A defective brace inside the upper stage of SpaceX’s Falcon 9 rocket was the probable cause of the post lift-off explosion that took place last month, destroying the Dragon capsule carrying supplies to the International Space Station.
SpaceX announced results of the initial assessment on Monday, concluding that the supportive brace, or strut, that holds in place a bottle of helium used to pressurise the liquid oxygen tank of the upper-stage engine broke about 138 seconds into the flight.
"As a result, the helium bottle would have shot to the top of the tank at high speed," SpaceX CEO Elon Musk said.
"It failed five times below its nominal strength, which is pretty crazy."
According to Musk, the failed piece of equipment was successfully flown on all previous Falcon 9 flights without any problems and had been tested to withstand 4,500kg (10,000lb) of force.
SpaceX said it will discontinue the use of the component and find a different supplier. Moreover, from now on, SpaceX will be testing each strut before installation into the rocket tank.
"We have been able to replicate the failure by taking a huge sample, essentially thousands of these struts, and pulling them,” Musk said. “We found a few that failed far below their certificated level. That's what led us to think that there was one just far below its rated capability that happened to be at the wrong place at the wrong time."
The accident, the third lost supply mission to the space station in only eight months, has grounded the SpaceX fleet with flights not expected to resume until September.
Some rather costly Nasa equipment was lost during the accident including the International Docking Adapter – a new docking port, which was supposed to be installed at the space station ahead of the arrival of Nasa’s new private space taxis.
The explosion will also delay the debut flight of SpaceX’s new Falcon Heavy rocket. Originally planned for late 2015, the flight will not take place before spring 2016, SpaceX said.
SpaceX is looking into further issues that may have contributed to the accident, as well as any potential problems that could affect future flights.
"This is the first time we've had a failure in seven years, so I think to some degree the company as a whole became maybe a little bit complacent," Musk said.
In April this year a Russian space capsule was lost on the way to the space station due to a failure during separation from the launcher. In October last year, a rocket of SpaceX’s American rival Orbital Sciences exploded in a ball of fire virtually seconds after lift-off.