Virgin Galactic's SpaceShipTwo left terra firma for her 24th glide flight on Wednesday morning. The flight was the first in which the loading and venting of the ship's nitrous system was tested. Virgin Galactic described the flight as "another key milestone on the way to our first powered flight."

When SpaceShipTwo does eventually fly under its own steam, liquid nitrous oxide will be used to oxidize the solid rubber-compound fuel that will provide power. This flight successfully tested the systems with which the nitrous oxide is loaded and vented. Interestingly, the venting took place while SpaceShipTwo was still on the pylon that connects it to the WhiteKnightTwo carrier.

Chief Pilot David Mackay manned the controls of the WhiteKnightTwo carrier craft, launching from the Mojave Air & Space Port. Former NASA and military test pilot Mark "Forger" Stucky, now of Scaled Composites, piloted SpaceShipTwo itself.

This was also the sixth in-flight test of SpaceShipTwo's feathered re-entry system, which raises the craft's tail section to angle of 65 degrees to the fuselage, slowing the craft in the upper atmosphere for more efficient reentry.

Virgin Galactic says that all test objectives were met with success.

View gallery - 4 images