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The Air Force's experimental X-37B space plane announced the end of its nearly two-year mission by creating a sonic boom on Sunday that surprised residents along Florida's Space Coast. Officials have provided only vague details about the unmanned craft's more than 700-day mission.

By Bill Chappell www.npr.org 5-8-17

"Not much is known about the 30-foot-long robotic spacecraft or what it took to space," as member station WMFE reports.

The X-37B is an "orbital test vehicle" that looks like a miniature space shuttle — it even used the old shuttle runway at NASA's Kennedy Space Center when it landed Sunday. To reach orbit, it rides on an Atlas V rocket.
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"The program supports technology risk reduction, experimentation and operational concept development," a spokesperson said at the time.

"What's interesting to me is it's being done in such an opaque manner," space policy analyst Joan Johnson-Freese from the US Naval War College told CBS News in 2015.

"If the Chinese were doing this, oh my god, there would be congressional hearings on a daily basis and programs being ginned up to respond to it. It has capabilities that other countries aren't sure about, and so they're going to be very nervous about them. If it's a highly maneuverable space vehicle that has some pretty significant implications." says Johnson-Freese.