Virgin Galactic’s SpaceShipTwo went supersonic over the Mojave desert during its first powered flight this morning, a major milestone for the company’s plans for commercial suborbital flights.

Sir Richard Branson’s spacecraft left the Mojave Air and Space Port in southern California on its first rocket powered flight not far from where the Bell X-1 piloted by the then Capt. Chuck Yeager first broke the sound barrier in 1947. Today’s flight is a big step forward for Virgin Galactic and paves the way for its first suborbital space flight test later this year. It’s been more than eight years since Virgin Galactic’s space tourism program began, and though progress has come slower than planned, Branson was nevertheless enthusiastic about the flight test.

“It marks the moment when we put together two key elements of our spaceflight system – the spacecraft and its rocket motor, which have both been tested extensively by themselves over several years,” Branson wrote on his blog after the flight. “And start the phase of testing that will demonstrate our vehicle’s ability to go to space (hopefully later this year).”

SpaceShipTwo is being flight tested by Scaled Composites, the company founded by aerospace pioneer Burt Rutan. Scaled designed and built the aircraft after SpaceShipOne became the first civilian aircraft to make a sub-orbital flight in 2004. SpaceShipTwo made its first glide flight back in 2010 and first flew with a rocket aboard in December.

Like SpaceShipOne, SpaceShipTwo uses a hybrid rocket motor with a solid rubber (strictly speaking, hydroxyl-terminated polybutadiene) fuel and liquid nitrous oxide as the oxidizer. The solid rubber fuel provides near instantaneous ignition and can be throttled by the pilot to control thrust.

For today’s flight, SpaceShipTwo was carried to about 47,000 feet by its mother ship, WhiteKnightTwo, being released at 7:48 a.m. PDT. Moments later pilots Mark Stucky and Mike Alsbury ignited the rocket engine and accelerated to Mach 1.2 as they climbed to over 55,000 feet in the blue Mojave sky. The rocket burn lasted just 16 seconds according to Virgin Galactic. Sub-orbital flights will need longer burns, likely close to the 80 or so seconds SpaceShipOne used to pass the 100 kilometer mark (~328,000 feet) internationally accepted as the (soft) edge of space. The final flight of SpaceShipOne included an 87 second burn that pushed the spaceship and pilot Brian Binnie to an altitude of 354,200 feet, beating the record for winged flight set by the North American X-15 in 1963.

In the video below, SpaceShipTwo can be seen during the release from WhiteKnightTwo when the pilots rise against the straps of their flight harnesses as they experience negative g-forces. A few seconds later when the rocket engine is ignited they experience an approximate 3 g force on their bodies – three times the force of gravity pushing them back, often referred to by pilots as “eyeballs in.” After 16 seconds of burn, the engine cuts out as planned and the pilots briefly experience “eyeballs out” negative g-forces due to the deceleration. Once settled into normal flight, SpaceShipTwo spent about 10 minutes gliding back to the runway in Mojave.

More than 500 people have signed up for sub-orbital rides aboard the six passenger SpaceShipTwo. The $200,000 tickets will give passengers a chance to float weightlessly for a few minutes while enjoying the view of the thin blue lens of the atmosphere sandwiched between the black sky of space and the desert landscape of the southwestern United States below.

Branson has said all along he plans on being on the first passenger flight, something he reiterated today after watching the flight, “like our hundreds of customers from around the world, my children and I cannot wait to get on board this fantastic vehicle for our own trip to space and am delighted that today’s milestone brings that day much closer.”

We’ll have updates throughout the day as Virgin Galactic releases more info. Stay tuned.