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SS2 and VMS Eve.jpg
SpaceShipTwo (central fuselage) carried under its mothership, White Knight Two.
Role Passenger spaceplane
Manufacturer The Spaceship Company
First flight 10 October 2010 (first glide flight)

29 April 2013 (first powered flight)

Status Powered test flight program underway
Primary user Virgin Galactic
Developed from SpaceShipOne

The Scaled Composites Model 339 SpaceShipTwo (SS2) is a suborbital, air-launched spaceplane designed for space tourism. It is under development as part of the Tier 1b program[1] under contract to The Spaceship Company, a California-based company that is wholly owned by its sister company Virgin Galactic. The Spaceship Company was formerly a joint venture between Virgin Galactic and Scaled Composites, but Virgin became the company's sole owner in 2012.[2]

SpaceShipTwo is carried to its launch altitude by a jet-powered mothership, the Scaled Composites White Knight Two, before being released to fly on into the upper atmosphere, powered by a rocket motor. It then glides back to Earth and performs a conventional runway landing.[3] The spaceship was officially unveiled to the public on 7 December 2009 at the Mojave Air and Space Port in California.[4] On 29 April 2013, after nearly three years of unpowered testing, the spacecraft successfully performed its first powered test flight.[5]

Virgin Galactic plans to operate a fleet of five SpaceShipTwo spaceplanes in a private passenger-carrying service, starting in 2014,[6][7][8][9] and have been taking bookings for some time, with a suborbital flight carrying an initial ticket price of US$200,000.[10] The spaceplane could also be used to carry scientific payloads for NASA and other organizations.[11]

Design overview[edit]

A schematic diagram of SpaceShipTwo.

The SpaceShipTwo project is 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 licenses this technology from Mojave Aerospace Ventures, a joint venture of Paul Allen and Burt Rutan, the designer of the predecessor technology.

SpaceShipTwo is a low-aspect-ratio passenger spaceplane. Its capacity will be eight people: six passengers and two pilots. The apogee of the new craft will be approximately 110 km (68 mi) in the lower thermosphere, 10 km (6.2 mi) higher than the Kármán line which was SpaceShipOne's target (though the last flight of SpaceShipOne reached a one-time altitude of 112 km (70 mi)). SpaceShipTwo will reach 4,200 km/h (2,600 mph), using a single hybrid rocket motor – the RocketMotorTwo.[12] It launches from its mothership, White Knight Two, at an altitude of 15,000 metres (50,000 ft), and reaches supersonic speed within 8 seconds. After 70 seconds, the rocket motor cuts out and the spacecraft will coast to its peak altitude. SpaceShipTwo's crew cabin is 3.7 m (12 ft) long and 2.3 m (7.5 ft) in diameter.[13] The wing span is 8.2 m (27 ft), the length is 18 m (60 ft) and the tail height is 4.6 m (15 ft) .[14]

SpaceShipTwo uses a feathered reentry system, feasible due to the low speed of reentry – by contrast, the Space Shuttle and other orbital spacecraft re-enter at orbital speeds, closer to 25,000 km/h (16,000 mph) , using heat shields. SpaceShipTwo is furthermore designed to re-enter the atmosphere at any angle.[15] It will decelerate through the atmosphere, switching to a gliding position at an altitude of 24 km (15 mi), and will take 25 minutes to glide back to the spaceport.

SpaceShipTwo and White Knight Two are, respectively, roughly twice the size of the first-generation SpaceShipOne and mothership White Knight, which won the Ansari X Prize in 2004. SpaceShipTwo has 43 and 33 cm (17 and 13 in) -diameter windows for the passengers' viewing pleasure,[14] and all seats will recline back during landing to decrease the discomfort of G-forces.[16] Reportedly, the craft can land safely even if a catastrophic failure occurs during flight.[17] In 2008, Burt Rutan remarked on the safety of the vehicle:

This vehicle is designed to go into the atmosphere in the worst case straight in or upside down and it'll correct. This is designed to be at least as safe as the early airliners in the 1920s...Don’t believe anyone that tells you that the safety will be the same as a modern airliner, which has been around for 70 years.[15]

In September 2011, the safety of SpaceShipTwo's feathered reentry system was tested when the crew briefly lost control of the craft during a gliding test flight. Control was reestablished after the spaceplane entered its feathered configuration, and it landed safely after a 7-minute flight.[18]

Fleet and launch site[edit]

The launch customer of SpaceShipTwo is Virgin Galactic, who have ordered five vehicles.[19][20] The first two were named VSS (Virgin Space Ship) Enterprise[21] and VSS Voyager. As of August 2013, only VSS Enterprise has been flown;[22] VSS Voyager has yet to begin flight tests. The WhiteKnightTwo carrying SpaceShipTwo crafts will take off from the Mojave Air and Space Port in California during testing. Spaceport America – formerly Southwest Regional Spaceport, a US$212 million spaceport in New Mexico partly funded by the state government[23] – will become the permanent launch site when commercial launches begin.[13]


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 Javits Convention Center in New York.[24] The design of the vehicle was revealed to the press in January 2008, with the statement that the vehicle itself was around 60% complete.[13] On 7 December 2009, the official unveiling and rollout of SpaceShipTwo took place. The event involved the first SpaceShipTwo being christened by then-Governor of California Arnold Schwarzenegger as the VSS Enterprise.[25]

2007 test explosion[edit]

On 26 July 2007, an explosion occurred during an oxidizer flow test at the Mojave Air and Space Port, where early-stage tests were being conducted on SpaceShipTwo's systems. The oxidizer test included filling the oxidizer tank with 4,500 kilograms (10,000 lb) of nitrous oxide, followed by a 15-second cold-flow injector test. Although the tests did not ignite the gas, three employees were killed and three injured, two critically and one seriously, by flying shrapnel.[26]

Rocket engine[edit]

The hybrid rocket engine design for SpaceShipTwo has been problematic and caused extensive delays to the flight test program. The original rocket motor design was based on hydroxyl-terminated polybutadiene (HTPB) fuel and nitrous oxide oxidizer – sometimes referred to as an N2O/HTPB engine[27][28] – from 2009–early 2014. In May 2014, the engine design was switched from a HTPB to a polyamide fuel formulation.


Main article: RocketMotorTwo

Between 2005 and 2009, Scaled Composites conducted numerous small-scale rocket tests to evaluate SpaceShipTwo's engine design. After settling on the RocketMotorTwo hybrid rocket design, the company began performing full-scale hot-fire rocket tests in April 2009.[29] By December 2012, 15 full-scale tests had been successfully conducted,[29][30] and additional ground tests continued into March 2013.[31] In June 2012, the FAA issued a rocket testing permit to Scaled Composites, allowing it to begin SS2 test flights powered by RocketMotorTwo;[32] the first such powered flight took place on 29 April 2013.[33] The HTPB RocketMotorTwo design generated 60,000 lbf (270 kN) of thrust.[34]

2014 Change of fuel[edit]

In May 2014, Virgin Galactic announced a change to the fuel to be used in the SpaceShipTwo rocket engine. Rather than the rubber-based HTPB—HTPB engines had experienced serious engine stability issues on firings longer than approximately 20 seconds—the engine will now use a type of plastic called thermoplastic polyamide as the solid fuel. The plastic fuel is projected to have better performance (by several unspecified measures) and will allow SpaceShipTwo to make flights to a higher altitude.[35][36][37]

As of May 2014, the new engine has already completed full-duration burns of over 60 seconds in ground tests on an engine test stand.[36]

SpaceShipTwo test flights[edit]

Main article: VSS Enterprise
SpaceShipTwo in a captive flight configuration underneath White Knight Two, during the runway dedication of Spaceport America in October 2010. VMS Eve is shown carrying VSS Enterprise.
A view of the firing of SpaceShipTwo's rocket motors during its first powered flight in April 2013.

As of October 2014, SpaceShipTwo has conducted 54 test flights.[38] The spacecraft has used its "feathered" wing configuration during ten of these test flights.[38][39][40]

In September 2012, Virgin Galactic announced that the unpowered subsonic glide flight test program was essentially complete.[41] In October 2012, Scaled Composites installed key components of the rocket motor, and SpaceShipTwo performed its first glide flight with the engine installed in December 2012.[42][43]

The spacecraft's first powered test flight took place on April 29, 2013. Spaceshiptwo reached supersonic speeds in this first powered flight.[44][45] On September 5, 2013, the second powered flight was made by SpaceShipTwo.[46] The first powered test flight of 2014—and third overall—occurred January 10, 2014. The spacecraft reached an altitude of 22,000 metres (71,000 ft) (the highest to date) and a speed of Mach 1.4. The WhiteKnightTwo carrier aircraft released SpaceShipTwo (VSS Enterprise) at an altitude of 14,000 metres (46,000 ft) .[47]


SpaceShipTwo's total development costs were estimated at around $400 million in May 2011, a significant increase over the 2007 estimate of $108 million.[48]

Commercial operation[edit]

The duration of the flights will be approximately 2.5 hours, though only a few minutes of that will be in space. The price will initially be $200,000.[49] More than 65,000 would-be space tourists applied for the first batch of 100 tickets. 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.[50] By the start of 2011, that number had increased to over 400 paid customers,[51] and to 575 by early 2013.[52] In April 2013, Virgin Galactic announced that the price for a seat would increase 25 percent to $250,000 before the middle of May 2013,[52] and would remain at $250,000 "until the first 1,000 people have traveled, so that it matches up with inflation since [Virgin Galactic] started."[53]

Following 50–100 test flights, the first paying customers are expected to fly aboard the craft in 2014.[6] Refining the projected schedule in late 2009, Virgin Galactic declined to announce a firm timetable for commercial flights, but did reiterate that initial flights would take place from Spaceport America. Operational roll-out will be based on a "safety-driven schedule".[54] In addition to making suborbital passenger launches, Virgin Galactic will market SpaceShipTwo for suborbital space science missions.[54]

NASA sRLV program[edit]

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 is a part of the agency's Flight Opportunities Program. Virgin projects research flights with a peak altitude of 110 km (68 mi) and a duration of approximately 90 minutes. These flights will provide approximately four minutes of microgravity for research payloads. Payload mass and microgravity levels have not yet been specified.[3] The NASA research flights could begin during the test flight certification program for SpaceShipTwo.

Future spacecraft[edit]

In August 2005, the president of Virgin Galactic stated that if the suborbital service with SpaceShipTwo is successful, the follow-up SpaceShipThree will be an orbital craft. In 2008, Virgin Galactic changed their plans and decided to make it a high-speed passenger vehicle, offering transport through point-to-point suborbital spaceflight.[55]


While the first WhiteKnightTwo and the first SpaceShipTwo were built by Scaled Composites, The Spaceship Company has responsibility for the manufacture of the second WK2 aircraft and the second SS2 spacecraft for Virgin Galactic, as well as additional production craft as other customers for the vehicles emerge.[56] In October 2010, TSC announced plans to build three WhiteKnightTwo aircraft and five SpaceShipTwo spaceplanes.[57]


Sources: [58][59]

General characteristics

  • Crew: 2
  • Capacity: 6 passengers
  • Length: 18.3 m (60 ft)
  • Wingspan: 8.3 m (27 ft)
  • Height: 5.5 m (18 ft – rudders down)
  • Loaded weight: 9,740 kg (21,428 lb)
  • Powerplant: 1 × RocketMotorTwo liquid/solid hybrid rocket engine


See also[edit]


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  4. ^ Amos, Jonathan (8 December 2009). "Richard Branson unveils Virgin Galactic spaceplane". BBC News. Retrieved 23 March 2010. 
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External links[edit]