{"id":39947,"date":"2012-12-21T22:32:27","date_gmt":"2012-12-21T14:32:27","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/shuttle-scrubber-sls-working-to-avoid-gucp-leaks\/"},"modified":"2012-12-21T22:32:27","modified_gmt":"2012-12-21T14:32:27","slug":"shuttle-scrubber-sls-working-to-avoid-gucp-leaks","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/shuttle-scrubber-sls-working-to-avoid-gucp-leaks\/","title":{"rendered":"Shuttle Scrubber: SLS working to avoid GUCP leaks"},"content":{"rendered":"<p>With a deep heritage between the Shuttle\u2019s External Tank and the Space Launch System (SLS) Core Stage, a NASA team recently evaluated recommendations to mitigate against leaks of the Ground Umbilical Carrier Plate (GUCP) \u2013 the cause of launch day delays for three Space Shuttle missions \u2013 on the monster rocket.\n<\/p>\n<p>The GUCP:<\/p>\n<p>The GUCP is a critical element of hardware, located at the end of the gaseous hydrogen vent arm. Attached to the External Tank, a plate holds a large-diameter pipe that collects excess hydrogen gas from the tank as it\u2019s being filled with liquid hydrogen on launch day.<\/p>\n<p>The venting system funnels it to a larger pipe that takes it down the fixed service structure and out to a flare stack that burns the excess hydrogen off safely. At liftoff, the GUCP retracts away from the tank, cutting off the connection.<\/p>\n<h4 class=\"widget-title penci-border-arrow\">See Also<\/h4>\n<ul>\n<li>SLS Forum Section<\/li>\n<li>L2 SLS Section<\/li>\n<li>L2 GUCP Special Section<\/li>\n<li>Click here to Join L2<\/li>\n<\/ul>\n<p>Due to the importance of the GUCP\u2019s connection to the tank ahead of lift-off, the hardware has sensors in place to watch for hydrogen leaking from the point of tanking operations, through to launch.<\/p>\n<p>These readings are closely monitored by the team in the Launch Control Center (LCC) Firing Room, with any readings outside the limits resulting in the Launch Director, the NASA Test Directors (NTDs) and Mission Management Team (MMT) making a decision based around Launch Commit Criteria \u2013 often resulting in a scrub for the day and the detanking of the ET.<\/p>\n<p>Click here for the list of GUCP-related articles: http:\/\/www.nasaspaceflight.com\/tag\/gucp\/<\/p>\n<p>This was the scenario that impacted three missions in the post-RTF era.<\/p>\n<p>Space tourism guides<path d=\"M7.59009 18.59L9.00009 20L17.0001 12L9.00009 4L7.59009 5.41L14.1701 12\" style=\"animation: initial !important; background: initial !important; border: 0px !important; box-shadow: none !important; color: inherit !important; cursor: inherit !important; direction: inherit !important; display: inline !important; fill: currentcolor !important; filter: initial !important; float: none !important; margin: 0px !important; opacity: initial !important; outline: 0px !important; overflow: initial !important; padding: 0px !important; stroke: initial !important; transform: initial !important; vertical-align: initial !important; visibility: inherit !important;\"><\/path>NASA mission patches<path d=\"M7.59009 18.59L9.00009 20L17.0001 12L9.00009 4L7.59009 5.41L14.1701 12\" style=\"animation: initial !important; background: initial !important; border: 0px !important; box-shadow: none !important; color: inherit !important; cursor: inherit !important; direction: inherit !important; display: inline !important; fill: currentcolor !important; filter: initial !important; float: none !important; margin: 0px !important; opacity: initial !important; outline: 0px !important; overflow: initial !important; padding: 0px !important; stroke: initial !important; transform: initial !important; vertical-align: initial !important; visibility: inherit !important;\"><\/path>Space Technology<path d=\"M7.59009 18.59L9.00009 20L17.0001 12L9.00009 4L7.59009 5.41L14.1701 12\" style=\"animation: initial !important; background: initial !important; border: 0px !important; box-shadow: none !important; color: inherit !important; cursor: inherit !important; direction: inherit !important; display: inline !important; fill: currentcolor !important; filter: initial !important; float: none !important; margin: 0px !important; opacity: initial !important; outline: 0px !important; overflow: initial !important; padding: 0px !important; stroke: initial !important; transform: initial !important; vertical-align: initial !important; visibility: inherit !important;\"><\/path>\n<p>     (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n<p>GUCP History \u2013 STS-119 (All \u201cL2-tagged\u201d materials can be found in the L2 GUCP Section):<\/p>\n<p>The first leak put an end to Discovery\u2019s opening launch attempt on STS-119 back in March 2009, using ET-127. The leak was observed at the point of the actual transition into topping, as the ET was almost full to its brim.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignleft\" title=\"STS-119 Leak Graph - from L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/a312.jpg\" alt=\"STS-119 Leak Graph - from L2\" width=\"295\" height=\"191\">With readings alerted to the Booster console inside the LCC, the leak rate appeared to decrease when the vent valve was closed. This led to an initial effort to troubleshoot via the procedure of cycling the valve to clear any potential ice in the hardware, but this effort failed to stop the leak.<\/p>\n<p>\u201cSTS-119 \/ ET-127: Pre-launch: 1st loading resulted in scrub\/LCC violation due to GH2 leakage at Ground Umbilical Carrier Assembly (&gt;40,000 ppm). Leakage occurred during transition from fast fill to topping. Vent valve opened when 98 percent level sensor indicated wet. Detected by leak detectors (LD 23 &amp; 25) located in ground umbilical shroud,\u201d documentation noted at the time (L2). \u201cIsolates leak to either ground side quick disconnect (QD) or interface with flight seal.\u201d<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-127 Repair Work\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A141.jpg\" alt=\"STS-127 Repair Work\" width=\"335\" height=\"242\">Once engineers accessed the GUCP, no obvious cause of the leak was found. The decision was made to changeout the seal, along with a focus on the retorquing of the hardware.<\/p>\n<p>Engineering notes at the time pointed to a potential problem with the \u201cleft and right pivot seat\u201d, which wasn\u2019t fully connecting to the ET\u2019s pin receptacle sleeve at the bottom of the GUCP.<\/p>\n<p>\u201cThere was some damage to the flight seal, but we\u2019re not sure that\u2019s the cause,\u201d noted launch director Mike Leinbach in review of the STS-119 troubleshooting. \u201cThere was a bit of discoloration on the QD (Quick Disconnect), but that might have been to the hydrogen flowing where it shouldn\u2019t have been.\u201d<\/p>\n<p>With a new seal and the \u201ctightening\u201d of the hardware completed, STS-119\u2019s second tanking was conducted without issue and no leak detectors tripped.<\/p>\n<p>As a result, managers could be forgiven for thinking the issue was a one-off, solved by the replacement of the flight seal and the re-alignment of the pivot seats.<\/p>\n<p>Click here for STS-119 news articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-119\/<\/p>\n<p>As is typical for NASA, an investigation was still conducted into the STS-119 scrub, which noted that out of the previous 31 loadings only one leak was observed (and only at 13,500 ppm). The investigation also noted the potential for issues with the flight seal being part of the root cause, along with the misalignment on the pivot seats \u2013 resulting in the hardware being \u201cpulled\u201d down and to the left.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-127 Flight Seal via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A51.jpg\" alt=\"STS-127 Flight Seal via L2\" width=\"335\" height=\"260\">\u201cMost probable cause identified as momentary breach in flexible flight-seal to bellows probe due to \u2018thermal shock\u2019 of GH2\/LH2 with vent valve in open position. Significant Disassembly Observations: Lower left pad was hard against skin,\u201d noted the findings (L2).<\/p>\n<p>\u201cOther locations were not touching (0.014 \u2013 0.030 gap \/ 0.001 requirement) indicating a pull downward and to the left. Peripheral seal compressed more on left side and toward bottom of GUCP. Left side pivot assembly in hard contact with pivot pin (pin would not rotate). Stain observed on external surface of bellows guard and peripheral seal at 6 o\u2019clock position. Flight-side seal asymmetrically compressed at 3, 7 and 8 o\u2019clock positions.\u201d<\/p>\n<p>Changes were then implemented to ensure the alignment issue wouldn\u2019t reoccur, with additional focus placed on both the installation of the GUCP hardware and observations of any movement once the stack was out at the pad. STS-119 launched without any further issues.<\/p>\n<p>With the next mission, STS-125, avoiding any leaks during tanking, STS-119\u2019s GUCP-related scrub continued to appear as a one-off issue, with additional confidence in future tankings gained by the aforementioned mitigation procedures. However, STS-127 would see the problem return.<\/p>\n<p>GUCP History \u2013 STS-127:<\/p>\n<p>Interestingly, STS-127\u2019s GUCP issues began before Endeavour had even rolled out to the pad with ET-131, with documentation showing work to install the hardware on the tank \u2013 carried out inside the Vehicle Assembly Building (VAB) \u2013 had been problematic, ultimately requiring a changeout of the GUCP and a redesign to its installation hardware.<\/p>\n<p>\u201cInterference between GUCA (Ground Umbilical Carrier Assembly) and ET-131 right hand hinge support observed during mate GUCP (Ground Umbilical Carrier Plate) installation in VAB,\u201d noted STS-127 SSP (Space Shuttle Program) FRR (Flight Readiness Review) documentation (L2).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A101.jpg\" alt=\"GUCP Investigation Slide via L2\" width=\"334\" height=\"250\">Such an interference is not permitted at the hinge location due to the fact that there is potential to induce un-intended loading on the pyro-bolt assembly \u2013 which could affect that separation mechanism at T-0. In order to correct the interference, the GUCP was removed and a different unit was installed. However, after this was accomplished, the interference remained.<\/p>\n<p>Visual and Laser inspections revealed the slight misalignment between the centerline of the plate and the hinge bracket, leading to a modification to the pivot assembly, which was successfully installed by \u201clocally machining outboard surface (0.1\u201d removed) to create the required gap (0.03\u201d gap provided),\u201d according to the FRR documentation.<\/p>\n<p>How much relation those changes had to the subsequent leak during STS-127\u2019s tanking remained unknown.<\/p>\n<p>The first tanking of STS-127 registered a leak at the same time as STS-119\u2019s detection, leading to the scrub and call to dismantle the GUCP hardware once the tank was inert.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 Flight Seal via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A62.jpg\" alt=\"STS-131 Flight Seal vs L2\" width=\"335\" height=\"230\">Once the vent arm was removed and engineers removed the flight seal, observations pointed to a potential root cause via small gaps on the right hand side of the seal.<\/p>\n<p>It was also thought the tank\u2019s GUCP may have suffered from being mated and then unmated at Pad 39B, before being mated once more at Pad 39A, as Endeavour switched rolls from being STS-125\u2019s Launch On Need (LON) vehicle (STS-400) to her primary role with STS-127 \u2013 requiring the pad switch.<\/p>\n<p>This was a potential candidate for being part of the root cause because the seal is a hard teflon ring with no resiliency, and thus presents a sharp corner edged to a smooth tapered metal probe. Any bump, dent or mis-alignment of the probe during installation could result in a leak caused by damage to the teflon edge on the seal.<\/p>\n<p>\u201cGH2 vent seal inspection results: rolled edge around entire circumference with worst case from 4 to 10 o\u2019clock position,\u201d noted one log report on the status of the old seal at the time of troubleshooting (L2). \u201cNo inclusions and no scratches observed.\u201d<\/p>\n<p>Click here for STS-127 news articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-127\/<\/p>\n<p>With the seal replaced, it was hoped that STS-127 would enjoy a smooth tanking at the second attempt, similar to STS-119 once the GUCP seal was changed-out. Unfortunately, the June 16, 2009 tanking once again registering a leak.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"GUCP Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/a47.jpg\" alt=\"GUCP Slide vs L2\" width=\"335\" height=\"188\">The leak was observed 25 minutes prior to topping and appeared to increase at the end of fast fill operations, with the leak detectors observing the peak leak rate of 60,000 ppm.<\/p>\n<p>\u201cThis time the leak started during fast fill which is a signature we\u2019ve never seen before (relating to the difference between the previous leaks, observed as the tank loading process moved from fast fill to topping\/stable replenish of the LH2). During fast fill we leaked to approx. 15,000 ppm,\u201d noted the STS-127 attempt 2 scrub outline on L2.<\/p>\n<p>\u201cOnce we reached replenish, we violated the LCC like we\u2019ve typically seen in the past. Leak eventually trended upward to 60,000 ppm.\u201d<\/p>\n<p>Initial theories pointed to several candidates as the root cause, such as unique thermal conditions associated with the hardware, notably the dynamics of the cryo temperatures that may be interacting with the hardware\u2019s hinge brackets, resulting in a misalignment during tanking.<\/p>\n<p>Also under evaluation were potential software issues, and even possible issues with the leak detectors that registered the leak during tanking \u2013 as much as the latter was ruled out as a specific reason for the scrub, due to the \u201cvisible\u201d observation of venting from the tank.<\/p>\n<p>Another investigation path pointed to the External Tank hardware itself, as opposed to the Ground Support Equipment (GSE) of the GUCP QD, as the reason for the specific leak issues observed with STS-119 and STS-127\u2019s tanks.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A131.jpg\" alt=\"STS-131 GUCP Investigation Slide via L2\" width=\"338\" height=\"230\">However, the key area of interest is related to the two mounts, or feet, located on the tank where the GUCP hinge points attach. One of these mounts (right) was deemed to be offset from&nbsp;its preferred location.<\/p>\n<p>\u201cHave many folks across Agency supporting GUCP investigation. Appears to be going well. Appreciate folks at KSC showing us the hardware there. It looks like the ETCA plate that mounts (manually installed) to the ET is not properly aligned with the ET,\u201d noted an Engineering overview presented via a Shuttle Standup meeting (L2) at the time.<\/p>\n<p>\u201cThere are a couple of feet, below where the GUCP rotates off during separation, which are not mounted exactly correctly relative to the ETCA. When the GUCP is put on, there are forces between the pyro bolt, the large QD and the seat. If the alignment is not correct on the ET, the seat may be shifted as everything is tightened.\u201d<\/p>\n<p>This problem was also found on six other tanks set to fly, although the misalignment on ET-131 was classed as \u201cthe worst\u201d.<\/p>\n<p>\u201cTwo adjustments were made to get additional clearance to allow centering and alignment, but after both attempts, the feet and brackets were found way over to the right side and we were not able to align properly,\u201d added notes, again pointing to a problem being suffered at the actual time the tank transitioned into a cryogenic state.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A71.jpg\" alt=\"STS-131 GUCP Investigation Slide via L2\" width=\"336\" height=\"237\">With the second scrub resulting in a several week standdown, NASA\u2019s engineering teams were put into full investigation mode, resulting in a hugely impressive mitigation drive involving several centers.<\/p>\n<p>Test articles were put to use \u2013 such as the GUCP rig at the Marshall Space Flight Center (MSFC) \u2013 working on the main candidate that a misalignment was causing the leaks, along with a drive to use a new two part flight seal, one which would be more forgiving to small misalignments, and hopefully mitigate unacceptable leak levels.<\/p>\n<p>The two part seal also allows the tank to \u201cburp\u201d \u2013 without the need for vent valve cycling \u2013 which had previously cleared a minor leak on a previous loading earlier in the program.<\/p>\n<p>The two part seal had only been installed in two previous tanks ahead of the problems with STS-119 and STS-127, one of which leaked, but was successfully mitigated via the \u201cburp\u201d, allowing the launch to proceed.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A111.jpg\" alt=\"STS-131 GUCP Investigation Slide via L2\" width=\"333\" height=\"221\">A tanking test in June 2009 was called for, testing out the changes and allowing for additional data to be gained \u2013 via strain gauges on the feet of the GUCP hardware \u2013 during the loading of the cryogenic propellants, with the ultimate aim of conducting a successful test and allowance to proceed with STS-127\u2019s launch.<\/p>\n<p>\u201cThe engineering teams, after much analysis of the measurement data between the 2nd scrub disassembly and the 1st scrub disassembly, have high confidence that misalignment is the issue,\u201d noted documentation ahead of the tanking test (L2).<\/p>\n<p>In order to mitigate misalignments, a redesign to the \u201cfitted feet\u201d on the GUCP was implemented on to STS-127\u2019s tank. This design \u2013 along with the two part seal \u2013 was implemented into all future tanks that were under construction at the Michoud Assembly Facility (MAF).<\/p>\n<p>The tanking test proved to be a success with no leaks detected, allowing for Endeavour to proceed towards another launch attempt, which also suffered from no leaks during tanking. Ironically, Endeavour was delayed by weather constraints and took a total of six attempts to finally launch on her mission to the International Space Station (ISS). No further leaks were observed on her tankings after the tanking test success.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A121.jpg\" alt=\"STS-131 GUCP Investigation Slide via L2\" width=\"336\" height=\"253\">The successes provided additional confidence that the engineering work on correcting and mitigating what was then confirmed to be an alignment issue of just 0.357 degrees in the counter-clockwise direction, has been successful.<\/p>\n<p>The amount of work that went into fixing the issue was listed in a 47 page presentation to the all-powerful Program Requirements Control Board (PRCB), dated July 7, 2009 and acquired by L2 at the time.<\/p>\n<p>The presentation provided what was claimed at the time to be the closure of the GUCP leak IPRs ahead of STS-127\u2019s successful launch, a path that appeared to be confirmation the problem was behind them.<\/p>\n<p>\u201cPresent the GUCP GH2 leak fault tree status, IPR 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 prefaced the presentation.<\/p>\n<p>\u201cIdentified 21 scenarios using inputs from community, new fault tree, timelines. Collected evidence to support\/refute each scenario. 11 scenarios are fully (4) or partially (7) mitigated by the actions taken. Evidence reviewed by team ruled out 10 scenarios.\u201d<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" title=\"STS-131 GUCP Investigation Slide via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/11\/A9.jpg\" alt=\"STS-131 GUCP Investigation Slide via L2\" width=\"342\" height=\"203\">Following an extensive review, engineers confirmed the misalignment was to blame. However, the a flight seal issue \u2013 since replaced with the \u201cmore forgiving\u201d two-part seal \u2013 may have also contributed.<\/p>\n<p>\u201cRoot cause: plate misalignment resulted in gapping at flight seal\/bellows probe interface. Contributors: As-built flight hardware misalignment ETCA &amp; hinge pin brackets. Insufficient controls during assembly to account for off-nominal ET geometry,\u201d the presentation noted.<\/p>\n<p>\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. Unexplained Anomaly, possible contributors include: Flight seal defects and\/or damage during assembly. Potential plate misalignment.<\/p>\n<p>\u201cLeak mitigation: Tighter tolerance alignment pins (0.515\u201d). Tailored GUCP feet (0.180\u201d &amp; 0.230\u201d offset). analysis shows adequate strength. Hinge pin washers restrain GUCP lateral motion. 2-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. Tanking test observations show minimal motion of GUCP feet.\u201d<\/p>\n<p>However, the PRCB investigation into the STS-119 and STS-127 leaks admit that \u201cA lack of root cause for STS-119 and partially mitigated failures scenarios demonstrate some residual leak risk still exists,\u201d but \u201crecommended MMT action closure\u201d.<\/p>\n<p>GUCP History \u2013 STS-133:<\/p>\n<p>STS-133\u2019s ET-137 proved to be a rather troublesome tank, following a double issue during its loading on launch day.<\/p>\n<p>Discovery saw her final mission delayed, following the recording of IPR-68 (Interim Problem Report) during the countdown, when leak detectors at the pad observed the gaseous hydrogen leak from the GUCP.<\/p>\n<p>All had been proceeding to plan \u2013 with the tank \u201cfast filled\u201d during tanking, with no issues recorded with either the loading process, or the Low Level\/Engine Cut Off (ECO) sensors via their customary SIM checks \u2013 until the first leak indication was revealed.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-27443\" title=\"a8\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/a8.jpg\" alt=\"\" width=\"321\" height=\"194\" srcset=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/a8.jpg 321w, https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/a8-180x110.jpg 180w\" sizes=\"(max-width: 321px) 100vw, 321px\">Firstly, a 33,000 ppm leak \u2013 below the 40-44,000 ppm (HAZ-09 limit in the Launch Commit Criteria \u2013 LCC) \u2013 was recorded, before reducing to a level below 20,000 ppm. The leak was only being observed during the cycling of the vent valve to \u201copen\u201d \u2013 to release the gaseous hydrogen from the tank and through the vent arm plumbing to the flare stack, as designed.<\/p>\n<p>With controllers deciding to stop the cycling of the valve \u2013 in order to increase the pressure and attempt to force a seal \u2013 before attempting to complete the fast fill process and transition into \u201ctopping\u201d, the leak spiked and pegged at the highest 60,000 ppm level, indicating a serious problem with the GUCP\u2019s seal.<\/p>\n<p>With cycling of the valve resumed \u2013 as part of the troubleshooting efforts to clear any potential obstructions such as ice from the hardware \u2013 and no resolution forthcoming, a scrub was the only outcome.<\/p>\n<p>Click here for STS-133 news articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-133\/<\/p>\n<p>\u201cPegged leak detectors at topping. Violation. Scrubbed for today. Configuring for drain,\u201d flashed the confirmation (L2), as controllers moved into emptying the External Tank, leading to the ECO sensors registering \u201cdry\u201d at 13:53 local time.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-27444\" title=\"The Stringer Crack IR image via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/A4521.jpg\" alt=\"The Stringer Crack IR Image via L2\" width=\"335\" height=\"270\">However, after the scrub was called, cameras at the pad picked up another serious problem, with cracks observed on the foam surrounding ET-137\u2019s LO2\/Intertank flange stringers.<\/p>\n<p>It took around a day for the tank to become inert, allowing engineers to prepare towards disconnecting the vent arm and the large amount of lines and ordnance on the hardware, prior to taking their first look at the potentially suspect seal and any potential alignment issues \u2013 the two leading candidates for the leak.<\/p>\n<p>At the same time, meetings were conducted to assess the reason for the crack, later found to be caused by the stringers themselves becoming cracked underneath the foam.<\/p>\n<p>Ultimately, a huge amount of work was carried out, both to investigate the root cause of the cracks \u2013 found to be via a \u201cmottled\u201d batch of stringers at MAF, leading to a rollback and the installation of radius blocks to strengthen the local structure.<\/p>\n<p>While this work was completed, engineers were called to \u201cclock\u201d the GUCP\u2019s placement on the tank \u2013 and a new two-part flight seal installed. The team were provided with \u201cfree\u201d test of the GUCP via a Tanking Test, called for to aid the investigation into the stringer cracks. The test showed the GUCP did not leak at any point during the tanking, adding confidence to the mitigation procedure.<\/p>\n<p>With STS-133 launching successfully, the last two missions of the Space Shuttle Program did not suffer from any issues, either with the ET\u2019s stringers or GUCP.<\/p>\n<p>GUCP \u2013 SLS:<\/p>\n<p>NASA managers often speak of \u201clesson\u2019s learned\u201d \u2013 the ability to draw on their vast experience in the rocket business, aided by their database of mitigation procedures. A shining example of this process was highlighted in a presentation that reviewed the aforementioned incidents with the GUCP and its relation to SLS.<\/p>\n<p>Relating to how SLS will have commonality with ET hardware \u2013 given the SLS core is Shuttle-like ET, bar obvious changes due to the in-line design of the HLV \u2013 the experiences of the Shuttle Program are notably apt.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-27440\" title=\"SLS &quot;GUCP&quot; Connection via L2\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/Z12.jpg\" alt=\"SLS &quot;GUCP&quot; Connection via L2\" width=\"349\" height=\"255\">However, there will be differences between the Shuttle and SLS hardware, specific to what was the GUCP on the ET. Firstly, the ongoing design process has moved further away from a direct match with the Shuttle ET GUCP, instead opting for a Core Stage Inter-Tank Umbilical (CSITU).<\/p>\n<p>According to the Ground Systems Development and Operations presentation (available on L2), \u201cFinal cost and schedule impacts to \u2026 baseline for change from ET Vent Line reuse to new swing arm umbilical\u201d are pending final approval.<\/p>\n<p>The new design will provide commodity services to the SLS\u2019s Core Stage Inter-tank region. The umbilical arm will be 45 feet in length, 8 feet in width, and 15 feet in height.<\/p>\n<p>An added benefit will come via the umbilical and ground carrier plates being mated in the VAB \u2013 due to no pad access for umbilical mating \u2013 allowing them to remain connected to the vehicle until liftoff. This will help avoid any problems that can occur with mating the hardware at the pad.<\/p>\n<p>For previous SLS Articles, click here:&nbsp;http:\/\/www.nasaspaceflight.com\/tag\/hlv\/<\/p>\n<p>The umbilical plate size is now expected to be 34 inches x 54 inches, although it will still consist of a seal at its heart as the protective element against scrub-causing leaks.<\/p>\n<p>This is where a team effort \u2013 between NASA Engineering (NE) and Team QNA Engineering personnel \u2013 is working towards a goal of providing support for the Umbilical Systems Development project, which is funded by Advanced Exploration Systems (AES) and 21st Century Launch Complex.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-27442\" title=\"New Tool\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/12\/Z772.jpg\" alt=\"New Tool\" width=\"351\" height=\"229\">Reviewing the Shuttle issues with the GUCP, and consulting with the SLS team for their recommendations, an associated presentation noted that several \u201clesson\u2019s learned\u201d will be implemented for the HLV.<\/p>\n<p>These recommendations included the development of a concentricity tool, to help alignment during assembly of flight side components. The use of Parallelism Retainer Clips, Ground Support Equipment bolts and clips that will maintain parallelism at the seal face during assembly of QD to launch vehicle. And the use of a Self-Aligning Probe, to accurately guide and centre the QD and the tank vent as they are brought together during the integration flow.<\/p>\n<p>They also reviewed the old two piece seal designs, proposing three new alternative seal designs \u2013 to be down-selected after more detailed tests\/analysis.<\/p>\n<p>The end result of these early evaluations will hopefully avoid launch fans having to head back home after a launch day scrub caused by the detection of unacceptable levels of leaking gaseous hydrogen from a small vent on the side of the vehicle.<\/p>\n<p>(Images: Via L2 content from L2\u2019s GUCP section and L2\u2019s SLS specific L2 section, which includes, presentations, videos, graphics and internal \u2013 interactive with actual SLS engineers \u2013 updates on the SLS and HLV, available on no other site. Other image via NASA)<\/p>\n<p>(L2 is \u2013 as it has been for the past several years \u2013 providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http:\/\/www.nasaspaceflight.com\/l2\/)<\/p>\n","protected":false},"excerpt":{"rendered":"<p>With a deep heritage between the Shuttle\u2019s External Tank and the Space Launch System (SLS) Core Stage, a NASA team recently evaluated recommendations to mitigate against leaks of the Ground Umbilical Carrier Plate (GUCP) \u2013 the cause of launch day delays for three Space Shuttle missions \u2013 on the monster rocket. The GUCP: The GUCP [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":30363,"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":[9021,9122,9034,624,9123,9038,9051],"class_list":["post-39947","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-et","tag-gucp","tag-hlv","tag-sls","tag-sts-119","tag-sts-127","tag-sts-133"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39947"}],"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=39947"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39947\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/30363"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=39947"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=39947"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=39947"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}