Chris Johnson, Index
Ariane 5 Case Study
- Failed to understand system change?
o) In Ariane 4 flights using the same type of inertial reference system there has been no
such failure because the trajectory during the first 40 seconds of flight is such that the
particular variable related to horizontal velocity cannot reach, with an adequate operational
margin, a value beyond the limit present in the software.
p) Ariane 5 has a high initial acceleration and a trajectory which leads to a build-up of
horizontal velocity which is five times more rapid than for Ariane 4. The higher horizontal
velocity of Ariane 5 generated, within the 40-second timeframe, the excessive value
which caused the inertial system computers to cease operation.