Rocket explosion inquiry

The European Space Agency's Ariane-5 rocket exploded on its maiden flight on Tuesday because of a failure of electronic communication between the guidance system and the on-board computer, according to ESA officials, writes Tom Wilkie.

Daniel Mugnier, launch operations director at Kourou in French Guiana, said that 37 seconds into the mission the onboard computer apparently started to believe - wrongly - that the rocket was veering off course and therefore issued a command to the rocket motors.

The control system swivelled the nozzles of the rocket engines so violently that they hit the end-stops; the rocket turned over and the stresses broke off the upper part, triggering automatic self-destruction.

In Britain, scientists were putting a brave face on the damage to their research programmes following the loss of the four-satellite Cluster payload carried on Ariane-5. At ESA headquarters, the focus was moving to the contractors and the pre-flight tests. The agency's inquiry is due to make its first report by 15 July. Launch-pad prospects, page 21