US military spacecraft takes off on yet another covert mission that should last for years

The X-37B spacecraft of the US military took off on a covert mission on Thursday that should last at least a few years.Similar to earlier missions, classified experiments were carried by the reusable aircraft that resembled a miniature space shuttle. Nobody is present on board.After more than two weeks of delays due to technical difficulties, the spacecraft launched at night on SpaceX's Falcon Heavy rocket from NASA's Kennedy Space Center.After making its debut in 2010, the X-37B has spent over ten years in orbit. This was its seventh flight.The last flight, the longest one yet, lasted 2 1/2 years before ending on a runway at Kennedy a year ago.Space Force officials would not say how long this orbital test vehicle would remain aloft or what’s on board other than a NASA experiment to gauge the effects of radiation on materials.Built by Boeing, the X-37B resembles NASA’s retired space shuttles. But they’re just one-fourth the size at 29 feet (9 meters) long. No astronauts are needed; the X-37B has an autonomous landing system.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.(with inputs from The Associated Press)