Space Florida, a state-backed economic development agency, doubled its budget to refurbish two old space shuttle hangers in an effort to lure a secretive military project to the Kennedy Space Center.

Space Florida board members  agreed to add $4 million to the project, with is aimed at relocating the Air Force’s X-37B Orbital Test Vehicles to Florida from California.

The 29-foot-long robotic spaceships, which resemble miniature space shuttles, are experimental vehicles the military has been flying since April 2010. The program’s third mission, launched on Dec. 11, 2012, remains under way.

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The Air Force has not disclosed what the X-37B is doing in orbit, nor when or where it will land. Two prior X-37B missions lasted 224 days and 469 days respectively, and landed autonomously at Vandenberg Air Force Base in California. The program currently consists of two vehicles.

The military has said it is considering relocating the program to Florida to save money on operations. The vehicles are launched on unmanned Atlas 5 rockets from Cape Canaveral Air Force Station, located just south of NASA’s Kennedy Space Center. They could land on the shuttle’s no-longer-needed runway.

Space Florida last year agreed to spend $5 million to prepare two mothballed space shuttle processing hangars at the Kennedy Space Center for its prospective new tenant. Boeing contributed another $2.5 million for the project.

Space Florida will now add add $4 million more for the project, which is code-named “Coyote,” to outfit the hangars for spacecraft assembly, refurbishment and testing. Boeing  will add another  $2 million.

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Under a similar partnership arrangement with Space Florida, another Boeing project already is using a third space shuttle processing hangar. The company is developing a seven-person commercial space capsule called the CST-100, one of three potential space taxis NASA is considering using to fly its crew to and from the International Space Station.

Photo: Personnel in protective suits conduct checks on the X-37B Orbital Test Vehicle 1 (OTV-1), the U.S. Air Force’s first unmanned re-entry spacecraft. Credit: U.S. Air Force photo/ Michael Stonecypher