A faulty metal strut is the most likely candidate for causing the SpaceX cargo ship explosion that occurred on June 28. The announcement came from the SpaceX CEO, Elon Musk. 

Musk added, in his first public comments on the explosion, that the steel bar "would appear to be incorrectly made but with no visible way of determining that from the outside."

The CRS-7 rocket was in trouble when the metal strut failed to hold a helium canister in place. The strut was just over half a meter (2 feet) in length and only 2.5 centimeters (1 inch) wide at its thinnest point. The strut broke under the stress of a force that was only one-fifth of the value that it was certified to withstand. 

Musk declined to disclose which external supplier had provided the part, although he did say that the strut was "not something that should ever have failed at this force level."

Musk looked to the future and explained how the company would use this as a learning experience. The SpaceX policy will be updated to independently test struts in the future to ensure that future rockets don't fall foul to a weak strut. The added cost to future space missions is predicted to be minimal, especially since the cost of these tests would be dwarfed by the cost of replacing an entire, failed rocket.

It's eye opening to witness how one strut can make or break a space mission. It demonstrates the need for space vessels to be perfect to have any chance of leaving the atmosphere. Elon Musk commented on the difficulties of creating space-worthy rockets. "The fundamental nature of rocketry is that it is a case where the passing grade is 100%, every time," he said. "From the moment of lift-off, it's 100% or nothing."

The unmanned SpaceX cargo ship was supposed to deliver supplies to the International Space Station (ISS). It carried supplies such as a water filtration system, a new spacesuit and a new docking port designed for commercial crew capsules. All of these, plus many more supplies, were destroyed when the rocket exploded.

You can see the footage of the explosion in the video below.

^{The SpaceX CRS-7 launch and explosion.} 

After the explosion occurred, Musk broadcasted the following tweet. 

Falcon 9 experienced a problem shortly before first stage shutdown. Will provide more info as soon as we review the data.

— Elon Musk (@elonmusk) June 28, 2015

It's great to see Musk make good on his promises. Hopefully, the company can pick itself up after this error. The next launch, a Falcon 9 rocket carrying a satellite that will measure ocean depths, was scheduled for August 8. However, this has been postponed as a result of the failed ISS resupply mission.

[H/T: Nature]