Patent Publication Number: US-8985026-B2

Title: Penetrator round assembly

Description:
TECHNICAL FIELD 
     The disclosure generally relates to munitions and, more particularly, to projectiles that can penetrate reactive armor. 
     BACKGROUND 
     Explosive reactive armor is a type of vehicle armor that is designed to reduce the amount of penetration of projectiles, e.g., anti-tank rounds. In general, explosive reactive armor includes an explosive material sandwiched between two plates, e.g., metal plates. The plates and explosive material form a block-like module. Numerous modules are distributed over the base armor of a vehicle, e.g., tank, in order to form a protective layer of explosive reactive armor. 
     Generally speaking, in operation the explosive reactive armor is designed to deflect a projectile by altering the angle of incidence of the projectile to prevent the projectile from perforating the base armor of the vehicle. More particularly, as the projectile impacts the outermost plate of an explosive reactive armor module, the explosive material ignites. The ignition of the explosive material causes the two plates of the module to be driven apart. As the outer (or cover) plate is driven outward into the projectile, the outer plate damages, e.g., breaks or bends, the penetrator rod of the projectile. As the inner plate is driven inward away from the projectile, a longer path-length is created for the projectile, thereby reducing the chance that the projectile will perforate the vehicle&#39;s base armor. 
     SUMMARY 
     This disclosure generally describes a penetrator round assembly having a main penetrator rod and nose designed to penetrate explosive reactive armor. Using various techniques described in this disclosure, the penetrator round assembly perforates explosive reactive armor (“ERA”) cover plates and absorbs the initial energy from the moving ERA plates without significantly bending the main penetrator rod. 
     In one example, this disclosure is directed to a penetrator round assembly comprising a main penetrator rod comprising a tungsten alloy, and a solid nose engaged to the main penetrator rod. 
     In another example, this disclosure is directed to a penetrator round assembly comprising a main penetrator rod comprising a tungsten alloy, and a solid steel nose engaged to the main penetrator rod, wherein a ratio of a length of the main penetrator rod and a diameter of the main penetrator rod is greater than about 25. 
     In another example, this disclosure is directed to a penetrator round assembly comprising a main penetrator rod comprising a tungsten alloy, and a solid steel nose engaged to the main penetrator rod, wherein a ratio of a length of the main penetrator rod and a diameter of the main penetrator rod is greater than about 25, wherein neither the main penetrator rod nor the nose comprise depleted uranium, and wherein the main penetrator rod does not comprise cobalt. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an example penetrator round assembly, in accordance with this disclosure. 
         FIG. 2  is a longitudinal cross-sectional view of a portion of the example penetrator round of  FIG. 1 . 
         FIG. 3  is a schematic view of an example main penetrator rod and nose assembly, in accordance with this disclosure. 
         FIG. 4  is a graph depicting relative base armor penetration at various ranges for two penetrator round assemblies against ERA. 
         FIG. 5  is a graph depicting relative base armor penetration at various ranges for two penetrator round assemblies against semi-infinite rolled homogeneous armor (RHA). 
     
    
    
     DETAILED DESCRIPTION 
     In general, this disclosure describes a penetrator round assembly having a main penetrator rod and nose designed to penetrate explosive reactive armor. The penetrator round assembly includes a solid steel nose that is sufficiently robust to perforate explosive reactive armor (“ERA”) cover plates and absorb the initial energy from the moving ERA cover plates without significantly bending the main penetrator rod of the assembly. In addition, the main penetrator rod of the assembly has a greater bending stiffness than other penetrator round assemblies, thereby allowing the main penetrator rod of this disclosure to absorb the grinding interaction of moving ERA cover plates better than the other penetrator round assemblies. In addition, the penetrator round assembly described in this disclosure allows a user to engage enemy vehicles, e.g., tanks, at longer ranges as compared to other penetrator round assemblies. A longer engagement range increases the chance that the user will survive the encounter with enemy forces. 
       FIG. 1  is a perspective view of an example penetrator round assembly, in accordance with this disclosure. The example penetrator round assembly of  FIG. 1 , shown generally at  10 , includes combustible cartridge case system  12 , spring disc  14 , visibility tracer  16 , electric primer  18 , case base and seal assembly  20 , stick propellant  22 , propellant bag  24 , sabot  26 , nylon obturator  28 , anti-split ring  30 , main penetrator rod  32 , nose  34 , and fins  36 . In some examples, penetrator round assembly  10  is fired from the main gun of a tank. 
     In accordance with this disclosure, main penetrator rod  32 , in contrast to other penetrator round assemblies currently available, does not include depleted uranium. Rather, main penetrator rod  32  is comprised of an alloy containing a minimum of 90% tungsten by weight. The tungsten alloy of main penetrator rod  32  does not, however, include cobalt. 
     In addition and in accordance with this disclosure, nose  34  is comprised of solid steel, e.g., solid stainless steel. Nose  34  does not include depleted uranium. Because of its solid design, nose  34  will perforate ERA cover plates, ignite the explosive material, and absorb the initial energy from the moving ERA cover plates without significantly bending the main penetrator rod of the assembly. As the ERA cover plates move, the cover plates erode away nose  34  rather than damaging main penetrator rod  32 . In this manner, nose  34  can be thought of as a sacrificial element. That is, nose  34  takes the brunt of the effects of the explosion from the ERA, thereby allowing main penetrator rod  32  to continue straight without substantially bending or deflecting. While this disclosure refers specifically to a solid steel nose, it should be noted that nose  34  may be made of a material other than steel, provided that the material has a density that is greater than or equal to steel. 
     In contrast to nose  34 , other currently available penetrator round assemblies utilizes hollow steel noses. The hollow steel nose design acts as a windshield for the round and is used for aerodynamic purposes rather than for penetrating cover plates, as described in this disclosure. 
       FIG. 2  is a longitudinal cross-sectional view of a portion of the example penetrator round of  FIG. 1 . Nose  34  is joined directly to main penetrator  32 . In particular, main penetrator  32  includes threaded portion  38  upon which a portion nose  34  is attached. 
       FIG. 3  is a schematic view of an example main penetrator rod and nose assembly, in accordance with this disclosure. In the example depicted in  FIG. 3 , main penetrator rod  32  has a length greater than 630 millimeters (mm) and the nose  34  has a length of greater than 100 mm. In other examples, main penetrator rod  32  has a length greater than about 630 mm, preferably greater than about 650 mm, and more preferably greater than about 670 mm. 
     In addition and in accordance with this disclosure, main penetrator rod  32  has a diameter of greater than 24 mm. In one example configuration, main penetrator rod  32  has a diameter of about 25 mm. By utilizing a diameter greater than 24 mm, main penetrator rod  32  can absorb the grinding interaction of moving ERA plates better than rods with small diameters due to its increased bending stiffness. The bending stiffness of the main penetrator rod is proportional to the diameter of the road raised to the 4 th  power. For example a 25 mm diameter rod is approximately 67% stiffer than a 22 mm diameter rod (25 4 /22 4 =1.67). Importantly, the length-to-diameter ratio is greater than about 25 for the penetrator round assembly. 
     In addition and as indicated above, main penetrator rod  32  does not include depleted uranium. Rather, main penetrator rod  32  is comprised of a tungsten alloy. The alloy comprises at least 90% tungsten and further includes nickel and iron, but does not include cobalt. 
       FIG. 4  is a graph depicting relative base armor penetration at various ranges for two penetrator round assemblies against ERA. In particular,  FIG. 4  depicts predicted base armor penetration (y-axis) of a vehicle protected by ERA using a penetrator round assembly that has a diameter that is greater than about 24 mm and uses a solid steel nose, in accordance with this disclosure, relative to a penetrator round assembly that has a diameter less than 24 mm diameter and uses a hollow nose design over a range of 4 kilometers (km) (x-axis). In  FIG. 4 , the armor penetration is normalized by the penetration depth of the penetrator round assembly that uses a hollow nose design at 1 km. As seen in  FIG. 4 , the design with the solid steel nose, indicated by line  40 , outperforms the design with a hollow nose design, indicated by line  42 , by at least 20% over a range of about 1-4 km. That is, the design with the solid steel nose, as described in this disclosure, perforates the base armor to a depth that is at least 20% more than the hollow nose design over a range of about 1-4 kilometers (km). 
       FIG. 5  is a graph depicting relative base armor penetration at various ranges for two penetrator round assemblies against semi-infinite rolled homogeneous armor (RHA). In particular,  FIG. 5  depicts the predicted base armor penetration (y-axis) of a vehicle protected by RHA using a penetrator round assembly that has a diameter greater than about 24 mm and uses a solid steel nose, in accordance with this disclosure, relative to a penetrator round assembly that has a diameter less than 24 mm and uses a hollow nose design over a range of 4 km (x-axis). In  FIG. 5 , the armor penetration is normalized by the penetration depth of the penetrator round assembly that uses a hollow nose design at 1 kilometer (km). As seen in  FIG. 5 , the design with the solid steel nose, indicated by line  44 , outperforms the design with a hollow nose design, indicated by line  46 , over a range of about 1-4 kilometers (km). That is, the design with the solid steel nose, as described in this disclosure, perforates the base armor to a depth that is deeper than that of the hollow nose design over a range of about 1-4 kilometers (km). 
     Various aspects of the disclosure have been described. These and other aspects are within the scope of the following claims.