A suborbital passenger spaceship being developed by Richard Branson's Virgin Galactic company crashed during a test flight on Friday at the Mojave Air and spaceport in California, killing one crew member and seriously injuring the other, officials said.

The crash of the vehicle, undergoing its first powered test flight since January over the Mojave Desert, 150 kilometres north of Los Angeles, came days after another private space company, Orbital Sciences Corp, lost a rocket in an explosion moments after liftoff in Virginia.

Virgin Galactic SpaceShipTwo crash

The Virgin Galactic SpaceShipTwo exploded mid-flight, shortly after detaching from its carrier craft. (Kenneth Brown/Associated Press)

The back-to-back accidents dealt a considerable blow to the fledgling commercial space launch industry, which has been taking on more work traditionally done by the U.S. government while expanding for-profit space markets, including tourism.

Television footage of the Virgin Galactic crash site showed wreckage of the spacecraft lying in two large pieces on the ground, and the company said the spacecraft was destroyed. Kern County Sheriff Donny Youngblood said a debris field was spread over nearly two kilometres. 

Ken Brown, a photographer who witnessed the crash, told The Associated Press the spacecraft blew apart shortly after being released from a carrier 'mother ship.' 

One spaceship pilot was killed in the crash and his body was found in the wreckage, while the second pilot, who ejected and parachuted to the ground, survived with serious injuries, Youngblood said. The survivor was found nearly two kilometres from the main wreckage site, he said.

Both crew members were test pilots for Scaled Composites, the Northrop Gruman Corp subsidiary that designed and built the spacecraft for Virgin and lost three other employees in a July 2007 ground test accident during development of the ship's propulsion system.

Virgin Galactic SpaceShipTwo crash

Wreckage lies near the site where SpaceShipTwo fell back to Earth after exploding mid-flight. (Ringo H.W. Chiu/Associated Press)

Friday's crash occurred shortly after the craft, dubbed SpaceShipTwo, separated from the jet airplane that carried it aloft for its high-altitude launch, according to the Federal Aviation Administration.

Scaled Composites President Kevin Mickey told a news conference the ill-fated flight was the first using a new rocket fuel formula the company switched to in May. He said that formula "had been proven and tested on the ground" before Friday's test launch.

'Today was a tough day'

Stuart Witt, chief executive of the spaceport, said officials were not ready to "speculate on the cause" of the crash. The National Transportation Safety Board said it was sending one of its "go-teams" to investigate the accident.

Virgin Galactic SpaceShipTwo crash

Stuart Witt, CEO and General Manager of Mojave Air and Space Port, said at a press conference Friday that there was no pre-flight indications that anything was wrong with the spacecraft. (Ringo H.W. Chiu/Associated Press)

Branson said via Twitter that he was on his way to Mojave following the crash. "Thoughts with all @virgingalactic & Scaled," he tweeted referring to the company, Scaled Composites, which designed and built the spacecraft for Virgin.

When Virgin Group licensed the technology from Microsoft co-founder Paul Allen, who funded about $26 million for SpaceShipTwo's predecessor craft, Branson envisioned operating flights by 2007. In interviews last month, he talked about the first flight being next spring with his son.

Branson released a statement Friday night saying it was "among the most difficult trips I have ever had to make" but that he wants to be "with the dedicated and hardworking people who are now in shock at this devastating loss."

"Space is hard — but worth it," Branson wrote. "We will persevere and move forward together."

VIRGIN GALACTIC CRASH

George Whitesides, chief executive of Virgin Galactic, said he expected Branson to arrive in California by Saturday morning.

"Space is hard, and today was a tough day. We are going to be supporting the investigation as we figure out what happened today, and we're going to get through it," he told a news conference at the spaceport.

He added: "We believe we owe it to the folks who were flying these vehicles as well as the folks who have been working so hard on them, to understand this and to move forward, which is what we'll do."

More than 700 waiting to take flight

More than 700 people have paid or put down deposits to eventually fly aboard the spaceship, which is hauled to an altitude of about 13.7 kilometres (45,000 feet) and released by Virgin's White Knight Two carrier jet airplane.

The spaceship then fires its rocket motor to catapult it to about 100 kilometres (62 miles) above Earth, giving passengers a view of the planet set against the blackness of space and a few minutes of weightlessness.

Stephen Hawking, Justin Bieber, Ashton Kutcher and Russell Brand are among the celebrities to sign up for flights. Virgin Galactic reports taking deposits totalling more than $80 million from the 700 people. 

The vehicle is based on a prototype, SpaceShipOne, which 10 years ago won the $10 million Ansari X Prize for becoming the first privately developed manned spacecraft to fly in space.

"During the test, the vehicle suffered a serious anomaly resulting in the loss of SpaceShipTwo," Virgin said in a statement, adding: "We will work closely with relevant authorities to determine the cause of this accident and provide updates ASAP."

Virgin Galactic SpaceShipTwo Oct 31

Video by KABC TV Los Angeles shows wreckage of what is believed to be SpaceShipTwo after a crash in Southern California's Mojave Desert. (KABC TV/Associated Press)

In May, Scaled Composites, a subsidiary of Northrop Grumman Corp, switched to an alternative plastic-type of fuel grain for the hybrid rocket motor.

The crash was the second accident this week involving a commercial U.S. space company. On Tuesday, an Antares rocket built and launched by Orbital Sciences exploded 15 seconds after liftoff from Wallops Island, Virginia, destroying a cargo ship bound for the International Space Station.

Plans for more spacecraft

Friday's crash was a major setback for Virgin Galactic, a U.S. offshoot of billionaire Branson's London-based Virgin Group. The company was aiming to make the world's first commercial suborbital space flights with SpaceShipTwo, a six-passenger, two-pilot spacecraft.

The flight was to have been the first in a series of test flights leading up to Virgin Galactic's first flight beyond Earth's atmosphere.

Virgin ultimately was planning to add four more suborbital spacecraft to its fleet, along with a second White Knight carrier jet. Plans call for the fleet to fly out of a new commercial spaceport in Las Cruces, New Mexico, once the company completes all test flights and is certified for passenger service to begin.

Virgin Galactic's Whitesides told a Toronto space conference earlier this month that a second spacecraft was already under construction and about 60 per cent complete.

Other companies developing passenger suborbital spacecraft include privately owned XCOR Aerospace, which is building a two-person space plane called Lynx, and Blue Origin, a startup space company owned by Amazon.com Inc founder Jeff Bezos.

Virgin Galactic also plans to use its White Knight Two carrier jets to launch small satellites and payloads into orbit.

With files from The Associated Press