Why did the first Ariane V rocket crashes ?
Due to bad programming, not a bad computer. And inadequate testing and system control.
ESA Portal - Press Releases - Ariane 501 - Presentation of Inquiry Board report
Quote:
Although the source of the Operand Error has been identified, this in itself did not cause the mission to fail. The
specification of the exception-handling mechanism also contributed to the failure. In the event of any kind of exception, the
system specification stated that: the failure should be indicated on the databus, the failure context should be stored in an
EEPROM memory (which was recovered and read out for Ariane 501), and finally, the SRI processor should be shut down.
It was the decision to cease the processor operation which finally proved fatal. Restart is not feasible since attitude is too
difficult to re-calculate after a processor shutdown; therefore the Inertial Reference System becomes useless. The reason
behind this drastic action lies in the culture within the Ariane programme of only addressing random hardware failures.
From this point of view exception - or error - handling mechanisms are designed for a random hardware failure which can
quite rationally be handled by a backup system.
Although the failure was due to a systematic software design error, mechanisms can be introduced to mitigate this type of
problem.