The U.S. military\u2019s X-37B space plane blasted off Thursday on another secretive mission that\u2019s expected to last at least a couple of years.<\/p>\n\n\n\n
Like previous missions, the reusable plane resembling a mini space shuttle carried classified experiments. There\u2019s no one on board.<\/p>\n\n\n\n
The space plane took off aboard SpaceX\u2019s Falcon Heavy rocket from NASA\u2019s Kennedy Space Center at night, more than two weeks late because of technical issues.<\/p>\n\n\n\n
It marked the seventh flight of an X-37B, which has logged more than 10 years in orbit since its debut in 2010.<\/p>\n\n\n\n
The last flight, the longest one yet, lasted 2 1\/2 years before ending on a runway at Kennedy a year ago.<\/p>\n\n\n\n
Space Force officials would not say how long this orbital test vehicle would remain aloft or what\u2019s on board other than a NASA experiment to gauge the effects of radiation on materials.<\/p>\n\n\n\n
Built by Boeing, the X-37B resembles NASA\u2019s retired space shuttles. But they\u2019re just one-fourth the size at 29 feet (9 meters) long. No astronauts are needed; the X-37B has an autonomous landing system.<\/p>\n\n\n\n
They take off vertically like rockets but land horizontally like planes, and are designed to orbit between 150 miles and 500 miles (240 kilometers and 800 kilometers) high. There are two X-37Bs based in a former shuttle hangar at Kennedy.<\/p>\n\n\n\n