Virgin Galactic's passenger-carrying spaceship VSS Unity has completed its seventh unpowered glider test flight. Test pilots Mark "Forger" Stucky and Michael "Sooch" Masucci ran the craft through a series of maneuvers over Mojave, California during which it reached a transonic velocity of Mach 0.9 (690 mph) – almost the highest it can attain without an engine.

The January 11 flight was the latest in a series of dry run flights for the Unity, which is the replacement prototype for the VSS Enterprise – the craft lost in a midair accident in 2014. Unity was carried aloft by the mothership VMS Eve before being dropped at high altitude to return to Earth on a glide path.

The purpose of the flight was to subject Unity to higher acceleration loads and forces, simulating the conditions of powered flight and pushing the craft's performance envelope. It was also a test for various modifications to the design that have been put through months of ground testing in the lead up to Thursday's flight.

According to Virgin Galactic, the Unity flew with water ballast equivalent in weight to the fully fueled hybrid liquid/solid rocket motor that will one day propel the vehicle into space on a suborbital trajectory. As on previous flights, the ballast was jettisoned at 22,000 ft to simulate the weight of a returning spacecraft. This allows the test program to not only simulate the conditions of ascent, but also of landing.

In addition, this marks the first time that VSS Unity flew with its Thermal Protection System (TPS) installed. Designed to protect the vehicle against air friction during supersonic flight, the TPS gave the upper surface a new silvery sheen.

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