Endeavour in eventful flow – OPF and ET-138 investigations continue

by Chris Bergin

The mystery washer that managed to find its way into the LO2/LOX feedline on External Tank ET-138 is being classed as an isolated incident, as the Shuttle fleet work through numerous investigations. Work on Endeavour is back into a full flow, as an investigation board check into how an Air Hoist managed to fall on to a platform in her Orbiter Processing Facility (OPF).

STS-134 Processing Latest:

Endeavour is in a relatively relaxed flow inside OPF-2, as the youngest orbiter in the fleet prepares for a February 24 launch date target for what is likely to be her final trip to the International Space Station (ISS).

No Interim Problem Reports (IPRs) have been charged against her flow for some time, although the installation of the heat shield – which mounts on to the aft of the vehicle to surround the Space Shuttle Main Engines (SSMEs) – was interrupted by an Air Hoist falling on to one of the OPF platforms.

“An Air Hoist fell approx. 8 feet down on to 19-level platform (last week). No personnel injury or flight hardware damage occurred. A Standing Accident Investigation Board (SAIB) has been formed. SSME heat shield installation has been rescheduled,” noted the NASA Test Director (NTD) processing report (L2), before the status was updated.

“The Air Hoist (SAIB) is completing its work. The area is still controlled. Controls are expected to be removed and the air hoist re-installed. SSME heat shield installation is now scheduled to pick up tomorrow (Wednesday).

Other processing, away from the controlled area, had been proceeding without delay, with engineers completed resupplying the Freon Coolant Loop – which runs through the orbiter’s radiators to provide vehicle cooling when the Payload Bay Doors (PLBDs) are opened on orbit.

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“OV-105 (STS-134). Window 7 has been installed for flight. Completed engine leak check and securing,” added NTD processing information. “Freon Coolant Loop top-off was completed. Sampling and adjust are scheduled.”

Waterproofing Endeavour is also being worked, after the process was recently carried out on Atlantis, marking the final few times the associated contractor – Evonik Degussa – will be working on the fleet

“Waterproofing of the vertical and side hatch are planned for Friday. This operation will result in a Bay clear,” added the NTD, following the clearance of OPF-1 for the opening work that was conducted on Atlantis this month.

Having already shutdown their production last month, the Program Requirements Control Board (PRCB) overviewed their ability to support the waterproofing of the orbiters with their stock of Dimethylethoxysilane (DMES) – the waterproofing agent – through to the Launch On Need (LON) support role of Atlantis, and/or if Atlantis gains the currently notional STS-135 mission.

“Tiles and Blankets are re-waterproofed by injection post flight. Approximately 42 one gallon bottles are used per Orbiter per flow. Current manifest shows two flows to the end of the program (STS-134, STS-335/135),” noted the associated PRCB presentations (L2) back in June.

“DMES is used to re-waterproof the Orbiter tiles and blankets prior to every flight. DMES has been in use at KSC since 1988. Only effective waterproofing agent that does not cause RTV reversion. Only material that is qualified for use on the Orbiter thermal protection tiles and blankets. Evonik Degussa plans to shut down the DMES plant and remove equipment once the contract expires on July 21, 2010.

Documentation shows that over 100 bottles of DMES will remain in stock after the final waterproofing is conducted, which should be an ample contingency ratio, taking into account it would take up to three years to find another supplier.

Endeavour’s primary payload, the Alpha Magnetic Spectrometer (AMS) – which was the primary cause of the launch scheduled realignment in April – is expected at the Kennedy Space Center (KSC) in just over a week’s time. Preparations for its eventual installation into Endeavour’s Payload Bay are currently on track.

“The Delta AMS Compatibility Review for STS-134 was held August 6.  It was followed up with a Ground Operations Working Group for AMS last week at KSC,” noted Flight Operations and Integration (Johnson Space Center) on the latest Shuttle Standup/Integration report (L2). “AMS is on track to deliver on August 26.”

“Payload Critical Path testing update: Alpha Magnetic Spectrometer (AMS) Power Transfer Unit (PTU) load test and Remotely Operated Electrical Umbilical (ROEU) 1553 BUS Characterization were rescheduled to this week,” added the NTD report.

Meanwhile, an Engineering Review Board (ERB) is being updated on the ET-138 investigation this week, after engineers removed the LOX 17” cover plate to perform angle and tip load measurements and found a washer had somehow found its way inside.

The washer was sent back to the Michoud Assembly Facility (MAF) in New Orleans, in order to attempt to track down its history, while options remain open to perform X-Rays on both ET-138 and the already-stacked ET-137 – which is set to fly with Discovery on STS-133.

“PR (Problem Report) ET-138 Washer update: Possible course of action will be to take X-rays, including areas inside the intertank, to look for additional FOD (Foreign Object Debris). The decision may also be made to perform X-ray inspections of ET-137,” added the NTD updates.

“The washer investigation is in work. Currently, it appears to be an isolated incident. There is an Engineering Review Board (starting) Tuesday, August 17. They will discuss potential inspections. The team is still working possible scenarios of how the washer got into the pipe.”

Processing of the tank – taking place inside its Checkout Cell in High Bay 2E (HB-2E) inside the Vehicle Assembly Building (VAB) – is continuing to plan for the meantime.

“ET-138 (VAB HB-2E): -Y protuberance air load foaming preps are in work,” added NTD processing status. “J box foaming preps are in work. Aft hardpoint primer is in cure. All systems electrical test is complete.”

Stacking of STS-134’s Solid Rocket Boosters (SRBs) have also picked back up in High Bay 1 (HB-1), following a few days of standdown due to poor local weather.

“In the VAB on SRB stacking, started back up last week; were delayed by weather for a couple of days. Moved the left forward center segment over; it is in work,” noted KSC Ground Operations on the Standup report, which was elaborated on via the NTD status update.

“SRB BI-145 / RSRM 113 (VAB HB-1): Left and Right tunnel cover bond preps are complete. Right Aft Center clevis preps are complete. Right Forward Center tang preps are complete. Right Center Joint segment mate preps are in work. Segment was lifted to HB-1 at 2000 (Monday).

“Leak check panel validation, run 4, complete. Right Aft Joint closeouts are complete. Right Aft Joint splice plate installation is complete. Hold down post ordnance preps: Upper shock absorbers are installed in blast containers. Clip installation is complete.”

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