3 ms·

I've told the story to my students many times (probably mangling some minor details over the years, but getting the point across). AFAIK (correct me if wrong).

I've told the story to my students many times (probably mangling some minor details over the years, but getting the point across). AFAIK (correct me if wrong)... - The code was re-used from the Ariane 4, which was designed for launch only in the northern hemisphere. The Ariane 5 was launched from south of the equator, hence the importance of unsigned vs signed. - A run-time warning was generated. Problem was where to put the warning, which wasn't specified, and which thru dangling pointer overwrote current position/velocity data. Watchdog code noticed the now-impossible trajectory, decided the system was very very confused, and initiated self-destruct for (relative) safety.

InclinedPlane 14y ago
Both Ariane 4 and Ariane 5 launch from the same facility (in Kourou, Guyana, almost right on the equator (5.2 deg. N latitude)). The specific problem was that the Ariane 5 had more horizontal motion than the Ariane 4. Within the code there was a conversion of a 64-bit float to a 16-bit signed integer, which overflowed on the Ariane 5 flight causing the inertial measurement unit to start spewing out diagnostic information which the flight control software merrily interpreted as data and drove the vehicle off course.
- HeyLaughingBoy 14y ago
  Nitpick. Kourou is in French Guiana (Cayenne), not Guyana. They are different countries. Similarity in name is due because three neighboring colonies used to be called "the Guianas." French, British and Dutch. British Guiana became independent in 1966 and changed its name to Guyana. Minor, and rather pedantic, detail, but seeing the place you were born being constantly mischaracterized is a bit irritating after a while :-)