Atlantis returns to OPF for STS-129 processing – Endeavour SSME contamination

by Chris Bergin

Atlantis has returned to Orbiter Processing Facility (OPF-1) in preparation for her flow towards the STS-129 mission to the International Space Station (ISS). Marking a busy period for the fleet, Discovery is receiving her SSMEs (Space Shuttle Main Engines) for STS-128, while Endeavour’s SSMEs are being evaluated – after corrosion/contamination was seen on tubing associated with two engine nozzles.

Atlantis/STS-129 Latest:

Following her Californian vacation, Atlantis has returned to the home comforts of the OPF in the early hours of Thursday, ahead of a flow that will reconfigure the orbiter for at least two more ISS missions prior to the retirement of the fleet – pending a final decision on shuttle extension, and her current assignment as the STS-135 LON (Launch On Need) support role of the final mission on the current manifest.

“The Orbiter was lifted and the SCA (Shuttle Carrier Aircraft) backed out yesterday at 1226 EDT. Atlantis was spotted in OPF Bay-1 at 0049 EDT (1st attempt) this morning,” noted Thursday processing information on L2. “Orbiter jack and level is in work. The 50-1/2 door removal and aft access are being worked. Tail cone removal is scheduled for 1st shift today.”

a24Work is taking place on inspecting wiring and avionics electrical hardware related to the Atlantis Aerosurface Servoamplifer (ASA) channel 1 failure, while the small amount of MMOD (Micro-Meteoroid Orbital Debris) related damage to an Orbital Maneuvering System (OMS) pod nozzle has been documented.

Although the MMOD hit was within family, it is large enough to call for the replacement of the nozzle during Atlantis’ processing flow.

Atlantis’ STS-129 mission is currently scheduled as the fifth and final mission of 2009, with a NET (No Earlier Than) launch date target of November 12, delivering 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.

Work has already been taking place for the shuttle elements flying with Atlantis, with the External Tank (ET-133) in a smooth final flow at the Michoud Assembly Facility (MAF), along with the build-up of the RSRM (Reusable Solid Rocket Booster) motors.

“SRM/RSRM (BI-140/ RSRM 108/RPSF): Right Aft Booster Build-up. Aft Tunnel Cable Electrical Check-out is complete. O/I Cable Connect Rooster Tail Aft Feed thru cable connections are in work. O/I Strut Cable Check-Out. Strut cable testing set-up is in work,” added processing information on Thursday.

“NSI Cable Connections and Resistance Checks. Ready-to-Work after Strut Cable check-out. Stiffener Ring Splice Plate Installation. Ready-to-Work after Aft Feed Thru Cable connections are complete. Left Forward Center Segment Offload. Crane repair is complete. Offload Segment today.”

Endeavour/STS-127 Latest:

With the launch date for STS-127 now officially set for June 13, Endeavour is less than a week away from heading into the complex ballet of S0007 (Launch Countdown) procedures out at Pad 39A.

Ahead of that milestone, the STS-127 crew have successfully completed the Terminal Count Demonstration Test (TCDT), ending with the simulated shutdown of the SSMEs at T-4 seconds.

“The Flight Readiness Review concluded yesterday and Saturday, June 13 was officially selected for launch of Endeavour on the STS-127 mission,” noted STS-127 processing latest.

“S0017, Terminal Count Demonstration Test continues today. T-0 is planned for around 1100 EDT this morning. Emergency egress training for the crew (S1025) was completed successfully yesterday. S0009, Launch Pad Validation, is essentially complete.”

However, one issue is being investigated, following the observation of rust-like contamination on two of Endeavour’s SSME nozzles.

a32“Corrosion/contamination has been noted on two SSME nozzles at Pad A for STS-127 (engines 1 and 3). ME2045 has a significant amount in the first few inches downstream of the MCC/nozzle interface joint G15 (see images below), and ME2054 has a minor amount approximately 10 inches below G15,” added a report on the observations.

“Digital microscope photos of the affected areas will be taken prior to and after cleaning with deionized water and a scrub brush. PWR Canoga Park nozzle engineering and M&P folks will evaluate today.

“These nozzles do get a coat of Sodium Molybdate corrosion inhibitor applied to the hotwall after every flight 1 to 8 inches aft of G15 (for some nozzles, including ME2045’s, it is applied 0 to 8 inches aft of G15). No discoloration was noted on these nozzles following the MCC polishing at Pad B on May 8.

“It is not yet known if nozzle leak checks will be required (possible launch schedule impact). We will have a better idea once we evaluate the nozzle post-cleaning imagery.”

The SSME nozzle tubes are made of A286 iron based steel and are nickel plated primarily to make the brazing of the tubes to operate nominally. It is deemed to be completely normal for these tubes to rust in the Florida coastal pad environment. However, the tubes – which are put under 6000 psig pressure during engine operation – are at risk of rupturing if corrosion has reduced their integrity.

An example of tube damage on the SSME nozzles was seen during STS-93’s infamous launch, where three tubes were damaged by a blown injector pin, leading to the engine controller assuming more hydrogen was being burned and compensated by injecting additional LOX – ultimately resulting in the ECO (Engine Cut Off) sensors shutting down the engines slightly ahead of time, leading to an underspeed at MECO (Main Engine Cut Off).

While Columbia’s engine only suffered from three punctures on her SSME during STS-93, a tube split would be a more serious event, which is why the engines will be inspected and cleared by Rocketdyne ahead of launch.

UPDATE: Leak Checks to take place on Friday.

Discovery/STS-128 Latest:

Over in OPF-3, Discovery is continuing to push through her processing flow, with the milestone of SSME installation being completed on Thursday. Discovery is tracking a launch date of August 7 for her STS-128 logistics mission to the ISS.

“FRCS interface verification is complete. SSME 1 and 3 were installed yesterday; SSME 2 installation is planned for today followed by engine securing,” noted STS-128 processing information on Thursday. “OBSS (Orbiter Boom Sensor System) end effector pre-mate and OBSS thermistor interface tests were both successfully completed.

“MSBLS (Microwave Scan Beam Landing System) waveguide leak checks are planned for today. MADS (Modular Auxiliary Data System) interface verification will be worked today. Orbiter Bus redundancy testing will pick up tonight. A hydraulic operation to perform ET actuator cycling and position aero surfaces is scheduled for tomorrow.”

Discovery is being prepared for a 13 day, three EVA, mission that will include the flight of the TriDAR AR&D Sensor Detailed Test Objective (DTO), the next Boundary Layer Transition (BLT) DTO. Also riding uphill with Discovery will be a new crew member for the ISS – Nicole Stott – as well as MISSE (Materials on International Space Station Experiments) 6A and 6B, SIMPLEX, MAUI, and SEITI.

Aiding Discovery’s ride to orbit will be the Solid Rocket Booster BI-139 (Booster Integration) set, which are currently being stacked in High Bay 1 of the Vehicle Assembly Building (VAB), while External Tank ET-132 is being prepared for mating with the boosters.

“SRB/RSRM (BI-139/ RSRM 107/ VAB/ HB-1): Left Forward Center segment mate is complete. Right Forward Center segment delivery to VAB has been delayed due to weather. No estimate for delivery at this time,” added processing information. “ET-132 (VAB HB-2E) 17” Disconnect Measure/Adjust: LH2 complete, boroscope scheduled for today. LO2 side is in work.”

L2 members: Documentation Рfrom which most of the above article has quoted snippets Рis available in full in the related L2 sections, now over 4000 gbs in size

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