Projectile Speed Research Articles

Interference effects due to projectile target nucleus scattering in single ionization ofH2by75−keVproton impact

Doubly differential cross sections (DDCSs) for single ionization of molecular hydrogen by $75\text{\ensuremath{-}}\mathrm{keV}$ proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. Interference structures are observed in the scattering angular dependence of the DDCSs, which disappear, however, at electron speeds near the projectile speed. The comparison to our calculations shows that the projectile-target nucleus interaction plays a central role. Furthermore, our data suggest that for a given scattering angle, ionization favors well-defined molecular orientations.

A special design condition to increase the performance of two-stage light-gas guns

Abstract This paper reports a theoretical and numerical study aimed at increasing the operating efficiency of two-stage light-gas guns by appropriately changing their working conditions. In particular, a method is presented for increasing the projectile speed without any rise of the maximum breech pressure. The classic design theory of two-stage guns starts from the assumption that the highest velocity is reached in a gun which constantly maintains the maximum acceptable pressure at the base of the projectile during the full launching time. The main drawback of this working condition is that it may require an unfeasible rise of the gun maximum pressure, especially when very high muzzle speed is requested. To overcome this limitation, a new reference case different from the constant-base-pressure one is presented, based on a novel gas-dynamics solution that can be expressed in exact form if losses are not accounted for. According to such an approach, it is theoretically shown that the projectile base-pressure can be appropriately shaped (i) to improve the final speed without increasing the breech pressure or, in other terms, (ii) to achieve a given muzzle velocity with reduced maximum gas pressure. The analytical application of the new gas-dynamics condition showed the capability of obtaining a 1 km/s velocity improvement with no increase of the breech pressure or, alternatively, a pressure reduction up to 30% with no penalty on the model final speed. A numerical verification of the calculations was performed through the CISAS light-gas gun full numerical model, which includes real effects such as friction losses and heat transfer. Finally, an experimental verification of the numerical test case was attempted and a speed augmentation of 0.8 km/s with no increase in the breech pressure was confirmed in laboratory, highlighting the agreement with numerical predictions.

Investigation of Liquid Impact-Based Macro-, Meso-, and Microforming Processes

It was shown that the liquid impact at the projectile speed of 1500 m/s affects a target similarly to an explosive deposited on the workpiece surface. A setup to investigate material deformation using the liquid impact was designed and constructed. The setup entailed a launcher for the acceleration of projectiles, a female die, a device for measuring the projectile momentum at the impact zone and a fixture for fastening the launcher and the die. The experiments included punching, stamping, extrusion, and forging, Special attention has been paid to the study of the microscale forging and extrusion. Forming of steel, spring steel, brass, aluminum, and copper samples was investigated. Dimensional stability and surface topography of the samples generated in the course of performed experiments were examined. The feasibility and effectiveness of the application of liquid impact for metal forming were shown.

Hidrodinamical model of an underwater projectile

The paper analyzes an underwater projectile. The input and output values, the projectile speed and acceleration are defined for a quality definition of the projectile mathematical model. With the conditions of the projectile potential movement previously set out, the torpedo model is defined by six equations. .

Stopping of ions based on semiclassical phase shifts

We develop a semiclassical theory of the stopping of ions in matter, aiming at a wide validity range in terms of ion energies and mass number. The excitation of a target electron is described as a binary ion-electron interaction governed by a screened-Coulomb potential. The energy loss is expressed in terms of the transport cross section for electron-ion scattering which is calculated in a semiclassical approximation to the scattering phase shifts. Exact numerical integrations of the Schroedinger equation are used for quantitative tests of the derived results. This approach provides a nonperturbative representation of the energy loss which bridges the gap between classical and quantal descriptions. It applies to nonrelativistic velocities for light and heavy ions with arbitrary charge states, and it reproduces typical quantum phenomena such as the oscillatory atomic-number dependence of stopping cross sections at low energies. Calculated results have been compared with predictions from linear and nonlinear stopping theory, in particular for stopping in the electron gas and by a quantum harmonic oscillator. Moreover, attention has been paid to the Bloch correction which, in the present scheme, approaches Bloch's well-known expression but does not blow up at low projectile speed. We have also determined a generalized Blochmore » correction which depends on the ion charge. Particular attention has been given to the description of static and dynamic screening of a dressed ion.« less

Bouncing steel balls on water

The ‘skimming’ of stones on water is a subject of perennial fascination for children andadults alike. In this article I describe the construction of an apparatus for safely andreproducibly demonstrating a similar phenomenon: the bouncing of 25 mm diameter steelballs from a water surface. The ‘bouncing’ is technically known as a ricochet and the articlerecounts the use of the effect in the Second World War in the ‘Dam Busting’ airraids of 1943. A number of calculations are made which allow an estimate ofthe projectile speed and energy, and the use of simple experimental techniquesfor validating these estimates is suggested. The role of spin is discussed, and aliterature review collates the available empirical and theoretical results concerning theincident angle and speed for successful ricochet of spinning and non-spinningprojectiles.

Effect of frame size, frame type, and clamping pressure on the ballistic performance of soft body armor

We analyze, with the computer code LS-DYNA, three-dimensional (3D) transient deformations of a 10-layer woven Kevlar armor held in a square steel frame and impacted at normal incidence by a 9 mm FMJ (full metal jacket), 124 grain projectile. The composite armor is discretized into weft and warp yarns to simulate its woven structure. The yarn is modeled as a 3D continuum. We consider failure of the yarn, and friction between adjoining layers and between the armor and the frame bars. For the armor perfectly bonded to the rigid frame bars, the computed residual speed and the residual kinetic energy of the projectile are found to increase with a decrease in the frame size implying thereby that the armor fixed in a smaller frame will have lower V 50 than that of the same armor clamped in a larger frame. (The V 50 of an armor equals the speed of a standard projectile that upon normal impact has 50% probability of just perforating the armor). For the armor allowed to slide between the frame bars, we have studied the effect of the pressure applied to the bars of the two- and the four-bar frames on the speed and the kinetic energy of the residual projectile. For both the two- and the four-bar frames, the speed of the residual projectile is found to increase with an increase in the applied pressure. Computed results also show that the armor fixed in the two-bar frame exhibits higher impact resistance than that held in the four-bar frame. The V 50 is found to be ∼270 m/s when the woven armor is held in a four-bar frame with a clamping pressure of 200 MPa. The V 50 decreases with an increase in the pressure applied to either the two-bar or the four-bar frames.

Laser-based projectile speed measurement system

The design and construction of a system to accurately determine the speed of a projectile (bullet) by measuring the time of flight between two parallel laser screens is described. Each screen is formed by a laser source and a set of prisms. At the detection end of each of the screens, a collector lens focuses the incident laser light beam onto a photodetector. The collector lens and detector are kept in a recess so that no stray or ambient light falls on the photodetector. Whenever a projectile crosses either of the screens, the corresponding photodetector senses the event, due to partial or full obscuration of the incident energy. An electronic circuit is used to accurately record the time when the projectile crosses each screen, and the time interval gives the time of flight. The distance between the screens being known, the velocity is displayed on a computer screen. Because a single collimated beam of light generates the entire optical curtain, the reduction in incident energy at the photodetector plane is independent of the entry point of the projectile into the screen. Due to the baffling of the photodetector from ambient light, the optical screens can be used at indoor or outdoor ranges equally effectively.

A new impact test for the identification of a dynamic crack propagation criterion using a gas-gun device

The modelling of damage and fracture behaviour under high rates of loadings for metallic structures presents the more and more interests for engineering design, especially for crash phenomena. In order to perform a numerical simulation of such phenomena a crack propagation criterion must be identified using adapted laboratory tests. The objective of this paper is to present a new impact test intended for the identification of a cohesive crack criterion implemented into a home-made FEM code based on Extended Finite ElementMethod. Therefore, a double-notched specimen is impacted using a gas-gun device in order to obtain different crack paths depending on projectile speed. A post-impact macro-photographic observation allows to measure the crack path, the angles and the advancing length. These experimental results are used as input responses in the identification procedure for determining the crack cohesive criterion parameters. Some experimental results, for an aluminium alloy crack criterion identification, are presented to illustrate the proposed approach.

Sliding along frictionally held incoherent interfaces in homogeneous systems subjected to dynamic shear loading: a photoelastic study

An experimental investigation was conducted to study dynamic sliding at high strain rates along incoherent (frictional) interfaces between two identical plates. The plates were held together by a uniform compressive stress, while dynamic sliding was initiated by an impact-induced shear loading. The case of freely-standing plates with no external pressure was also investigated. The dynamic stress fields that developed during the events were recorded in a microsecond time scale by high-speed photography in conjunction with classical dynamic photoelasticity. Depending on the choice of experimental parameters (impact speed and superimposed static pressure), pulse-like and crack-like sliding modes were observed. Visual evidence of sub-Rayleigh, intersonic and even supersonically propagating pulses were discovered and recorded. Unlike classical shear cracks in coherent interfaces of finite strength, sliding areas in frictional interfaces seem to grow at various discrete speeds without noticeable acceleration phases. A relatively broad loading wave caused by the interference between the impact wave and the preexisting static stress field was observed emanating from the interface. There was a cusp in the stress contours at the interface, indicating that the propagation speed was slightly faster along the interface than in the bulk. The observed propagation speeds of the sliding tips were dependent on the projectile speed. They spanned almost the whole interval from sub-Rayleigh speeds to nearly the sonic speed of the material, with the exception of a forbidden gap between the Rayleigh wave speed and the shear wave speed. Supersonic trailing pulses generating Mach lines of different inclination angles, emanating from the sliding zone tips, were discovered. In addition, behind the sliding tip, wrinkle-like opening pulses were observed for a wide range of impact speeds and confining stresses. They always traveled at speeds between the Rayleigh wave speed and the shear wave speed of the material.

Absolute cross sections for the production of positive atomic ions from dissociative collisions of [formula omitted], [formula omitted] and [formula omitted] in He

Absolute total cross sections are reported for the production of positive atomic ions from dissociative collisions of 1–5keV H3+, D3+ and HD2+ with He for scattering angles up to 5°. The cross sections are of the order of 10−17cm2 for all the processes studied in this work. In order to investigate the mass effect in the dissociation processes, the data are plotted as a function of the projectile speed. The cross sections from HD2+ are normalized to compensate for the relative fragment yield making possible the comparison of the mass effect over the dissociation processes, i.e. 3σ(H+) and 1.5σ(D+) have been considered. For equivelocity incident H3+, D3+ and HD2+, the H+ and D+ formation cross sections were the same within the accuracy of the experiment.

Single and double ionization of helium by the impact of fast charged particles

A survey of the recent literature shows that paradoxes abound in electron- and ion-impact ionization of helium. For example, Schulz et al. [M. Schulz, R. Moshammer, D. Fischer, H. Kollmus, D.H. Madison, S. Jones, J. Ullrich, Nature 422 (2003) 48] found that first-Born and three-body distorted-wave (3DW) theories reproduced their data for single ionization of helium by very fast fully stripped carbon ions in the scattering plane, but not outside the scattering plane. For much slower impacting carbon ions, however, Madison et al. [D.H. Madison, D. Fischer, M. Foster, M. Schulz, R. Moshammer, S. Jones, J. Ullrich, Phys. Rev. Lett. 91 (2003) 253201] found good agreement between 3DW theory and experiment, even outside the scattering plane. This creates a dilemma, since distorted-wave perturbation theories are generally thought to improve with increasing, not decreasing, projectile speed! In this contribution, we will address these and other issues, and suggest possible ways of proceeding.

Fully differential single ionization cross sections of helium by relativistic heavy-ion impact

We present three-dimensional images of fully differential cross sections for ionization of He by 1GeV/amu U92+ impact. This collision system corresponds to a relatively large perturbation (projectile charge to velocity ratio η=0.8) in spite of a relativistic projectile speed of 90% speed of light, representing a kinematic regime which so far is to a large extent still unexplored. Here, in spite of the large perturbation, higher-order contributions in the projectile–electron interaction are very small, but at the same time we find the projectile–residual target-ion interaction to be quite important.

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

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 function, and from those a number of mathematical and numerical results obtained previously with the implicit relation for the range are obtained more easily. The explicit solution for the range of the linear problem is then used as the zeroth-order term for the series solution of the range of the projectile with resistive force proportional to the nth power of the projectile's speed, in powers of δ = (n – 1)/2. PACS Nos.: 02.30.Gp, 45.20.Dd, 45.30.+s, 45.50.Dd

Performance optimization of hypervelocity launcher system using experimental data

This study presents the performance optimization of hypervelocity launcher system by using the experimentall data. During the optimization, the RSM (Response Surface Method) is adopted to find the operating parameters that could maximize the projectile speed. To construct a reliable response surface model, 3 full factorial method is used with the selected design variables, such as piston mass and 2 driver fill pressure. Nine test data could successfully construct the reasonable response surface, which used to yield the optimal operational conditions of the system using the genetic algorithm. The optimization results are confirmed by the experimental test with a good accuracy. Thus, the optimization can improve the performance of the facility.

Three-stage light-gas gun with a preheating stage

The performance of a three-stage light-gas gun with a preheating stage that uses hydrogen gas is described. In the preheating tests, in which the gun is not fired, the hydrogen gas was preheated up to 500 K and the temperature returned to room temperature in 250 ms. The preheated working gas was sealed in a pump tube constantly by using an improved big piston. In the firing tests, a projectile speed of 7.2 km/s, which is higher than the maximum speed without the preheating stage, was achieved with a 1.0 g projectile. It was shown that the light-gas gun is promising for a gas-dynamics gun in a wide range of operating conditions.

Radio-wave emission due to hypervelocity impacts in relation to optical observation and projectile speed

A hypervelocity impact causes the emission of radio-waves in the microwave frequency range. In order to understand the features of the phenomena and eventually to clarify the mechanism of the radio-wave generation, two kinds of experiments were carried out. The first one is the simultaneous observation of the phenomena by the micro-wave detection and the optical imaging method. The second one is to investigate the microwave emission in relation to the speed of a projectile. This paper describes the experimental results, and compares the microwave and optical methods from the viewpoints of impact detection.

Optimization and Evaluation of Coil Gun as a Target Injector for Laser Fusion

Target injector is an essential device to be established for a laser-fusion reactor. This paper describes current status of the injector research and introduces our research results of a coil gun. The drive circuits and trigger timing of the coil gun were optimized to improve injected projectile speed. The maximum speed at the first stage achieved to 8.7 m/s after optimization. The laser shot demonstration was carried out by the coil gun with an optically triggered Nd:YAG laser. The design guideline for a coil gun is discussed with experimental results and numerical simulation.

Ion-formation total cross sections from dissociative collisions of vibrationally relaxedH3+,D3+,andHD2+molecular ions with He

Total cross sections for the positive and negative fragments resulting from dissociative collisions with He of vibrationally relaxed ${\mathrm{H}}_{3}^{+},$ ${\mathrm{D}}_{3}^{+},$ and ${\mathrm{HD}}_{2}^{+}$ molecular ions have been measured in the energy range 3--9.8 keV. The measured absolute total-cross-section values are more than one order of magnitude smaller than those previously reported with the molecular ions without vibrational relaxation. When the cross sections are plotted as a function of the projectile speed and normalized to compensate for the relative fragment yield, the values for the production of deuterium fragments are higher than those for hydrogen ions in the energy range of the present study. These results are consistent with the theoretical predictions for the behavior of triatomic molecular ions with high rovibrational excitation.

Measurement of Impact Ejecta from Regolith Targets in Oblique Impacts

This paper reports the results of experiments on projectile impact into regolith targets at various impact angles. Copper projectiles of 240 mg are accelerated to 197 to 272 m s −1 using an electromagnetic gun. The ejecta are detected by thin Al foil targets as secondary targets, and the resulting holes on the foil are measured to derive the spatial distribution of the ejecta. The ejecta that penetrated the foil are concentrated toward the downrange azimuths of impacting projectiles in oblique impacts. In order to investigate the ejecta velocity distribution, the nondimensional volume of ejecta with velocities higher than a given value is calculated from the spatial distribution. In the case of the vertical impact of the projectile, most ejecta have velocities lower than 24% of the projectile speed (∼50 m s −1), and there are only several ejecta with velocities higher than 72 m s −1. This result confirms the existence of an upper limit to the ejection velocity in the ejecta velocity distribution (Hartmann cutoff velocity) (W. K. Hartmann, 1985, Icarus 63, 69–98). On the other hand, it is found that, in the oblique impacts, there are a large number of ejecta with velocities higher than the Hartmann cutoff velocity. The relative quantity of ejecta above the Hartmann cutoff velocity increases as the projectile impact angle decreases. Taking these results with the results of S. Yamamoto and A. M. Nakamura (1997, Icarus 128, 160–170) from impact experiments using an impact angle of 30°, it can be concluded that the ejecta from these regolith targets exhibit a bimodal velocity distribution. Below a few tens of m s −1, we see the expected velocity distribution of ejecta, but above this velocity we see a separate group of high-velocity ejecta.