EM Gun Research Articles

Aerodynamics analysis of a hypersonic electromagnetic gun launched projectile

A hypersonic aerodynamics analysis of an electromagnetic gun (EM gun) launched projectile configuration is undertaken in order to ameliorate the basic aerodynamic characteristics in comparison with the regular projectile layout. Static margin and pendulum motion analysis models have been applied to evaluate the flight stability of a new airframe configuration. With a steady state computational fluid dynamics (CFD) simulation, the basic density, pressure and velocity contours of the EM gun projectile flow field at Mach number 5.0, 6.0 and 7.0 (angle of attack = 0°) have been analyzed. Furthermore, the static margin values are enhanced dramatically for the EM gun projectile with configuration optimization. Drag, lift and pitch property variations are all illustrated with the changes of Mach number and angle of attack. A particle ballistic calculation was completed for the pendulum analysis. The results show that the configuration optimized projectile, launched from the EM gun at Mach number 5.0 to 7.0, acts in a much more stable way than the projectiles with regular aerodynamic layout.

EM Gun Bore Life Experiments at Naval Research Laboratory

The Naval Research Laboratory (NRL) performs basic and applied research on high power railguns as part of the US Navy EM Launcher program. The understanding of damage mechanisms as a function of armature and barrel materials, launch parameters, and bore geometry is of primary interest to the development of a viable high power railgun. Research is performed on a 6-m, 1.5-MJ railgun located at NRL. Barrel studies utilize in situ diagnostics coupled with detailed ex situ analysis of rail materials to provide clues to the conditions present during launch. Results are compared with coupled 3-D electromagnetic and mechanical finite element analysis models of railgun operation. Results of several experiments on rail wear will be discussed.

For Love of a Gun

This paper reviews the tumultuous history of electromagnetic launchers. It also studies various aspects of electromagnetic launch (EML), including an intriguing use in tank armor. Most of all, the recent history of railgun research is a cautionary tale about military R&D. The U.S. Army and Navy envision EM guns as a key component for the next generation of all-electric vehicles.

Design of an 8-MJ integrated launch package

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.

The operational value of long range land attack EM guns to future naval forces

The US Navy has been investigating the possibility of applying EML technology to long range ship-based land attack guns. EM guns offer the potential to extend naval fires to operationally significant ranges at costs markedly lower than present day missile or aircraft weapon systems. The US Navy has yet to commit significant investment in EM guns, but may do so in the future because of the increased emphasis on the land attack mission. The utility and feasibility of a long-range (over 300 nmi) naval EM gun has been investigated. It was determined that a naval system could be fielded in 20 to 30 years with a reasonable investment in fundamental research, followed by full scale gun development and platform integration. This paper answers the question "Why should a modern power projection navy make such an investment in EM gun development". The potential war fighting value of a naval EM gun system is discussed. Based on some notional performance parameters for an EM gun fieldable in the 2030 time-frame, conceptual employment schemes are outlined for attacking land targets from the sea in a manner that cannot be done today. The sensor and communications networks needed to realize the full utility of a long-range land attack EM gun is introduced. Second order implications of adopting EML as the primary naval gun technology is also discussed.

EM gun scaling relationships

Sub-scale system test results and the experiences gained during fabrication and testing can be extremely valuable for success with the full scale system. This publication focuses on the EM gun scaling relationships between the full and sub-scaled systems' field variables. Derivations of the scaling relationships presented are based upon the magnetic, thermal and momentum differential equations and a few basic EM gun equations. It is shown that the EM gun field variables of the two systems can be matched or scaled linearly (the peak values are scaled while their distribution characteristics are unchanged), if the scale factors of the gun dimensions, the gun current pulse, etc. are chosen properly. With the proposed linear scaling method a wide range of different scalings is possible. Cases of nonlinear scaling can be solved approximately in the average sense. The presented scaling relationships are applied to an example to demonstrate.

Integrated thermal management of a hybrid electric vehicle

A thermal management methodology, based on the Vehicle Integrated Thermal Management Analysis Code (VITMAC), has been developed for a notional vehicle employing the all-electric combat vehicle (AECV) concept. AECV uses a prime power source, such as a diesel, to provide mechanical energy which is converted to electrical energy and stored in a central energy storage system consisting of flywheels, batteries and/or capacitors. The combination of prime power and stored energy powers the vehicle drive system and also advanced weapons subsystems such as an ETC or EM gun, electrically driven lasers, an EM armor system and an active suspension. Every major system is electrically driven with reclamation when possible from braking and gun recoil. Thermal management of such a complicated energy transfer and utilization system is a major design consideration due to the substantial heat rejection requirements. In the present paper, an overall integrated thermal management system (TMS) is described which accounts for energy losses from each subsystem component, accepts the heat using multiple coolant loops and expels the heat from the vehicle. VITMAC simulations are used to design the TMS and to demonstrate that a conventional TMS approach is capable of successfully handling vehicle heat rejection requirements under stressing operational conditions.

Rail heating analysis for multishot EM gun operation

This paper describes a method of analyzing potential railgun concepts for their rail heating effects in multishot mode. The method is meant to provide a quick estimate of heating effects based on the geometry of the rails and containment and the performance specifications of each shot. First, a coupled electrical-mechanical simulation is run for the railgun in which the effects of current diffusion are included to calculate the effective rail resistance and associated heating as a function of axial position and time. This analysis is then expanded with an assumed current distribution (relative amount of current on top and back of rail compared with the front) to develop a first order temperature distribution in the rail cross section at any specified axial location. This axial section is then subjected to two-dimensional finite element analysis (FEA) to determine the heat redistribution between shots. A sample set of calculations is compared with a single shot experiment incorporating temperature probes in the rails. Finally, the utility of the method for multishot analysis is shown with two simulations, one with and one without active cooling in the rails.

Launching tactically configured solid armature projectiles from large and medium calibre railguns-results from the DRA test programme

One of the main thrusts of the United Kingdom EM gun programme is to prove the feasibility of accurate hypervelocity flight of projectiles launched from an EM gun. Several notable successes have been achieved in pursuit of this goal. To date DRA has carried out almost 70 large and medium calibre solid armature experiments using 40 mm and 90 mm round bore railguns. With one or two exceptions all firings have employed monolithic aluminium alloy armatures, the majority in base-push configuration. So far, approximately half of the shots have been full tactical packages with discarding sabots and long rod sub-projectiles flown over range. This paper presents results from these tactical package firings and observations on armature performance based on analysis of shot data and recovered specimens. Other gun issues that may be important to any future implementation of EML technology in a weapons system are also discussed.

Combustion driven pulsed linear generators for electric gun applications

Energy storage and pulse forming for electromagnetic and electro-thermal chemical guns has historically been accomplished through the use of complex power trains. Such power trains typical involve a prime power source, electrical or mechanical power conversion devices, capacitive or flywheel energy storage devices, and sophisticated switching and control elements. Kaman Electromagnetics (KEC) has developed concepts for simpler pulse power systems where chemical energy is converted more directly into an electrical output which can be utilized by an electric gun load without further conditioning. One family of devices which has shown considerable promise is the linear flux compressor. Early work with flux compressors used explosives and was suited only for microsecond duration pulses. More recent efforts utilizing propellants and even conventional hydrocarbon fuels can provide millisecond duration pulses which are well suited for electric gun type loads. Internally funded efforts indicate linear flux compressor pulse power supplies can be considerable smaller and lighter than conventional systems. This paper presents the operational principles and design issues of linear flux compressors suitable for EM guns. Point designs, performance simulations and general scaling relationships are also presented.

Prime power and pulsed energy storage for EM gun equipped tank combat missions

This paper describes initial simulations carried out for a sample all-electric combat vehicle based on a generic tank-like mission profile. Variations in prime power and pulsed energy store capacity are examined under stationary and dynamic move-and-shoot conditions over a simple 30 minute mission profile, and a more complex 50 minute engagement. Results show that by sharing power between the mobility and weapons systems, the prime power required can be reduced significantly from that required by the old method of summing up the worst case loads. Further discussion for continued reduction of the power system required is also included.

Overview of some recent EML efforts within Russia

The research program in the USSR and then in Russia included the study of the potentials of different types of electromagnetic launchers of solids: railguns, ET guns, ETC guns. In this survey, primary emphasis is placed on railguns. Pulsed power problems for EM guns will not be discussed in this paper. Traditionally, the potentials of electromagnetic launchers of solids have been studied in two aspects - basic research and applied (military) research. This paper presents the results of fundamental studies. Also, the plans of some research teams for the nearest years are briefly outlined.

‘Field’ guns: electromagnetic launchers

The tank weapons of the future may be able to fire without any help from unstable, dangerous chemical reagents. Instead they may use electromagnetic guns. In an electromagnetic gun, the projectile is pushed by an electromagnetic field pressure. In principle this force can be propagated at the speed of light, so in principle, the electromagnetic gun should be able to produce much higher velocities than powder guns. As well as the higher muzzle velocity, the EM gun has logistical advantages for the tank crew that has to use it. These advantages come at a cost in terms of convenience, however. The gun system has a low energy density, which means that the launcher must be heavier and bulkier than a conventional gun barrel. The author describes the formation of the railgun armatures and the design of railguns. The research being carried out in this area in the UK is discussed. The testing of the guns is also discussed.

Effective launch package integration for electromagnetic guns

Many engineering disciplines must be considered when designing launch packages for electromagnetic guns. These include electromechanics, plasma physics, fluid dynamics, structures, materials science, aerodynamics, thermodynamics, flight dynamics, and terminal effects. Often, the requirements of one discipline will be in direct conflict with the requirements of another. Each discipline can claim to be of overriding importance, but all aspects of launch package design must be considered if the gun system is to succeed in its mission. Choices must be made regarding launch package configuration. Base-pushing or mid-riding solutions are possible with solid, hybrid or plasma armatures. Fully optimized launch package designs must be used in comparisons to find the actual optimal design point. The most effective design for one gun system will not necessarily be the most effective for another. This paper discusses the interplay among the various engineering disciplines involved in launch package design. Successful testing of integrated projectile/armature/sabot configurations from 90 mm EM guns is reviewed. >

Experiments with the Green Farm electric gun facility

The design and construction of a major electric gun facility at Green Farm in San Diego is described. The facility is driven by an 11 kV 32 MJ capacitor bank, arranged in 4 MJ modules that can be independently triggered to provide a choice of pulse shapes. The bank has powered a variety of EM and ET guns, including an 8-meter Single Shot Rail gun and a modified 5-inch Naval gun. World record high energy and high velocity shots have been achieved. The highest rail gun muzzle energy was 8.6 MJ and the highest muzzle velocity was 4.3 km/s with a plasma driven projectile of 0.64 kg, corresponding to a muzzle energy of 6 MJ. Intact projectile launch and flight was confirmed by high speed (8000 frames/sec.) photography and flash X-rays. >

Nanoscale/Multilayer Gradient Materials for Application in the Electromagnetic Gun Systems

AbstractAnalysis of fired rails from electromagnetic railguns indicates severe surface damage occurs due to high current arcing and tribological mismatch. We have explored the behavior of several nanoscale multilayered materials as possible routes to improve the thermomechanical properties of the rail and armature materials . Structures investigated include (i) Ti-Co alloy on Ta-Cu alloy on dlc (diamond-like carbon) on stainless steel; (ii) Ti-Co alloy on Ta-Cu alloy on dlc on Cu, (iii) Ti-Co alloy on Ta-Cu on Cu; and (iv) Ti-Co on Ta-Cu alloy on Al. The alloys were all 50:50 at% and film thicknesses were in the range 400-1000 Å. The films were formed using a repetitively pulsed vacuum arc plasma deposition method with substrate biasing- and IBAD-like techniques. The surfaces were characterized by scanning electron microscopy, transmission electron microscopy, Rutherford backscattering spectroscopy, optical microscopy, microhardness measurements, arc erosion resistance and scratch resistance tests. Preliminary results show improvement in the microhardness, arc erosion resistance and scratch resistance, most especially for the dlc-coated surfaces. This kind of multilayered approach to the fabrication of electromagnetic railgun and armature surfaces could be important for future advanced Electromagnetic EM Gun systems.

Tantalum Ion Implantation into Cu-12Nb for Electromagnetic Railgun Technology

ABSTRACTAnalysis of fired rails from electromagnetic railgun indicates gross surface melting near the breach end of the rails. This effect is most likely caused by joule heating and arc erosion. To improve the mechanical behavior of the rail material, alloys of copper, such as Cu-0.6 Nb, has been used in the past with moderate success. More recently another alloy of copper, Cu-18 Nb, has become available. Preliminary metallurgical research in the thermomechanical properties of this latter alloy indicates it could be a candidate for application in EM gun systems. In this effort we have attempted to study the influence of ion implantation on the thermomechanical properties of Cu-12Nb alloy. In a series of experiments, Ta ions have been implanted at an energy range of 100–180 KeV and a dose of 5 × 1016 cm-2. Several analytical techniques such as Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), arc erosion, and microhardness measurements have been done. It has been shown that although there is an improvement in the microhardness of the implanted materials, the ion implantation saturation dose cannot exceed 5 × 1016 cm-2. Furthermore, the RBS data indicate that the implanted Ta resides mostly at a depth of about 200–300 Å from the surface. Results from the SEM analysis of unimplanted Cu-12Nb indicate the Nb has an acicular morphology and is randomly distributed. Results from microhardness measurements of the implanted materials indicate that implantation enhances the microhardness. In another experiment, such as implantation of Ta in an already TiN coated surface, we observed a similar increase in the microhardness value. We speculate that the microhardness improvement of Cu-18Nb or the Ta implanted TiN surface is due to induce compressional stresses near the lenticular (filament) Nb fibers in the Cu-18Nb composite.

Surface Modification of Electromagnetic Railgun Components

ABSTRACTCopper and aluminum used for rail and armature materials in electromagnetic railgun systems undergo severe degradation during the EM gun operation. The extent of this degradation is especially severe in guns operated at high energy levels or designed for repeated firings. In an effort to improve surface properties of the copper rail, armature, and sabot materials, the technique of metal ion implantation using a vacuum arc ion source has been employed. Preliminary tests have been conducted to identify the best implant species to improve spark erosion resistance, scratch resistance and hardness. The implanted species included Al, Ti, Cr, Ni, Ta, Ag, and W. The implantation energy range and dose varied between 100–180 KeV and 0.4 to 2 × 1017 cm-2, respectively . Several analytical techniques were also used to assess the effect of implanted species. These included Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Microhardness Measurements, Spark Erosion and Scratch Testing. It has been tentatively concluded that Ta and Ni implantation of the copper rail substantially improve wear and inhibit arc erosion. There is also sufficient evidence to indicate that implantation of the aluminum armature with Cr and Ta, involving two stages of implantation, will also improve its mechanical and wear properties.

Development and validation of the ARDEC Army Railgun Modular Simulator (ARMS)

An electric gun computer simulation code has been developed, tested, and validated at the Army Research and Development Engineering Center (ARDEC). The Army Railgun Modular Simulator (ARMS) is a railgun and pulse power supply numerical code that predicts the time-variant response of a coupled electromechanical system. The ARMS code is a PC-based program which uses a user-friendly input interface called the Designer and a companion numerical simulator called the Simulator. Both the Designer and Simulator use a building block, or modular, approach to modeling a complete EM gun system. With this approach the computer program is readily reconfigurable and adaptive to the changing needs of the experimentalist and program manager alike. An overview of the current status, features, program architecture, mathematical rationale, and future software directions for the ARMS code is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

EMGWS, D1 projectile tests

The 90 mm EMGWS D1 projectile is an unguided projectile that is designed for launch from an electromagnetic gun to achieve significant armor penetration. The 90 mm D1 type II workhorse projectile is used to test material strength, fabrication techniques, and projectile structural integrity. The type II flight projectile is designed to allow maximum stress levels of 100 ksi when launched at 100 kg peak acceleration. The total weight of the projectile is 2.0 kg to attain a muzzle velocity of 3.0 km/s from a 9 MJ EM gun. The type II projectile configuration employs a tungsten nosetip plus 12 segmented tungsten penetrators, a two-piece aluminium discarding sabot, an aluminium pusher plate, and a nylon orbturator. The pusher plate, can incorporate either a solid or plasma armature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>