Lauer himself homed in on a question many have discussed since the accident. Test flight and space travel has always been dangerous, are the risks worth it when the object is an expensive thrill ride rather than the advancement of science? Mid-air breakup: Sheriff's deputies look at a piece of debris near the crash site of Virgin Galactic's SpaceShipTwo near Cantil, California. Credit:Reuters "Absolutely it is worth the risks," said Branson without hesitation, adding though that his program was about more than the $200,000 space flight that is being marketed to rich adventurers. He said it was not just about giving the "millions of people who would like to" a chance to see space, but about launching "massive arrays" of satellites and mastering sub-orbital flight for passengers here on Earth. "It is a grand program," he said. Not everyone is convinced, and it helps to have some understanding of the technology Branson's Virgin Galactic was using to understand why.

To reach space, Virgin Galactic's spacecraft was to have been hauled 15 kilometres into the air by another aircraft before it was released, fired its own rockets and reached an altitude of 100 kilometres, the outside boundary of Earth's atmosphere. Our theory: US transportation officials say the co-pilot of the Virgin Galactic space plane that crashed unlocked its wing tip "feathers" early and that pilot error has not been ruled out. At that point, passengers would experience a few minutes of weightlessness and a view of Earth before the craft flipped back it wings into a "feathered" position, to slow the craft down for a glide home to its base. This is essentially the same technology the United States Air Force was experimenting with even before NASA was created, says Jonathan McDowell, an astronomer at the Harvard-Smithsonian Centre for Astrophysics. It is not the sort of technology that could be harnessed to deploy satellites or resupply a space station, he says, and he agrees with critics who describe the venture as an expensive roller-coaster ride.

But he points out that should Branson succeed in commercialising space flight, he would have the infrastructure in place to commit to further advances. At a press conference on Sunday night, the National Transportation Safety Board, which is leading the investigation, said there were early indications that the feathering device had been deployed too early, causing the aircraft to break apart. The device is normally deployed by one of the pilots unlocking the mechanism and then in a second action moving a handle into position. Branson seemed to embrace this early explanation on Monday morning, even to the point of suggesting that pilot error might have been a factor, telling the Today Show: "That is something which is easy to fix and we can make absolutely certain that it cannot be done again in the future." There had been earlier speculation that the accident might have been caused by the craft's rocket engine or its fuel source. Earlier, Branson denied an explosion brought down the craft. Either of these explanations would set back the program far longer, Dr McDowell says. Dr McDowell said while it was too early to know what went wrong, it is conceivable that the aircraft had lost stability and the pilots deployed the feathering device in an effort to regain control. A test pilot flying an earlier iteration of the craft once deployed the feathering device to control a spin, he said.

Virgin Galactic and Branson have faced criticism in the past for their aggressive test schedule and it use of nitrous oxide as fuel in the past. Indeed the first three deaths in the commercial space industry were engineers killed testing these rocket engines on the ground in 2007. Carolynne Campbell, an expert with the Netherlands-based International Association for the Advancement of Space Safety, also on Sunday told AFP that she and other experts "were concerned about what was going on at Virgin Galactic". "I warned them … that the rocket motor was potentially dangerous," she said. Should the disaster turn out to have been caused by the feathering system being deployed too early rather than the result of a more fundamental engineering problem, Virgin Galactic could resume test flights as soon as the company's new spacecraft is completed, Dr McDowell says. A second SpaceShipTwo is understood to be halfway through construction.

"They have been at this for a long time, and every year they say passenger flights are going to start the next year," he says. "They give the impression that they are pushing forward very fast."