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Sir Richard Branson and Burt Rutan unveil SpaceShipTwo and WhiteKnightTwo
Sir Richard Branson (left) and Burt Rutan (right) discussed details of Virgin Galatic's spaceline and gave the public its first look at SpaceShipTwo and WhiteKnightTwo during the unveiling at the Hayden Planetarium in New York City (photo by Dan Linehan).

SpaceShipTwo and WhiteKnightTwo Designs Unveiled
by Dan Linehan
On January 23, 2008, nearly three and a half years after the announcement of an agreement between Virgin Galactic and Scaled Composites to build a fleet of passenger-carrying spacecraft for a commercial spacelines, the designs of SpaceShipTwo and WhiteKnightTwo were unveiled to the world. Though both vehicles share some similarities to their predecessors, each had surprising differences—even compared to Virgin Galactic's previously released conceptual drawings, as shown below.

Early concepts of SpaceShipTwo and WhiteKnightTwo
Released well before the unveiling, this conceptual drawing showing SpaceShipTwo and WhiteKnightTwo reveals their similarities to SpaceShipOne and White Knight (Virgin Galactic).

Passengers will face a maximum g-force of 3.5 g on boost and 6 g on reentry, and will experience about 4.5 minutes of weightlessness. The price tag for the 2 hour ride to space, wheels up to wheels down, is $200,000, and there are more than 200 astronauts-in-waiting who have already paid a combined deposit in excess of $30 million.

The Virgin Spaceship (VSS) Enterprise will be the first of 5 SpaceShipTwo's to fly six passengers and two pilots to a suborbital altitude of "at least" 110 kilometers (68 miles). However, this altitude seems a bit low considering the last flight of SpaceShipOne reached 112 kilometers (70 miles). It had been reported earlier by the BBC that the altitude would be between 135–140 kilometers (84–87 miles), which seems much more reasonable. The SpaceShipTwo prototype, designated by Scaled Composites as Model 339, is 60% complete and will begin flight testing at the end of 2008 if all goes as per plan.

SpaceShipTwo with its feather up
The current design of SpaceShipTwo shown in its feathered configuration (Virgin Galactic).

At 60 feet in length, SpaceShipTwo is slightly more than twice the length of SpaceShipOne. The fuselage and windshield of SpaceShipTwo take on a much more conventional shape than that of the bullet shape and array of circular windows of SpaceShipOne. The circular windows have found their place on SpaceShipTwo, although they now provide the view for the passengers in the 12-foot-long cabin.

SpaceShipOne and SpaceShipTwo Size Comparison
SpaceShipOne SpaceShipTwo
  Length (ft) 28 60
  Wingspan (ft) 16.4 27
  Width (ft) 27 42
  Height (ft) 8.8 15
  Cabin diameter (ft) 5 7.5

As shown above, SpaceShipTwo also employs a feather for safe reentry into Earth's atmosphere. The feather extends up and down similarly to how SpaceShipOne's operated. However, the forward section of each tail boom points downward below the pivot axis. This change may have been necessary to act as a counterbalance for the large feather. It wouldn't make sense to have something of only aesthetic value in such a critical position. After all, the spacecraft reenters on its belly, so any protuberances would be subject to high degrees of heating and require suitable thermal protection.

Lifted to launch altitude by White Knight, SpaceShipOne then dropped free and fired its rocket engine.
Lifted to its launch altitude of about 47,000 feet, SpaceShipOne then dropped free of White Knight and ignited its hybrid rocket engine (© 2004 Mojave Aerospace Ventures, LLC, Photo by David M. Moore).

To improve stability, SpaceShipTwo uses a low-wing configuration as opposed to the high-wing of SpaceShipOne, as shown above. This also changes the look substantially. All the control surfaces appear to be located on the tail booms as with SpaceShipOne, although there is an extra inboard horizontal stabilizer on each tail boom.

WhiteKnightTwo carries SpaceShipTwo between its two fuselages
WhiteKnightTwo, a twin-hull design, carries SpaceShipTwo centered underwing between its two fuselages (Virgin Galactic).

Perhaps the biggest surprise turned out to be the configuration of WhiteKnightTwo (Model 348). However, the name "WhiteKnightTwo" may not be its final moniker. Early conceptual drawings show SpaceShipTwo and WhiteKnightTwo stacked, fuselage under fuselage, as were SpaceShipOne and White Knight. This was an unlikely configuration for the new vehicles because of factors such as clearances since they are so much larger. Stacked but top-launched seemed like a good possibility. But Rutan is renown for coming up with unconventional approaches and designs that people just don't see coming. WhiteKnightTwo's twin-hull design gives plenty of room for SpaceShipTwo under its 140-foot-long wing.

Each fuselage has a cabin interior just like SpaceShipTwo so that passengers on deck can get a bit of training or observers can get a great view of the separation and boost. But only the starboard fuselage has a cockpit used to fly WhiteKnightTwo.

As opposed to the rebuilt, jet-trainer engines used in White Knight, the new carrier aircraft has four top-of-the-line Pratt and Whitney jet engines. This alleviates the performance headaches not uncommon to White Knight and also gives a good measure of redundancy. The decision to have four engines verses two engines could prove to be important for more than just redundancy, though. If WhiteKnightTwo in its current configuration had only one engine per wing and an engine failure occurred, then the resulting thrust imbalance could potentially cause aerodynamic and structural problems.

SpaceShipTwo will launch from Spaceport America in New Mexico
To be located in the desert of New Mexico and be designed to resemble a giant eye
when viewed from the sky, Spaceport America will operate Virgin Galactic's fleet of
5 SpaceShipTwo's and 2 White Knight Two's (Virgin Galactic).

WhiteKnightTwo is 80% complete, so it will be first to begin flight testing, which is likely to start this summer. The first commercial flights will occur in the 2009–2010 timeframe and are scheduled to launch from Spaceport America in New Mexico.

SpaceShipOne: An Illustrated History by Dan Linehan with foreword by Arthur C. Clarke Burt Rutan's Race to Space: The Magician of Mojave and his Flying Innovations by Dan Linehan with foreword by Mike Melvill