A propos de l'accident du "SpaceShipTwo", il semblerait que le déploiement du système de freinage aérodynamique à un moment inopportun soit à l'origine du crash (l'engin est articulé, et se "plie" au moment de rentrer dans l'atmosphère, pour réduire sa vitesse et se stabiliser).
From the NTSB (National Transportation Safety Board) :
"The vehicle... was dropped from its carrier aircraft, WhiteKnightTwo, at an altitude of almost 50,000ft at 10:07:19 US Pacific time.
The ship’s hybrid rocket motor was then ignited just a couple of seconds later, at 10:07:21.
Eight seconds after that (10:07:29), the vehicle was travelling just under the speed of sound (Mach 0.94). Two further seconds into the flight (10:07:31), it was travelling at Mach 1.02.
It is in that period between Mach 0.94 and Mach 1.02 that Michael Alsbury is seen on recovered cockpit video moving a lever to unlock the feathering system - an action that in the pilots’ checklist was not called for until the vehicle had reached Mach 1.4.
Investigators have previously described how the feathering system then deployed, apparently "uncommanded" by the pilots. It is probable that aerodynamic forces deployed the mechanism, resulting in the break-up of the ship. This is timed at 10:07:34 - the instant at which video and telemetry were lost.
One line of inquiry will be to ascertain whether the pilots were getting the correct information on their cockpit display throughout this critical period."