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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Efficient Near-Field to Mid-Field Sonic Boom Propagation Using a High-Order Space Marching Method

An efficient strategy for propagating sonic boom signatures from a near-field Computational Fluid Dynamics (CFD) solution to the mid-field is presented. The method is based on a high-order accurate finite-difference discretization of the 3D Euler equations on a specially designed curvilinear grid and a single sweep space marching solution algorithm. The new approach leads to more than a factor of two reduction in overall computational resources compared to the current method used to propagate near-field sonic booms to the ground. Accuracy and efficiency of the near-field to mid-field process is demonstrated using a selection of test cases from the AIAA Sonic Boom Prediction Workshops. Azimuthal dependence of nonlinear wave propagation from the near-field to mid-field is analyzed along with its effects on the ground level noise.

Housman, Jeffrey A.↗
NASA NTRS2012

Exhaust Plume Effects on Sonic Boom for a Delta Wing and a Swept Wing-Body Model

Supersonic travel is not allowed over populated areas due to the disturbance caused by the sonic boom. Research has been performed on sonic boom reduction and has included the contribution of the exhaust nozzle plume. Plume effect on sonic boom has progressed from the study of isolated nozzles to a study with four exhaust plumes integrated with a wing-body vehicle. This report provides a baseline analysis of the generic wing-body vehicle to demonstrate the effect of the nozzle exhaust on the near-field pressure profile. Reductions occurred in the peak-to-peak magnitude of the pressure profile for a swept wing-body vehicle. The exhaust plumes also had a favorable effect as the nozzles were moved outward along the wing-span.

Castner, Raymond↗
NASA NTRS2004

Human Response to Simulated Low-Intensity Sonic Booms

NASA's High Speed Research (HSR ) program in the 1990s was intended to develop a technology base for a future High-Speed Civil Transport (HSCT). As part of this program, the NASA Langley Research Center sonic boom simulator (SBS) was built and used for a series of tests on subjective response to sonic booms. At the end of the HSR program, an HSCT was deemed impractical, but since then interest in supersonic flight has reawakened, this time focusing on a smaller aircraft suitable for a business jet. To respond to this interest, the Langley sonic boom simulator has been refurbished. The upgraded computer-controlled playback system is based on an SGI O2 computer, in place of the previous DEC MicroVAX. As the frequency response of the booth is not flat, an equalization filter is required. Because of the changes made during the renovation (new loudspeakers), the previous equalization filter no longer performed as well as before, so a new equalization filter has been designed. Booms to be presented in the booth are preprocessed using the filter. When the preprocessed signals are presented into the booth and measured with a microphone, the results are very similar to the intended shapes. Signals with short rise times and sharp "corners" are observed to have a small amount of "ringing" in the response. During the HSR program a considerable number of subjective tests were completed in the SBS. A summary of that research is given in Leatherwood et al. (Individual reports are available at http://techreports.larc.nasa.gov/ltrs/ltrs.html.) Topics of study included shaped sonic booms, asymmetrical booms, realistic (recorded) boom waveforms, indoor and outdoor booms shapes, among other factors. One conclusion of that research was that a loudness metric, like the Stevens Perceived Level (PL), predicted human reaction much more accurately than overpressure or unweighted sound pressure level. Structural vibration and rattle were not included in these studies.

Sullivan, Brenda M.↗
NASA NTRS1982

Sonic boom measurement test plan for Space Shuttle STS-5 launch

Sonic booms measurements are obtained at key locations within the focus region and the lateral attenuation rate during ascent is determined in order to assess the validity of existing capability to predict the extent of focus boom area, the number of booms within the various zones (focus and nonfocus regions), the overpressures, and focus factors. The sonic boom focus region, consists of a region on the ground (in the form of an inverted 'horseshoe' pattern) in which higher than nominal overpressures can occur.

Henderson, H. R.↗
NASA NTRS1990

A study of sonic boom overpressure trends with respect to weight, altitude, Mach number, and vehicle shaping

This paper presents and discusses trends in nose shock overpressure generated by two conceptual Mach 2.0 configurations. One configuration was designed for high aerodynamic efficiency, while the other was designed to produce a low boom, shaped-overpressure signature. Aerodynamic lift, sonic boom minimization, and Mach-sliced/area-rule codes were used to analyze and compute the sonic boom characteristics of both configurations with respect to cruise Mach number, weight, and altitude. The influence of these parameters on the overpressure and the overpressure trends are discussed and conclusions are given.

Needleman, Kathy E.↗
NASA NTRS1993

Recent laboratory studies of loudness and annoyance to sonic booms

NASA Langley Research Center is supporting NASA High-Speed Research Program efforts to develop an updated technology base for future high-speed civil transport aircraft. Part of this effort involves (a) quantification of loudness and annoyance benefits due to sonic boom shaping and (b) determination of boom exposures acceptable to the public. Langley is conducting a series of laboratory studies to investigate in detail the subjective reactions to a wide range of shaped sonic boom signatures and to examine several metrics as estimators of sonic boom subjective effects. Results from several of these studies, as well as results obtained by other investigators, demonstrated that substantial reductions in the loudness of sonic booms can be achieved by careful shaping of the boom signatures. Recent Langley studies extended this work to include: (a) quantification of subjective effects due to booms heard indoors, (b) determination of subjective reactions due to ground-reflected booms, and (c) determination of subjective reactions to simulator reproductions of booms recently at White Sands Missile Range.

Leatherwood, Jack D.↗
NASA NTRSDate not supplied

Influence of Atmospheric Variability on Predicted Sonic Boom Metrics

As part of the Quesst mission, NASA will fly the X-59 aircraft over selected communities to survey community responses to low sonic booms. Previously, we developed a Kalman filter method to estimate the loudness metrics experienced by each survey participant during each flight. The Kalman filter fuses acoustic measurements with predictions from PCBoom, a sonic boom propagation model. PCBoom requires vertical profiles of the temperature, humidity, and wind to propagate sonic booms through the atmosphere and predict the loudness metrics at the ground. Prior to each X-59 flight, NASA will launch weather balloons to measure the vertical atmospheric profile. However, the atmosphere changes continually with geographic location and time. The purpose of this work is to determine where and when to launch these weather balloons to minimize the uncertainty in the predicted loudness metrics caused by atmospheric variability. We analyzed the effect of atmospheric variability on the predicted Perceived Level in three communities in different climate zones in the United States. To achieve acceptable uncertainty in the Perceived Level, weather balloons should be launched from at least two different sites within the survey area within one hour of each X-59 flight.

sonic boom↗
NASA NTRS1992

Analysis of sonic boom data to quantify distortions of shock profiles

Researchers at Penn State have been examining some sonic boom waveforms recorded during overflights by the Air Force which have become available to NASA and its contractors. The quality of the digitized data and the supporting meteorological data was such that one could test the applicability of molecular relaxation theories. In the late sixties, it had been supposed that the finite rise times in the absence of turbulence had neglected the vibrational relaxation of nitrogen molecules. Bass et al. have demonstrated that molecular relaxation definitely gives the correct order of magnitude of the observed rise times. However, the Air Force data in conjunction with the recent steady-state shock profile model theory of Kang and Pierce give the first opportunity to make a detailed quantitative assessment of the molecular relaxation hypothesis. Currently an investigation is ongoing to establish a method of quantifying the distortion of a sonic boom wave from a classic N-wave shape using the Air Force data taken at Edwards AFB in 1987. Using the premise that energy will be conserved approximately for a sonic boom wave both before and after the boom passes through the Earth's turbulent boundary layer, a classic undistorted waveform is constructed from the distorted signature received at the ground. A correlation between the mean-squared deviation of the distorted and undistorted waveforms and the distance the boom travels through the turbulence is sought.

Gionfriddo, Thomas A.↗
NASA NTRS1972

Sonic-boom measurements for SR-71 aircraft operating at Mach numbers to 3.0 and altitudes to 24384 meters

Sonic-boom pressure signatures produced by the SR-71 aircraft at altitudes from 10,668 to 24,384 meters and Mach numbers 1.35 to 3.0 were obtained as an adjunct to the sonic boom evaluation program relating to structural and subjective response which was conducted in 1966-1967 time period. Approximately 2000 sonic-boom signatures from 33 flights of the SR-71 vehicle and two flights of the F-12 vehicle were recorded. Measured ground-pressure signatures for both on-track and lateral measuring station locations are presented and the statistical variations of the overpressure, positive impulse, wave duration, and shock-wave rise time are illustrated.

Maglieri, D. J.↗
NASA NTRS1995

Ground-recorded sonic boom signatures of F-18 aircraft formation flight

Two F-18 aircraft were flown, one above the other, in two formations, in order for the shock systems of the two aircraft to merge and propagate to the ground. The first formation had the canopy of the lower F-18 in the inlet shock of the upper F-18 (called inlet-canopy). The flight conditions were Mach 1.22 and an altitude of 23,500 ft. An array of five sonic boom recorders was used on the ground to record the sonic boom signatures. This paper describes the flight test technique and the ground level sonic boom signatures. The tail-canopy formation resulted in two, separated, N-wave signatures. Such signatures probably resulted from aircraft positioning error. The inlet-canopy formation yielded a single modified signature; two recorders measured an approximate flattop signature. Loudness calculations indicated that the single inlet-canopy signatures were quieter than the two, separated tail-canopy signatures. Significant loudness occurs after a sonic boom signature. Such loudness probably comes from the aircraft engines.

Bahm, Catherine M.↗
NASA NTRS1992

Georgia Tech sonic boom simulator

To examine the building and human response to sonic boom in the range 3 Hz to 30 Hz, Georgia Institute of Technology is building a special acoustic driver system to simulate sonic boom. To support the NASA LaRC program on building and human response, this simulator's capability has been extended to an upper frequency of 4 KHz. A residential test house was made available by Georgia Tech for these tests. At the time of preparation of this document, most of the acoustic drivers and the associated electronics have been built and assembled. The system has, however, not been fully tested. The following pages provide an overview of the progress to date. The acoustic driver systems, and the principle of their operation together with the test house are described. Future plans are also summarized.

Ahuja, Krish K.↗
NASA NTRS2002

Sonic Boom Testing Performed in NASA Glenn Research Center's 10- by 10-Foot Supersonic Wind Tunnel

One of the current impediments to the establishment of supersonic transports as a viable part of the commercial aviation fleet is the sonic boom effect. This effect is created when a vehicle achieves supersonic speeds and creates a shock wave (an immediate pressure change) that impinges on the ground. The resulting sonic boom can be both heard and felt on the ground, and it traverses the ground along the flight path of the vehicle. The environmental impact of this sonic boom effect is currently regulated by only allowing supersonic flight on over-water flight paths. The ability to measure the pressure signature of an aircraft configuration would allow researchers to identify the sources and the relative magnitude of that source on the aircraft pressure signature. It would also allow for the development and validation of computer codes to predict the sonic boom effects of an aircraft configuration.

Stark, David E.↗
NASA NTRS1996

SR-71 Experiment On Propagation Of Sonic Booms

Flight experiment conducted using an SR-71, F-16XL, and YO-3A airplane to study propagation of sonic booms. Work geared toward developing high-speed civil transport (HSCT) aircraft. Data used to soften sonic booms from supersonic aircraft. Techniques used in experiment to measure pressures and relative aircraft separation accurately also under consideration for use in other flight research unrelated to sonic booms.

Haering, Edward A., Jr.↗
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.↗