Other Disasters Disasters
The disastrous launch cost approximately $370m, led to a public inquiry, and through the destruction of the rocket’s payload, delayed scientific research into workings of the Earth’s magnetosphere for almost 4 years. The Ariane 5 launch is widely acknowledged as one of the most expensive software failures in history. More details
On June 4th, 1996, the very first Ariane 5 rocket ignited its engines and began speeding away from the coast of French Guiana. 37 seconds later, the rocket flipped 90 degrees in the wrong direction, and less than two seconds later, aerodynamic forces ripped the boosters apart from the main stage at a height of 4km. This caused the self-destruct mechanism to trigger, and the spacecraft was consumed in a gigantic fireball of liquid hydrogen.
A report from the United States General Accounting Office begins On February 25, 1991, a Patriot missile defense system operating at Dhahran, Saudi Arabia, during Operation Desert Storm failed to track and intercept an incoming Scud. This Scud subsequently hit an Army barracks, killing 28 Americans. More details can be found in the following reference:
Patriot missile defense: Software problems led to system failure at Dhahran, Saudi Arabia. Report GAO/IMTEC-92-26, Information Management and Technology Division, US General Accounting Office, Washington DC, Feb. 11992, 16 pp.
The report finds that the failure to track the Scud missile was caused by a precision problem in the software.
The computer used to control the Patriot missile is based on a 1970s design and uses 24-bit arithmetic. The Patriot system tracks its target by measuring the time it takes for radar pulses to bounce back from them. Time is recorded by the system clock in tenths of a second, but is stored as an integer. To enable tracking calculations the time is converted to a 24-bit floating point number. Rounding errors in the time conversions cause shifts in the system's ``range gate", which is used to track the target. More details