The Virgin Galactic space plane that broke apart over the Mojave Desert on Friday shifted early into a high-drag configuration that was designed to slow it down, federal accident investigators have said.
The accident killed the co-pilot, Michael Alsbury; the pilot, Peter Siebold survived after parachuting out of the plane.
The craft, called SpaceShipTwo, was designed to rocket up, and when it reached the top of its ascent, two tail booms would rotate upward into a “feathered” position. That would create more drag and stability, allowing the plane to descend gently back into the atmosphere, much like a badminton shuttlecock.
At the news conference Sunday night at the Mojave Air and Space Port in California, Christopher A. Hart, the acting chairman of the National Transportation Safety Board, said the plane was not supposed to move into the feathered configuration unless the pilots took two actions: First, a lever would be switched to unlock the tail booms, then a handle would be moved to feather the booms.
“About nine seconds after the engine ignited, the telemetry data told us the feather parameters changed from locked to unlocked,” Mr. Hart said.
In addition, a video camera in the cockpit showed Mr. Alsbury switching the lever to the unlocked position, Mr. Hart said. That occurred at a velocity of about Mach 1, which is the speed of sound at a given altitude. Under normal operations, that lever would not be moved until later in the flight, when the space plane had reached a speed of Mach 1.4, Mr. Hart said. The plane’s altitude would also be higher, where the air is thinner.
Two seconds later, the booms rotated, even though neither pilot had moved the feathering handle.
“Shortly after the feathering occurred, the telemetry data terminated, and the video data terminated,” Mr. Hart said. “The engine burn was normal, up until the extension of the feathers.”
Previously, speculation had focused on the engine, a new design that was fired for the first time in flight using a new fuel. The new motor was intended to provide better performance for SpaceShipTwo, generating more thrust and reducing vibrations.
Mr. Hart said the findings he reported were a “statement of fact” and not a conclusion about the cause of the accident.
“There is much more we don’t know, and our investigation is far from over,” he said.
Investigators located almost all of the important pieces of the space plane, which had fallen along a debris field five miles long. That included the fuel tanks and engine, which were “intact, showed no signs of burn through, no signs of being breached,” Mr. Hart said.
Other issues the investigators will examine include training and the safety culture at Virgin Galactic and at Scaled Composites, the unit of Northrop Grumman that designed and built SpaceShipTwo, and whether the companies felt pressure to resume testing because of delays.
Virgin Galactic, founded by the billionaire entrepreneur Richard Branson, is to take space tourists on short rides to an altitude of 62 miles, which is considered the boundary of outer space, providing a few minutes of weightlessness. More than 700 people have reserved seats; tickets cost $250,000 each.
Technical issues have pushed back the start of the commercial flights, and until Friday, SpaceShipTwo had not ignited its motor during a test flight since January. In September, Mr. Branson said he hoped commercial flights would begin next spring.
In a statement Sunday, Virgin Galactic responded to criticism that the design of SpaceShipTwo was flawed and that the test flights were reckless.
“At Virgin Galactic, we are dedicated to opening the space frontier, while keeping safety as our ‘North Star,”’ the company said. “This has guided every decision we have made over the past decade, and any suggestion to the contrary is categorically untrue.”