STS-133: Discovery waiting on Right OMS removal and launch date decision

by Chris Bergin

With manifest meetings set to take place in the next couple of weeks, Discovery continues to be deep in processing for her upcoming STS-133 mission. While program managers are working on confirming a mission extension by three days – with two EVAs added – processing on Discovery is concentrating on the repair of the helium valve that led to a large amount of flight rationale discussion ahead of her STS-131 mission.

STS-133 Processing Latest:

Officially still targeting a September 16 launch date, STS-133 has been likely to slip for some time, primarily due to tight processing timelines relating to the turnaround of the MLPM Leonardo into the Permanent Multi-purpose Module (PMM) which will remain with the International Space Station (ISS).

However, work on the module is not believed to be hugely behind schedule – although references have been made to FOD (Foreign Object Debris) damage to MPLM/PMM pressure vessel.

Regardless, talk of slipping the flight into October or November remains solid within the Space Shuttle Program (SSP).

Such a slip may be related to the changes being installed via a Change Request (CR) to increase the mission content via the addition of two EVAs – which will require additional training being placed into the crew loading timeline.

“Put a CR in the system last week to add the two EVAs to STS-133 and adjust the mission duration appropriately,” noted Flight Operations & Integration via the latest Shuttle Standup/Integration report (L2). “That will be coming to a board in the next couple of weeks.” (screenshot from May 28th’s “FAWG” Manifest Presentation – L2).

With STS-133 previously manifested with no spacewalks – given it was set to be the last mission to fly, prior to the delay and manifest order swap with STS-134 – the mission length will be remanifested as 11+1 days, an increase of three days from the previous schedule of 8+1.

The all-powerful Program Requirements Control Board (PRCB) were also updated on the status of the mission via a 100 page presentation (L2), which will be summarized into an upcoming article.

As far as Discovery herself, processing has been proceeding along the timeline without any major issues inside her Orbiter Processing Facility (OPF-3), with only 18 Interim Problem Reports (IPRs) charged against her flow since returning from STS-131.

A large amount of work is taking place on repairing the troublesome helium isolation valve on the Right Reaction Control System (RRCS), with the entire Right Hand OMS (Orbital Maneuvering System) Pod soon to be demated from Discovery for repairs to take place in the Hypergolic Maintenance Facility (HMF).

As noted during the flight rationale meetings ahead of STS-131’s launch, the option to replace the faulty valve would have resulted in rollback and demating inside the Vehicle Assembly Building (VAB), given the valve is impossible to access without the removal of the Pod from the orbiter. As predicted, the system performed without issue via the backup regulators in the system.

“OV-103 (STS-133) Completed all SCAPE ops for the RH pod removal. Also completed the electrical de-mates. Will pull the RH pod on June 2 and send out to the HMF for repair,” noted KSC Integration on the Standup Report, with the NASA Test Director (NTD) also noting current status on the preparations.

“OMS/RCS cross-feed line fuel and oxidizer drain for the right OMS pod removal and flange disconnect complete,” which in turn led to at least one of the recent IPRs – with SCAPE (Self-Contained Atmospheric Protection Ensemble – suits used while performing task related to hydrazine operations) precautions in effect due to the hazardous nature of the work.

“OMS Cross-feed SCAPE operations: IPR-0016: After SCAPE operations for the fuel cross-feed line sample ground-half coupler installation were completed, a leak was discovered. SCAPE was re-initiated and troubleshooting revealed the leak to be in the flex hose mated to MD686,” added the NTD. “The flex hose was replaced and OPF-3 was opened for controlled work.”

Although engineers were given the Memorial Day weekend off, it remains a busy flow for what may be Discovery’s last mission (pending the approval of STS-135, and decision on which orbiter – either Atlantis or Discovery – will gain the honor).

STS-133 Specific Articles:

“OV-103 (OPF Bay 3): RH OMS pod removal preps continue. Pod removal is scheduled for next week. Preps for PRSD (Power Reactant Storage and Distributation) tank set 5 removal is in work. Tank removal is planned for late next week,” added NTD processing information (L2).

“Atmospheric Revitalization Pressure Control System (ARPCS) checkout continue. MSBLS (Microwave Scan Beam Landing System) waveguide leak checks were completed with nominal results. Mass Memory Unit 1 (MMU) reinstallation. MMU 1 installation and electrical connects are complete, load to follow.

“MPS Engine Cut-Off (ECO) system checkout is scheduled to pick up, and will be completed on Tuesday. No weekend or Memorial Day work is scheduled.”

Troubleshooting on the Ku Band antenna system has revealed the STS-131 mission suffered from a random failure, that in fact has no commonality with a previous issue reported on STS-92 – as had previously been assumed.

“Analysis continues on the Ku-Band transistor. When compared to the previous Ku-Band failure, the two are not anything alike. There is no commonality with the STS-92 failure. Currently, it appears to be a one of a kind, random failure,” noted the Orbiter Project at the Johnson Space Center (JSC).

The root cause of the issue was tracked back to a fault with the Deployed Assembly (DA) unit, which has since been removed and replaced, although interference with Discovery’s Orbiter Docking System (ODS) caused engineers to revisit the Ku system recently.

“Ku signal radar acquisition would not acquire the signal. Constrains Final stow for flight. Most probable cause, interference from the ODS platform,” added processing information, as it became a new IPR on the STS-133 flow – prior to being resolved.

“IPR 0014 (Ku-band radar acquisition would not acquire the signal) Update: Radar search was performed with Orbiter Docking System (ODS) platform removed and Traveling Wave Tube Amplifier commanded to ON. Target acquisition was successful and the IPR will be closed as ‘procedural error’ with a deviation written to ensure ODS platform is removed prior to search operations on the target.”

Despite the large strides made with the mitigation of foam liberation from the External Tank’s intertank region – with the root cause confirmed and production changes at the Michoud Assembly Facility (MAF) providing two clean tanks in a row – pull/plug tests are continuing on the downstream tanks to check the adhesive properties between the intertank structure and the foam.

With ET-137 undergoing routine checks in the VAB’s High Bay 4E, mating with the twin Solid Rocket Boosters – currently being stacked in High Bay 3 – has been delayed by about a week. No specific reason was given for the change in schedule.

“There will be a delay on the actual mate of the ET stack for STS-133,” noted the KSC Launch Integration Manager on the latest Standup report. “The ET/SRB Mate Review scheduled for next Friday will slip by approximately a week. A notice will go out on the new date.

“In the VAB on SRB stacking, completed the mating of the right FWD segment. The right FWD assembly is in work; will wrap up with the left FWD segment and left FWD assembly early next week.”

ET and SRB operations in the VAB have also gained the Memorial Day weekend off, prior to processing starting back up on Tuesday on the left booster’s stacking, and the finalization of work on ET-137 ahead of mating.

“SRB BI-144 / RSRM 112 (VAB HB-3): Joint closeouts continue. Left Forward segment stacking is scheduled to begin next Tuesday,” added the NTD report.

“ET-137 (VAB HB-4E): LO2/LH2 17” Disconnect Measurement; LO2 plate installation, LH2/LO2 flex hose installation, purge, press and leak checks are all complete. Bond adhesion test repairs; Foam residue removal and Environmental enclosure construction are complete.”

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