Rogallo's Flexible Wing
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- Francis and Gertrude Rogallo
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Francis and Gertrude Rogallo (right), inventors of the V-shaped flexible "parawing." In December 1961, Langley flight-tested a 5O-foot parawing's ability to bring down safely a model of a manned space capsule from a few thousand feet above Plum Tree Island (below), an old army bombing range near Langley Field.
These are quotes duplicated from Chapter 11 of a major book:
More than any other division at Langley, the Full-Scale Research Division acted as a "service effort" for Apollo. Testing in the high-speed wind tunnels of this division provided essential data in the transonic regime for the moon shot. Not all Apollo work carried out in the Full-Scale Research Division, however, involved high-speed aerodynamics. Perhaps the most interesting and potentially significant technologies developed in this division involved low-speed aerodynamics -specifically, a proposed Apollo capsule recovery system that used a controllable paraglider. This concept, which was eventually turned down both for Gemini and Apollo, was the brainchild of Francis M. Rogallo, an ingenious thinker and kite-flying enthusiast who worked in the 7 x 10-Foot Tunnel Branch.
Although Bob Gilruth and many other engineers responsible for Project Mercury considered the ballistic capsule approach "an elegant solution" to the problem of quickly putting a person in orbit, no aeronautical engineer was especially happy with the plan.35 Their dream was for the spacecraft [381] to return to earth using "wings and wheels" -that is, to really fly down through the atmosphere to a landing on a conventional runway.
NASA placed its hopes for such an airplane-like landing on an unusual inflated-fabric flexible wing, or parawing. Such a wing was being developed at Langley in the early 1960s under the intellectual direction of Francis M Rogallo. Rogallo's idea for Gemini, as well as for Apollo, was to pack away a carefully designed parawing like a parachute until the spacecraft fell to about 60,000 feet, at which time an elaborate unstowing and unfurling process began. By 20,000 feet, if a I went well, the descending spacecraft would turn into the world's heaviest hang glider, suspended under a dart-shaped parawing. The astronauts themselves would then bring the soaring craft down to a landing either on water or on soil.36
Rogallo had started at NACA Langley in 1936 after graduation from Stanford University, and since 1945 the flexible wing had been a pet project. A survey of the history of the parawing provides not only an understanding of the genesis of one of Langley's most intriguing -if never used - developments for Apollo but also insight into the sudden and dramatic impact of Sputnik and the spaceflight revolution on the course of independent research at Langley.
Rogallo and his wife, Gertrude, spent their spare time flying home-built kites at their beach house at Nags Head, North Carolina, which is near Kitty Hawk. By the end of World War II, this hobby had begun to give the couple ideas for unconventional vehicles, such as hydrofoil boats, ground-effect machines, V/STOL aircraft, and flexible wings. Because they could not find any organization, including their own NACA, to support R&D for their ideas, they "decided to do what we could privately as time permitted." Initially their efforts focused on configurations resembling boat sails; later, their designs were similar to parachutes. Finally, they concentrated on shapes somewhere between boat sails and parachutes -flexible wings. By the end of 1948, the couple had developed a flexible kite, which the Rogallos called "Flexi-Kite," and a type of gliding parachute, which they later named a "paraglider." 37
In 1948, Rogallo and his wife filed a patent for a V-shaped flexible wing, which was awarded (U.S. Patent No. 2,546,078) in March 1951. From the outset, the inventors had thought of their parawing as a wing not only for sport gliders but also for military and civil powered aircraft. No one, however, took their proposals seriously. As Rogallo remembers, when meeting friends and acquaintances, they were generally greeted with, "How's the kite business?" The Rogallos had resorted to selling their Flexi-Kite as a toy in order to illustrate the parawing principle and help finance their work Francis Rogallo would often say in later years that toys should copy the real thing and not the other way around.38
For the first seven years of its development, the motivation behind the flexible wing had been "purely aeronautical," but that changed in 1952 when the Rogallos saw the Colliers magazine that ran the exciting series...
Formal correct spelling: Paresev. But the other with "a" was found in many texts/
- An early version of the single-seat Paraglider Research Vehicle ("Parasev") is test "flown" in Langley's Full-Scale Tunnel in January 1962. L-62-631.
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An early version of the single-seat Paraglider Research Vehicle ("Parasev")[sic,
Paresev for Pa..., res...v ] is test "flown" in Langley's Full-Scale Tunnel in January 1962. L-62-631.
....of stories about spaceflight. Francis Rogallo was struck by the issue's beautiful illustrations of rigid-winged gliders mounted on top of huge rockets. As he recalled later in a 1963 speech to the American Astronautical Society, "I thought that the rigid-winged gliders might better be replaced by vehicles with flexible wings that could be folded into small packages during the launching." In August 1952 he met Dr. Willy Ley, one of Colliers consultants, and told Ley his thoughts about flexible wings for astronautics in the conversation Rogallo mentioned that the technology of flexible wings might someday prove very useful when spacecraft commute regularly between planets: a rocket ship returning from Mars could pop out flexible wings as it entered the earth's atmosphere and glide the last 100 or 200 miles home, saving "the stockholders" that much fuel. "But the time was not yet ripe."39 (Note that Rogallo imagined, perhaps in jest, that private corporations would be sponsoring the interplanetary travel, not governments.)
In April 1954, hoping to gain acceptance of his concept for aerospace applications, Rogallo gave a presentation, complete with glider model demonstrations, to the local Tidewater reserve unit of the Air Force Research and Development Command. Two months later, he submitted a proposal to include parawing research in the NACA budget, but the proposal was rejected. Indefatigable, he submitted a proposal to discuss his flexible wing concepts at the annual meeting of the Institute of Aeronautical Sciences (IAS). This was "the first [proposal] that actually reached the program committee after several tries," but it too was turned down. The IAS rejection letter read: "Although the paper is out of the ordinary and looks like it might be fine to hear, it just does not fit into our program."40
As it did for so many research projects, the launch of Russia's Sputnik 1 in October 1957 changed the course of history for the parawing. Even before the formation of NASA in 1958, Rogallo had received NACA approval to make a few crude wind-tunnel and model flight investigations of parawings in the 7 x 10-Foot Tunnel Branch. In December 1958, he made a presentation to the Langley Committee on Aerodynamics, and as he remembers, "gradually people in other divisions became interested and volunteered to investigate parawings in their facilities." During 1959 cloth parawings were tested in the 4-Foot Supersonic Pressure Tunnel at Mach 2, and still other parawing models were deployed at high altitudes (150,000 to 200,000 feet) at nearly Mach 3 from rocket launchings at Wallops Island. In August 1959, von Braun invited Rogallo to Huntsville for a presentation, so "business was picking Up "41
For the next year and a half, into early 1961, Rogallo gave talk after talk on his parawing concept to various technical groups. He spoke at the national aeronautics meeting of the Society of Automotive Engineers (April 1960); at Ryan Aeronautical Company and North American Aviation (May 1960); at the annual IAS meeting in New York City (Jan. 1961); and at local IAS chapter meetings in Lancaster, California, and San Diego [384] (March 1961). By the end of 1960, the Ryan company, the same company that built Charles Lindbergh's Spirit of St. Louis, began building a powered man-carrying "Ryan Flex-Wing" at its own expense; Rogallo was on hand in San Diego to witness its first flight. Also, in early 1961, NASA Marshall gave Ryan and North American contracts to study the feasibility of recovering Saturn boosters by means of parawings. NASA in-house studies of the technological capabilities of the wing were made at Marshall and Langley and demonstrated that recovery of the (later canceled) C-2 rocket stage was feasible. By the end of 1961, the DOD let its first parawing contract, to Ryan, for flight tests of the Flex-Wing. The aircraft was later sent to NASA Langley for investigation in the Full-Scale Tunnel. Thereafter, the number of projects and contracts related to parawings increased too rapidly to mention in this brief history.42
"It looked like parawings were here to stay," Rogallo rejoiced at the time, and Sputnik was the reason.43 By the summer of 1963, it appeared that the concept had achieved worldwide acceptance and that the time had come for his parawing study group to give the U.S. government royalty-free license to use its patents, which it did in a ceremony in Washington on 18 July 1963. In a short speech, Rogallo expressed his hopes for the invention: "We feel confident that the civil and military agencies of the government will carry on this work, and we hope private industry will promote use of the concept for business and pleasure as effectively as they have for astronautics and military aeronautics." In a separate ceremony a day earlier, Dr. Hugh Dryden, deputy administrator of NASA, presented Francis Rogallo and his wife with a check for $35,000 for their development of the flexible wing concept; at that time, it was the largest cash award ever made by the space agency to an inventor.44
Unfortunately, the spaceflight revolution, which had so quickly turned circumstances in the wing's favor, just as quickly turned circumstances against it. That is often the nature of revolutions -to take things full circle. From the beginning, NASA's interest in Rogallo's paraglider grew primarily from the possibility of using it as a controllable space capsule recovery system. When that interest waned, so too did NASA's support for the innovative flight technology.
Given NASA's formal go ahead for research, Rogallo and his colleagues in the Full-Scale Research Division invested much time, energy, and emotion in the paraglider concept. Several Langley employees shared Rogallo's enthusiasm for the innovative flight technology and even conducted manned flexible wing flight research during weekends on the Outer Banks with privately owned equipment. Although qualitative in nature, these investigations proved "valuable in providing quick answers and indicating promising directions for the much more costly and time-consuming instrumented but unmanned NASA flight research."45 In wind-tunnel studies at Langley, this research covered a broad spectrum of parawing design parameters - everything from the original concept of a flexible lifting surface (indicated [385] in the engineering data as a "limp paraglider") to rigid frame gliders with conical and cylindrical canopies
As this research on the basic technology of the parawing gained momentum at Langley, NASA's STG, still at Langley at this time, grew interested in the possible application of the foldable, deployable, inflatable-frame paraglider to its Gemini EOR program. Specifically, the STG believed it might be used as part of Mercury Mark II, the follow-on to Project Mercury, which ultimately (in January 1962) became Project Gemini. The STG felt that such a wing could be deployed either before or after reentry to provide controlled glide and horizontal landing. Even on a lifting reentry body - NASA was giving "lifting body" technology considerable attention in relation to space station studies during this period (see the epilogue) -tests at Langley and other NASA facilities were showing that a parawing could improve the post-entry flight or landing characteristics.46
In early July 1961, a few weeks before the second manned Mercury flight by Gus Grissom, Gilruth's organization initiated three well-funded design study contracts on the paraglider concept with Ryan, North American, and Goodyear. Of these three companies, North American would eventually produce the most acceptable plan -a study to explore the parawing as an earth-landing system for Project Apollo.47 A few weeks later, the STG began requesting that studies of the Rogallo-type paraglider be conducted at NASA centers. At Langley this led, on 31 August, to a research authorization for "Free-Flight and Wind-Tunnel Tests of Guided Parachutes as Recovery Devices for the Apollo Type Reentry Vehicle." By late fall, all of this work came together as a formalized NASA paraglider development program, with Langley and Ames responsible for the wind-tunnel tests and the Flight Research Center for scheduling manned flight tests. Starting in mid-1963, 12 manned flight tests were actually made at Edwards with a so called Parasev.48
If the United States had not been in a hurry to go to the moon, the Rogallo paraglider might have been used as the capsule recovery system for Gemini and Apollo; of course, if the country had not been in such a hurry, it would not have gone to the moon at all in the 1960s -and perhaps would not have gone there ever. As it turned out, the paraglider became "hopelessly snarled in a financial, technical, and managerial morass."49 Richard Hallion recollects the specific problems encountered during the flight tests at Edwards:
Paraglider development involved solving major design difficulties in deploying the wing, ensuring that crew would have adequate control over the parawing-equipped craft, and providing stability, control, and handling qualities. The Flight Research Center's technical staff was never convinced that the scheme was workable. Eventually, because of poor test results and rising costs and time delays, the idea was dropped from Gemini in mid-1964 FRC engineers and pilots had believed that any vehicle so equipped might present a pilot with a greater flying challenge than contemporary advanced airplanes.
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Notice the the A-frame is evident in hung-mass gliding. 
