Showing papers on "Projectile published in 2005"

Ballistic impact behaviour of woven fabric composites: Parametric studies

Abstract: Polymer matrix composites undergo various loading conditions during their service life. For the effective use of such materials for high performance applications, their behaviour under impact/ballistic impact loading should be clearly understood. This is because the polymer matrix composites are susceptible to impact/ballistic impact loading. Ballistic impact behaviour of composite targets depends upon target geometrical and material parameters as well as projectile parameters. In the present study, investigations on the ballistic impact behaviour of two-dimensional woven fabric E-glass/epoxy composites are presented as a function of projectile and target parameters. The ballistic impact behaviour predictions are based on the analytical method presented in our earlier work [N.K. Naik, P. Shrirao, Composite structures under ballistic impact, Compos. Struct. 66 (2004) 579]. Firstly, perforation and partial penetration of the projectile into the target and cone formation on the exit side of the target are studied. Further, effect of stress wave transmission factor is studied. The other parameters considered are: thickness of the target and mass and diameter of the projectile. Ballistic limit, contact duration at ballistic limit and residual velocity are presented as a function of different target and projectile parameters.

Navier-Stokes Computations for a Spinning Projectile from Subsonic to Supersonic Speeds

Abstract: A computational study has been undertaken to predict the static-aerodynamic, Magnus-moment, and roll-damping coefficients of a standard spinning projectile using a single, modern, unstructured Navier-Stokes flow solver. Numerical results without engraving and semi-empirical results have been obtained for a wide range of Mach numbers to include subsonic, transonic, and supersonic flight regimes. Effects of 0-, 2-, and 5-deg angles of attack have been investigated. Flowfield characteristics of each flight regime are briefly explored. A comparison of coefficients calculated from the computational fluid dynamics results are made to both experimental range data as well as semi-empirical aeroprediction code results with some success. Good predictive capabilities are found for the static aerodynamic coefficients throughout all of the flight regimes. Discrepancies arise between the computational results and the experimental results for the Magnus moment and roll-damping coefficients due in part to the lack of engraving on the computational model.

Modified Projectile Linear Theory for Rapid Trajectory Prediction

Abstract: In some smart weapons, estimation of the impact point of the shell at each computation cycle of the control law is an integral part of the control strategy. In these situations, the impact point predictor is part of the imbedded computing system onboard the projectile. Practical considerations dictate that the impact point predictor yield rapid yet reasonably accurate estimates. Common methods for rapid trajectory prediction are numerical integration of point mass dynamic equations and evaluation of approximate closed-form solutions of the rigid-body projectile dynamic equations. These methods are shown to exhibit poor impact point prediction for long-range shots with high gun elevations characteristic of smart indirect fire munitions. Through modifications of projectile linear theory, a rapid projectile impact point predictor is proposed that eliminates the accuracy problems of the other methods while preserving low computational requirements. Typical results are provided for a short-range trajectory of a direct fire fin-stabilized projectile and a long-range trajectory for an indirect fire spin-stabilized round to substantiate these claims.

Time-Accurate Numerical Prediction of Free-Flight Aerodynamics of a Finned Projectile

Abstract: This article describes a new multidisciplinary computational study undertaken to compute the flight trajectories and simultaneously predict the unsteady free-flight aerodynamics of a finned projectile configuration. Actual flight trajectories are computed using an advanced coupled computational fluid dynamics/rigid body dynamics technique in a body-fixed coordinate system. An advanced time-accurate Navier–Stokes computational technique has been used in computational fluid dynamics to compute the unsteady aerodynamics associated with the free flight of the finned projectile at supersonic speeds. Computed positions and orientations of the projectile have been compared with actual data measured from free-flight tests and are found to be generally in good agreement with the data. Predicted aerodynamics forces and moments also compare well with the forces and moments used in the 6 degree of freedom fits of the results of the same tests. Unsteady numerical results obtained from the coupled method show the flowfield, the aerodynamic coefficients, and the flight paths of the projectile.

Conversion of 92MeV/u 38Ca/37K projectile fragments into thermalized ion beams

Abstract: The results of tests for stopping and extraction of energetic, 92 MeV/ u , short-lived 38Ca and 37K fragments of 0.5% and 0.1% full-width of momentum spread with the first version of the National Superconducting Cyclotron Laboratory (NSCL) gas cell are reported. The projectile fragments were thermalized in 51 cm of helium at 1 bar and were transported by electric fields and gas flow into an expansion chamber through a supersonic nozzle, guided by an radio frequency quadrupole (RFQ) guide and collected on a metallic wire. The extraction efficiency was measured for different implantation rates, different electrical field distributions inside the gas cell, and different values of beam degrader thicknesses. The extraction measurements were compared with the experimental stopping efficiency and measurement of ionization induced in the helium gas. Mechanisms responsible for ion losses were identified and possible improvements of the gas cell performance were discussed.

Optical sighting system

Abstract: An automatic optical sighting system generates at least one adjustment for an adjustable optical system based on at least one detected condition, an appropriate dynamic model of a projectile in flight, and a solution of the equations of motion in flight, so that the projectile will have a trajectory between an origin and a selected target that helps the projectile to hit the target.

Visualization of Impact Damage in Ceramics Using the Edge-On Impact Technique

Abstract: Projectile impact generates severe fragmentation in ceramics which propagates at high velocities and precedes the penetration of the projectile. The high-speed photographic technique of the Edge-On Impact (EOI) has been developed at the Ernst-Mach-Institute (EMI) in order to visualize dynamic fracture in brittle materials. In a typical EOI test the projectile hits one edge of a specimen and fracture propagation is observed during the first 20 us after impact by means of a Cranz-Schardin highspeed camera. EOI tests allow a characterization of different ceramics by the macroscopic fracture patterns, single crack velocities, and crack front velocities (damage velocities). The phenomenology of damage propagation in several ceramics and a ceramic-metal composite is discussed. The EOI technique is useful for the evaluation of damage models for brittle materials because it enables a direct comparison of model predictions to experimental data obtained during the impact process.

Ballistic Impact Behavior of Thick Composites: Analytical Formulation

Abstract: Structures undergo different loading conditions during their service life. Impact is one of the typical cases of loading. In this study, an analytical method is presented for the prediction of ballistic impact behavior of thick composites based on wave theory and energy balance between the projectile and the target. For thick composites the wave propagation along the thickness direction is also considered. During the ballistic impact event, energy transfer takes place from the projectile to the target. As the energy is absorbed by different mechanisms, kinetic energy and velocity of the projectile decrease. Different damage and energy-absorbing mechanisms for a typical woven fabric composite are compression of the target directly below the projectile, possible reverse bulge formation on the front face, compression in the surrounding region of the impacted zone, tension in the yarns, shear plugging, bulge formation on the back face, delamination and matrix cracking, friction between the target and the projectile, and heat generation caused by impact. Based on the analytical method presented, typical results are generated and compared with the experimental values. Nomenclature A = cross-sectional area of the projectile Aql = quasi-lemniscate area reduction factor Ay = cross-sectional area of the yarn d = diameter of the projectile dci = deceleration of the projectile during a given time interval E = energy Ebb = energy absorbed due to bulge formation on the back face of the target Ecf = energy absorbed due to compression of the target directly below the projectile Ecsy = energy absorbed due to compression of yarns in the surrounding region of the impacted zone: region 2 Edl = energy absorbed due to delamination Efr = energy absorbed due to friction Ehg = energy absorbed due to heat generated Emc = energy absorbed due to matrix cracking Emt = energy absorbed by matrix cracking per unit volume Erb = energy absorbed due to reverse bulge formation on the front face of the target Esp = energy absorbed due to shear plugging of the yarns Etf = energy absorbed due to tension in the yarns in a layer ETOTAL = total kinetic energy lost by the projectile F = total force/contact force Fc = compressive force Fi = inertial force GIIcd = critical strain energy release rate in mode II h = thickness of the target hl = thickness of each layer hlc = thickness of a layer after compression h p = length of the plug K = numerical constant (depends on the shape of the projectile)

Projectile-Residual-Target-Ion Scattering after Single Ionization of Helium by Slow Proton Impact

Abstract: 0031-9007= We have measured fully differential single ionization cross sections for 75 keV p He collisions. At this relatively small projectile velocity, signatures of the projectile–residual-target-ion interaction, which are not observable for fast projectiles and for electron impact, are revealed rather sensitively. In fact, this interaction appears to be more important than the postcollision interaction, which so far was assumed to be the most important factor in higher-order effects for slow ion impact. These features are not well reproduced by our three-distorted-wave calculations.

Temporal cavity and pressure distribution in a brain simulant following ballistic penetration.

Abstract: To study ballistic brain injury biomechanics, two common civilian full metal jacket handgun projectiles (25-caliber and 9-mm) were discharged into a transparent brain simulant (Sylgard gel). Five pressure transducers were placed at the entry (two), exit (two) and center (one) of the simulant. High-speed digital video photography (20,000 frames/second) was used to capture the temporal cavity pulsation. Pressure histories and high-speed video images were synchronized with a common trigger. Pressure data were sampled at 308 kHz. The 25-caliber projectile had an entry velocity of 238 m/s and exit velocity of 170 m/s. The 9-mm projectile had an entry velocity of 379 m/s and exit velocity of 259 m/s. Kinetic energies lost during penetration were 45.2 J for the 25-caliber projectile and 283.7 J for the 9-mm. Size of temporary cavities and pressures were dependent on projectile size and velocity. The 9-mm projectile created temporary cavities 1.5 times larger in size and lasted 1.5 times longer than the 25-calibe...

Dynamics of a projectile penetrating in granular systems.

Abstract: The impact of a sphere with velocity u0 on a fine, loose granular system under the acceleration due to gravity has been studied by fast video photography. The behavior of the granular bed is found to be similar to a fluid during initial impact, followed by a cavity drag during projectile penetration. From the trajectory of the projectile it is found that the drag on the projectile can be well described by adding a bulk frictional force f to the hydrostatic force kappa(z) where kappa is a constant and z denotes the penetration depth. Both kappa and f are u0 dependent. This form of the drag force suggests that fluidlike viscous dissipations in the bed can be neglected in these three-dimensional (3D) experiments. However, due to the imposed boundary this hydrodynamic term of the drag force is found to be not negligible in quasi-2D granular beds.

Model Predictive Control of a Direct Fire Projectile Equipped With Canards

Abstract: Launch uncertainties in uncontrolled direct fire projectiles can lead to significant impact point dispersion, even at relatively short range. A model predictive control scheme for direct fire projectiles is investigated to reduce impact point dispersion. The control law depends on projectile linear theory to create an approximate linear model of the projectile and quickly predict states into the future. Control inputs are based on minimization of the error between predicted projectile states and a desired trajectory leading to the target. Through simulation, the control law is shown to work well in reducing projectile impact point dispersion. Parametric trade studies on an example projectile configuration are reported that detail the effect of prediction horizon length, gain settings, model update interval, and model step size.

Interface Defeat of Long-Rod Projectiles by Ceramic Armor

Abstract: : An investigation has been conducted to guide the development of ceramic armor that protects against long-rod projectiles launched at ballistic-ordnance velocities. Studies have concentrated on protection by diverting the projectile, but have also considered protection by maintaining a high resistance to penetration. A projectile is diverted by promoting a lateral flow of projectile erosion products at the ceramic, which minimizes stress and microdamage in the impinged area of the ceramic. Some resistance to lateral flow provides dynamic frontal support for the ceramic, and the projectile is fully consumed by lateral flow even though marginal rear support permits moderate macrodamage. The first part of the investigation has examined ceramic damage and the influences of materials, dimensions, target designs, and other factors, such as impact velocity and target obliquity. The second part of the investigation has briefly considered layered target designs that achieve protection by maintaining the ceramic element s high resistance to penetration. The interplay of material properties and characteristics and target designs must be further investigated to determine the potential for future ballistic armor designs.

Kinetic energy rod warhead with lower deployment angles

Abstract: A kinetic energy rod warhead includes a projectile core which includes a plurality of individual projectiles, an explosive charge about the core, at least one detonator for the explosive charge, and an explosive sheet on each end of the projectile core.

Pseudo GPS aided multiple projectile bistatic guidance

Abstract: A guidance system for guiding each of several projectiles toward a moving target has a platform having a radar system for illuminating the target with a radar signal. Each projectile has a receiver for receiving the radar signal reflected from the target, a transponder for replying to Global Positioning System (GPS) like timing signals from several timing signal sources, and a data link transceiver for establishing a bidirectional data link to the platform. The data link carries the measured frequency shift of the radar signal reflected from the target as measured by the projectile. A computer on the platform computes a relative position of each projectile with respect to the target from tracking the moving target using the radar system and the reply signal from the transponder on each projectile. The data link sends guidance commands from the platform to each projectile to guide the projectile to the target.

2-d projectile trajectory correction system and method

Abstract: A 2-D correction system uses intermittent deployment of aerodynamic surfaces (18) to control a spin or fin stabilized projectile (10) in flight; correcting both crossrange and downrange impact errors. Intermittent surface deployment develops rotational moments, which create body lift that nudge the projectile (10) in two-dimensions to correct the projectile (10) in its ballistic trajectory. In low spin rate projectiles ('fin stabilized'), the rotational moment directly produces the body lift that moves the projectile (10). In high spin rate projectiles ('spin stabilized'), the rotational moment creates a much larger orthogonal precession that in turn produces the body lift that moves the projectile (10). The aerodynamic surfaces are suitably deployed over multiple partial roll cycles at precise on (deployed) and off (stowed) positions in the cycle to nudge the projectile (10) up or down range or left or right cross range until the desired ballistic trajectory is restored.

Method and an apparatus for determining a deviation between an actual direction of a launched projectile and a predetermined direction

Abstract: A method of determining a deviation of a path of a projectile from a predetermined path. The method uses an image of a target area in which the desired path or direction is pointed out. Subsequently, the real direction or path is determined and the deviation determined.

Exact expressions for the range and the optimal angle of a projectile with linear drag

Abstract: The analytical expressions for the range and the optimal angle of a projectile with linear drag are obtained for the first time. The analytical results are expressed in terms of the Lambert W funct...

Charge state and stopping dynamics of fast heavy ions in dense matter

Abstract: K-shell radiation of fast heavy ions penetrating solid matter was used to analyze the stopping dynamics of ions over more than 80% of the stopping path. The most important advantage of this method is that the data is obtained with a high spatial resolution directly from the interaction volume. In experiments 11.4 MeV/ u Ca projectile were slowed down in solid quartz and low-density SiO2 aerogel targets. Characteristic projectile and target spectra in the photon energy range of 1.5–4 keV were registered by means of spherically bent crystal spectrometers with high spectral and spatial resolution in the direction of the ion beam propagation. K-shell spectra of heavy ions induced by close collisions with target atoms provided information about the projectile charge state and velocity dynamics. The line intensity distribution of the K-shell transitions arising from ions with different ion charges represents the charge state distribution along the ion beam track. The variation of the line Doppler shift due to the ion deceleration in the target material was used to determine the ion velocity dynamics. The spectroscopic analysis of the stopping process was complemented by measurements of the energy loss and ion charge state distribution after the ion beam emerged from the target using a standard time-of-flight method and magnet spectrometer.

Frictional roll control apparatus for a spinning projectile

Abstract: The invention relates generally to a roll damping apparatus for a spinning projectile having a first section and a second section rotatably attached about a roll axis. The roll damping apparatus comprises a first portion attached to the front section, and a second portion attached to the rear section. The first portion is adapted to cause a braking frictional force to act on the second portion, the braking force being effective to control the spin rate of the front section relative to the rear section. The invention further relates to a spinning projectile having a roll damping apparatus.

Model Predictive Control of a Direct Fire Projectile Equipped with Canards

Abstract: Launch uncertainties in uncontrolled direct fire projectiles can lead to significant impact point dispersion, even at relatively short range. A model predictive control scheme for direct fire projectiles is investigated to reduce impact point dispersion. The control law depends on projectile linear theory to create an approximate linear model of the projectile and quickly predict states into the future. Control inputs are based on minimization of the error between predicted projectile states and a desired trajectory leading to the target. Through simulation, the control law is shown to work well in reducing projectile impact point dispersion. Parametric trade studies on an example projectile configuration are reported that detail the effect of prediction horizon length, gain settings, model update interval, and model step size.