The
National Transportation Safety Board (NTSB) investigated the accident. A Go Team was dispatched to the accident site on October 31, 2014. It was expected to take about a year for the final report to be released. and a press release on the same day, the NTSB cited inadequate design safeguards, poor pilot training, lack of rigorous federal oversight and a potentially anxious co-pilot without recent flight experience as important factors in the 2014 crash. They determined that the co-pilot, who died in the accident, prematurely unlocked a movable tail section some ten seconds after SpaceShipTwo fired its rocket engine and was breaking the sound barrier, resulting in the craft breaking apart. The Board also found that the Scaled Composites unit of Northrop Grumman, which designed and flew the prototype space tourism vehicle, did not properly prepare for potential human slip-ups by providing a fail-safe system that could have guarded against such premature deployment. "A single-point human failure has to be anticipated," board member
Robert Sumwalt said. Instead, Scaled Composites "put all their eggs in the basket of the pilots doing it correctly." The report's details of the final moments of the flight reveal that the feather system was unlocked as SS2 accelerated under rocket power through Mach 0.92 at 10.07:28, 9 seconds after release from the WhiteKnightTwo (WK2) carrier aircraft and 14 seconds before the vehicle would have reached Mach 1.4, the minimum speed at which the tail was designed to be unlocked. Telemetry, in-cockpit video and audio data confirmed that co-pilot Michael Alsbury announced "unlocking" as Mach 0.92 was passed and vehicle breakup occurred within the next 4 seconds. The feathering device, conceived by Scaled Composites designer
Burt Rutan, is deployed after reaching maximum altitude, increasing drag and slowing descent as a carefree and stable reentry method for recovery of SpaceShipOne. The system operates by rotating the vehicle's twin tail booms upward about the trailing edge of the wing by around 65 degrees; following reentry, the actuators rotate the booms down into the flush position for approach and landing. Aerodynamic forces when accelerating through the
transonic moments of the flight, above Mach 0.85 and below Mach 1.34, push upwards on the tail; releasing the locks before the vehicle passes these speeds means that a pair of actuators were the only things keeping the tail in place against these powerful forces, which had unintentionally been sufficient on earlier test flights. Investigators said the developer of the spacecraft failed to include systems to protect against human error, believing that highly trained test pilots were simply incapable of making a wrong move, and that co-pilot Michael Alsbury may have been influenced by time pressure, along with strong vibration and acceleration forces he had not experienced since his last powered test flight in April 2013. The combination "could have increased the co-pilot's stress." The board found that during years of development and flight tests, engineers at Scaled Composites assumed that any pilot mistakes would occur only in reaction to systems failures, not as the cause of such failures. The Flight Test Data Card for this mission, giving information on the test vehicle and the step-by-step mission plan, called for the feathering system to be unlocked at Mach 1.4, but did not indicate that unlocking early could be a danger. The NTSB investigators also found just one email, from 2010, and one presentation slide, from 2011, that even mentioned the risks of unlocking before completing the transonic stage of the acceleration. The NTSB members also criticized the
FAA, which approved the experimental test flights, for failing to pay enough attention to human factors or to provide necessary guidance to the nascent commercial space flight industry on the topic. They also cited pressure from some FAA managers to quickly approve experimental flight permits, sometimes without fully understanding technical issues or the details of the spacecraft. In its submission to the NTSB, Virgin Galactic says the second SS2, nearing completion, had been modified with an automatic mechanical inhibit device to prevent locking or unlocking of the feather during safety-critical phases. An explicit warning about the dangers of premature unlocking has also been added to the checklist and operating handbook, and a formalized
crew resource management (CRM) approach, already used by Virgin for its WK2 operations, is being adopted for SS2. This will include call-outs and a challenge/response protocol. While the report cites CRM issues as a likely contributing cause, Virgin says there is no plan to modify the cockpit display system. NTSB chairman Christopher Hart said that, as the Board had learned "with a high degree of certainty the events that resulted in the breakup", he hoped the investigation would prevent such an accident from happening again. "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." Hart added "for commercial spaceflight to successfully mature, we must meticulously seek out and mitigate known hazards, as a prerequisite to identifying and mitigating new hazards." Virgin Galactic is proceeding with its plans for space flight and is building another craft; company officials said that their commitment to commercial spacecraft had not wavered despite the crash and they expected the company to resume test flights later in 2015, though that date subsequently slipped. On 19 February 2016,
Enterprise's successor,
VSS Unity, was unveiled by Scaled Composites and Virgin Galactic. ==Responses==