Abstract:
A device for controlling one or more of the flight parameters of a projectile: speed, spin, pitch and yaw. The invention discloses a novel approach to controlling these parameters by rotating or extruding a surface out from the body of the projectile in a plane normal to the length of the projectile. The specific shape, thickness, and degree of surface exposure would be determined by the specific application and aerodynamic analysis.

Description:
DEDICATORY CLAUSE  
       [0001] The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to us of any royalties thereon. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    Projectiles are utilized in many fields for many purposes. While such purposes may be as diverse as games, scientific experiments, blowguns, and even vehicles, the most common use is probably as weapons of war. The shapes of such projectiles are as varied as their purposes. Frequently, the projectile will have an elongated body with designated fore and aft ends. While there are clearly many exceptions to this general shape, a boomerang being one, the focus of this invention is on a device for controlling the flight of an elongated-shaped projectile. Such projectiles may travel at subsonic, transonic, and supersonic speeds.  
           [0004]    Prior art is replete with methods for controlling the various flight parameters (e.g., speed, spin, pitch and yaw) of such projectiles. Some examples include: pulse motors, variety of nozzle arrangements, aerodynamic shaping of the body of the projectile, and fixed and moveable fins (or other protrusions from the body of the projectile). These devices may be utilized at various locations upon the projectile. The prior art references below contain a more detailed discussion of these prior control methods.  
           [0005]    For weapons of war, accurate control of a projectile has several advantages. It increases the likelihood of hitting the target and, thereby, reduces the number of projectiles required to accomplish the objective. This efficient use of projectiles can result in a more effective combat engagement when quantities of projectiles are limited and a cost savings by reducing the number of projectiles used for a given mission. A quick and accurate engagement of the target also may be beneficial, if not essential, for the survivability of the system or individual firing the projectile. The existence of a highly accurate and effective projectile also may have a psychological impact upon the enemy.  
           [0006]    2. Description of Prior Art  
           [0007]    In U.S. Pat. No. 5,398,887 issued Mar. 21, 1995, a control system for use in missiles and other projectiles is disclosed. The system controls pitch, yaw, and roll by means of two opposing pairs of flaps configured in the aft end. The flaps initially conform to the exterior surface of the projectile, and when actuated each flap rotates about its leading edge. This invention does not directly address any adjustments to the speed of the projectile.  
           [0008]    In U.S. Pat. No. 6,123,289 issued Sep. 26, 2000, an aft section for attachment to a projectile is disclosed. The primarily purposes are to reduce the speed of the projectile and to produce a stabilizing lift force during forward flight. The aft section includes a conically shaped flared section and a flange.  
           [0009]    In U.S. Pat. No. 6,135,387 issued Oct. 24, 2000, a projectile guidance control system is disclosed. This system includes several foldout fins in the aft section and a plurality of rotating fins mounted pivotally in the fore section of the projectile.  
           [0010]    Objective.  
           [0011]    The invention discloses a simple and effective device for controlling one or more of the flight parameters of a projectile: the speed, spin, pitch and yaw. The simplest application requires only the inherent spin of the projectile to actuate a preset control feature.  
         SUMMARY OF THE INVENTION  
         [0012]    The flight parameters of a projectile include speed, spin, pitch and yaw. This invention discloses a novel approach to controlling these parameters by rotating or extruding a surface out from the body of the projectile in a plane normal to the length of the projectile. The specific shape, thickness, and degree of surface exposure would be determined by the specific application and aerodynamic analysis. 
       
    
    
     DESCRIPTION OF THE DRAWING  
       [0013]    [0013]FIG. 1 shows the preferred embodiment location of the device for a typical projectile.  
         [0014]    [0014]FIG. 2 shows the single-rotating surface version of the device.  
         [0015]    [0015]FIG. 3 shows a two-rotating-surfaces version of the device.  
         [0016]    [0016]FIG. 4 shows a four-rotating-surfaces version of the device.  
         [0017]    [0017]FIG. 5 shows a four-extruding-surfaces version of the device.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Referring now to the drawing wherein like numbers represent like parts in each of the several figures, FIG. 1 shows a typical projectile  2  where the longer axis is generally in the direction of flight. For obvious reasons the projectiles normally are aerodynamically designed to minimize the resistance or drag effects of the medium through which such projectiles might travel. Such projectiles may or may not have an initial spin direction or may change spin direction during flight. These projectiles may be subsonic, transonic, or supersonic. In the preferred embodiment a housing unit  4  is positioned at the aft end of the projectile. This location of the housing unit  4  was chosen for the preferred embodiment and is not a limitation upon the claims. The housing unit  4  conforms to the body of the projectile. It may be built in during production of the projectile or attached to an existing projectile by means known to those skilled in the art. The means for attaching the housing unit  4  also may be built in during production.  
         [0019]    [0019]FIG. 2.A. shows a single surface  6  in the stowed position. FIG. 2.B. shows the single surface  6  in a rotated position. The rotation is in the plane that lies normal to the length of the projectile. The rotation is to a position outside of the housing unit  4  and, therefore, outside of the body of the projectile. This rotating version of the device is primarily designed for projectiles having a high rate of spin in a single direction during flight. The means for rotating the single surface  6  is the spin of the projectile during flight. To effect this rotation the surface is attached to the housing unit  4  such that the surface rotates in a direction opposite the spin of the projectile  2 . Where the rotation is effected by the spin of the projectile, such spin must be consistent in one direction, and that direction must be known when integrating the device with the projectile. Alternatively, in a rotating version of the device the surface may be actuated by means other than the spin of the projectile. In such alternative embodiments having the surface attached for rotation in a direction opposite the spin of the projectile is desirable but not required. Such alternatives may be employed on projectiles with no spin. In FIGS. 2, 3, and  4  a point of rotation  28  is shown without implying any specific means for rotation.  
         [0020]    Available options to address using a single device with projectiles having different directions of spin would include: the device may be designed so that it may be attached to a projectile in two different configurations (This would allow the rotation of the surface to be opposite the known spin direction for that projectile.); the number of surfaces could be doubled with each pair of surfaces rotating in an opposite direction and actuated by only an opposite spin of the projectile; or the device itself might be produced in two different configurations.  
         [0021]    In this first embodiment as well as those following, the surface shape, thickness, and degree of rotation or extrusion will be functions of the desired application and aerodynamic analysis. The surface may be rotated or extruded to a single position, a plurality of positions, or a continuum of positions between stowed and fully extended. The rotation or extrusion may be for a very short duration (i.e., bang-bang actuation) or for a longer duration (to include the completion of the flight). A variety of components known to those skilled in the art may be used to accomplish the rotation or extrusion and the desired degree of control over rotation or extrusion. Some options include electronic actuators, mechanical actuators, springs, and air flow though selected paths within the device. The methods of rotation or extrusion and the method for control chosen for these embodiments are not a limitation upon the claims. The location of the housing unit at the aft end of the projectile represents the preferred embodiment and does not limit the claims. The claims do not specify a predetermined location.  
         [0022]    Slower spin rates for a projectile will make an increased number of surfaces more desirable. The additional surfaces will accommodate the slower revolution frequency and impart the appropriate control authority in the desired manner. FIG. 3.A. shows two surfaces  8  and  10  in the stowed position. FIG. 3.B. shows these surfaces  8  and  10  in a rotated position. The surfaces  8  and  10  are attached to the housing unit  4  to allow for rotation in a direction opposite the spin of the projectile.  
         [0023]    [0023]FIG. 4.A. shows four surfaces  12 ,  14 ,  16  and  18  in the stowed position. FIG. 4.B. shows these surfaces  12 ,  14 ,  16  and  18  in a rotated position. The surfaces  12 ,  14 ,  16  and  18  are attached to the housing unit  4  to allow for rotation in a direction opposite the spin of the projectile.  
         [0024]    As an alternative embodiment the surface may be extruded radially from the housing unit. FIG. 5.A. shows four surfaces  20 ,  22 ,  24 , and  26  in a stowed position. FIG. 5.B. shows one of the four surfaces  22  in an extruded position. The number of surfaces in this embodiment is not a limitation upon the claims. Centrifugal force may be used to extrude the surface with another means employed for returning the surface to a stowed position.  
         [0025]    Other embodiments may include a means for adjusting the shape of the surface and for altering the position of the surface outside a plane normal to the length of the projectile. The selection of these optional means will be based upon the desired application and aerodynamic analysis.  
         [0026]    Although several embodiments of the device have been illustrated, it is apparent that various modifications and other embodiments of the device may be made by those skilled in the art without departing from the scope and spirit of the foregoing disclosure. Accordingly, the scope of the Device for Projectile Control should be limited only by the claims appended hereto.