Cause of fatal 2014 SpaceShipTwo crash determined by NTSB

The National Transportation Safety Board releases its final report on the October 31 crash that killed one of two pilots on the test flight over the Mojave Desert.

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Virgin Galactic's SpaceShipTwo. Jon Griffith/Virgin Galactic

On the morning of October 31, 2014, the white shape of SpaceShipTwo took to the skies over the Mojave Desert in California. It would be a tragically short flight -- about 13 seconds long.

Just after 10:07 a.m. PT, the craft broke into pieces. It appeared to disintegrate just seconds after the thermoplastic rocket motor fired, leading some to conclude that a structural weakness caused the failure. On Tuesday, the National Transportation Safety Board released its final report on the crash, concluding that a combination of co-pilot error and inadequate safety procedures were at fault.

The cause of the ship's breakup was an early deployment of its feathering system. In a normal flight, the ship rockets up and out of the atmosphere and then, momentum exhausted, falls gently back to Earth. This is when the feathering system is supposed to go into effect, the wings folding backward to increase drag and stabilize the return journey. Those wings are supposed to be locked in place until the ship accelerates through a speed of Mach 1.4 (just over 1,000 mph, or 1,700 kph). However, according to the NTSB report, co-pilot Michael Alsbury released those locks early, at Mach 0.92. Four seconds later, the ship broke up.

The wreckage of SpaceShipTwo. National Transportation Safety Board

Alsbury died in the accident, while pilot Peter Siebold's seat was thrown clear. Siebold was able to release his harness and deploy his parachute, saving his life.

The craft was one of the prototype vehicles crafted by Scaled Composites for Virgin Galactic, built to ultimately deliver paying customers to the edge of space. Throughout that year, testing for the company and its radically designed, rocket-powered craft had gone quite well. There was optimism on the part of many that commercial flights were perhaps only months away.

To prevent this from happening again, a number of changes have been made, including the addition of a mechanical system to prevent the feathering system from premature unlocking, and a change to the checklist and call-outs that the pilots must go through before unlocking that system. An external safety review of SpaceShipTwo is also ongoing.

It remains to be seen when Virgin Galactic and its new SpaceShipTwo craft will resume testing.