One Scaled Composites test pilot died and another was injured severely after a powered flight of SpaceShipTwo ended in disaster near Mojave, California, for the commercial space tourism venture led by Richard Branson’s Virgin Galactic on 31 October.

If the test had gone as planned, upon releasing from mothership WhiteKnightTwo around 45,000ft at around 215kt, SpaceShipTwo would have ignited a hybrid rocket motor propelled by a new fuel chemistry on the fourth powered test of the suborbital spaceplane, commencing a final phase of testing before achieving certification by the US Federal Aviation Administration (FAA).

Instead, SpaceShipTwo released from WhiteKnightTwo at about 10:10, quickly achieved ignition – and then something went tragically wrong.

There were multiple witness reports of an explosion, but Mojave Air and Space Port chief executive Stuart Witt says he saw nothing unusual. Scaled Composites’ ground control team became aware of an “in-flight anomaly” around 10:12, but nothing obvious was visible from Witt’s standpoint on the ground. He watched the aircraft drop from WhiteKnightTwo, then observed a different plume than he had seen before, which Scaled Composites had warned him to expect. But Witt’s first hint that something was awry was nothing that he could see or hear.

“There was a pause of about 90,” Witt said at a press conference. “I knew [there was an anomaly] when other things weren’t happening. It wasn’t because of something did happen. It was because of what I was not hearing and not seeing.”

Local police and fire crews responded to the scene about 25mi north of Mojave and quickly discovered a SpaceShipTwo crew member who had died. The other pilot was picked up with “major” injuries and rushed to Antelope Valley Hospital, says Kern County Sheriff Donny Youngblood.

“It appeared to be major injuries. We don’t know really what that means yet. We hope that the survivor will be just fine,” Youngblood says.

The first fatal incident involving a commercial spacecraft drew a swift response from Washington DC. The FAA launched an investigation. Meanwhile, the National Transportation Safety Board (NTSB) dispatched a “go-team” to Mojave, which is expected to arrive on 1 November at 07:30, says Kevin Mickey, president of Scaled Composites, a subsidiary of Northrop Grumman.

Mickey and Virgin Galactic chief executive George Whitesides decline to release the names of the two pilots involved in the incident.

Mickey describes the new fuel mixture as a “nuance” in the design of a rocket motor, which had already been proven to be safe during months of ground testing.

The powered flight represented the first flight test of SpaceShipTwo since last January. Although ground testing continued, flight testing was put on hold as the programme switched from a rubber-based solid fuel that was determined to be unstable on lengthy burns to a plastic-based solid fuel. It was the 55th flight test overall of the vehicle mated to WhiteKnightTwo and the 34th test involving a free flight of SpaceShipTwo.

Four Scaled Composites employees have been killed during the 10-year-long SpaceShipTwo test programme, including three workers who died when an oxidizer tank exploded during a 2007 ground test.

“Space is hard and today was a tough day,” Whitesides says. “[The] future rests in many ways on hard days like this. But we believe we owe it to the folks who are flying these vehicles as well as the folks who have been working so hard on them to understand this and move forward, which is what we’ll do.”