STS-134: Endeavour ordnance installation on tap – Mission still being tweaked

by Chris Bergin

Following a relatively relaxed week at Pad 39A, Endeavour is preparing to enter Ordnance installation tasks on Monday and Tuesday, as the youngest orbiter in the fleet heads into her final week prior to the launch countdown. With the Flight Readiness Review (FRR) also set to take place on Tuesday, managers are making their final refinements to the baselined STS-134 mission.

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With the processing flow realigned for the April 29 launch date, over one week’s worth of contingency time has been naturally eroded over recent days via a reduced workload, merging into the planned schedule in order to hit its marks in the run up to the start of S0007 (Launch Countdown) operations in just over a week’s time.

As a result, Endeavour and her engineers enjoyed the weekend off, ahead of what is expected to be a ramped up flow over the coming days.

“The EMU (Space Suits) were stowed in the airlock. The functionals on the units performed. Worked some of the vehicle closeouts,” noted KSC Ground Operations (L2). “Monday night/Tuesday morning, the ordnance activities will be performed. Still on track for launch April 29, 2011.”

Those EMU tasks did result in two additional Interim Problem Reports (IPRs) being charged against Endeavour’s flow, both of which were resolved without delay – allowing the hatch to be closed for the final time ahead of launch day.

“OV-105/SRB BI-145/RSRM 113/ET-122 (Pad-A): V1103 EMU functional testing was successfully completed and the airlock has been closed out for launch,” noted the NASA Test Director (NTD) report (L2). “New IPR 134V-0039: During V1103, following Airlock O2 samples, observed decay on the Extra Vehicular Oxygen Supply Pressure.

“The decay rate was approx 170sccm (70sccm is allowable). Troubleshooting found the dynatube cap at TP1 on Panel C7 was only finger tight. The cap was removed, inspected and reinstalled with proper torque, and a leak check of the O2 system was successful.

“New IPR 134V-0040 to Integration: Following EMU 1 Battery charge termination, EMU 2 Service and Cooling Umbilical (SCU 2) was de-mated instead of SCU 1. Per design, the EMU power supply automatically shuts down when an open circuit is detected, so there was no hardware damage. SCU 2 has been re-mated and battery charging successfully completed.”

A Problem Report (PR) was also listed prior to airlock closeout, relating to a duct in the airlock which was missing some straps and wasn’t installed per nominal procedure. However, by the time the issue was listed, the correct straps were procured and installed, and the duct was properly stowed.

With the stack now officially into S0007 launch countdown preparations, the SRB (Solid Rocket Booster) ESP (External Stowage Platform) has been lowered at the pad. The ESP will be used as part of the final ordnance installation tasks, scheduled to begin on Monday night.

Ordnance installation tasks will be rounding up by the time managers meet for the Agency Level FRR at the Kennedy Space Center (KSC), which will officially set the launch date.

While a large amount of work has already been completed via the Space Shuttle Program (SSP) FRR at the Johnson Space Center (JSC), the Agency level review will also evaluate the work carried out by engineers to ensure the recent severe storms did not cause any damage of concern on the stack via the lightning, hail and wind events.

“Making progress on open paper closures for ET-122 in anticipation of the Agency FRR,” noted Lockheed Martin/External Tank on the latest Shuttle Standup/Integration report (L2). “Also incorporating the package and will have a submittal regarding the hail damage flight rationale.”

The required flight rationale, mainly relating to two specific areas of interest – the slight hail damage to the top of ET-122 and wind loads stresses on the associated hardware with the Ground Umbilical Carrier Plate (GUCP) – was the subject of four large presentations (available on L2), which were overviewed by the Program Requirements Control Board (PRCB) on Thursday.

The highly extensive review, which included the departments which presented a positive overview to the Engineering Review Board (ERB) earlier last week, will be the subject of an upcoming article.

Mission Tweaking:

Also noted of late were the evaluations into the potential Endeavour will carry out a full 16 day nominal mission, which would allow for additional work to take place to aid Atlantis’ shorter – and timeline constrained – STS-135 mission. Currently, STS-134 is being baselined as a 14 day mission, with any extension decision likely to be taken during the docked phase of the flight.

Endeavour sports the additional docked mission capability due to their SSPTS (Station to Shuttle Power Transfer System) – allowing for a reduction on the demands of the orbiter’s PRSD (Power Reactant Storage and Distributation) tank loads, which supply the Fuel Cells.

“Reviewing STS-134 O2 loading; have cryo to protect +2 docked days. APM (Ascent Performance Margin) is sufficient to allow reduced offload and to add cryo for FD4 (docking) protection,” noted Flight Operations & Integration on the Standup report. “That is ~160 lbs more of O2 to put on. That still leaves an APM above 100 lbs for a 5 minute window.”

If a 16 day mission option was taken, this would also have the addition of the End Of Mission (EOM) plus one and two days scenario. Plus one is usually classed as “pick-em day” in this scenario, resulting in numerous landing opportunities at KSC, Dryden (Edwards Air Force Base) and even White Sands in New Mexico if required. EOM+2 would be reserved for a technical wave off, due to the unlikely event of troubleshooting requiring the additional day in space.

As confirmed by Flight Operations & Integration, the option to pack STS-134’s mission is related to the opportunity to release some of the workload from STS-135, as Atlantis’ docked mission timeline continues to be worked due to the previously reported challenges.

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“It (the STS-134 extension) is being assessed for STS-135. STS-135 is a very tight flight, and the team is trying to come up with creative ways to fit it in and still get the mission content done,” added FO&I.

“A CR (Change Request) was approved for Outside the Board Processing yesterday to go to an April 29, 2011 launch date for STS-134. A mission duration of 15+1 days was put on that. There is some discussion of going to 16+0, so there might be a change coming (currently sticking with 14 days for the interim).”

Also requiring late evaluation is Endeavour’s docking procedure, after the Orbiter Project at the Johnson Space Center updated their evaluations into the large oscillations noted during Discovery’s docking with the International Space Station during STS-133.

Large oscillations between Shuttle and ISS on STS-133. Misalignment reached 10 degrees pitch and 4 degrees yaw (in mechanism coordinates). Similar to STS-130, but larger,” listed a point by point overview of the STS-133 issues in the SSP FRR Orbiter Presentation (all FRR presentations available in L2 – numerous).

“Clearance between Orbiter forward bulkhead and PMA-2 reduced to 16.4 inches. Time from initial contact to hooks closed was 50 minutes. Timeline impact. ISS out of certified attitude. ISS power concerns. ISS longeron shadowing. Unable to model combined gravity-gradient and dynamic effects.”

As a result of the evaluations, the Orbiter Project recommended a change to the docking procedure for STS-134, revolving around the “fixers” in the docking hardware.

“Recommending docking procedure update for STS-134. Current procedure pauses on loss of ring alignment. Pause disables fixers and permits vehicles to oscillate,” added the Orbiter FRR presentation.

“Updated procedure pauses on indication of initial contact. Initial contact envelopes fixers. Fixers will control misalignment throughout ring retraction. Total docking time of 15-20 minutes. Consistent with docking system design and certification. Pending two confirmations. Approvals in work.”

The noted approval process involves numerous centers and even the Russians at RSC Energia, with an update to the Standup meeting speaking of another review being scheduled at an upcoming Joint PRCB meeting,

“Working with the community on the change in the docking procedure. The team has performed the analysis and discovered that even with a failed fixer in the new procedure, we cannot get contact between orbiter and station,” noted the Orbiter Project on the Standup report. “This will be briefed at a Special OCCB, and then a JPRCB at a later date.”

The update was also the subject of praise from SSP manager John Shannon, who also referenced the painful layoffs which underwent another round throughout the Shuttle community recently, prior to the major job cull at the conclusion of STS-135.

“It’s really good to see that the team is working things like… docking procedure changes. That is what we have to keep doing here,” noted Mr Shannon on the Standup report.

“We had our last big contractor layoff last week, until the end of the Program. The team is in place to manage the final two missions, and folks know what they need to do to accomplish them successfully. So, we are set up and ready to go for April 29, 2011. We will come back late June/early July and do STS-135 to finish up really well.”

(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: All via L2 content and L2 presentations).

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