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As a result, three of Endeavour\u2019s thrusters were deselected and Endeavour\u2019s crew, and ground controllers temporarily lost their ability to monitor the Reaction Control System Jet Leak Indications, though \u201cfuel leak detection capability (was) maintained via oxidizer temp sensor due to thermal crosstalk.\u201d<\/p>\n
After the mission, the suspect card was Removed and Replaced (R&R\u2019ed), and the replacement was found to be in proper working order.<\/p>\n
Another IFA reviewed by the OPO was the failure of the Flash Evaporator System (FES) Pri-A controller, which, like the DSC card, failed during shortly after lift-off.<\/p>\n
\u201cDuring ascent, the FES Pri-A controller shut down while in full up mode with high load and topper operating,\u201d notes the OPO presentation. \u201cThe FES had been operating with no anomalies prior to the event.\u201d<\/p>\n
Several attempts were made to restart the Pri-A controller during the mission; however, the attempts were not successful.<\/p>\n
During post-flight processing, the Pri-A controller was R&R\u2019ed and confirmed to have a failure within the shutdown logic circuit of the IC chip \u2013 the first failure of an IC chip.<\/p>\n
Additionally, a pressure decay indication from Auxiliary Power Unit 1 (APU-1) was a topic of discussion at the readiness review.<\/p>\n
\u201cFuel tank pressure began to decay shortly after APU ascent shutdown, at a rate greater than what could be attributed to thermal cooling,\u201d notes the OPO. \u201cSystem instrumentation (was) not able to distinguish between fuel (hydrazine) or GN2 leakage.\u201d<\/p>\n
Sensors indicated a leak of approximately 4-psi\/day through Flight Day-10 (FD-10) before the pressure stabilized at 228 psia on FD-14.<\/p>\n
Post-flight testing focused mainly on a Quick Disconnect (QD) poppet, the source of a similar pressure decay during Discovery\u2019s STS-121 flight in July 2006. Testing confirmed that the suspect poppet was in fact contaminated; however, further testing at White Sands Test Facility (WSTF) proved inconclusive.<\/p>\n
\u201cLeakage testing of QD at WSTF showed that presence of hydrazine does not necessarily affect QD leakage. R&R\u2019ed seal and poppet on (Discovery) after STS-121 have since flown twice with no leakage.\u201d<\/p>\n
Engineers believe that the leakage of Endeavour\u2019s APU-1 on orbit was caused by a combination of low temperatures and \u201cother seal variables,\u201d notes the OPO FRR presentation.<\/p>\n
The last IFA reviewed from Endeavour\u2019s previous flight pertained to the ongoing omega bend issue with the shuttle fleet\u2019s Payload Bay radiator retract hoses.<\/p>\n
\u201cForward Starboard radiator retract hose \u2018C\u2019 bend noted post-flight,\u201d notes the FRR document. \u201cSubsequent Payload Bay Door cycles showed nominal hose retraction into the storage box.\u201d<\/p>\n
At this time, the SSP has accepted a flight rationale to fly this hose \u2018as is\u2019 for STS-126 \u2013 with the final hurdle before flight being the successful closure of Endeavour\u2019s Payload Bay Doors at the launch pad, an option that was completed without issue last week.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2008\/11\/a42.jpg\")
Also reviewed during the FRR were several IFAs from STS-124. The first such IFA pertained to the partial late release of one of the many RCS Tyvek covers.<\/p>\n
\u201cGround imagery showed that when thruster F3D and F4D Tyvek rain covers released, a small piece remained attached to the thruster lip,\u201d notes the readiness review presentation.<\/p>\n
A similar event was observed on STS-118 in August 2007. As a result, the Tyvek covers were modified so that they carried the minimum thickness in the \u201ctear initiation region.\u201d This modification was flown on all subsequent flights to STS-118 with the first anomaly occurring on STS-124.<\/p>\n
\u201cAnalyses and impact testing were performed using a larger remnant mass size than seen on STS-118 and STS-124.\u201d The associated risk of a late-release of a Tyvek cover has been accepted by the Program Requirements Control Board (PRCB). Thus, there is no constraint for Endeavour\u2019s mission.<\/p>\n
Also discussed was the Rudder Speed Break (RSB) Spring Tab liberation event that occurred late in Discovery\u2019s mission. \u201cMicro\/tactile inspection performed for STS-126 \u2013 discrepant parts (6) replaced,\u201d notes the FRR document.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2008\/11\/a32-300x206.jpg\")
Since these tabs are only used for thermal protection of the Orbiter\u2019s RSB from plume recirculation during ascent, they are not a vital thermal protection component during reentry. The final STS-124 IFA review slide notes an excessive Type A flow on Wing Leading Edge Tee Seal Rib Splice 10.<\/p>\n
The presentation notes that \u201cfollowing STS-124, a region of excessive Type A flow was observed on the right-hand wing leading edge tee seal at rib splice 10 during the runway inspection.\u201d<\/p>\n
Subsequent inspections revealed \u201ca large forward-facing step and gap along the lockside interface to the mating WLE panel 9R that was not apparent before flight.\u201d<\/p>\n
After engineers removed the tee seal, a deterioration of the leading edge as well as a Type A glass flow were discovered. Comparable discoveries were identified on Discovery\u2019s left wing as well.<\/p>\n
While entry heating did not exceed mission critical temperatures, and no damage to Discovery\u2019s SiC was observed, this issue prompted a review of Endeavour\u2019s RCC and T-seal panels.<\/p>\n
\u201cThe LESS PRT reviewed and verified the vendor lockside measurements and accepted that no similar conditions exist on the OV-105,\u201d notes the OPO presentation.<\/p>\n
Endeavour\u2019s Safety and Mission Enhancements:<\/p>\n
Emphasizing NASA\u2019s continued directive of improving safety with every mission, several enhancements have been made to \u2013 or will be implemented during \u2013 Endeavour\u2019s highly important logistics run to the International Space Station (ISS) this month.<\/p>\n
The first improvements deal with Carbon Dioxide (CO2) levels and air recirculation standards in the crew cabin.<\/p>\n
\u201cDuring STS-123, crew reported symptoms of high CO2 concentrations in the shuttle airlock and middeck,\u201d notes the readiness review document.<\/p>\n
An airflow analysis was performed to determine any areas where CO2 concentrations may develop and exceed safety levels.<\/p>\n
\u201cAnalysis indicates that the flow velocities in various locations violate the 15 ft\/min minimum OVEI requirement. OVEI cabin ventilation shall be 25 feet per minute (fpm) nominal and the allowable range shall be 15 to 40 fpm.\u201d<\/p>\n
The presentation notes that crew equipment stored in the middeck during the mission can interfere with the air circulation requirements. To this end, NASA has developed several mitigation techniques, including modified LiOH canister change out schedules, activation of airlock booster fans prior to docking with the ISS, as well as using additional middeck air registers.<\/p>\n
Another safety improvement is the D-Hatch decal relocation, a modification that was originally due to debut on Atlantis during STS-125. The relocation effort relates to difficulties experienced by the STS-124 crew in closing the upper airlock \u201cD\u201d hatch.<\/p>\n
Analysis of the misplaced decals revealed that \u201ca stop bolt modification and re-rigging was previously implemented but the hatch decals were not relocated to match the revised configuration.\u201d<\/p>\n
The problem, which was discovered to be fleet-wide, has been corrected by placing the decals in the correct locations, and covering the misplaced decals with white tape.<\/p>\n
Another modification taken from STS-125 pertains to the Aft Window Shade revision.<\/p>\n
\u201cAt STS-125 CEIT (Crew Equipment Interface Test), crew requested elimination of additional light through previously modified window shades to facilitate sleep on the flight deck,\u201d notes the presentation. The modification was successfully tested and adopted by the STS-126 crew.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2008\/11\/a25.jpg\")
Furthermore, another modification has been made to Endeavour\u2019s MO10W Panel O2 System number 2.<\/p>\n
\u201cDuring system checkout for STS-126 an anomaly was noted in the ARPCS O2 system #2 crossover valve,\u201d notes the presentation. \u201cDecision was made to install a jumper line with a check valve to bypass the faulty valve.\u201d<\/p>\n
The modification does not impede any oxygen flow requirements to the Advanced Crew Escape System suits or extra-vehicular mobility unit manifolds. Proper indicators and revisions to the flight procedures have been implemented to account for the bypass.<\/p>\n
The final safety modification flying on Endeavour is one that was originally scheduled to debut on STS-119 \u2013 and then advanced to STS-125 before that mission\u2019s postponement.<\/p>\n
The modification relates to the replacement of MA-8 inertia reels in the lightweight crew seats with MA-16 inertia reels.<\/p>\n
\u201cThe MA-8 inertia reels in the lightweight seats lock only through differential acceleration of the crewmember and the seat in the forward X direction. During a low onset acceleration event, the inertia reel may allow the crewmember to become dislocated from the seatback,\u201d notes the readiness review document.<\/p>\n
The new inertia reels will provide sufficient restraint for crewmembers in all possible acceleration directions.<\/p>\n
In addition to the interior safety modifications, two Payload Bay configuration changes have been made to Endeavour. The first configuration change relates to the removal of handrails near the Lightweight Multipurpose Experiment Support Structure Carrier (LMC).<\/p>\n
\u201cClearance studies showed less than 3\u201d static clearance between LMC contingency latching pin and 1307 bulkhead handrails,\u201d notes the OPO document.<\/p>\n
Since the LMC is non-deployable, and the handrails in question would not be accessible by the crew on-orbit, the handrails\u2019 removal will not affect any aspect of the mission.<\/p>\n
The rails in question were removed in late October during payload installation ops at Pad-A.<\/p>\n
The second Payload Bay configuration change comes from the Multi-Purpose Logistic Module Latch Guides, which are needed to help guide on-orbit berthing operations of the MPLM at the end of Endeavour\u2019s mission.<\/p>\n
\u201cIssues identified with original configuration using 24\u201d latch guides on forward and aft sides of each latch,\u201d notes the presentation. \u201cPotential contact with OBSS (Orbiter Boom Sensor System) under worst case deflection on starboard side and potential contact with payload bay crossover wire bracket with aft mounted guide.\u201d<\/p>\n
The modification will see the installation of 22\u201d latch guides. This change will resolve the OBSS issues while still accepting a remote failure case.<\/p>\n
In addition to the above modifications, efforts to install BRI (Boeing Reinforced Insulation) tiles around Endeavour\u2019s landing gear doors and External Tank umbilical well doors continued during Endeavour\u2019s flow from STS-123, improving the resiliency of the vehicle\u2019s Thermal Protection System in critical seal areas.<\/p>\n
L2 members<\/em><\/em>: All documentation \u2013 from which the above article has quoted snippets \u2013 is available in full in the related L2 sections, now over 4000 gbs in size.<\/em><\/em><\/p>\n","protected":false},"excerpt":{"rendered":" As Endeavour heads into the home stretch of pad processing before her scheduled launch on November 14, technicians and program managers continue to emphasize \u2013 through a series of Flight Readiness Reviews (FRRs) \u2013 the multiple safety and mission enhancements debuting on the fleet\u2019s youngest Orbiter. Making a lengthy presentation before the Space Shuttle Program (SSP) FRR […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[3610,9219],"class_list":["post-41269","post","type-post","status-publish","format-standard","hentry","category-news","tag-frr","tag-sts-126"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41269"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=41269"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41269\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41269"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}