Abstract:
A munition is provided for deploying a molten payload within a target. A plurality of holes are formed in the munition&#39;s projectile body about the circumference thereof. A seal closes off each hole. A firing mechanism is mounted in the munition&#39;s nose cone and is capable of generating energy of initiation upon deformation of the nose cone. A first burnable material is housed in the projectile body and is coupled to the firing mechanism to receive the energy of initiation. The first burnable material extends in a tree-like fashion along a plurality of connected paths in the projectile body with each of the connected paths terminating at one of the seals. A second burnable material fills the voids in the projectile body surrounding the first burnable material. The first burnable material has a lower threshold of combustion than the second burnable material while the second burnable material burns hotter than the first burnable material.

Description:
ORIGIN OF THE INVENTION 
     The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon. 
     FIELD OF THE INVENTION 
     The invention relates generally to munitions, and more particularly to a munition capable of neutralizing a target while minimizing the probability of an explosive event. 
     BACKGROUND OF THE INVENTION 
     Underwater mines are varied in their designs and mechanisms for sensing when detonation should occur. Such sensing systems include mechanical, electrical, acoustic, heat, optical, or other types of sensors. Regardless of the type of mine, underwater mine neutralization typically involves the direct placement of an explosive material on a mine or involves a projectile-delivered explosive that will impact the mine and cause an explosive event. Both of these methods have drawbacks. In terms of direct placement of a bulk explosive, underwater divers must be used to place the explosive directly on a mine. The explosive could be set off prematurely or accidentally and injure/kill the diver. Further, the diver is generally at risk just swimming amongst underwater mines. Still further, whether directly-placed or projectile-delivered, the resulting explosive event signals to an enemy that operations of some sort may be underway. This could compromise the covert nature of a mission. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a munition that can be directed/delivered to a target for the neutralization thereof without the use of an explosive event. 
     Another object of the present invention is to provide a munition that can be used to neutralize an underwater mine without endangering personnel. 
     Still another object of the present invention is to provide a munition that can be used to neutralize an underwater mine without causing the underwater mine to detonate. 
     Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings. 
     In accordance with the present invention, a munition is provided for deploying a molten payload within a target. The munition has a projectile body with a nose cone. A plurality of holes are formed in the projectile body about a circumference thereof. A seal closes off each hole. A firing mechanism is mounted in the nose cone and is capable of generating energy of initiation upon deformation of the nose cone. A first burnable material is housed in the projectile body and is coupled to the firing mechanism to receive the energy of initiation. The first burnable material extends in a tree-like fashion along a plurality of connected paths in the projectile body with each of the connected paths terminating at one of the seals. Voids are formed in the projectile body around the connected paths. A second burnable material fills the voids in the projectile body. The first burnable material has a lower threshold of combustion than the second burnable material. Upon impacting a target, deformation of the nose cone activates the firing mechanism. As a result, the energy of initiation is applied to the first burnable material which burns quickly along the connected paths and causes the failure of the seals. The heat generated by the burning of the first burnable material ignites the second burnable material which, in turn, becomes molten and flows out of the unsealed holes in the projectile body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein: 
     FIG. 1 is a cross-sectional schematic view of one embodiment of a munition that can deploy a molten pyrotechnic payload within a target in accordance with the present invention; and 
     FIG. 2 is a cross-sectional view of an embodiment of a firing mechanism that can be used in the munition of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to FIG. 1, a munition that can deploy a molten payload within a target is shown schematically and referenced generally by numeral  10 . Munition  10  can be used to neutralize (i.e., render the target inoperable) a variety of targets. For example, such targets can include underwater mines, vehicles, facilities, electronic equipment, or any other target that can be rendered useless by the deposition of a molten pyrotechnic material therein. In terms of an underwater target, munition  10  can be launched using, for example, the launcher disclosed in U.S. Pat. No. 5,686,686. 
     Munition  10  has an outer body  12  shaped like a projectile, the particular shape of which is not a limitation of the present invention. Projectile body  12  has a nose cone  14  and a casing  16  aft of and adjoining nose cone  14 . Nose cone  14  houses a firing mechanism  18  that will initiate reactions within casing  16  as will be described further below. Firing mechanism  18  can be of any suitable design that supplies an energy of initiation when munition  10  embeds itself in a target. Typically, firing mechanism  18  will be triggered upon the deformation of nose cone  14 . Since nose cone  14  will generally be made from a heavy metal (e.g., titanium, tungsten, depleted uranium, stainless steel, etc.) so that it can puncture a target upon impact therewith. The use of a heavy metal also prevents inadvertent activation of firing mechanism  18  as routine mishandling of munition  10  will not bring about sufficient deformation of nose cone  14  to initiate firing mechanism  18 . 
     A number of holes  16 A are formed about the circumference of casing  16 . While the size of holes  16 A is not a limitation of the present invention, holes  16 A typically are on the order of approximately 0.25 inches. Each of holes  16 A is sealed with a seal or plug  20  that will fail (e.g., melt, break, etc.) at the appropriate time as will be explained further below. Each seal  20  serves as a moisture seal and can be a soft meltable plastic or wax, a piece of foil or other suitable sealing material. 
     Coupled to firing mechanism  18  is a burnable material  30  that extends from firing mechanism  18  in a tree-like structure to define a plurality of connected paths. By way of example, burnable material  30  has a central trunk portion  30 A extending axially within and along the length of casing  16 . A plurality of branch portions  30 B of burnable material  30  extend radially outward from trunk portion  30 A to a hole  16 A closed off by a seal  20 . Note that not all of holes  16 A need to have a branch portion  30 A leading thereto although this will generally be the case. Branch portions  30 B need not extend perpendicularly from trunk portion  30 A, but could also be at an angle thereto. Both of trunk portion  30 A and branch portions  30 B need not define straight paths as shown, but could be curved. Still further, more than one of trunk portion  30 A could extend the length of casing  16 . 
     The spaces or voids formed about burnable material  30  within casing  16  is filled with another burnable material  40 . Relative to burnable material  30 , burnable material  40  has a higher threshold of combustion and burns at higher temperature than burnable material  30 . That is, material  30  will combust more readily than material  40  but, once ignited to its molten state, material  40  attains higher temperatures than a burning form of material  30 . 
     The interior configuration of burnable material  30  and burnable material  40  can be achieved in a variety of ways. For example, tubes  32  defining the tree-like structure of burnable material  30  can be filled and placed (or placed and filled) within casing  16 . Tubes  32  could be made from a material (e.g., cardboard, plastic, etc.) that burns or melts easily when burnable material  30  is burning. With filled tubes  32  in place, burnable material  40  can be added to casing  16  to fill up the spaces and tubes  32 . Another way to achieve the interior configuration of burnable materials  30  and  40  is to first fill casing  16  with burnable material  40 , and then bore out burnable material  40  to define the desired tree-like structure for burnable material  30 . The bored out portion of burnable material  40  is then filled with a slurry of burnable material  30 . In this construction, no tubes  32  would be required. 
     In operation, munition  10  is launched towards a target (not shown). Upon impacting the target, nose cone  14  penetrates an outer wall of the target, begins to deform, and pulls casing  16  inside the target. Since most mines today are equipped with sensor(s) that are designed to prevent detonation due a brief sudden impact (e.g., bumping by a fish or a speedboat, or impact by munition  10 ), munition  10  will typically be able to penetrate a mine without detonating it. To assure that munition  10  does not just pass through the target, casing  16  can be flared outward at some portion thereof to define a larger outer diameter. For example, in the illustrated embodiment, casing  16  flares radially outward at a step  16 B. However, it is to be understood that this is not the only construction for casing  16 . Such flaring could also occur continuously along the length of casing  16 . obviously, such flaring should not negatively impact the ballistic nature of munition  10 . 
     Deformation of nose cone  14  activates firing mechanism  18  which, in turn, supplies an energy of initiation to burnable material  30  to bring about two results. First, burnable material  30  burns quickly along its trunk portion  30 A and branch portions  30 B causing the failure (e.g., melting) of seals  20 . Second, the heat generated by the burning of burnable material  30  ignites burnable material  40  throughout casing  16 . As burnable material  40  becomes molten and pressurized due to thermal expansion, it flows out of any of holes  16 A aligned with burnable material  30 , as well as any of holes  16 A aligned with burnable material  40  whose seals  20  will fail as burnable material  40  becomes molten. 
     Material(s) selected for burnable material  40  will dictate the temperature thereof in its molten state, how the material will flow out of casing  16  in its molten state, and the choice of burnable material  30 . Several examples will be provided herein. However, it is to be understood that other material selections can be made without departing from the scope of the present invention. 
     Regardless of the type of molten flow desired, a good choice for burnable material  40  is thermite which, in general, is a mixture of aluminum and ferrous oxide. If it is desired to provide a continuous flow of (molten) burnable material  40  from casing  16 , burnable material  40  could be selected from a variety of well known thermite compounds such as thermite TH3 (66.8% aluminum/iron oxide, 29.00% barium nitrate, 2.00% sulfur and a percentage of binder). Other thermite compounds that can be used in the present invention include, but are not limited to, a thermite compound that includes a copolymer of vinylidene fluoride and hexafluoroporpylene as disclosed in U.S. Pat. No. 4,432,816, or a thermite compound that includes metallic fuels and halopolymeric binders like polytetrafluroethylene as disclosed in U.S. Pat. No. 4,349,396. 
     In other applications, it may be desirable to create a turbulent or chuffing flow of (molten) burnable material  40 . That is, (molten) burnable material  40  is forced out of holes  16 A turbulently in a jet-like fashion. To achieve this, burnable material  40  is a high-temperature burning material (e.g,. a thermite compound) with energetic or explosive material homogeneously dispersed therein. The explosive material could be in the form of powder, solid particles, or hollow particles or pellets. Suitable explosive materials include, but are not limited to, TNT including specific military compositions such as PENTOLITE, RDX including specific military composition such as various HBX compositions, and HMX including specific military compositions such as OCTOL. The explosive material can be of any shape/size as needed to increase or reduce its burning rate and/or transition from burning to deflagration and/or detonation depending on the burning temperature of the burning material (e.g., thermite compound) and cook-off temperature of the explosive material. 
     The amount of explosive material dispersed in the burning material (e.g., thermite compound) can be varied based on the type of chuffing reaction desired. In terms of burning materials selected from thermite compounds, the weight percent of explosive material used to make the burnable material  40  could be as high as 80%. The actual weight percent of explosive material depends on a variety of factors such as the choice of explosive, percentage of voids in the material mixture, pressure developed in the material as it is being loaded/packed into casing  16 , and the operation pressure and temperature of the material as it burns. 
     The choice of burnable material  30  can also be varied without departing from the scope of the present invention. By way of example, if burnable material  40  is a thermite compound, or a mixture of a thermite compound and explosive material as described above, burnable material  30  could be any well known thermite ignition mix. One such thermite ignition mix is made from the following constituent components (or suitable facsimiles as known in the art of thermite ignition mixes): 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Potassium Nitrate 
                 66.89% 
                 by weight 
               
               
                   
                 Titanium 
                 14.96% 
               
               
                   
                 Silicon 
                 7.78% 
               
               
                   
                 Aluminum 
                 8.67% 
               
               
                   
                 Binder 
                 1.70% 
               
               
                   
                   
               
             
          
         
       
     
     If it is necessary to make burnable material  30  in the form of a slurry, a variety of well established practices can be used. For example, a slurry could be made using the above-recited thermite ignition mix by adding eight percent by weight of nitrocellulose to acetone, and then mixing twenty grams of the acetone/nitrocellulose solution with fifteen grams of the above-recited thermite ignition mix. 
     As mentioned above, a variety of designs could be used for firing mechanism  18  without departing from the scope of the present. By way of example, one suitable firing mechanism  18  is illustrated in FIG. 2. A firing pin  180  is housed within a retainer housing  181  having, for example, a retaining clip  182  cooperating with a detent  183  on firing pin  180 . Clip  182 /detent  183  prevent the inadvertent activation of firing mechanism  18 . A primer  184  (such as military primer M42C2) is adjacent housing  181  and maintained within a primer and ignition holder  185 . Adjacent primer  184  within holder  185  is any igniter  186  (such as IGNITER  212  described on U.S. Navy Drawing DWG 2518212) which, in turn, is in contact with burnable material  30 . At target impact, nose cone  14  deforms and causes firing pin  180  to impact primer  184  as clip  182  fails. Note that the requirement that nose cone  14  be deformed prior to initiation of firing mechanism  18  provides for the penetration of nose cone  14  into the target prior to full activation of firing mechanism  18 . This insures that munition  10  is substantially in the target prior to the deployment of (molten) burnable material  40 . The impact of firing pin  180  on primer  184  initiates igniter  186  to start the burning of burnable material  30  along its defined paths as described above. 
     The advantages of the present invention are numerous. The munition can be used to neutralize an underwater mine or other target without any explosive event thereby increasing the chance for mission covertness. The munition can be remotely directed and launched towards its target thereby keeping personnel out of harms way. The present invention is lightweight and can be used on land or underwater. The munition can be constructed to provide a continuous flow or a chuffing flow of molten material. 
     Although the invention has been described relative to a specific embodiment thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. For example, as mentioned above, energy of initiation for igniting burnable material  30  could come from a variety of mechanisms such as percussion primers, squibs, exploding bridge wires, a shock tube, exploding foil initiators, an underwater timing fuse, etc. The choice of burnable materials  30  and  40  can be different from those described herein without departing from the novelty of the present invention. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.