Engineers and technicians had spent the intervening five months making sure the vehicle will be ready for the higher loads of rocket-powered flight when the time comes, according to the company.
"After release from mothership VMS Eve, the spaceship was immediately pushed into a sharp descent, accelerating to Mach 0.9, which is around the maximum airspeed we can achieve without igniting the rocket motor!" they added.
(Mach 1 is the speed of sound — 767 mph, or 1,234 km/h, at room temperature.) As that note indicates, SpaceShipTwo is designed to be carried aloft by a specialized airplane.
During operational flights, the spacecraft will be dropped at an altitude of about 50,000 feet (15,000 meters), then boost itself to suborbital space using its own rocket motor.
The company is laying the groundwork for powered tests: During today's flight, Unity carried water ballast to simulate the rocket motor's weight, and it was outfitted with a thermal protection system, which will shield the spacecraft from the heat and friction of atmospheric re-entry, Virgin Galactic representatives said.