SpaceX this week revealed the likely cause of a September explosion of its unmanned Falcon 9 rocket.
Elon Musk's private spaceflight company was conducting a routine test at the Cape Canaveral Air Force Station in the fall, when something went wrong, resulting in a blast that rocked the launch site. Now, the firm reveals that one of the three composite overwrapped pressure vessels (COPVs) inside the second-stage liquid oxygen (LOX) tank failed.
"Specifically, the investigation team concluded the failure was likely due to the accumulation of oxygen between the COPV liner and overwrap in a void or a buckle in the liner, leading to ignition and the subsequent failure of the COPV," a Monday SpaceX blog update said.
Each stage of Falcon 9 uses COPVs to store cold helium, used to maintain tank pressure; each COPV consists of an aluminum inner liner with a carbon overwrap. The COPVs recovered from the test site showed buckles in their liners.
According to SpaceX, buckles are unlikely to burst a COPV on their own. But in this case, those distortions allowed LOX to pool under the overwrap, where it became trapped. When pressurized, the super-chilled oxygen generated friction ignition, causing the COPV to fail—and the rocket to explode.
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Now, Musk & Co. are moving forward, with plans to change the COPV configuration and return to flight with the Iridium NEXT launch on Jan. 8.
"SpaceX greatly appreciates the support of our customers and partners throughout this process, and we look forward to fulfilling our manifest in 2017 and beyond," the blog said.
The September blast came a month after SpaceX successfully landed its Falcon 9 rocket for the sixth time. Prior to the explosion, the company's last major setback occurred in June when its rocket exploded after an otherwise-successful mission to launch two communications satellites into orbit. SpaceX made history in April with its first successful landing of the Falcon 9 rocket booster on a platform in the Atlantic Ocean.