In Reliability Engineering, we study Cascading Failures, but typically do not have a good example. This is because Cascading Failures are extremely rare.
They can also be very spectacular.
If you observe the explosion of the Spacex rocket, and you know what you are looking at, you can count 100 failures that occurred.
This is a grand example of a CASCADING Failure. This is where one failure causes other failures. In certain cases, one failure can cause another failure, then another, then another.The way you can tell if it is a cascading failure is the BOOM BOOM BOOM BOOM.
In some cases, a small failure can result in major damage.
An example might be where a small electrical fire or electrical short can cause loss of the vehicle. In Engineering Design, we will ensure that a small failure will not lead to loss of vehicle.
This is called a Catastrophic Failure. We define Catastrophic as “Loss of Vehicle”.
We also define catastrophic as “Loss of Mission”, where the failure causes the whole mission to fail.
When we get away from the hardware, we will also define a Catastrophic Failure as one where someone is killed. In Engineering Design, we are very adamant about making sure no one dies. Actually, we then get very adamant about someone getting injured. Although some people may not consider an injury to be catastrophic, it may become more important if the injury occurs to YOU.
So, in the SpaceX explosion, the first thing we learned was that no one was killed or injured.
There was obviously loss of vehicle, which defines the explosion to be Catastrophic. There was obviously loss of the Satellite, which leads to loss of mission, which is also catastrophic.
But most important, the explosion did not stop, it just kept on going and going. There was a bright flash somewhere by the interface between the rocket and the payload module.
If we look at 1:09, we will see that the payload module has an umbilical connected to the module. Somewhere down the top of the umbilical, about 6 feet, we MIGHT see where the explosion began.
The explosion requires a source of ignition, as well as a source for fuel.
The initial explosion was horrific. And it did not stop.
I did not see a water cannon firing water onto the rocket, like Von Braun had at Peenemunde when he had HIS terrific explosion of HIS V2 Rocket. He obviously had expected a giant explosion, and when it happened, he was ready for it.
Later about 1:23, the module with the satellite inside it fell, and it still had about six feet of the umbilical connected to it. Now, when a rocket flies up into the air, the umbilicals all disconnect from the rocket. When a rocket begins its flight, it is not connected to the umbilicals, because they might hold the rocket down, or cause it to stray from its trajectory. But it looks like the umbilical connected to the payload module did not separate, and the umbilical fell while still connected to the payload module.
Which leads to another concept, that there was perhaps an electrical short where the support structure connected to the umbilical. This would give us the source of the ignition.
Why could this happen? In Engineering Design, we always have someone assigned to one module. That person is an expert on HIS module. But not an expert on the other person’s module. The problem becomes the responsibility of another person, referred to as the Interface Engineer. We often do not have another person assigned to the interfaces, because it is extremely complicated because you need to know how each of the modules work, rather than just one.
That is why many failures occur at the interfaces.
But, the explosions just kept on occurring, which is VERY unusual.
We might notice that after the initial explosion, there were fires.
So, what was causing the fires? The fires just kept on burning, and then there were more explosions. Boom – boom – boom – boom.
It seems that the explosions and fires kept on going until all of the fuel was burned up.
Recommendation: The satellite was within the confines of the Payload Module. Maybe they should have invented an enclosure which would have protected the satellite in case there was an anomaly. We often have an Engineering Drop-Test, which requires the satellite to be protected in case there is a problem.
Summary: This was probably the most impressive explosion of a rocket in history. If we try, we can count one failure after another happening. Boom – boom – boom – boom.
Thanks to Gizmodo