STS-127: Engineers carrying out minor repairs ahead of countdown

by Chris Bergin

As STS-127 prepares to enter S0007 Launch Countdown operations on Wednesday night, engineers have carried out repairs on areas of the External Tank (ET-131) Thermal Protection System (TPS) foam, and what appears to be a chip on the left hand Solid Rocket Booster (SRB). All areas are deemed as minor and should be cleared for flight in time for the L-1 Mission Management Team (MMT) meeting.

STS-127/Endeavour Processing Latest:

Endeavour remains on track for the July 11 launch from Pad 39A, with no serious issues being worked on the vehicle. The STS-127 crew – led by Commander Mark Polansky – also made their journey from Houston, arriving at the Kennedy Space Center (KSC) on Tuesday afternoon.

Over the holiday weekend, S5009 operations – including Range Safety checkout and GUCP (Ground Umbilical Carrier Plate) ordnance connect – were completed, while the majority of recent flow work involved S0071 (Hyper loading/pressurization) operations, which have also been completed.

“S0071 Hyper Pressurization: OMS/RCS (Orbital Maneuvering System/Reaction Control System) Helium Regulator Lockup was completed. MPS/SSME (Main Propulsion System/Space Shuttle Main Engine) Helium Tank Fill is complete,” noted Tuesday processing information on L2.

“OMS/RCS GHe/GN2 Stage 1 Press is complete. S0007.100 Launch Countdown preparations continue. Two waves of LH2 replenishment were successfully completed yesterday.”

S0007 Launch Countdown Call To Stations is set for Wednesday, July 8 at 2130 EDT, with the milestone checkpoint of the L-1 MMT briefing scheduled for July 10 at 0900 EDT.

“It is good to have everyone back from the July 4th weekend. Hope that everyone had the chance to rest and visit with their families,” added Shuttle Manager John Shannon on the latest Standup/Integration report on L2.

“The STS-127/2JA flight will be a long mission, with many objectives to accomplish. Everyone needs to be ready for launch and to be sure the mission is properly executed.”

External Tank Inspections:

Following ET-131’s successful tanking test on July 1, pad and ET engineers have completed a full evaluation of the tank’s TPS, providing a list of items that may be of interest, or may require repair ahead of launch. Three such areas were found on the tank, with repairs taking place throughout Tuesday.

t21“An External Tank LO2 feed line inspection was completed yesterday with three foam discrepancies observed,” noted Tuesday processing information. “Two of them will require no work (ET-131-TS-0020/0021). ET-131-TS-0019 was generated for a 2.5” piece of cracked foam that will require the LO2 feed line platform and diving boards to repair.”

Expanding on the flow update, inspection logs and photographs Рacquired by L2 on Tuesday morning Рoutlined the ET areas of interest in greater detail.

“Post Tanking LO2 Feedline Inspection: Inspection was performed on LO2 feedline for STS-127/ET-131 to assess the potential debris noted behind station XT1129 on the Post Tanking Scrub Walkdown and to quantify any chaffing on the LO2 Feedline Brackets, LO2 Feedline and the Intertank.

“XT-1115 (Intertank to LO2 Feedline): There are several areas of chatter/chaffed foam on the Intertank that appear to be within the bounds of (requirements) and no loose material present. There was little to no change to the area as observed on the Post Drain Walkdown.

“An inspection behind the feedline was performed and there was no chatter marks observed on the LO2 Feedline. Will be initiating a PR (Problem Report) on this item and we will be processing a MRB (Material Review Board) for ‘use as is'”

“XT-1129: Removed all loose debris and inspected the location and the area had minor amount of foam chatter that was not apparent prior to the Tanking. Will be initiating a PR on this item and we will be processing a MRB for ‘use as is’ to assess the damage and any potential debris concerns.”

t31The main area that underwent evaluation is on the inboard LO2 Feedline Bracket Strut, which has two cracks on its aft face. Engineers are likely to work a procedure to remove the damaged materials, eliminating the potential for it to become a debris concern during launch.

“XT-1377: The larger of the cracks is emanating from a point on the aft side of the strut approximately two inches from the +Z end. The smaller crack is located on the chamfer at the +Z end of the strut.

“The larger crack appears very similar to the crack that was observed on STS-121/ET-119 prior to the piece liberating and being discovered on the MLP (Mobile Launch Platform).

“The local consensus is to process an MRB to remove the loose material to alleviate the debris concern, assess any icing concerns, and essentially fly in the same configuration as STS-121/ET-119.

“Will be coordinating the disposition with ET Project and we will have MRB approval prior to any foam removal. The PR has been initiated. All other Feedline Bracket locations appear to be in nominal condition.”

LH SRB Crack/Chip:

During the walk-downs last week, engineers spotted what appears to be a paint chip on the LH (Left Hand) SRB, located a couple of inches above the field joint. Following the configuration of safety ropes and access platforms, repair work is expected to be completed by Wednesday morning.

t4“During a surveillance walk down of the BI-138 Booster set located at Pad-A it was observed that a possible impact of the LH Booster by an unknown source could have occurred,” noted an engineering report on L2.

“A suspect mark on the LH Booster topcoat was noted at approximately the 22 degree location on the 155 foot level. The size of the ‘mark’ is guessed to be .15 X .005 inches.”

Other notes class the mark – caused by windstorm on June 26 – as “hard to identify”, though it will be repaired ahead of flight, given the confidence that the damage is only cosmetic.

“An issue in work for STS-127/2JA concerns loss of coating on the left-hand center-forward segment, resulting from a windstorm on June 26. This is a very small area, but it is being investigated,” added notes.

“Photos were taken of the area, but the clarity and detail of the pictures cannot indicate if the area is in fact an impact mark or an unknown foreign material.

“Once we gain access, a sample will be taken of the area, any raised metal will be sanded and removed, Eddy Current will be performed, and primer and topcoat will be applied.

“High Crew has installed access to the SRB anomaly on 155′ level of Pad A. The SEAT has assessed the access and pending installation of an additional support to resist horizontal loads (expected 2nd shift), it will be ready for use.”

L2 members: Documentation Рfrom which 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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