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The proceedings of a symposium on motorless flight research are presented. The subjects discussed are: (1) glider aerodynamic and design, (2) instrumentation, (3) structural concepts and materials, (4) soaring meteorology, (5) self-launching and ultralight sailplanes, and (6) performance testing.
The feasibility of utilizing instrumentation mounted on a sailplane wing is investigated to determine vortex wakes from a large aircraft. The instrumentation consisted of static and total pressure tubes and a rotating vane vorticity meter mounted in a pod on the glider wing tip. It was concluded that the study was not feasible.
A turbulent boundary layer on the fuselage of a glider was used to excite a Helmholtz resonator. The resonator orifice was flush with the surface and smaller than the boundary layer thickness. Resonator frequencies were chosen so they would tune with different portions of the boundary layer wall pressure spectrum. The resonators were excited at both the Helmholtz frequency and a standing wave frequency. The results show a shift in the Helmholtz frequency when the boundary layer is present. This shift indicates the degree to which the turbulence interacts with the acoustic motion in the orifice and modifies the end correction. Four of the nine resonators tested were 'strongly' excited and radiated considerable acoustic sound. This phenomenon occurs when turbulent eddies about the size of the orifice are convected past the orifice with the proper velocity to impose a frequency that matches a resonant frequency of the resonator. Turbulent eddies which are either smaller or larger than the orifice will not produce strong excitation.
A turbulent boundary layer on the fuselage of a glider is used to excite a Helmholtz resonator whose openings are comparable in size to the turbulent eddies in the boundary layer. The resonator was excited at both the Helmholtz frequency and a standing wave frequency. The level of the resonator response and the response frequency are the major results. A shift in the response frequency, compared to acoustic excitation, indicates an interaction of turbulent and acoustic motions and a modification of the orifice end correction. A strong excitation phenomenon occurs when the resonator and boundary layer are tuned, in which case turbulent eddies of about the orifice diameter in size flow past the orifice and impose a frequency equal to one of the resonant frequencies of the resonator.
A manned recoverable flying machine that operates both in air and space was discussed. This space shuttle precursor was proposed in the early 1900's by Eugen Sanger. The vehicle was especially to be used as the first stage of booster rockets or to ferry, supply and furnish rescue equipment for manned space stations. Basic concepts of the space aircraft, a cross between a powered booster rocket and an aerodynamic glider, are presented.
The development of the following Liquid-Propellant Rocket Engines (LPRE) is reviewed: (1) an alcohol-oxygen single-firing LPRE for use in wingless and winged rockets, (2) a similar multifiring LPRE for use in rocket gliders, (3) a combined solid-liquid propellant rocket engine, and (4) an aircraft LPRE operating on nitric acid and kerosene.
The first recorded balloon ascension in America took place on June 19, 1784, when an unmanned balloon was raised in a public demonstration at Bladensburg, Maryland. On June 24, 1784, a thirteen-year-old boy ascended in the same balloon. The history of actual flight during the nineteenth century was entirely concerned with balloons except for several gliders and models leading to the coming of the airship and the aircraft. The history of practical flight in America begins in the twentieth century. The described developments related to aerostatics are concerned with balloons, rigid airships, and blimps. In a review of the evolution of aeronautics, attention is given to general aviation and its search for a market, trends in military aeronautics, and commercial aviation. It is pointed out that American air transport had its birth on New Year's Day, 1914, at Tampa Bay, Florida. The evolution of astronautics during the period from 1957 to 1976 is also examined, taking into account scientific satellites, the Apollo project, the exploration of the planets with the aid of unmanned spacecraft, strategic reconnaissance satellites, missile alarm satellites, instrumental satellites for detecting nuclear and thermonuclear explosions, weather satellites, communications satellites, and earth resource survey and geodetic satellites.
A computer program was developed to calculate numerically the speed and circling polars of an aircraft when the lift and drag characteristics of the wing airfoils are known. The planform of the wing is described by variables which are optimized so that the cross-country speed of the glider is maximum for the particular type of thermal model. Two thermal models are compared and shown that with a greater wing area than now normally used the performance can be increased.
A method was developed for the design of propellers of minimum induced loss matched to an arbitrary operating point characterized by disc loading (thrust or power), air density, shaft speed, flight speed, and number of blades. A consistent procedure is outlined to predict the performance of these propellers under off design conditions, or to predict the performance of propellers of general geometry. The examples discussed include a man powered airplane, a hang glider with a 7.5 kW (10 hp) 8,000 rpm engine, and an airplane-like motorsoarer.
Low speed aerodynamics of sailplanes and hang gliders are discussed. Emphasis is placed on optimal flight techniques, structures and materials, and ultralight design.
An experimental program was conducted with the pendular platform of the Oto-Rhino-Laryngology Clinic, which was developed for the investigation of disturbances of the equilibrium. The equilibrium sense of the glider pilot was emphasized. Results are presented.
Variables taken into account in glider flight strategy decisions are modeled. These include height of clouds, distance between thermals, time of day, water ballast, present altitude, weather changes, lift organization, and distance to goal, as well as the strength of the next thermal. Results of the Monte Carlo atmospheric model are discussed.
As presently envisioned, the ultralight sailplane is intermediate in size, cost and performance between current hang gliders and the lower end of the traditional sailplane spectrum. In the design of an ultralight sailplane, safety, low cost, and operational simplicity were emphasized at the expense of absolute performance. An overview of the design requirements for an ultralight sailplane is presented. It was concluded that by a judicious combination of the technologies of hang gliding, human powered flight, conventional soaring and motor gliding, an operationally and economically viable class of ultralight, self-launching sailplanes can be developed.
Research consisted of a theoretical analysis which attempts to predict aerodynamic characteristics using lifting surface theory and finite-element structural analysis as well as an experimental investigation using 1/5 scale elastically similar models in the NASA Ames 2m x 3m (7' x 10') wind tunnel. Experimental data were compared with theoretical results in the development of a computer program which may be used in the design and evaluation of ultralight gliders.
An airplane specifically designed for Mars flight is described, emphasizing its conceivable role as an aerial surveyor for visual imaging, gamma-ray and IR reflectance spectroscopy, studies of atmospheric composition and dynamics, and gravity-field, magnetic-field, and electromagnetic sounding. Possible imaging systems and surveying tasks are considered, along with a plausible mission scenario for a fleet of 12 airplanes, which would be taken to Mars in squadrons of four by three Shuttle/IUS Twin Stage/spacecraft carriers. A basic configuration closely resembling that of a competition glider is examined, and four types of airplane are discussed: hydrazine-powered cruisers and landers and electrically powered cruisers and landers. Attention is given to navigation, guidance, and control avionics, vehicle weight, the use of composite materials for the wing, and flight testing on earth.
This paper describes the mission design, scientific utilization, and prototypical design of a Mars Airplane. As a scientific platform, the airplane provides an excellent means of obtaining data in a resolution range intermediate to surface vehicles and orbiters. It has great versatility to perform a variety of missions: conduct aerial surveys, land instrument packages, collect samples, and perform atmospheric sounding. The Mars Airplane has many characteristics of a competition glider on earth. Two versions of the plane, a cruiser, and one with soft landing and takeoff capability, have been designed. Maximum range and endurance are 10,000 km and 31.1 hours with a 40-kg payload.
A glider capable of climbing while circling in an updraft at low speed with a great mount of lift while gliding to the next updraft at high speed and with minimal altitude loss was designed. The wing profile design alleviates several problems and leaves no gap between wind and flap. A constant thickness flap eliminates the need for a flexible contour section which in turn reduces control effort. The conventional method of banking with ailerons is retained. Improved performance is demonstrated.
Research was based on a series of mechanical, electrical, and cinematographic instruments developed to measure various features of air current behavior as well as bird and airplane flight. Investigation of rising obstruction and thermal currents led to a theory of bird flight, especially of the gliding and soaring types. It was shown how a knowledge of bird flight can be applied to glider and ultimately motorized aircraft construction. The instruments and methods used in studying stress in airplanes and in comparing the lift to drag ratios of airplanes and birds are described.