Research aircraft

Even after the development of powered aircraft, gliders have been built for research. The NASA Paresev Rogallo flexible wing is an example that was built to investigate alternative methods of recovering spacecraft. Although this application was abandoned, publicity inspired hobbyists to adapt the flexible wing airfoil for modern hang gliders.

Unpowered flying wings are another type of aircraft that have been built for aerodynamic research. Examples are the Horten flying wings, the scaled glider version of the Armstrong Whitworth A.W.52 jet powered flying wing and the Baynes Bat (to give information for a planned military glider).

In contrast to the flying wings, lifting bodies have been also developed using unpowered prototypes. Although the idea can be dated to Vincent Justus Burnelli in 1921, interest increased as an alternative for returning spacecraft. Traditional space capsules have very little control over where they land, whereas a steerable craft using wings would have more options. The lifting bodies use the fuselage itself to generate lift without employing the usual thin and flat wing. The objective of the lifting body is to minimize the drag and structure of a wing for very high supersonic or hypersonic flight as might be experienced during the re-entry of a spacecraft. This can be compared with a flying wing that seeks to minimise drag at subsonic speeds by eliminating non-lifting surfaces. Examples of type are the Northrop HL-10 and Martin-Marietta X-24.

Rocket gliders

Rocket-powered aircraft consume their fuel quickly, and so most must land unpowered, unless there is another type of engine. The first was the Lippisch Ente. Later examples include the Messerschmitt Me 163 rocket-powered interceptor.^[13] The American series of research aircraft starting with the Bell X-1 in 1946 up to the North American X-15 spent more time flying unpowered than under power. In the 1960s research was also done on unpowered lifting bodies and on the X-20 Dyna-Soar project, but although the X20 was cancelled, this research eventually led to the Space Shuttle.

On April 12, 1981, the Space Shuttle orbiter first flew. The Shuttle re-entered at Mach 25 at the end of each spaceflight, and landed entirely as a glider. As with Buran the shuttles represented by far the fastest type of aircraft of all time. The latest examples of rocket glider are the privately funded SpaceshipOne which is intended for sub-orbital flight and the XCOR EZ-Rocket which is being used to test engines.

Rotary wing

Most unpowered rotary-wing aircraft are kites rather than gliders, i.e. they are usually towed behind a car or boat rather than being capable of free flight. These are known as rotor kites. However rotary-winged gliders, 'gyrogliders', were investigated that could descend like an autogyro or helicopter, using the lift from rotors to reduce the vertical speed. These were evaluated as a method of dropping people or equipment from other aircraft.