US authorities are investigating why Virgin Galactic’s space rocket crashed over California’s Mojave desert on a test flight.

One pilot died and the other was badly injured when SpaceShipTwo exploded shortly after take-off on October 31.

A National Transportation Safety Board (NTSB) team arrived in Mojave on November 1 and was heading to the crash site.

Virgin Group founder Richard Branson said he was “determined to find out what went wrong” and learn from the tragedy.

The dead pilot was named as 39-year-old Michael Alsbury. The pilot who survived Friday’s crash has not been identified.

Speaking at the at the Mojave Air and Space Port, where the craft was being developed, Richard Branson said “nobody underestimates the risks involved in space travel”.

SpaceShipTwo was flying its first test flight for nine months when it crashed shortly after take-off near Bakersfield (photo EPA)

Virgin had hoped to launch commercially in 2015. It has already taken more than 700 flight bookings at $250,000 each, with Richard Branson pledging to travel on the first flight.

“We owe it to our test pilots to find out what went wrong, and once we find out, if we can overcome it, we will make sure that the dream lives on,” Richard Branson added.

Richard Branson said Virgin Galactic and its partners had “been undertaking a comprehensive testing program for many years and safety has always been our number one priority”.

A team of between 13 and 15 NTSB investigators – including specialists in structures, systems, engines and vehicle performance – arrived in Mojave on Saturday morning and would begin on-site work later in the day, NTSB acting chairman Christopher Hart said.

Their work would include detailed examination of all available data, work at the crash site and interviewing witnesses, Christopher Hart said.

“This was a test flight and test flights are typically very well documented in terms of data,” he added.

Wreckage from the crash is scattered across a large area of the Mojave desert, north-east of Los Angeles. Police secured the site amid fears that some of the debris could be explosive.

SpaceShipTwo was flying its first test flight for nine months when it crashed shortly after take-off near Bakersfield.

In a statement, the company said SpaceShipTwo experienced “a serious anomaly” after the craft separated from its launcher, an aircraft called WhiteKnightTwo.

WhiteKnightTwo landed safely.

It later emerged that the space craft was burning a new type of rocket fuel never before used in flight, although officials said it had undergone extensive ground testing.

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