STS-134’s additional EVA to pick up on deferred ISS Stage work

by Chris Bergin

The changes to Endeavour’s final mission have been outlined at a Program Requirements Control Board (PRCB) meeting, which approved the addition of two docked days and a fourth EVA for STS-134. The additional work will focus on the installation of the FGB Power Data Grapple Fixture (PDGF), which was deferred from ISS US EVA-15, due to the successful changeout of a failed Pump Module.

STS-134 Processing Latest:

Endeavour continues to track a late February launch date – pending Discovery launching within her restricted launch windows in November or December – and continues to enjoy a very smooth processing flow inside her Orbiter Processing Facility (OPF-2).

“OV-105 (OPF Bay 2): Integrated hydraulic brake/anti-skid/nose wheel steering checkout was completed. SSME (Space Shuttle Main Engine) TVC (Thrust Vector Control) and ET (External Tank) actuator cycling completed,” noted the NASA Test Director (NTD) processing update (L2). “Weekend Work: None.”

Two DTOs (Detailed Test Objectives) are also being prepared on Endeavour, with the Boundary Layer Transition (BLT) mod – a continuing experiment which measures the effects of increased heating as the orbiter returns to Earth via a protruding tile and associated instrumentation – and a Catalytic Coating experiment, which is applied to two Thermal Protection System (TPS) tiles, providing Orion – and shuttle – engineers with refined aeroheating data.

“OV-105 (STS-134) Working boundary layer transition mods. Did find some protuberance tiles with coating damage. Performing R&R of those tiles now,” noted KSC Ground Operations (L2). “Continuing with system testing. Continuing on schedule.”

STS-134 related preparations are also ongoing in two of the Vehicle Assembly Building (VAB) High Bays, with processing work on Endeavour’s twin Solid Rocket Boosters (SRBs) and the tank that is currently set to be allocated to the mission.

With High Bay 3 (HB-3) now vacated – following Discovery’s rollout to the pad as the STS-133 stack – the Mobile Launch Platform (MLP) with STS-134’s stacked boosters will soon be “rolled around” from HB-1.

“SRB BI-145 / RSRM 113 (VAB HB-1): L/R (Left/Right) Insta Foam Spray RH/LH foam trim complete waiting on pull test results. PDL (foam) on the small void on L/R cameras will be performed after roll around,” added the NTD report. “Plunger installation is complete less paint cures. Blast shield installation won’t be worked until after optics is shot for ET mate. Preps are complete the stack is ready for roll around.”

Once in High Bay 3, it is expected that ET-122 will be mated with the boosters later this year, although continuing questions over the final green light for STS-135 – due to the ongoing wait for funding to be sent to NASA for the authorized mission – still means no official decision has been taken on if the newer ET-138 should be held back for the extra mission, or flown with STS-134.

“ET-122 (VAB HB-4E): Aft Hard Point Conathane cure and BX-265 foam spray is complete,” noted NTD processing information. “GUCP 7 (Ground Umbilical Carrier Plate) in QD (Quick Disconnect) installation and primer application is complete. RH pivot assembly to RH Bracket interference PR (Problem Report) is complete.”

“Had a weld scratch on the third hard point that was sanded, blended, and dye penned,” added the tank’s contractor, Lockheed Martin. “That will be used as repaired. No other defects noted.”

STS-134 Specific Articles:

STS-134 Mission Change:

As noted earlier this month, NASA managers decided to change STS-134’s mission content, by increasing the flight by two days, in order to accommodate an additional spacewalk (EVA-4). As expected, the change was approved by the all-powerful PRCB meeting last Thursday.

“Purpose: Approve Change Request (CR) to update the STS-134 Flight Definition and Requirements Document (FDRD): Mission Duration to 14+1 days. EVAs to 4+1,” noted the document presented to the PRCB (available on L2).

“Rationale of Change Request: Additional two docked days are required to perform the additional EVA during STS-134 mission. EVA added to perform FGB Power Data Grapple Fixture (PDGF) installation. Was to be performed during ISS US EVA 15 but deferred due to unscheduled Pump Module R&R.”

The decision wasn’t a surprise, with several pre-emptions of extending the mission already seen internally – and even publicly via one astronaut on twitter – with the presentation itself noting managers had already recommended “adding to the STS-134 flight at the 09/28/10 SSPCB (Space Station Program Control Board).”

The presentation itself covered numerous areas relating to the mission, such as the enhanced reach of the Integrated Boom Assembly (IBA), with notes including “reach capability over solar panels can be further improved by employing alpha and beta solar panel joint rotations,” referring to the plan to leave the Orbiter Boom Sensor System (OBSS) on Station, as a parting gift from Endeavour.

However, the focus was on the additional docked days and the extra EVA, with several changes installed into the flight plan.

As part of those changes, the presentation noted that the Lab EWC Antenna will be added to the EVA-1 tasks, along with the S1 Radiator Grapple Bar Stow Beams task being added to EVA-2. An additional 15 minutes of off-duty time was also incorporated into Flight Day 6.

Flight Day 8 is now listed as a water dump placeholder, along with EVA prep and four hours of off-duty time, ahead of Flight Day 9’s EVA-3, now listed as FGB PDGF, FGB Y-Jumpers and potential CP7 ETVCG R&R. The original EVA-3 tasks are pushed into EVA-4’s timeline, which will follow Flight Day 10’s Docked Late Inspection.

“Install FGB PDGF. Tie down fiberglass MLI (insulation) removed from FGB. Install transfer frame with PDGF and FGB cable harness. Install Video Signal Converter (VSC) and VSC thermal covers. Install and route external 1553 cables for FGB PDGF,” listed some of the specifics of the additional EVA tasks. “Retrieve Strela Adapter from PMA3 and install in FGB PDGF. Photos of FGB Thrusters.”

Refinements to the extended mission included the need to use additional ISS Lithium hydroxide (LiOH) canisters and the addition of around 16lbs of GN2 – none of which hold any mission impact.

“EVA concurs with change in mission duration to add 4th EVA for addition of FGB PDGF task,” noted the presentation’s findings. “Initial NBL (Neutral Buoyancy Laboratory) evaluation estimated FGB PDGF installation with FGB thruster photos and Strela adapter get-aheads is approximately 4 hours.

“From 9/20 SSPCB, EVA wireless communication system and FGB Y-cable task was added to open EVA time. An additional ~16 lbs of GN2 is required to support the increase in mission duration and the 4th EVA.

“Currently planned transfer of 50 lbm will be adjusted to reflect this additional requirement. No impact to APM (Ascent Performance Margin) as the GN2 tanks will remain full. Three extra LiOH cans will be required from the ISS stockpile.”

With no objections – or disapprovals – noted at the PRCB, managers concurred with the recommendation to install the changes into Endeavour’s mission content.

“Recommendation: Approve CR to change FDRD. Mission duration from 12+1 to 14+1 days. EVAs from 3+1 to 4+1.”

(All photos and graphics via L2).

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