The Scaled Composites Model 339 SpaceShipTwo (SS2) is a retired air-launched suborbital spaceplane type designed for space tourism. It was manufactured by The Spaceship Company, a California-based company owned by Virgin Galactic.
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. It then glided back to Earth and performed a conventional runway landing. The spaceship was officially unveiled to the public on 7 December 2009 at the Mojave Air and Space Port in California. On 29 April 2013, after nearly three years of unpowered testing, the first SS2 constructed successfully performed its first powered test flight.
Virgin Galactic planned to operate a fleet of five SpaceShipTwo spaceplanes in a private passenger-carrying service and took bookings for some time, with a suborbital flight carrying a ticket price of US$250,000 in 2015. The spaceplane was also used to carry scientific payloads for NASA and other organizations.
On 31 October 2014, during a test flight, the first SpaceShipTwo VSS Enterprise broke up in flight and crashed in the Mojave Desert. An investigation found that the craft's descent device deployed too early. One pilot, Michael Alsbury, was killed; the other was treated for a serious shoulder injury after parachuting from the stricken spacecraft.
The second SpaceShipTwo spacecraft, VSS Unity, was unveiled on 19 February 2016. The vehicle underwent flight testing 2016–2023. Its first flight to space (above 50 miles altitude), VSS Unity VP03, took place on 13 December 2018. The first operational flight of Unity (defined as the first flight flying passengers that were not Virgin Galactic employees) was Galactic 01 on 29 June 2023. The final flight of Unity was Galactic 07 on 8 June 2024.
Design overview
The SpaceShipTwo project was based in part on technology developed for the first-generation SpaceShipOne, which was part of the Scaled Composites Tier One program, funded by Paul Allen. The Spaceship Company licensed this technology from Mojave Aerospace Ventures, a joint venture of Paul Allen and Burt Rutan, the designer of the predecessor technology.
SpaceShipTwo was a low-aspect-ratio passenger spaceplane. Its capacity was planned to be eight people — six passengers and two pilots. The SpaceShipTwo spaceplanes never flew with more than six people on board (four passengers, two pilots). The apogee of the new craft was designed to be approximately in the lower thermosphere, higher than the Kármán line but as of July 2021, the maximum height reached was 89.9 km. In the end, the SpaceShipTwos never broke the 100 km limit. The predecessor craft SpaceShipOne's target was also 100 km but the last flight reached an altitude of . SpaceShipTwo was designed to reach , using a single hybrid rocket engine — the RocketMotorTwo. It launched from its mothership, White Knight Two, at an altitude of , and reached supersonic speed within 8 seconds. After 70 seconds, the rocket engine cut out and the spacecraft coasted to its peak altitude. SpaceShipTwo's crew cabin was long and in diameter. The wing span was , the length was and the tail height was .
SpaceShipTwo used a feathered reentry system, feasible due to the low speed of reentry. In contrast, orbital spacecraft re-enter at orbital speeds, close to , using heat shields. SpaceShipTwo was furthermore designed to re-enter the atmosphere at any angle. It decelerated through the atmosphere, switching to a gliding position at an altitude of , and took 25 minutes to glide back to the spaceport.
SpaceShipTwo and White Knight Two were, respectively, roughly twice the size of the first-generation SpaceShipOne and mothership White Knight, which won the Ansari X Prize in 2004. SpaceShipTwo had -diameter windows for the passengers' viewing pleasure, In 2008, Burt Rutan remarked on the safety of the vehicle: