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ensured structural integrity. Seven weeks after the project was initiated the team rolled out the Paresev 1.
The Paresev (Paraglider Research Vehicle) was an indirect outgrowth of kite-parachute studies by NACA Langley engineer Francis M. Rogallo. In early 1960s the "Rogallo wing" seemed an excellent means of returning a spacecraft to Earth. The delta wing design was patented by Mr. 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. The logistics became enormous and the price exorbitant, plus NASA pilots and engineers felt some baseline experience like building a vehicle and flying a Parawing should be accomplished first.
The Paresev was used to gain in-flight experience with four different membranes (wings) and was not used to develop the more complicated inflatable deployment system. The Paresev was designed by Charles Richards, of the Flight Research Center's Vehicle and System Dynamics Branch, with the rest of the team being: engineers, Richard Klein, Gary Layton, John Orahood, and Joe Wilson; from the Maintenance and Manufacturing Branch: Frank Fedor, LeRoy Barto; Victor Horton as Project Manager, with Gary Layton becoming Project Manager later on in the Program. Mr. Paul Bikle, Director of the Center gave instructions that were short and to the point: build a single-seat Paraglider and "do it quick and cheap."
The Paresev was unpowered, the "fuselage" an open framework fabricated of welded 4130 steel tubing referred to as a "space frame." The keel and leading edges of the wings were constructed of 2 1/2-inch diameter aluminum tubing. The leading edge sweep angle was held constant at 50 degrees by a rigid spreader bar. Additional wing structure fabricated of steel tubing ensured structural integrity. Seven weeks after the project was initiated the team rolled out the Paresev 1. It resembled a grown-up tricycle, with a rudimentary seat, an angled tripod mast, and, perched on top of the mast, a Rogallo-type parawing. The pilot sat out in the open, strapped in the seat, with no enclosure of any kind. He controlled the descent rate by tilting the wing fore and aft, and turned by tilting the wing from side to side with a control stick that came from overhead. 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 started immediately.
There was one space frame built called the Paresev that used four different wing types. Paresev 1 had a linen membrane, with the control stick coming from overhead in front of the pilots seat. Paresev 1A had a regulation control stick and a Dacron membrane. Paresev 1B had a smaller Dacron membrane with the space frame remaining the same. Paresev 1C used a half-scale version of the inflatable Gemini parawing with a small change to the space frame.
All "space frames," regardless of the parawing configuration, had a shield with "Paresev 1-A" and the NASA meatball on the front of the vehicle.
After the space frame was completed a sailmaker was asked to sew the wing membrane according to the planform developed by NASA Flight Research Center personnel. He suggested using Dacron instead of the linen fabric chosen, but yielded to the engineer's specs. A nylon bolt rope was attached in the trailing edge of the 600 square foot wing membrane. The rope was unrestrained except at the wing tips and was therefore free to equalize the load between the two lobes of the wing.
This worked reasonably well, but flight tests 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 fifth flight aloft lasted 10 seconds. On a ground tow the Paresev and pilot fell 10 feet. Considerable damage was done to the Paresev with the pilot being taken to the base hospital. Injuries sustained by the pilot were not serious.
After this accident the Paresev was extensively rebuilt and renamed, Paresev-1A.
The sailmaker was asked again to construct a 600 square foot membrane the way he wanted to. The resulting wing membrane had excellent contours in flight and was made from 6 ounce Dacron. The space frame was rebuilt with more sophistication than the Paresev 1 had. The shock absorbers were Ford automotive parts, the wing universal joint was a 1948 Pontiac part, and the tires and wheels were from a Cessna 175 aircraft. The overhead stick was replaced with a stick and pulley arrangement that operated more like conventional aircraft controls. This vehicle had much improved stick forces and handling qualities.
The instrumentation used to obtain data was quite crude, partially as a result of the desire to keep the program simple and low in cost and also because there was no onboard power. To measure performance, technicians installed a large alpha vane on the wing apex with a scale at the trailing edge that the pilot could read directly. A curved bubble level measured the vehicle's attitude, and a Fairchild camera recorded the glide slope.
The Paresev 1-B used the Paresev 1-A space frame with a smaller Dacron wing (400 square feet) and was flight tested to evaluate its handling qualities with lower lift-to-drag values. One project NASA engineer described its gliding ability as "pretty scary."
The space frame of the vehicle remained almost unchanged from the earlier vehicles. However, a new control box gave the pilot the ability to increase or decrease the nitrogen in the inflatable wing supports to compensate for the changing density of the air. Two bottles of nitrogen provided an extra supply of nitrogen. The vehicle featured an inflatable wing, 179 square feet in area.
Actually the whole wing was not inflatable; the three chambers that acted as spars and supported the wing inflated. The center spar ran fore and aft and measured 191 inches; two other inflatable spars formed the leading edges. These three compartments were filled with nitrogen under pressure to make them rigid. The Paresev in this configuration was expected to closely approximate the aerodynamic characteristics that would be encountered with the Gemini space capsule with a parawing extended. The Paresev was very unstable in flight with this configuration.
The first Paresev flights began with tows across the dry lakebed, in 1962, using a NASA vehicle, a International Harvester carry-all (6 cylinder). Eventually airtows were done using Stearman sport biplane (450 hp), a Piper Super Cub (150-180 hp), Cessna L-19 ( 200 hp Bird Dog) and a Boeing-Vertol HC-1A. Speed range of the Paresev was about 35 - 65 mph.
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 Gus Grissom, astronaut. The Paresev was legally transferred to the National Air Museum of the Smithsonian Institute, Washington, D.C. However, the Smithsonian loaned the Paresev to the Experimental Aircraft Museum in Oshkosh, Wisconsin, in January 1968.
Despite its looks, the Paresev was a useful research aircraft that helped develop a new way to fly. 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.