Sonic Boom Characteristics Research Articles

Development of computer code and calculation of the propagation of sonic boom to the ground in a real atmosphere

One of the main problems in the development of a supersonic aircraft of the second generation is to ensure a safe level of the sonic boom impact on the environment. Achieving such level at the preliminary design stage is possible with the help of reliable methods for calculating the characteristics of the sonic boom due to impossibility of tube experiments at far field and expensiveness of real flight tests. This paper presents method for determining the shape of the overpressure signatures in the generalized form of an augmented Burgers equation for the case of disturbances propagation in a moving medium (atmosphere with wind). Based on the presented method, the computer code “vBoom” has been developed. The calculation results of the sonic boom characteristics (overpressure waveforms, the loudness in different metrics and the sonic boom carpet on the ground) are presented in comparison with the results obtained by NASA within the international seminar SBPW3 [1] (Sonic Boom Prediction Workshop).

The aeroballistic technique for studying sonic-boom characteristics

In the present paper, we analyze a suggestion implying the use of the aeroballistic technique for carrying out studies of shock-wave (sonic-boom) characteristics at large distances from the freely flying model. An analysis of the main engineering solutions ensuring the possibility of implementing the proposed experimental facility in the range of flight velocities of examined models from one to two Mach numbers is performed. A list of scientific and engineering problems pertaining to the study of sonic-boom characteristics in the middle and far zones which can be experimentally tackled with the help of the proposed facility is presented.

Controlling the level of the sonic boom generated by a flying vehicle by means of cryogenic forcing. 3. Physical justification of the cryogenic action

The influence of the basic factors of cryogenic forcing on formation of the middle zone on the sonic boom and aerodynamic characteristics of the flying vehicle is studied by experimental and numerical methods. Experimental data obtained with alcohol or liquid nitrogen as an injected liquid are used for comparisons; as a result, the total effect of temperature and coolant evaporation can be determined. The influence of temperature is studied by means of numerical simulations of the cryogenic action of distributed injection of air. A comparison of numerical and experimental data reveals the effect of the coolant evaporation process on perturbed flow formation. It is demonstrated that evaporation of the coolant outgoing onto the vehicle surface should be intensified to increase the efficiency of cryogenic forcing (to decrease the coolant flow rate).

Effects of Meteorological Variability on Sonic Boom Propagation from Hypersonic Aircraft

A numerical study of primary sonic boom propagation from a hypersonic Mach 6 cruise aircraft is performed, including the effects of nonlinearity, atmospheric absorption and dispersion, and atmospheric stratification. A second-order split-step algorithm alternating between the time domain for nonlinearity and the frequency domain forabsorptionallowsforafasterconvergenceofresultsthanconventional first-orderalgorithms.Dailyvariabilityof meteorological parameters is used to investigate the variability of sonic boom shock overpressure, rise time, and carpet width over the span of a year. Two locations are chosen based on their difference in climates, especially humidity, and two flight directions are considered. It is found that sonic boom rise time is especially susceptible to variability in humidity, whereas shock overpressure and carpet width are most sensitive to winds. A statistical analysis and comparison between hypersonic and supersonic aircraft configurations reveal that all sonic boom characteristics are highly dependent on the aircraft and flight conditions, so that generalizations of statistics cannot be made. simulated for lower Mach numbers than what is being considered in the present study. This paper investigates the sonic boom ground impact for an aircraft flying at Mach 6 cruise at a 28 km altitude. Sonic boom impactisestimatedintermsofthepeakoverpressureattheverticalof the flight track, the front shock rise time, and the lateral extent of the geometricalcarpet.The firsttwoparametersprovideanestimationof theloudestboomlikelytoinducemaximumannoyance,andthethird parameter estimates the lateral impact of the boom during the cruise phase. As a sonic boom propagates over long distances, it isstrongly affected by the atmosphere and thus is dependent on meteorology and geographical location. The impact is quantified statistically, based on numerical simulations using an extensive meteorological database. A numerical study of primary sonic boom propagation from the Mach 6 aircraft is performed, including the effects of nonlinearity, absorption and dispersion, and stratification. Tests of accurate numerical parameters for varying strengths of nonlinearity and absorptionareperformedtodeterminethemostefficientalternatives. An extended absorption model is adopted that accounts for changes in the atmosphere up to the high flight altitude required by Mach 6 operation. The effects of meteorological variability on sonic boom propagation are investigated by considering the climate at two different geographical locations over the course of a year at a 6 h resolution. Vertical gradients of meteorological parameters at a coastal areawithhighgroundhumidityarejuxtaposedwith thosefor a desert region. Key sonic boom parameters are compared with predictions for other aircraft configurations at Mach 1.6 and with a previous study for a Mach 2 aircraft (9). Section II presents the meteorological data. In the following Sec. III, an extended absorption model is presented to take into account the high flight altitudes (about 30 km) for the Mach 6 case. Modifications to include high-altitude sound absorption in the sonic boom code are briefly presented. A brief explanation of the theory behind the sonic boom algorithm is outlined in Sec. IV, and Sec. V presents the specific parameters used in the simulations. Sonic boom predictions at the ground level are synthesized and compared with other cases and previous studies in Sec. VI.

Variability of focused sonic booms from accelerating supersonic aircraft in consideration of meteorological effects

Statistics of the meteorologically induced variability of focused sonic boom characteristics due to unsteady, accelerated supersonic flights were derived. The simulations were performed with an advanced sonic boom software including a numerical solver of the Nonlinear Tricomi Equation modeling the focused sound pressure field around caustics. A one-year set of daily meteorological data along the Northern Atlantic flight corridor was used as input. The statistics comprise the location, strength and geometrical extension of caustics at ground level for assumed flights of a supersonic commercial transport from Paris to New York and back. Caustics only occurred during the acceleration phase above the English Channel for flights from Paris to New York, never during the deceleration phase of return flights. The mean value of the maximum focused overpressure is found to be about 4 times the maximum overpressure for cruise flight at Mach 2 in similar conditions, but shows a large variability. The caustics intersection with the ground varies between 3 and 8km in width and between 30 and 180km in length. A linear correlation analysis showed the relationship between meteorological profile shape parameters and the focused sonic boom characteristics.

Meteorologically induced variability of sonic-boom characteristics of supersonic aircraft in cruising flight

The influence of the meteorological variability on the characteristics of the primary sonic boom emerging from an aircraft in cruising flight is investigated. The sonic-boom propagation is calculated by means of an advanced ray-tracing algorithm which takes meteorological influences into account. Real meteorological situations are considered based on a full 10-year data set in 12- and/or 24-h resolution. Three different climate regions are studied: a mid-latitude coastal sea region, a tropical coastal sea area, and a subpolar land region. Frequency distributions of sonic-boom characteristics such as wave amplitude, rise time, and carpet width are shown for each area, all seasons, and opposing flight directions. It turns out that while variability is low at the ground track, it is high laterally for carpet width or boom amplitude at the outer carpet edges. A correlation analysis is applied which shows specific relationships between meteorological profile parameters and acoustical response. In addition, a meteorological classification is introduced and tested.

Statistical and numerical study of the relationship between turbulence and sonic boom characteristics

A statistical analysis of data collected by NASA during supersonic flight operations in the 1960’s shows that turbulence is related to characteristics of the sonic boom. Both convective and mechanical turbulence increase the rise times and produce peaked and rounded waveforms. Convective conditions are especially conducive to the formation of peaked waveforms. A physical model has been developed to investigate the interaction of sonic booms with turbulence. Scattering center-based calculations demonstrate that scattering from eddies with sizes from 10 to 100 m is effective in producing long rise times and all major types of non-N boom shapes.

Sonic boom of the oblique flying wing

This article presents an analysis of oblique flying wing sonic boom characteristics. This long asymmetric wing provides a reduction in sonic boom loudness as well as aerodynamic and structural improvements over conventional transports. The wing is represented by an oblique line equivalent area distribution, a panel model, and a high-definition surface model. The near-field pressure signature of the first two representations is found using the Whitham F-function method applied to the oblique equivalent area distribution and the panel model. The near-field pressure distribution of the high-definition surface model was found using TranAir, a full-potential analysis code. Good agreement between the methods was found. The near-field signature is extrapolated through the standard atmosphere by the Thomas waveform parameter method. The asymmetry in the geometry leads to an asymmetrical sonic boom under the flight track. The bow shock amplitude is typically between 50-75 N/m2 depending on the size, weight, and altitude of the configuration. The aft shock has only one-half the amplitude of the bow shock due to favorable volume-lift interference. This article also includes a simple method to estimate the maximum sonic boom overpressures of oblique flying wings.

Sonic boom measurement for space shuttle

Sonic boom measurements have been obtained during six flights of the Space Transportation System (STS). Information regarding sonic boom signature characteristics that include overpressure, period, and shock‐rise‐time will be discussed and some comparisons with predictions will be shown. Measurements of the sonic boom generated by the orbiter during descent flight phases were made on STS‐1, STS‐2, STS‐4, and STS‐11. Ascent measurements were obtained during STS‐5 and STS‐7 launches. The objectives were (1) to define sonic boom characteristics of the STS during both launch and entry, and (2) to assess the validity of a semi‐empirical method used previously to predict 2, 4, and 11 entries into Edwards Air Force Base or Kennedy Space Center. Sonic booms during descent are of particular interest to NASA because of the population centers exposed. During ascent from the Kennedy, no land masses are impacted by the pressure wave. However, ascent booms for STS launches are important to the Air Force because of their plan to launch the Shuttle from Vandenberg Air Force Base. From Vandenberg, the launch boom may impact (for some launch azimuths) the Channel Islands and, under some conditions, the California coast itself.

Review of current sonic boom studies.

Several aspects of the sonic boom phenomena are currently under investigation at The Boeing Co. This work, supported by the NASA and the FAA, includes an in-depth analysis of sonic boom measurements recorded at the BREN tower, a summary and evaluation of sonic boom investigations done in the last decade and a half, and configuration studies to determine practical lower bound sonic boom limits. The BREN tower test program yielded unique and valuable data because it was the first time that vertical profile measurements were made through caustics produced by maneuvers and atmospheric refraction. The objective of the second effort is to compile in a single reference an annotated abstract, including significant results, for each published sonic boom study and to provide a comprehensive review of the current state of the art to aid future researchers. The configuration work is devoted toward determining the feasibility of supersonic transport type airplanes with a primary design goal of acceptable sonic boom characteristics. Each of these investigations is briefly reviewed and significant results are discussed.

Airline Simulation for Analysis of Commercial Airplane Markets

The Lockheed Airline System Simulation is discussed as a step-by-step evaluation of the economics of different ways of routing passenger travel demand. Interacting items that are discussed include forecast passenger traffic demand, persistence of demand, purpose of travel, passenger preferences toward fare and speed, aircraft characteristics, flight frequency, route interaction, and competitive and regulatory influences. Also discussed are specific uses of the simulation program during the design of the supersonic transport. The first use is in determining the optimum SST size, speed, and sonic boom characteristics. The impact of a refined SST on the air transport environment is then discussed. This latter subject is presented in terms of airplane requirements, load factors, airline earnings, and airline return on investment.

Sonic-Boom Pressure-Field Estimation Techniques

Current theoretical methods of estimating the flow field surrounding airplanes in supersonic flight are based on Whitham's solution for the flow about bodies of revolution and on other theoretical work that makes possible the representation of a complete airplane as an equivalent body of revolution. This paper presents a review of the fundamental theory and discusses the use of high-speed digital computers in providing rapid and reliable analysis of sonic-boom characteristics of complex airplane configurations. Application of the estimation techniques is illustrated in correlation with wind-tunnel and flight-test measurements.