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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Sonic boom generation propagation and minimization.

Consideration of the possibility of reducing sonic boom noise to a level acceptable in populated areas. A detailed study is made of the possibility of predicting sonic boom generation, taking into account the effect of atmospheric conditions, air turbulence, and the effect of the shape and condition of the ground where people are located. The relation between the shape of the sonic boom signature on the ground and the aircraft shape is shown to be an important factor governing the use of supersonic aircraft over populated areas.

Ferri, A.↗
NASA NTRS1972

Sonic-boom-induced building structure responses including damage.

Concepts of sonic-boom pressure loading of building structures and the associated responses are reviewed, and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic-boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of such other phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data from laboratory models and full-scale building tests are summarized, and these data are compared, where possible, with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic-boom-induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.

Clarkson, B. L.↗
NASA NTRS1973

Application of sonic-boom minimization concepts in supersonic transport design

The applicability of sonic boom minimization concepts in the design of large supersonic transport airplanes capable of a 2500-nautical-mile range at a cruise Mach number of 2.7 is considered. Aerodynamics, weight and balance, and mission performance as well as sonic boom factors, have been taken into account. The results indicate that shock-strength nominal values of somewhat less than 48 newtons/sq m during cruise are within the realm of possibility. Because many of the design features are in direct contradiction to presently accepted design practices, further study of qualified airplane design teams is required to ascertain sonic boom shock strength levels actually attainable for practical supersonic transports.

Carlson, H. W.↗
NASA NTRS1973

Results of an experimental program for the development of sonic inlets for turbofan engines.

Results of a current program for sonic inlet technology development are presented. This program includes configuration and mechanical design selection of concepts, aerodynamic design description of the models, and results of test evaluation. In the test program several sonic inlet concepts were tested and compared for aerodynamic and acoustic performance. Results of these comparative evaluations are presented. Near-field measurements were taken inside the sonic inlet on several inlet models. Results of these tests are discussed with respect to the effect of Mach number gradients on noise attenuation and rotor shock wave attenuation, and boundary layer effects on noise propagation. The test facilities and experimental techniques employed are described briefly.

Klujber, F.↗
NASA NTRS1973

The design or operation of aircraft to minimize their sonic boom.

Means of reducing or eliminating the sonic boom through aerodynamic design or aircraft operation are discussed. These include designing aircraft to minimize or eliminate certain features of the overpressure signature, operating aircraft at slightly supersonic speeds so that the sonic boom does not reach the ground, and seeking reductions through the high altitude-high speed flight conditions of hypersonic transports. A simple computer program has been developed that determines the area development of the equivalent body of revolution required to minimize various sonic boom signature parameters.

Seebass, A. R.↗
NASA NTRS1973

A study to determine the feasibility of a low sonic boom supersonic transport.

The objective of this study was to determine if a supersonic transport designed to produce a sonic boom signature with low overpressure represented a feasible concept. Two design goals were chosen: an overpressure of 1.0 psf or less for cruise at Mach 2.7 and an overpressure of 0.5 psf for cruise at Mach 1.5. Projected 1985 technology was assumed for the analysis. The principal effort was to develop cruise configurations capable of meeting the sonic boom goals. The Mach 2.7 goal was achieved with a blended arrow wing configuration and the Mach 1.5 design was a low arrow wing configuration with a horizontal tail. The development of these airplanes is summarized and the concept of a low sonic boom SST is evaluated.

Kane, E. J.↗
NASA NTRS1973

Research of the sonic-boom problem

Wind tunnel tests were conducted to determine the characteristics of sonic booms. A theoretical examination of nonlinear effects in near and far flow fields, as well as sonic boom shock strength, is reported. A study of the Mach lines and bicharacteristics in three dimensional flow was pursued. The direction derivatives if the bicharacteristics were calculated in a general three dimensional flow field. A second order theory for supersonic flow past slender bodies was developed. Formulas relating flow deflections to the Whitham F-function were derived, which permitted determination of the sonic boom strength from wind tunnel measurements fairly close to the body.

Drougge, G.↗
NASA NTRS1974

Sonic-boom ground pressure measurements from the launch and reentry of Apollo 16

Sonic-boom pressure signatures recorded during the launch and reentry phases of the Apollo 16 mission are presented. Five measurements were obtained along the vehicle ground track: 69 km (37.3 n. mi.) 92 km (49.8 n. mi.), and 130 km (70.3 n. mi.) down range from the launch site during ascent, and at 185 km (100 n. mi.) and approximately 5.5 km (3 n. mi.) from the splash-down point during reentry. Tracings of the measured signatures are included along with values of the overpressure, impulse, time duration, and rise times. Also included are brief descriptions of the launch and recovery test areas in which the measurements were obtained, the sonic-boom instrumentation deployment, flight profiles, and operating conditions for the launch vehicle and spacecraft, surface weather information at the measuring sites, and high-altitude weather information for the general measurement areas. Comparisons of the sonic-boom overpressures from Apollo 15 and 16 along with those from current aircraft are also presented.

Henderson, H. R.↗
NASA NTRS1973

Shuttle sonic boom - Technology and predictions

Because the shuttle differs significantly in both geometric and operational characteristics from conventional supersonic aircraft, estimation of sonic boom characteristics required a new technology base. The prediction procedures thus developed are reviewed. Flight measurements obtained for both the ascent and entry phases of the Apollo 15 and 16 and for the ascent phase only of the Apollo 17 missions are presented which verify the techniques established for application to shuttle. Results of extensive analysis of the sonic boom overpressure characteristics completed to date are presented which indicate that this factor of the shuttle's environmental impact is predictable, localized, of short duration and acceptable. Efforts are continuing to define the shuttle sonic boom characteristics to a fine level of detail based on the final system design.

Holloway, P. F.↗
NASA NTRS1973

Parametric interactions between Alfven waves and sonic waves

Parametric interactions between a sonic pump wave and a weak Alfven wave are studied. It is shown that if the Alfven-wave velocity Va is small relative to the sonic-wave velocity Vs there is a time-growing instability leading to the increase of the Alfven wave at the expense of the sonic wave. This phenomenon can be of importance in solar and stellar physics. For Va large relative to Vs, the interaction is of the stop-band type.

Elachi, C.↗
NASA NTRS1974

Measurements of sonic-boom overpressures from Apollo space vehicles

This paper presents representative results of sonic-boom overpressure data recorded during the launch and reentry of the Apollo 15 and 16 space vehicle systems. Comparisons are made between measured overpressures and those predicted using available theory. The measurements were obtained along the vehicle ground track at 68, 87, 92, 129, and 970 km downrange from the launch site during ascent, and at 9, 13, 55, 185, and 500 km from the splash-down point during reentry. Also included are tracings of the sonic-boom signatures along with a brief description of the launch and recovery test areas in which the measurements were obtained, the sonic-boom instrumentation deployment, flight profiles and operating conditions, and high-altitude weather information for the general measurement areas.

Hilton, D. A.↗
NASA NTRS1974

Sonic-boom measurements in the focus region during the ascent of Apollo 17

Sonic-boom pressure signatures recorded during the ascent phase of Apollo 17 are presented. The measurements were obtained onboard six U.S. Navy ships positioned along the ground track of the spacecraft vehicle in the area of expected focus resulting from the flight path and acceleration of the vehicle. Tracings of the measured signatures are presented along with values of the maximum positive overpressure, positive impulse, signature duration, and bowshock rise time. Also included are brief descriptions of the ships and their location, the deployment of the sonic-boom instrumentation, flight profiles and operating conditions for the launch vehicle and spacecraft, surface-weather and sea-state information at the measuring sites, and high-altitude weather information for the general measurement areas. Comparisons of the measured and predicted sonic-boom overpressures for the Apollo 17 mission are presented. The measured data are also compared with data from the Apollo 15 and 16 missions and data from flight test programs of various aircraft.

Henderson, H. R.↗
NASA NTRS1974

Laboratory study of sonic booms and their scaling laws

This program undertook to seek a basic understanding of non-linear effects associated with caustics, through laboratory simulation experiments of sonic booms in a ballistic range and a coordinated theoretical study of scaling laws. Two cases of superbooms or enhanced sonic booms at caustics have been studied. The first case, referred to as acceleration superbooms, is related to the enhanced sonic booms generated during the acceleration maneuvers of supersonic aircrafts. The second case, referred to as refraction superbooms, involves the superbooms that are generated as a result of atmospheric refraction. Important theoretical and experimental results are briefly reported.

Toong, T. Y.↗
NASA NTRS1975

Experimentally determined aeroacoustic performance and control of several sonic inlets

Low speed wind tunnel tests were conducted to determine the aeroacoustic performance of several model sonic inlets. The results were analyzed to indicate how inlet aeroacoustic characteristics were affected by inlet design and operating conditions. A system for regulating sonic inlet noise reduction was developed and tested. Results indicate that pressure losses at forward velocity may be substantially less than those at static conditions. This is particularly true for translating centerbody inlets with the centerbody extended in the approach and landing position. Operation to simulated take-off incidence angles of 50 deg was demonstrated with good inlet performance. Results suggest that at takeoff, with 0 deg incidence angle, sonic inlet total pressure losses need not exceed those generated by skin friction for sound pressure level reductions to at least 15 dB. Inlet sound pressure level reduction was regulated to within approximately plus or minus 1 dB by controlling inlet surface static pressure measured at the diffuser exit.

Miller, B. A.↗
NASA NTRS1976

Sonic environment of aircraft structure immersed in a supersonic jet flow stream

Test methods for determining the sonic environment of aircraft structure that is immersed in the flow stream of a high velocity jet or that is subjected to the noise field surrounding the jet, were investigated. Sonic environment test data measured on a SCAT 15-F model in the flow field of Mach 1.5 and 2.5 jets were processed. Narrow band, lateral cross correlation and noise contour plots are presented. Data acquisition and reduction methods are depicted. A computer program for scaling the model data is given that accounts for model size, jet velocity, transducer size, and jet density. Comparisons of scaled model data and full size aircraft data are made for the L-1011, S-3A, and a V/STOL lower surface blowing concept. Sonic environment predictions are made for an engine-over-the-wing SST configuration.

Guinn, W. A.↗
NASA NTRS1976

Sonic boom theory - Its status in prediction and minimization

This paper gives a brief review of the currently accepted understanding of sonic boom phenomena and describes the manner in which modified linearized theory and geometric acoustics are used to predict the sonic boom caused by a complex aircraft configuration. Minimization methods that have evolved in recent years are discussed with particular attention given to a method developed by Seebass and George for an isothermal atmosphere which was modified for the real atmosphere by Darden. An additional modification which permits the relaxation of the nose bluntness requirement in the defining aircraft is also discussed. Finally, an overview of current areas of sonic boom research is given.

Darden, C. M.↗
NASA NTRS1975

Sonic spark chambers for cosmic-ray experiments

The sonic spark chamber provides an attractive high resolution hodoscope for low flux cosmic ray experiments. Spark position is determined by measurement of the time of flight of the sonic shock front from the spark position to a number of piezoelectric transducers placed at the periphery of the chamber. For each spark, four quantities must be determined: the spark coordinates, the sound velocity, and the spark 'size'. By over-determining the four parameters, high accuracy is possible. With eight sonic transducers, air-gap spark positions were measured with an error of less than 100 microns everywhere over a 1 sq m region.

Ahlen, S. P.↗
NASA NTRS1979

Some effects of applying sonic boom minimization to supersonic cruise aircraft design

This paper presents a discussion of an aircraft shaping method to control sonic boom over-pressure levels along with the analysis of wind-tunnel data which validated the method. The results indicate that the sonic boom minimization method can guide the design team choices of aircraft planform and component arrangement toward a low-boom-level configuration while permitting sufficient freedom and flexibility to satisfy other design criteria. Further, it is shown that off-design flight conditions do not drastically change the overpressure sonic boom shape and strength.

Mack, R. J.↗