A mini military space plane lifted off Wednesday from Cape Canaveral, but, as usual, the Air Force isn't saying much about the experimental unmanned flight's mission.
The launch marks the fourth flight for the military research program, which is shrouded in secrecy. The three previous missions also began with rocket launches from Florida.
The last X-37B mission lasted close to 675 days and ended with a California touchdown.
The Air Force won't say how long this mission will last or where it will end.
The X-37B looks like a miniature version of a NASA space shuttle. Like the old shuttle, the X-37B launches vertically and lands horizontally, is reusable, and has lots of room for experiments. But, no one flies on them, and they are operated robotically.
NASA has a materials experiment aboard - close to 100 polymers and composites to investigate how they hold up in space long term.
The Atlas 5 will also deploy a cube-sat no bigger than a loaf of bread, known as the "Light Sail," developed by the Planetary Society.
Bill Nye, "The Science Guy," is CEO of the Planetary Society and helped raise funds and support to privately build the Light Sail.
"The idea is, it's astonishing, light has no mass, but it has momentum," said Nye. "It's pure energy. When light hits me, it's giving us the tiniest push."
Nye said light can push the large solar sail, and the spacecraft, slowly but indefinitely. He said that technology offers great potential for a manned spacecraft to one day orbit Mars, but also for an orbiting satellite that can monitor solar storms that wreak havoc on electronics on earth and in space.
"And we have to protect our communications satellites when those things happen," said Nye. "Well you could get a jump on it if you had a solar sail satellite in orbit."
Nye said the solar sail will deploy in about 2 weeks. This mission will only test the deployment mechanisms in space. Next year, another Light Sail will be launched into space and fully tested.
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