Secretive US space plane X-37B lands after record 908 days in orbitThe X-37B has returned to Earth after more than two years in orbit, breaking its previous record – what has it been doing in orbit for so long?The X-37 Orbital Test Vehicle (OTV) began life under the umbrella of NASA, but was passed to the US military, which created the X-37B variant.Officials say that it carried out a range of scientific experiments, including a test designed by the US Naval Research Laboratory, in which energy was collected by solar panels and beamed back to Earth as microwaves.Other experiments were provided by NASA, including some designed to test the effects of space exposure on various materials and seeds.Sign up to our free Launchpad newsletter for a voyage across the galaxy and beyond, every FridayMore on these topics:"