Virgin Galactic SpaceshipTwo passes speed of sound in flight test


Virgin Galactic’s VSS Unity fires its rocket engine during its successful test flight

Virgin Galactic’s SpaceShipTwo VSS Unity has successfully completed its first supersonic, rocket-powered flight, almost four years after the tragic loss of its predecessor VSS Enterprise during a test flight.

VSS Unity’s test flight from Mojave Air and Space Port in California, took off at 8:02am on April 5 with Mark “Forger” Stucky and Dave Mackay in the cockpit, attached to the WhiteKnightTwo carrier aircraft, VMS Eve, piloted by Mike Masucci and Nicola Pecile.

VSS Unity gliding during a test flight 

The mated vehicles climbed to a launch altitude of around 46,500ft before VMS Eve executed a clean release of Unity. After a few seconds, Unity’s rocket motor was fired and the pilots aimed the spaceship upwards into an 80˚ climb, accelerating to Mach 1.87 during 30 seconds of rocket burn.

The hybrid rocket motor on VSS Unity runs on a nitrous oxide / Hydroxyl-terminated polybutadiene (HTPB) compound and was designed, built and tested by The Spaceship Company, the company owned by Richard Branson’s Virgin Galactic and Scaled Composites.

After the rocket shutdown, VSS Unity continued an upwards coast to an apogee of 84,271ft before readying for the downhill return. At this stage, the pilots rotated up the vehicle’s tail booms to into the feathered configuration which increases drag and stability while descending.

This feathering design feature is key to a reliable and repeatable re-entry. Additional safety mechanisms have been incorporated into the spacecraft after the 2014 VSS Enterprise test flight accident, which occurred when the tail booms were repositioned too early.

At around 50,000ft, the tail-booms were lowered again and while jettisoning the remaining oxidizer, Unity turned towards Mojave for the glide home and landing.

The successful test flight follows two years of extensive ground and atmospheric testing and generated data on flight, motor and vehicle performance which engineers will review.

It also marks a key moment for the test flight program and marks the start of the final portion of Unity’s flight test program.

April 6, 2018

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About Author


Ben has worked as a journalist and editor, covering technology, engineering and industry for the last 20 years. Initially writing about subjects from nuclear submarines to autonomous cars to future design and manufacturing technologies, he was editor of a leading UK-based engineering magazine before becoming editor of Aerospace Testing in 2017.

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