![\"SpaceX](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/SpaceX-CRS-7-Launch-Side-by-Side.gif\")
However, an overpressure event in the Second Stage 139 seconds after liftoff resulted in the loss of Dragon and the disintegration of the Falcon 9 launch vehicle.<\/p>\nSpaceX CEO and Chief Designer Elon Musk has updated the status of the investigation into the failure of the Falcon 9 rocket during its ill-fated CRS-7 Dragon mission. The preliminary findings point to a support strut in the Second Stage LOX tank breaking, releasing a helium pressurization bottle (Composite Overwrapped Pressure Vessel) that began the series of events that resulted in the loss of the vehicle.<\/p>\n
CRS-7 Failure Latest:<\/p>\n
SpaceX had enjoyed a string of successes since fighting back from the early days of its history.<\/p>\n
After suffering three Falcon 1 failures in succession, the fourth flight provided the company with its first completed mission \u2013 prior to achieving a huge amount of success with its Falcon 9 rocket in 2008.<\/p>\n
The CRS-7 failure, the 19th launch of the Falcon 9, was tasked with loft the seventh Dragon spacecraft on a key resupply mission to the Space Station, with the aim of adding to Falcon 9\u2019s string of successes.<\/p>\n
However, an overpressure event in the Second Stage 139 seconds after liftoff resulted in the loss of Dragon and the disintegration of the Falcon 9 launch vehicle.<\/p>\n
The cause of the failure was not immediately known \u2013 with only a short message shortly after the loss from Mr. Musk providing some information that pointed to the Second Stage of the Falcon 9.<\/p>\n
\u201cThere was an overpressure event in the Second Stage liquid oxygen tank. Data suggests a counterintuitive cause. That\u2019s all we can say with confidence right now. Will have more to say following a thorough fault tree analysis.\u201d<\/p>\n
![\"2015-07-03-223752\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/2015-07-03-223752-350x236.jpg\")
That note placed an immediate focus on the helium pressurization system\u2019s bottles in the Second Stage of the Falcon 9.<\/p>\n
Aerospace industry analysis (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n Composite Overwrapped Pressure Vessels (COPVs) \u2013 as they were named during the Shuttle era \u2013 have been a topic of engineering discussion for SpaceX in the past, with \u201cbad trends\u201d in a number of helium bottles causing a manifest debate relating to the CRS-6\/SpX-6 and TurkmenistanSat missions.<\/p>\n Both missions were launched without issue.<\/p>\n During the blackout of the initial investigation period, SpaceX worked to recover any remaining items of the destroyed Falcon 9 to aid its knowledge base. It is understood that most publicly recognizable pieces of debris that have been found recently were both solar arrays with covers and one landing leg.<\/p>\n (Image left of a COPV support in the First Stage \u2013 which Mr. Musk noted is the same design as those in the Second Stage).<\/p>\n It was suggested that one of these rods \u2013 or struts \u2013 may have failed during ascent.<\/p>\n Such a scenario would have resulted in a loose bottle \u2013 which are classed as \u201cbuoyant\u201d \u2013 impacting with the surrounding inners of the tank.<\/p>\n Mr. Musk confirmed that the failure of a support strut for a helium bottle is the leading theory, aided by ground-based stress testing that resulted in one of the struts failing, leading to metallurgy evaluations showing a weakness in the material.<\/p>\n \u201cIt appears that one of those struts broke free during flight.\u201d<\/p>\n The struts \u2013 which were supplied to SpaceX by a contractor \u2013 are typically used for tank mounting applications and are made up of a shaft with a rod end (containing a spherical bearing) screwed on at one end, and either another rod end or a bracket screwed or welded on at the other end.<\/p>\n The rod end would fit into a bracket on the tank wall, with a nut\/bolt combination running through the bracket and rod end, anchoring the assembly. There appears to be a focus on a bolt in the strut assembly.<\/p>\n Mr. Musk explained that ground testing of such hardware isn\u2019t fully sufficient to mirror the stresses such a strut undergoes during flight.<\/p>\n \u201cIt\u2019s quite unique to rockets that as the stage is accelerating, the buoyancy increases proportionate to the G-loading. It might seem counter-intuitive that as the rocket is accelerating that something in the tank would want to go \u2018up\u2019 more \u2013 but that\u2019s basically what happens.<\/p>\n (Image left: An example of a strut \u2013 not a SpaceX graphic).<\/p>\n With the helium bottle loose \u2013 and likely becoming damaged \u2013 it is believed a large amount of helium would have been released into the LOX tank, resulting in the overpressure event.<\/p>\n It was not immediately obvious the strut was the hardware that had failed, based on flight experience and ground testing, resulting in data on hundreds of struts \u2013 including those that had already flown without issue.<\/p>\n Also, the struts were designed to handle 10,000 lbs of force, per its certification. However, based on the period of when the Falcon 9 failed, it is estimated that the force would have been around 2,000 lbs.<\/p>\n \u201cIt\u2019s proving to be quite a puzzle,\u201d added Mr. Musk.<\/p>\n \u201cThe telemetry data also somewhat confusingly shows a drop in helium pressure \u2013 which you\u2019d expect with a breach in the system \u2013 and then, somewhat strangely, a rise (of pressure) in the system, back to its starting pressure. This is obviously quite confusing.\u201d<\/p>\n The theory revolves around a bottle breaking free, twisting around, resulting in its helium line \u201cpinching\u201d off the helium manifold, which subsequently restored pressure in the helium system. However, it would have still released enough helium into the tank to cause the Second Stage to fail.<\/p>\n The event happened within a quarter of a second, with the overpressure occurring at speed due to the propellant not being used \u2013 given the rocket was still in first stage flight.<\/p>\n The immediate forward plan to return the Falcon 9 to flight is to change the struts inside all future tanks, independently tested to ensure their quality before being used in the rocket.<\/p>\n \u201cWhatever something is certified to handle, we\u2019re not going to believe that. We\u2019re going to test every single strut. We\u2019re going to switch to a strut that has an even higher margin of safety.\u201d<\/p>\n Based on the replacement schedule, Mr. Musk believes the impact to SpaceX\u2019s manifest will only be a matter of months, with the next flight \u2013 with a yet-to-be-decided payload \u2013 expected no sooner than late September.<\/p>\n \u201cBut we want to make sure we\u2019re turned over every piece of data, that we\u2019ve diagnosed the issue correctly, or if any more issues we need to be addressed as well and that all our customers are onboard.\u201d<\/p>\n Further articles will follow.<\/p>\n (Images: via L2\u2019s SpaceX Section, including assets from L2\u2019s CRS-7 Video Analysis Section \u2013 which involves numerous videos techniques and evaluations with thanks to members jdeshetler, bstrong, moralec and Okan170 \u2013 these are not official SpaceX investigation assets. Other images from Keltisch WerWolf, SpaceX and NASA)<\/p>\n (Click here: http:\/\/www.nasaspaceflight.com\/l2\/ \u2013 to view how you can support NSF\u2019s running costs and access the best space flight content on the entire internet)<\/p>\n","protected":false},"excerpt":{"rendered":" SpaceX CEO and Chief Designer Elon Musk has updated the status of the investigation into the failure of the Falcon 9 rocket during its ill-fated CRS-7 Dragon mission. The preliminary findings point to a support strut in the Second Stage LOX tank breaking, releasing a helium pressurization bottle (Composite Overwrapped Pressure Vessel) that began the […]<\/p>\n","protected":false},"author":1,"featured_media":30111,"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":[8026,2304,1395,479,316],"class_list":["post-39289","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-copv","tag-crs","tag-dragon","tag-falcon-9","tag-spacex"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39289"}],"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=39289"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39289\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/30111"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=39289"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=39289"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=39289"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"2015-07-20-152727\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/2015-07-20-152727-350x261.jpg\")
There were also notes (L2) about interest in the rods that support the helium bottles inside the LOX tank in the second stage.<\/p>\n![\"\"](\"http:\/\/oi62.tinypic.com\/2wefhw5.jpg\")
\u201cThe preliminary conclusion is that the failure arose from a strut in the Second Stage LOX tank \u2013 that was holding down one of the COPVs,\u201d noted Mr. Musk during Monday\u2019s media call.<\/p>\nSee Also<\/h4>\n
\n
![\"2015-07-21-000734\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/2015-07-21-000734-350x246.jpg\")
\u201cAt (around) 3.2 Gs, the strut holding down one of the helium bottles appears to have snapped.\u201d<\/p>\n![\"2015-07-21-001007\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/2015-07-21-001007-350x245.jpg\")
SpaceX also examined the CRS-7 Falcon 9\u2019s processing flow, reviewing closeout photos that showed no obvious issues with the struts inside the tank during assembly.<\/p>\n![\"2015-07-21-005155\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2015\/07\/2015-07-21-005155-350x255.jpg\")
\u201cThis is somewhat speculative, but that\u2019s the best explanation we can think of right now,\u201d added Mr. Musk. \u201cA really odd failure mode.\u201d<\/p>\n