STS-133: Discovery’s SSMEs removed – ET-137 arrives in Florida

by Chris Bergin

Discovery’s speedy turnaround from STS-131 to STS-133 is continuing on the timeline, as engineers completed the removal of her three Space Shuttle Main Engines (SSMEs) and welcome External Tank (ET-137) to the Kennedy Space Center (KSC). STS-133’s September launch target remains under threat of slipping, due to required modification work on Discovery’s payload.

STS-133 Processing Latest:

Discovery was set to launch on the final scheduled mission of the shuttle program, prior to the large payload-related delay to STS-134. With Discovery now flying after Atlantis, the veteran orbiter is on track to be in a position to support STS-132 via the LON (Launch On Need) requirement.

It’s only been a matter of weeks since Discovery arrived back from STS-131 and began her processing flow inside the Orbiter Processing Facility (OPF-3). Engineers have been ably pressing through the schedule of milestones, which included the successful removal of all three of the orbiter’s SSMEs by the end of the week.

“Space Shuttle Main Engine (SSME) removal: Engine 2 and 3 removals are complete; engine 1 removal completed on Friday,” noted the NASA Test Director (NTD) in processing information on L2. “SSME Thrust Vector Control (TVC) DPF test performed.”

“Mass Memory Unit (MMU) R&R was completed. Forward Reaction Control System (FRCS) functional and checkout.”

Engineers have finally brought Discovery’s Ku-Band capability back on line, following issues during STS-131. The root cause was deemed to be a problem with the Ku-band’s Deployed Assembly (DA), which has now been replaced, with electrical connection mates completed.

The Ku-band system has been checked on Atlantis, although plans are in place for the crew, should a similar issue occur during STS-132.

STS-133 Specific Articles:

Engineers are continuing to work on Discovery throughout the weekend, finishing any outstanding work on her FRCS, while the ceramic inserts on her Payload Bay Door hinge line are being inspected, ensuring they have all remained in place – following the Flight Readiness Review (FRR) interest in the inserts, via their potential to liberate.

“Weekend Work: Forward Reaction Control System (FRCS) functional checkout (contingency),” added the NTD report. “Preparations for Aft Propulsion System (APS) functional checkout. Payload Bay Door (PLBD) inserts inspection/rework. Thermal Protection System Waterproofing Sunday (Bay Clear).”

While the liberation threat from the inserts have focused on the handful of loose and missing plugs around the windows of the orbiter on a couple of recent flights, the problem with accessing the inserts on the PLBD hinge line has resulted in the aforementioned checks being conducted in the OPF.

Engineers are only double checking none of the inserts are showing signs of coming loose, as program confidence has already been earned via flight history showing no liberations from this area – which in turn has allowed for flight rationale to be in place for STS-131 and STS-132.

The biggest challenge facing STS-133 remains the modification of the Multi-Purpose Logistics Module (MPLM) Leonardo, as engineers convert it into a PMM (Permanent Multi-purpose Module), ahead of being left on the International Space Station (ISS) at the conclusion to the docked phase of the mission.

The timeline – to be ready to support the launch date of September 16 – is deemed to be extremely tight, and remains at risk of slipping by a few weeks.

Other payload considerations are also being discussed, mainly based around the problems suffered by the STS-131 delivered NTA (Nitrogen Tank Assembly).

Although the tank is now working as planned, meetings had already taken place to include a LMC (Lightweight Multi-Purpose Experiment Support Structure Carrier) into Discovery’s already “busy”¬†payload bay.

“A CR (Change Request) will go into the system to put the LMC on STS-133 and to increase the mission duration from 8+1 to 10+1. Trades are being discussed,” noted Flight Operations & Integration via the Shuttle Standup Integration report (L2).

However, once the NTA had undergone successful troubleshooting, the decision may now be reversed – confirming the NTA was central to the original call for the inclusion of a LMC.

“Had a CR submitted (which has been pulled back) to add an LMC to STS-133/ULF5 to return the nitrogen tank,” added Flight Operations & Integration on a later Standup report. “This is on hold until ISS can figure out if they want to leave the NTA on board or not.”

A final decision on adding the LMC to Discovery’s payload bay will be taken at the Space Station Program Control Board (SSPCB) meeting on May 18.

“I asked a question about the ULF5 Payload Bay config and whether adding an LMC was still under consideration,” noted one manager on the FPWG notes (L2). “The response was that the NTA problems appear to be resolved and the likelihood to fly and LMC was now reduced since NTA is back operational.

“This topic will be added to the next SSPCB agenda, probably on 5/18. If the LMC were added, two key tasks would be the R&R (Removal and Replacement) of the NTA Tank, and the LWAP (Light Weight Adapter Plate) task.”

Meanwhile, Discovery’s ET has arrived in Florida, ahead of being offloaded on Monday, and transported into the Vehicle Assembly Building’s High Bay 4E for checkouts.

The tank enjoyed a smooth processing flow at the Michoud Assembly Facility (MAF) in New Orleans, who only have ET-138 for STS-134, and ET-122 for STS-335 to ship, if the current manifest remains unchanged.

“ET-137 is now expected on Dock Saturday, May 8th at the VAB Turn Basin around 1630,” pre-empted the NTD on Friday. “Offload to the VAB transfer aisle Monday, May 10th, lift into HB-4E on Tuesday, May 11th.”

The tank will eventually be moved to High Bay 3 for mating with the twin Solid Rocket Boosters (SRBs), which are currently undergoing stacking operations.

“SRB BI-144 / RSRM 112 (VAB HB-3): LH (Left Hand) HDP (Hold Down Post) Stud Tensioning; Tensioners installed, tensioning is ready to work. RH HDP Stud Tensioning; Tensioning complete, tensioners moved to LH, ground check next,” added the NTD report.

“Right Aft Center segment mate is complete. Beam is disconnected and on the dolly. Primer is in cure. Leak check is in work. Left Aft Center segment stacking is scheduled for next Wednesday/Thursday.”

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