Virgin Galactic SpaceShipTwo (SS2) continues to inch toward a full suborbital test flight with its third supersonic test carried out Friday morning. The SS2 rocket engine fired for 20 seconds, pushing the suborbital spacecraft to an altitude of 71,000 ft (18 km) and a top speed over Mach 1.4, both of which were new records for SS2. The Reaction Control System, feather re-entry system, and a thermal protection coating were successfully tested during the flight.

Among other firsts, this was the first SS2 powered flight on which Virgin Galactic's Chief Pilot Dave Mackay was in command. Mackay's co-pilot was Scaled Composites' Test Pilot Mark Stucky, who had been the pilot on the first two supersonic test flights.

SS2 was lifted by the double-fuselage White Knight Two carrier airplane to a height of 46,000 feet (11.7 km). At that point, SS2 was dropped, and its hybrid rocket engine, capable of delivering a thrust of 60,000 lb (267 kN) for a period of 70 seconds, was fired for 20 seconds, for a top speed in excess of Mach 1.4 and a peak altitude of 71,000 ft (18 km).

The primary SS2 systems tested during this flight were the Reaction Control System (RCS) and a new thermal protection coating for the feathering fins. When an airplane is flying in the atmosphere, it controls its attitude using ailerons, elevators, and the rudder. Additional stability is provided by the wings and tail, which tend to keep the airplane flying in a constant direction.

When flying a vehicle into space, an altitude is reached after which the various airfoils have no effect on the direction or orientation of the vehicle. The RCS takes over this function. Attitude control is established using a system of thrusters (essentially small rocket engines) directed by an inertial stability control system. The RCS system test provided additional data for use in optimizing the system.

A new thermal protection coating is now in use on the inner surfaces of the vehicle’s tail booms. These structures surround the rocket engine nozzle and its exhaust stream during powered flight. Later, they are folded forward as the SS2 takes on its feathered reentry configuration. In past flights, the vehicle skin temperatures were higher than called for in the system design, so the new reflective thermal protection coating was applied.

Always quick with a quote, Sir Richard Branson said: “I couldn’t be happier to start the New Year with all the pieces visibly in place for the start of full space flights. 2014 will be the year when we will finally put our beautiful spaceship in her natural environment of space. Today, we had our own Chief Pilot flying another flawless supersonic flight and proving the various systems required to take us safely to space, as well as providing the very best experience while we’re up there.”

Chief Pilot Mackay, who will be flying the first commercial flight on which Sir Richard and his family will be passengers, said that the flight was a “dream come true.”

“I have watched SS2 evolve over the years into an incredible vehicle that is going to open up space to more people than ever before,” he said. “To be behind the controls and fly it as the rocket ignited is something I will never forget. She flew brilliantly.”

That says it all.

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