VSS Enterprise (tail number: N339SS) was the first SpaceShipTwo (SS2) spaceplane, built by Scaled Composites for Virgin Galactic. It had been planned to be the first of five commercial suborbital SS2 spacecraft planned by Virgin Galactic, but only one other was ever built.
It was also the first ship of the Scaled Composites Model 339 SpaceShipTwo class, based on upscaling the design of record-breaking SpaceShipOne.
The VSS Enterprise's name was an acknowledgement of the USS Enterprise from the Star Trek television series. The spaceplane also shared its name with NASA's prototype Space Shuttle orbiter, as well as the aircraft carrier USS Enterprise.
It was rolled out on 7 December 2009.
SpaceShipTwo made its first powered flight in April 2013. Richard Branson said it "couldn't have gone more smoothly".
Enterprise was destroyed during a powered test flight on 31 October 2014, killing one pilot, Michael Alsbury, and seriously injuring another, Peter Siebold. This was the first spacecraft-related accident in which part, but not all, of the crew survived. An investigation revealed the accident was caused by premature deployment of the "feathering" system, the ship's descent device; the NTSB also faulted the spacecraft's design for lacking fail-safe mechanisms that could have deterred or prevented early deployment.
Initial projections by Virgin Galactic in 2008 called for test flights to begin in late 2009 and commercial service to start in 2011. This schedule was not achieved, with captive carry and glide flight tests beginning in 2010, and the first test flight under rocket power in 2013.
In October 2009, Virgin Galactic CEO Will Whitehorn outlined the flight test program for SpaceShipTwo. The test program includes seven phases:
Captive carry under White Knight Two
Subsonic testing with only a brief firing of the rocket
Supersonic atmospheric testing
Full flight into suborbital space
Execute a detailed and lengthy appraisal process with the FAA/AST to demonstrate the system's robustness and eventually obtain a commercial launch license to begin commercial operations.
On 22 March 2010, the SpaceShipTwo vehicle VSS Enterprise underwent a captive carry test flight, with the parent White Knight Two aircraft, VMS Eve, performing a short flight while carrying the Enterprise.
A second test flight was made on 16 May 2010, reaching SS2's launch altitude (51,000 feet) and lasting nearly five hours, in order to facilitate "cold soak" testing of SS2's avionics and pressurization system. Thereafter, "a simulated spaceship descent/glide mission was made from [launch] altitude."
Between these two flights, the SpaceShipTwo airframe was modified by the addition of two interior fins, with one fin being added to the inside (rocket-side) of each of the craft's twin vertical stabilizers.
On 15 July 2010, VSS Enterprise made its first crewed flight. The craft remained attached to VMS Eve as planned, and underwent a series of combined vehicle systems tests. The flight lasted a total of 6 hours and 21 minutes. A second, similar crewed flight of VSS Enterprise and VMS Eve was carried out on 30 September 2010, lasting approximately 5 hours. Among the objectives of these flights was the improvement of pilot proficiency, and the results of the flights were deemed to show that the systems were capable of supporting future glide missions.
On 10 October 2010, VSS Enterprise made its first crewed gliding test flight. It was released from VMS Eve at 45,000 ft (13,700 metres) and glided to a safe landing at the Mojave Air and Spaceport. A second gliding test flight took place on 28 October 2010 and a third on 17 November 2010. As of December 2010, Scaled reported that the flight test program was exceeding expectations. The fourth test flight took place on 13 January 2011, while the fifth and sixth glide flights occurred on 22 and 27 April 2011, respectively. Following this, the feathered reentry configuration was tested in flight on 4 May 2011, with weekly test flights continuing through the end of May.