A human-factors expert has been asked to join the investigation of the fatal crash of Virgin Galactic's passenger spacecraft to figure out why the co-pilot unlocked a pivoting tail section of the ship during a test flight prematurely.
The engagement of the tail mechanism, which is designed to slow the vehicle's decent into the atmosphere from space, and the possibility that pilot error was to blame, were announced by National Transportation Safety Board (NTSB) late on Sunday and have emerged as a main "thrust" of the inquiry into Friday's incident.
"We know already from having the lever move from lock to unlock that we need to get a human-factors person in here," said NTSB Chairman Christopher Hart, according to Reuters. "The question then is why did that happen when it happened?"
Hart added that investigators haven't decided yet whether releasing the tail mechanism too early caused or contributed to the crash of the space plane near the Mojave Air and Space Port, about 95 miles north of Los Angeles.
The rocket vehicle, called SpaceShipTwo, broke into pieces over California's Mojave Desert and crashed shortly after its separation from the special jet aircraft that carries it for its high-altitude launches, according to Reuters.
The crash, which took place without SpaceShipTwo catching fire or exploding in flames, came on its fourth powered test flight, the first since January.
Video footage from the cockpit shows co-pilot Michael Alsbury, 39 releasing a lever to unlock the twin-tail section eight seconds after SpaceShipTwo's engine ignited, Hart said to reporters on Monday. Alsbury was killed in the crash.
Just two seconds later the tail, which didn't have sufficient aerodynamic pressure to hold it in place, started to pivot upward, a maneuver created to increase drag for atmospheric re-entry, according to Reuters.
Investigators are also trying to figure out how surviving pilot Pete Siebold, 43, managed to get out of the rocket plane and parachute to the ground from a height of roughly 50,000 feet.
Hart said Siebold, who was hospitalized with a shoulder injury after landing, did not exit through the cockpit's escape hatch.
"We know it wasn't through there, so how did this pilot get out?" Hart said.
Virgin Galactic is the space tourism company of billionaire Richard Branson.
Branson and his son plan to fly on the first commercial flight, according to Reuters. Approximately 800 people already have paid or put down deposits for the ride, which costs $250,000.
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