A spaceplane is an aerospace vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space. It combines features of an aircraft and a spacecraft, which can be thought of as an aircraft that can endure and maneuver in the vacuum of space or likewise a spacecraft that can fly like an airplane. Typically, it takes the form of a spacecraft equipped with wings, although lifting bodies have been designed and tested as well. The propulsion to reach space may be purely rocket based or may use the assistance of airbreathing jet engines. The spaceflight is then followed by an unpowered glide return to landing.
Five spaceplanes have successfully flown to date, having reentered Earth's atmosphere, returned to Earth, and safely landed — the North American X-15, Space Shuttle, Buran, SpaceShipOne, and Boeing X-37. All five are considered rocket gliders. As of 2015[update], only these aircraft and rockets have succeeded in reaching space. Two of these five (X-15 and SpaceShipOne) are rocket-powered aircraft, having been carried up to an altitude of several tens of thousands of feet by an atmospheric mother ship before being released, and then flying beyond the boundaries of the earth's atmosphere under their own power. Three (Space Shuttle, Buran, and X-37) are vertical takeoff horizontal landing (VTHL) vehicles relying upon rocket lift for the ascent phase in reaching space and atmospheric lift for reentry, descent and landing. The three VTHL spaceplanes flew much further than the aircraft launched ones, not merely leaving the earth's atmosphere but also entering orbit around it, which requires at least 50 times more energy on the way up and heavy heat shielding for the trip back. Of the five vehicles, three have been piloted by astronauts, with the Buran and X-37 flying unmanned missions.