Patent Publication Number: US-6668727-B1

Title: Explosively driven impactor grenade

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor. 
     BACKGROUND OF THE INVENTION 
     The invention relates in general to grenade type munitions and in particular to a grenade type munition comprising Explosively Driven Impactors (EDIs). 
     A need exists for a biological and chemical agent defeat warhead. The warhead would enable the attack of chemical and biological agents located within semi-hardened or hardened storage and manufacturing facilities. The warhead would be delivered by a precision air, ship or submarine weapon system, with minimum collateral damage to the surrounding area. To destroy biological and chemical agents, the agents must first be released from their containers. The EDI grenades are designed to rupture containers to release the chemical and/or biological agent contents with minimal collateral damage due to low overpressure from the grenades. Once the agents are released, the Agent Defeat High Temperature Thermal Radiator (HTTR) payload will destroy the agents. The EDI grenade can also be used by individual soldiers as a hand grenade. 
     The EDI grenades for agent defeat application are thermally fuzed to operate when a pre-determined room temperature is reached. The thermal fuzing is required for agent defeat application because to minimize collateral damage, the room temperature needs to be high enough to create a lethal environment for biological agents before the agent containers are ruptured. The EDI grenades can be alternatively fuzed for other applications such as for anti-personnel. Other fuzing methods for an EDI grenade include time delay, pressure sensing and impact fuzing. 
     If existing grenades such as the M67, M61 or MK3A2 were used for agent defeat application, the collateral damage would be much higher due to its greater over-pressure characteristic. These hand grenades do not have the penetration capability of an EDI grenade. 
    
    
     The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals. 
     FIG. 1 is a perspective view of a one embodiment of a grenade body. 
     FIG. 2 is a perspective view of a second embodiment of a grenade body. 
     FIG. 3A schematically shows a fuze and FIG. 3B shows a fuze cap. 
     FIG. 4 is a side view of an explosively driven impactor. 
     FIG. 4A is a sectional view of a cup for housing an explosively driven impactor. 
     FIG. 5 shows a retaining ring. 
     FIG. 5A shows a gasket. 
     FIG. 6 schematically shows a fuze and a booster charge. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The purpose of the Explosively Driven Impactors (EDI) grenade is to cause damage to equipment, storage containers, and personnel. In one scenario, the EDI grenade ruptures containers filled with biological or chemical agents with minimal collateral damage effects due to its low overall overpressure output. The EDI grenade is unique because of the use of EDIs. This application of EDI technology inflicts multi-directional damage, possesses greater penetration capability than existing hand grenades and eliminates the need for a self-righting mechanism. 
     The EDI grenade includes a grenade body having a substantially spherical shape. For the purposes of this patent, a substantially spherical shape includes spherical, flattened spherical and geodesic shapes. The importance of the substantially spherical shape of the grenade body is that it allows the EDI grenade to be multi-directional no matter how it finally comes to rest. In this regard, a self-righting mechanism is not required. For example, in agent defeat applications, the EDI grenade can affect storage containers regardless if it lands next to or on top of a container and regardless of its landing orientation. The grenade body material may be metallic (steel, aluminum, etc.) or plastic. The diameter of the grenade body may vary from, for example, two inches to thirty-six inches. 
     FIG. 1 is a perspective view of a one embodiment of a grenade body  10 . Grenade body  10  has a geodesic shape. Grenade body  10  includes a hollow central portion  12  for receiving a fuze. The exterior surface of the body  10  includes a plurality of recesses  14  formed thereon for receiving the EDIs. Each recess  14  includes an opening  16  into the hollow central portion  12  of the grenade body  10  to allow deflagration cord to connect the EDIs with the fuze. The grenade body  10  also includes an opening  18  on the exterior surface for insertion of the fuze. The opening  18  connects with the hollow central portion  12   
     FIG. 2 is a perspective view of a second embodiment of a grenade body  20 . Grenade body  20  has a flattened spherical shape. Grenade body  20  includes a hollow central portion  22  for receiving a fuze. The exterior surface of the body  20  includes a plurality of recesses  24  formed thereon for receiving the EDIs. Each recess  24  includes an opening  26  into the hollow central portion  22  of the grenade body  20  to allow deflagration cord to connect the EDIs with the fuze. The grenade body  20  also includes an opening  28  on the exterior surface for insertion of the fuze. The opening  28  connects with the hollow central portion  22 . 
     FIG. 3A schematically shows a fuze  30 . Fuze  30  is disposed in the hollow central portion  12  of the grenade body  10  or the hollow central portion  22  of the grenade body  20 . The EDI grenade contains a single fuze  30 . Fuzing methods include thermal, time delay, pressure sensing and impact, depending upon the application. The EDIs (FIG. 4) are all connected to this common fuze  30  so that the EDIs will all initiate at the same time. FIG. 3B shows a fuze cap  32  for closing the openings  18 ,  28  on the exterior surface that connects with the hollow central portions  12 ,  22 . The fuze cap  32  may include threads  34  that mate with threads on the interior of openings  18 ,  28 . 
     FIG. 4 is a side view of an explosively driven impactor (EDI)  40 . EDI  40  includes a circular metal disk  42 , a backing layer  44 , high explosive  46 , an ignition device  48  and deflagration cord  50 . The EDI  40  fits in the recesses  14 ,  24  in the grenade bodies  10 ,  20  with the circular metal disk  42  facing outward. The deflagration cord  50  is fed through the openings  16 ,  26  in the recesses  14 ,  24 . All the cords  50  are joined together and then attached to fuze  30  so that all the EDIs will actuate at the same time. 
     Circular metal plate  42  is preferably concave on its side  52 , that is, the side that faces away from the grenade body. The internal side of plate  42  is preferably convex. A preferred metal for plate  42  is copper. The thickness of plate  42  is, for example, from about 0.07 inches to about 0.125 inches. The plate thickness depends on the plate diameter and the target thickness desired to be penetrated. The plate  42  is pressed formed into its curved shape. Copper is easily formed into different shapes. The recesses  14 ,  24  are deep enough so that the EDIs  40  do not extend further outward than the adjacent exterior surface of the body  10 ,  20 . 
     Behind plate  42  is a backing layer  44  comprising an elastomer such as solid rubber (i.e., not foam rubber). The backing layer  44  is attached to plate  42  with adhesive. The high explosive  46  may be molded into shape or pressed into recesses  14 ,  24 . If the explosive  46  is molded, it is adhered into the recesses  14 ,  24  with an adhesive compatible with the explosive  46 . The explosive  46  is preferably a Class 1.1 High explosive such as C4 or HMX. The plates  42  with backing layer  44  attached are dropped into the recesses  14 ,  24  on top of the explosive  46 . Plate  42  is secured with a retaining ring  60  (See FIG.  5 ). There is a groove  62  along the circumference of each recess  24  (See FIG. 2) to accept the retaining ring  60 . The backing layer  44  is slightly compressed during the retaining ring installation to take up any volume between the backing layer  44  and the explosive  46 . 
     Prior to installing the explosive  46  and plate  42 , an ignition device  48  is installed into each recess  14 ,  24 . The ignition device  48  has a small amount of energetic material, such as Boron Potassium Nitrate, in a metallic housing to initiate the explosive  46 . Deflagration cords  50  are attached to each ignition device  48 . After the ignition devices  48  are all installed and the deflagrating cords  50  are fed out of each recess  14 ,  24  and into the fuze hole  12 ,  22 , the explosives  46  and plates  42  are installed. After the explosives and plates are installed the deflagrating cords  50  are connected together and joined to a single fuze  30 . The fuze is then installed into by way of opening  18 ,  28  into the hollow central portion or fuze hole  12 ,  22 . A fuze cap  32  is preferably threaded to cover the opening  18 ,  28 . If a time delay fuze is used (such as those used in hand grenades) there will be a pull pin through the cap  32 . When the pull pin is pulled, the fuze is activated. 
     The metal plates  42  undergo a controlled acceleration when the explosive  46  is initiated. The EDI performance characteristics are tailored to meet the required flight distance and target strength. The EDIs  40  are substantially evenly patterned on the grenade body surface. The EDIs  40  are simultaneously initiated when the fuze  30  senses a specific environmental temperature (if the fuze is a thermal fuze). In the agent defeat application, the EDIs are initiated by a thermal fuze when the HTTR reaction drives the temperature in the target area to 250-500° F. Dependent upon the target penetration requirement, the weight ratio of plate  42  to high explosive  46  can be less or greater than one to two. 
     The grenade disperses the EDIs  40  in multiple directions at a variety of target configurations and at a large velocity range. During dispersal, the grenade can interact with a variety of stationary objects. The body structure is designed to withstand high acceleration loads and high velocity impacts. The orientation of the grenade can vary depending on launch/dispersal velocities and impact angles. Therefore, the grenade body contour is designed with a self-righting shape. At rest, the grenade will position itself in a predefined orientation. This orientation will aim a predefined number of EDIs  40  in a repeatable direction with respect to the ground surface. 
     Upon detonation, the plates  42  are dispersed at velocities great enough to create holes in metal targets such as steel containers. The penetration ability of even a small EDI is substantial. For example, a 2-inch diameter EDI can create a hole in 1-inch thick armor plate. The size of the EDI grenade will depend upon the size of the EDI utilized. The EDIs employed in the grenade have greater penetration capability against armored targets than existing hand thrown grenades such as the anti-personnel M67 and M61 hand grenades. Depending upon the size of the individual EDI, the EDI can penetrate several inches of metal armor. 
     Some advantages of the EDI grenade include: 
     1) Incorporating a number of EDIs into a single grenade to effect a much greater level of damage against equipment and personnel than a single EDI. 
     2) Minimal collateral damage effects to the surrounding area due to the low-overpressure characteristic of the EDI grenade. For example, if the target were a container filled with weaponized Anthrax spores, the lower-overpressure generated by the EDI grenade would minimize dispersal of the Anthrax spores. This is due to the smaller amount of high explosives required for the EDI operation than that required for hand grenades of comparable size. 
     3) The EDI grenade is multi-directional. A self-righting mechanism is not required. For example, in agent defeat applications, the EDI grenade can affect storage containers regardless if it lands next to or on top of a container and regardless of its landing orientation. 
     In an alternative embodiment of the invention, each explosively driven impactor comprises a metal plate  42 , a backing layer  44  and an explosive  46 . The explosive  46 , backing layer  44  and metal plate  42  are contained in a metal housing  68  in the shape of a cup (FIG.  4 A). The metal housing  68  is open at the top so that the metal plate  42  is free to launch. The metal housing  68  is made of, for example, aluminum having a thickness of about 0.02 inches. The ignition devices  48  are not used in this embodiment. 
     The explosive  46 , backing layer  44  and metal plate  42  are placed in housings  68 . Housings  68  are then placed in recesses  14 ,  24 . An elastomeric gasket  64  (FIG. 5A) is placed atop the housing  62 . The retaining ring  60  is then placed in groove  62 . The elastomeric gasket  64  between the top of housing  68  and retaining ring  60  takes up any assembly gaps and compensates for thermal dimensional changes. 
     In this alternative embodiment, a booster charge  66  (FIG. 6) is placed in the hollow central portions  12 ,  22  of the body  10 ,  20 , along with fuze  30 . Fuze  30  initiates booster charge  66  which initiates the explosive  46  in the individual EDIs. A physical connection (deflagration cord) between the booster charge  66  and the explosive  46  is not needed, but may be used if desired. The booster charge  66  is near enough to explosive  46  to initiate explosive  46  without deflagration cord. Booster charge  66  comprises, for example, a high explosive. 
     While the invention has been described with reference to certain preferred embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.