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Virgin Galactic 'feathering' function activated early, say crash investigators
Virgin Galactic exploded seconds after 'feathering' function was activated
(35 minutes later)
US investigators say that a function designed to help Virgin Galactic’s crashed space plane descend deployed early during the accident that killed one of its pilots on Friday – and that the craft’s fuel tanks and engine were found intact.
Virgin Galactic’s space plane broke apart in mid-air seconds after its re-entry system deployed prematurely in an accident on Friday that killed one of its pilots and left another seriously injured, US crash investigators have said.
Fifteen federal US investigators have been combing the site of the fatal crash in California’s Mojave desert, as questions surfaced about the unconventional fuel propulsion system used to blast the craft up to space.
SpaceShipTwo (SS2) was equipped with a “feathering system” to reduce its speed and stabilise its descent on return to Earth, but investigators found that the mechanism was activated before the space plane had reached the right speed during Friday’s test flight.
The head of the National Transportation Safety Board (NTSB), the agency leading the examination of the crash, said on Sunday they had recovered the fuel tanks and engine, which indicated no explosion.
When the feathering system is deployed, the space plane’s twin tail booms rotate forwards and upwards, dramatically increasing aerodynamic drag and making the craft fall like a shuttlecock.
SpaceShipTwo (SS2), the plane on which the Virgin boss Sir Richard Branson has pinned his hopes of sending commercial passengers to the edge of space at a cost of $250,000 (£156,000) each, broke up during a test flight at about 45,000ft on Friday. The pilot, Peter Siebold 43, managed to parachute to the ground and was described as alert though with serious injuries; the co-pilot, Michael Alsbury, 39, was killed.
Christopher Hart, the acting chairman of the US National Transportation Safety Board, told a press conference on Sunday night that the co-pilot, Michael Alsbury, had unlocked the feathering system, but that the second stage of the process, which moves the wings into the feathering position, happened “without being commanded”.
Investigators have warned it could take up to a year for the full report into the crash to be completed. One area of inquiry that has already been flagged up is the relatively new hybrid propulsion system that was used in Friday’s flight: nitrous oxide and plastic fuel, in contrast to the carbon-based fuels that have powered most rockets for decades.
“After it was unlocked, the feathers moved into the deployed position and two seconds later we saw disintegration,” he said.
The NTSB’s acting chairman, Christopher Hart, said that while no cause for Friday’s crash of SpaceShipTwo had been determined, investigators found the “feathering” system which lifts and rotates the tail to create drag was activated before the craft reached the appropriate speed.
“Normal launch procedures are that after the release, the ignition of the rocket and acceleration, that the feathering devices are not to be moved – the lock/unlock lever is not to be moved into the unlock position – until the acceleration up to Mach 1.4,” he added. “Shortly after the feathering occurred, the telemetry data terminated and the video data terminated.”
The system requires a two-step process to deploy. Hart said the co-pilot unlocked the system but the second step occurred “without being commanded”.
But Hart stresssed that the premature deployment of the space plane’s feathering system was “a statement of fact and not a statement of cause”. Investigators could take many more months to reach firm conclusions over the cause of the accident.
Hart said the investigation was months from being completed, and pilot error and mechanical failure were among many things being looked at.
Asked whether investigators were “edging” towards the possibility of pilot error, he added: “We’re not edging towards anything. We’re not ruling anything out. We’re looking at all of these issues to determine what was the root cause of this mishap. We are looking at a number of possibilities including that possibility (pilot error).”
Hart also said the debris suggested a breaking apart in flight.
“We are a long way from finding cause. We still have months and months of investigation to do,” Hart said.
“The debris field indicates an in-flight breakup,” he told Reuters. “We’ll know that for certainty when we look at all the sources we have.”
Fifteen federal US investigators have been combing the site of the fatal crash in California’s Mojave desert. On Sunday, the space plane’s fuel tanks and engine were found intact, contradicting earlier claims that SpaceShipTwo had exploded.
In a statement, Virgin Galactic said it was “dedicated to opening the space frontier, while keeping safety as our ‘North Star’. This has guided every decision we have made over the past decade, and any suggestion to the contrary is categorically untrue.
The space plane on which the Virgin boss Sir Richard Branson has pinned his hopes of sending commercial passengers to the edge of space – at a cost of $250,000 (£156,000) each – broke up during a test flight at about 45,000ft on Friday. The pilot, Peter Siebold 43, managed to parachute to the ground and was described as alert though with serious injuries; the co-pilot, Michael Alsbury, 39, was killed.
“Everything we do is to pursue the vision of accessible and democratized space – and to do it safely ... Now is not the time for speculation.”
Virgin Galactic has denied reports that it ignored safety warnings ahead of Friday’s test flight crash. “At Virgin Galactic, we are dedicated to opening the space frontier, while keeping safety as our ‘North Star’. This has guided every decision we have made over the past decade, and any suggestion to the contrary is categorically untrue.”
Rocket engineers and safety experts have been warning for at least a year about the potential instability of nitrous oxide. Carolynne Campbell, a rocket engineer who is the lead expert on hybrid propulsion systems for the International Association for the Advancement of Space Safety (IAASS) told the Guardian that when it was used by dentists in its commonly-known form of “laughing gas”, nitrous oxide was “mild, gentle stuff”. In the highly dynamic environment of a rocket engine, though, it was “extremely unpredictable – it has a bit of a devil in it”.
In an interview with Sky News, Branson said: “We’ve spent many, many years building a spacecraft, a mothership, a space port, that I think can do the job and do the job safely. We will not start taking people until we’ve finished a whole massive series of test flights and until myself and my family have gone up, and until we feel that we can safely say to people ‘we’re ready to go’.”
Campbell pointed out that as recently as six months ago the Virgin Galactic website was describing nitrous oxide as “benign” and “stable” yet the gas was a factor in the 2007 explosion at the Virgin Galactic spaceport in which three workers died.
“We need to be absolutely certain our spaceship has been thoroughly tested – and that it will be – and once it’s thoroughly tested and we can go to space, we will go to space. We must push on. There are incredible things that can happen through mankind being able to explore space properly,” he added.
“They knew that three people were killed by this stuff, and yet they persisted in presenting it as safe, stable and benign,” said Campbell, speaking before the NTSB said that the fuel tanks were discovered intact.
Geoff Daly, a US-based British rocket scientist, who has been highly critical of the Virgin Galactic space tourism project, said nitrous oxide – used in small quantities in drag racing – is uncharted territory when used in large amounts. SpaceShipTwo’s tank was believed to have carried 11,000-12,000lbs of the gas.
“It’s still very poorly understood in large quantities … The temperature of the fuel is critical,” said Daly, who had sent several emails to officials at the Federal Aviation Authority (FAA) last year, when he warned of another disaster if test flights were given the go-ahead.
Daly also alleged that there were “fundamental design flaws” in the rocket system. “The delivery system is solid, the motor is bolted to the fuel tanks. There is no flexibility in the tank and motor, any vibration can result in the fracture and failure of the engine system.”
Speaking at the scene of the crash on Saturday, Branson said the focus was now on finding out what had had happened on Friday. But he added that “once we find out what went wrong, if we can overcome it, we will make absolutely certain that the dream lives on”.
Friday’s launch was the fourth powered flight for SS2 and was intended to test how the space plane fared on re-entry at supersonic speeds rather than to monitor the new fuel or the performance of the rocket on the way up.
Friday’s launch was the fourth powered flight for SS2 and was intended to test how the space plane fared on re-entry at supersonic speeds rather than to monitor the new fuel or the performance of the rocket on the way up.
The flight occurred in the context of very ambitious targets set by Virgin Galactic, that had been aiming to premier the first commercial flights as early as next spring. The desire to make the venture commercially viable carried with it huge engineering challenges.
The flight occurred in the context of very ambitious targets set by Virgin Galactic, which had been aiming to premier the first commercial flights as early as next spring. The desire to make the venture commercially viable carried with it huge engineering challenges.
Prime among those was to design a spacecraft capable of carrying six fee-paying passengers and two pilots as high as the edge of Earth’s atmosphere, the notional marker called the Karman Line, some 100km above sea level. Not only that, the enormous ticket price paid by the citizen astronauts on board had to be rewarded with a view back to Earth and its hazy blue atmosphere and the experience of weightlessness.
Prime among those was to design a spacecraft capable of carrying six fee-paying passengers and two pilots as high as the edge of Earth’s atmosphere, the notional marker called the Karman Line, some 100km above sea level. Not only that, the enormous ticket price paid by the citizen astronauts on board had to be rewarded with a view back to Earth and its hazy blue atmosphere, and the experience of weightlessness.
A whiteboard in Virgin Galactic’s London offices illustrated the basic thinking behind the project. “Design challenge: we wanted ROOM to enjoy weightlessness and WINDOWS,” it says besides hand-drawn sketches of a person floating in an astronaut’s suit and a round window looking down on Earth.
In an interview with the Guardian two weeks ago, Virgin Galactic’s chief executive George Whitesides said the new hybrid of nitrous oxide and plastic fuel had passed its crucial ground tests and was then undergoing “qualification tests” to prove it would perform predictably.
“In qualification tests you are proving to yourself that you can build it the same every time and that when you fire it it does the same thing every time. So that’s what we’re doing now,” he said.
In order to reach the edge of Earth’s atmosphere, SS2 would need to fire its engine for between 55 to 60 seconds. Ground tests had shown it could be safely fired for 70 seconds, Whitesides said.
According to one eye witness, Ken Brown, SS2’s engine had only been running for between 12 and 20 seconds before the craft appeared to catch fire and then broke up. At this stage, it is unclear whether it was the engine or the craft itself which failed.
There were also reports that three different types of fuel tank had been recovered from the crash site over the weekend, suggesting the rocket might have had additional layers of complexity in its fusion of the fuels.
SS2’s predecessor, SpaceShipOne, travelled to the edge of space twice in two weeks, returning to Earth safely on both occasions, 10 years ago. But the smaller craft could only carry two astronauts – not sufficient to make it commercially viable.
SS2’s predecessor, SpaceShipOne, travelled to the edge of space twice in two weeks, returning to Earth safely on both occasions, 10 years ago. But the smaller craft could only carry two astronauts – not sufficient to make it commercially viable.
Will Whitehorn, former president of Virgin Galactic, rejected any suggestion that the project had been rushed. “This is nonsense. The project started in 2004 … this is the longest test flight in the commercial sector in history.”
Will Whitehorn, former president of Virgin Galactic, rejected any suggestion that the project had been rushed. “This is nonsense. The project started in 2004 … this is the longest test flight in the commercial sector in history.”
Whitehorn also questioned whether the rocket had exploded. “I don’t know the cause, but looking at the pictures, the nitrous oxide tanks are still intact. An aircraft breaking up is something completely difficult. The National Transportation Safety Board will begin producing interim evidence in the next few days that will eliminate some of the assumptions being made without basis in fact.”
• This article, including the headline, which highlighted the questions over the new fuel mix used on SS2, were updated after the NTSB announced that the fuel tanks were discovered intact.
• This article, including the headline, which highlighted the questions over the new fuel mix used on SS2, were updated after the NTSB announced that the fuel tanks were discovered intact.
