Air Force Mystery Space Plane X-37B Set For Fourth Mission

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The U.S. Air Force’s secretive X-37B space plane is all set to head to orbit on Wednesday for the fourth time. The spacecraft is scheduled for launch at 10:45 AM ET Wednesday atop a United Launch Alliance Atlas V rocket from Cape Canaveral. It will be the unmanned, reusable space plane’s fourth mission, known as Orbital Test Vehicle-4 (OTV-4).

X-37B tests new technologies

The X-37B space plane and its activities are still a mystery. The secrecy around the project has fueled speculations that the Air Force might be testing some space weapon. However, the USAF has repeatedly rejected these rumors, reports Mike Wall of It is unclear what the X-37B will be doing once it enters the orbit. Air Force officials have said in the past that the space plane simply tests new space technologies.

The OTV-4 will be carrying an experiment apparatus belonging to NASA. The space agency’s apparatus, called Materials Exposure and Technology Innovation in Space (METIS), will study the impact of the space environment on about 100 different types of materials. It will provide valuable data about how these materials hold up in the environment they will have to operate, said METIS principal investigator Miria Finckenor.

X-37B to carry a Hall thruster

The X-37B will also be carrying a Hall thruster, which is an advanced version of the thruster that powered the first three Advanced Extremely High-Frequency military communications satellites. The X-37B looks pretty similar to NASA’s space shuttle, which has now retired. The solar-powered plane measures 29 feet in length and 9.5 feet in height. It launches vertically and lands horizontally.

The Atlas V rocket will also be carrying a LightSail “cubesat” made by the Planetary Society. LightSail will test solar sailing technologies. The Air Force has two X-37B space planes, both built by Boeing. The two vehicles have completed a total of three missions to date. The last one touched down in October 2014 at Vandenberg Air Force Base in California after spending 674 days in space.

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