Unity’s high-speed glide

The Virgin Galactic VSS Unity during a glide test assessed its performance, stability and control at high transonic speeds. The previously white feather flaps are now covered in a silver film to provide thermal protection. Virgin Galactic

Virgin Galactic is a step closer to starting commercial spaceflight operations after its VSS Unity completed an initial high-speed glide test. The aircraft was taken from the company’s Mojave, California, base to high altitude from its VSS Eve mothership before it was released, put into a steep descent and accelerated to Mach 0.9 to examine its performance, stability and control at high transonic speeds.

This is around the maximum speed the aircraft can achieve without its rocket motor, A Virgin Galactic statement said: “At this stage of the glide flight programme, each flight is essentially a dry run for rocket-powered test flights. Where possible, the team replicates those powered flight conditions by, for example, adding water ballast to simulate the weight and positioning of the rocket motor. As during previous flights, the water ballast was jettisoned at around 22,000ft, allowing the pilots to complete the flight and land in a lighter configuration, again simulating the conditions which will apply during space flight. As a precursor to powered flight VSS Unity flew with her thermal protection system fully applied. This ensures heat loads generated by air friction during rocket-powered boost and supersonic re-entry cause no damage to the vehicle… the upper surfaces of the previously white feather flaps [are] now covered in a protective silvered film.”

The test came after several months of Virgin Galactic undertaking planned ground time on VSS Unity involving analysis, tests and modifications. The company aims to start commercial spaceflight operations later this year. Mark Broadbent