STS-133: Discovery’s replaced SSME heading into key torque checks

by Chris Bergin

With Discovery’s three Space Shuttle Main Engines (SSMEs) now reinstalled on the orbiter, engineers should know by Friday if they have solved the torquing issue with ME-1. The engine – along with ME-2 and ME-3 due to access issues – was removed to allow for the replacement of the Low Pressure Oxidizer Turbo Pump (LPOTP) at the center of the issue.

STS-133 Processing Latest:

Despite her STS-133 launch date slipping, it remains a busy processing flow for Discovery inside her Orbiter Processing Facility (OPF-3), as engineers keep up the pace to protect contingency time.

“Payload premate test was completed on Friday. Auxiliary Power Unit (APU) leak and functional test. WCS (Waste Containment System) functional testing continues,” noted the NASA Test Director (NTD) flow report latest (L2).

“Airlock subsystem verification picked up and continues through Friday. Crew equipment interface test is scheduled for Friday and Saturday.”

The Orbiter Project Office (OPO) at the Johnson Space Center (JSC) noted an actuator issue with the B-Hatch (otherwise known as the side hatch) on last week’s Shuttle Standup/Integration report (L2), which has since been repaired.

“Orbiter (USA/JSC): On OV-103 (Discovery) B-hatch, they were having some problem getting the actuator door closed. It was fixed, but in the process of trouble-shooting the problem, they noticed that one of the four little detent balls that keep the removable handle in place was missing.

“The whole actuator will be R&R’d (Removed and Replaced) to get it back into configuration. The other vehicles will be checked to ensure no other balls are missing.”

STS-133 Specific Articles:

The hatch issue wasn’t elevated into an IPR (Interim Problem Report), meaning Discovery remains on a low count of just 25 IPRs in her flow since returning from STS-131, the latest of which – relating to an false indication on an electrical umbilical in Discovery’s Payload Bay (PLB) – has since been cleared.

“IPR-0025 sill connector issue has been isolated to a problem with ROEU (Remotey Operated Electrical Umbilical System) Sys 1 stow indication due to a recessed pin on a connector. Repair and retest were successful.”

Discovery will welcome back her Right Hand (RH) Orbital Maneuvering System (OMS) Pod next week, following the completion of work replacing the faulty helium isolation valve on the Right Reaction Control System (RRCS).

“At the HMF (Hypergolic Maintenance Facility) on the RH pod, have completed the valve R&R retest. In work on closeouts and structural inspections. The pod comes back to the OPF on July 13,” noted KSC Logistics on the Standup Report, whilst adding the removed faulty valve is now being evaluated for a root cause to the issues during Discovery’s STS-131 pad flow.

“At the NSLD (NASA Shuttle Logistics Depot) at KSC, have the helium ISO (Isolation) valve from RPO-103 (Discovery’s Right Hand Pod) that will start TT&E (Test, Teardown & Evaluation).”

Other processing highlights for Discovery included the completion of work relating to the checks on the small ceramic plugs located along the Payload Bay Door (PLBD) hinge line – an area that can only be access when the orbiter is inside her OPF. Work is also proceeding to schedule on the mated External Tank and twin Solid Rocket Boosters (SRBs).

“OV-103 (STS-133) Completed the PLBD hinge line ceramic plug R&R. Got the PLBDs reopened,” added KSC Integration on the Standup report. “Will continue with TPS processing, have 78 more bonds to complete for a total of 137 for the flow. In the VAB (Vehicle Assembly Building) on the stack, continuing with the integrated closeouts between the tank and the booster.”

Those integrated closeouts include leak checks and foam applications to closeout areas of the stack, with one area of slight damage foam damage still under evaluation. Final pull/plug tests on the intertank region of ET-137 have also been completed, allowing for access scaffolding to be removed.

“SRB BI-144 / RSRM 112 / ET-137 (VAB HB-3): L/R (Left/Right) S&A leak checks; RH is complete. LH leak check is in work. R/L Tunnel Cover foam application; Preps continue. RH RT-455 applications in work, LH Bond check readings are next,” added the NTD.

“L/R Forward Crossover installation complete. RT-455 next. RH ET Fairing cover next. On hold for damaged SLA (Foam) PR (Problem Report – damage on fairing support plate, Photos and measurements taken. More disposition to follow). L/R ET bolt catcher installation complete.

“L/R ET AFT Fairing Installation – Preps for installation continue. Additional foam damage areas were during inspection and require engineering disposition to continue. Inter-tank Adhesion Testing location closeouts are complete and scaffolding is removed.”

Meanwhile, Discovery’s SSMEs head into integrated testing on Wednesday, leading up to torque check results on the LPOTP likely to be known by the end of this week.

“Engine securing continues; SSME/MPS (Main Propulsion System) integrated testing is scheduled for Wednesday,” added the NTD processing report.

Following the Program Requirements Control Board (PRCB) decision to swap the engine positions for two of Discovery’s engines, engineers have completed the reinstallation process, with ME-1 now sporting a replacement turbo pump.

“Following the issues with the low pressure LOX turbo pump, they got all three engines back into the engine shop and replaced the pump,” noted Pratt & Whitney Rocketdyne/KSC on the Standup report. “They went to the PRCB and re-ordered the engine positions, switching engines #1 and #2.

“Engine 2044 was put into position 1, Engine 2058 in position 3, and Engine 2048 with the new low pressure pump into position 2. Into securing and into leak checks.”

The removed LPOTP has since been shipped back to Pratt & Whitney Rocketdyne’s Canoga Park facility in California, where it is undergoing a failure investigation, in order to understand why it suffered from an unacceptably high torque – which is the first time such an issue has occurred since 13 years ago.

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