G. Becherini

Gyroscopic stabilization of launch package in induction type coilgun

The aim of this paper is to study the problem of gyroscopic stabilization of the launch package in induction type coilguns. This result can be obtained by utilizing a double-feed induction coilgun which provides rotation to the launch package while it is accelerating. Such a launcher is comprised of two coils, one generating a travelling magnetic field (and consequently the axial acceleration) the other a rotating magnetic field for the rotation of the projectile. Electromagnetic analysis, based on a cylindrical sheet current model, allows one to determine, as a function of the two slips (in the translation motion and in the rotation motion) all the electric, magnetic and mechanical quantities. Thermal and mechanical stress are determined too. Finally the results for a launcher, in which a 2 kg projectile is accelerated, are reported. For this application time dependence of the principal electromechanical quantities are shown. A comparison with the same launcher running as a linear induction launcher is developed too.

Helicoidal electromagnetic field for coilgun armature stabilization

In this paper, stabilization of an induction type coilgun inside the bore armature is considered. The projectile moves with a helicoidal motion and such a movement is obtained using a double-fed induction launcher furnished of two coils: the main one generates a traveling magnetic field providing, as a consequence, the axial motion, while the other one produces a rotating magnetic field that is responsible for the rotation. The aim of this work is to investigate the effects of the interference between the traveling and rotating magnetic fields on the in-bore armature stability.

Thermal and mechanical stress in induction coilguns

The aim of this paper is to define a procedure for the design of induction coilguns in order to obtain thermal and mechanical stress that do not exceed the allowed values in the sleeve. The magnetic vector potential is determined considering a cylindrical sheet current model both for the barrel and the sleeve and solving the related modified Bessel equation. Then the flux, the current density and the propulsive force for each section are determined. By considering the constraints due to mechanical and thermal stress, the maximum muzzle velocity for a one-section launcher is determined. Supposing that the muzzle velocities in the first and in the last section are established, and assuming that all sections, from the second to the last, work with the same mean slip and the same relative velocity, the number of sections and their length are determined. Moreover the surface current density in the barrel is calculated. The design criterion is compared with other criteria, and then used to design an 8 km/s muzzle velocity launcher.

Analysis of the Dynamic Behavior of a Linear Induction Type Catapult

The electromagnetic launcher, widely studied as electromagnetic gun, may also be used as a catapult for electromagnetic acceleration of aircrafts to replace steam catapult. These launchers can be realized utilizing a synchronous or asynchronous type of linear accelerator. In this paper, the second realization, which is the use of an asynchronous type of linear accelerator, is considered. Thus, a system consisting of a fixed part, realized with several sections and a moving part that brings the sled supporting the object to launch, is proposed. Each section contains a three-phase winding fed by different frequencies. The goal of this paper is to investigate moving part braking strategies once the mass has been launched. It is proposed that a method of electromagnetic braking can possibly allow the recovery of the kinetic energy.

Design of Multistage Linear Induction Motor used as electromagnetic catapult

In this paper the authors describe an analytical procedure for preliminary design of Multistage Linear Induction Motor (MLIM) operating as heavy mass electromagnetic catapult. Through the use of the sheet current method we derive the thermal, mechanical and electrical modeling. The implemented methodology enables to individuate and optimize the main parameters of the system and in particular the number of barrel sections. The main steps of the procedure are clearly explained and discussed throughout the paper. Finally, we show the main quantities of interest calculated for a designed prototype.

A sensitivity approach to determine the response bounds of transmission lines with random parameters

The paper deals with the problem of the analysis of transmission lines characterized by random parameters. The scope of the work is to determine lower and upper bounds to the direct and crosstalk response of a transmission line when the per unit length or the geometrical parameters are characterized by random variations. A sensitivity analysis is performed first, and then a very simple estimate of the lower and upper bounds of the voltage response is given. The accuracy of the determined bounds is shown by performing a Monte Carlo procedure over two different transmission lines.

Characterization of EM Emission During the Operation of Solid and Plasma Armature Rail Launchers

We present the results of an experimental analysis aimed at investigating the electromagnetic (EM) emission during rail launcher operation. In order to obtain such data, an experimental setup was assembled in a shielded semi-anechoic chamber, consisting of a pulsed power source-unit, a power coaxial cable and a rail launcher prototype. Several experiments were performed for different operating conditions and results were repeatable. Finally, we provide a qualitative modeling of some sources of electromagnetic transients and we discuss basic aspects driving the EM emission phenomena in railgun systems.

Electromagnetic and mechanical gyro stabilization in railgun launcher

This paper presents two new strategies to provide gyroscopic stabilization for armatures launched by railgun launchers. The rotating motion of the projectile is obtained by means of an electromagnetic field or, alternatively, of an appropriately shaped bore. In the first case windings, coiled in the bore axis direction, generate a rotating magnetic field. The interaction between the field and the conducting sleeve implies a rotation of the latter. The mechanical solution consists in a helicoidally extruded square bore launcher. In this way, the projectile moves along the main axis and it rotates at the same time. Results of a theoretical analysis are reported and the feasibility of both techniques is discussed.

Modeling and analysis of a Multistage Linear Induction Motor fed by a permanent magnet flywheel motor-generator

In the present paper the authors analyze the dynamic behavior of a Multistage Linear Induction Motor (MLIM) fed by means of a suitable back-to-back converter supplied through a flywheel energy source. The MLIM is used as a heavy mass launcher. The final velocity is several tens of m/s. Regenerative braking mode is also studied, as well as the shuttle recovering phase. The dynamic mathematical model of the whole system (flywheel-converter-MLIM) has been implemented in the Simulink® environment. Several simulations have been carried out and main results are discussed.

Design of Plasma Launcher With Gyro Stabilized Launch Mass

This paper considers the design of a plasma electromagnetic launcher aimed at determining the gyroscopic stabilization of the launch mass. The basic idea is to provide the rotation to the projectile during its acceleration inside the bore by means of a rotating magnetic field. In order to create the rotating field, a three-phase winding coil system is adopted. The design procedure of the main elements (the rails, the coil system, and the projectile) of the electromagnetic device is described in detail. The results obtained for the specific case of a launch mass of about 8 kg with outgoing velocity of 2 km/s are reported and discussed