The investigation into last week's deadly crash of the Virgin Galactic spaceship has found that the "feathering" function to help it descend into the atmosphere from space was deployed early, the National Transportation Safety Board said on Sunday.
SpaceShipTwo's rotating tail boom, a key safety feature for re-entering the atmosphere, inadvertently rotated early, said Christopher Hart, the acting chairman of the NTSB.
The federal agency is leading the investigation into what caused the spacecraft to crash in California's Mojave Desert during a test flight on Friday, killing one pilot and badly injuring the other.
Virgin Galactic is the fledgling space tourism company of billionaire entrepreneur Richard Branson.
Hart told a news conference late on Sunday investigators had determined the "feathering" system should have been deployed when the vehicle was traveling about 1.4 times the speed of sound. Instead, the feather began rotating when the vehicle was traveling at Mach 1, he said.
The system, which folds the vehicle in half to create more atmospheric drag, was unlocked early by the co-pilot but a second command to move the feather handle into position was not sent, he said.
Investigators also recovered SpaceShipTwo's propellant tanks and engine intact, indicating there was no explosion.
"The engine burn was normal up until the extension of the feathers," Hart told reporters.
He emphasized that the NTSB was not saying the early deployment of the ship's feather was the cause of the accident and stressed that the investigation was in its earliest stages.
"We have months and months of investigation," Hart said.
SpaceShipTwo was conducting test flights and was not yet certified for commercial operations when the crash occurred, delaying indefinitely the start of passenger service.
Branson and his son plan to fly on the first commercial flight. More than 800 people have paid the full $250, 000 for a ticket or put down deposits to eventually fly aboard the spaceship, which is carried to an altitude of about 45,000 feet and released. The spaceship then fires its rocket motor to catapult it to about 62 miles above Earth, giving passengers a view of the planet set against the blackness of space — and a few minutes of weightlessness.
The two pilots involved were employees of Scaled Composites, a Northrop Grumman Corp subsidiary that designed and built the six-passenger, two-pilot craft for Virgin Galactic.
Michael Alsbury, 39, has been identified as the co-pilot who died. Peter Siebold, the 43-year-old pilot riding in the right-hand seat, parachuted to the ground and was recovering at a nearby hospital, Scaled Composites said in a statement.