Ground Truth
Tagged code-reuse
2 pieces
- · 6 min read
Every Reused Module Is Untested Until You Run It Against the New Envelope
A reused module carries a correctness argument scoped to its old environment. Ariane 5 lost a launcher to a conversion that was safe within Ariane 4's velocity range, and the Therac-25 killed three people reusing code whose assumption about hardware interlocks was no longer true.
- · 7 min read
Ariane 5: The Code Worked in Every Demo and Destroyed the Rocket
The inertial reference module was reused unchanged from Ariane 4 and had a flawless demonstration record. Ariane 5 produced horizontal velocity values roughly five times larger, a conversion to a 16 bit signed integer exceeded 32,767, and the launcher was destroyed 37 seconds after liftoff.