The spectacular on-pad explosion of a SpaceX Falcon 9 rocket during a pre-launch test Sept. 1 was triggered by a sudden catastrophic breach in a helium pressurization system inside the booster’s second-stage liquid oxygen tank, the company said Friday.
While no details were provided, the company said a data review and “fault tree” analysis showed the unspecified problem was not related to the internal strut failure that released a second stage helium pressurization bottle during a June 28, 2015, launch. The buoyant helium bottle shot to the top of the oxygen tank, causing the second stage to break apart, destroying the rocket and a space station-bound cargo ship.
While the second stage helium system was involved in the Sept. 1 explosion, a different failure mode apparently was involved.
“At this stage of the investigation, preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place,” SpaceX said in a statement.
“All plausible causes are being tracked in an extensive fault tree and carefully investigated. Through the fault tree and data review process, we have exonerated any connection with last year’s … mishap.”
SpaceX was readying the Falcon 9 for launch Sept. 3 to boost an Israeli communications satellite into orbit. In a routine pre-launch test, the rocket was mounted on the launch pad and loaded with super-cooled liquid oxygen and kerosene propellants for a planned first-stage main engine test firing on Sept. 1.
SpaceX test fires the nine Merlin 1D engines for several seconds before every launch to make sure propulsion and other critical launch systems are operating properly before committing a booster to flight. As always, the launch complex was evacuated before the test.
The engine firing was planned for 9:15 a.m. EDT (GMT-4). But at 9:07 a.m., the second stage exploded, triggering a spectacular conflagration that destroyed the $62 million rocket and its $195 million satellite payload in a huge fireball of burning propellant. No one was injured.
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SOURCE: CBS News, William Harwood