Ariane 5 self destructs dramatically

[GroupJW]

I have thought of this being shown to all of you. It's an Ariane 5 exploding. I added alternate subtitles to see on what is happening on this maiden flight of the launcher. The audio is from "Sky Captain and the World of Tomorrow" to make it dramatic to all of you.

 

Edited May 15, 2023 by GroupJW

[Gargamel]

Nice.    

Moved to.... ah heck... Science and Spaceflight. 

[sevenperforce]

One of the most expensive software errors in history.

The Ariane 5 re-used the code from the Ariane 4, which had a particular 16-bit variable set to represent the vehicle's pitch. Unfortunately, the Ariane 5's updated code used a 64-bit measurement for increased precision and they forgot to remove that part of the Ariane 4 code.

Initially, the 64-bit measurement converted quite readily into the 16-bit variable, but at 37 seconds into flight the 16-bit variable overflowed, defaulting to a diagnostic value intended for pad checkouts. This sent a signal to the engines that the rocket was still perfectly vertical on the pad, and all three sets of engine gimbal actuators immediately tried to push the rocket "back" to its correct downrange pitch. Of course this just made the rocket pitch down toward the ground and aerodynamic forces ripped the stack apart 2 seconds later.

[mikegarrison]

https://en.wikipedia.org/wiki/Cluster_(spacecraft)

They were not even using this code. On the Ariane 4 it was used on the ground and in flight. On the Ariane 5 it was only used on the ground, but it was still running in flight.

The code was supposed to shut itself off 40 seconds into the flight. On the Ariane 4, this would happen long before the bits were filled up. Because the Ariane 5 was able to accelerate faster than the Ariane 4, it filled those bits faster. This happened 39 seconds into the flight.

Edited March 11, 2021 by mikegarrison

[GroupJW]

5 hours ago, sevenperforce said:

One of the most expensive software errors in history.

The Ariane 5 re-used the code from the Ariane 4, which had a particular 16-bit variable set to represent the vehicle's pitch. Unfortunately, the Ariane 5's updated code used a 64-bit measurement for increased precision and they forgot to remove that part of the Ariane 4 code.

Initially, the 64-bit measurement converted quite readily into the 16-bit variable, but at 37 seconds into flight the 16-bit variable overflowed, defaulting to a diagnostic value intended for pad checkouts. This sent a signal to the engines that the rocket was still perfectly vertical on the pad, and all three sets of engine gimbal actuators immediately tried to push the rocket "back" to its correct downrange pitch. Of course this just made the rocket pitch down toward the ground and aerodynamic forces ripped the stack apart 2 seconds later.

Well, that's somehow a simplified version of what went wrong on the flight. The audio from "Sky Captain and the World of Tomorrow" that you're hearing now is from the end, when Sky Captain and Polly managed to release the Ark's animal cargo in floating escape pods and then paralyzing the Ark's computer in mid-flight, preventing the second-stage booster engines from igniting, therfore rupturing the fuel lines,  the fire resulting from this igniting the second stage (presumably at cookoff point) and destroying the Ark.  Yep. This is where the similiarites meet. Ariane 5 self destructs mid-flight, and the Ark from the movie gets destroyed in mid-flight due to a design flaw.

2 hours ago, mikegarrison said:

https://en.wikipedia.org/wiki/Cluster_(spacecraft)

They were not even using this code. On the Ariane 4 it was used on the ground and in flight. On the Ariane 5 it was only used on the ground, but it was still running in flight.

It was a 16-bit signed integer, in which the highest bit of the binary number is used for the sign. 0 is positive, and 1 is negative. When the other 15 bits filled up, the computer just flipped the next bit, but that made it a negative number....

The code was supposed to shut itself off 40 seconds into the flight. On the Ariane 4, this would happen long before the 15 bits were filled up. Because the Ariane 5 was able to accelerate faster than the Ariane 4, it filled those bits faster. This happened 39 seconds into the flight.

You're absolutely right about that!

Edited March 12, 2021 by GroupJW
Fixed typo.