Virgin Galactic will use technologies developed and tested on SS1 in its designs for WK2 and SS2.
Like WhiteKnightOne, WK2 is made of carbon composites -- it's the world's largest all carbon-composite aircraft. It's powered by four Pratt and Whitney PW308A turbo jet engines and has two crew compartments on either side of the point where SS2 attaches to its underside. WK2 can lift and launch SS2 as well as other payloads, such as small unmanned rockets capable of carrying small satellites into low Earth orbit. WK2 will also serve as a training vehicle for the SS2 astronauts and pilots, training them for weightlessness by flying parabolic flight paths (see How Zero-gravity Flights Work and How Weightlessness Works). The WK2 aircraft is near completion and expected to begin flight tests in summer 2008.
SS2 is 60 feet (18.3 meters) long (more than twice the length of SpaceShipOne) and 7.5 feet (2.3 m) wide. It has a wing span of 27 feet (8.2 m), a tail height of 15 feet (4.6 m) and can carry two pilots and six passengers. The passenger cabin is 12 feet (3.7 m) long and 7.5 feet (2.3 m) wide. Virgin Galactic compares SS2 to a Gulfstream business jet.
The SS2 features:
- A carbon-composite double hull made of carbon sandwich panels with a honeycomb core. The hull enables a fully pressurized cabin so that passengers and pilots won't have to wear bulky space suits.
- A hybrid rocket motor that's part solid rocket and part liquid. It uses nitrous oxide oxidizer and tire rubber fuel. The nitrous oxide self-pressurizes and is stored in a tank behind the cabin (the tank makes up the cabin's rear bulkhead). The case, throat and nozzle (CTN) are made of solid rubber fuel. A main valve and igniter lights the nitrous oxide as it flows over the rubber fuel and out the nozzle. The CTN burns out and can be replaced for the next flight.
- Double-pane windows that are capable of withstanding pressure differences across the cabin wall. They'll provide numerous views of the Earth and space.
- Thrusters (pressurized containers of air) that help the spacecraft pitch, roll and yaw
- Rudders and elevons, flight control surfaces that will help SS2 maneuver while gliding for landing
- Two hatches -- one for entry and exit and another for emergency exit
- A feather mechanism (pneumatically operated controls that rotate the wings). Feathering places the wings in an upward position for re-entry. The feathered position produces drag, slows the spacecraft and allows it to gently fall back through the upper parts of the Earth's atmosphere like a badminton shuttlecock. This technique reduces the g-forces and heat buildup of re-entry.