Military


Rogallo Wing

The paraglider, or "Rogallo Wing", invented by Francis M. Rogallo in the late 1940s, used flexible fabric airfoils arranged in a V-shape. Flexible wings are wings made of very loose or slack cloth whose configuration in flight is maintained by the combination of the aerodynamic forces and the reactions from the load suspension system. Such wings can be completely flexible_ or they may be stiffened in several ways to meet the requirements of particular applications. The flexible wing could be guided more precisely than a parachute. The flexible wings of most immediate interest were those with no structural stiffening because they have weight, volume, packing, and deployment characteristics potentially as good as those of conventional parachutes, but provide a stable and controllable glide with performance adequate for aerial delivery of cargo and personnel.

After the usual dreaming about flexible wings since childhood, in 1945 at the close of World War II Francis M. Rogallo decided to undertake a serious study of the subject. It was decided to undertake it at hom% jointly with Mrs. Rogallo and later including other members of the family and friends. U.S. Patent No. 2,546,078 filed in November 1948 and issued in March 1951 to Gertrude and Francis Rogallo is entitled "Flexible Kite" even though it proposes applicability of the concept to all heavier than air flying machines. This private endeavor covered the 13 years from 1945 until late in 1958, when America's entry into the exploration of space brought about government consideration of this and other unconventional ideas.

Early flight tests at the Langley Research Center on inflated-tube configurations indicated a possible design approach for the recovery of spacecraft and for aerial delivery of cargo. The need for research information on conical parawings for support of the Gemini parawing and the Army cargo-drop glider prompted extensive wind-tunnel research on inflated-tubetype of wing configurations (see refs. 19, 28, and 24). Other work on wings having small leading edges and a rigid frame led to the construction of flight vehicles such as the Paraglider Research Vehicle and the Ryan Flex-wing.

In the early 1960s the Rogallo wing seemed an excellent means of returning a spacecraft to Earth. The delta wing design was patented by NACA Langley engineer Francis M. Rogallo. In May 1961, Robert R. Gilruth, director NASA's Space Task Group, requested studies of an inflatable Rogallo-type Parawing for spacecraft. Several companies responded; North American Aviation produced the most acceptable concept and development was contracted to that company. In November 1961 NASA Headquarters launched a paraglider development program, with Langely doing wind-tunnel studies and the NASA Flight Research Center supporting the North American test program.

The North American concept was a capsule type vehicle with a stowed parawing that could be deployed and controlled from within for a landing more like an airplane instead of a splash down in the ocean as was the practice in the Mercury and later the Gemini and Apollo programs. The logistics became enormous and the price exorbitant, besides which, NASA pilots and engineers felt some baseline experience like building a vehicle and flying a Parawing should be accomplished first.

The wing was attached to steel tubing to create a flying machine. It ended up looking like an oversized tricycle with a mast. The pilot sat strapped in the seat without any kind of cockpit enclosure. He could fly higher or lower by tilting the wing from side to side with a control stick. This craft, called the Parasev, was one of NASA's first research airplanes. NASA registered the Paresev, the first NASA research airplane to be constructed totally in-house, with the Federal Aviation Administration on February 12, 1962.

Flight testing of the Paresev (Paraglider Rescue Vehicle) started immediately, and proved the wing to be too flexible with it flapping and bulging in alarming ways. The poor membrane design led to trailing edge flutter, with longitudinal and lateral stick forces being severe. A number of different rigging modifications to improve the flying characteristics were tried, but very few were successful and none were predictable. Everything seemed to affect stick forces in the worst way.

The Paresev completed nearly 350 flights during a research program from 1962 until 1964. Pilots flying the Paresev included NASA pilots Milton Thompson, Bruce Peterson, and Neil Armstrong from Dryden, Robert Champine from Langley, and astronaut Gus Grissom, plus North American test pilot E.P. Hetzel. Engineers tested the Rogallo wing for several years in NASA's wind tunnels at Langley Research Center. They decided to stick with the original parachute plan instead of using the paraglider. But, that wasn't the end of the Rogallo wing.

The Paresev was legally transferred to the National Air and Space Museum of the Smithsonian Institute, Washington, DC. Despite its looks, the Paresev was a useful research aircraft that helped develop a new way to fly.

Today, the Rogallo wing is used by the recreational sporting goods industry. Hang gliders soaring from a hillside or cliff are the commercial adaptation of Francis Rogallo's invention to help the space program land its vehicles. It's come a long way. Hang gliders are now used for fun and exploration. Although the Rogallo wing was never used on a spacecraft, it revolutionized the sport of hang gliding, and a different but related kind of wing was tested on the X-38 technology demonstrator. Rogallo first thought of using the flexible wing for recreation. He only presented it to the space industry after deciding that there was nowhere to sell his idea for public use.



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