Elbert Leander "Burt" Rutan is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft, and considered the "second true innovator" in the field of aerospace materials technology, his most important predecessor being German engineer Hugo Junkers, who pioneered the design of all-metal aircraft in 1915. He is most famous for his design of the record-breaking Voyager, which was the first plane to fly around the world without stopping or refueling, and the sub-orbital spaceplane SpaceShipOne, which won the Ansari X-Prize in 2004 for becoming the first privately funded spacecraft to enter the realm of space twice within a two week period.