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Virgin Galactic boss said new fuel had passed crucial tests Virgin Galactic boss said new fuel had passed crucial tests
(about 2 hours later)
When Virgin Galactic’s chief executive was planning what turned out to be SpaceShipTwo’s fatal last flight, the challenge that concerned him most was not the performance of the new fuel his engineers had been testing, but the rocket’s return to Earth’s atmosphere.When Virgin Galactic’s chief executive was planning what turned out to be SpaceShipTwo’s fatal last flight, the challenge that concerned him most was not the performance of the new fuel his engineers had been testing, but the rocket’s return to Earth’s atmosphere.
George Whitesides’ big fear was that his craft might catch fire on re-entry, not on its way into space. Compared with Nasa’s now-retired Shuttle, SS2 has light thermal protection. Rather than being coated in combustion-proof tiles, it has strips of thermal material on its nose and wing edges only, where the friction is greatest. But as we now know, SpaceShipTwo never began its return journey. The craft broke up at about 45,000ft over the Mojave desert in California, killing one crew member. George Whitesides was using SS2’s fourth powered flight to monitor how it performed on re-entry under supersonic speeds. Its tailfins fold into what Galactic calls a “feathered” configuration, and the craft is designed to fall back to earth roughly belly-first. Compared to Nasa’s now-retired Shuttle, it is designed to descend at slower speeds.
For this reason, SS2 has light thermal protection. Rather than being coated in combustion-proof tiles, it has strips of thermal material on its nose and wing edges only, where the friction is greatest. But as we now know, SS2 never began its return journey. The craft broke up at about 45,000ft over the Mojave desert in California, killing one crew member.
On a visit to London in the first week of October to reassure customers, investors and the media, Whitesides was keen to emphasise that the new fuel had passed its crucial ground tests.On a visit to London in the first week of October to reassure customers, investors and the media, Whitesides was keen to emphasise that the new fuel had passed its crucial ground tests.
SS2 does not rely on traditional carbon-based rocket fuel. It uses a cheaper and, according to Whitesides, simpler alternative – plastic and laughing gas.SS2 does not rely on traditional carbon-based rocket fuel. It uses a cheaper and, according to Whitesides, simpler alternative – plastic and laughing gas.
The craft carries a tank of the gas – properly known as nitrous oxide – and grains of plastic pressed into the shape of a hollow tube. When the engine is fired, the gas passes at great speed through a valve and then through the plastic tube, causing it to catch fire. The craft carries a tank of the gas – properly known as nitrous oxide – and plastic moulded into the shape of a hollow tube. When the engine is fired, the gas passes at great speed through a valve and then through the plastic tube. Igniters spark the flame, and the nitrous oxide provides the oxygen needed for the plastic in the tube to catch fire.
The decision to replace the original rubber fuel with plastic was taken in May. Since then, the new engine had undergone extensive tests. When the Guardian met Whitesides, development testing, in which parts are changed, was complete. Virgin was conducting qualification tests – to ensure the engine performed the same every time. The decision to return to the air would have been taken only after these were completed satisfactorily.The decision to replace the original rubber fuel with plastic was taken in May. Since then, the new engine had undergone extensive tests. When the Guardian met Whitesides, development testing, in which parts are changed, was complete. Virgin was conducting qualification tests – to ensure the engine performed the same every time. The decision to return to the air would have been taken only after these were completed satisfactorily.
“What we are in now is qualification tests,” said Whitesides. “In [the] development test, you are changing things, in [the] qualification test 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.”“What we are in now is qualification tests,” said Whitesides. “In [the] development test, you are changing things, in [the] qualification test 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.”
When asked whether he was confident the new engine would take SS2 into space, Whitesides replied: “Yes. It’s a simple system and should be very reliable once it’s in operation. Liquid fuel engines have a higher part count and in general the higher the part count, the higher the potential for failures. A simpler system should be safer.”When asked whether he was confident the new engine would take SS2 into space, Whitesides replied: “Yes. It’s a simple system and should be very reliable once it’s in operation. Liquid fuel engines have a higher part count and in general the higher the part count, the higher the potential for failures. A simpler system should be safer.”
In order to reach the edge of Earth’s atmosphere, the notional marker called the Karman line some 100,000km (62,000 miles) above sea level, SS2 would need to fire its engine for between 55 and 60 seconds. Ground tests had shown it could be safely fired for 70 seconds, Whitesides said. In order to reach the edge of Earth’s atmosphere, the notional marker called the Karman line some 100km (62 miles) above sea level, SS2 would need to fire its engine for between 55 and 60 seconds. Ground tests had shown it could be safely fired for 70 seconds, Whitesides said.
According to one witness, SS2’s engine had only been running for 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 that failed. According to one witness, 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 that failed.
Whitesides’ comments two weeks ago made it clear that thermal protection, and not the height – or apogee – reached by the craft, was his main concern.Whitesides’ comments two weeks ago made it clear that thermal protection, and not the height – or apogee – reached by the craft, was his main concern.
“From a test flight perspective, I’m less focused on the apogee, although the outside world is focused on the apogee. What I’m focused on is supersonic re-entry, coming down in the feather configuration into the atmosphere and breaking the speed of sound on the way down.“From a test flight perspective, I’m less focused on the apogee, although the outside world is focused on the apogee. What I’m focused on is supersonic re-entry, coming down in the feather configuration into the atmosphere and breaking the speed of sound on the way down.
“We’ve done it on the way up; we haven’t done it on the way down so we need to do that. Analytically, our models look good, but what is test flight? It is proving your analogue models. We need to get through peak re-entry heating.”“We’ve done it on the way up; we haven’t done it on the way down so we need to do that. Analytically, our models look good, but what is test flight? It is proving your analogue models. We need to get through peak re-entry heating.”
The irony is that SS2’s predecessor, SpaceShipOne, travelled to the Karman line twice in two weeks, returning to Earth safely on both occasions, a decade ago. But the smaller craft could only carry two astronauts. In order to make his space venture commercially viable, Sir Richard Branson needed a craft that could carry six passengers and two pilots.The irony is that SS2’s predecessor, SpaceShipOne, travelled to the Karman line twice in two weeks, returning to Earth safely on both occasions, a decade ago. But the smaller craft could only carry two astronauts. In order to make his space venture commercially viable, Sir Richard Branson needed a craft that could carry six passengers and two pilots.
But these were not the only changes. As an illustration on a whiteboard in Virgin Galactic’s London office shows, the craft needed to be large enough to let its paying passengers experience the joys of zero gravity, with plenty of room to move around the cabin. And it needed windows, so that the citizen astronauts who had paid $250,000 (£156,000) a seat could gaze back at the Earth and its hazy blue atmosphere.But these were not the only changes. As an illustration on a whiteboard in Virgin Galactic’s London office shows, the craft needed to be large enough to let its paying passengers experience the joys of zero gravity, with plenty of room to move around the cabin. And it needed windows, so that the citizen astronauts who had paid $250,000 (£156,000) a seat could gaze back at the Earth and its hazy blue atmosphere.
These changes, it seems, made all the difference. In the 10 years since SpaceShipOne made its record-breaking flights, its successor craft has been unable to make it as far as the Karman line. The question now is whether it ever will.These changes, it seems, made all the difference. In the 10 years since SpaceShipOne made its record-breaking flights, its successor craft has been unable to make it as far as the Karman line. The question now is whether it ever will.