry the Alpha Magnetic Spectrometer (AMS-2) and Express Logistics Carrier 3 (ELC-3) to the International Space Station (ISS).

The 15,300lbs AMS-02 unit will undergo a milestone review next week, based on the changes made since engineers decided to replace the cryogenic super-fluid helium superconducting magnet with a permanent alternative – the reason the launch date slipped down the manifest.

“There will be a Delta Compatibility Review on August 6 for the AMS payload to ensure that all the changes made are still consistent with our engineering and their mission profile,” noted Flight Operations and Integration on the latest Shuttle Standup/Integration report (L2).

All three of her Space Shuttle Main Engines (SSMEs) were installed by Thursday of last week, and are now being put through closeout and interface procedures. Endeavour is currently enjoying the weekend off.

“OV-105 (OPF Bay 2): OIU (Orbiter Interface Unit) verification was successfully completed. SSME #2 was installed; all three engines are now installed. Closeouts continue,” noted the NASA Test Director (NTD) processing report (L2), which mentioned ongoing testing on the Orbiter Boom Sensor System (OBSS), which will remain with the ISS after Endeavour undocks.

“OBSS keep alive test was completed. SPEE premate testing was started and will resume once adapter cables are routed from Bay 3. Weekend work: None scheduled.”

Over in the Vehicle Assembly Building (VAB), engineers are stacking the twin Solid Rocket Boosters (SRBs) in High Bay 1 (HB-1), while External Tank (ET-138) continues it’s “shakedown” operations in HB-2E’s checkout cell.

“SRB BI-145 / RSRM 113 (VAB HB-1): L/R (Left/Right) Stud Tensioning; Need RT-455 pull test results. ETAR foam repair; PDL repair complete less closure. LA Joint Closeout; Cork pull test complete, on hold for PR (Problem Report) on ‘D’ dimension tool,” added the NTD report.

“ET-138 (VAB HB-2E): Bond Adhesion test repairs PDL (foam) application, trim and sand and final acceptance are complete, to engineering pre scaffold removal walkdown.”

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

Flow Control Valve Spot:

Most Shuttle followers will be only too aware of how the Flow Control Valves (FCVs) became an item of great interest, following the liberation of part of a valve’s poppet during Endeavour’s STS-126 launch in November 2008.

The finding led to the immediate inspection of the FCVs throughout the fleet, highlighted by Special Program Requirements Control Board (SPRCB) meetings and Flight Readiness Review (FRR) debates ahead of Discovery’s STS-119 mission.

The GH2 FCVs – of which there is one per SSME – are designed to provide the proper amount of pressurized GH2, while maintaining the ET LH2 tank flight pressurization limits.

However, one of the main concerns related to the potential of a large enough piece of the poppet liberating from the valve and impacting the downstream 90 degree elbow in the Main Propulsion System (MPS), which may cause an undesirable GH2 leak into the aft compartment.

FCV Specific Articles (Extensive): http://www.nasaspaceflight.com/tag/FCV/

Subsequent reviews of all FCV flight history and risk information revealed that the overall likelihood of a FCV poppet failure in flight is low. All the FCVs that have flown since have also undergone Non Destructive Evaluation (NDE) eddy current inspections, in order to spot any potential cracks forming in the valves prior to installation.

With no notable issues recorded by the valves since STS-126, the SPRCB and FRR conclusions and mitigation plans have again been proved to be correct. However, they are backed by highly experienced hands-on engineering teams at the Kennedy Space Center (KSC), who need to keep their eye on the ball at all times, and not just on areas of recent interest.

An example of their diligence was noted when one FCV on Endeavour was rejected via a tolerance problem, a five thousands-of-an-inch deviation from nominal, about the width of a sheet of paper.

“During installation of FCVs on OV-105 (Endeavour), one of the units failed an installation dimension requirement check,” noted the Orbiter Project Office (OPO) on the latest Standup report, noting the valve was sent back to its fabricator in California, who found the valve was missing one of its numerous – yet tiny – shims.

“That unit was sent back to the vendor where it was discovered that a 0.005 inch shim was missing. Orbiter is in the process of evaluating all the remaining units coming out of the vendor that have the proper configuration, and are confident that the units on the vehicle are in the proper configuration because they all passed the same installation dimension requirement check.”

A replacement valve has since been installed into Endeavour over the past few days and passed “mass spec” checks, confirming the new valve isn’t suffering from the same issue.

The spot earned praise from Mr Shannon on the Standup report, showing the teams are remaining extremely focused during what is a difficult time for the Program, with continuing lay-offs and uncertainty about the future after the fleet retires.

“Mr. Shannon said it was a good catch by the team installing the FCVs finding the tolerance problem; that is the way we want to do business,” he was noted as saying at the Standup meeting, before adding a message about the recent notices that informed nearly 1,500 workers they would lose their jobs in October.

“Please be compassionate and understanding as people’s lives are going to change, and we must still concentrate on getting the mission ahead of us done. It is vitally important that we do that, but it is a tough time for a lot of our team members. Please be aware of that and be compassionate about that.”

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Review of the Issue:

During Endeavour’s launch on November 14, 2008, “MPS (Main Propulsion System) engine #2 GH2 (Gaseous Hydrogen) flow control valve (FCV) LV57 appeared to transition from low flow towards high flow position without being commanded to do so,” notes the FCV Poppet Investigation Summary presentation to the Program Requirements Control Board (PRCB) on January 7.

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

Post-flight inspections of the valve revealed a liberation of ~87-degrees of the poppet head’s circumference.

This finding lead to the immediate inspection of the FCVs throughout the Shuttle fleet and the subsequent grounding of Discovery and the STS-119 mission until the cause of the poppet liberation could be determined or the integrity of the FCVs to set to fly with Discovery verified.

The GH2 FCVs (of which there is one per SSME [Space Shuttle Main Engine]), are designed to provide each engine with the proper amount of pressurized GH2 from the ET LH2 tank while maintaining the ET LH2 tank flight pressurization limits.

The FCVs are “Commanded ON/OFF by corresponding ullage pressure signal conditioner. ON (low flow) when ET ullage pressure exceeds 33.2 psia. OFF (hi flow) when pressure drops below 32.8 psia,” notes the failure summary presentation – available for download on L2.

When the FCVs are commanded “ON,” a Solenoid valve with a “spring return” is energized, causing the poppet on the FCV to close against the spring.

Conversely, when the FCVs are commanded “OFF,” the Solenoid valve is de-energized, causing the poppet to open.

Given the important nature of the GH2 FCVs in maintaining ET LH2 tank pressure during the powered phase of ascent, the primary concerns for a liberation and multiple FCV failures are the over-pressurization of the Liquid Hydrogen tank (resulting in “overboard venting” and the creation of a fire hazard) and Liquid Hydrogen tank under-pressurization (resulting in “External Tank structural failure or low SSME turbo pump Net Positive Suction Pressure”).

Further implications for a liberated FCV poppet head are “downstream component/line damage or blockage and/or line rupture” resulting in the under-pressurization of the External Tank and corresponding venting and fire hazards in the aft fuselage of the Orbiter.

Review of Accepted Flight Rationale for STS-119 and Subsequent Flights:

In particular, the review of all FCV information revealed that the overall likelihood of a FCV poppet failure in flight is low – especially since all FCVs post-STS-126 are inspected via Non Destructive Evaluation (NDE) eddy current inspections.

Furthermore, the extensive flight history behind the FCVs allowed engineers to conclude that any non-detected cracks (after eddy current inspections) in a FCV poppet were unlikely to grow to the point of failure (liberation) in a single ascent.

This flight history, combined with fractography and fracture analysis “suggests that small cracks would likely require some number of flights to grow to failure due to HCF (High Cycle Fatigue) and H2 (Hydrogen) assisted static loading environment,” notes the failure summary analysis.

Still, the possibility – though extremely low – exists that a resonance between the vehicle and the FCV poppet could exacerbate a non-detected crack and accelerate poppet failure in a single flight.

Should a non-detected crack in a FCV poppet lead to a single-flight failure, experts believe that – at most – only 125-degrees of the circumference of the poppet would liberate.

“Bounding analysis based on engineering judgment of fracture experts predicts a maximum particle release of 125 degrees.”

Nonetheless, part of the failure analysis looked at the various possible failure modes.

“ET venting analysis shows no ET venting for a single poppet failure (up to 170 degrees of the circumference) even if that failure occurs as early as engine start. Venting prior to 120 seconds requires two 125 degree poppet failures in the first 90 seconds” of flight.

Additional confidence was gained via liberation impact testing which showed that, even if the largest possible circumferential area of a GH2 FCV poppet should liberate during ascent, the damage inflicted to the connected GH2 lines would not be large or significant enough to cause an ET under-pressurization event.

“ET under-pressurization analysis shows that the hole size in MPS/ET GH2 line required to underpress the tank is 60 times larger than the biggest damage created during impact testing,” notes the failure analysis report.

Furthermore, the amount of damage necessary to cause the over-pressurization of the ET is eight times (8x) larger than the damage created during the largest possible circumferential area liberation tests.

Moreover, “Orbiter flammability analysis indicates that damage created during impact testing is comparable to that required to exceed concentration limits. (Combustion requires oxygen source and ignition source to also exist).”

Lastly, a Monte Carlo probabilistic risk assessment confirmed the low risk of damage due to a GH2 FCV poppet liberation.

Considerations and Testing:

The initial results of the FCV analysis lead to the use of eddy current inspections to verify the integrity of all FCVs for STS-119.

Since then, every flight has had its FCVs inspected both pre-flight and post-flight, with some FCVs being removed from service due to the signatures returned during their eddy current inspections.

In some cases, the NDEs of the FCVs revealed an increase in the signature denoting the presense of unseen, subsurface cracks – cracks that could propagate during liftoff.

However, in a December 2009 interview with NASASpaceFlight.com, KSC Launch Integration Manager Mike Moses stated that the ongoing investigation into the FCV issue revealed that these NDE inspections and ground testing methods could be contributing to the cracks and increases in post-flight eddy current signatures.

“One of the things the teams are looking at is that the Non Destructive Evaluations might actually be causing some of the problems we’re trying to avoid,” stated Moses. “The teams are off looking at that data and there’s still some work to do there but it appears that our ground testing might actually be causing some of the cracks that can propagate during flight.”

This issue also gained mention in the FCV failure summary.

During ground testing, six un-flown FCVs experienced cracking of their poppets. “Hardware evidence indicates that the ground flow environment induces considerable damage to the poppet radius as shown by the cracked six 0-flight poppets.”

Since a very high alternating stress (54 ksi) is required to initiate a crack in a GH2 FCV poppet (those same stresses would accelerate crack growth in a GH2 environment), the most likely cause of the cracks has been traced to either the ground GN2 (Gaseous Nitrogen) processing or the ground GH2 testing environments.

Testing “points to GN2 processing as the likely source of initiation or a ground GH2 testing environment with higher amplitude responses than those in flight,” notes the failure analysis presentation.

A combination of a Computational Fluid Dynamics (CFD) acoustic model and the “intersection of structural modes, and their presence in the acoustic emission flow test data provides two areas of interest for damage consideration even though the state-of-the-art analyses conducted to date do not predict initiation.”

The first of these areas of interest is the GH2 flight and test environment and the second is the GN2 “full stroke force balance testing at Vacco.

For the GN2 full stroke test environment, “The flared 0361 housing at VACCO increases CFD response by a factor of about 3 to that of a straight housing. The full stroke case traverses a structural mode between 56 and 68 Khz as it seats on the housing.

“Chatter: repeatedly seating and unseating the poppet could have an amplification characteristic/flutter that is not captured in the CFD and dynamic analysis. Inlet conditions and stroke variability may influence responses considerably,” notes the presentation.

Additionally, a GN2 85% full stroke case was found to hold the potential of amplifying stresses on the FCV poppet based on Acoustic Environment data that showed an unexpected “non-symmetric” response “in the pull back-in phase of the flow balance GN2 test.”

This signature could be a sign of a “lock in with a mode and or a flutter response.”

Furthermore, “damping” has a significant effect on the alternating stress amplitude at structural resonance; however, this factor is highly uncertain given the lack of measurements of structural damping in operating conditions.

Results and Recommendations:

In all, the year-long investigation has yielded six recommendations to the Space Shuttle Program, the first of which being an official closure to the investigation with “ground flow induced damage as the most likely source of crack initiation.”

The second recommendation advises the continued use of flight rationale based on NDE inspections and hardware observations (eddy current, Mat Lab review, MPI, and SEM). This was followed by the recommendation to maintain “evaluation of the vast acoustic emission data that has yet to be analyzed.”

The fourth recommendation pertained specifically to STS-130 and advised for the “emphasized attention” to Endeavour’s LV-57 position FCV. “This particular position is the only one of the 1301 family of poppets to exhibit considerable crack growth consecutively (STS-126 failure, and STS-127 zone 3 crack development to .22 inch flaw).”

If this trend continues with STS-130, it is recommended that all housing/valve hardware be replaced.

The final two recommendations pertain to the ground processing side of the FCVs.

Recommendation #5 advocates the implementation of a redesign of the outlet tube housing for the GH2 and GN2 ground testing modes. This would be accomplished in order to remove numerous acoustic frequencies to the noise level and demonstrate the effectiveness of Acoustic Environment sensors.

The final recommendation is to remove or reduce the full stroke shimmed flow balance test, and/or implement effective GH2 and GN2 ground testing controls to “improve repeatability and reduce runtimes.”

In addition, new procurements of poppets and piston seals is currently being worked to support additional 0-flight poppet testing.

Further, all FCVs will continue to be removed after every flight, inspected, cleaned, reassembled, and – if they pass inspection – reinstalled on an orbiter for a future flight.

Therefore, engineers have concluded that most likely cause for the FCV liberation on STS-126 was the result of a constant pressure crack growth with subsequent ground test data from flown and un-flown FCVs revealing that the ground testing procedures are the most likely cause of poppet crack formation.

Because of all the extensive testing, strong Flight Rationale exists for the remaining five Space Shuttle missions, with safety measures in place to ensure that only viable FCVs are flown on those remaining missions.

As Mike Moses stated, “When you go back and look at everything that the teams have done in response to this issue, you can see that the appropriate steps were taken to ensure the highest level of safety. This is a complex vehicle and you can never allow yourself to think that you understand exactly how it works.

“We’ve been flying for almost 30-years now and we learn something new every flight. We thought we had a pretty good handle on the Flow Control Valves. STS-126 proved to us that we needed to take some time, go look at our data, re-evaluate our knowledge of this system, and prove to ourselves that we were – and that we are – safe to fly,” stated Moses.

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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STS-125 Swine Flu plan:

At present, managers are only pre-empting a potential outbreak of Swine Flu in the Houston area, by creating a plan that would see the STS-125 astronauts being placed into quarantine as early as this weekend.

“Due to concern with the Swine Flu, the crew doctors are considering putting the crew into quarantine early,” noted the Flight Crew/Astronaut Office via the latest Shuttle Stand-up/Integration report on L2.

“They are going to talk about it this week, especially if they see any outbreaks in the Houston area. They will talk to MOD (Mission Operations Directive) about any impacts to training. If (quarantine) happens, it will probably be this weekend.”

From a SSP (Space Shuttle Program) standpoint, no restrictions have been placed on the travel plans for managers and engineers, a large number of whom have travelled to Florida for Thursday’s STS-125 Agency FRR (Flight Readiness Review) at the Kennedy Space Center.

“Regarding the flu, and the concerns that have been in the news, we do have a lot of folks planning to travel this week and there are things going on around the Program,” added Mission Management Team (MMT) chair Leroy Cain on the Stand-up report.

“As a Program, we do have plans in place for these kinds of eventualities, so if you have concerns about travelling please let us know. We don’t see any reason at this point why we should keep folks back from travelling, but if you feel otherwise or if you think there is something going on that we should be aware of please don’t hesitate to let us know.

“We just need to pay very close attention to it and listen to the health officials, and make sure that we are all being smart about what we do. But right now, it looks like we are okay to travel.”

STS-125 Processing Latest:

Processing remains on track – pending the resolution of two issues (noted below) – with the highlight of the pad flow on Tuesday being the installation of the three Flow Control Valves (FCVs) on Atlantis.

The valves were installed into their housing during Tuesday, with mass spec leak checks already passed. Engineers are now working the electrical retest procedure.

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

“HST SM-4 Interface Verification Test (S07125) is scheduled to complete Thursday,” added processing information on L2, outlining other work being conducted on the pad flow. “S1287 Orbiter Aft Closeouts continue throughout the week and conclude with the Aft Confidence test, planned for Monday, May 4.

“The EMUs (EVA Mobility Units) were installed; testing begins Tuesday. GO2 check valve R&R (GO2 battery) in work after leak in check valve was noted. LO2 tank replenishment with two waves of tankers was completed Monday.

“Final Ordnance installation (S5009) begins Thursday evening. Launch Countdown preparations (S0007.100) will begin Friday.”

Radiator Repair Latest:

Following the incident involving an impact on Atlantis’ left radiator panel from a torque wrench socket – which caused two dents in the face sheet in the 0.011” thick aluminium face sheet and subsequent observation of a crack - engineers have been working on a repair plan.

While that plan is now set, it appears there are two cracks on the radiator, both of which will undergo the same repair procedure.

“After a discussion with the engineering community, approved a plan to perform the standard repair at the pad which is complete removal of the damaged area, install a plug and doubler,” according to engineering notes on L2. “The Hubble M&P engineer and the Vehicle manager were both consulted and approved the plan.

The plan is to remove the face sheet, followed by work on the honeycomb core – which will be straightened. If this is not possible the core will be removed and a honeycomb plug will be bonded in place.

The surface will then be prepared for the bonding of a double face sheet. This will require six hours of elevated temperatures via heated blankets over the area to cure the repair. The entire procedure will be carefully controlled to avoid contamination of the critical Hubble payload components.

“Two plugs will be made one 1 3/8” in diameter and the other 1” in diameter. The doubler will go over both plugs. The paper should be written and approved by Wednesday and the work should start by Thursday,” continued engineering notes.

“Because of the Hubble payload, a catch bag and vacuum will be used to clean as the work is done and cleanliness will be a special concern. The repair should be done by payload bay closure on May 8th.”

A second crack was observed via additional photography – acquired by L2 – that was taken at the pad this week. Both cracks are less than an inch in length.

Despite the second crack being found, the plan remains intact to support the May 8 target for Payload Bay Door closure, which in turn will not impact the launch date target of May 11.

FRCS Stud Investigation:

Also noted by OPO engineers last week – and reported by this site – a concern was raised on the incorrect installation of studs – one of which was broken – relating to the FRCS F5R thruster, found during post STS-119 processing.

“On OV-103 (Discovery), during R&R of the F5 hard on the HMF (Hypergolic Maintenance Facility), one of the studs used to hold the jet in place was broken and the net was missing,” noted OPO (L2). “The team is now searching to determine what happened to the stud/net. Root Cause Analysis is underway to understand this issue.”

That investigation has resulted in a call to check the identical hardware on both Atlantis and Endeavour, which will involve two panels being removed from each orbiter, prior to a borescope inspection of the thruster studs for any problems.

It is unlikely engineers will find any issues on Atlantis and Endeavour, and given Discovery probably flew a couple of missions with the incorrect configuration of the stud – without a problem during flight – it would take a serious problem with the hardware to result in work being called on replacing the studs.

Should managers decide to take that option of replacing the studs, both Atlantis and Endeavour would have to be rolled back for destacking, prior to the completion of remedial work in their respective Orbiter Processing Facilities (OPFs). This, as stated, is unlikely.

Borescope inspections on Atlantis will begin on Thursday.

UPDATE: Inspections on Atlantis have found no issues with the studs – and thus is cleared for flight.

With the Agency FRR meeting on Thursday, the official setting of the launch date will be undertaken. At present no constraints to confirming the realigned May 11 launch date have been noted.

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

No related posts.

STS-125 Pad Flow Latest:

The Hubble servicing payload has been successfully installed into Atlantis’ Payload Bay and is currently undergoing battery charging, as the pad flow remains on track for either a May 11, or May 12 launch date.

“S0600 vertical payload operations: Payload installation into Orbiter was completed on Wednesday,” noted Thursday morning processing information on L2. “Payload battery connector mates complete, battery charging in work. Orbiter Mid-body Umbilical Unit (OMBUU) mate is scheduled for today.”

As reported by this site on Tuesday, managers are attempting to move the launch date to May 11 in order to allow for three launch attempts, prior to handing over the range to the next Delta IV launch. The latest status noted the possibility of moving up the launch date is promising, with only a few “boxes to tick” until it could become official.

Launching earlier is also desirable, due to the short turnaround time ahead of Endeavour’s STS-127′s planned launch the following month.

However, a smooth pad flow between now and launch is required, with tTwo issues currently being worked by engineering teams, relating to the Camera/Flash system located in Atlantis’ ET Umbilical Well and damage to her left radiator panel – as noted on Thursday morning processing information on L2, along with hi res images.

“A 1 1/8” socket from a torque wrench fell from the PCR (Payload Checkout Room) level 4, impacting the Orbiter Port Aft Radiator,” noted the processing update.

“The impact point is approximately 5.5 inches forward of the trailing edge of the aft port radiator and approximately two inches out from the inboard edge of the radiator.”

An investigation into both the incident and the damage is taking place. Such accidents are possible when the tether – which stops the socket from falling any great distance - fails

Importantly, the impact managed to avoid one of the Freon loop lines which run through the radiator panels and allow for heat to be dispersed from the orbiter whilst on orbit. It also managed to miss the newly installed HST payload.

“Inspections have revealed the impact point was in between two Freon lines striking honeycomb material and causing no damage to the Freon lines,” added engineering notes on Thursday. “ The payload was not impacted in this incident. Engineering inspections and evaluation continue. Constraint is to vehicle power up.”

It is possible that no repair will be called for until Atlantis returns home to her Orbiter Processing Facility (OPF) after the completion of STS-125. Had the impact occurred on one of the Freon loop lines, repairs would have been required – likely leading to a delay in the launch date.

See also: Endeavour: MMOD hit to radiator
See also: Atlantis: MMOD hit originated from another vehicle

FCV Latest:

One of the other milestones in STS-125′s pad flow relates to the installation of Atlantis FCVs, which have been “cherry picked” for this flight as part of the short term mitigation plan for avoiding pieces of the valve’s poppet lips from liberating – as observed during STS-126.

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

Because one of the threats to a liberating piece of FCV is the potential puncturing of line at the 90 degree elbow bend - which is located immediately downstream of the valves - engineers have been working on a doubler plate, which would be installed to add protection to the line.

That plan is now likely to be initiated for future flights, but not for STS-125 or STS-127 – which some engineers favored – after it was decided to defer the installation until at least STS-128 with Discovery.

“The FCV manifold elbow doubler discussion was discussed and the decision was made to not pursue that for STS-125 and STS-127,” noted engineering logs on Thursday morning.

The installation of the FCVs is set for completion by the end of the month, which is well within the requirement for advancing the launch date to May 11.

STS-400/127 Pad Flow Latest:

Over on Pad 39B, Endeavour continues to be processed without issue, as she is prepared for her STS-400 Launch On Need (LON) support role for Atlantis’ STS-125 mission. Following the standdown, Endeavour will be moved to Pad 39A for her primary STS-127 mission.

“Engine and aero surface flight readiness testing (V1046), Ball Seal leak checks, and helium signature tests continue through tomorrow,” noted Thursday morning processing information on L2.

“Preparations for Prelaunch Propellant Servicing (S0024) began yesterday and continue into Saturday. Propellant load picks up on Monday with Call to Stations at 2200 EDT. OMBUU mate is scheduled for tomorrow. Crew compartment hatch functional was completed yesterday.”

“Launch Countdown Simulation (S0044) was successfully completed yesterday.”

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. Hubble switchover efforts to Side B completed – Suffers more problemsThe complicated task of remotely switching the Hubble Space Telescope...
2. Dual flow ballet for Endeavour and Atlantis – De-stack debatePreliminary milestone schedules have been created for the complex dual...
3. STS-126 launch countdown begins – Atlantis heads back to OPF-1The three day launch countdown for STS-126 has begun, marking...

Processing Flow Latest:

With two vehicles out at the launch pads, engineers are primarily working towards launching Atlantis from Pad 39A on STS-125, while processing Endeavour to a standby point on Pad 39B, in case of a LON (Launch On Need) requirement – an unlikely event where Atlantis suffers serious damage on orbit and requires rescue.

“S0600 vertical payload operations: Payload Bay doors were opened at 1032 EDT,” noted processing information on Tuesday via L2. “Power up was completed at 0224 EDT. Cap stow complete and rain gutter removal in work at 0430 EDT.

“APU re-pressurization is complete to date with 24 and 48 hour leak checks in progress. LH2 storage tank replenishment is scheduled for today. Two waves of tankers are expected.”

Atlantis’ pad flow remains on target, allowing managers to consider an advancement of the launch date to May 11. Evaluations are in the early stage of planning, with engineers being consulted on their confidence on achieving the advancement.

The plan is related to the Delta IV/GOES launch – which is also scheduled for STS-125′s current launch date of May 12 following recent delays. Due to range requirements, it is understood the plan would be to delay the Delta IV launch enough to allow Atlantis three launch attempts – starting May 11.

Opening requests for flow status were sent to the KSC teams during the SSP FRR, which has completed its two day review of the mission. 32 presentations from the SSP FRR are available on L2, multiple articles will follow ahead of launch.

ET Camera/Flash System Troubleshooting:

The main issue being worked at the pad relates to the ET umbilical well camera and flash system on the belly of the orbiter – which is used to take photography of the separated External Tank after MECO (Main Engine Cut Off).

This allows for imagery to be downloaded on the ground, and used to pinpoint foam loss – some of which may have impacted the orbiter during the ride uphill – in order to cross reference any debris relates issues during the DAT (Damage Assessment Team) process.

The problem with the camera/flash system has occurred on a few recent flights, including STS-119, when the flash only worked the one time, while the resulting imagery could not be downloaded as planned.

“The digital umbilical camera used on STS-119/15A was x-rayed and it showed a blown five-amp fuse. An electrical overload caused the failure,” added processing information on the issue, which appears to be fleet-wide, given smaller issues with also noted on system during Endeavour’s processing for STS-127/400.

“Special topic discussion at FRR – for reasons why it is safe to fly this camera – will be brought forward. Issues with the camera already on STS-125 are being studied for common causes.”

The issue with Atlantis’ system relates to a communication issue – as seen with one of STS-119′s problems with the downloading of imagery – which was initially put through a troubleshooting process by changing the software, which failed.

“ET camera communication problem. Update: A new laptop software load did not make a difference during troubleshooting,” added processing information. “The original communication issue remains unresolved. More troubleshooting to follow. JSC engineering is consulting.

“The camera ‘manual bracket’ setting could not be confirmed. Engineering is looking at a possible internal failure of the camera.”

By late on Tuesday, engineers decided that the camera system will have to be removed from the orbiter for a closer inspection. However, that process is reasonably complicated.

The system has to be removed through ET door cavity, so engineers will have to pull the ET umbilical baggie back by removing the retainer brackets, or slit the baggie and tape it up afterwards.

“Such a procedure has been carried out in the past, but there are concerns about the baggie kapton plastic being thicker where the tape is applied and if that would damage tiles as the baggie rips away,” noted one engineer explaining the process. “This issue is being worked, but the forward plan is to replace the camera.”

The Orbiter Project Office (OPO) at JSC also provided an update on the status of troubleshooting late on Tuesday, which confirmed that the flash on the system is working as required, which means it is not suffering from a full system failure.

“Performed operation to verify function/non-function of the camera by stationing an observer to watch for flashes during the picture acquisition period. A total of 23 flashes were observed. This proves the camera is capable of taking pictures,” noted information acquired by L2.

“The camera team will review the results of this test, as well as a functional test of the GSE (Ground Support Equipment) on the other (Endeavour’s) camera and make a determination as to the next course of troubleshooting at ET sep telecon on Wednesday.”

It is not currently known if this issue is a constraint to launch, especially with elements of the camera system – such as being able to take images – working as required.

Meanwhile, good news has been reported on processing information in relation to the shipping of Atlantis’ Flow Control Valves (FCVs), which are on a deadline of the end of the month for installation into the orbiter.

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

“Status of GH2 Flow Control Valves for STS-125. All three FCVs are scheduled to be on site 4/28. Installation is planned for 4/29, and retest on 4/30.”

Discussions are still taking place on whether a modification – which involves the installation of a protective bracket on the outside of the 90 degree bend, immediately downstream of the valves – will be requested for STS-125. More will follow on this story in an upcoming FCV forward plan article later this week.

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

Related posts:

1. Atlantis to rollback to VAB on October 20 – Hubble troubleshooting latestAs NASA and the SSP (Space Shuttle Program) refine their...

Highlighting the ever-fluctuating nature of the Space Shuttle Program (SSP), STS-129 was originally scheduled to fly with Discovery; however, delays to the Hubble Space Telescope servicing mission forced NASA to realign its downstream flight manifest – resulting in an orbiter swap from Discovery to Atlantis.

With the change of orbiters, as well as changes to the mission’s middeck payload, flight planners are now projecting an Ascent Performance Margin of 1,101-lbs for STS-129 based on a November 12 launch.

Furthermore, the 106 page LSFR presentation – available for download on L2 - shows that Atlantis will not exceed any weight limits for the nominal abort modes available to her Flight Crew in the event of an emergency during launch.

However, Atlantis’ weight will exceed the Contingency Return weight limit set forth by the SSP.

“CONT RTRN exceeds 233,000-lbs Nominal End Of Mission limit,” notes the LSFR presentation.

This, however, does not appear to be of great concern to the SSP as there is no further mention of this issue in the LSFR presentation.

Currently targeting launch No Earlier Than November 12, 2009, the STS-129 mission will see Atlantis deliver the Express Logistics Carriers 1 & 2 (ELC-1 and ELC -2), along with SASA and MISSE (Materials on International Space Station Experiment) 7A and 7B, to the Space Station.

Additionally, the all-powerful Program Requirements Control Board (PRCB) has filed a Change Request to add RAMBO-2 (a Department of Defense payload of opportunity) to the mission. The addition of this payload is scheduled to be discussed on April 27.

Modifications for Atlantis:

As with every OPF (Orbiter Processing Facility) flow, Atlantis will undergo a series of configuration changes/upgrades during her scheduled 127 day stay in the OPF.

The first such modification scheduled for Atlantis is the redesign of the gaseous hydrogen Flow Control Valve (FCV) elbow – a modification necessary to provide additional protection for Atlantis in the event of a FCV liberation and impact event in the gaseous hydrogen lines.

“Proposed redesign of the FCV elbows involves increased wall thickness, a change in material from CRES 304L to 21-6-9 steel, and a longer elbow arm eliminating a tube section and braze joint downstream of each elbow,” notes the presentation.

The redesign will be installed in all six downstream gaseous hydrogen line locations. Further, while this safety modification will result in a marginal weight increase for Atlantis, the alteration of the FCV elbows will not require “vibration testing.” Rather, the modification will be certified for flight by analysis.

More will follow in an upcoming article based on the FCV forward plan presentation, which was reviewed by last Thursday’s PRCB, relating to missions STS-125 and beyond.

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

The second issue, first discovered during Atlantis’ flow for the STS-115 mission back in 2006, relates to an Extended Capture Latch duct clamp and cushion installation discrepancy in avionics bays one and two.

Because of limited access to the area in question, program engineers analyzed the situation back in 2006 and determined that the affected system would continue to function properly.

As a result, the SSP accepted the condition and deferred replacement of the duct clamp and cushion until Atlantis’ next Orbiter Modification Down Period (OMDP).

Since Atlantis was originally scheduled to retire after STS-125, the duct clamp and cushion issue would not need to be dealt with as Atlantis would retire before her next OMDP.

However, NASA managers later decided to retain Atlantis for service to the Shuttle program through 2010, thus giving Atlantis two additional flights and bringing this issue back to the table for discussion.

Again, since access to avionics bays one and two is limited, requiring the removal of the Tactical Air and Navigation and Microwave Scanning Beam Landing System decoder for proper access, the SSP will likely accept an additional waiver for this condition, deferring modifications until “the next time access is obtained.”

Also, additional upgrades to Atlantis will include the installation of a resized orifice to middeck avionics bay 3A, the modification of wiring for the oxygen crossover valves, a change to the external airlock ducting configuration, the removal of a recorder box from the left OMS Pod, and the addition of acreage doublers to avionics bays four, five, and six.

For the middeck avionics bay airflow reconfiguration, the ISS payload Mice Drawer System, which will be installed in middeck avionics bay 3A will not have sufficient airflow to “to accommodate rear breathing payload in the middeck avionics bay 3A,” notes the LSFR presentation.

The intended modifications (installing a bracket in the duct to allow the installation of an upgraded orifice) will increase the airflow and provide avionics cooling support for the Mice Drawer System.

In addition to this modification, Atlantis airlock fan will be configured to run from “post-insertion through de-orbit preparation.”

The LSFR notes that the Mission Operations Directorate has determined that Atlantis’ future missions will not need to benefit from the cryo savings associated with the “use of the booster fan bypass duct.”

The new duct modification will reduce the amount of crew work associated with the fan in its current configuration; nevertheless, the option to fly the booster fan bypass duct will still be available to the STS-129 crew.

On another front, the addition of acreage doublers to Avionics Bays four, five, and six is a preventative measure to reduce the risk of ground processing damage to the avionics bay doors.

The LSFR presentation notes that “Protective doublers over the entire acreage will prevent future damage and work stoppage during damage assessment and repair effort.””

Furthermore, work will also be conducted on Atlantis’ Rudder Speed Brake (RSB) inconel thermal barrier tabs.

The tabs, which are designed to prevent ascent heating from adversely affecting the RSB assembly and which are not necessary for reentry protection, have a history of coming lose during missions. The most notable example was seen during the STS-124 flight last June when one of these tabs dislodged during the standard Flight Control Surface and RCS hotfire tests the day before landing.

Improved ground inspection techniques were added for the STS-126 mission in November. However, despite these efforts, seven tabs were found to be missing when Endeavour returned to KSC.

For STS-129, the redesigned inconel thermal barrier tabs will improve the strength of the tab’s attachment to the inside of the RSB. “The redesign effort will reduce the moment arm and stress to the spot welds and will provide a secondary mechanical attachment,” notes the presentation.

Moreover, “Redesign lengthens tab to reach screw, slides tab into spring by .70” (.30” overhang), includes more spot welds and changes the spot weld from Class “C” to Class “B” (additional quality control to ensure weld conformance).”

Additionally, ground technicians will also be charged with conducting a mandatory structural inspection of Atlantis’ Wing Leading Edge (WLE) spars.

These inspections, which would normally be conducted during an OMDP or a prolonged OPF flow, are due for Atlantis by January 22, 2010. Since this date is before the final manifested mission of Atlantis – and since the last complete inspection was back in 2003 – Program managers developed three working options for this issue.

The first solution was to simply extend the time between inspections, therefore negating the necessity to conduct the intrusive inspections (which requires the removal of several RCC panels) during the 129 flow.

Nevertheless, the SSP decided that it could not accept any justification for not performing at least some of the inspection.

To this end, Atlantis’ engineers will perform WLE spar inspections of RCC panels 9-16 on each wing during the STS-129 OPF flow. The Program is expected to accept the risk of a partial inspection during a PRCB meeting April 24.

Furthermore, one final modification for Atlantis relates to her Shuttle Remote Manipulator System (SRMS) – or robot arm.

Due to a back-up release stall problem on STS-103 in December 1999 – and the fact that raybestos brakes/clutches are no longer available – the shuttle fleet’s SRMS End Effectors are being upgraded with ceramic material brakes.

Endeavour’s SRMS End Effector was upgraded last summer before her STS-126 flight; Discovery’s SRMS End Effector is being upgraded for her STS-128 mission in August.

Atlantis is scheduled to have her SRMS End Effector upgraded during the STS-129 flow; however, delivery of the new End Effector is currently two days behind the KSC need date. The presentation notes that the Government Flown Equipment team is working with the KSC team to refine the delivery dates at this time.

As always, refinements to Atlantis’ flow for STS-129 will be made over the coming weeks and months after the vehicle returns from the Hubble Telescope servicing 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.

No related posts.

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.

Atlantis/STS-125 Rollout:

Atlantis, mated with ET-130 and her twin Solid Rocket Boosters (SRBs), began rolling out on top of the Mobile Launch Platform (MLP) and Crawler Transporter (CT) for the seven hour journey to the pad.

“A5214, rollout of STS-125 to Pad A, call-to-stations was completed at 0001L this morning. MLP first motion occurred at 0354L,” noted Tuesday morning processing information on L2. “MLP hard-down at the pad is targeted for 1100L.

“S0009, Launch Pad Validation: Call-to-stations is scheduled for 1030L this morning. All 3 APUs will be hot-fired on 3rd shift tonight. RSS rotation to mate position is scheduled for 0900L Wednesday.”

Atlantis will be joined by her younger sister Endeavour, when she rolls out to Pad 39B – following the approval to opt for the dual pad scenario for STS-400 LON (Launch On Need support.

Due to a “mission duration change” being worked by the SSP (Space Shuttle Program) for her primary STS-127 mission, Endeavour’s rollout date in April is undergoing fine-tuning. However, both vehicles remain on the flow timeline to support the May 12 NET (No Earlier Than) target for Atlantis’ final servicing mission to the HST.

“A mission-duration change will be brought forward for STS-127/2JA,” noted the latest Shuttle Stand-Up/Integration report on L2. “There are several sidewall payloads and a DTO (Detailed Test Objective) that have been worked and will meet the “early rollout date” on OV-105 (Endeavour).”

Flow Control Valve Status:

It was Endeavour’s previous flight on STS-126 that raised the questions surrounding the three LH2(G) Flow Control Valves (FCVs), following the liberation of a small part of the valve’s poppet during ascent.

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

The liberation failed to cause any issues for Endeavour, notably via the other two valve’s ability to keep the LH2 tank at the required pressure, and no damage was suffered to the internal plumbing of the Main Propulsion System (MPS) from the liberation – which is the main concern surrounding the FCV’s during ascent.

For STS-119, Discovery was fitted with three “cherry picked” valves, which have previously flown multiple times. These valves exhibited no signs of cracking, which is understood to be the first sign of a potential liberation threat on a future ascent.

All three of Discovery’s FCVs worked nominal during ascent, earning deserved praise for the multi-center effort utilized to create the Flight Rationale for STS-119.

Engineers are now looking ahead to the next two flights with Atlantis and Endeavour, in order to guarantee both orbiters have a good set of valves, to “ensure we have the right plan in place to get our assets for STS-125, STS-125(400) LON, and STS-127,” as per the Orbiter Project Office status on the FCVs on L2.

“Will also talk forward plan and make sure there is a good long-term plan to finish out the program.”

At present, Atlantis and Endeavour will require their replacement valves by the start of May, before a long term plan – surrounding newly produced valves at the contractor Vacco – kicks in. For the upcoming missions, previously flown valves have been “cherry picked”, including the re-use of Discovery’s three good FCVs from STS-119.

“Issue: Due to STS-126 GH2 Flow Control Valves (FCV) failure, Orbiter team reviewing options to support near-term requirements. Limited spares with no cracks and rapid flight sequence (STS-119 to STS-125 and STS-127),” noted a SSP overview of the current status.

“In the process of restoring new poppet production capability at Vacco, and they turned on to reinitiate their GN2 test stand capability. It will much more efficient to test and build the valves at Vacco.

“STS-125 and STS-125 LON mission need FCVs by approx May 1, 2009. Orbiter Team reviewed options to install unflown poppets as soon as possible. Current schedules projects FCV delivery in late May/early June as full production capability is restored.”

Discovery’s three nominally performing FCVs will be removed from the vehicle and donated to Endeavour, while Atlantis will fly with three valves that have flow between eight and 12 missions each – all with a nominal track record and no signs of cracking on their poppets, confirmed following extensive testing.

“Orbiter Team recommends the following preliminary FCV configurations: STS-125: (number of flights: 8/12/12, (S/N (Serial Numbers) 1007, 1022, 1023),” added the OPO report. “STS-125(400) LON/STS-127: 5/6/13 (S/N 1006, 1015, 1002) – recycle of STS-119 valves.”

One flown valve and another spare are being prepared to support any issues with the six valves that are to be installed on Atlantis and Endeavour, while other unflown/new valves are being targeted for use with Discovery on STS-128.

“Team working to clear S/N 1017 (10 flight valve) and/or deliver single zero flight poppet valve early as usable spare,” added the OPO. “Schedule supports the 5/1 need date for the STS-125 valves. Team still working to determine exact delivery date for STS-125 LON valves.

“Due to STS-119 valve recycle, date for unflown poppets will move to right. Date should support August STS-128 launch.”

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. Forward Plan: STS-126 rolling to Pad 39A in a few weeks – STS-125 back to VABWhile the status of STS-125′s Hubble Servicing Mission remains fluid,...
2. Atlantis to rollback to VAB on October 20 – Hubble troubleshooting latestAs NASA and the SSP (Space Shuttle Program) refine their...
3. STS-126 launch countdown begins – Atlantis heads back to OPF-1The three day launch countdown for STS-126 has begun, marking...

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.

No related posts.

Engineers will replace cable and hardware in the left SRB and re-test the system over the weekend, after the FRR decided flying “as-is” would be unacceptable. Both SRB’s incorporate a range safety system, that includes a battery power source, receiver/decoder, antennas and ordnance.

“An anomaly was observed in the range safety system that could be attributable to the left hand Command Receiver Decoder (CRD),” added notes from the FRR.

“Therefore, the decision was made this morning to R&R the box tonight. Schedule for the retest after the R&R is dependent on when Delta launch occurs (launch scheduled for tonight) but is not expected to affect our launch date.”

Pending a successful re-test, engineers will begin full preparations to enter the launch countdown, known as S0007, on Sunday. Only one other “exception” was noted at the FRR, related to Ground Support Equipment – which will be resolved in time for the L-2 MMT (Mission Management Team) meeting.

“Call-to-stations (CTS) for launch countdown is currently scheduled for 1830 EDT on Sunday for the March 11 launch,” noted Friday processing information on L2.

“S1006 LH2 dew point and conditioning was completed yesterday. Orbiter aft closeouts continue and should finish up tonight.

“GH2 flange bolts were R&R’d yesterday and the bolt thread protrusion is now within specification. S0071 MPS/SSME and OMS/RCS pressurization for flight picks up tonight on 3rd shift and will complete on Sunday.

“Weekend work: S0071 HYPER/MPS pressurization for flight, IPR-0051/52 range safety troubleshooting, and launch countdown preps.”

Sunday will also mark the arrival of Discovery’s seven crewmembers at the Kennedy Space Center (KSC), with an expected arrival time of 3pm local.

The launch window will range from the 11th to the 16th – the latter resulting in a major reduction to the mission content, notably with space only for one EVA.

“KSC’s scrub turnaround plan reflected two consecutive attempts but they are receptive to three consecutive attempts,” added the FRR notes. “ISSP (International Space Station Program) is willing to launch as late as 3/16 (local time) and accept the loss of EVA content.”

The FRR approved the launch with only minor dissent, related to previous reservations regarding the decision not to install a special doubler plate to the 90 degree elbow bend, which is in the direct path of an impact from a liberated piece of FCV.

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

“The Shuttle Program poll to go for launch on 3/11. We are deciding to go without installing the doubler, but there is some dissent from those who would like to install the doubler,” noted one memo ahead of the FRR. “GO” for launch on 3/11, without the doubler, will be the Shuttle Program recommendation to the NASA Agency FRR.”

Confidence is high that none of the reinstalled valves on Discovery are threatening to suffer from a liberation, following an extensive check of the three valves – all of which have previously flown with Discovery four to five times.

The checks were based around signs of cracking, which was observed on some of the inspected stock of FCVs. Consistent test results via an “eddy current screening’ technique proved the ability to ensure the valves were free of cracks, and thus highly unlikely to liberate part of its poppet for at least the next flight – allowing for the single launch flight rationale.

“The FRR went very smoothly today and we have a go decision for a target launch date of 3/11/09, with potential opportunities through 3/16/09 pending range coordination. L-2 is scheduled for Monday at 9am EDT,” added notes from the FRR, acquired by L2.

“The entire community was comfortable with FCV rationale for flight, which is based on:

“1) mitigation of eddy current inspections showing no detectible cracks on installed poppets, 2) bounding analysis showing 125 deg. max particle size, if a poppet should fail, and 3) low likelihood and overall acceptable risk of critical failure consequences after extensive analysis and testing. Any further work to complete gimbal testing and the integrated PRA were deemed unnecessary.

“There were a couple dissenting opinions voiced about not flying a doubler on the elbow downstream of the FCV exit, but the community was uncomfortable with the residual risk of the doubler until final design verifications are complete.

“Although the recent focus has been squarely on FCV, the entire OPO team has done a terrific job getting us ready across the board to fly STS-119.

“A very special thanks to everyone working FCV for all the outstanding work as well as late nights and long weekends, just a remarkable job! Now get some rest this weekend before we go fly.”

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

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