Virgin Galactic has largely finished subsonic and unpowered flight tests of SpaceShipTwo, the vehicle that will bring tourists into suborbital space for several minutes of weightlessness.

"Essentially we've finished subsonic flight tests of SpaceShipTwo," says George Whitesides, president of Virgin Galactic. "We've explored the envelope in a way that we now feel fairly comfortable that we're ready for the next stage, from an aerodynamics perspective."

SpaceShipTwo will remain on the ground for several months as the vehicle's hybrid liquid/solid rocket engine is installed. "This is the main integration of rocket motor components into the vehicle," says Whitesides.

"We won't go straight from, put the hatch back on, zip it up, and the next flight will be a powered flight," Whitesides remarks. "It will be, we'll zip it up, take it up, release it, see if everything's still gliding just the way we like it. Then we'll take it up and do some non-ignition tests of the rocket motor."

 SpaceShipTwo mounted to WhiteKnightTwo carrier veh

 ©Virgin Galactic

Once Virgin Galactic is satisfied the vehicle and rocket motor function will function as expected, subsequent flights will see the hydroxyl-terminated polybutediene/nitrous oxide rocket ignited. The first powered flight may also be the first supersonic one.

"The variable there is just how long we decide to fire the motor on that first flight. The uncertainty is just that we're baselining a pretty short burn, but even on a short burn it will get up to supersonic pretty quickly," says Whitesides. "It is possible but it has not yet been decided."

Source: Flight International