SpaceShipOne will today attempt to reach an altitude of 100km for the second time in less than a fortnight, and thereby claim the $10m X-Prize for the first private space vehicle to accomplish the feat.

The flight is due to blast off from Mojave, California, later today following its ascent last Wednesday to 102.8km. The first mission proved successful despite the vehicle developing a roll which forced pilot Mike Melvill to stabilise SpaceShipOne using its compressed gas "reaction control system". At high altitudes, lack of atmosphere makes traditional control surfaces virtually ineffective.

Melvill later dismissed the Mach 2.7 incident as a "little victory roll" and is expected to take the controls again today, although this has not been confirmed. Neither has designer Burt Rutan yet announced whether he is to suit up and hop aboard SpaceShipOne for the flight. He is understood to be keen to hitch a ride for the historic event. ®

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