Virgin Galactic's tourist-carrying spaceplane has taken a step closer to entering service after its chemical rocket engine was fired for the first time in the skies over the Sierra Nevada Mountains in California. With test pilots Mark "Forger" Stucky and Dave Mackay at the controls, the 60-ft-long (18 m) SpaceShipTwo VSS Unity pegged the speedometer at Mach 1.87 (1,424 mph, 2,290 km/h) within 30 seconds of igniting its engine.

Built by Virgin Galactic subsidiary, The Spaceship Company, VSS Unity's first rocket-powered, supersonic flight began today at 8:02 am PDT as the spaceplane was carried aloft from the company's Mojave base by the mothership WhiteKnightTwo, also known as VMS Eve, piloted by Mike Masucci and Nicola Pecile. Unity was dropped from Eve at an altitude of 46,500 ft (14,173 m).

A few seconds later the spacecraft's hybrid rocket engine fired, sending the vehicle on an 80-degree angle upward. The engine, which uses a plug of plastic solid rocket fuel and nitrous oxide as an oxidizer, propelled Unity to an altitude of 84,271 ft (25,686 m) as it went transsonic and then supersonic. As the engine throttled back and shut down, the twin tail booms deployed 60 degrees into a "feathered" configuration that slowed the craft down as it descended to Earth. At 50,000 ft (15,240 m), the booms were retracted and Unity glided to a conventional landing.

According to Virgin Galactic, the tail boom now incorporates new safety devices developed in the wake of the loss of VSS Enterprise after its booms deployed prematurely during a test flight in 2014. Today's flight showed marked improvements in rocket burn duration, speed and altitude achieved, and Unity will now go into its final flight test program. Meanwhile, engineers are studying telemetry and recorder data on flight, motor and vehicle performance.

The video below shows the test firing.

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