It was human error which led to the SpaceShipTwo accident on 31 October, last year, in California’s Mojave Desert. Nine months after the incident, the US National Transportation Safety Board (NTSB) has released its first investigation report, which leaves no room for doubt.
Premature release by the copilot of the rotating tail boom, which serves to slow the vessel, resulted in the inflight breakup of the aircraft. The feather (braking) system was activated too soon, at a speed of Mach 0.8 (1,000 km/h or 620 mph). It would normally be unlocked when the ship’s rocket engine is switched off upon re-entry into the atmosphere. The structure of the craft was not designed to undergo such a load factor.
In the report, Scaled Composites, the company that manufactured the ship is hardest hit. According to the Board: ‘‘Scaled Composites failed to consider the possibility that a test pilot could unlock the feather early or that this single-point human error could cause the feather to deploy uncommanded.’’ Clearly, no protection to prevent this scenario from occurring had been installed on the spaceplane. The Board also found that Scaled Composites failed to ensure that test pilots adequately understood the risks of unlocking the feather early.
Subsequently, the Board has made recommendations to the Federal Aviation Administration and the Commercial Spaceflight Federation. If acted upon, the recommendations would establish human factors guidance for commercial space operators.
