Cause Identified for Ariane 5 Launch Abort

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COLORADO SPRINGS, Colo. — The March 30 launch abort of Europe’s Ariane 5 rocket after the main engine had been ignited was caused by one or more components attached to the engine nozzle that prevented the nozzle from moving freely during ignition, the head of the Arianespace launch consortium said April 15.

The suspect components have since been removed, and replacements tested and installed on the Ariane 5 ECA rocket, Jean-Yves Le Gall said in an interview. The launch, to carry Intelsat’s New Dawn and startup operator Yahsat’s Yahsat 1A telecommunications satellites, has been rescheduled for April 22.

The launch abort occurred after the end of the vehicle’s usual automated sequence preceding ignition, a time when the on-board computer verifies that all systems are functioning correctly.

The March 30 countdown proceeded without a hitch, letting go the ignition of the main-stage cryogenic Vulcain engine. Typically that motor then burns for seven seconds, time for a final series of checks by the computer. If all is OK, the order is given to ignite the Ariane 5’s two large strap-on solid-rocket boosters, which provide most of the initial thrust as the vehicle moves through the atmosphere.

Sensing a problem, the computer shut down the engine about midway through this seven-second firing.

“We have not isolated a single probable cause, but several components attached to the [Vulcain] engine and nozzle did not give the nozzle sufficient freedom of movement. The actuators then centered the nozzle,” Le Gall said in an interview. “In this case, the computer found that the nozzle was not moving as it should, and it correctly stopped the ignition.”

It was the first time in Ariane 5’s history that this has happened.