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This paper presents the results of the theoretical external ballistic calculations for projectiles fired from barrels which correspond to the barrels used in two Polish small arms systems: MSBS- 5.56 system (MSBS GROT standard rifle and MSBS GROT carbine) and BERYL system (BERYL standard rifle and MINI BERYL carbine). The results obtained allowed the analyse of the effects of barrel length and the associated initial projectile velocity on the nature of projectile trajectory, particularly the over height and projectile range obtained along the trajectories. The analysis of the results facilitated an assessment of the scope of proposed changes in the settings of the firearm sights, resulting from the use of barrels of different lengths and the consequential changes in projectile trajectory.

This is a study to investigate ballistics performance of armor structures with in-layer deflector against projectiles. For this purpose, the armor structure, which consists of a v-cross section sheet metal array covered with aluminum and steel plates, has been designed and optimized. Firstly, numerical simulations were studied using the finite-element method (FEM). The ANSYS LS-DYNA FE software is used for the ballistic analysis. The Johnson-Cook constitutive equation and damage model were used to model the behavior of metal armors under impact in the ballistic simulations. In the next step, experimental studies were carried out. Penetration depths were measured; including the magnitude of plate bending in front of the target plate and bulging behind it. Comparisons between the results of the finite element analysis (FEA) and the tests reveal that a bullet with a velocity of 868 m/s penetrated the target, but the target could not be penetrated at a firing speed of 631 m/s Furthermore the experimental and numerical results were in good agreement. © 2022, Marcílio Alves. All rights reserved. 2021-01-05-035 This project was supported by the Research Fund of the Sakarya University of Applied Sciences (Project Number: 2021-01-05-035). We thank the Sakarya University of Applied Sciences for its financial support.

The main goal of the study is to analyze methods and diagnose mechanical damage to the pipeline using functional analysis, neural networks and the finite element method. In the work, mathematical formulations of the corresponding geometrical inverse problems of the theory of shells on reconstruction of defects of lateral surface are formulated according to measurement data obtained from sensors located in a given section of the shell. The statement was given and a method for solving inverse geometric problems for a shell of Tymoshenko type was developed. The authors have offered methods for solving inverse geometric problems of identifying volumetric and crack-like defects in extended underground structures and pipelines based on the analysis of responses to unsteady elastic-wave perturbations using the mathematical apparatus of wavelet signal transformation, the finite element modeling method and intelligent software system based on neural network.

The article is devoted to the study of the optimal control of propellant consumption during vertical lifting of rocket in homogeneous atmosphere using regularized solution of integral equation of the first kind. The problem of lifting of a rocket into desired height along optimal trajectory in the view of minimal consumption of propellant leads to solving the set of differential and integral equations. Problem of optimal control of propellant consumption during lifting of rocket in homogeneous atmosphere is solved using regularized solution of integral equation of the first kind which is solution of corresponding Euler equation on discrete time net. Influence of the regularization parameter and some additional parameters on precision of discreted problem is investigated. Considered algorithm is summed up easily to the case of non-homogeneous atmosphere by introducing dependence of the ballistic coefficient on altitude of flight and to problem of putting spacecraft into determined orbit and suborbital flights by setting desired altitude and velocity and modifying of motion equations.

This work presents a novel approach for the modeling of the entrainment in the numerical simulation of the internal ballistics of hybrid rocket engines with paraffin-based fuels. This model, coupled with a more sophisticated gas–surface interaction treatment, is an improvement of the model previously developed by some of the authors, which was based on some oversimplifying assumptions. Indeed, the old entrainment model was performed in a close range of averaged oxidizer mass flux, and it made the overall numerical model not scalable on different motor sizes. Therefore, a new correlation is introduced, which is based on the Reynolds number and takes into account the dependence of the entrained fraction on the shear stress exerted by the gas flow and the tube diameter. Firstly, the new and the old numerical models are compared in order to highlight the improvement obtained by the current efforts. Then, the model has been validated on experimental tests involving two different thrust class motors. Finally, the effect of the motor size on the fuel consumption is shown, thus revealing the crucial influence of the recirculating zone extension due to the oxidizer axial injection.

This article is concerned with the issue related to studying the dynamic properties of the aerial target imitator. Applying the modelling principles, the structure and technical data of aerial target imitator were described and utilising the PRODAS software a physical model of the aerial imitator was developed based on the conducted simulation studies. Mass, aerodynamic and basic parameters of flight path were determined. Then, experimental studies of basic dynamic characteristics were discussed. The comparison of results obtained from experimental and theoretical studies proves the correctness of the developed model.

A predictive numerical approach, based on Reynolds-averaged Navier–Stokes simulations including the effects of turbulence, chemistry, fluid/surface interaction, and radiation, has been developed fo...

A computational thermofluid-dynamic model of hybrid rocket internal ballistics is developed. Numerical simulations of the flowfield in a laboratory small-scale hybrid rocket motor, operated with gaseous oxygen and high-density polyethylene propellants, are carried out with the aim of predicting the solid fuel regression rate experimentally achieved with two different oxidizer injectors. The fuel regression rate is the main parameter for the hybrid rocket design. Here, it is calculated with a detailed gas/surface interface characterization based on local mass and energy balances. The combustion of oxygen and gaseous ethylene injected from the fuel wall is modeled by means of the probability-density-function approach coupled to chemical equilibrium. Two oxidizer-injection configurations, which generate either a two-dimensional axially symmetric or three-dimensional flowfield, are analyzed. The local regression rate is evaluated along both the fuel grain axis and inner circumference in the three-dimensional case, as well as at several stages in the firing, by updating the local port diameter, which is thus not assumed constant. Data retrieved from three firing tests are compared with the numerical results, revealing good agreement between both the average regression rates (maximum deviation less than 5%) and the fuel consumption axial profiles (with maximum deviation of 14%)

Based on the theory of fractional order calculus (FOC), a novel extended proportional guidance (EPN) law for intercepting the maneuvering target is proposed. In the first part, considering the memory function and filter characteristic of FOC, the novel extended PN guidance algorithm is developed based on the conventional PN after introducing the properties and operation rules of FOC. Further, with the help of FOC theory, the average load and ballistics characteristics of proposed guidance law are analyzed. Then, using the small offset kinematic model, the robustness of the new guidance law against autopilot parameters is studied theoretically by analyzing the sensitivity of the closed loop guidance system. At last, representative numerical results show that the designed guidance law obtains a better performance than the traditional PN for maneuvering target.

A numerical rebuilding of a series of test data obtained with static firings of a lab-scale hybrid rocket is carried out with a Reynolds-averaged Navier–Stokes solver including detailed gas–surface interaction modeling based on surface mass and energy balances. Two experimental campaigns are considered in which gaseous oxygen is fed into axisymmetric hydroxyl-terminated polybutadiene grains through an axial conical subsonic nozzle. A validation rebuilding of all of the firing tests has been performed first to highlight numerical prediction capabilities and modeling limits. Despite the several geometrical simplifications, which allows using a reduced number of cells in the computational domain and thus performing parametric analyses efficiently, the present computational fluid dynamics approach is able to capture the main features of the motor internal ballistics, fairly reproducing the average chamber pressure values and the fuel regression rate trends with oxidizer mass flux and port diameter. Computed f...

The handling of explosives and ammunition introduces a safety risk for personnel and third parties. Accidents related to storage, transport and transshipment may result in severe injury and material damage. Dispersion of structural debris is one of the main hazards resulting from detonations inside structures. Reliable prediction models for debris dispersion are essential for risk assessment methods. In this article we give a statistical description of the dispersion of explosion produced debris. The basis is a general expression for the projectile areal number density in the horizontal and vertical plane. Combined with engineering models for the launch conditions, predictions can be made. An analytical solution to the equations of motion may be used to allow for fast calculations. A parameter study shows consistent results. The model has been validated with internal detonation tests of bare charges in reinforced concrete structures. The validation clearly shows the prediction capabilities of the model for three loading regimes described in the literature. We give a thorough description of the validity and limitations of the model, and an outlook of current and future research. Examples are the failing debris mass distribution prediction for reinforced concrete in the shock overloading regime, and ricochet and roll and break-up at impact phenomena.

Current Mars entry, descent, and landing technology is near its performance limit and is unable to land payloads on the surface that exceed approximately 1 metric ton. One option for increasing landed payload mass capability is decreasing the entry vehicle's hypersonic ballistic coefficient. A lower ballistic coefficient vehicle decelerates higher in the atmosphere, providing additional timeline and altitude margin necessary for heavier payloads. This study analyzed the guided entry performance of concept low ballistic coefficient vehicles at Mars. A terminal point controller guidance algorithm was used to provide precision targeting capability. Accuracy at parachute deploy, peak deceleration, peak heat rate, and integrated heat load were assessed and compared to a traditional vehicle to determine the effects of lowering the vehicle ballistic coefficient on entry performance. Results from this study suggest that while accuracy at parachute deploy degrades with decreasing ballistic coefficient, accuracy and other performance metrics remain within reasonable bounds for ballistic coefficients as low as 1 kg/m2. As such, this investigation demonstrates that from a performance standpoint, guided entry vehicles with large diameters may be feasible at Mars.

Measuring an arrow's ballistic performance such as arrow velocity on impact, total time of flight and arrow shaft oscillation is challenging because of the dynamic nature of arrow flight. This challenge becomes increasingly difficult as the distance of the shot increases. It is also of great interest to bowhunters to understand the ballistic performance of arrows that include hunting broadheads. A miniaturized, sensory data acquisition system, located in the arrow tip and engineered to withstand the high accelerations experienced at launch and impact, enables the precise measurement of arrow ballistics in flight. By continuously recording arrow drag in flight, the system enables measurement of the ballistic performance of an arrow as it travels downrange. The authors have also built an adapter that is connected to the housing of the sensing system to allow for comparative ballistic tests to be performed on hunting broadheads. Here, we present results obtained using the sensing system to perform initial testing on two commercially available broadheads at shot distances of approximately 45 m.

Este documento expone la metodología y los resultados obtenidos en el desarrollo de una investigación sistemática, que trata sobre a la implementación de misiones de cohetería experimental. En este proceso se obtuvieron, datos y resultados que permitieron corroborar de forma experimental, conceptos de propulsión, aerodinámica y balística propios de una aeronave tipo cohete sin elementos de control activo a bordo. Para el estudio e implementación de esta misión, se generó un método dividido en etapas por las cuales se guió el desarrollo del proyecto; primero se realizó la etapa de validación y eldiseño preliminar en forma teórica, se continuó con la etapa de simulación, utilizando un software especializado y culminó con la etapa del proceso constructivo y el procedimiento de disparo. La puesta en marcha de esta misión de cohetería experimental permitió alcanzar, propulsado por un combustible tipo “candy” compuesto por nitrato de potasio y sorbitol, un apogeo del cohete Ainkaa 1 de 780 m sobre la superficie de lanzamiento, con una velocidad de impacto de 526 Km/h, un tiempo de quemado de 3.2s entre otros datos, para configurar esta misión dentro de la categoría de alta potencia.

The problem of evaluating the performance of an uncertain guidance loop system is considered, when the uncertainty is described in terms of an integral quadratic constraint. The idea of the approach proposed in this paper is to determine the set of all possible state vector values at the end of the flight that are compatible with the model uncertainty and determine the upper and lower bound for the miss distance by solving two optimization problems on this set. The main theoretical result of the paper shows that this is a quadric that can be determined by the solving a differential Riccati equation and a set of coupled linear differential equations. Unfortunately, numerical experiments showed that the method is practically unusable for realistic models of guidance loops. A single integral quadratic constraint is a poor representation of the usual model uncertainties, meaning that the results are certainly too conservative. In addition, the optimization problem turns out to be badly conditioned in all cases of interest for homing guidance loop analysis. This is illustrated using a contrived numerical example based on a relatively well-behaved linear time-invariant system. Although in its present form, the approach taken in this paper did not achieve the results that were hoped for, the ideas advanced here, and some of the technical results are interesting in themselves and may be useful in future research on this theme.

The problem of evaluating the performance of an uncertain guidance loop system is considered, when the uncertainty is described in terms of an integral quadratic constraint. The idea of the approach proposed in this paper is to determine the set of all possible state vector values at the end of the flight that are compatible with the model uncertainty and determine the upper and lower bound for the miss distance by solving two optimization problems on this set. The main theoretical result of the paper shows that this is a quadric that can be determined by the solving a differential Riccati equation and a set of coupled linear differential equations. Unfortunately, numerical experiments showed that the method is practically unusable for realistic models of guidance loops. A single integral quadratic constraint is a poor representation of the usual model uncertainties, meaning that the results are certainly too conservative. In addition, the optimization problem turns out to be badly conditioned in all cases of interest for homing guidance loop analysis. This is illustrated using a contrived numerical example based on a relatively well-behaved linear time-invariant system. Although in its present form, the approach taken in this paper did not achieve the results that were hoped for, the ideas advanced here, and some of the technical results are interesting in themselves and may be useful in future research on this theme.

Commercial pressure on users and suppliers of space systems is forcing industry to reduce operational time and costs on ground and to increase reliability of operations in orbit. One opportunity has been identified in the use of non-toxic alternatives to established state-of the art propellants for spacecraft and orbital vehicles. Due to the considerable variety of propellant candidates existing or being developed around the globe the need for a systematic selection method and for selection criteria is identified and is presented in this paper. This method permits down selection of the most promising propellants for the benefit of users and propulsion system developers alike. It is shown in two sample cases that the selection method applied to each mission objective and to the resulting technical requirements leads to a quantified ranking among the potential candidates. Each mission may entail its own specific propellant. Also, the time scale for reaching operative readiness of a non-toxic propulsion system and possible multiple use in the same spacecraft strongly influences the propellant choice. Although an ideal non-toxic propellant for a generic use on spacecraft and orbital propulsion is not identified, for each individual mission and program time frame the suitable propellant can be chosen by the methods proposed in this paper.

The parallel, Double Wall, hypervelocity impact shield configuration has been heavily tested and characterized for ballistic performance for normal and oblique impacts for the ISS and other programs. However, in many locations with spacecraft designs, the rear wall cannot be modeled as being parallel or concentric with the outer bumper wall and in cases with a cylindrical outer wall, the effective non-parallel angle commonly varies as the outer wall impact location changes. This complicates micrometeoroid and orbital debris assessment of critical spacecraft components located within outer spacecraft walls. Based on a study combining hypervelocity impact testing and hydrodynamic impact simulations on multiple shield configurations including non-parallel first and rear walls, this paper provides equation adjustments for use with the double wall Ballistic Limit Equation (BLE) for a variety of impact speeds, non-parallel wall angles and impact obliquities.

A series of hybrid sandwich structures were fabricated by shrink-fitting precision-ground prisms of alumina (CoorsTek grade AD 995) with triangular, trapezoidal or rectangular cross-sections into the voids of extruded sandwich panels made from Al 6061-T6. The panels were subjected to impact tests using hard steel spheres over the velocity range 570–1800 m s −1 . A combination of X-ray tomography, high-speed video imaging and cross sectioning of impacted samples was used to investigate the penetration mechanisms. We find that the ballistic performance of these structures, characterized by the ballistic limit and the exit velocity of impact ejecta beyond this limit, is significantly improved when triangular prisms are replaced by trapezoidal prisms, provided the base width of the prism exceeds about three times the projectile diameter. Additional performance improvements are obtained when the trapezoidal prisms are replaced by rectangular prisms, albeit at the expense of an increase in the lateral extent of damage. The variations in impact response are found to arise from: (i) the effect of prism size and shape on the degree of confinement of the ceramic by the metallic webs, (ii) the core web structure, which influences the fracture conoid angle in the transverse plane, and (iii) the spacing of web-face nodes on the back face, which governs the deflection and fracture of the back-face sheet.