Spin Stabilization of Projectiles Accelerated by Electromagnetic Force

Abstract

An electromagnetic accelerator device which is configured to impart spin to projectiles fired from it. Various methods to accomplish this stabilization are proposed. The spin may be imparted physically using friction, inductively using an alternating magnetic field or inducing eddy currents in an armature, or by shaping the magnetic field or armature within the barrel of the device appropriately. The magnetic field(s) within such a device may be configured to impart a linear, as well as a rotational force, upon an armature which may be non-circular in cross-sectional profile, or non-axisymmetric in physical shape or material properties.

1 . An apparatus comprising:
 a) one or more of an electromagnetic coil which may impart a linear accelerating force and/or a rotational torque onto an armature by means of an electromagnetic field; and   b) a force, or a superposition of forces, is exerted upon the armature differentially depending upon its material properties, and/or its position within the electromagnetic field generated by the apparatus; and   c) at the armature, a torque is exerted as a result of a non-axisymmetric quality of said magnetic field in at least one portion of the apparatus for at least some portion of the time which said armature spends within said apparatus; and   d) an external surface of said armature which lacks helical groove or helical rib features.   
     
     
         2 . The apparatus of  claim 1 , wherein the armature is non-axisymmetric in its physical shape, material properties, electrical properties, or magnetic properties; and/or the electromagnetic field generated by the electromagnetic coil is essentially non-axisymmetric in intensity. 
     
     
         3 . The apparatus of  claim 1 , wherein the apparatus in its entirety weighs less than 100 lbs. 
     
     
         4 . The apparatus of  claim 1 , wherein the armature lacks aerodynamic fins or spiral groove features. 
     
     
         5 . The apparatus of  claim 1 , wherein the magnetic field is generated by three or more coils. 
     
     
         6 . The apparatus of  claim 1 , wherein the armature is constructed primarily from a ferromagnetic material. 
     
     
         7 . The apparatus of  claim 1 , wherein the armature is constructed primarily from an electrically conductive material within which a transitory electrical current is induced while the armature is within the apparatus, and said electrical current creates a magnetic field which interacts with the electromagnetic field generated by the apparatus. 
     
     
         8 . The apparatus of  claim 1 , wherein the electromagnetic coil surrounds a barrel fashioned from non-magnetic material, and within said barrel there exists an internal bore through which the armature may pass, and when the armature is positioned within said internal bore, the cross section of the internal bore consists of less than 90% by area of a material which interacts with the electromagnetic field of the apparatus. 
     
     
         9 . The apparatus of  claim 1 , wherein a cross section of the armature does not substantially change in shape along an axis parallel to its linear acceleration. 
     
     
         10 . The apparatus of  claim 1 , wherein the electromagnetic coil(s) are switched on or off by a control system in response to the armature's angular position. 
     
     
         11 . The armature of  claim 6 , wherein the ferromagnetic material is selected from the group consisting of: Permendur KF49, Permendur 2V, ferrite, iron, steel, or steel alloys. 
     
     
         12 . The control system of  claim 10 , wherein the angular position of the armature is provided by electrical, optical, mechanical, radio frequency, or magnetic signals generated by the armature as it passes through a barrel of the apparatus. 
     
     
         13 . A system comprising a linear electromagnetic motor which imparts a linear force upon a non-captive projectile; and during or after such linear acceleration, the system also imparts a rotational force upon said projectile through the use of electromagnetic, electrostatic, mechanical, or other means; and the projectile leaves the system rotating on one axis. 
     
     
         14 . The system of  claim 13 , wherein the projectile exits the system rotating about an axis that is parallel to its direction of travel. 
     
     
         15 . The system of  claim 13 , wherein the projectile exits the system rotating about an axis that is perpendicular to its direction of travel. 
     
     
         16 . The system of  claim 13 , wherein the control system may be configured to engage a series of external electromagnetic coils in a pre-programmed timed sequence, or in response to feedback from optical, mechanical, radio frequency, or magnetic signals generated by the armature, to create a superposition of fields which acts to impart a rotational torque upon said armature. 
     
     
         17 . The system of  claim 13 , wherein the system imparts a rate of rotation upon the projectile greater than one rotation per three feet of the projectile's linear travel. 
     
     
         18 . A means for imparting spin upon a non-captive armature accelerated by electromagnetic force.