![\"Shuttle](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2013\/02\/Z57.jpg\" "\\"Shuttle")
This tank had been re-engineered to use Al-2195 and Al-2090 extensively, which were stronger and lighter than the Al alloys on LWT (Al-2219, etc).<\/p>\nWith a recent decision to switch the Space Launch System (SLS) core from aluminum-lithium to non-lithium alloys, NASA has come full circle on a journey that started nearly twenty years ago with the development of Shuttle\u2019s Super Light Weight External Tank (SLWT). The switch is not just about reducing costs, but it will also prove to be more optimal for the stresses that SLS will endure.<\/p>\n<\/p>\n
SLS Core Material:<\/p>\n
In 1998 \u2013 after a challenging four year development program that kick-started NASA\u2019s knowledge about Al-Li alloys \u2013 STS-91 flew the first SLWT.<\/p>\n
This tank had been re-engineered to use Al-2195 and Al-2090 extensively, which were stronger and lighter than the Al alloys on LWT (Al-2219, etc).<\/p>\n
Together with the first use of an orthogrid structure \u2013 on the LH2 tank\u2019s barrel \u2013 this lightened the structure and improved payload, especially to the high-inclination orbit of the International Space Station (ISS).<\/p>\n
However, those new alloys were also more brittle and difficult to weld, and experience showed a maintenance overhead. All of the dome and ogive sections were reverted back to aluminum over three subsequent revisions \u2013 first flown on STS -116, -119, and -130 respectively.<\/p>\n
At the same time, SLWT experience allowed the LH2 orthogrid to be further optimized and lightened from STS-119.<\/p>\n
Space Shuttle models (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n Notably, SLS will move completely away from the stringer design for its intertank, which carries much higher loads supporting a larger LO2 tank, an upper stage, payload and PLF \u2013 all at higher G\u2019s, and with greater aero and bending loads than the ET.<\/p>\n The new design will have integrally machined stiffeners instead of riveted sheet metal stringers.<\/p>\n Similarly, the components which failed during a recent pressure test of the Exploration Flight Test -1 (EFT-1) Orion flight article were also Al-2195.<\/p>\n Launch vehicles need to allow substantial margins to avoid their tanks, intertanks and interstages buckling during launch. Rules for this were set by experiments in the sixties, but the state-of-the-art in analysis and construction has moved on a long way since then.<\/p>\n The engineering team are re-writing the rules for large vehicles via a combination of analysis and experimental verification, leading to a 2011 \u201ccan crush\u201d test where they used a million pounds of force to buckle an \u201cExternal-Tank-like Test Article\u201d, which was 8.4m in diameter and 6.1m tall.<\/p>\n The team has already produced a first draft of their guidelines. In addition, since early 2012, they have been working closely with the SLS team on design of the core.<\/p>\n It is in this light that the SLS program recently reported a wholesale switch from Al-2195 to Al-2219 on the core. This \u201cwas based on a trade study that reduced payload mass by 3 t,\u201d \u2013 taken from project reserves \u2013 \u201cbut that will result in approximately $30 million per flight savings.\u201d<\/p>\n L2 sources confirm that Al-2195\u2019s brittleness was the limiting factor when trying to beef up the structure for SLS.<\/p>\n However, the ET was already using the thickest plate that could survive being formed to the tank\u2019s 8.4m diameter.<\/p>\n Al-2219 is less brittle, so they can use thicker plate which can be reliably formed, and the thicker orthogrid actually results in a lighter structure overall.<\/p>\n Information also notes that the SBKF project has also been doing preliminary work on a new alloy. AL-2050 adds magnesium for an Al-Mg-Li mix, and \u201cis already used extensively in several commercial aircraft\u201d. This promises plates and orthogrids three times thicker than Al-2195 \u2013 up to six inches \u2013 with weight savings of as much as 20-30 percent.<\/p>\n This effort has been spun off into a Small Business Innovation Research project \u201cto investigate material properties and structural design optimization for heavy lift LV cryotanks\u201d.<\/p>\n It is possible that one day this could become the basis of a Super Light Weight upgrade to SLS.<\/p>\n (Images: Via NASA, TerraBuilder, Inc and L2 content from L2\u2032s 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.)<\/p>\n (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":" With a recent decision to switch the Space Launch System (SLS) core from aluminum-lithium to non-lithium alloys, NASA has come full circle on a journey that started nearly twenty years ago with the development of Shuttle\u2019s Super Light Weight External Tank (SLWT). The switch is not just about reducing costs, but it will also prove […]<\/p>\n","protected":false},"author":1,"featured_media":30395,"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":[9021,9034,624],"class_list":["post-39907","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-et","tag-hlv","tag-sls"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39907"}],"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=39907"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39907\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/30395"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=39907"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=39907"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=39907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"First](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2013\/02\/A45211.jpg\" "\\"First")
But the Space Shuttle Program (SSP) wasn\u2019t finished with problems with Al-Li \u2013 the intertank stringers which failed during STS-133 tanking and had to be reinforced, were Al-2090.<\/p>\n![\"SBKF](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2013\/02\/Z410.jpg\" "\\"SBKF")
Meanwhile, a Shell Buckling Knockdown Factors (SBKF) project has been running at NASA Langley since 2007, funded by the SLS Advanced Development Office since Q3 FY12.<\/p>\nSee Also<\/h4>\n
\n
![\"SLS](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2013\/02\/Z710.jpg\" "\\"SLS")
Orthogrids \u2013 or possibly isogrid (as shown in the image to the left) \u2013 on the tank barrel are machined from flat plates, leaving stiffening ribs that ideally are tall (for strength, or more accurately, stiffness), allowing them to be thin (for lightness).<\/p>\n