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This paper describes theoretical and experimental work aimed at the development of a new class of high-speed projectiles with superior penetration performance. Our earlier publications [1, 2] were focused on finite element analysis of projectile-target interaction over a wide range of impact speeds. The projectiles were made of tungsten or alumina, and the target plates were made of aluminum, steel, or tungsten. Subsequently, finite element modeling was performed for ceramic rods encased in metal shells and launched against reinforced concrete [3]. The current work expands the range of ceramic and ceramic-based composite materials for use in high-speed projectiles. Materials were compared based on their mass density, Hugoniot elastic limit, fracture toughness, deformability and ability to withstand intense aerodynamic heat during high-speed flight and penetration. Finite element analysis was performed for ceramic and tungsten projectiles impacting metal plates at speeds ranging from 0.5 km/s to 6.0 km/s. Several transient phenomena such as ceramic projectile self-sharpening, multiple impacts, spall, and buckling were observed. The computation results were used for design and manufacture of high-speed projectiles with superhard tips made of commercially available diamond composites. Experiments involved several projectile configurations. The penetration depth of reference steel projectiles into concrete decreased with increased impact speed while the penetration depth of the projectiles with diamond tips increased. Clusters of ceramic and metal-ceramic projectiles and fragments can find use against larger and softer targets and in the generation of debris.

The Soreq Propulsion Physics Division has recently initiated the development of a small-caliber pure electrothermal (ET) weapon. This paper reports the promising results obtained with a 25-mm ET gun. The currently mature gun technology based on conventional ballistic process is mostly limited because: 1) the propellant burning features dictate a curve that is entirely determined by the grain geometry and cannot be changed "online" and 2) the pressure gradient between the breech and the projectile's base strongly depends on the molecular weight of the combustion gases, which is almost propellant formulation independent. Removing the first limitation and reducing the second one is the key of the ET technology. ET guns use electric energy as the unique source of propelling energy. It is converted into a high-temperature plasma which interacts in the chamber with an inert cooling fluid that serves also as a propelling working fluid. In this study, two types of working fluids were tested: polyethylene and water. Polyethylene was found unsuitable for our purposes. Experiments, supported by simulations, show that the degree of water dissociation was enough to produce the required working fluid. Using 750 kJ of ET energy, 20% improvement in kinetic energy was obtained with a standard projectile without exceeding the maximum authorized breech pressure. It has been shown that the well-known barrel erosion issue is mostly due to the aggressive abrasion of the cartridge metal by the hot plasma jet. A new cartridge concept has been especially designed to overcome this problem. Results are very satisfactory

The main motivation of this work is to clarify whether the hopes of significantly improving the performance of the conventional guns by using plasma ignition have a realistic basis. We assessed the possibility of improving the whole interior ballistic process, its repeatability and safety, through a uniform propellant ignition. In addition, we planed to improve the gun performance [the projectile muzzle energy (velocity)] by "forcing" "cold" charges to perform as "hot" ones (achieving "temperature compensation"). All of these goals are intended to be accomplished by using reasonable electrical energies (which would allow the reduction of the mass and volume of the power supply). We also avoided any significant changes in the conventional gun topography in order to prevent unacceptable costs. The presented research program proved that by using a standard 105-mm gun (concerning its barrel length and charge chamber volume) and a standard propellant, improved performances (more than 28% in the projectile muzzle energy) can be achieved while dense charges are used. In addition, significant reduction of the important effect, the "temperature gradient," is obtained. The capacity of plasma as the ignition factor to provide ballistic gain has also been demonstrated

Under some simplified assumption conditions, this paper establishes and deduces a one-dimensional coupling model of solid propellant electrothermal-chemical gun (SPETCG). In the model, the quality and momentum and energy conservation when plasma flow and powder particles coupling each other are considered, at the same time, the temperature gains proper dynamical disposition. At last, according to the model, simulation of SPETCG is calculated and the result quantified is analyzed and discussed.

An overview of the electro-thermal-chemical launcher (ETC) research program at the Propulsion Physics Laboratory, Soreq NRC, Israel is presented. The main avenue explored is a detailed study of solid propellant ETC (SPETC) performance and optimization. A better knowledge of the physical phenomena taking place inside the device and in parallel efforts to tackle the engineering aspects of specific weapon systems based on the SPETC concept. Theoretical and experimental tools have been developed. Permanent efforts toward developing optimal and efficient components for such systems are invested. A second avenue is the design and the construction of a small-caliber ETC demonstrator, as an answer for present military demands for urban combat conditions. All system options are dealt with including a novel inductive pulse power supply.

This paper describes the design of an 8-MJ base-pushed launch package for railgun launch. Extensive interior ballistics and flight dynamic analyses were performed. The launch package was designed to withstand a peak acceleration of 57 k-gees, and a substantial amount of lateral load. The lateral load was of prime importance for this launch package to ensure survivability of subprojectile joints present inside. Even though the launch was by a base-push method, a sabot was necessary to carry the bore-riders. Sabot separation dynamics and projectile aerodynamic coefficients were evaluated to ensure a successful flight. The package was successfully tested at the 32-MJ UK EM Gun Facility located at Kirkcudbright, Scotland at 7-MJ muzzle energy.

The utilization of high-speed compulsators is central to the success of the electromagnetic pulsed power launch systems under development. The efficient use of these high-energy storage devices depends, in turn, on high-strength carbon composite bands for attaining sufficient speed, and thus energy levels, without disintegrating. While advances in material science allowed significant improvements in the performance of the latest generation of compulsators, a growing concern is their vulnerability to ballistic impact. A comprehensive experimental study using a scaled but realistic version of an operational compulsator is presented. A set of two test rotors consisting of several layers, including a simulated coil section and an outer carbon confining shell, was tested. The rotors were spun to approximately 18 000 r/min in a high-speed test facility, and shaped charges were fired at the outer shell at normal incidence. The results of a set of experiments are presented, showing damage ranging from benign to complete failure, depending on the impact energy level.

The ignition of solid propellants by plasma jets with high temperature and density has been suggested as an improvement over conventional primers. Plasma ignition may enable the ignition of propellant charges with high loading density and/or low sensitivity, which is difficult using conventional primers. In addition, plasma ignition can provide a better control of the ballistic process, improving repeatability and enabling compensation for the propellant temperature effect. Due to the typically large volume and weight of electrical energy storage devices and pulsed power systems, which increase with the required energy, it is important to reduce the amount of plasma energy needed for ignition. In this paper, we present and analyze experiments performed in a gun simulator as well as a series of 105-mm gun firings. The aim is to improve the understanding of the plasma-propellant interaction at low plasma energies, in order to reduce the energy needed for a proper propellant ignition and smooth ballistic process.

The realization of proper interior ballistic performance in a large-caliber electrothermal-chemical (ETC) gun requires a well-defined interaction of the plasma ignition system with ETC-tailored propellants and charge designs. Before testing the interior ballistic cycle in a large-caliber gun, basic investigations in closed vessels and firing simulators have to be performed. In order to conduct these investigations, a 70-mm firing simulator has been designed and fabricated at Rheinmetall, Unterluess, Germany. The paper gives an overview on the setup of the 70-mm firing simulator. In the following, the design of the propellant charge to be tested is described briefly. Results obtained from preliminary interior ballistic simulations on the charge setup are presented. An overview on the test program is given and results of firings at different propellant temperatures are described and evaluated.

The physical and chemical phenomena involved in the ballistic process, both in conventional guns and in electrothermal-chemical (ETC) guns, are very complex, so that optimization of gun performance requires a detailed understanding of the influence of different parameters. The initial stage of propellant ignition is critical to the rest of the process, in terms of both performance (muzzle velocity, repeatability) and safety. A better understanding of the ignition stage is thus very important in achieving improved performance. In this paper, we propose a new method and ignition sensor aimed at providing direct experimental information about the propellant ignition process. We further report on measurements of the ignition delays, and the propagation of the "ignition wave", performed using these sensors in experimental devices such as closed bombs and gun simulators.

This paper presents the validation of a sabot discard model, developed at the Institute for Advanced Technology (IAT), for predicting armature/sabot separation, and quantifies the effect of electromagnetic launch on sabot discard as well as on the sub-projectile. The experimental data used to validate the model were obtained at the Army Research Laboratory (ARL) Transonic Experimental Facility at Aberdeen Proving Ground, MD. Five shots were conducted at a nominal velocity of 1350 m/s and armature/sabot petal trajectories were reduced from X-ray images taken at six downrange stations. The residual electromagnetic force on the launch package after muzzle exit was also determined from experimental data. The sabot discard model uses analytical expressions to estimate surface pressure distributions, which are then integrated, in a time-marching algorithm, for linear and angular accelerations, and subsequently for sabot petal trajectories. The most significant attribute of this model is that it does not rely on any empirical data for modeling and is therefore expected to be widely applicable. The results from this study have shown that the comparison between predicted and measured armature/sabot petal trajectories is excellent. Furthermore, the model has demonstrated quantitatively the delayed armature/sabot discard caused by the residual electromagnetic force and the additional deceleration of the sub-projectile due to the delayed mechanical disengagement.

The use of telemetry in gun-launched projectiles is not as common as in missile and aircraft systems. A primary reason is the launch environment of guns. Conventional solid propellant guns often produce launch accelerations approaching 100,000 g's. Additionally, if the bore is rifled, large lateral accelerations are also produced. Recently, the Hardened Subminiature Telemetry and Sensor System (HSTSS) program has developed and demonstrated a series of telemetry products and technologies specifically designed to make gun-launched in-bore and flight measurements more routine and affordable. This paper reviews the products and flight experiences from the HSTSS program and addresses the potential use of the HSTSS products and techniques for use on projectiles launched from electromagnetic rail guns.

The energy transport by radiation is one of the most important effects in an electrothermal-chemical (ETC) accelerator. At the beginning of the ETC round, after the initiation of the plasma e.g. by an exploding wire, the plasma radiation is responsible for the ignition of the propellant and the observed enhancement of mass production. This could be validated by different closed vessel tests e.g. at TZN and ICT. Therefore the radiation energy reaching the propellant has to be known for the description and understanding of the plasma-propellant interaction. Furthermore radiation energy leaving the hot plasma core enhances the temperature of the colder plasma boundary layer and the surrounding powder gases. For this reason the calculation of radiation transport is necessary to simulate the temperature and pressure development during the interior ballistics processes of an ETC round. A simulation program is described, which can be used for studying the plasma-propellant interaction and which can be used directly in gasdynamic codes, like the 2D code IBECA, for solution of the energy balance equation.

The "smart gun" is a concept designed to control the muzzle velocity, and hence reduce the dispersion, of projectiles fired from artillery guns by using electrothermal energy. Simulations have been undertaken to assess the potential of the "smart gun" concept. This paper describes experiments conducted in a 30 mm smooth bore ETC gun designed to validate some of these simulations. The ETC gun employed a breech mounted capillary plasma generator. A sequence of electrical pulses were delivered to the plasma generator. The first pulse ignited the propelling charge. A relatively long pulse (the sustain pulse) was then discharged to maintain current flow within the plasma capillary for an extended period of time. At varying times after the ignition pulse, a "boost" or "smart gun" pulse was discharged. The shorter the time interval between the ignition and "smart gun" pulses the more effectively energy is transferred to the projectile and the greater the increase in the projectile's velocity. The results are shown along with a comparison of the simulations. The efficiency with which the electrical energy in the "smart gun" pulse was transferred to the projectile was calculated for each delay employed.

The Defence Evaluation and Research Agency (DERA) is investigating a number of different electrothermal-chemical (ETC) gun concepts which utilize solid propellants. One of these concepts uses a capillary plasma generator (CPG). In the CPG concept, electrical energy (EE) is discharged into a polyethylene tube, open at one end only, through two electrodes which are located at each end of the capillary. Plasma vents from the open end of the capillary into a combustion chamber which contains a charge of solid propellant. This paper describes some modeling of 155 mm ETC gun firings that used the CPG concept. In these firings the EE was used either to ignite the charge or to augment the combustion process at pressures up to about 80 MPa. In order to simulate successfully these gun firings, it was necessary to assume that enhanced burning, due to the plasma, of the solid propellant occurred. This paper describes the modeling that was conducted for the 155 mm ETC gun firings and compares the simulations with measured results. The simulations were conducted using one-dimensional (1D) and two dimensional (2D) internal ballistics codes and investigate the zone of influence of the plasma.

The ability of electromagnetic (EM) guns to launch payloads at very high velocities has been shown to enable some new potential for long range bombardment from both ship and shore. This paper examines long-range ballistics in detail to highlight the launch parameters of importance to EM gun designers. The use of kinetic energy at long range for target defeat is introduced in the atmospheric effects section of this paper and later examined through specific case studies. High kinetic energy, on target, is a key capability enabled by the higher launch velocities associated with EM guns. This paper also shows the sensitivity of range, impact energy, and time of flight on the launch velocity in the regime of high altitude trajectories (enabled by EM launch).

Experiments have shown that an electrically-generated, ablation-stabilized plasma is an effective ignition stimulus in electrothermal-chemical (ETC) guns. The current generation of ETC concepts in the United States utilizes a small amount of electrical energy during the ignition process of the order of the chemical energy in conventional igniters. Thus, in order to obtain the significant muzzle kinetic energy increase that has been demonstrated in the US with ETC guns in comparison to fielded systems, a new generation of energetic materials has been developed with increased impetus and improved packing properties. The propelling charge loading density (propellant mass/initial free volume in the combustion chamber) his risen concurrently in direct fire applications from the conventional 0.85-0.95 g/cm/sup 3/ to a value up to 1.35 g/cm/sup 3/ in experimental firings. The increase in loading density and concomitant decrease in initial ullage in the combustion chamber changes the sensitivity of the charge and the multi-phase properties of the interior ballistic flow. In this paper the authors present comparisons between high and low density cases for a number of ballistic parameters. Experimental data are also examined to compare the pressure gradient in conventional guns versus high loading density cases.

The most important research results and the prospect directions for the electromagnetic (EM), electrothermal (TT) and electrothermochemical (ETC) launch in Russia are presented in this paper. The development of pulse power supplies, materials, projectile ballistics and simulation is also considered.

Researchers at the Weapons and Materials Research Directorate of the Army Research Laboratory (ARL) have recently completed experimental testing with a G-hardened gun-launched miniature instrumentation package that fits within the projectile fuze cavity for obtaining realistic in-bore, deceleration, and projectile impact data. This device consists of an accelerometer and a digital recorder that is designed for the reliable capture of ballistic data during projectile launch, flight, and target impact. During recent flight test evaluation at the ARL, Aberdeen Proving Ground, projectiles containing this device were tested with a telemetry link as well as recovery and direct downloading of onboard recorded data. For projectile impact studies both concrete and bunker targets were successfully engaged. This methodology of onboard data recording has been shown to provide a reliable and high-fidelity characterization of projectile in-bore and impact events critical for advanced munitions designers

A detailed experimental investigation of the launch and flight performance of a kinetic energy fin-stabilized penetrator has been performed. The integrated launch package (ILP) consists of the subprojectile and mid-riding armature. The armature front contact is electrically insulated from the rails. This configuration has shown potential for effectively managing the launch disturbances. To evaluate the transitional ballistics, aeroballistics, and jump characteristics, single-shot firings with an exit velocity of 1350 m/s were conducted at the ARL Transonic Experimental Facility, APG, MD. The impact data show larger variability in the vertical direction than in the horizontal direction. Results from the jump survey indicate that effects of the deviation from the launcher centerline (i.e., straightness) contribute significantly to the target impact dispersion. Substantial contributions from the linear and angular rates at the muzzle are evident in the vertical direction. The contribution attributable to sabot discard in either plane is minimal. When possible, comparisons are made to our earlier investigation which examined the ballistic behavior of a similar ILP with a conducting front contact.

A series of experiments were conducted for examining the disturbances acting upon a subprojectile during electromagnetic launch. This investigation uses a number of performance indicators, including target impact dispersion, to quantify the causes. The effects of armature contact configuration and in-bore acceleration profile on the launch process were considered. The test program consisted of two armature contact configurations and two in-bore accelerations. Twenty-eight shots were fired, of which 15 were slugs. For the test matrix, the nominal exit velocity was 1100 m/s. The in-bore acceleration profile was varied by diverting the armature current with a time delayed closing switch, located at the muzzle of the railgun. Effects from the launch disturbances were quantified by use of flash X-rays, smear camera photography, and yaw card and target impacts. The time-rate-of-change of launcher and switch currents and launcher voltages were measured. Results indicate significant differences in ballistic performance for the two front contact configurations. Also to a lesser extent, differences were observed for the two in-bore acceleration profiles. In-bore dynamics initiated from the deviation from the bore centerline are believed to cause these differences.

Today the electrodischarge light-gas launcher (EDL) is not only the subject of investigation, but may be a suitable tool for different kinds of explorations. Such a hypervelocity accelerator gives the possibility to carry out experiments on impact interaction over a wide range of velocities (up to several kilometers per second) with substantial accelerated body masses. This experiment demands the creation of special impactor which in turn requires the launch package design. This paper considers the development of launch package for multiple rod hypervelocity impact investigation. Distinctive features of multiple rod impact investigation are the requirements to the simultaneity and desired impact geometry of interaction (mutual position of penetrators and approach angle). To meet all mentioned demands penetrators were placed in inseparable holding cartridge. The exact approach angle was ensured by means of aerodynamic stabilization. The holding cartridge has to be made from materials with least possible density to decrease its Influence on interaction process. At the same time the holding cartridge has to be strong enough to withstand the overloads during the in-bore acceleration. In this paper the design and test results of the launch package for the multiple rod hypervelocity impact studying are presented. All experiments were carried out with the (EDL) of 30-mm caliber. Hydrogen under the initial pressure of 40 MPa was used as a working gas. It permits us to use the projectiles with masses up to 150 g and explore the velocity range from 1500 up to 3000 m/s.

In recent years, great strides have been made regarding the identification of the dominant loads that cause beam type vibrations of cannons during ballistic operation. These motions infringe upon shot accuracy because at projectile disengagement, the muzzle's kinematic state may compromise the projectile's intended flight path. This is particularly relevant to coil gun loading, which, unlike gas launch, applies the recoil load to the muzzle end of the barrel instead of the breech. This effectively places the barrel in a state of columnar compression during the launch cycle that may exacerbate structural vibrations known as gun "whip".

Historically, electrothermal-chemical (ETC) gun firings have failed to achieve ballistic performance as measured by ballistic ratios (BRs) commensurate with those for conventional powder guns. In this paper, the ETC ballistic cycle is examined in an attempt to identify possible aspects of the ETC process leading to the lower-than-expected BRs. Results indicate that at least a partial answer may be the energy required to evaporate and dissociate the polyethylene and metal electrodes of the plasma capillary, state changes which occur in the combustion gases due to the higher temperatures of the plasma and radiative energy losses.

A projectile using a metal powder buried in a polycarbonate is used so that an impact experiment between materials of higher specific mass, such as metal and metal, may be carried out. The projectile could be accelerated above 6 km/sec and it was confirmed that the powder stayed in its original configuration in the polycarbonate base without any deformation during flight. To prove the effectiveness, impact experiments were performed in which the total weight and the diameter of the projectile, with and without the metal powder, are fixed for comparison. Using 2.5 cm thick stainless steel as a target, the produced craters are compared. The crater made by the projectile with palladium (Pd) powder is much deeper than the one with the simple polycarbonate projectile. Moreover, a two stage crater structure is obtained which implies that higher pressure and higher temperature impact has been realized. >

Electrothermal-chemical (ETC) guns offer the prospect of significantly increased muzzle kinetic energy over conventional solid propellant gun systems as evidenced by experimental data collected over the past several years. To support the various experimental programs, codes developed specifically for ETC interior ballistic processes have matured including 0D, 1D, and 2D/3D models. Although these models in general have been successfully applied to simulate experimental data, prediction of gun interior ballistic performance at high gun energies has been more difficult. In this paper we examine comparisons of 0D and 1D model results with experimental data in order to gain a clearer understanding of the way that electrothermal energy input modifies the interior ballistics in ETC guns. These comparisons suggest that both axial and radial effects must be considered, necessitating development of first-principles 2D/3D models. Results from one such model, CRAFT, are presented in the paper. >