The second SpaceShipTwo, VSS Unity, glides to a landing at the Mojave Air and Space Port Jan. 11 after its first flight in more than five months. Credit: Virgin Galactic

WASHINGTON — Virgin Galactic conducted its first test flight of its SpaceShipTwo suborbital vehicle in more than five months Jan. 11 as the company prepares to begin powered test flights of the vehicle.

The glide flight, conducted in the skies above the Mojave Air and Space Port in California, was the seventh for the second SpaceShipTwo, named VSS Unity, dating back to December 2016. Pilots Mark Stucky and Michael Masucci landed the vehicle at the airport after a successful flight.

The glide flight was the first for SpaceShipTwo since one in early August. The company said in a statement that it had spent the intervening months on “extensive analysis, testing and small modifications to ensure vehicle readiness for the higher loads and forces of powered test flight.”

Virgin Galactic tested those modifications on the glide flight, as the pilots pushed the vehicle into a steep descent shortly after release from its WhiteKnightTwo carrier aircraft, reaching a top speed of Mach 0.9. That is the fastest the vehicle can fly without igniting its hybrid rocket motor, according to the company.

This flight may be the last glide test before the vehicle begins powered test flights. “I think we’ll probably do one more glide flight, and then we’ll be ready to go into powered flight,” George Whitesides, chief executive of Virgin Galactic, said in a presentation at the Next-Generation Suborbital Researchers Conference in Broomfield, Colorado, Dec. 18.

In that presentation, Whitesides didn’t go into details about the schedule for that powered test flight program, but suggested it would take up most, if not all, of the year ahead. “We’re looking forward to having a full 2018 with powered test flights,” he said. “That will be a very exciting phase for our company. We’re going to take our time to do it right.”

The powered flight program, he said, will have many “test points” to go through incrementally as the vehicle first makes it to space on those flights, and then to “refine the various aspects of the customer experience,” such as evaluating the interior of the vehicle.

Virgin Galactic’s first SpaceShipTwo, VSS Enterprise, was lost in an accident in a powered test flight in October 2014, the fourth for that vehicle. An investigation by the National Transportation Safety Board concluded the vehicle’s co-pilot prematurely unlocked the feathering system for the vehicle that raises its tail for reentry, causing the vehicle to become aerodynamically unstable and break up as it passed through Mach 1. The investigation also blamed vehicle designers for not including safety systems that would have prevented the feathering system from being unlocked during that phase of flight.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...