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 The June 28 accident, which destroyed a load of cargo destined for
the International Space Station, was the third botched resupply run
within eight months. An Orbital ATK rocket explosion claimed a
Cygnus cargo ship in October and a Russian Progress freighter failed
to reach orbit in April.
SpaceX founder and Chief Executive Musk said Falcon rocket flights
will not resume until September at the earliest. The company also
plans to delay the debut flight of its heavy-lift Falcon rocket from
this year to spring 2016.
A defective brace, or strut, holding a bottle of helium in the
Falcon 9 needed to pressurize the upper-stage engine’s liquid oxygen
tank, was the most likely cause of last month's accident, Musk said.
He said the strut, from a vendor he declined to identify, was built
from steel certified to withstand 10,000 pounds (4,536 kg) of force
but apparently failed at 2,000 pounds (907 kg) of force, Musk said.
 “It looks like the key strut that holds down one of the helium
bottles failed. As a result, the helium bottle would have shot to
the top of the tank at high speed,” Musk told reporters on a
conference call.
"It failed five times below its nominal strength, which is pretty
crazy,” he said.
SpaceX not only intends to buy new struts, most likely from a
different vendor, but test each one prior to installation in the
rocket’s tanks, Musk said.
SpaceX had successfully flown its Falcon 9 rocket 18 times since its
debut in 2010 before the June 28 failure. During those flights,
thousands of similar struts apparently worked with no issues.
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“We have been able to replicate the failure by taking a huge sample,
essentially thousands of these struts, and pulling them. 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,” Musk
said.
The results are preliminary, he added.
In addition to the bad strut, SpaceX is looking for other issues
that may have caused or 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.
The company has a backlog of more than 50 rocket launches, worth
about $5 billion, for commercial companies, NASA and other agencies.
(Reporting by Irene Klotz; Editing by Tom Brown)
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