The Rogallo wing is a flexible type of wing. In 1948, Francis Rogallo, a NASA engineer, and his wife Gertrude Rogallo, invented a self-inflating flexible wing they called the Parawing, also known after them as the "Rogallo Wing" and flexible wing. NASA considered Rogallo's flexible wing as an alternative recovery system for the Mercury and Gemini space capsules, and for possible use in other spacecraft landings, but the idea was dropped from Gemini in 1964 in favor of conventional parachutes. History Rogallo had been interested in the flexible wing since 1945. He and his wife built and flew kites as a hobby. They could not find official backing for the wing, including at Rogallo's employer National Advisory Committee for Aeronautics (NACA), so they carried out experiments in their own time. By the end of 1948 they had two working designs using a flexible wing — a kite they called "Flexi-Kite" and a gliding parachute they later referred to as a "paraglider". Rogallo and his wife received a patent on a flexible square wing in March 1951. Selling the Flexi-kite as a toy helped to finance their work and publicize the design. NASA research In the late 1950s and early 1960s, U.S. aerospace manufacturers worked on parachute designs for space capsule recovery. NASA briefly considered the Rogallo wing to replace the traditional round parachute for the Project Mercury capsule during temporary development problems. Later, the Rogallo wing was the initial choice for the Project Gemini capsule, but development problems ultimately forced its replacement with the parachute. Construction Nowadays the term "Rogallo wing" is synonymous with one composed of two partial conic surfaces with both cones pointing forward. Slow Rogallo wings have wide, shallow cones. Fast subsonic and supersonic Rogallo wings have long, narrow cones. The Rogallo wing is a simple and inexpensive flying wing with remarkable properties. The wing itself is not a kite, nor can it be characterized as glider or powered aircraft, until the wing is tethered or arranged in a configuration that glides or is powered. In other words, how it is attached and manipulated determines what type of aircraft it becomes. The Rogallo wing is most often seen in toy kites, but has been used to construct spacecraft parachutes, sport parachutes, ultralight powered aircraft like the trike and hang gliders. Rogallo had more than one patent concerning his finding; the due-diligence expansion of his invention involved cylindrical