<p><b> by Jeff Donlan</b></p>A military space plane just returned from another mysterious mission. The U.S. Air Force’s X-37B</a> landed with a sonic boom this weekend, after a classified space mission lasting nearly two years. Most of the X-37B’s activities are kept secret, but the Air Force says they are just testing technologies in orbit. This mission reportedly involved testing a new thruster system and NASA material samples. This was X-37B’s fourth mission. It first flew in 2010.<p> </p></p><br /> <p>The post Mystery Military Space Plane Lands After Two-Year Mission</a> appeared first on Vocativ</a>.</p>
