SpaceShipOne assembly at fault

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Scaled Composites' X-Prize contender SpaceShipOne did not reach its intended altitude on its first space voyage on 21 June because it was assembled incorrectly, says Dick Rutan, brother of the vehicle's designer Burt Rutan.

The rocket motor was not installed on the centreline of the vehicle and the resulting thrust asymmetry caused the vehicle to start rolling 45-90û to the left about 7s after rocket ignition, between 48,000ft (14,600m) and 53,000ft.

Pilot Michael Melvill used the rudder to counter the roll moment, but this early trajectory deviation cost the vehicle 31,500ft of altitude. Instead of reaching 360,000ft it only reached 328,500ft.

"It was thrust asymmetry, the rocket was off centre, so it needed trim to work. When SpaceShipOne was bolted together [the rocket motor] was off centre a little bit," says Dick Rutan. Another problem was the distortion of the carbonfibre engine nozzle fairing during re-entry. Burt Rutan says energy radiating from the nozzle "softened the fairing", adding it was "an oversight on my part".

ROB COPPINGER / LONDON