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Firing accuracy is a critical quantity of interest in the performance analysis of electromagnetic railgun (EMRG) exterior ballistics. Since the simulation technique is always used to simulate the complex physical system at a low cost, it is employed to evaluate the firing accuracy of railgun projectile with uncertainty in this paper. An exterior ballistics simulation model of the railgun, including 3-DOF flight mechanical model, relative kinematic model, and guidance law model, is developed to simulate the ballistics behavior in the missile target intercept mission. The firing accuracy is studied in this paper to compare the capability of EMRG with different ranges and muzzle velocities. In order to explore the firing accuracy of the guided projectile, the guidance precision analysis and ballistics uncertainty quantification are studied. In the guidance precision analysis, the shot range and efficiency are used to make a comparison. In addition, the sensitivity analysis and firing accuracy analysis are also performed in terms of uncertainty quantification. The simulation results illustrate that the simulation of the guided projectile can give some practical guide to the projectile design of EMRG. [ABSTRACT FROM AUTHOR]

Energy efficiency is a critical quantity of interest in the performance of electromagnetic railgun (EMRG). To improve the energy efficiency of EMRG with the presence of uncertainty, a hybrid robust optimization method is proposed. EMRG simulation model is developed to simulate the behavior of exterior ballistics and the corresponding robust optimization issue is formulated. With the help of the impact factor analysis, several significant factors of energy efficiency are selected as the design variables while the insignificant ones are not taken into account. In the robust optimization, the polynomial chaos expansion approach coupled with Latin hypercube design is proposed to propagate the uncertainty for alleviating the computational burden of fitness function (energy efficiency) evaluation. Then, the genetic algorithm is employed to solve the EMRG energy efficiency optimization problem with the constraint of mean miss distance. The optimization results illustrate that the hybrid robust optimization method is an efficient approach to improve the energy efficiency, which can be applied in the practical application of EMRG projectile design. [ABSTRACT FROM AUTHOR]

Electromagnetic railgun (EMRG) is a promising candidate weapon system for the future surface-fire support mission characterized by quick response, hypersonic velocity, and high damage efficiency. Since the huge power consumption during launching, priority should be given to the precise strike. Firing accuracy of EMRG, which refers to the closeness degree of the projectiles’ impact points to the target, is an important performance metric in the EMRG exterior ballistic performance assessment. To provide a systematic solution for the measure of firing accuracy, the assessment factors are formulated in detail. Then, a general framework, including trajectory simulation, data preprocessing, parameters estimation, and hit probability calculation, is proposed to evaluate EMRG firing accuracy. Considering the trajectory simulation experiments may be time consuming, a new multicriteria optimal Latin hypercube design method is presented to maintain the balance between experiment time and sampling performance. Finally, firing accuracy assessment of 16-kg projectiles is performed using the designed framework and proposed experimental design method. The result reveals that the circular error probability is about 5 km under current defined scenarios, which means the initial disturbances may have great impact on the firing accuracy of projectiles without guidance and control units. [ABSTRACT FROM PUBLISHER]

We have already presented a compact model for FETs operating in the quasi-ballistic regime [1]. However, this model suffers from two important problems: 1) the profile for charge density along the channel is not correctly accounted for and 2) current is not conserved throughout the channel. In this brief, we propose improvement, which does away with these inaccuracies. [ABSTRACT FROM AUTHOR]

A simple model of negative capacitance (NC) MOSFETs is presented. The model treats 2-D electrostatic effects, and the ballistic to diffusive transport regimes. It shows quantitative agreement with numerical device simulations based on a self-consistent solution of the Poisson equation and quantum transport equation based on nonequilibrium Green’s function formalism, for an NC MOSFET structure without an internal floating gate. The model can accurately describe the reverse drain-induced barrier lowering (DIBL) and negative output differential conductance (NDC) effects as the NC FETs scale down. With approximations valid at low power supply voltages, it is shown that the improvement of the subthreshold swing (SS) due to electrostatic short channel effects results in a linear increase of the reverse DIBL and NDC. For a modified NC MOSFET structure with an ultrathin quantum metallic layer contacted to the source, the SS, however, can be improved considerably with the reverse DIBL and NDC approximately unchanged. [ABSTRACT FROM PUBLISHER]

In this paper, we present an analytical semiempirical model of the profile of the channel charge and potential in quasi-ballistic double-gate (DG) MOSFETs. The charge model is based on the premise of separating the charge density in the quasi-ballistic channel into two hypothetical components: 1) exclusively ballistic (collision-free) and 2) collision-dominated components, which are governed by the same electrostatics. These components are related to each other through a ballisticity parameter whose values lie between 0 and 1. Varying the value of this parameter allows us to model the charge profile continuously between diffusive and purely ballistic devices. Using the proposed charge model and the DG MOSFET electrostatics, an analytical expression for the channel potential is derived which, like the charge model, is continuous between the diffusive and ballistic regimes. [ABSTRACT FROM AUTHOR]

The thrust provided by a plasma source, open at one end, is calculated for an arbitrary ratio of collision to ionization rates. If the plasma is of a low collisionality, ion pumping is dominant, and the momentum of the jet exiting the source is carried mostly by the plasma. In the collisional regime, neutrals are accelerated through charge-exchange collisions with ions, leading to neutral pumping, so that most of the momentum of the jet is carried by the neutral gas. It is shown that these ion–neutral collisions increase the thrust for a given power. However, the conventionally defined efficiency for a thruster, reflecting also the propellant utilization, is lower in the collisional regime. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the electron mobility in nanowire (NW) FETs operating under quasi-ballistic conditions. Starting from a general expression of the current-voltage characteristics worked out in a previous work, we determine the limiting current at low drain voltage and find the functional dependence of the carrier mobility versus device and gate lengths, barrier height, and momentum-relaxation length. The expression resulting from this procedure is nonlocal and is proved to be given by the Matthiessen's combination of ballistic and scattering-limited mobilities in NW-FETs, thus accommodating the transition between these two limiting transport conditions. Moreover, the relationship between mobility and backscattering coefficient is highlighted, showing that the former is simply proportional to the latter. One of the main results of this paper is that the combined effect of acoustic-phonon and surface-roughness scattering leads to a weakly varying mean-free path versus effective field, at least for NW-FETs with a diameter around 5 nm. Thus, mobility degradation at large gate voltages is predominantly due to carrier degeneracy, which is particularly severe in 1-D structures, rather than an enhanced scattering rate. Finally, we propose a methodology for the extraction of the average momentum-relaxation length from experimental measurements of the drain conductance, which does not require a separate measurement of the carrier density. [ABSTRACT FROM AUTHOR]

Ballistic transport has been of interest in semiconductor devices for quite some time, and its effect has been used to predict quite-different device performance. Here, we investigate the role of ballistic transport in a short-channel InGaAs/InAlAs HEMT through full-band cellular Monte Carlo simulations. We can examine the contrast in behavior between when scattering mechanisms are present and when they are turned off. When the scattering processes are completely removed, the output characteristics show a distinct change in behavior over all drain voltages. This result is in qualitative agreement with prior arguments, suggesting that triodelike behavior should be expected due to enhanced drain-induced barrier lowering. However, we find that explicit band-structure effects are observable in the output characteristics of the ballistic transistor. We also find that this distinctive behavior gradually disappears as scattering is turned on, particularly in the drain end of the device. We also develop a method of determining the probability that electrons pass through the gate region in a ballistic manner in the presence of realistic scattering. Even when the gate is only 10 nm long, we find that this probability is only on the order of 50% in these devices. We also examine the ballistic ratio in our device as a function of gate length. [ABSTRACT FROM AUTHOR]

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]

This paper examines the validity of the widely used parabolic effective mass approximation by computing the ballistic injection velocity of a double-gate, ultrathin-body (UTB) n-MOSFET. The energy dispersion relations for a Si UTB are first computed by using a 20-band sp³ d5 s*-SO semiempirical atomistic tight-binding (TB) model coupled with a self-consistent Poisson solver. A semiclassical ballistic FET model is then used to evaluate the ballistic injection velocity of the n-type UTB MOSFET based on both an TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic band model with bulk effective masses is found to be reasonably accurate as a first- order approximation until down to about 3 nm, where the ballistic injection velocity is significantly overestimated. Such significant nonparabolicity effects on ballistic injection velocity are observed for various surface/transport orientations. Meanwhile, the injection velocity shows strong dependence on the device structure as the thickness of the UTB changes. Finally, the injection velocity is found to have the same trend as mobility for different surface/transport orientations, indicating a correlation between them. [ABSTRACT FROM AUTHOR]

We propose an efficient and fast algorithm to solve the coupled Poisson-Schrödinger and Boltzmann transport equations (BTE) in two dimensions. The BTE is solved in the relaxation time approximation within each subband obtained from the direct solution of the Schrödinger equation. The proposed approach, considering a subband-based transport formalism, allows to fully explore the entire range from drift-diffusion to ballistic regime in nanoscale field-effect transistors. Quantum effects are also fully taken into account by the direct solution of the Schrödinger equation. The model is implemented in the NanoTCAD2D device simulator and used to study the device performance of a 25-nm channel-length MOSFET. The influence of scattering on the electron distribution function and on device characteristics is analyzed in detail. [ABSTRACT FROM AUTHOR]

We discuss selected aspects of the physics of electronic transport in nMOSFETs at the 10-nm scale: Long-range Coulomb interactions, which may degrade performance and even prevent ballistic transport from occurring; scattering with high-κ insulator interfacial modes, which depresses the electron mobility but is found to affect minimally the saturated transconductance of 15-nm devices; and the use of high-mobility small effective-mass substrates, which poses serious concerns related to performance limitations due to the density-of-states (DOS) bottleneck and to the band-to-band (Zener) leakage current. On the basis of our results, we argue that ballistic transport may not only be unachievable (because of unavoidable electron-electron collisions) but may also be undesirable, as it may enhance the DOS bottleneck. We also argue that the knowledge of low-field mobility is of little use in predicting quantitatively the performance of devices in the saturated region. [ABSTRACT FROM AUTHOR]

In this paper, we propose a quasi-analytical device model of nanowire FET (NWFET) for both ballistic and drift- diffusion current transport, which can be used in any conventional circuit simulator like SPICE. The closed form expressions for current-voltage (I-V) and capacitance-voltage characteristics are obtained by analytically solving device equations with appropriate approximations. The developed model was further verified with the measured I-V characteristics of an NWFET device. Results show a close match of the model with measured data. [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]

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]

This paper is based upon the observation that, when a bullet is fired, it creates characteristic markings on the cartridge case and projectile. From these markings, over 30 different features can be distinguished, which, in combination, produce a ‘fingerprint’ for a firearm. By analyzing features within such a set of firearm fingerprints, it will be possible to identify not only the type and model of a firearm, but also each and every individual weapon just as effectively as human fingerprint identification. A new analytic system based on the fast Fourier transform for identifying projectile specimens by the line-scan imaging technique is proposed in this paper. This paper develops optical, photonic, and mechanical techniques to map the topography of the surfaces of forensic projectiles for the purpose of identification. Experiments discussed in this paper are performed on images acquired from 16 various weapons. Experimental results show that the proposed system can be used for firearm identification efficiently and precisely through digitizing and analyzing the fired projectiles specimens. [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]

Two state models and a measurement model for estimation of relative kinematics using measurements from RF seekers are proposed. The state vector for the first state model includes the acceleration of the target along with target-interceptor relative position and velocity in the state vector. In the other state model, the jerk of the target is also included among the state variables. Both models also include the ratio of the air density and the ballistic coefficient and its time derivatives as elements of the state vector to account for the aerodynamic drag in the endo-atmospheric phase. Such formulations obviate the need for assuming empirical models of air density and drag coefficient. In the proposed measurement model, the line of sight (LOS) angle is derived from the seeker measurements of LOS rate and gimbal angle and used for measurement update of the state estimator. This reduces the dimension of the measurement vector and obviates the need for modeling the dynamics of the seeker tracking and the stabilization loop. Performance results of the proposed methods have been compared with a well- known model from the literature under closed-loop guidance employing the augmented proportional navigation (APN) law for endo-atmospheric ballistic target tracking. It is clearly seen that the proposed methods yield more accurate estimates of target acceleration in terms of reduced mean error and a more favourable cumulative distribution of miss distances that effectively increase the probability of hit for a given warhead lethality radius. [ABSTRACT FROM PUBLISHER]

In this paper an acceleration model and a jerk model are proposed for estimation of the kinematic state of reentry ballistic targets (RBTs) using extended Kalman filters (EKF). The models proposed here use the equations of target kinematics only and do not assume any model parameterization for variation of the ballistic coefficient and air density a priori, as found in the literature. The novelty lies in estimation of the ratio \gamma of air density and ballistic coefficient and its time derivatives using a separate Kalman filter (KF) \gamma which utilizes pseudo measurements of \gamma computed from the velocity and acceleration estimated by the EKF at each time step. The parameter \gamma and its derivatives estimated by the \gamma-filter are, in turn, used for the estimation of position, velocity, acceleration, and jerk in the EKF. The use of the pseudo measurements of \gamma makes the algorithms inherently adaptive to variations of the ballistic coefficient and air density during reentry. A comparative assessment of several dynamic models for reentry of ballistic targets reported in the literature and those proposed here demonstrates that the estimation errors in velocity and acceleration are significantly less for the proposed models compared with the existing ones. [ABSTRACT FROM AUTHOR]

The theory of operation is presented, together with experimental results, of a projectile target scoring system that determines highly accurate hit locations of small arms fire by processing constant frequency CW radar Doppler phase content into a trajectory estimate. We describe a new algorithm for extracting trajectory parameters from Doppler time series to obtain time, distance, and velocity at closest approach. Vector trajectories are derived by combining multiple scalar trajectories from three radar units. Live fire test results from a local range and Aberdeen Proving Ground are provided to show that a hit location accuracy of 4 cm can be achieved reliably on small arms. [ABSTRACT FROM PUBLISHER]

The article reports on the development of a ballistic computing transistor by a team of U.S. university researchers. University of Rochester professor Marc Feldman leads a team of experts in computer engineering, circuit design, computer architecture, and theoretical physics in working on the ballistic deflection transistor (BDT), a technology for creating ultra-fast, energy-efficient chips developed by Quentin Diduck. Some of the problems regarding transistor approaches dealt with by BDT technology are discussed.