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\u201cAir to GN2 changeover complete at 0513 EDT. LO2\/LH2 final load preps are in work. BDA (Blast Danger Area) clear will pick up at 0630 EDT. Ops\/Eng Tanking Briefing is scheduled for 0800 EDT. ET load Weather Briefing 0845 EDT. LO2\/LH2 tanking around 0926 EDT (confirmed as 09:36). T-0 is expected at 1851 EDT,\u201d outlined Monday morning processing status.<\/p>\n
The weather was once again an issue for Monday\u2019s attempt, with forecasts noting a 60 percent constraint to launch by the time STS-127\u2019s countdown reaches T-0. Also, rain during the launch countdown would be very problematic for an exposed tyvek cover \u2013 as noted in attempt 4\u2019s article.<\/p>\n
With the delay to Wednesday, the Rotating Service Structure (RSS) will be placed back around the vehicle for a replacement of the cover.<\/p>\n
Water intrusion into the thruster holds the threat of freezing during ascent, which could cause problems for its operation on orbit. However, it was the weather in the local area for around T-0 that resulted in another scrub being made official.<\/p>\n
Several \u201cfunnies\u201d had also been listed at the Mission Evaluation Room (MER) at the Johnson Space Center (JSC), ranging from GSE (Ground Support Equipment).<\/p>\n
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![\"T-0_Umbilical_Slush2a\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T-0_Umbilical_Slush2a.jpg\" "\\"T-0_Umbilical_Slush2a\\"")
The main notes on the MER list related to findings by the Ice Inspection Team \u2013 which had arrived at the pad to look at all areas of the shuttle after tanking had entered stable replenish.<\/p>\n\u201cTPE 127V-0134, During ICE Team inspections, 3\u201d x 3\u201d x 1\/2\u201d ice buildup on the bottom of the LH2 T-0 umbilical,\u201d noted the MER funny, acquired by L2. \u201cETM 127V-0135, During ICE Team inspections, frost with crack on the LH2 Pyro Cannister.<\/p>\n
\u201cLH2 T-0 Umbilical Ice \u2013 Constraints both S0007.200 OP 16-1151 coming out T-9 minute hold.\u201d<\/p>\n
During the hold ahead of T-9 minutes, a waiver was issued to allow the vehicle to proceed to launch.<\/p>\n
Another issue related to a Freon (coolant) loop in Pad 39A\u2019s Ground Coolant Loop Resevoir Level. However, this is a known condition, as an existing GSE PR (Problem Report) on the freon leak was noted.<\/p>\n
A problem with a chiller pump at the pad was also not going to be a cause any problems for the remainder of the count.<\/p>\n
While Wednesday was originally unavailable due to the Progress launch, NASA had appeared to have used an option to negotiate the extension of STS-127\u2019s window by a day with the Russians, and\/or reduce mission content in order to have a final opportunity available on Thursday \u2013 if approved by the MMT.<\/p>\n
GUCP Status (images to be added shortly):<\/p>\n
One benefit of Sunday\u2019s \u2013 and indeed Monday\u2019s \u2013 scrub was the confirmation the GUCP troubleshooting plan appears to have worked, with no leaks detected throughout the countdown, up to the point of polling to come out of the T-9 minute hold.<\/p>\n
For all 19 NASASpaceflight.com articles on the GUCP, click here: http:\/\/www.nasaspaceflight.com\/tag\/gucp\/<\/p>\n
![\"T1\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T1.jpg\" "\\"T1\\"")
This provided additional confidence \u2013 following the tanking test at the start of the month \u2013 that the engineering work on correcting what was an alignment issue of just 0.357 degrees in the counter-clockwise direction, has been successful.<\/p>\nThe amount of work that went into fixing the issue can be seen in a 47 page presentation to the all-powerful Program Requirements Control Board (PRCB), dated July 7 and acquired by L2.<\/p>\n
\u201cPresent the GUCP GH2 leak fault tree status, IPR (Interim Problem Report) closure (STS-119 and STS-127), and results of root cause assessment including affected materials, process\/procedure\/technique changes, and other associated relevant data. Present results to the PRCB,\u201d opened the presentation.<\/p>\n
\u201cThe objective of the overview \u2013 to identify the configuration that allows us to proceed to a launch attempt with very high confidence of success.\u201d<\/p>\n
Engineers were tasked with checking historical issues with the hardware, in order to attempt a root cause analysis of not only ET-131\u2019s leak during STS-127\u2019s opening two countdowns, but the leak on the opening launch attempt of STS-119 with ET-127.<\/p>\n
![\"T5\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T5.jpg\" "\\"T5\\"")
They were also asked to present the worst case outcome of the potential scenarios surrounding a problem with the GUCP hardware.<\/p>\n\u201cIdentified 21 scenarios using inputs from community, new fault tree, timelines. Collected evidence to support\/refute each scenario,\u201d added the presentation. \u201c11 scenarios are fully (4) or partially (7) mitigated by the actions taken. Evidence reviewed by team ruled out 10 scenarios.<\/p>\n
\u201cWorst case effect\/risk vary with individual scenario: Could result in an improper function of the vent line (leakage of flammable hydrogen external to the ET), resulting in a launch scrub.<\/p>\n
\u201cPremature release of GUCA (Ground Umbilical Carrier Assembly) resulting in improper vent line operation or inability to perform functions (nominal or on-pad abort configuration). Improper release \/ binding after pyro bolt separation.\u201d<\/p>\n
Following an extensive review, engineers confirmed the misalignment was to blame. However, the a flight seal issue \u2013 since replaced with a \u201cmore forgiving\u201d two-part seal \u2013 may have also contributed.<\/p>\n
![\"T2\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T2.jpg\" "\\"T2\\"")
\u201cRoot cause: plate misalignment resulted in gapping at flight seal\/bellows probe interface. Contributors: As-built flight hardware misalignment ETCA & hinge pin brackets. Insufficient controls during assembly to account for off-nominal ET geometry.<\/p>\n\u201cMeasurements, Alignment pins, Flight\/ground plate relative motion (lateral) during assembly. Reduced capability to accommodate motion at interface during operations due to stiffer Inconel bellows.<\/p>\n
\u201cUnexplained Anomaly, possible contributors include: Flight seal defects and\/or damage during assembly. Potential plate misalignment.\u201d<\/p>\n
The solution, which included replacement of the aforementioned seal, involved new feet being installed on the GUCP, to avoid misalignment potential out at the pad.<\/p>\n
\u201cLeak mitigation: Tighter tolerance alignment pins (0.515\u201d). Tailored GUCP feet (0.180\u201d & 0.230\u201d offset). analysis shows adequate strength. Hinge pin washers restrain GUCP lateral motion,\u201d the presentation noted, which was backed up by the data gained via ET-131\u2019s tanking test.<\/p>\n
\u201c2-piece flight seal has greater resiliency and provides additional capability for misalignment. 2-piece seal tested to 0.050\u201d. Concentricity and other measurements during assembly show minimal motion of GUCP. Successful tanking test (50 ppm GH2). Note -successful tanking has never been followed by a leak resulting in a scrub. Tanking test observations show minimal motion of GUCP feet.\u201d<\/p>\n
The modifications noted will now be implemented on ET-132 (for STS-128) and all downstream tanks that are yet to arrive at the Kennedy Space Center (KSC) from their manufacturing base \u2013 the Michoud Assembly Facility (MAF) in New Orleans.<\/p>\n
\u201cProcessing plan for ET-132 & subs. Apply ET-131 lessons learned. Assembly using tighter tolerance guide pins. Install 2-piece flight seal. Install washers on hinge pins. Increased measurements during assembly.\u201d<\/p>\n
![\"T4\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T4.jpg\" "\\"T4\\"")
Although this forward plan included flight rationale to the Mission Management Team (MMT) for STS-127\u2019s tanking and launch, the investigation will continue, given the findings do not provide a clear root cause for STS-119\/ET-127\u2019s leak.<\/p>\nThis will include further work at the test facility at the Marshall Space Flight Center (MSFC).<\/p>\n
\u201cWorking theory supported by measurements. Hydrogen leak occurred between flight seal and ground QD (Quick Disconnect). Unique ET-131 umbilical geometry was a contributor to the leak,\u201d the investigation noted.<\/p>\n
\u201cMitigations implemented for ET-131: Fabricated new GUCP feet \u201ctailored\u201d to ET-131 geometry. Utilized tighter tolerance guide pins during assembly. Installed hinge pin washers to limit lateral motion. Installed 2-piece flight seal.<\/p>\n
\u201cET-131 mitigations do not invalidate certification or hazard controls. Continue investigation to determine the sensitivity of this interface to off-nominal geometry for future tanks, other contributing factors, and finalize long-term changes to preclude leaks.<\/p>\n
\u201cLack of root cause for STS-119 and partially mitigated failures scenarios demonstrate some residual leak risk still exists. Recommend MMT action closure.\u201d<\/p>\n
![\"T3\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/07\/T3.jpg\" "\\"T3\\"")
However, images of ET-127\u2019s flight seal \u2013 which was replaced with a similar spare for STS-119 \u2013 shows the leak was likely caused by a faulty seal, with several anomalies observed on its edges.<\/p>\n\u201cET-127 Flight Seal Findings: Multiple dents, gouges, scratches and flattened areas were noted around circumference of seal face and edge. Abnormal gouge patterns observed in between 6:00 -7:00,\u201d the presentation outlined.<\/p>\n
\u201cSeal edge inspections showed that the compression band formed on the seal edge by bellows probe contact was sporadically inconsistent around the entire circumference of the seal. Areas of wide, rolled, jagged, thin & wavy contact were all observed.<\/p>\n
\u201cDents and gouges were also evident around the entire circumference of the seal edge.\u201d<\/p>\n
Given ET-131\u2019s first flight seal only suffered from a few rolled edges \u2013 likely caused by the misalignment \u2013 ET-127\u2019s leak is probably related to a specific fault with its flight seal, which in turn adds confidence ET-131\u2019s issue was mainly via the now-solved misalignment problem.<\/p>\n
For live updates of launch attempt 5 \u2013 refer to the live update pages, linked above.<\/p>\n
L2 members<\/em><\/em>: 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":"
Shuttle orbiter Endeavour was again ready to launch to the International Space Station. However, poor weather again put pay to the fifth launch attempt for STS-127, moving launch to Wednesday. Meanwhile, the results of the Ground Umbilical Carrier Plate (GUCP) investigation appear to have been validated via Sunday\u2019s leak-free \u201cnear-complete duration\u201d tanking. STS-127 Fifth Attempt Scrub: With […]<\/p>\n","protected":false},"author":1,"featured_media":29955,"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":[9122,9038],"class_list":["post-41051","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-gucp","tag-sts-127"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41051"}],"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=41051"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41051\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/29955"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41051"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41051"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41051"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}