{"id":40563,"date":"2010-12-31T17:27:41","date_gmt":"2010-12-31T09:27:41","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/sts-133-managers-to-decide-on-et-137-stringer-modifications-next-week\/"},"modified":"2010-12-31T17:27:41","modified_gmt":"2010-12-31T09:27:41","slug":"sts-133-managers-to-decide-on-et-137-stringer-modifications-next-week","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/sts-133-managers-to-decide-on-et-137-stringer-modifications-next-week\/","title":{"rendered":"STS-133: Managers to decide on ET-137 stringer modifications next week"},"content":{"rendered":"<p>Following a Space Shuttle Program (SSP) meeting on Thursday, a decision on carrying out modifications to STS-133\u2019s External Tank (ET-137) won\u2019t be made until next week, as engineers inside the Vehicle Assembly Building (VAB) carry out repairs to a number of additional cracks, found during Non Destructive Evaluation (NDE) scans of the intertank flanges.<\/p>\n<p>ET-137 Latest:<\/p>\n<p>Since arriving back in the VAB, Discovery\u2019s tank has received X Ray and Backscatter scans of the entire circumference of the two flanges on the upper and lower areas of the intertank, a task which could not be completed out at the pad due to access constraints.<\/p>\n<p>The scans were called for as part of the root cause and flight rationale discussions following the observation of four cracks on the LOX\/LO2 Intertank flange, which caused a large crack to form in the flange\u2019s foam during the scrubbed tanking attempt back in November.<\/p>\n<h4 class=\"widget-title penci-border-arrow\">See Also<\/h4>\n<ul>\n<li>STS-133 LIVE UPDATES<\/li>\n<li>L2 STS-133 Special Section<\/li>\n<li>Click here to Join L2<\/li>\n<\/ul>\n<p>The four cracks were found on the S6 and S7 stringers \u2013 an area which faces the orbiter\u2019s critical Thermal Protection System (TPS), thus a concern from a foam liberation standpoint. The new cracks are located on the opposite side of the tank, and will undergo the same repair procedure that was carried out at the pad on the original cracks.<\/p>\n<p>This repair, which will involve foam removal, followed by the installation of doublers, should result in the tank being confirmed as defect-free, although a decision is yet to be taken on whether to carry out additional work via the installation of a modification to a number of the stringers.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignleft size-full wp-image-17397\" title=\"A3\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/12\/A311.jpg\" alt=\"\" width=\"326\" height=\"293\">\u201cThe other decision that still needs to be made is if they intend to perform any additional modifications to the tank,\u201d noted a memo ahead of the meeting (L2). \u201cThere are three proposals on the table: 1) fly with no additional modifications to the tank, 2) adding what are called \u201cradius blocks\u201d or 3) adding \u201cradius blocks with Z straps\u201d on the stringers.<\/p>\n<p>\u201cThere is also an open question if they want to do these mods on 18 or 36 or all the stringers. Even if the modifications are required (at least the 18 or 36 stringer modifications), there is a plan that will allow us to make the Feb 3 window.\u201d<\/p>\n<p>Should managers decide to carry out modifications to the tank, the \u201cradius blocks\u201d modification will be similar to the doubler installations conducted on the S6\/S7 stringers. The modification options were down-selected as a preference due to their history of flying without issue on numerous External Tanks over the history of the Program.<\/p>\n<p>\u201cDesign Enhancement Overview: Two options developed to mitigate potential contributors: Radius blocks only. Radius blocks with Z stringer reinforcements (straps),\u201d noted a Program Requirements Control Board (PRCB) presentation, available on L2.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-17398\" title=\"A4\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/12\/A415.jpg\" alt=\"\" width=\"331\" height=\"247\">\u201cBasis for Selection: Both concepts previously flown and within experience base. Similar to repairs already implemented at S6 and S7. Radius blocks mitigate contributors (i.e. defects, residual stress) by increasing local bending stiffness of feet. Initial stringer pull tests complete and consistent with expectations.<\/p>\n<p>\u201cReinforcements provide \u2018fail safe\u2019 feature to protect for unlikely failure in stringer sidewall. Relatively basic tasks required to remove and re-install hardware. TPS Repair and Replace well within experience.\u201d<\/p>\n<p>Once the foam has been removed from the stringer area, engineers will leave the first row of fasteners in place to mitigate clearance issues with the fasteners which need to be removed (the next six rows). The holes on the stringer will then be \u201creamed\u201d to accommodate the larger hole size required for installation blind fasteners (A286 Huck).<\/p>\n<p>With the stringer area ready to receive the radius block, the installation would mirror the doubler work, prior to visual inspections the modification is firmly seated in place.<\/p>\n<p>STS-133 Specific Articles (click for numerous background content on the ET and&nbsp;relating to this article): http:\/\/www.nasaspaceflight.com\/tag\/sts-133\/<\/p>\n<p>\u201cRadius Block and Stringer Reinforcement Designs Used Extensively on ET. Used where point loads require local reinforcing and \/ or to prevent fastener installation encroaching on corner radii,\u201d noted the presentation\u2019s background on the modification hardware. \u201cMiscellaneous brackets \/ clips used to reinforce structure locally (localized loading\/around penetrations).\u201d<\/p>\n<p>However, the tank is deemed to be in a \u201cstrong\u201d configuration, based on Tanking Test data \u2013 which also showed the S6 and S7 doublers performed as advertised \u2013 possibly allowing managers to press ahead with flying the tank \u201cas is\u201d once the doublers have been installed in the area of the latest cracks.<\/p>\n<p>Managers are expected to determine the forward path for the tank as early as Monday.<\/p>\n<p>(Lead Image via KSC\/NASA.gov. Images within the article via L2 presentations).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Following a Space Shuttle Program (SSP) meeting on Thursday, a decision on carrying out modifications to STS-133\u2019s External Tank (ET-137) won\u2019t be made until next week, as engineers inside the Vehicle Assembly Building (VAB) carry out repairs to a number of additional cracks, found during Non Destructive Evaluation (NDE) scans of the intertank flanges. ET-137 [&hellip;]<\/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":[9021,9051],"class_list":["post-40563","post","type-post","status-publish","format-standard","hentry","category-news","tag-et","tag-sts-133"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40563"}],"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=40563"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40563\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40563"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40563"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40563"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}