Abstract:
The present invention is devoted to providing projectiles which can be configured as relatively lightweight warhead assemblies that are comparable to heavier warhead assemblies in target-destruction effectiveness. In accordance with exemplary embodiments, the lightweight warhead assemblies can be more efficiently carried in greater numbers on, for example, aircraft platforms. Because these lightweight warhead assemblies can replace existing, larger warhead assemblies, a standard size warhead assembly can be used to attack different types of targets. In addition, various submunitions or unitary warheads can be incorporated into payload containers having a common external shape with common aerodynamic and mass properties, as well as common guidance, sensor, fuzing, and mechanical and electrical interfaces. A standardized, or modular approach improves the interchangeability of various warhead assemblies, reduces costs of configuring and operating the aircraft platform, and enables a reduction in the size of internal weapon bays of aircraft platforms.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to projectiles, and more particularly, to lighter warhead assemblies which achieve levels of performance that are comparable to much heavier warhead assemblies. 
     2. State of the Art 
     The design of an effective penetrating projectile, such as a warhead, often involves balancing between competing requirements. A warhead must have adequate penetration, blast, and fragmentation performance to effectively destroy the intended target. One important factor in the design of a warhead is its mass. The greater the mass of the warhead, the greater force imparted to the target upon impact. However, the greater the mass of the warhead, the more difficult it is to deliver the warhead to the target, particularly with munitions carried by aircraft platforms. Warheads of relatively large mass require more fuel to carry, reduce maneuverability of the aircraft, occupy more space on the aircraft platform, appear more prominently on radar signatures, and must be carried in fewer numbers. 
     Existing relatively lightweight warhead assemblies having a weight on the order of 1,000 lbs. lack sufficient performance capabilities and can be ineffective against certain targets. Therefore, it is common to carry different warhead assemblies of varying sizes and configurations on aircraft platforms to accommodate different types of targets. These warheads are different in their aerodynamics, their mass, and their mechanical and electrical interfaces with the aircraft. These differences limit the flexibility of the aircraft platform to accommodate different weapon configurations, increase the cost of configuring and operating the aircraft, and require larger weapon bays to accommodate the warhead assemblies. 
     Accordingly, it would be desirable to provide projectiles which can accommodate different types of targets, but which avoid the drawbacks associated with delivering different warhead assemblies designed to accommodate different types of targets. 
     SUMMARY OF THE INVENTION 
     The present invention is devoted to providing projectiles which can be configured as relatively lightweight warhead assemblies that are comparable to heavier warhead assemblies in target-destruction effectiveness. In accordance with exemplary embodiments, the lightweight warhead assemblies can be more efficiently carried in greater numbers on, for example, aircraft platforms. Because these lightweight warhead assemblies can replace existing, larger warhead assemblies, a standard size warhead assembly can be used to attack different types of targets. In addition, various submunitions or unitary warheads can be incorporated into payload containers having a common external shape with common aerodynamic and mass properties, as well as common guidance, sensor, fuzing, and mechanical and electrical interfaces. A standardized, or modular approach improves the interchangeability of various warhead assemblies, reduces costs of configuring and operating the aircraft platform, and enables a reduction in the size of internal weapon bays of aircraft platforms. 
     Generally speaking, exemplary embodiments are directed to warhead assemblies including a main body portion and a substantially ogive-shaped end portion, the substantially ogive-shaped end portion having an external surface with a first radius of curvature and an internal surface having a second radius of curvature, a ratio of the first radius of curvature to the second radius of curvature being approximately 1.27-1.40, and a substantially cylindrical body portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Other objects and advantages of the present invention will become more apparent to those skilled in the art from reading the following detailed description of preferred embodiments in conjunction with the accompanying drawings, wherein like elements have been designated with like reference numerals, and wherein: 
     FIG. 1 is a side view of a warhead assembly constructed according to an exemplary embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of the FIG. 1 warhead casing; 
     FIG. 3 is an enlarged partial cross-sectional view of the FIG. 2 warhead casing; 
     FIG. 4 is an enlarged partial cross-sectional view of the FIG. 2 warhead casing; 
     FIG. 5 is a cross-sectional view taken along line  5 — 5  of FIG. 1; 
     FIG. 6A is an enlarged partial cross-sectional view of the FIG. 1 area  6 — 6 ; 
     FIG. 6B is a top view of a warhead assembly including a guidance kit according to an exemplary embodiment of the present invention; 
     FIG. 7 is a partial, enlarged cross-sectional view of the FIG. 1 area  7 — 7 . 
     FIG. 8 is a side view of the warhead assembly of FIG. 1 including a tail section. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates an exemplary warhead assembly  100  constructed according to the principles of the present invention. The warhead assembly  100  includes a warhead casing  200  having a longitudinal axis A, a hardback assembly  500 , a retaining member  600 , and a fuse assembly  700 . 
     Referring to FIG. 2, the warhead casing  200  comprises a generally cylindrical main body portion  201 , a first open-end portion  203  defining a bore  205 , and a second substantially ogive-shaped closed end portion  207 . The main body portion together with the first and second end portions define a substantially continuous exterior peripheral surface  211  and interior surface  213 . 
     The internal longitudinal dimension of the warhead casing  200  is indicated by reference numeral  219 , and is measured from a first substantially flat end surface  209  at first end portion  203  to a second substantially flat interior end surface  215  defined at second end portion  207 . The external longitudinal dimension of the warhead casing  200  is indicated by reference numeral  221 , and is measured from the first end surface  209  to a second exterior end surface  217  located at second end portion  207 . 
     The longitudinal distance between the second interior end surface  215  and the second exterior end surface  217  constitutes a solid section of the second end portion  207  which is indicated by reference numeral  220 , and which corresponds to the difference between the internal longitudinal dimension and external longitudinal dimension. The extent of this solid section of second end portion  207  is an important factor in defining the mass distribution and penetrability of the warhead casing  200 . In an exemplary embodiment, the ratio of the longitudinal extent  220  of this solid section over the external longitudinal dimension  221  is on the order of 0.084-0.086, but can be any other specified ratio depending upon desired performance characteristics. 
     Other features of the second substantially ogive-shaped end portion  207  are illustrated in FIG. 3. A first interior tangent point  323  and a first exterior tangent point  325  are defined along interior surface  213 , and exterior surface  211 , respectively, in an area of transition between the main generally cylindrical body portion  201  and the substantially ogive-shaped second end portion  207 . The first and second tangent points  323  and  325  are located at a predetermined longitudinal distance  327  from the second interior end surface  215 , and are spaced from the second exterior end surface  217  by a predetermined longitudinal distance  329 . 
     The location of tangent points  323  and  325 , as defined by longitudinal dimensions  327  and  329 , corresponds to the extent of longitudinal elongation of the ogive shape possessed by second end portion  207 . In one embodiment, the ratio of longitudinal dimension  329  to longitudinal dimension  221  of the warhead casing  200  is on the order of 0.38, but can be any specified ratio depending on desired performance characteristics. This relative dimensioning is indicative of the longitudinal dimensions or elongation of the ogive-shaped second end portion  207  relative to the overall longitudinal dimension of the warhead casing  200 , and has been shown to provide advantageous results. 
     The outer diameter of the warhead casing  200 , as measured at the FIG. 3 tangent points  323  and  325 , is indicated by reference numeral  331 . As illustrated in FIG. 3, the warhead casing  201  curves inwardly or gradually converges, defining a radius of curvature  333  along exterior surface  211 , and a radius of curvature  335  along interior surface  213 . The radial thickness  337  (the radial direction being normal to the longitudinal axis A) of the warhead casing  200  gradually increases in a direction from the first and second tangent points  323  and  325  toward the second end portion  207  as a result of a predetermined difference in the radii of curvature  333  and  335 . In an exemplary embodiment, the ratio of the radius of curvature  333  over radius of curvature  335  is on the order of 1.27-1.40, but can be any other specified ratio depending on desired performance characteristics. These relative dimensions are indicative of the rate of increase in radial thickness of the warhead casing, and provide desirable thickness and mass distribution properties in accordance with an exemplary embodiment. 
     In a direction toward second end surface  217  of the second end portion  207 , second interior tangent points  339  and  339 ′ are disposed along interior surface  213  and are located a predetermined longitudinal distance  343  from the second interior end surface  215 . Tangent point  339  is also a predetermined radial distance  340  from the portion of exterior surface  211  located at exterior tangent point  325 . Tangent points  339  and  339 ′ are separated by a predetermined radial separation  341 . 
     The portion of interior surface  213  extending between tangent points  339  and  339 ′ to second interior flat surface  215  constitutes a substantially curved surface having a radius of curvature  345 . The second interior end surface  215  is defined by radial dimension  347 . The extent of radial dimension  347  helps define the interior shape and the mass distribution properties of warhead casing  200 . 
     The second exterior end surface  217  is defined by a predetermined radial dimension  349 . The extent of radial dimension  349  helps define the exterior shape and the mass distribution properties of warhead casing  200 . 
     In an exemplary embodiment, the warhead casing  200  further comprises a threaded nose portion  351  extending longitudinally from the second exterior end surface  217 . 
     Certain details of the first open end portion  203 , of warhead casing  200  will now be described by reference to FIG.  4 . As the main body portion  201  extends toward the first end surface  209 , a transition portion having a predetermined radius of curvature  453  is defined along exterior surface  211 . A sloped surface  455  connects the transition portion defined by radius of curvature  453  with a second transition point  459 . Sloped surface  455  defines a predetermined angle  457  relative to the longitudinal direction. A substantially flat surface  461  extends from second transition point  459  to the second flat end surface  209 . 
     The first end portion  203  defines a bore  205  having an inner diameter  463 . Similarly, substantially flat surface  461  defines an outer diameter  465 . By this construction, first end portion  203  is strengthened thereby permitting connection of various accessories, such as a booster section, to the warhead casing  200 . 
     Warhead casing  200  can be constructed of any suitable high strength material. For example, the warhead casing can be constructed of a heat treatable alloy steel. In an exemplary embodiment, the heat treatment is carried out to military specification MIL-H-6875, CL A. A suitable heat treated alloy steel will have a yield strength of approximately 170,000 psi or more, an ultimate strength of approximately 180,000 to 200,000 psi, or more, Charpy V-notch impact resistance at −40°(+/−) 2° Farenheight of approximately 20 ft.-lb. on 3 per section, with a 15 ft.-lb. minimum, or more, and a Brinnel hardness number (BHN) of approximately 375 to 415, or more. By way of example, one suitable heat treatable alloy is AISI 4335 steel. 
     The overall shape and dimensions of the warhead casing  200  are an important factor in achieving the desired objectives of the present invention. The following dimensions and ratios are given as an illustration of one exemplary embodiment of a warhead casing constructed according to the principles of the present invention. 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Value (in inches, unless otherwise 
               
               
                   
                 Dimension 
                 indicated) 
               
               
                   
                   
               
             
             
               
                   
                 219 
                 64.52-64.64 
               
               
                   
                 220 
                 5.94-6.06 
               
               
                   
                 221 
                 70.52-70.64 
               
               
                   
                 327 
                 21.011-21.031 
               
               
                   
                 329 
                 27.011-27.031 
               
               
                   
                 331 
                 11.50-11.70 
               
               
                   
                 333 
                 80.99-81.01 
               
               
                   
                 335 
                 58.0-64.0 
               
               
                   
                 337 
                 0.94-1.06 
               
               
                   
                 340 
                 4.02-4.18 
               
               
                   
                 341 
                 3.38-3.44 
               
               
                   
                 343 
                 1.97-2.03 
               
               
                   
                 345 
                 0.45-1.05 
               
               
                   
                 347 
                 1.984-2.004 
               
               
                   
                 349 
                 2.310-2.330 
               
               
                   
                 457 
                 2.5 0 6.5 degrees 
               
               
                   
                 463 
                 9.57-9.63 
               
               
                   
                 465 
                 12.97-13.03 
               
               
                   
                   
               
               
                   
                 Ratio 
                 Value 
               
               
                   
                   
               
               
                   
                 333/335 
                 1.27-1.40 
               
               
                   
                 220/221 
                 0.084-0.086 
               
               
                   
                 329/221 
                 0.382-0.383 
               
               
                   
                   
               
             
          
         
       
     
     A warhead assembly incorporating a warhead casing constructed in accordance with exemplary embodiments of the present invention provides numerous advantages. For example, by controlling the forward exterior and interior shape of the warhead casing, the particular thicknesses and variations in thicknesses of the warhead casing, and mass distribution, a warhead can be provided with exceptional structural strength, enabling survival of the warhead upon impact with hardened structures. The shape of the warhead casing enables penetration of hard materials such as rock or concrete to a greater depth than other warheads weighing on the order of 2,000 pounds, and to a depth that exceeds certain existing 1,000 pound class warheads. 
     FIG. 5 illustrates details of an exemplary hardback assembly  500  which can be mounted to the warhead casing  200 . Hardback assembly  500  includes a hardback plate  501 . The hardback plate  501  can be constructed of any suitable material, such as high strength aluminum alloy material. Hardback plate  501  is connected to an adaptor lug  503  by a suitable fastener member, such as a threaded bolt  505 . Adaptor lug  503  can also be constructed of any suitable material, such as a heat-treated alloy steel. Adaptor lug  503  is connected to the warhead casing by a suitable threaded fastener member, such as threaded bolt member  507 . Adapter lug member  503  defines an opening having a counter bore  509  disposed therein. 
     Hardback assembly  500  facilitates mounting of the warhead assembly  100  to a suitable launch platform, such as an aircraft, as known in the art. 
     As illustrated in FIG. 6A, a retaining member  600  is threadably received about the threaded nose portion  351  of warhead casing  200 . Retaining  600  includes a threaded internal bore  601  which mates with the exterior threading of nose member  351  of the warhead casing  200 . Once threaded over nose member  351 , a set screw  602  acts to fix the position of retaining member  600  relative to the warhead casing  200 . Retaining member  600  further includes an external threaded surface  603  and upstanding flange member  605 . Retaining member  600  can be formed of any suitable material, such as an alloy steel. 
     By this construction a retaining bolt member  600  permits attachment of various accessories to the second end portion  207  of the warhead casing  200 . As illustrated in FIG. 6B one such accessory is a guidance kit  607 . Guidance kit  607  includes means to generate signals which guide the flight path warhead assembly  100 . Any suitable guidance system can be used in conjunction with the present invention. Suitable guidance systems include active or semi-active laser guided systems, such as those used in a guided bomb unit (GBU-24) and (GBU-27), produced by Raytheon Corporation. Other guidance systems which can be used include a combined global positioning system/inertial navigation system (GPS/INS), which is known in the art. 
     Guidance kit member  607  may be attached to the warhead casing  200  via retaining member  600  in any suitable fashion. For example, a rear section of guidance kit member  607  can be threadably received over external threaded surface  603  of retaining member  600 . Guidance kit member  607  can further include one or more stabilizing and/or steering air vane members  609 . 
     At the opposite first end  203  of the FIG. 2 warhead casing  200 , a fuse assembly  700  of the exemplary FIG. 7 embodiment is at least partially received within bore  205  of the first end  203 . In the exemplary embodiment shown in FIG. 7, an aft closure retaining ring  701  is received within threaded counter bore  464  thereby retaining the fuse assembly  700  in its proper position. 
     Aft closure  703  is positively engaged by the aft closure retaining ring  701 . An opposite side of the aft closure is engaged by a shoulder  704  formed along bore  205 . By this construction, the aft closure  703  is positively located and retained in its proper position. Aft closure  703  is provided with one or more openings  705  which are closed by a threaded plug member  706 . A fuse liner  707  is received within the aft closure  703 . A fuse liner retaining flange  711  is provided at one end of the fuse liner  707  and is received upon a shoulder  713  formed along the interior of aft closure  703 . A fuse liner retaining ring  709  is threadably received within aft closure  703  and is threadably driven into positive engagement with fuse liner retaining flange  711 . In this manner, fuse liner  707  is positively retained within aft closure  703 . 
     In an embodiment of the present invention in which warhead casing  200  carries a payload material, fuse assembly  700  is provided to activate the payload material. Any suitable payload material can be carried within warhead casing  200 , such as conventional or nuclear explosives, as well as agent-defeating materials such as incendiaries, chemicals or submunitions. The components of fuse assembly  700  can be constructed of any suitable material. A high strength, heat treated alloy steel is one such suitable material. 
     End surface  209  can be further provided with a plurality of blind bores  715 . Bores  715  can serve as a means for attachment of an exemplary FIG. 8 tail section  800  to the warhead casing  200 . As illustrated in FIG. 8, tail section  800  can be attached to the end surface  209 . The tail section  800  can include a suitable booster device. For example, a rocket booster motor can be incorporated in the tail section  800 . Tail section  800  can further include stabilizing and/or control vanes  801 . In an alternate embodiment, an appropriate guidance system can be mounted within tail section  800 , rather than through the FIG. 3 threaded nose member  351 . 
     According to the principles of the present invention, the exemplary warhead assembly  100  can have a total weight on the order of 900-1,000 lbs. (with approximately 250 lbs. of payload materials), or any specified weight for a given payload, and still possess the penetration and destructive capabilities comparable with warhead assemblies of greater weight. For example, the warhead having a weight on the order of 900-1,000 lbs. can have performance characteristics comparable to a warhead weighing on the order of 2,000 pounds. Such relatively lightweight warhead assemblies can be carried more efficiently and in greater numbers on launch platforms. These relatively lightweight warhead assemblies can be used to replace existing heavier warhead assemblies without significant sacrifice in effectiveness. This standardization or modular approach provides significant cost savings benefits over existing systems, and enables a reduction in the space occupied by the warhead assemblies on launch platforms. 
     Although the present invention has been described by reference to particular embodiments, it is in no way limited thereby. To the contrary, modifications and variants will be apparent to those skilled in the art in the context of the following claims.