Inadequate pilot training and lack of consideration for lessons already known elsewhere in transportation has been identified as the underlying cause behind last year’s crash of Virgin Galactic’s SpaceShipTwo, the use US National Transportation Safety Board ruled.
Following several months of investigation, the NTSB released a report with its findings, confirming the initial suspicion it was an error of one of the experimental spacecraft’s pilots that led to the disaster that took place on 31 October 2014 above California’s Mojave desert.
However, the true culprit, the NTSB said, is Virgin Galactic’s partner Scale Composites, who built the ill-fated spacecraft, who didn’t provide sufficient training to the pilots and failed to consider a human error and its consequences during the design of the spaceship.
"Many of the safety issues that we will hear about today arose not from the novelty of a space launch test flight, but from human factors that were already known elsewhere in transportation," said NTSB Chairman Christopher A. Hart presenting the investigation results.
The investigation found co-pilot Michael Alsbury unlocked the erectable tail section of the spacecraft, designed to slow it down at supersonic speeds, when the plane was travelling at only 0.8 Mach. At this speed, the aerodynamic forces were not sufficient to hold the feather in place, causing it to deploy uncommanded. The deployment at this stage of the flight resulted in extreme aerodynamic loads that broke the spaceship apart. Alsbury died in the accident while first pilot Peter Siebold managed to catapult himself and survived with injuries.
The NTSB suggested SpaceShipTwo should not have been flying at all, as it was awarded an experimental flight permit by the US Federal Aviation Administration (FAA) despite the FAA being aware of the fact that Scale Composites’ hazard analysis did not meet the software and human error requirements.
The permit was issued based on mitigation measures included in Scaled Composites’ application but the FAA subsequently failed to ensure the measures were being implemented.
Moreover, the investigation found the company discussed the risks related to the inadvertent release of the braking mechanism during the subsonic stage of the flight with the pilots only once during their training, about three years ago.
"Scaled did not consider that a pilot would induce that kind of failure," said lead investigator Lorenda Ward.
Scaled Composites, owned by Northrop Grumman acknowledged the findings and pledged to implement the lessons learned.
"Scaled will incorporate learning from this accident into its flight procedure review and safety assessment in future projects," Scaled Composites said in a statement posted on NTSB's website after the hearing.
"Scaled will expand the documentation of training and testing further to promote safety, including with emphasis on the challenges inherent in rocket flight," the statement added.
The accident was a setback in billionaire entrepreneur Richard Branson's more than decade-old quest to ferry space tourists beyond Earth's atmosphere.
The lost craft was the first of a planned fleet of five vehicles that Virgin eventually expects to use to fly passengers on short, suborbital flights to the edge of space. It has already sold about 700 tickets for rides that cost $250,000 each.
"In short, the NTSB has been able to confirm its initial statements as to the cause of the accident: that the feather, a unique system used for the spaceship's safe re-entry from space, was manually and prematurely unlocked by Scaled's pilot,” Sir Richard Branson said following the announcement.
"With the investigation completed, Virgin Galactic can now focus fully on the future with a clean bill of health and a strengthened resolve to achieve its goals."
The Spaceship Company, a Virgin-owned operation based in Mojave, has taken over construction of SpaceShipTwo vehicles from Scaled, a transition that began before last year's accident.
Test flights of Virgin Galactic's new ship are scheduled to begin before the end of the year.
Virgin Galactic was criticised by space industry insiders shortly after the accident for its safety engineering practices.