Virgin Galactic's pioneering spacecraft designed to take tourists into space crashed Friday in California, killing one of its two pilots and scattering debris across the desert.
Television images showed the wreckage of SpaceShipTwo, a test vehicle that flies to the edge of space, amid brush east of Mojave, a few hours' drive northeast of Los Angeles.
"Space is hard and today was a tough day," George Whitesides, CEO of Virgin Galactic told reporters at a media briefing a few hours after the crash.
"When we have a mishap from the test community, we find the test community is very small ... and we are human, and it hurts," added Stuart Witt, head of the Mojave Air and Space Port.
The incident is the econd disaster involving a US spacecraft this week, after an unmanned Orbital Science rocket carrying supplies to the International Space Station exploded after launch on Tuesday.
It is also a huge blow to British tycoon Richard Branson's long-held dream of offering the first passenger space flights, which have been snapped up by celebrities including Leonardo DiCaprio.
The Virgin chief said he was heading straight to the site, as the California Highway Patrol confirmed that one pilot had died and another was seriously injured and taken to hospital.
"Thoughts with all @virgingalactic ... I'm flying to Mojave immediately to be with the team," he wrote on Twitter. Whitesides later said that the globe-trotting tycoon was due in Mojave by Saturday morning.
The spaceship had been carried aloft on a bigger aircraft known as WhiteKnightTwo and then released for a test of its rocket engine above the Mojave desert, the latest in a series of tests.
Witt told reporters that WhiteKnightTwo took off at 9:20 am, and released SpaceShipTwo at an altitude of 45,000 feet, at 10:10 am, after 50 minutes of flight.
Two minutes later Witt, watching from the space port, said it became clear something had gone wrong, even though there was nothing obvious visually from the ground.
"If there was a huge explosion I didn't see it," he said, adding: "From my eyes and my ears I detected nothing that appeared abnormal."
The US air safety agency, the National Transportation Safety Board (NTSB), said it was sending a team to the site of the crash.
The flight—the 35th by SpaceShipTwo, according to Virgin Galactic's Twitter feed—involved the same configuration as previously, although the type of fuel was new, officials said.
More than 500 people have already reserved seats—and paid a deposit on the $250,000 ticket price—for a minutes-long suborbital flight on SpaceShipTwo, which can carry six passengers.
DiCaprio and fellow actors Ashton Kutcher and Demi Moore are among those already reported to have booked their place.
In May "Titanic" star DiCaprio auctioned off an invitation to join him on a trip with him into space, raising 700,000 euros ($876,000).
Private companies are rushing to fill the gap left by NASA, which ended its 30-year shuttle program in July with the completion of the final Atlantis mission to the International Space Station (ISS).
Analysts said the accident is a huge blow to the nascent industry.
"It's a setback for the tourism industry," said Marco Caceres, an analyst and director of space studies for the Teal Group, a defense and aerospace consultancy just outside of Washington, DC.
"You are not going to see any commercial space tourism flight next year or probably several years after that," he told AFP.
But Witt said the commercial space industry, and all the young entrepreneurs working in it, must move beyond Friday's tragedy. "My message to theme is stay the course," he said.
Whitesides echoed the sentiment, saying: "We are going to be supporting the investigation as we figure out what happened today. And we're going to get through it.
The future rests in many ways on hard days like these.
"We believe we owe it to the folks who were flying these vehicles .. to understand this and to move forward, which is what we'll do," he said.
Friday's incident is the second involving an American spacecraft this week, after the Orbital Science rocket exploded six seconds after launch on a resupply mission to the ISS.
Initial investigations into that explosion centered on the pair of rocket engines providing its thrust, which were made during the Soviet era and refurbished.
The Virgin crash also raised questions over a reality TV show, "Space Race."
The show, which was commissioned last year, pits contenders against each other to win a flight on the Virgin Galactic spacecraft, according to entertainment industry journal Variety.
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