VSS Enterprise

VSS Enterprise, bearing tail number N339SS, was the inaugural SpaceShipTwo (SS2) suborbital spaceplane, constructed by Scaled Composites on behalf of Virgin Galactic. It was intended to be the first of five commercial SS2 spacecraft Virgin Galactic planned, though ultimately only one additional unit was produced. As the initial vessel in the Scaled Composites Model 339 SpaceShipTwo class, its design was a scaled-up version of the record-setting SpaceShipOne. The name "Enterprise" paid homage to the USS Enterprise from the *Star Trek* television series, and was also shared with NASA's prototype Space Shuttle orbiter and the aircraft carrier USS Enterprise. The spaceplane was unveiled on 7 December 2009, and its first rocket-powered flight occurred in April 2013, which Richard Branson described as having "couldn't have gone more smoothly."

Enterprise was destroyed during a powered test flight on 31 October 2014, resulting in the death of pilot Michael Alsbury and serious injury to pilot Peter Siebold. This marked the first spacecraft-related accident where part of the crew survived. An investigation determined that the crash was triggered by the premature deployment of the "feathering" system—the vehicle's descent mechanism—and the NTSB also criticized the spacecraft's design for lacking fail-safe features that could have prevented or mitigated the early activation.

The flight test program began with initial projections in 2008 aiming for test flights in late 2009 and commercial service by 2011, but this timeline slipped. Captive carry and glide tests started in 2010, with the first rocket-powered test in 2013. In October 2009, Virgin Galactic CEO Will Whitehorn outlined a seven-phase test program: vehicle ground testing, captive carry under White Knight Two, unpowered glide testing, subsonic testing with brief rocket firings, supersonic atmospheric testing, full suborbital space flight, and a detailed FAA/AST appraisal to secure a commercial launch license.

On 22 March 2010, VSS Enterprise underwent its first captive carry test flight while attached to the White Knight Two aircraft, VMS Eve. A second test on 16 May 2010 reached SS2's launch altitude of 51,000 feet, lasting nearly five hours for "cold soak" testing of avionics and pressurization, followed by a simulated descent and glide mission.