SpaceShipTwo's fatal accident likely not caused by new rocket engines; feathering system scrutinized

Monday, November 3, 2014, 6:05 PM - Investigators looking into the cause of Friday's fatal crash of Virgin Galactic's SpaceShipTwo still aren't sure exactly what caused the accident, however they have ruled out one possible reason. The new engines that had been installed on the hybrid rocket jet since the last test were apparently not the reason for the crash.

According to Christopher Hart, the acting chairman of the National Transportation Safety Board, who spoke in a media briefing on Monday, the engines and fuel tanks "showed no signs of burn-through, no signs of being breached."

Instead, as the video above mentions, the current focus of the investigation seems to be on SpaceShipTwo's feathering system - the tail wings that fold upward during re-entry into the atmosphere, to increase drag on the craft.

According to Hart, it's not known yet if the feather system is the actual cause of the accident. In a press conference on Sunday, he emphasized that discussions about the feather system were "a statement of fact, and not a statement of cause."

During initial flight maneuvers - between being released by the WhiteKnightTwo 'mothership' and when it achieves its planned flight ceiling at a speed of about Mach 1.4 - these feathers remain locked into a position parallel to the rest of the craft, like wings. It's only when the craft reaches the speed of Mach 1.4 that the feather system is unlocked and then deployed so that they pivot, and the help bring the craft back down to Earth.

"In order for feathering ... to be commanded by the pilots, two actions must occur," Hart said during the briefing. "One is that the lock/unlock handle must be moved from lock to unlock, and two is that the feathering handle must be moved to the feather position."

From the telemetry data and the cockpit video recordings, the release of SpaceShipTwo from WhiteKnightTwo went as expected, and the engine burn was normal as the craft accelerated up to Mach 1.0. There is evidence at that point that co-pilot Michael Alsbury - who died in the accident - unlocked the feather system ahead of schedule, turning the lock/unlock handle from the lock position to the unlock position when the craft was travelling at just over Mach 1.0. However, Alsbury did not deploy the feather system at that time.

Even so, according to Hart, approximately two seconds after the feathering system was unlocked, the feathers deployed, even though the feathering handle had not been moved to the feather position.

Immediately afterward, telemetry and video data from the craft stopped.

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"Again, I want to emphasize that we have not determined the cause," Hart said in the briefing. "I am not stating that [the premature unlocking of the feathering system] is the cause of this mishap. We have months and months of investigation to determine what the cause was."

The investigation team will be looking at training issues, whether there was pressure to continue testing, the safety culture, the spacecraft design, and the procedures used during the flight.

"We've got many, many issues to look into, much more extensively, before we can determine the cause," Hart concluded.