WhiteKnightTwo is a dual-hull quad-engine aircraft roughly three times larger than the original WhiteKnight. WK2 is the world's first all-composite full-sized aircraft. Everything apart from the engines and landing gear is constructed from ultra-lightweight composite materials.
Virgin Galactic expects to fly its first commercial space flights somewhere between 2009 and 2011.
Virgin galactic pictures
The most important thing is that is has no boom, the engines are on the outside. Any kind of payload can be put to it and have no interference with the cabin or the engines. WK2 can launch a light satellite at a much reduced cost over what is being done now with competing systems. WK2 is actually is large enough if you build a lightweight mercury capsule you can put a man in orbit.
WK2 will be an aerobatic aircraft, and will provide preview flights offering several seconds of weightlessness, before the actual suborbital event. It will have a service ceiling of about 60,000 ft or 18km, offering a dark blue sky to passengers.
White Knight Two has a twin boom with two jet engines per hull. One hull is an exact replica of that of SpaceShipTwo (to allow tourist training), and the other will carry cut-rate day-trippers into the stratosphere.
Scaled composites site