Muzzle Wave Research Articles

The effect of muzzle devices on the distribution of muzzle waves when firing an assault rifle

The effect of muzzle devices on the distribution of muzzle waves when firing an assault rifle

METHOD OF DETERMINING THREE ACOUSTIC SENSORS FOR REGISTRATION THE BALLISTIC WAVE OF AN ARTILLERY SHOT

Abstract. The paper is dedicated to the development of the method of identifying acoustic sensors for registering ballistic and muzzle waves of an artillery shot. The proposed method allows solving the problem of selecting three acoustic meters from the existing set in the firing zone, which are the most suitable for implementing effective registration of ballistic and muzzle waves of a shot, taking into account their location, measurement error, and the probability of failure-free operation. Keywords: artillery shooting, verification of shots, ballistic wave, method of identifying acoustic sensors

Development of a universal binary classifier of the state of artillery barrels by the physical fields of shots

An artillery shot is accompanied by the release of combustion products of powder gases from the barrel. It is proposed to usemuzzle ejection to classify the level of barrel wear during firing. A full-scale experiment was carried out with high-speed video recording in the visible and infrared ranges of the dynamics of the development of muzzle ejection when firing guns with a defect-free and worn barrel. Muzzle ejection when fired from a large-caliber gun consists of three spatial regions: frontal and two side, associated with the emission of powder gases through the openings of the compensators. A technique for analyzing three synchronized video streams has been developed. The technique made it possible to quite fully investigate the processes of muzzle ejectiondevelopment dynamics in defect-free and worn barrels. Informative signs are chosen, which are different for the dynamics of muzzle ejection from defect-free and worn barrels. This madeit possible to build a binary classifier of the condition of the trunks by the level of wear based on the support vector machine with least squares. In contrast to the classical SVM classifier, thisallowed us to reduce the calculation time and reduce the required size of the training set. To assess the quality of classification, it is proposed to rely on only errors of the first and second kind, but also an integral indicator –the probability of error-free classification. To increase the reliability of the classification, the concept of a universal binary classifier is proposed, which uses both video recording of the muzzle ejection and acoustic fields of the shot –ballistic and muzzle waves –to diagnose the state of the barrel. On the basis of experimental data, it is shown that the use of all physical fields accompanying an artillery shot for the binary SVM classification allows obtaining a high value of the error-free classification probability.

INFORMATION TECHNOLOGY FOR AUTOMATED ASSESSMENT OF THE ARTILLERY BARRELS WEAR BASED ON SVM CLASSIFIER

An information technology for the automated assessment of the has been developed wear level has been developed. Information technology is based on the analysis of acoustic fields accompanying a shot. The acoustic field of the shot consists of a ballistic wave accompanying a projectile flying out at a supersonic speed, and a muzzle wave generated when propellant gases are ejected from the barrel. The parameters of the ballistic and muzzle waves depend significantly on the level of barrel wear. This makes it possible to construct an automatic classifier of the barrel wear level based on the analysis of informative features of acoustic signals recorded by microphones near the weapon's firing position. The information technology is based on a binary SVM classifier. A set of records of acoustic fields of shots was synthesized on the basis of real signals recorded when firing a 155 mm howitzer. From the set of records, a training and test set of information features were formed for training the classifier and assessing its quality. Methods of preliminary data normalization of training and test samples are investigated. A technique for optimizing the classifier hyperparameters with instance cross-validation has been developed. The technique is a two-stage method for finding the optimal values of hyperparameters. In the first stage, the search is performed on an exponential decimal grid. At the second stage, the optimal values of hyperparameters are refined on a linear grid. A method for the binary classification of artillery barrels according to the wear level has been formulated. Checking the classifier on a consistent test sample showed that it provides the correct classification of barrel wear with a probability of 0.94. An information technology has been developed for classifying artillery barrels by wear level based on the analysis of acoustic fields of shots. Information technology consists of three stages: data preparation, construction, training an optimization of the binary SVM classifier and the operation of the binary SVM classifier. A field experiment was carried out, which confirmed the correctness of the basic scientific and technical solutions. An automated system has been developed for classifying wellbores by wear level.

Development of physical models for the formation of acoustic waves at artillery shots and study of the possibility of separate registration of waves of various types

Physical models of the formation of ballistic and muzzle waves generated during an artillery shot have been developed and investigated. A promising method for assessing the degree of wear of artillery barrels is the acoustic non-contact method. However, its implementation requires separate records of the ballistic and muzzle waves. A series of physical models have been developed to assess the possibility of such a recording. A model for calculating parameters of a ballistic wave accompanying an artillery shot has been built. The proposed model features replacement of the problem of spatial axisymmetric streamlining the shell surface by the problem of plane streamlining the wedge. The model makes it possible to determine the value of the angle of inclination of the oblique shock to the direction of the oncoming flow depending on the Mach number. Calculation of pressure of the powder gases flowing from the muzzle section of the barrel behind the shell is based on the application of the law of energy conservation for compressed powder gases. This avoids solving the complex modified Lagrange problem. Calculations show that the muzzle wave pressure changes in the range (30...300) MPa. A physical model of the muzzle wave propagation at the initial stage of the outflow of powder gases from the bore was proposed. During propagation of the muzzle wave, a situation is possible at an initial stage in which this wave reaches the recording point before the ballistic wave. This situation can occur if the range angles and the wedge taper are small. This phenomenon can be avoided by appropriate angle selection. The proposed model determines the law of propagation of the muzzle wave and makes it possible to estimate the rate of its attenuation. It has been established that measuring microphones recording the actual ballistic wave can be located at distances of 50÷500 m from the barrel. The developed models are useful in practice. It is possible to estimate the initial speed of the shell and the degree of barrel wear by separate recording the ballistic and muzzle waves

Development of a method for determining the wear of artillery barrels by acoustic fields of shots

A possibility of assessing the level of wear of artillery barrels by acoustic fields of shots was studied. Despite the importance of knowledge on the current barrel state, existing methods of wear assessment are not sufficiently prompt. These methods give rather rough estimates of wear or require expensive equipment. Unlike the known methods, the method proposed in the article is prompt, does not require large expenses, can be combined with a training firing, and is easily automated. Characteristics of the shock and muzzle waves generated by a gunshot were studied and differences in their parameters for barrels without wear and those with a critical wear level were shown. Initial shell velocity serves as a criterion indicator of wear. It was shown that according to the acoustic characteristics, a shot from the barrel having any degree of wear is equivalent to a shot from a gun of a smaller caliber. A computational experiment was conducted on real acoustic signals recorded during the firing of a 155 mm howitzer. Informative attributes of acoustic signals from shots were selected. They make it possible to automatically classify barrels into two classes: barrels suitable for use and barrels with wear exceeding the critical level. It was shown that the application of the support vector method (SVM) makes it possible to confidently classify barrels by the level of their wear based on the temporal and spectral attributes of the shock and muzzle waves. A cumulative analysis of spectral characteristics was used in the analysis of acoustic signals from shots. This has a significantly increased likelihood of correct barrel classification. The results are useful for practical use in artillery units in the field conditions. The study results enable the development of an automated system for assessing the barrel condition with high promptness. This ensures sufficient accuracy in assessing the level of barrel wear in the combat practice

Integrating acoustic shooter detection into a hearing protection device

Recent advances in the development of hearing protection devices open new fields of applications on the battlefield. While the TCAPS (Tactical Communication And Protective Systems) protect against acute acoustic traumas, they maintain information relative to the acoustic environment of the soldiers. Today, these systems are efficient for both hearing protection and communication. We propose to use the microphones equipping the TCAPS headsets in order to detect and localize shooters on the battlefield. The microphone underneath the hearing protection is used in order to detect the shock and muzzle waves generated by supersonic shots. A meshed network between the TCAPS deployed on the field allows transmitting asynchronous information relative to the detected waves to data fusion nodes that allow estimating the shooter’s position. Solutions are proposed in order to compensate the effects of the presence of the head between the microphones underneath the hearing protection. Results concerning the estimation of the time difference of arrival of a transient wave in free field and in the presence of an artificial head are presented. The data fusion process is tested thanks to simulations in various deployment configurations.

Analysis of Solutions of Intermediate Ballistics Problems

В статье автор анализирует состояние проблем расчета процессов, имеющих место в период последействия, и определения эффективности устройств, работающих в этот период. Рассматриваются методики расчета, построенные на аналитических зависимостях, и численные методики; указываются особенности, которые требуется учитывать при использовании решений в квазистационарной или в нестационарной постановке. В статье подчеркивается необходимость учитывать при расчете параметров течения наличие фазы установления, в продолжение которой наблюдается движение в газоводе ударных волн и волн разряжения, а также изменение под действием термодинамических и волновых процессов положения критических сечений течения потока, образование циркуляционных и застойных зон, других нестационарных газодинамических явлений. Указанные процессы играют существенную роль при образовании дульных ударных волн и пламенности выстрела, что во многом определяет качество наствольных устройств ствольного оружия.

DETERMINING OF SOURCE’S COORDINATES OF SHOT BY MEAN OF ACOUSTIC WAVES

The article discusses the localization of the source of the shot by two microphones using the parameters of the excited acoustic wave. The direction of angle on the source is determined by the difference in arrival of the acoustical muzzle wave on microphones, and the distance – the algorithm which takes into account both the time and the physical characteristics of the acoustic wave. The theoretical calculations and experimental data of determining the source of origin.Referense 3, Figures 3

Sensitivity of shot detection and localization to environmental propagation

Acoustic sensing systems are used to detect and localize mortar and small arm shots on the battlefield. This study is an experimental investigation on the sensitivity of the sensing performance to environmental propagation. For simulated mortar shots, the muzzle wave detection range is observed to vary by a factor of three from day to day and with the propagation direction, due to the varying atmospheric refraction. For small-arm fire shots, the shot azimuth is estimated by some degrees in an open environment, but large errors are observed for shots nearby a forest (with Mach wave reflections) in adverse atmospheric conditions. Last, the shooter’s range estimate is found to feature bias and scatter. Atmospheric turbulence is found to cause the observed shot-to-shot variability of the Mach wave characteristics, which drives the scatter in range estimate. The study promotes a careful assessment of impulse sound propagation effects when analyzing, developing, evaluating and using systems for shot detection and localization.

Generalization of the muzzle wave similarity rules

The present paper describes an improvement of the muzzle wave similarity that permits treatment to unsteady and non sonic gun muzzle conditions. The revised formulation of the similarity is capable of characterizing the muzzle wave propagation even for significant variation of the muzzle conditions during the life time of the wave. Suitable scaling parameters are selected and tested yielding appropriate similarity rules at a significantly reduced number of tests whose applicability is confirmed by experimental data and comparison to an analytical theory.

Similarity and asymptotic analysis for gun-firing aerodynamics

An experimental observation of the flow following the discharge of firearms has been carried out by means of ultra-high-speed visualization. The theory of similarity has been applied in order to define the rules governing the tests on models, chiefly for gun firing-air intake interference problems. When the blast effect predominates, no geometric similarity is required between the simulation gun and the simulated one, so the model and the simulation gun can have different scales. It is shown that the main parameter characterizing the blast effect is the energy rate at the muzzle which can be considered as a point source of energy caused by a very hot gas. So, the muzzle wave tends asymptotically toward the blast wave of a non-instantaneous intense point explosion. Specific experiments confirm this assertion. All previous results allow a theoretical modelling of gun-firing aerodynamic phenomena which will be presented in a separate paper.