SpaceShipTwo's Descent System Deployed "Without Being Commanded"

Investigators looking into Friday's tragic crash of SpaceShipTwo are saying that a safety device on the Virgin Galactic spacecraft had been deployed prematurely — and that it may have gone off spontaneously.


According to federal investigators, SpaceShipTwo's unique tail section, which "feathers" at an angle to help the spacecraft make a safe descent, unfurled as it was ascending and it did so without being ordered. During a news conference on Sunday, National Transportation Safety Board (NTSB) acting chairman Christopher Hart said the feathering mechanism wasn't supposed to be unlocked until the spacecraft reaches Mach 1.4, or 1.4 times the speed of sound. But during the flight, co-pilot Michael Alsbury moved the mechanism's lock-unlock lever into the unlocked position earlier, at just slightly above Mach 1.

But the feathering procedure requires two separate steps to engage. First, the pilots must unlock the mechanism. Second, they must move a separate feather handle into position. For some unknown reason, SpaceShipTwo's feather mechanism began moving almost immediately, even though neither pilot executed that second step.

SpaceShipTwo during a normal descent in feathering mode. Image: Virgin Galactic.

The result of the premature deployment would have increased the plane's atmospheric drag considerably and at the worst possible time — as it was rapidly ascending into space.


Hart said the second stage of deployment happened "without being commanded."


Image: AP Photo/Kenneth Brown.

"Two seconds later, we saw disintegration," Hart said. Almost immediately, telemetry and video data "terminated."


The U.S. investigators have offered no explanations for why the tail mechanism moved prematurely, but the revelation has shifted the focus away from earlier speculation about the plane's hybrid rocket motor and the use of a new fuel. What's more, the motor and the fuel tanks have been recovered, and they're intact. It's a strong indication that the motor and the fuel were not at fault.

Still, Hart said, "there's much more that we don't know" and that "we are a long way from finding the cause."


It could takes months, if not an entire year, for NTSB investigators to conduct and finalize the investigation. A November 2nd press release from Virgin Galactic makes its position on the matter clear:

Now is not the time for speculation. Now is the time to focus on all those affected by this tragic accident and to work with the experts at the NTSB, to get to the bottom of what happened on that tragic day, and to learn from it so that we can move forward safely with this important mission.


Pilot Peter Siebold survived the incident, but his co-pilot, Alsbury, died.

[ Virgin Galactic | NBC | BBC ]

Top image: Ringo H.W. Chiu.

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