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With SSME (Space Shuttle Main Engine) final preps\/TSM (Tail Servicing Mast) securing now complete, along with vehicle pressurization tasks, preparations were completed for the retraction of the RSS \u2013 which began at 10:30am local time on Friday.<\/p>\n
Other key milestones on Friday and Saturday include: LO2\/LH2 tanking of Endeavour\u2019s External Tank (ET-131), scheduled for 2152 EDT (underway), followed by the Terminal Countdown at 03:22 EDT Saturday morning. The STS-127 Crew will ingress Endeavour at 03:57 EDT, ahead of T-0 at 7:17am.<\/p>\n
UPDATE: Ahead of the retraction of the RSS, engineers walked around the structure to check for any items of interest. Two \u201cdebris\u201d related observations were made, though both have been cleared as no issue for Saturday\u2019s launch.<\/p>\n
\u201cDuring Walkdown for RSS Roll, debris was noticed on both the ET Cross Beam and the LOX side vertical strut,\u201d noted one problem report, via L2\u2019s live coverage, before adding: \u201cDuring Walkdown for RSS Roll, possible metallic (reflective) sliver approx 1\/16\u201d on top\/forward of the LOX T-0 Plate Seal.<\/p>\n
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\u201cDebris is inaccessible RSS or no. ICE Team has determined debris is no constraint to RSS roll or Launch and will be dispo\u2019d as such.\u201d<\/p>\n
Debris investigation T-0 Umbilical Plate:<\/p>\n
Debris, or more specifically, ice on the T-0 plate was also at the center of the SE&I Flight Readiness Review (FRR) presentations, with the department calling for a Tiger Team \u2013 the name for the high level investigation team \u2013 to look into the liberation threat from the T-0 umbilical hardware over the coming launches.<\/p>\n
Ice on the T-0 umbilical hardware is not uncommon, but following the observation of ice liberating from Endeavour during STS-126\u2019s ascent, and ice spotted on the plate as STS-125\/Atlantis left the pad, a greater understanding is now required for the remaining shuttle flights, as part of the Shuttle Program\u2019s ongoing threat mitigation process.<\/p>\n
The T-0 umbilical \u2013 located on each side of the orbiter \u2013 is mated to the orbiter via retractable plates in the Tail Service Masts (TSMs), which can be seen either side of the orbiter\u2019s aft. These umbilicals are retracted at SRB (Solid Rocket Booster) ignition.<\/p>\n
During STS-126, at approximately 26.7 seconds, debris was observed to liberate between the LH2 T-0 umbilical and port OMS pod. However, it did not impact the vehicle.<\/p>\n
![\"a41\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/06\/a41.jpg\" "\\"a41\\"")
Ahead of STS-119\u2019s launch with Discovery, United Space Alliance (USA) engineers worked on a \u201crain\/water diverter\u201d modification, which was added to the TSMs as a form of extra protection from one of the determined drivers of ice formation on the T-0 umbilical area.<\/p>\nA release agent \u2013 which would ease the release of any ice during the first few seconds of ascent \u2013 was also mentioned, but never confirmed as being certified for inclusion.<\/p>\n
\u201cSTS-126: most likely cause was a gap in the T-0 plate seal. STS-126 anomaly (large ice loss internal to purge barrier seal) was not repeated on STS-119,\u201d noted the SE&I Agency FRR presentation, available to download on L2.<\/p>\n
Due to the lack of observed ice on STS-119\u2019s launch, it is likely the STS-126 event was solely caused by the compromised T-0 plate seal. However, the STS-125 observation may require a re-think \u2013 or at least an investigation into surrounding areas of the plate.<\/p>\n
![\"a25\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/06\/a25.jpg\" "\\"a25\\"")
\u201cDuring STS-125 Launch, Final Inspection Team photos of the LH2 T-0 Umbilical revealed the presence of ice outside the T-0 Umbilical plate seal. The T-0 ice seen on STS-125 was not in the same family as that seen on STS-126,\u201d noted SE&I.<\/p>\n\u201c1) External Ice seen in FIT images and waivered for STS-125. 2) Indication of Ice under the T-0 Umbilical Plate \u2013 Not visible until T-0 Retraction. 3) Indication of Ice under the T-0 Umbilical Plate \u2013 Not visible until T-0 Retraction.\u201d<\/p>\n
As noted, the problem facing the Tiger Team relates to being able to observe the ice prior to lift off, which is impossible with the plate obscuring the mated plate and umbilicals.<\/p>\n
Ice is only spotted on the plate via engineering cameras placed inside the TSMs on what is known as the QuVIS video \u2013 collated via an array of cameras, most of which are never publicly aired on NASA TV\u2019s launch replay feed (several QuVIS videos available on L2, click here for SSME ignition video sample).<\/p>\n
However, ice outside of the mated plate may give indications of a potential threat, with SE&I working on \u2018allowable\u2019 mass observations, which in turn will be fed back to the Mission Management Team and Launch Director for what is called a \u201cDay-Of-Launch (DOL)\u201d decision.<\/p>\n
Options open to the launch director range from scrubbing to the more likely scenario of issuing a waiver to allow for the launch to proceed.<\/p>\n
![\"a33\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/06\/a33.jpg\" "\\"a33\\"")
It would take a serious ice build-up to become a concern for an orbiter impact, with computational models showing ice liberating from that area of the vehicle would not impact key orbiter hardware, such as the OMS Pods\/Engines and\/or Space Shuttle Main Engines (SSMEs).<\/p>\n\u201cSE&I debris team is working with Orbiter Project to develop T-0 Umbilical allowables for external ice to support future Day-of-Launch (DOL) decisions. Masses up to 0.5 lbm will be considered for characterization of external ice risk. STS-125 Waiver based on 12\u201dx1\/2\u201dx1\/4\u201d external ice (estimated 0.042lbm).\u201d<\/p>\n
\u201cOrbiter is developing capability models for the aft region. No debris transport to OMS nozzles or SSME nozzles. Plan to update requirements with T-0 Ice allowables after STS-127. SE&I has also chartered a Tiger Team to look at T-0 umbilical ice mitigation.\u201d<\/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":"
The ascent threat of ice liberation, as observed on STS-126 and potentially STS-125, will be closely monitored during Endeavour\u2019s launch \u2013 which has been delayed by a scrub \u2013 following an expansive overview by NASA\u2019s Space Shuttle Systems Engineering and Integration Office (SE&I) to the Flight Readiness Reviews (FRRs). STS-127 S0007 (Launch Countdown) Latest: UPDATE: SCRUB due to […]<\/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":[9122,9038,9218],"class_list":["post-41077","post","type-post","status-publish","format-standard","hentry","category-news","tag-gucp","tag-sts-127","tag-tsm"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41077"}],"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=41077"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41077\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41077"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41077"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41077"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}