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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.

Exterior ballistics performance evaluation plays a critical role in the design and development of the electromagnetic railgun system. The ballistics performance evaluation can be regarded as a multicriteria decision-making problem, for the reason that various characteristics, also termed criteria, have effects on the overall performance. A sophisticated simulation model, including six-DOF mechanics, railgun configuration, environment, and aerodynamics models are established to compute the exterior ballistics profile. Then a comprehensive framework based on cloud model and analytic hierarchy process method are proposed to evaluate ballistics performance. Eight criteria including ballistics velocity, energy efficiency, flight time, flight range, overload, attack angle, and sideslip angle stability are selected to determine exterior ballistics performance. The proposed approach yields the certainty degree of each criterion and integrates multicriteria into the whole performance. Two scenarios including 32-MJ launch energy and 200-km strike range are taken to generate alternatives for assessing ballistics performance, which demonstrate the proposed approach is feasible. Results show that in the same launch energy 32 MJ, the performance levels of 12- and 16-kg projectiles are I (excellent) and III (medium), respectively. Besides, gaining the projectile’s mass can improve performance in the same strike range 200 km.

The French-German Research Institute of Saint Louis proposed an innovative concept of a microair vehicle (MAV). The gun-launched MAV (GLMAV) is a new and original type of discreet and robust miniature hybrid system of about 1 kg for a very quick observation mission by air. The GLMAV in a projectile configuration is launched by a portable dedicated tube weighing less than 10 kg. After a ballistic flight, the GLMAV is transformed into a miniature drone with automatic deployment of coaxial counter-rotating rotors. The GLMAV in drone configuration is slowed down to be able to execute hovering or/and maneuvering flights. In few seconds, aerial observation down and forward can begin in order to capture information, because it is equipped with an embarked vision system with real-time image transmission. This paper is first focused on the conception of the launcher and of the platform in order to incorporate all the features coming from multiple disciplines. This hybrid system conception is linked to an iterative process between all fields of research such as aerodynamics, interior and exterior ballistics, mechanics, electronics, optronics and signal transmission, guidance, navigation, and control. All theoretical studies presented in this paper have then converged toward the manufacturing of the dedicated ballistic launcher and of the GLMAV platform. The latter is now ready for the autopilot implementation in the near future.

Wind can and often does significantly affect impact-point prediction (IPP) performance for thrusting/ballistic endoatmospheric projectiles. Wind exacerbates the estimation ambiguity between drag and thrust in the dynamic model and induces additional uncertainty in the IPP procedure. A tracker accounting for the wind effect is presented and simulation study shows that it can be fully compensated if the wind information is available. An-point adaptive initialization based on a goodness-of-fit test and a statistical significance test is introduced. Based on the multiple interacting multiple model (MIMM) approach developed recently, the IPP performance is investigated with respect to the total observation time and the sensor accuracy in various wind scenarios. In each Monte Carlo (MC) run of the simulation study, under the same sensor accuracy and the same observation time, the same set of random numbers has been used (but different in different MC runs) for the same caliber projectile in various wind scenarios to examine how much the wind affects the IPP performance with/without the exact knowledge of the wind information. The final conclusion is that with the wind effect accounted for, the IPP performance in the presence of wind is practically the same as in its absence.

We present an attitude estimation method for self-guided ballistic munitions from onboard magnetometers. An adaptive feedback filter is used to remove actuator-induced magnetic disturbances whose spectrum overlaps the signal of interest. A state-augmented extended Kalman filter (EKF) is used to estimate roll rate and sensor bias from the filtered data. Experimental results demonstrate that this method is able to accurately estimate the roll without phase delay inherent in other methods.

We present a procedure to estimate the state of thrusting/ballistic endoatmospheric projectiles for the end purpose of impact point prediction. The short observation time and the estimation ambiguity between drag and thrust in the dynamic model motivate the development of a multiple interacting multiple model (MIMM) estimator with various drag coefficient initializations. A simple unbiased IMM mixing procedure (useful for quite general applications) is presented for state estimators with unequal dimensions and applied for the thrusting and ballistic modes in the case considered. Results with real data are given.

A low-altitude endoatmospheric interceptor, which is steered by aerodynamic lift and divert thruster, is investigated in this paper. The divert thrust is provided by a solid rocket engine with a single public combustion chamber and a group of nozzles around the missile. As a result, it can be used only once. To utilize the divert thruster effectively and to determine the width of the divert thruster pulse, a logic-based guidance strategy is proposed. Moreover, the decomposition of the game space is employed to analyze the appropriate initiating time of the divert thruster. Finally, the validity of the guidance strategy is tested using a realistic 2-D ballistic missile defense scenario. It is shown that, due to the sufficient utilization of the divert thruster, there is a significant improvement in the homing performance.

This paper presents a multiple model procedure to estimate the state of a ballistic object in the atmosphere and identify it using radar measurements for the purpose of impact point prediction (IPP). A key aspect of the projectile identification is the identification of the mode of stabilization used, i.e., fin stabilization or spin stabilization. Measurements are taken during the first part of its trajectory up to apogee, and the final state estimate obtained by the multiple model estimator is then predicted to its impact point on Earth. For each model a different extended Kalman filter (EKF) is used for state estimation, and the model likelihoods are then used to identify the projectile. It is shown from simulations carried out on three fin-stabilized projectile trajectories (mortars of different caliber) and a spin-stabilized (howitzer) projectile trajectory that the projectile can be identified with a high probability and also that the impact point is predicted to a high degree of accuracy and with a consistent covariance. It is also shown that accurate modeling of the gyroscopic effect caused by the spinning of the howitzer projectiles is critical for IPP accuracy in the case of spin-stabilized projectiles. The key in the design of the multiple model filter (MMF) is the choice of the models, which based on the characteristics of the different projectile trajectories, have different state dimensions. A choice has to be made between too few state components, which leads to poor accuracy/consistency, and too many state components, in which case the accuracy and discrimination ability suffers because of too much uncertainty in the model.

An interacting multiple model (IMM) filter is presented for the real-time tracking of tactical ballistic missiles (TBMs). The novel aspects of the proposed IMM filter include the development of a constant axial force (CAF) Kalman filter, asymmetric IMM state interaction, and an entropy-based variation of the IMM mode probability update equation. Using data from a recent TBM defense (TBMD) test event, the proposed IMM filter is shown to yield consistent state estimates throughout the entire TBM trajectory, which includes a dual-stage boost during launch.

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

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

An improved acoustic target is considered. Acoustic targets estimate the hit coordinates of a supersonic projectile using the time of arrival (TOA) of the supersonic shock wave at several acoustic transducers located in the vicinity of the target. An improved target allows oblique hits, likely in firing practices involving roaming infantry and armor. Four trajectory parameters are estimated: two hit coordinates (x,h) on a virtual, vertical, target plane; horizontal angle of incidence; projectile velocity. Explicit expressions are provided of the expected TOA measurements and their derivatives with respect to the estimated parameters. The expressions simplify a least-squares iterative algorithm and accelerate its convergence. Expected error contour maps are provided.

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

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

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

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

The Airdrop Ballistic Winds (ABW) team at Wright-Patterson AFB, Ohio, conducted flight tests of its 2 /spl mu/m laser radar (lidar). This system, called the Operationally Capable Lidar (OCL), was installed in a modified C-130 fuel pod. The OCL was designed to: (1) provide real-time, 3-D maps of wind fields between the aircraft and the ground; and (2) significantly improve airdrop accuracy from high altitudes. This paper briefly describes the OCL, the Precision Airdrop simulation (PADS) tool, and flight test activities, including the Precision Airdrop Integrated Demonstration.

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

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

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

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. >

A multidimensional, transient, fluid dynamic model, BISON, has been developed to study the interior ballistic processes in an electrothermal-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 multiphase 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 a better understanding of the interior ballistics physics. The multidimensional model BISON proves to a very useful tool for ETC gun interior ballistics simulations. >

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 30-mm 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. >

A dual-density Rodman cone, with 1/d=7, has been found to be attractive for electromagnetic launch and may have adequate terminal ballistic performance. Stable flight is achieved from the correct distribution of mass within the projectile body. The design provides some flexibility for the armature in that all the armature mass is used for aerodynamic stability. Furthermore, the acceleration can be supported by a simple one-piece armature. A bore rider, which is less than 10% of the total mass, is needed for in-bore stability and structural support at the tungsten/aluminum interface. Work to date has focused on small-caliber applications, but substantial gains can be achieved when the bore size is increased to cannon caliber. General design principles for a mass stabilized projectile are presented. Nearly all aspects of launch, flight, and terminal effects as a function of bore size are addressed. Flight and terminal effects are computed from curve fits to existing experimental data. >

A railgun for the study of the interaction of meteorites with planetary surfaces and the interaction of space debris was developed. The authors have attained a velocity constantly higher than 5 km/s, with a maximum of 6 km/s. The importance of plasma confinement behind the projectile to prevent a leakage is shown to realize a high velocity. An effective acceleration using an aluminum rail is also shown. >

The impact of launch acceleration on the design of electromagnetic launcher barrels and on the design of associated launch packages is discussed. This is of particular interest because launch package size and mass directly affect the overall armament system size and mass. A common design approach is to use as the peak launch acceleration the maximum acceleration which the projectile can be designed to withstand. While this approach will minimize barrel length, it may also yield an excessively large overall system size and mass, especially for the long, slender projectile configurations which are desired for high aero-thermal and terminal ballistics performance. An alternate design approach which balances the goals of reducing barrel length ad reducing launch package mass is described. Results illustrate the benefits of this balanced design approach on overall armament system size and mass. >

LTV Aerospace and Defense Company (LTVAD) using the company's highly reliable, reusable electromagnetic (EM) railguns have conducted over 200 projectile launchings since the second Electromagnetic Launch Technology Symposium and have established a projectile/launcher data base covering interior as well as exterior ballistic considerations. Projectiles weighing 2 to 43 grams have been launched with the LTVAD EM launcher lab's 12.7 and 20 mm railguns over the velocity range of 1.5 to 8.5 km/sec. This paper describes the interface and compatibility relationship between an EM launcher and the launch package during the interior ballistics of launch and the influence on the subsequent exterior ballistics. Some terminal effects and test descriptions conducted at LTVAD are presented along with associated projectile monitoring instrumentation utilized in determining projectile motion, integrity, orientation, flight characteristics, and impact phenomenology. This work was sponsored by the Army Ballistic Missile Advanced Technology Center.

A program was initiated to design, build and evaluate the performance of a two-stage light gas gun, utilizing hydrogen gas, for use as an injector to an electromagnetic railgun. This effort is part of a project to develop a hypervelocity electromagnetic launcher for equation-of-state studies (HELEOS). The specific design features that enhance compatibility of the injector with the railgun, including a slip-joint between the injector launch tube and the coupling to the railgun, are described. The operational capabilites for using all major projectile velocity measuring techniques, such as in-bore pressure gauges, laser and CW (continuous wave) X-ray interrupt techniques, flash X-ray, and continuous in-bore velocity measurements using VISAR interferometry, are discussed. An internal ballistics code for optimizing gun performance has been utilized to interpret performance data of the gun. >

Millimeter wavelength radars are used to study plasma effects associated with ionized flow fields of projectiles launched at hypersonic speeds into a free-flight ballistic range. Two CW Doppler radars, at frequencies of 35 and 70 Gc/s, measure the nose-on backscattering radar cross sections during flight. The design and performance of the two radars are described in detail. A signal simulator provides absolute calibration. The purpose is to measure changes that occur in the radar cross sections of hypersonic projectiles caused by highly ionized flow fields. Under certain conditions the nose-on backscattering radar cross section of a blunt-nosed metal projectile decreases drastically when a thin, shock-produced layer of ionized gas covers the projectile. A theoretical analysis of this effect is given. Comparisons between theoretical predictions and experimental data show good correlation.