Patent Publication Number: US-8985025-B1

Title: Submunition and cluster munition containing submunitions

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority of U.S. provisional patent application Ser. No. 61/567,238 filed on Dec. 6, 2011, which is incorporated by reference herein. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The inventions described herein may be manufactured, used and licensed by or for the U.S. Government for U.S. Government purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates in general to munitions and in particular to submunitions and cluster munitions. 
     Cluster bombs may be dispensed from dispensers and dropped in a pattern to blanket a target area. This method may be used to increase the probability that an individual submunition will encounter, engage, and destroy targets within the target area. Submunitions may be ejected in a dispersion pattern that may depend on the nature of the ejection mechanism used in the submunition carrier. Submunitions may be armed as they are dispensed from the cluster bomb or other carrier. If the submunitions do not encounter and engage a target, they may remain unexploded, armed, and lethal when they impact the ground and after impact with the ground. 
     This overall approach to engaging one or more targets with many individual munitions or dispensed submunitions is often referred to as an “area attack” and is a statistical methodology for defeating targets. Area attack may be contrasted with “precision attack,” which typically uses one precision-guided munition to engage each target individually. Assuming an accurate target location, precision attack may yield a higher percentage of kills per munition, but at a substantially higher cost due to the use of precision guidance and control on each munition. 
     Submunitions of various kinds may be ejected or dispersed from a carrier, such as a missile, mortar, rocket or cannon projectile. Generally, the carrier brings the submunitions to a location close to the target, and the submunitions are then ejected or dispersed near the target. The submunitions may free fall from the ejection location and rely on statistical distribution to hit the target, or the submunitions may include a guidance system to move them closer to the target. A number of methods are known for guiding the submunitions to the final target. 
     One method employs terminal guidance systems, such as infrared seekers and other IR detection and guidance systems, as shown, for example, in U.S. Pat. No. 4,492,166. Another method provides mechanical control systems, such as aerofoils or special wings with a target detector, such as those shown in U.S. Pat. No. 5,155,294 and U.S. Pat. No. 4,635,553. In U.S. Pat. No. 4,554,871, assigned to Allied Corporation, there is disclosed a missile that carries at least two asymmetric submunitions. The guidance system on each submunition causes the submunition to precess about its center axis, thereby creating an appropriate search pattern or controlling the flight path of the submunition after a suitable target has been acquired by the submunition&#39;s guidance system. 
     Satellite aided global location systems, such as the Global Positioning System (GPS), are also well known in the art. These systems utilize several satellites to permit a body on the earth to calculate, such as by triangulation, its precise location on the globe. Global location systems today are used in guidance systems for a wide variety of objects. These include munitions, such as bombs and missiles. There is shown, for instance, in U.S. Pat. No. 5,943,009, assigned to Northrop Grumman Corporation, a munition with a tail fin assembly, at least one flight control surface having an actuator, and a guidance system having a GPS receiver for effecting control of the actuator to facilitate guiding of the munition. 
     U.S. Pat. No. 5,260,709 discloses a system and method that uses differential computation of position relative to a GPS coordinate system and the computation of an optimum weapon flight path to guide a weapon to a non-moving fixed or re-locatable target. The system comprises an airborne platform with a navigation subsystem that utilizes the GPS satellite system to provide the coordinate system, and a synthetic array radar (SAR) to locate desirable targets. Targeting is done prior to weapon launch; therefore, the weapon requires only a navigation subsystem that also utilizes the GPS satellite system to provide the same coordinate system that the platform uses. 
     There is shown in U.S. Pat. No. 5,507,452 a precision guided system suitable for use in conventional aircraft-launched bombs. The system includes a kit mounted upon the nose of the conventional bomb which replaces the conventional fuse disposed in a fuse well. The kit includes guidance electronics that control a self-contained jet reaction device and GPS P-code receiver electronics. The bombs are readied for discharge by signals broadcast from the aircraft into the bomb bay. Readying the bombs includes transferring initial GPS data and commencing operation of a gas generator which powers the jet reaction device. 
     There is shown in U.S. Pat. No. 6,481,666 a method and system for guiding submunitions in which a satellite-aided global location system is utilized to control a parachute disposed on each submunition. In particular, the orientation of the parachute is adjusted by a servo, which in turn is controlled by the guidance system, thus allowing alteration in direction of downward travel of the submunition. U.S. Pat. Appl. Publication No. 2007/0266884 discloses a dispenser system for controllably deploying components, such as unmanned ground sensors, into a desired pattern and orientation. The dispenser system utilizes a GPS-based guidance system to control the deployment of the main canister, rather than the submunitions. 
     All of the above-mentioned systems include the use of satellite-aided global location systems to guide a munition over a relatively long distance and/or control a relatively complex guidance system (to control, for example, the orientation of fins, parachutes, etc.). Thus, the electronics and control system required to guide the munitions are complex and expensive to manufacture and maintain. Further, the submunitions themselves are incapable of communicating with one another so as provide selective targeting. Moreover, deployment of conventional cluster munitions results in relatively high incidences of unexploded ordinance. 
     The Oslo Treaty dated May 30, 2008 requires that all cluster munitions weighing less than 20 kg contain less than 10 submunitions. Each submunition must be single target discriminating, must weigh more than 4 kg, and must have an electronic self-destruct and self-deactivate capability. The conventional cluster munitions described above do not meet the Oslo Treaty requirements. A need exists for a cluster munition and submunitions that meet the Oslo Treaty requirements, while also providing effective targeting and enemy elimination characteristics. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a cluster munition and submunitions that meet the Oslo Treaty requirements, while also providing effective targeting and enemy elimination characteristics. 
     One aspect of the invention is a submunition. The submunition may include a submunition body with explosive material therein. A deployable antenna/stabilizer is attached to the submunition body. A wireless communication device is disposed on the submunition and is electrically connected to the deployable antenna/stabilizer. A microprocessor is disposed on the submunition and is electrically connected to the wireless communication device. A means for determining a relative location of the submunition is electrically connected to the microprocessor. A multi-mode fuze is electrically connected to the microprocessor. The multi-mode fuze includes at least two of: (a) a proximity fuze for detonating the submunition in a selected proximity of the submunition to a target; (b) a point detonating fuze for detonating the submunition when contacting a target; and (c) a timer-based fuze for detonating the submunition after a selected time has elapsed. 
     The deployable antenna/stabilizer may be, for example, at least one of a coil, a foldable flat spring and a drogue chute. 
     The submunition may include one or more sensors selected from the group consisting of, for example, IR sensor, microwave sensor, laser sensor, UV sensor, barometer, and altimeter. The sensors are electrically connected to the microprocessor. 
     Another aspect of the invention is a cluster munition. The cluster munition includes a submunition delivery vehicle having a main body portion. A plurality of the inventive submunitions are disposed in the main body portion. The delivery vehicle may include a wireless communication device and a microprocessor electrically connected to the wireless communication device. 
     Another aspect of the invention is a method that includes launching the cluster munition and ejecting the plurality of inventive submunitions from the delivery vehicle. The method includes creating a wireless communication network between the wireless communication devices of the plurality of submunitions. Creating the network may include creating a wireless communication network between the wireless communication devices of the plurality of submunitions and the wireless communication device of the delivery vehicle. 
     The method may include determining relative locations of the plurality of submunitions using each submunition&#39;s means for determining relative location. Target location information may be sent from the microprocessor of the delivery vehicle to respective microprocessors of each of the plurality of submunitions. 
     The target location information may include a single desired target location for each submunition, a listing of all possible target locations, and a friendly/hostile identifier for each of the all possible target locations. 
     The method may include using each submunition&#39;s respective microprocessor and means for determining relative location to estimate the submunition&#39;s end location; then, comparing the submunition&#39;s estimated end location to its single desired target location; and then, executing a safe action if the estimated end location is not the single desired target location or if the desired target location has a friendly identifier. The safe action may include one of deactivating the submunition and detonating the submunition. 
     The method may include, for each submunition that reaches ground, wirelessly transmitting from the submunition information regarding location of the submunition and status of the submunition. The status information may include one of a pre-deactivation state and a pre-self-destruct state. 
     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 one embodiment of a submunition. 
         FIG. 1A  is a perspective view of another embodiment of a submunition. 
         FIG. 2  is a partially transparent, cut away perspective view of the submunition body of  FIG. 1 . 
         FIG. 3  is a perspective view of the submunition of  FIG. 1  with the compressible stabilizer in a compressed state. 
         FIG. 4  is a partially cut away perspective view of one embodiment of a cluster munition. 
         FIG. 5  is a temporal sequence showing ejection of submunitions from a delivery vehicle. 
         FIG. 6  is a perspective view of the submunition of  FIG. 1  showing additional features of one embodiment of a deployable antenna/stabilizer. 
         FIG. 7  is a perspective view of the submunition of  FIG. 6  including another embodiment of a deployable antenna/stabilizer. 
         FIG. 7A  is a perspective view of a coil spring rigging line. 
         FIG. 8  is a block diagram of electrically connected components of a submunition. 
         FIG. 9  is a temporal sequence showing detonation modes of a multi-mode fuze for a submunition. 
         FIG. 10  shows one embodiment of a method of deploying a cluster munition with submunitions. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an embodiment of a submunition  10  having a submunition body  12  and a deployable antenna/stabilizer  16  attached to submunition body  12 . Deployable antenna/stabilizer  16  performs at least two functions. A first function is to act as a wireless communications antenna. A second function is to aerodynamically stabilize, orient, or decelerate submunition  10  during its descent. A third, optional function is to facilitate ejection of submunition  10  from a delivery vehicle  30  ( FIG. 4 ) using spring force. Deployable antenna/stabilizer  16  may be embodied in several forms. 
     In  FIG. 1 , deployable antenna/stabilizer  16  is in the form of a coil  14  having a first end  18  attached to submunition body  12  and a second end  20  opposite first end  18 . In the deployed or uncompressed state of  FIG. 1 , second end  20  is distal submunition body  12  and coil  14  has a diameter that increases from first end  18  to second end  20 . Coil  14  may stabilize the orientation of submunition  10  as it descends in the air. Coil  14  may be made of, for example, a metallic or semi-metallic material Coil  14  may be coiled on its edge  36  ( FIG. 2 ) or may be coiled about its face  38  ( FIG. 2 ). Coiling about face  38  will present a larger surface area in the direction of descent of submunition  10  and increase the drag. Coil  14  may include a plurality of curved and/or straight portions. 
     One or more wireless communication devices  22  ( FIG. 1 ) may be disposed on submunition  10 . Wireless communication device  22  may be electrically connected to coil  14 . Coil  14  may function as an antenna for wireless communication device  22 . Wireless communication device  22  may communicate with communication devices exterior to submunition  10  for purposes such as, for example, receiving programming data, transmitting sensor data, etc. Wireless communication device  22  may be, for example, an active and/or passive RFID chip, a laser, or a microwave or millimeter wave communication device. 
     In  FIG. 1A , deployable antenna/stabilizer  16  is in the form of a foldable flat spring  11  having a first end  13  attached to submunition body  12  and a second end  15  opposite first end  13 .  FIG. 1A  shows foldable flat spring  11  in a deployed state. Foldable flat spring  11  may be made of, for example, a metallic or semi-metallic material. Foldable flat spring  11  may be electrically connected to and act as an antenna for wireless communication device  22 . Foldable flat spring  11  may also aerodynamically stabilize, orient, or decelerate submunition  10  during its descent. One or more foldable flat springs  11  may be used with a single submunition body  12 . 
       FIG. 2  is a partially transparent, cut away perspective view of submunition body  12  of  FIG. 1 . Only the lower portion of coil  14  is shown in  FIG. 2 . Submunition body  12  may be made of any conventional material, for example, a metallic material that is prone to high fragmentation when submunition  10  is detonated. Body  12  may include a metal case  24  that may be scored to increase fragmentation. Ball bearings  26  may be disposed in metal case  24  to increase lethality, if desired. Explosive material  28  may be disposed in body  12 . 
       FIG. 3  shows deployable antenna/stabilizer  16  in the form of coil  14  in a compressed state, prior to deployment of submunition  10 . When used as deployable antenna/stabilizer  16 , foldable flat spring  11  may be similarly compressed prior to deployment of submunition  10 .  FIG. 4  shows a plurality of submunitions  10  disposed in a delivery vehicle  30 . Submunitions  10  may be stacked in a main body portion  32  of delivery vehicle  30 . Deliver vehicle  30  may be, for example, an artillery shell or cartridge. When compressed as shown in  FIGS. 3 and 4 , deployable antenna/stabilizer  16  may exert a spring force and function as an ejection means to facilitate ejection of submunition  10  from a rear  34  of delivery vehicle  30 .  FIG. 5  illustrates submunitions  10  being ejected from rear  34  of delivery vehicle  30 . 
     As seen in  FIG. 6 , coil  14  may be scored in certain locations to define discrete sections, such as sections  16   a  and  16   b , between scoring lines  40 . Scoring lines  40  enable sections of coil  14  to be easily and cleanly broken off to tailor the overall length of coil  14  to fit in various delivery vehicles. Such tailoring is especially useful when retrofitting existing cluster munition delivery vehicles with embodiments of submunitions  10 . 
     In the embodiment of  FIG. 6 , coil  14  includes a straight portion  42  at second end  20 . After submunition  10  is ejected from delivery vehicle  30 , coil  14  springs into the uncompressed state shown in  FIG. 6  and straight portion  42  may extend radially beyond the external radius or the circumference of submunition body  12 . That is, distance d in  FIG. 6  is greater than the length of external radius R of body  12  so that straight portion  42 , acting as an antenna for wireless communication device  22 , may transmit and receive RF signals to objects below (at lower elevations than) submunition  10 . Such objects may include other submunitions  10  ejected from delivery vehicle  30  or from another delivery vehicle. 
     One or more projections  44  may be attached to or formed integral with coil  14 . Projections  44  may increase the effective RF transmission and reception range of coil  14 , acting as antenna for wireless communication device  22 . Projections  44  may take any desired shape and size, as long as they do not hinder the compressibility of coil  14 . 
     In addition to coil  14  and flat foldable spring  11 , another form of deployable antenna/stabilizer  16  is a drogue chute  46  ( FIG. 7 ). Drogue chute  46  may be desirable for more massive submunitions  10 . Drogue chute  46  may be used with or without one of coil  14  and flat foldable spring  11 . Drogue chute  46  may be attached to submunition body  12  with rigging lines  48 . Drogue chute  46  can provide additional drag, thereby slowing descent of submunition  10 . Drogue chute  46  may also help provide proper orientation of submunition  10  relative to the ground. Parachutes, X-drags, or other means of increasing drag may also be used. 
     Rigging lines  48  attach drogue chute  46  to submunition body  12 . Rigging lines  48  may be partially or wholly made of metallic and/or semimetallic material. Rigging lines  48  may be electrically connected to wireless communication device  22  and may function as an antenna for wireless communication device  22 . If it is desired that drogue chute  46  also facilitate ejection of submunition  10  from delivery vehicle  30 , then each rigging line  48  may be in the form of a small, tightly wound coil spring ( FIG. 7A ). When used with coil  14 , rigging lines  48  of drogue chute  46  may be looped through coil  14  to thereby create an omnidirectional loop antenna. The length of rigging lines  48  may be adjusted to vary the drag on submunition  10 , to tailor rigging lines  48  to a desired radio frequency, or to conform to the size of coil. To increase drag, the diameter of drogue chute  46  may be greater than the diameter of the submunition body  12 . 
     As shown in  FIG. 8 , submunition  10  may include a programmable microprocessor  54  electrically connected to various devices, for example, wireless communication device  22 , sensors  52 , a multi-mode fuze  56  ( FIG. 2 ), and position locating means  50 . Position locating means  50  may determine at least the relative spatial location of submunition  10  and, in some embodiments, the absolute location of submunition  10 . Position locating means  50  may be, for example, a polarized RF relative positioning system. RF relative positioning systems are disclosed in, for example, U.S. Pat. No. 7,193,556 issued on Mar. 20, 2007; U.S. Pat. No. 7,298,255 issued on Nov. 20, 2007; and U.S. Pat. No. 7,425,918 issued on Sep. 16, 2008, which are all expressly incorporated by reference herein. Position locating means  50  may include an altimeter. Another type of locating means  50  is a GPS (global positioning system). The GPS may provide absolute location of submunition  10 . In the claims, the “means for determining a relative location of the submunition” corresponds to locating means  50 . 
     A variety of sensors  52  may be connected to microprocessor  54  to transmit and receive data. Sensors  52  may be disposed in any appropriate location within or on submunition  10 . Examples of sensors  52  are IR sensors, microwave sensors, laser sensors, UV detectors, temperature sensors, altimeters, barometers, timers, etc. Sensors  52  such as IR sensors, microwave sensors, and laser sensors may be used to measure proximity of submunition  10  to a target or location and/or provide data utilized to single target discriminate. Single target discrimination helps to avoid collateral damage. Environmental sensors, such as an altimeter, etc., may also assist in single target discrimination. In addition, environmental sensors may indicate that submunition  10  should be deactivated, for example, when submunition  10  has not exploded for a predetermined period of time after deployment. 
     Multi-mode fuze  56  may include at least two of: (a) a proximity fuze for detonating submunition  10  in a selected proximity of the submunition  10  to a target; (b) a point detonating fuze for detonating submunition  10  when contacting a target; and (c) a timer-based fuze for detonating submunition  10  after a selected time has elapsed. Preferably, multi-mode fuze  56  includes all three types of the afore-mentioned fuzes. As shown in  FIG. 9 , the proximity fuze may detonate submunition  10  when it is in a proximity distance Y of a target T. If the proximity fuze fails, the point detonating (impact) fuze may initiate detonation upon impact of submunition  10  with target T. If the point detonating fuze also fails, a timer-based fuze initiates detonation within a preset time period after firing. Multiple layers of redundancy are provided by multi-mode fuze  56 , which greatly diminishes the possibility of unexploded ordnance being left in the field. 
     In one embodiment, a cluster munition or delivery vehicle  30  ( FIG. 4 ) includes a programmable microprocessor  58  and a wireless communication device  60  electrically connected to microprocessor  58 . Prior to or after launching delivery vehicle  30 , target information may be loaded onto microprocessor  58  of delivery vehicle  30  and/or onto microprocessors  54  of submunitions  10  contained in delivery vehicle  30 . 
       FIG. 10  illustrates one embodiment of a method of deploying a cluster munition or delivery vehicle  30  containing submunitions  10 . In step S 1 , delivery vehicle  30  is launched from, for example, a gun tube. In step S 2 , at a selected point in the flight of delivery vehicle  30 , submunitions  10  are ejected from delivery vehicle  30 . In step S 3 , wireless communication devices  22 ,  58  of the submunitions  10  and vehicle  30  form a wireless communication network. In addition, other submunitions  10 , delivery vehicles  30 , and nearby entities (such as a drone or manned aircraft) may be part of the wireless communication network. 
     Before launch or at any point in the process, in step S 4 , wireless communication device  60  of delivery vehicle  30  or another wireless communication device (for example, a wireless device on a drone or manned aircraft) may send target location information to each submunition  10 . The target location information may include a single desired target location X N  for each submunition 1 through N (Table 1), a listing of all possible target locations (Table 2), and a friendly/hostile identifier for each of the all possible target locations (Table 2). One way to specify locations is by specifying latitude, longitude, and elevation. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 SINGLE DESIRED TARGET LOCATION 
               
            
           
           
               
               
               
            
               
                   
                 Submunition  
                 Target Location 
               
               
                   
                 Number 
                 Number 
               
               
                   
                   
               
               
                   
                 1 
                 X 1   
               
               
                   
                 2 
                 X 2   
               
               
                   
                 3 
                 X 3   
               
               
                   
                 N 
                 X N   
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Target Location 
                   
                   
               
               
                 Number 
                 Target Location 
                 Identifier 
               
               
                   
               
             
            
               
                 X 1   
                 Lat., Long. Elev. 
                 Hostile 
               
               
                 X 2   
                 Lat., Long. Elev. 
                 Hostile 
               
               
                 X 3   
                 Lat., Long. Elev. 
                 Friendly 
               
               
                 X N   
                 Lat., Long. Elev. 
                 Hostile 
               
               
                   
               
            
           
         
       
     
     In step S 5 , position locating means  50  of each submunition  10  may determine each submunition&#39;s absolute or relative position. The position information may be wirelessly communicated to other submunitions  10  and delivery vehicles  30 . In step S 6 , each submunition&#39;s respective microprocessor  54  and locating means  50  may be used to estimate that submunition&#39;s end location. In step S 7 , microprocessor  54  may then compare the submunition&#39;s estimated end location with its single desired target location. In step S 8 , microprocessor  54  may then execute a “safe action” if the estimated end location is not the single desired target location or if the desired target location has a friendly identifier. The “safe action” may include one of deactivating submunition  10  and detonating submunition  10 . 
     If no safe action was executed in step S 8 , and submunition  10  is in proximity to its single desired target, then, in step S 9 , proximity fuze in multi-mode fuze  56  will detonate submunition  10 . If the proximity fuze fails and submunition  10  impacts its single desired target, then, in step S 10 , the point-detonating fuze of multi-mode fuze  56  will detonate submunition  10 . If submunition  10  reaches the ground without detonating, then, in step S 11 , submunition  10  may wirelessly transmit its location information and its status information to, for example, one or more delivery vehicles  30  or another wireless communication device that is in range of submunition  10 , such as a communication device in a drone or manned aircraft. The status information may include whether submunition  10  is preparing to deactivate or whether submunition  10  is preparing to self-destruct. The location information and status information of submunition  10  after it reaches the ground is an important tool in eliminating the problem of unexploded ordnance. In step S 12 , submunition  10  will deactivate (for example, if submunition  10  is in a friendly location) or detonate (for example, if submunition  10  is in a hostile location). 
     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. For example, deployable antenna/stabilizer  16  may be embodied in forms other than coil  14 , foldable flat spring  11 , or drogue chute  46 .