euesa1-4, Exercise 2: The Ariane 5 failure

Model answer:

On its first flight on 4 June 1996 Ariane 5 veered off course and destroyed itself less than a minute after lift-off, losing the four Cluster satellites it carried. The inquiry found a software fault: a component in the guidance system had been reused from Ariane 4. Ariane 5 was faster and flew a different path, so a number no longer fitted the space set aside for it, causing an error that was not handled safely. The backup unit ran the same code and failed in the same way.

General lesson: reusing code without re-testing it under the new conditions is risky, and a backup running identical software gives no protection against a software fault. Also, errors need safe handling.

Check the cost figure before quoting it.