The US military’s X-37B space plane took off Thursday on another secret mission that is expected to last at least a couple of years. As with previous missions, the reusable plane—similar to a mini space shuttle—carries secret experiments. It has no crew. The aerospace craft took off at night aboard SpaceX’s Falcon Heavy rocket from NASA’s Kennedy Space Center, more than two weeks late due to technical issues. This is the seventh flight of an X-37B, which has accumulated more than 10 years in orbit since its debut in 2010.
The most recent flight — the longest to date — spanned two and a half years before ending on a landing strip at the Kennedy Center a year ago. Space Force officials would not say how long the orbital test vehicle’s current journey will last or what it has on board, beyond a NASA experiment to measure the effects of radiation on materials.
Built by Boeing, the X-37B resembles NASA’s shuttles, which have since ceased service. But at 9 meters (29 feet) long, the orbital test vehicle is only a quarter the size of the shuttles. No astronauts required; The X-37B has an autonomous landing system. It takes off vertically like rockets, but lands horizontally like airplanes, and is designed to orbit the planet at an altitude ranging from 240 to 800 kilometers (150 to 500 miles). There are two X-37Bs in an old shuttle hangar at the Kennedy Center.