Abstract:
A munition and method capable of producing real-time selectable effects ranging from unrestricted to low collateral damage. The munition is capable of a directionally focused fragment pattern and limited lethality/damage effects.

Description:
[0001]    This invention was made with Government support under FA8651-07-C-0153 awarded by the United States Air Force and Government support under W911QX-10-C-0019 awarded by the United States Army. The Government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The current invention relates to the field of munitions capable of directionally focused fragmentation. 
       BACKGROUND OF THE INVENTION 
       [0003]    Munitions are typically designed for the specific purpose of creating the maximum lethality or destruction for a given munition volume or weight. Typical munitions utilize a metal case containing explosive material. Detonation of the explosive material fragments the case into high velocity shrapnel that damages or obliterates the target(s). These types of munitions are highly indiscriminant in that they will produce substantial damage within a large lethality radius. Such design has been beneficial in conventional force-on-force warfare where collateral damage is of minimal concern. 
         [0004]    Current warfare is frequently conducted by small groups of combatants in areas that may be highly populated with non-combatants, or with remotely fired missiles targeting a specific target located in or near a populous area. In such situations, traditional munitions can produce undesirable collateral damage to personnel and property. In recent years, effort has been placed on creating selectable effects munitions for attacking a target with little or no resultant collateral damage. 
         [0005]    Guirguis (U.S. Pat. No. 7,347,906 B1) describes an on-demand variable yield munition that permits the selection of low, high, or intermediate collateral damage. Such munitions could decrease collateral damage in war zones, but the Guirguis munition&#39;s blast footprint is limited to a radial area surrounding the munition; it offers no forward-focused lethality option. Guirguis also fails to describe or claim the desirable feature of post-launch lethality selection. Thus Guirguis does not satisfy the need for real-time selectable effects munitions that offer the post-deployment choice of generalized outputs that can range from blast only to blast plus fragments to a prescribed fragment footprint including a forward-focused lethality area. 
         [0006]    The inventors herein describe and claim a device and method that satisfies the need for on-demand, selectable effects, multi-mode munitions that can be adapted in real time to address and respond to evolving circumstances on the battlefield. The present invention was described in a 2010 symposium paper, incorporated herein by reference. Dennis Wilson, John Granier, Christopher Vineski, and Donald Littrell, “Development of a Small Selectable Mode Warhead,” 12th Joint Classified Bombs/Warheads &amp; Ballistics Symposium, Monterey, Calif., 23-26 Aug. 2010. The present invention is an apparatus and method that accommodates the constantly changing circumstances of current warfare and provides options from which the user can in real time select the type, magnitude, and direction of the explosive force that a munition will deliver to a target. The present invention gives the user the ability to select the characteristics of a munition as it is in transit to the target. 
         [0007]    The preferred embodiment of the present invention apparatus is a real-time selectable effects, multi-mode munition that is appropriate for both unrestricted and low collateral damage scenarios. The selectability provides several benefits over state of the art munitions. One benefit is enhanced mission flexibility. For example, aircraft-delivered, real-time selectable effects, multi-mode munitions eliminate time-consuming and costly returns to the air base for proper weapon load-out in the event of post-takeoff changes in target intelligence. Another benefit is streamlined logistics. Real-time selectable effects, multi-mode munitions can decrease the number of unique munitions required to engage diverse target scenarios. Most importantly, real-time selectable effects, multi-mode munitions provide discriminating lethality against a broad target set, thus minimizing collateral personnel damage and costly post-conflict infrastructure reconstruction. 
         [0008]    Guirguis uses two conventional organic explosives that have well defined detonation velocities that effectively establish the respective power outputs. The conventional explosives have fixed energies of detonation and heats of combustion that combine to set the total effective energy output. The selectable effects achieved by the present invention are based on its use of a modified high-energy density explosive that releases its energy via variable speed self-oxidized combustion (SOC). The SOC reaction rate is determined by the shock impetus strength. Because the rate and extent of an SOC reaction depend on the initiation stimulus, the reaction is shock dependent and can be overdriven. Aluminized perfluoropolyether modified explosives are attractive for selectable effects applications because the combustion wave speed, and thus the energy release rate or power, can be controlled through novel initiation techniques. The modified explosive enables the present invention&#39;s novel option of selectable fragmentation, i.e., isotropic or anisotropic fragment projection as opposed to the strictly spherical fragmentation of state of the art munitions. 
       SUMMARY OF THE INVENTION 
       [0009]    The following terms in this application and any continuation applications based thereon shall be construed using the corresponding inventor-supplied definitions. 
         [0010]    “Case” shall mean an enclosure of any geometry such as, but not limited to, a casing. 
         [0011]    “Explosive” shall mean a material capable of releasing energy at detonation time scales. 
         [0012]    “Modified explosive” shall mean any material capable of fast energy release by means of a multi-molecular diffusion reaction as opposed to the typical single molecule reaction such as a C-H-N-O explosive. 
         [0013]    “Fragment” shall mean a piece detached from a whole, including, but not limited to, fractured metal casing, pieces of a pre-formed geometric array, and metal particulates. 
         [0014]    “Reactive metal and oxidizer” shall mean materials that when combined and provided the appropriate initiation energy produce a combustion reaction. 
         [0015]    “Selectable effects” shall mean output or results that can be chosen by a user. 
         [0016]    “Variable yield” shall mean the result achieved by tuning the total energy or power output from a munition. 
         [0017]    In the apparatus preferred embodiment, the real-time selectable effects multi-mode munition contains an outer case enclosing at least two types of explosives. One end of the case has a fragmentable end cap while the other end has at least two detonators designed to selectively detonate the two different explosives. 
         [0018]    In another embodiment, the munition case contains at least two explosives. Each end of the munition contains a detonator designed to selectively detonate one of the explosives. 
         [0019]    In another embodiment, at least one of the explosives is a reactive metal and oxidizer combination. 
         [0020]    In yet another embodiment, the method of selectively detonating the real-time selectable effects multi-mode munition is based on user input. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a section view of a cylindrical assembly illustrating one embodiment of the current invention. 
           [0022]      FIG. 2  shows an end view of a focused fragment array end cap. 
           [0023]      FIG. 3  shows a section view of a cylindrical assembly illustrating a second embodiment of the current invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    As shown in  FIG. 1 , the preferred embodiment of the current invention apparatus has a case  100  that has a preformed focused fragment end cap  200  on one end and a detonator housing  140  on the other end. The detonator housing  140  is secured to the case  100  with the threaded retaining ring  120 , but could also be integral with the case. The detonator housing  140  contains the first detonator  510 . The case  100  also contains a shock attenuating detonator housing  160  and a second detonator  520 . The shock attenuating detonator housing  160  significantly reduces the transmitted shock pressure. It is comprised of a homogeneous, low density, highly compressible material, but can also be comprised of a heterogeneous, highly dissipative material such as soft granular particles. Shock attenuating detonator housing porosities can range from 10% to 50%. Examples include, but are not limited to, polymers such as polyethylene and polystyrene, and epoxy containing hollow micro-spheres. 
         [0025]    The case  100  also contains explosives  300  and  400  such that explosive  300  is directly initiated by detonator  510 , and explosive  400  is initiated by detonator  520 . Booster explosive  515  facilitates initiation of explosive  300 . Explosive  300  forms an outer cylinder in contact with the case  100  and surrounds the inner core of explosive  400 . Explosive  400  is generally cylindrical in form and is in contact with the focused fragment end cap  200  that is attached to the case  100 . The end cap can be retained by an adhesive or a mechanical feature such as, but not limited to, machine threads. 
         [0026]    Pressure generated by detonation of explosive  300  causes the case  100  to fragment into many small fragments moving outward with high velocity. One skilled in the art can recognize that this can be accomplished by fabricating case  100  from various metals including, but not limited to, low and high carbon alloy steel, powder metals, and cast metals. The case  100  may be designed to break up into predetermined fragment sizes. 
         [0027]    However, the pressure generated by the reaction of explosive  400  is not sufficient by itself to shatter the case  100  into small, high-velocity fragments. The case  100  is designed to contain the pressure so that the focused fragment end cap  200  ruptures into high velocity fragments projected away from the munition in a direction substantially co-linear with the munition&#39;s longitudinal axis.  FIG. 2  shows the end view of the focused fragment end cap  200 . In the preferred embodiment, the focused fragment end cap  200  is constructed from multiple hexagonal tungsten segments  820  held together by a low-strength encapsulating matrix to form a circular disk or other suitable shape. The low-strength encapsulating matrix can be, but is not limited to, thermoset epoxies, thermoplastics, sintered metals, and polymer/metal powder mixtures. The fragmenting end cap can be an array of other nesting shapes and sizes such as, but not limited to, millimeter size spheres, cubes, or cones. While tungsten is the preferred material, other materials such as, but not limited to, steel and tantalum can be used. Alternatively, the focused fragment end cap  200  may be constructed from a single piece of metal or ceramic scored to break apart into segments of predetermined shape and size. 
         [0028]    In yet another embodiment, the focused fragment end cap  200  is made from a combination of tungsten powder and polymeric matrix or other suitable binder. A density in the range of 8 to 16 g/cc is used in the preferred embodiment, although one skilled in the art will recognize that other densities can be used. In this embodiment the end cap ruptures and many fine particles are blasted away from the munition in a direction substantially co-linear with the munition&#39;s longitudinal axis. While tungsten is the preferred material, other materials including, but not limited to, tantalum or mixtures of high-density metals can be used. 
         [0029]    In the preferred embodiment, the first explosive  300  is an explosive such as, but not limited to, C-4, H6, RDX, or HMX. The second explosive  400  is a modified explosive such as, but not limited to, a mixture of combustible metals and oxidizers with or without a low concentration of HMX or RDX. A critical requirement of the modified explosive  400  is that it not cause a detonation of explosive  300 . 
         [0030]    In operation the invention is initiated in various modes. In one mode of operation, the first detonator  510  is activated, thus initiating the first explosive  300 . This in turn initiates the second explosive  400 . This mode results in both explosives being detonated, and the case  100  and focused fragment end cap  200  breaking into many small fragments projecting in many different directions with a result similar to that of traditional munitions. 
         [0031]    In a second mode of operation, the second detonator  520  is activated, thus initiating the second explosive  400 . The reaction is not sufficient to cause the first explosive  300  to detonate; however, it does cause the explosive  300  to deflagrate. The case  100  is designed to contain the resultant pressure so that the focused fragment end cap  200  ruptures into high velocity fragments moving away from the munition in a direction substantially co-linear with the munition&#39;s longitudinal axis. 
         [0032]    In a third mode of operation, both detonators  520  and  510  are activated either simultaneously or with a delay specified by the user. This mode produces blast and fragmentation characteristics unique from the two modes previously described. One skilled in the art will appreciate that there are numerous means of creating a time delay between the two initiators, including, but not limited to, electronic, mechanical, and pyrotechnic means. 
         [0033]    An embodiment of the current invention was fabricated utilizing a case  100  made from AISI 4140 steel with an inside diameter of 1.5 in., length of 3.5 in., and a wall thickness of 0.300 in. In another embodiment low carbon alloy 1018 steel was used. The first explosive  300  was approximately 100 g of PETN sheet explosive, and the second explosive  400  was approximately 200 g of aluminum and perfluoropolyether. The focused fragment end cap  200  utilized 48 hexagonal tungsten pellets epoxied together. The first detonator  510  was a standard RP-502 product, and the second detonator  520  was a standard RP-87 product with a 1 g PBXN-5 booster pellet. While the current invention utilized the above-mentioned dimensions, one skilled in the art could scale the invention up or down. One skilled in the art will also recognize that the detonators and explosives can be selected from a large population for customizable results. 
         [0034]    In an alternative embodiment depicted in  FIG. 3 , the case  100  contains explosive  300  and explosive  400 . Both ends of the housing have a focused fragment end cap ( 210  and  220 ). The focused fragment end cap  210  contains a first detonator  520 , and the focused fragment end cap  220  contains a second detonator  510 . The explosive  300  can be directly initiated by the detonator  510 , and the explosive  400  can be directly initiated by the detonator  520 . Booster explosive  525  facilitates initiation of explosive  400 . End caps  210  and  220  are metal/polymeric matrices intended to shatter when impinged by low pressure input. End caps  210  and  220  can also be made of monolithic materials such as, but not limited to, steel and tungsten. 
         [0035]    Explosive  300  lines the inside of the case  100  and is in contact with the detonator  510 . 
         [0036]    Explosive  400  is partially contained within the explosive  300  and is in contact with the detonator  520 . A portion of explosive  400  is in contact with the inside of the case  100  near the focused fragment end cap  210 . This configuration allows explosive  400  to be initiated resulting in a fast SOC reaction and deflagration of explosive  300 . 
         [0037]    An unrestricted collateral damage output can be achieved by activating detonator  510 , detonating explosive  300 . Similarly, both detonators  510  and  520  can be activated simultaneously. Either method will fracture the case  100 , producing small, high velocity fragments and a reaction of explosive  400 . 
         [0038]    For limited or low collateral damage, detonator  520  is activated alone. This initiation mode results in a controlled SOC reaction of explosive  400  and simultaneous deflagration of explosive  300 . The resulting high pressure ruptures the end caps  210  and  220  producing a dense metal cloud. The resulting multi-phase blast creates a small lethality radius. End caps  210  and  220  can be designed to produce fragments ranging from micron to millimeter size. The metal cloud fragments can be, but are not limited to, tungsten and tantalum. The case  100  either remains intact or separates into several large, low velocity fragments having a limited lethality radius. 
         [0039]    Initiation of detonators  510  and  520  in various timed sequences produces a variety of blast and fragmentation characteristics intermediate to the output modes previously described. 
         [0040]    The present invention includes a method for using the present invention apparatus for achieving a desired blast result. The munition as described herein is delivered to a desired target via aircraft, ships, wheeled or track vehicles, dismounted troops, or a combination of those and other means. During delivery, target environment data are analyzed for determination of the desired output mode. If maximum damage with unrestricted collateral damage is required, the detonator  510  or both detonators  510  and  520  is/are armed upon launch and activated when the munition is near the target. If, during the mission, intelligence dictates a change from unrestricted to limited collateral damage, only the detonator  520  is armed and activated. If an alternative result is desired, a real-time command specifies the time delay between the two detonations. The detonator real-time selection, arming, timing, and activation can be achieved with commonly understood wireless or wired signal technology.