Abstract:
A system is disclosed for defeating enemy missiles and rockets, particularly rocket propelled grenades (RPG&#39;s). The first step is to identify the firing of a missile by the use of sensors that give the approximate distance and bearing of the incoming missile. A non-lethal cloud of pellets is then launched from the target, which can be a building or vehicle or the like, in the general direction of the missile. The pellets are housed in a series of warhead containers mounted at locations on the target in various orientations. The warheads are triggered to fire a low velocity cloud of pellets toward the incoming missile. The pellets then collide with the missile a certain distance away from the target causing premature detonation of the missile, and/or possible severe damage to the missile, and/or deflection of the missile, due to the relatively high velocity of the missile.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Application 60/908,806, filed Mar. 29, 2007, the contents of which are incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of contract No. N00014-06-C-0040 awarded by the Office of Naval Research. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates to a system for defeating enemy missiles and rockets generally, and more particularly to a system of generating a non-lethal cloud of projectiles or pellets intended to collide with an enemy missile to cause premature detonation of the missile, and/or possible severe damage to the missile, and/or deflection of the missile, due to the relatively high velocity of the missile. 
       BACKGROUND 
       [0004]    During the times of terrorism and war, various guided and unguided missiles have been used resulting in casualties. A system that protects structures, ground/air/sea vehicles, and the people inside them against missile attack could save the lives of military troops as well as civilians. A common unguided missile currently used is the rocket-propelled-grenade (RPG). 
         [0005]    Existing technologies for RPG or missile defeat systems include application of slat armor to the military vehicles. The principle of slat armor is to stop the missile before it strikes the body of the target, to crush the missile and short circuit its electric fuze, or to cause shaped charge detonation at a standoff distance, rather than directly on the body of the vehicle. Disadvantages to slat armor are that it adds significant weight to the vehicle, and sacrifices maneuverability. Other RPG or missile defeat systems launch a single or small number of projectiles toward the incoming missile. These systems require accurate sensing of the missile trajectory, accurate aim of the projectiles in order to intercept the missile, and fast reaction time to slew and fire the projectile. 
         [0006]    Another existing strategy for RPG defeat is to deploy a commercial air bag to trap the RPG before it strikes the vehicle. Still another is to deploy a net-shaped trap made of super high strength ballistic fiber. The net is claimed to defeat the RPG by crushing its ogive and rendering the fuze inoperable. Both the airbag and the net intercept the RPG at a standoff distance of up to two meters. At this standoff distance, the RPG shaped charge jet still has significant penetrating ability. Neither of these competing technologies prevents the detonation of the RPG by its built-in self-destruct mechanism, nor do they protect nearby personnel from shrapnel from the exploding RPG. 
       SUMMARY 
       [0007]    A system is disclosed for defeating enemy missiles and rockets, particularly rocket propelled grenades (RPG&#39;s). The first step is to identify the firing of a missile by the use of sensors that give the approximate distance and bearing of the incoming missile. A non-lethal cloud of projectiles or pellets is then launched from the target, which can be a building or vehicle or the like, in the general direction of the missile. The pellets are housed in a series of warhead containers mounted at locations on the target in various orientations. The warheads are triggered to fire a low velocity cloud of pellets toward the incoming missile. The pellets then collide with the missile a certain distance away from the target causing premature detonation of the missile, and/or possible severe damage to the missile, and/or deflection of the missile, due to the relatively high velocity of the missile. 
         [0008]    In a preferred embodiment of the present disclosure, the system does not require highly accurate sensing of the incoming missile location, nor does it require slewing of a countermeasure weapon. This leads to increased potential for interception of missiles fired from very close range. The shot can be fired at non-lethal velocities, since the missile velocity will provide nearly all of the required impact energy. The present system preferably contains no high explosives or fuzes, which will lead to ease of transportability and implementation. Also, the system is preferably not lethal to people standing in the path of the shot when fired. The shot cloud system is relatively lightweight and easy to deploy. The result of the system is that the incoming missile will detonate prematurely before hitting its target and greatly reduce the resulting damage and loss of life. Appropriate density shot has also been demonstrated to limit the travel of shrapnel from the point of RPG detonation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  illustrates a typical RPG. 
           [0010]      FIG. 2  illustrates voltage output from RPG fuze due to pellet impact. 
           [0011]      FIG. 3  illustrates a RPG ogive that has been damaged by the protective system of the invention. 
           [0012]      FIG. 4A  illustrates one embodiment of a pair of warheads for implementing the system of the present invention. 
           [0013]      FIG. 4B  illustrates one embodiment of a warhead of the invention attachable to a base. 
           [0014]      FIG. 5  illustrates one embodiment of a section of a canister of the present invention. 
           [0015]      FIG. 6  illustrates one embodiment of a warhead assembly of the present invention. 
           [0016]      FIG. 7  illustrates one embodiment of electrical connections useful for operating the system of the present invention. 
           [0017]      FIG. 8  illustrates clouds of pellets surrounding a target. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    This disclosure describes the best mode or modes of practicing the invention as presently contemplated. This description is not intended to be understood in a limiting sense, but provides an example of the invention presented solely for illustrative purposes by reference to the accompanying drawings to advise one of ordinary skill in the art of the advantages and construction of the invention. In the various views of the drawings, like reference characters designate like or similar parts. 
         [0019]      FIG. 1  illustrates one embodiment of a typical rocket-propelled grenade (RPG)  100  comprising an ogive  110 , a sustainer motor  120 , stabilizer fins  130 , a rear offset fin  140  and a fuze  160 . While an RPG is illustrated, it will be appreciated that the protective system of the present invention could be employed on any incoming enemy threat such as a missile, rocket, or the like. For purposes of convenience, the enemy threat will be described simply as an RPG. 
         [0020]    The firing of the RPG  100  can be detected by various sensing means (not shown) including infrared (IR) sensors, radar and/or cameras. These sensors can be mounted on the potential target structure, which can be a vehicle or building, for determining approximate distance and bearing of the incoming RPG. Alternatively, sensors can be mounted separate from the target structure but in close proximity to the target structure if necessary. Alternatively, offsite or remote sensors could be utilized instead of, or in addition to onsite sensors, to improve the accuracy and/or tracking of the protective system of the present invention. Various sensor means could be employed as desired by the user and in accordance with appropriate field conditions. 
         [0021]    Sensors are used to trigger warhead devices (described in more detail below) mounted on a target or an adjacent location to produce a cloud or screen of projectiles or pellets (see  FIG. 8 ) intended to engage and disable an incoming RPG. More preferably, a variety of warhead devices are mounted in strategic locations relative to the target so that the target is sufficiently protected through a surrounding screen of pellets that will allow up to the entire target structure to be protected. The warhead can be any device or combination of devices that will propel shot in a manner that will produce a cloud or screen of pellets  820  (see  FIG. 8 ) distributed such that they have a significant probability of hitting an incoming RPG. 
         [0022]    In one non-limiting example, warhead containers (to be described below) with tubular cross-sections of 40 mm to 100 mm were tested, although other dimensions will be operable. The tubes were filled to various depths with projectiles or pellets, which were discharged at varying velocities. The pellets were discharged with and without the aid of a pusher plate (to be described below). The shot dispersion angle at the muzzle of the tubes was measured using a high speed camera. Results of this testing are shown in Table 1. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Dispersion Testing 
               
             
          
           
               
                   
                   
                   
                 Pusher 
                 Dispersion 
               
               
                 Tube Diameter, mm 
                 Velocity, ft/s 
                 Depth, in. 
                 Plate 
                 Angle 
               
               
                   
               
             
          
           
               
                 40 
                 60 
                 3 
                 No 
                 38° 
               
               
                 40 
                 80 
                 6 
                 No 
                 37° 
               
               
                 40 
                 60 
                 12 
                 No 
                 31° 
               
               
                 40 
                 75 
                 3 
                 Yes 
                 34° 
               
               
                 40 
                 95 
                 6 
                 Yes 
                 34° 
               
               
                 40 
                 100 
                 12 
                 Yes 
                 24° 
               
               
                 100 
                 60 
                 2 
                 No 
                 45° 
               
               
                 100 
                 90 
                 4 
                 No 
                 59° 
               
               
                 100 
                 55 
                 2 
                 Yes 
                 45° 
               
               
                 100 
                 65 
                 4 
                 Yes 
                 53° 
               
               
                   
               
             
          
         
       
     
         [0023]    Statistical calculations revealed that a dispersion angle of 30° or more resulted in a shot pattern that provides a high probability of impact with an incoming RPG. The use of a pusher plate resulted in a more even dispersion pattern, although other methods to achieve this are possible. Warhead shot containers with rectangular or elliptical cross-sections may also be used. Other cross-sectional configurations are contemplated. A wide range of organic and inorganic materials, including, but not limited to, reinforced plastic, polymeric composites, aluminum and steel, can be used for the shot containers. Other materials are contemplated. 
         [0024]    A significant amount of testing was performed, using the RPG of  FIG. 1 , to establish size, shape, and material of the shot. Pellets  150  of various materials were fired in the laboratory at inert RPG grenades with piezoelectric fuzes  160 , and fuze output voltages were measured. It was determined that suitably dimensioned pellets with a range of shapes, compositions and sizes can be used to pre-detonate the RPG.  FIG. 2  ( 200 ) shows that both steel and tungsten carbide shot, preferably greater than 0.156 inch diameter, produced sufficient fuze output voltage and generated a sufficient voltage pulse in the RPG detonation fuze to pre-detonate an RPG if the impact was on the RPG fuze. Other shot materials evaluated include reactive particles, piezoelectric particles and triboelectric particles, where in one embodiment for example, the shot material is ejected to impart an electric charge to the body of the incoming threat so that its detonator prematurely activates. These particles react on impact with the RPG to defeat it by one of the mechanisms described above. Other materials are also contemplated. 
         [0025]    As shown in  FIG. 3 , an RPG ogive  300  can be significantly damaged by impact with the pellets. Both steel and tungsten carbide pellets were found to dent or penetrate the ogive  300 , with other materials anticipated to have similar results. Pellets that penetrate the ogive can disrupt the shaped charge and reduce its lethal penetrating ability. Ogive dents and/or penetrations  310  can cause short circuiting of the electric detonation circuit (not shown) thereby causing the shaped charge not to actuate upon impact with the target. An observation during testing was that pellet impacts also have the potential for deflecting a RPG off course. 
         [0026]      FIG. 4A  illustrates a non-limiting embodiment of a pair of warhead shot containers  400  comprised of steel cylindrical tubes  410  mounted at its back ends  415  on bases  420  preferably having, as tested, an inside diameter of approximately 100 mm, a length of approximately 14 inches, and wall thickness of approximately 0.1 inches. While two containers are shown, it will be understood that only one container may be utilized, or more than two as the need or situation arises. Furthermore, while the containers are oriented in a consistent relationship, it will be understood that the other orientations are possible as long as there is no detrimental cross-fire. 
         [0027]    As shown in  FIG. 4B , a tube  410  is mounted at its back end  415  to a base  420  through the engagement of locking tabs  430  on the tube  410  with locking slots  440  on the base  420 . A wave spring  450  is further provided on the base for biased contact between the tube  410  and base  420 , while a locking pin  460  provides additional secured engagement at the junction of the tube  410  and base  420 . A contact socket  470  in the base  420  allows for passage of the actuation mechanism that activates the warhead  400 . 
         [0028]    One embodiment of a proven design of a propulsion system at the back end  415  of a warhead  400  is shown in  FIG. 5 . The warheads  400  house pellets  500  and a pusher cup or plate  510 . The pellets  500  are held in the warhead  400  preferably by a frangible or dislodgeable cover  480  ( FIGS. 4A ,  4 B) secured, for example, by a plastic ring  485 . Behind the pusher plate  510  is a cylindrical pressure chamber which will propel the pusher plate  510  and pellets  500  when sufficient pressure occurs. A high-low adapter  520  and a canister base  515  are welded to the preferably 100 mm canister  505 . A high pressure 12-gauge insert  525 , with a brass burst disk  530  in front of it, is threaded into the high-low adapter  520 . A pyrotechnic mechanism such as a 12-gauge shotgun shell  540  with a pre-wired primer is inserted into the high pressure insert  525 . A threaded rod  550 , with a large axial hole  552  at the back and a small axial hole  554  at the front, is screwed into the high pressure insert  525  behind the shotgun shell  540 . Primer wires  560  are threaded through the axial holes  552 ,  554  and attach to the shot gun shell  540 . A grooved rubber plug  565  is inserted into the large axial hole  552 , with the wires  560  in the groove. The wires  560  are threaded through the hole  570  in the threaded cap  575 , which is then screwed onto the threaded rod  550 . When electronically triggered, the propellant will ignite and will launch the pusher cup  510  and shot  500 . This propulsion system was employed and performed successfully during live RPG testing. Other propulsion systems are possible, such as sheet explosives, which have the potential for warhead size and weight reduction. 
         [0029]    Another embodiment of the proven design of a propulsion system useful in the present invention is shown in the warhead tube  600  of  FIG. 6 . A cartridge holder  610  and an O-ring seal  615  are bolted, with lock washers, on the inside of the warhead tube  600 . A pusher plate  620  and pellets (not shown) are then placed in the tube  600  and held there by a frangible cap  625 , secured to the tube  600  by a steel washer  630  and cap screws  635 . A 20 mm cartridge  640  with an electric primer  645  and containing propellant (not shown) is inserted into the cartridge holder  610  at the back of the warhead and a metal contact bar  650 , rubber washers  655 , a plastic insulating sleeve  660 , an O-ring  670  and a support plate  675  are attached. The metal contact bar  655  contacts the center of the primer in the cartridge  640 . Rubber and plastic components insulate the contact bar  650  from the rest of the assembled warhead tube  600 . 
         [0030]    Another embodiment of a propulsion system useful in the present invention involves using a pneumatic assembly at the back of the warhead tube  600  comprising a pressurized cartridge and a fast acting release valve, wherein such propulsion system utilizes compressed air to propel the pellets. 
         [0031]    In accordance with one embodiment of the present invention, two warheads  700  (only one being shown; see  FIG. 4A  that shows two) are then inserted into breech blocks  710  with electrical contacts as shown in  FIG. 7 . Specifically, the metal contact bar  720  on the warhead  700  contacts the positive electronic firing pin  725  in the breech block  710 . The metal support ring  730  on the warhead  700  contacts the negative firing pin  735 . When electronically triggered, the propellant will ignite and will launch the pusher cup and pellets. 
         [0032]    In a preferred, non-limiting embodiment, for the RPG ogive identified in  FIG. 3 , for example, each warhead is filled with pellets made of tungsten carbide having a diameter of approximately 0.215 inches, a density of approximately 14.9 g/cm 3 , and a Rockwell C hardness of approximately 75. This configuration results in approximately 15,000 pellets housed in each warhead. Other shot configurations are contemplated. When triggered, the pellets are ejected from the two warheads in a non-directed manner and typically radiate as clouds with expanding circular cross-sections that progressively overlap. The pellets leave the warheads at speeds between 50 ft/s and 150 ft/s, and more preferably at speeds that are non-lethal to nearby personnel. In this example implementation, the pellets will have a dispersion angle of approximately 40 degrees radiating from each warhead tube, and an overall dispersion angle from a pair of warhead tubes of approximately 60 degrees. This configuration using a large number of pellets will result in a high probability of encountering the piezoelectric device on the nose of the missile, and thereby causing premature detonation of the missile. This was confirmed by testing one described typical embodiment system against several separate live RPGs fired from an RPG launcher. The RPGs that entered the protected area of the screen all detonated upon impact with the pellets. 
         [0033]    As shown in  FIG. 8 , a series of warheads  800  can be mounted on a vehicle  810  and can protect the vehicle  810  from missile attack. Any structure can be provided with complete coverage by proper placement and orientation of a series of warhead tubes. In the typical embodiment, the shot screen  820  is fired in order to strike the missile 10 to 20 feet from the target vehicle or building. Once the sensor  830  detects that a missile has been fired, the speed and approximate trajectory of the missile must also be determined by measurement, typically supported by rapid calculation. Calculations are made to determine if, when and approximately where the missile will strike the vehicle or building, therefore determining which warhead tubes must be fired, and when they need to be fired. This will require a distributed or central processing unit (not shown) that is capable of collecting data from the sensors and making the appropriate calculations. It should be noted that, in the preferred embodiment, the warhead tubes are mounted statically and are not slewed. The result is an automatic system capable of defeating multiple missiles and thereby protecting vehicles, buildings, and people. 
         [0034]    The shot is preferably fired at non-lethal velocities, since the missile velocity will provide nearly all of the required impact energy. The present system preferably contains no high explosives or fuzes, which will lead to ease of transportability and implementation. Also, the system is preferably not lethal to people standing in the path of the shot when fired. The shot cloud system is relatively lightweight and easy to deploy. The result of the system is that the incoming missile will detonate prematurely before hitting its target and greatly reduce the resulting damage and loss of life. 
         [0035]    While the present invention has been described at some length and with some particularity with respect to the several described embodiments, it is not intended that it should be limited to any such particulars or embodiments or any particular embodiment, but it is to be construed with references to the appended claims so as to provide the broadest possible interpretation of such claims in view of the prior art and, therefore, to effectively encompass the intended scope of the invention. Furthermore, the foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.