An Atlas V rocket sent a classified military space plane into another long orbit Wednesday from the Space Coast.

The Air Force isn't saying much about the unmanned mission, but the mini space shuttle blasted off at 11:05 a.m. from Cape Canaveral Air Force Station.

This is the fourth flight of an X-37B, a secretive, experimental program run by the Air Force. The three previous missions also began with rocket launches from Cape Canaveral Air Force Station.

The U.S. Air Force moved operations and processing of the space plane from California to the Kennedy Space Center. Earlier this month, the unmanned vehicle was moved to the Cape Canaveral Air Force Station and mounted on top of an Atlas V rocket.

The mystery test vehicle — essentially a technology test bed — is designed to orbit the Earth and then land like one of NASA's old space shuttles. It is operated robotically, without anyone on board, and is reusable. It is 29 feet long — about one-fourth the size of a NASA shuttle.


View Mission Overview from the United Launch Alliance

The longest X-37B flight lasted about 675 days; touchdown was last October. There was no official word on how long this one will stay up. All three previous missions ended in California.

Meantime a not-so-secret experiment involving a 344-square-foot solar sail is taking its first trip to space.

The experiment is headed up by the group The Planetary Society, and its leader Bill Nye the Science Guy, who witnessed today's launch.

The shoebox sized Cubesat will deploy its sail systems in what's hoped to be a future way to propel spacecraft without using fuel, which is costly and heavy.

"The force of sunlight gives it a push. It's not the particles of the solar wind, it's light itself, pushing through space. So we strongly believe this will advance space exploration," Nye saidat the launch viewing site.

There was also a NASA experiment on the launch that will study how more than 100 different types of materials fare in the rigors of space.

That data might help designing future spacecraft.

Although largely mum about this X-37B flight, the Air Force has acknowledged a thruster experiment involving electric propulsion. Air Force researchers want to check design modifications to ion thrusters already flying on some advanced military communication satellites.

Information from The Associated Press was used in this report.