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A multi-dimensional, transient, fluid dynamic model BISON has been developed to study the interior ballistic processes in an electro-thermal-chemical (ETC) gun. The model solves the full Navier-Stokes equations and uses a high-order numerical scheme to integrate the governing equations. Most of the important physical processes pertinent to ETC gun interior ballistics including multi-phase flow, chemical reaction and plasma dynamics are incorporated in the model. Examples of model applications to study basic ETC gun phenomena, such as plasma jet penetration and real gun design component analyses, are presented and discussed. The modeling results not only compare well with experimental data but also provide us with a better understanding of the interior ballistics physics. The multi-dimensional model BISON proves to be a very useful tool for ETC gun interior ballistics simulations.

Royal Ordnance are undertaking a fundamental research programme into the internal ballistics of electrothermal chemical guns. The research is separated into two inter-dependent programmes; numerical modelling and experimentation. The modelling separates the gun into three sections; power supply, plasma generator and gun chamber/barrel. The latter two are modelled using a finite difference Eulerian code, using flux corrected transport techniques in the algorithms. The experimental effort has concentrated on the fundamental physics of the plasma generator and has been confined to closed vessel experimentation. This paper presents the progress to date.

Presents information on a study which examined long-range ballistics to highlight the launch parameters of importance to electromagnetic gun designers. Atmospheric effects; Launcher energy limitations; Subcaliber projectiles; Conclusions.

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 will be 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.

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.

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 U.K. EM Gun Facility, Kirkcudbright, Scotland, at 7-MJ muzzle energy. [ABSTRACT FROM AUTHOR]

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 were focused on the 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. This paper 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 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 the 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. [ABSTRACT FROM AUTHOR]

Projectiles in coil gun usually make one-way movement and move at a very high speed. The device would be fit for the application of oil pumping unit, as long as the projectiles can make reciprocating movement and move slower by adopting proper control methods. At present, during the production process of petroleum, the efficiency of the system is rather low. Energy dissipation takes a considerable ratio in the total cost of oil production. Moreover, beam pumping-unit system suffers from long driving chain, poor flexibility, a quite huge capacity and weight under long length of stroke, and low efficiency. Aiming at the earlier problems, linear electromagnetic oil pumping unit is presented in this paper, which is essentially a multiphase coil launcher. Analysis is made about the advantages and disadvantages of three~phase and multiphase structures, as well as the practical structure. Simulation studies are made; meanwhile, experimental investigations are carried out on a small-scale-model machine system. Further simulation studies of coil launching system are carried through the mechanical and mathematical models of rod string in a sucker-rod pumping-unit system. Theoretical analysis and experimental results verify the feasibility and the validity of the proposed system. Thus, a new path to solve the problem of high energy dissipation in oil production is explored. [ABSTRACT FROM AUTHOR]

A conventional electromagnetic (EM) launcher propels a projectile with electromagnetic forces. By contrast, a Metafex launcher contains a dense, initially-inert material, activated by an electrical pulse, that reacts, creating a gas that propels the projectile. Because the reaction energy is four times as energetic as the electrical pulse, the ratio of projectile kinetic energy to electrical energy is much larger for a Metafex launcher than it is for a conventional EM launcher. Conventional EM launchers generally use long rails or barrels to gradually accelerate projectiles and are suitable replacements for entire guns. Metafex launchers are compact, provide rapid acceleration, and are more suitable for flyer plate applications. We have obtained positive test results for Metafex configurations that operate at practical voltages of approximately 20 kV. We describe the outcome of the testing, the potential uses of the material, and the opportunities for development of related pulsed power components such as capacitors and switches that will follow from Metafex commercialization. [ABSTRACT FROM AUTHOR]

Proposes a new method and ignition sensor aimed at providing direct experimental information about the propellant ignition process, as of January 2003. Methods in studying propellant ignition process; Principles used in the new method; Importance of the propellant ignition in the ballistic process.

Focuses on a study that presented a mathematical model and algorithms of the basic problem of interior ballistics of the electrothermal-chemical (ETC) launcher on slurry/liquid propellant. Use of electrical discharge on propellants; Performance of ETC slurry/liquid propellant; Mathematical simulation; Conclusions.

Presents the possible physical causes for lower performance than anticipated in experimental electrothermal-chemical firings using a one-dimensional code coupled to a plasma code. Discussion of experimental firings; Description of codes and 120-mm tank gun case; Calculations of ballistic ratio with plasma; Analysis on ignition and flamespread event; Comparison of gradients in physical variables with conventional solid propellant guns. Conclusions.

Examines the electrothermal-chemical (ETC) ballistic cycle to identify possible aspects of the ETC process leading to the lower-than-expected ballistic ratio (BR). Two mechanism that may contribute to the shortfalls of the ETC process; Background of the Examination; Analysis of ETC interior ballistic (IB) process; Conclusions.

Presents the Pulsed Power-Plasma-Interior Ballistic (PPIB), a PC-based, end-to-end electrothermal-chemical (ETC) gun ballistic simulation code developed by Princeton Combustion Research Laboratories. Analysis on the development of the PPIB code; Calculations of High energy plasma; Conclusions.

The FST-railgun is a new type of hypervelocity chemical-electromagnetic launcher for use as a high-pressure equation of state (EOS) research tool. To reduce the effect of barrel ablation of railgun and accelerate projectiles to higher velocities, the fast shock tube (FST), a cylindrical convergent high explosive (HE) launcher, is used as the injector of this novel railgun. The FST injector can provide injection velocities of up to 7 to 8 km/s, which results in final muzzle velocities of railgun up to 20 km/s with sufficient energy. The helium gas of the FST injector is partially ionized to plasma by strong shock waves driven by HE and the plasma is used as the armature of the back-stage railgun. This paper describes the configuration of FST-railgun and establishes an internal ballistics model of FST-railgun for analyzing the performance of the FST-railgun and evaluating the feasibility of experiment. The FST can also be used as the injector of electrothermal gun. This FST-electrothermal gun is also briefly introduced. [ABSTRACT FROM AUTHOR]

We investigated the effect of magnetic-electric barriers on electron transport in the two-dimensional electron gas (2DEG) of a Al-GaAs-GaAs heterostructure. It is found that electric potential can be controlled to achieve both spin and charge conductance modulation in this material system, with the requisite condition being the presence of magnetic barriers to break the time reversal symmetry of the system. The use of electrical potential rather than applied magnetic fields as an external control parameter to achieve spin/charge conductance modulation promises a simpler device design for practical realization. [ABSTRACT FROM AUTHOR]

In this paper, we model the effect of Rashba spin-orbit interaction, induced by structural inversion asymmetry, on the ballistic charge transport across a hybrid ferromagnetic two-dimensional electron gas (FM-2DEG) device, with a double tunnel junction. We show that the spin polarization of current and magnetoconductance (MC) of the device can be strongly modulated by the Rashba effect. [ABSTRACT FROM AUTHOR]

Focuses on a study that presented comparisons between high and low density cases for a number of ballistic parameters. Overview of the approach used to increase kinetic energy in the electrothermal-chemical guns in the United States; Description of gun system; Sensitivity to parameter changes; Conclusions.

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. Index Terms--Electrothermal-chemical (ETC) guns, experiment, interior ballistics, plasma ignition, simulation.

A precise and continuous measurement of the velocity of projectiles inside the barrel would permit to improve the understunding of the dynamic behavior of railguns. Friction-related questions, the mechanical stability of projectiles, or mass loss of armatures are problems to be mentioned in this context. One possibility to monitor the projectile dynamics is the use of a conventional Doppler-radar. In this paper, the experimental setup of a W-band Doppler system and its application at railgun experiments are described. First results obtained using a 15 x 30 [mm.sup.2] rectangular caliber railgun are presented. The maximum muzzle velocity for the series of experiments is about 1300 m/s. Depending on the quality of the electrical contact between rails and armatures, a very good agreement between the projectile dynamics measured by the Doppler-radar and the information given by several B-dot signals recorded at several positions along the barrel is obtained. If no electrical arcs are formed during the shot, the projectile is properly detected until it reaches the muzzle of the launcher (l = 3 m). Some aspects of friction are discussed to illustrate the evaluation of the data obtained. Index Terms--Armature, Doppler-radar, railgun.

In this paper we describe the development and illustrate the utility of end-to-end models of electrothermal launcher systems. The end-to-end model is comprised of a component that models the power supply, a component that models the plasma injector, and a component that models the interior ballistics processes. Appropriate coupling conditions are applied at the interfaces between the component models in order to make the end-to-end model self consistent. The component models are made modular so that models with varying degrees of complexity can be interchanged as needed for resolution. After describing the development of the end-to-end model we illustrate its use to analyze experimental results using two different levels of interior ballistics models. First, we use a control volume model of the interior ballistics process to simulate a test firing. Then, we illustrate the resolution that can be achieved with a two-dimensional model of the interior ballistics.

The augmentation of a ballistic process, based on the well known solid propellant burning by an electrothermal (ET) energy source, is the subject of an experimental and theoretical investigation to obtain improved launching techniques. The plasma jet formation method, the internal ballistics modeling approach and the experimental test bed are described. Experimental results are disclosed showing the enhanced burning rate of a solid propellant ignited and augmented by the injection of plasma jets. We also present preliminary experimental evidence of improved performance of the new proposed method over that of conventional ballistics using solid propellant alone.

Active electromagnetic (EM) armor is a new type of active defense system, which can intercept invading objects effectively. When hit by interception projectiles, the invading object will deviate from its trajectory or be destroyed totally. A steerable EM launcher system using two separate pancake coils is introduced in this paper, and its 3-D model is built. With finite element analysis code, acceleration process of the interception projectile is simulated, and laws of acceleration force acting on the projectile, its velocity, and displacement versus time are also investigated. Experimental installation is introduced, and experimental data are well matched with simulation results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A solid-propellant electrothermal-chemical (SPETC) 40-mm gun has been designed, constructed, and tested in the indoor firing facilities of the Soreq Propulsion Division Laboratory. An external injector device converts the electric energy stored in the capacitors of the pulse forming network (PFN) into a high-temperature plasma jet that penetrates the gun cartridge and boosts the whole ballistic process. However, unlike large-caliber SPETC systems, in which electric energy is limited to ignition purposes, the 40-mm SPETC gun is a genuine hybrid gun with almost equal electric and chemical contributions. There is experimental evidence that this unique feature induces a very peculiar initial propellant temperature compensation mechanism. It seems that when a significant part of the propelling energy comes from the plasma, i.e., electric energy is not only predominant at the ignition stage of the firing but also later on, then the temperature sensitivity of the propellant tends to vanish. A simple theoretical model supports the experimental findings. The large amount of electric energy is also responsible for a recorded ballistic improvement of 15% in the projectile muzzle kinetic energy. Calibrated simulations show that an optimal tailoring of the power pulse shape and suitable propellant grain geometry should further increase by 10% the muzzle kinetic energy. These modifications are in progress and results should be soon available. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

One of the main issues of railguns is the ablation of the rails due to the existence of a plasma arc occurring at high currents. To avoid the heat load on the rails, it is necessary to reduce the current intensities. The use of a parallel augmented railgun is one method of lowering the current without reducing the electromagnetic force on the projectile. One- and two-brush projectiles have been fired in a parallel augmented railgun with a 15 mm × 15 mm caliber and with a barrel length of 1.5 m. These experiments have shown that the maximum kinetic energy at the muzzle-without the transition of the solid contact between the rails and the brush to a plasma contact-can be significantly increased in an augmented railgun. The maximum kinetic energy has increased by a factor of 5 for one-brush projectiles and by a factor of 9 for two-brush projectiles. A model for the electromagnetic force in the augmented railgun and a friction model for the brush projectile are presented. The kinematics of the projectile in the gun are simulated with these models and are compared to the measured velocity. A good agreement is obtained. [ABSTRACT FROM AUTHOR]

Focuses on the research program of the Israeli Ministry of Defense on electrothermal-chemical (ETC) technology at Soreq NRC in Israel. Background information on research on electrothermal launch technology; Laboratory and experimental facilities; Theoretical and computational tools for simulating the phenomena involved in the ETC ballistic process; Details on plasma ignition propellants at high loading density.

This paper describes a preliminary experimental investigation to convey acceleration measurements, made on-board an electromagnetic (EM) launched projectile, using microwave telemetry techniques. The focus of the investigation is to extend the Hardened Subminiature Telemetry and Sensor Systems (HSTSS) technology for use in EM launch environments. Many aspects of the HSTSS technology have already been successfully demonstrated in high-G, high-pressure launch environments in conventional gun systems. In addition, microwave transmission in stationary experiments, where the telemetry package was exposed to relatively high magnetic fields and EM transients in a railgun launcher, has been demonstrated. However, microwave telemetry during an EM launch has not been demonstrated until now. In this work, setback acceleration measurements obtained with an on-board accelerometer were processed by HSTSS electronics and transmitted simultaneously during launch via an antenna located in front of the EM launch package. While only the test conducted at 9-kG peak acceleration provided the most useful data, detailed analyses suggest that mechanical problems--rather than the microwave telemetry process itself--were probably responsible for difficulties experienced at higher accelerations. This paper reviews the experimental methodology and discusses the results of the investigation. Index Terms--Accelerometer, FM, hardened, RF, S-band.

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. [ABSTRACT FROM AUTHOR]

The PEGASUS railgun at the French-German Research Institute of Saint-Louis is capable of launching 0.3-kg projectiles with muzzle velocities greater than 2500 m/s without mechanical failure of the sabot which is made of fiber-reinforced plastics. Unfortunately, for these high velocities, the metallic fiber brush armature shows contact transition. One of the main long-term objectives is to improve the railgun performance by delaying this armature transition, leading to an increase of the overall railgun efficiency and a reduction of the rail erosion. In order to obtain a better understanding of the transition mechanisms, several series of PEGASUS shots were examined with projectile masses ranging from 250 g up to 2 kg. As a result, a model was developed in order to predict the transition. It determines the mass loss of the brush armature due to electrical heating, mechanical shearing, and viscous heating. It can be shown for the low- weight high-velocity projectiles that friction heating becomes a predominant transition mechanism. For the 13-stage PEGASUS railgun, the transition model was implemented in a lumped parameter simulation code which takes into account the time-dependent armature voltage drop and the armature mass loss. The comparison of the computed transition time with measured values shows a very good agreement. [ABSTRACT FROM AUTHOR]

This paper deals with experiments and calculations performed in order to investigate the influence of the electromagnetic hardening of payloads in a railgun. This is a complex task: besides the large amplitudes of the in-bore magnetic fields due to the pulsed current, the exit of the projectile from the muzzle and the consequences of plasma arcs have to be considered. At the muzzle the magnetic induction can drop from several Teslas to zero within some microseconds, leading to very high induced voltages and electric fields in the metallic parts of the projectile. On the other hand, the electric contact established by solid armatures tends to develop into electric arcs at high velocities during the launch. These plasma arcs as well as the closing switch transients of the railgun circuit are a source of electromagnetic radiation in a broad spectral range. Some electronic devices were selected and tested with static setups corresponding to the previous conditions. In a first phase a series of static railgun experiments (no projectile movement) was performed. In a second phase, static experiments simulating the muzzle exit conditions were carried out. Finally, the influence of electromagnetic waves emitted during railgun experiments on electronic devices was investigated, using a static setup with a conventional spark gap. [ABSTRACT FROM AUTHOR]

Electrothermal-chemical ignition systems have been demonstrated in gun systems to provide desirable characteristics including reproducible shorter ignition delays. We present a combined theoretical and experimental study of the capillary discharge with an aim to develop a capillary plasma source with efficient energy conversion. The major emphasis in the present capillary discharge model is the ablation phenomenon. Consideration is given to different characteristic subregions near the ablated surface: namely, a space-charge sheath, a Knudsen layer, and a hydrodynamic layer. A kinetic approach is used to determine the parameters at the interface between the kinetic Knudsen layer and the hydrodynamic layer. Coupling the solution of the nonequilibrium Knudsen layer with the hydrodynamic layer provides a self-consistent solution for the ablation rate. According to the model predictions, the peak electron temperature is about 1.4 eV, the polyethylene surface temperature is about 700 K, and the pressure is about 10 MPa in the case of a 0.6 kJ discharge. In parallel, a parametric experimental study of the capillary ablation process is conducted. The ablation rates are measured for capillary tubes made of polyethylene and Teflon. Both experimental measurements and simulations indicate that the ablated mass increases with the peak discharge current and that a smaller diameter capillary yields a larger ablated mass. It is found that model predictions agree well with experimental measurements. [ABSTRACT FROM AUTHOR]

The three-year line of sight/beyond line of sight (LOS/BLOS) electrothermal chemical (ETC) launcher program, funded by the U.S. Army's Armament Research, Development and Engineering Center (ARDEC), Picatinny Arsenal, is a comprehensive effort to advance ETC launcher technologies. The program includes development of ETC plasma injectors for 120-mm M829A2s, build of a 100-kJ pulsed power supply small and robust enough to be realistically integrated into a combat vehicle, improvement of power connections to the gun to allow electromagnetic field containment and automated connection to the round, and tests of the completed ETC system with various chemical propellants and electrical energy levels. As part of the LOS/BLOS program, a new, coaxial version of BAE Systems' Basepad plasma injector has been developed and tested successfully in XM36, XM291, and M256 cannons. The Basepad's coaxial design effectively insulates the gun breech, thus preventing any part of the gun from being part of the high-voltage discharge circuit. A compact electrothermal ignition pulsed power supply (ETIPPS) has been designed, built, and tested. Including its own high-voltage charger, actuation circuitry, safety systems, and peripherals, ETIPPS's low weight and volume make it easily small enough for vehicle integration, as was demonstrated in a concurrent effort that included ETC firings from a combat vehicle. Test firings, currently ongoing, have validated the system architecture and performance and continue to supply data on performance at different temperatures, electrical energy levels, propellant loading, and propellant type. These tests demonstrate many of the benefits of ETC launchers including improved accuracy from precision ignition; maximum performance potential across all temperatures ranges (temperature compensation); and reliable ignition of new, high-energy, high-density, and in some cases low-vulnerability propellants. The system-wide approach of the LOS/BLOS electrothermal launcher program has advanced ETC technology significantly towards field readiness. [ABSTRACT FROM AUTHOR]

The exact forces and the way they act to accelerate and retard a projectile in a railgun and the correct model to represent the data have been debated for years. This paper demonstrates the use of a well known method (Chapman-Kirk) for identification of force parameters in a relatively simple nonlinear differential equation model of railgun projectile motion. Where other methods of parameter identification failed, this method converged well. The data used to demonstrate the procedure is a limited set of CHECMATE data (three shots at approximately the same conditions) and one shot from another gun. The input data to the procedure is the measured current and B time position data. Although the analysis of the results do not show that the model is adequate and correct over a wide range of operative conditions, the force parameters obtained are reasonable and some are substantiated by other methods.

Progress towards developing a first-principles capability to simulate the dominant physical processes in an electrothermal-chemical (ETC) gun is described. The computational model is the CRAFT Navier-Stokes solver which implements advanced implicit/upwind numerics with strongly coupled chemistry and generalized grid dynamics. The model provides a framework for incorporation of physics submodules developed by a team of Science Applications International Corporation (SAIC), Sandia National Laboratories (SNL), and the U.S. Army Ballistic Research Laboratory (BRL) scientists as well as industry and university researchers.

The results of an internal ballistic parametric study for an artillery weapon based on an electrothermal-chemical (ETC) propulsion system are reported. The study was carried out for four different calibres: 30 mm, 76 mm, 120 mm and 155 mm. Several different working fluids, both endothermic and exothermic, were considered for each calibre. Aspects considered include different proportions of electrical energy to chemical energy, working fluid masses and volumes, and the masses and volumes of the electrical power supply. Calculations were performed for two fixed muzzle velocities and for the case of the maximum stretch potential.

An electrothermal light gas gun (ELGG) has been developed that has launched 2.0 grams to about 7 km/sec, 10 grams to 4.6 km/sec, and 17 grams to 3.5 km/sec with an efficiency of 32%, from a 16 mm reusable steel gun tube. These initial experiments were with a single chamber breech fed launcher. The gun is scalable to large bore sizes and to date has close to the performance of a conventional light gas gun but removes the need for a heavy pump tube structure. It also has the potential to exceed conventional LGG performance when configured as a launcher with distributed H2 injectors, and a facility to explore this has been constructed.

Experimental gun firings and computer simulations of hybrid solid propellant-electrothermal gun propulsion concepts are reported. The test firings were conducted using loose and compacted ball propellant in a 30mm test fixture. A plasma capillary located at the breech of the gun was used both to ignite the propellant charge and to augment the ballistic process. Computer simulations of selected tests were conducted using modified lumped parameter interior ballistic models, which were originally developed for conventional charge simulations. More general optimization studies of the solid propellant electrothermal-chemical interior ballistic process are also discussed.

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. Index Terms--Burn rate, electrothermal-chemical, interior ballistics, solid propellant.