The Scaled Composites Model 339 SpaceShipTwo (SS2) was an air-launched suborbital spaceplane type designed for space tourism.

SpaceShipTwo was carried to its launch altitude by a Scaled Composites White Knight Two, before being released to fly on into the upper atmosphere powered by its rocket engine.

[1] The spaceship was officially unveiled to the public on 7 December 2009 at the Mojave Air and Space Port in California.

[3] Virgin Galactic planned to operate a fleet of five SpaceShipTwo spaceplanes in a private passenger-carrying service[4][5][6][7] and took bookings for some time, with a suborbital flight carrying a ticket price of US$250,000 in 2015.

[14][15] One pilot, Michael Alsbury, was killed; the other was treated for a serious shoulder injury after parachuting from the stricken spacecraft.

[27] It launched from its mothership, White Knight Two, at an altitude of 13,500 m (44,300 ft),[28] and reached supersonic speed within 8 seconds.

SpaceShipTwo had 43 and 33 cm (17 and 13 in)-diameter windows for the passengers' viewing pleasure,[30] and all seats reclined back during landing to decrease the discomfort of G-forces.

[33] SpaceShipTwo (and the WhiteKnightTwo launcher aircraft) were built by The Spaceship Company, originally formed as a joint venture between Scaled Composites and Virgin Galactic.

[38][21] Unity was retired on 8 June 2024 after its final flight took place on that date, as Virgin Galactic shifted its focus to the next generation Delta-class vehicles.

[44] SpaceShipTwo was launched from the WhiteKnightTwo launcher aircraft, which took off from the Mojave Air and Space Port in California during testing.

On 28 September 2006, Virgin Group founder Sir Richard Branson unveiled a mock-up of the SpaceShipTwo passenger cabin at the NextFest exposition at the Jacob K. Javits Convention Center in New York.

The event involved the first SpaceShipTwo being christened by then - Governor of California Arnold Schwarzenegger as the VSS Enterprise.

[50] The hybrid rocket engine design for SpaceShipTwo was problematic and caused extensive delays to the flight test program.

In September 2012, Virgin Galactic announced that the unpowered subsonic glide flight test program was essentially complete.

[71] On 31 October 2014, SpaceShipTwo VSS Enterprise suffered an in-flight breakup during a powered flight test,[72][73] resulting in a crash killing one pilot, Michael Alsbury, and injuring the other.

In July 2015, the NTSB released a report which cited inadequate design safeguards, poor pilot training, lack of rigorous federal oversight and a potentially anxious co-pilot as important factors in the 2014 crash.

[79][80] While the co-pilot was faulted for prematurely deploying the ship's feathering mechanism, the Federal Aviation Administration, Federal Aviation Administration Office of Commercial Space Transportation, and the ship's designers were also faulted for not creating a fail-safe system that could have guarded against such premature deployment.

[86][87][88][89] After several glide flights over the preceding months, in July 2017, Richard Branson suggested that the craft was to begin powered tests at three-week intervals.

[94] On 13 December 2018, SpaceShipTwo VSS Unity reached its highest altitude up to that point, 82.72 km (51.40 mi).

[23] Following a February 2019 spaceflight, VSS Unity began to undergo modifications in preparation for commercial service; this includes an upgrading the flight deck and installing a passenger cabin.

[96] It was later revealed in 2021 that VSS Unity had actually suffered a large crack in its structure during its 2019 spaceflight, requiring repair work to the vehicle.

[97] Following its return to service VSS Unity made a test flight that included Richard Branson as a passenger on July 11, 2021.

While in ascent the vehicle triggered a red warning light which indicated it had deviated from its safe flight path.

[98] On 2 September 2021, it was publicly announced that further SpaceShipTwo flight tests would be grounded by FAA mandate until the investigation was completed.

By December 2007, Virgin Galactic had 200 paid-up customers on its books for the early flights, and 95% were passing the 6-8 g centrifuge tests.

[122] By March 2011, Virgin Galactic had submitted SpaceShipTwo as a reusable launch vehicle for carrying research payloads in response to NASA's suborbital reusable launch vehicle (sRLV) solicitation, which was a part of the agency's Flight Opportunities Program.

[123] In August 2005, the president of Virgin Galactic stated that if the suborbital service with SpaceShipTwo would be successful, the follow-up SpaceShipThree would be an orbital craft.

In 2008, Virgin Galactic suggested that it may develop a high-speed passenger vehicle to offer transport through point-to-point suborbital spaceflight.