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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 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 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]

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]

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]

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]

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]

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 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]

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]

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]

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]

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.

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.

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.

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.

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.

We calculate the magnetoresistance of the single-walled carbon nanotube biasing by using ferromagnetic electrodes in different alignments of magnetic polarization. In large polarization of the ferromagnetic electrodes, the magnetoresistance is significant and easily reaches saturation at small bias, which suggests spintronic devices are possible by using carbon nanotubes. [ABSTRACT FROM AUTHOR]

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]

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]

Electron transport property in the nanocontacting wire was investigated by measuring magnetoresistance effect. In the regime of conductance quantization, the magnetoresistance exhibits the quantized step (in the unit of e² /h) and nonquantized step (ΔG < e² /h). The magnetoresistance effect appears to be large in the case that either of the steps was observed in a magnetoresistance curve, indicating that there are different mechanisms which bring about the giant magnetoresistance. [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]