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An additional item of interest \u2013 relating to the fleet\u2019s windows on the flight deck \u2013 has resulted in a minor addition to the pad flow, which will take five shifts to complete.<\/p>\n
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As noted in a previous processing report, a concern with the torque strengths on a few of Endeavour\u2019s windows required evaluations across the fleet. As a result, one of Discovery\u2019s windows will require operations to re-torque its fasteners.<\/p>\n
\u201cThe PRCB (Program Requirements Control Board) decided yesterday (Tuesday) to re-torque the Window 3 fasteners,\u201d added processing information. \u201cStructures and TPS (Thermal Protection System) engineering are estimating approximately five shifts of work, which is being targeted prior to S0071.<\/p>\n
\u201cThe team is not anticipating this work to impact any milestones, including S0007, assuming there is no collateral TPS or window damage to evaluate\/repair.\u201d<\/p>\n
Flow Control Valve (FCV) Latest:<\/p>\n
The key topic for STS-119, and the fleet as a whole, remains the requirement to gain flight rationale for the FCVs. A full overview of the main areas of concern\/risk will be published on this site on Thursday, based on content contained within 19 expansive presentations available on L2.<\/p>\n
Click here for NASASpaceflight.com articles on the FCV issue since STS-126.<\/p>\n
Summarizing the state of play, engineers are looking into the root cause of why \u2013 as observed on STS-126 \u2013 a piece of the poppet on the valve managed to liberate.<\/p>\n
The liberation is caused by tiny cracks in the valve, believed to be related to high cycle fatigue, and an acoustic environment which is coupling with the structural mode of the poppet.<\/p>\n
While the entire root cause may not be \u201cfully\u201d understood by the time STS-119 flies, flight rationale will be based on \u201crisk assessment\u201d \u2013 which relates to ensuring a full understanding of potential LOV\/C (Loss Of Vehicle\/Crew) and the \u201cprobability\u201d of such an outcome.<\/p>\n
The main concern is associated with the External Tank venting due to a lack of pressure management during the first 120 seconds of launch (first stage) via a serious FCV failure, would result in the ET catching fire, and LOV\/C. However, the probability of such an incident is classed as a \u201cmean\u201d of 1 in 1,300.<\/p>\n
Shuttles fly all the time with multiple LOV\/C risks. However, they are able to fly due to the low probability associated with the risks of a failure.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/02\/a218.jpg\")
The other main risk associated with a liberation of part of the FCV \u2013 the outcome of the valve debris impacting and causing a breach in the downstream line\/plumbing \u2013 has also resulted in extensive testing.<\/p>\n\u201cExcellent progress has been made since the Agency Flight Readiness Review (FRR) on February 3rd and the Agency Delta FRR is scheduled for 2\/20 with launch NET 2\/27.\u201d summarized the L2 acquired 8th Floor News this week \u2013 which is weekly memo to shuttle managers.<\/p>\n
\u201cThe effort to determine whether there is adequate flight rationale to fly as is for STS-119 has focused on bounding the size of the poppet lip that can liberate, assessing the risks associated with a poppet failure, and investigating whether there is common cause on the GO2 side. Work continues on refining the bounding particle size.<\/p>\n
\u201cThe venting risk is considered low due to the small window of exposure and fracture size required to result in venting during the region of concern. Significant progress has been made with the particle impact testing. Although some negative margins were computed, the testing was based on conservative particle velocities.<\/p>\n
\u201cAdditional analysis is being performed to understand and possibly reduce the conservatism before conclusions can be drawn from the impact testing. Because of the differences between the GO2 and GH2 valve\/poppet design (three of each), the same issue with poppet failure on the GO2 side is not considered credible.<\/p>\n
\u201cThe team is doing a great job approaching this issue in a thorough and methodical manner. Stay patient and remain focused! We\u2019ll get there!\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":"
Shuttle Discovery is back into full launch processing, with the pad flow working to the latest NET (No Earlier Than) launch date target of February 27. The processing \u2013 which can be backed out of in the event of another Flow Control Valve (FCV) related delay \u2013 will also include work on one of Discovery\u2019s windows. […]<\/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":[9191,9123],"class_list":["post-41185","post","type-post","status-publish","format-standard","hentry","category-news","tag-fcv","tag-sts-119"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41185"}],"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=41185"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41185\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41185"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41185"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41185"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}