A tiny solar-sailing spacecraft will hitch a ride on the rocket that blasts the United States Air Force's X-37B space plane into orbit on its latest mystery mission tomorrow (May 20).

The robotic X-37B spacecraft is scheduled to launch tomorrow at 10:45 a.m. EDT (1445 GMT) atop a United Launch Alliance Atlas V rocket from Florida's Cape Canaveral Air Force Station. The booster will also loft 10 tiny "cubesats," including a spacecraft called LightSail, which is about the size of a loaf of bread.

LightSail is part of the nonprofit Planetary Society's effort to develop and advance solar sail technology. Solar sails harness solar radiation pressure, which imparts a tiny but continuous push that can accelerate a spacecraft to tremendous speeds over time,. [Photos: Solar Sail Evolution for Space Travel]

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