![\"spacex\"](\"https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2015\/07\/spacex-620x342.png\")
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The unexpected breakdown of a tank strut apparently caused last month\u2019s failure of a Falcon 9 rocket launch to the International Space Station, SpaceX CEO Elon Musk reported Monday.<\/p>\n The June 28 loss of the Falcon, plus SpaceX\u2019s robotic Dragon capsule and more than two and a half tons of cargo, will set back the company\u2019s launch schedule by at least a few months and is likely to result in hundreds of millions of lost revenue, Musk told reporters.<\/p>\n SpaceX\u2019s workhorse Falcon 9 rocket is grounded pending the conclusion of the company\u2019s investigation and the Federal Aviation Administration\u2019s signoff. Also, the debut of its Falcon Heavy launch vehicle will have to be put off until next spring, Musk said.<\/p>\n He said that the strut assembly would be redesigned and readjusted before the Falcon flies again, and that SpaceX would readjust its attitude as well.<\/p>\n<\/p>\n <\/span> This is the first time we\u2019ve had a failure in seven years, so to some degree the company became complacent<\/span>\u201cThis is the first time we\u2019ve had a failure in seven years, so to some degree the company became complacent,\u201d Musk told reporters. \u201cWhen you\u2019ve only ever seen success, you don\u2019t fear failure quite as much.\u201d<\/p>\n Musk emphasized that the focus on a faulty strut was only a preliminary rather than a definitive determination of the cause, but here\u2019s how he and SpaceX\u2019s investigators think it went down, based on an analysis of data from 3,000 channels of telemetry: One of the steel struts holding down a bottle of helium inside the Falcon\u2019s second-stage liquid-oxygen tank assembly broke loose during the first couple of minutes of flight. The helium is supposed to be released in a controlled fashion to keep the liquid oxygen under stable pressure, and the struts connected to the bottles are supposed to withstand 10,000 pounds of force.<\/p>\n But on June 28, something went wrong when the stress on the struts amounted to only 2,000 pounds. \u201cIt failed at five times below its nominal strength, which is pretty crazy,\u201d Musk said.<\/p>\n![\"Elon](\"https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2015\/01\/muskelon1211-300x203.jpg\")