STS-133: Discovery enters her final month of OPF processing ahead of rollover

by Chris Bergin

With over 128 million miles on her clock, Discovery is now into the final month of her flow inside the Orbiter Processing Facility (OPF) for her 39th and final mission, as she prepares for rollover to the Vehicle Assembly Building (VAB) on September 8. Meanwhile, investigations are ongoing into the Reaction Control System (RCS) Test Article failure in New Mexico.

STS-133 Processing Latest:

Discovery is processing in OPF-3 for her November 1 launch to the International Space Station (ISS). STS-133 was set to be the final mission of the Space Shuttle Program (SSP) until payload problems resulted in a realigned manifest that pushed Discovery’s flight ahead of Endeavour’s heavily-delayed STS-134 mission.

In what is highly likely to be the veteran orbiter’s final processing flow for flight, the milestones of rollover and rollout will likely be marked by ceremonies that will be even more poignant than Atlantis’ STS-132 events – considering many observers were aware Atlantis already had one eye on an additional flight via the proposed STS-135 mission.

With just one more month of her OPF flow remaining, her dedicated engineers are seeing their own final milestones for the old girl, with the final closure of the Payload Bay Doors (PLBDs) upcoming this week – only to be opened one final time at the launch pad when she receives her payload.

“OV-103 (STS-133) Working on preps for PLBD closure, will close the PLBDs next week. Have some TPS (Thermal Protection System) work to do, then will cycle to final closure,” noted Ground Operations on the latest Shuttle Standup/Integration report (L2).

“Working preps for crew module leak checks to be performed tonight. Installing BRI tile on the ET (External Tank) doors. Working the valve position indicator (VPI) indicator on the O2 crossover valve, IPR-35 (Interim Problem Report), and will do some more troubleshooting on that.”

IPR 35 – relating to observations made during data reviews on the O2 system 1 crossover valve – found that the VPI indicated “on” when it should be indicating “off”. This issue remains under review.

“IPR 35 update: O2 system 1 crossover valve cycles (5) were performed.  When (engineering teams working the issue) returned (the) VPI state at power up had changed from the indication prior to orbiter power down. Troubleshooting indicates the valve is physically closed and the issue may reside with the VPI. Engineering evaluation continues,” noted the NASA Test Director (NTD) report (L2).

The NTD also noted other processing work being carried out on Discovery, including TPS operations that have been ongoing through the weekend, along with the closure of one of the early issues in the flow – IPR 5, the problem which was recently highlighted by cable issues.

“OV-103 (OPF Bay 3): Crew Module leak checks were completed and results were nominal. Nose Landing Gear boot repair was completed and RTV is in cure. IPR 5: finished troubleshooting the in-flight anomaly on the S-Band Antenna system. Were not able to duplicate the problem seen on-orbit and expects to close the IPR as an Unexplained Anomaly (UA).”

As per usual, managers will review the status of Discovery’s flow one week ahead of her scheduled rollover to the Vehicle Assembly Building (VAB) – which is currently on track for September 8.

STS-133 Specific Articles:

“The Orbiter Rollout Review for STS-133 is September 1,” confirmed the KSC Launch Integration Manager on the Standup report. “On track from rollover to the VAB on September 8.”

There she will link up with External Tank (ET-137) and the twin Solid Rocket Boosters (SRBs) in High Bay 3 (HB-3) for mating operations. Repair work continues to be carried out inside the VAB on a Fairing Support Plate, following problems with the initial TPS work that was conducted over the last few weeks.

“SRB BI-144 / RSRM 112 / ET-137 (VAB HB-3): PR (Problem Report) ET-137: Damaged SLA (foam) on EB-2 Fairing Support Plate; Will Hand Pack both inboard and outboard. New SLA kit has been ordered and will arrive next week,” added the NTD.

“Aft Strut and HDP (Hold Down Post) Firing Line checks are complete. Forward Firing Line checks will be worked after ET Fairing is installed after SLA repair is complete on PR.”

RCS Test Article Failure Update:

The failure suffered by the RCS test article – otherwise known as the “Fleet Leader” – at the White Sands Test Facility (WSTF) remains under investigation, with the latest results scheduled to be reviewed by the Orbiter Project Office (OPO) this coming Wednesday.

Since 1989, the Fleet Leader Program has played a vital role in NASA’s ability to detect, predict, and prevent Orbital Maneuvering Subsystem (OMS) and RCS life-dependent failures and anomalies before they affect the shuttle fleet.

The New Mexico facility’s test article functional tests simulate orbiter flight and maintenance downtime period activities, and special propulsion subsystem tests, using all of the Fleet Leader test articles.

Other special tests have been performed to support the Fleet Leader Program, such as the OMS/RCS Crossfeed Line Gas Sweep Test (Test Stand 301), the Forward Interconnect System Test using FRCS Test Article (Test Stand 328), and Chamber Chiplife.

A problem during testing on the hardware was reported a few weeks ago, relating to a firing of the RCS fleet leader unit experiencing an unplanned controlled shutdown – a result of a large crack in a weld that is between the closeout of a fuel manifold and the injector.

The related hardware is being investigated via both Non Destructive Evaluations (NTE) techniques and more intrusive inspections, in order to understand the root cause.

“On the WSTF RCS test article investigation, the team has completed sectioning of the injector part that has the crack. Half of the part is being used for NDE development, and the other half for detailed destructive evaluation. The crack has been opened, and fractography is beginning,” noted OPO on the Standup report.

“Continuing to inspect the valve sensors, transducers and perform radiography. Also doing a chemical evaluation of what was flushed out of the thruster prior to the cut. There will be an OPO Tech Tagup next Wednesday to discuss all the known data.”

This issue will not impact STS-133’s upcoming Flight Readiness Reviews (FRRs) unless commonality with the fleet’s flight hardware is found.

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