During the (otherwise successful) second test flight of the new Ariane 5 rocket, the main (second) stage began to rotate soon after booster separation. At the end of the main stage flight, the roll rate had reached almost six revolutions per minute. The cause for the unexpected rotation was a torque of 900 Nm [Newton metre.]

Such a torque is not unusual; but before the test flight it had been estimated at less than 300 Nm. The attitude control system of the main stage would have been able to compensate for that. It couldn't cope with the threefold value that actually occurred, which caused the main engine to shut down some 10 or 20 seconds too soon.

Among several solutions to counter the roll torque it was decided to install a second attitude control system on the Ariane 5 launcher. The new unit, installed on the lower part of the vehicle equipment bay, is able to counteract a roll torque up to 2000 Nm.

• Ariane 5 ECA (2002-12-11)
• Ariane 5 G (2001-07-12)
• Ariane 5 G (1996-06-04)

Launch Failures Chronology