Virgin Galactic performed the latest glide flight of its second SpaceShipTwo suborbital spaceplane Aug. 4, calling it a "dry run" for upcoming powered test flights. SpaceShipTwo, carried aloft by its WhiteKnightTwo aircraft, separated from the plane about an hour after its 11:58 a.m. Eastern takeoff from Mojave Air and Space Port in California. The spaceplane landed back in Mojave ten minutes later. The glide flight was the sixth for this SpaceShipTwo vehicle, named VSS Unity, and the first in two months. As on two previous glide flights, pilots tested the feathering system that raises the vehicle's twin tail booms for...