Abstract:
A resource is protected by an armor structure comprising a magnetic field such that the magnetic field will interfere with a warhead blast to weaken the blast. In particular, magnetic field will interfere with a molten metal jet from a shaped charge to disperse the jet, allowing subsequent layers of armor to absorb the jet energy without penetration. In one embodiment, the magnetic field is produced by a layer of magnetic material magnetized with the field lines perpendicular to the primary threat direction and typically parallel to the surface of the area to be protected. The magnetic material layer may include ferromagnetic (iron or steel, or other) layers to strengthen and contain the magnetic field, protect the magnetic material and act as additional armor layers. The magnetic layer is typically used in conjunction with an inner shield armor layer to absorb the diffused jet after passing through the magnetic layer.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 USC 119(a) of U.S. Provisional application 60/644,605 filed Jan. 15, 2005 by Fullerton, which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention pertains to the field of protection of a resource by dispersion and distribution of threat energy, more particularly by using protective armor. 
     2. Background of the Invention 
     There is a class of weapon that uses a shaped charge to form a high-speed molten metal jet to cut through armor as a method of armor piercing. Once through the armor, the molten metal continues to do damage to personnel or items such as explosives stored behind the armor. One typical example of such a weapon is a Russian made RPG-7 (Rocket Propelled Grenade) that is being used extensively in Iraq to inflict casualties to US troops. The RPG-7 has been successful in penetrating many inches of steel armor and is notoriously difficult to develop protection against. One method of protection involves the use of high temperature materials, but the temperature of the shaped charge is effective in penetrating even the highest temperature materials. Alternatively, more and more armor may be used, but the weight becomes prohibitive, especially for mobile assets such as tanks and armored troop carriers. Another type of armor is active armor that explodes on contact or near contact to prematurely set off the shaped charge to disperse the energy and reduce the effectiveness. Active armor, however, when used is spent, providing no protection until replaced. 
     Therefore, there is a need for an effective method and system of protection against a shaped charge type of armor piercing round, yet is light enough to be used for mobile equipment including tanks and armored troop carriers and maintains integrity and effectiveness when attacked repeatedly. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly, a resource is protected by an armor structure comprising a magnetic field such that the magnetic field will interfere with a warhead blast to weaken the blast. In particular, magnetic field will interfere with a molten metal jet from a shaped charge to disperse the jet, allowing subsequent relatively light layers of armor to absorb the jet energy without penetration. In one embodiment, the magnetic field is produced by a layer of magnetic material magnetized with the field lines perpendicular to the primary threat direction and typically parallel to the surface of the area to be protected. The magnetic material layer may include ferromagnetic (iron or steel, or other) layers to strengthen and contain the magnetic field, protect the magnetic material and act as additional armor layers. The magnetic layer is typically used in conjunction with an inner shield armor layer to absorb the diffused jet after passing through the magnetic layer. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
         FIG. 1A  illustrates an exemplary arrangement of layers of armor utilizing a magnetic layer to disperse a shaped charge in accordance with the present invention. 
         FIG. 1B  (prior art) illustrates the action of a shaped charge warhead on conventional armor. 
         FIG. 2  illustrates a perspective view of the magnetic and cladding layers of  FIG. 1A . 
         FIG. 3  illustrates an alternate layer stack including two magnetic layers in accordance with the present invention. 
         FIG. 4  illustrates an application of the invention and illustrates an angled orientation to the threat direction. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is an armor system comprising a magnetic layer that disperses and deflects a molten metal jet from a shaped charge to allow the jet to be stopped or rendered ineffective by a subsequent layer of ordinary armor or other protective material. The magnetic layer may be effective against any molten jet, regardless of temperature, because the principle depends only on the magnetic and conductive properties of the jet. The dispersion of the jet is derived from Lenz&#39;s law, a law of physics discovered by the German scientist H. F. E. Lenz in 1834. Lenz&#39;s law states that the electromotive force (emf) induced in a conductor moving perpendicular to a magnetic field tends to oppose that motion. Thus, in accordance with the present invention, the molten jet forms a moving conductor in the magnetic field of the magnetic armor. Thus, the magnetic field acts to slow and deflect the conducting molten jet of metal. In the process of slowing the jet, the jet is broken up and dispersed over a wide area, reducing the penetration capability of the jet. 
       FIG. 1A  illustrates an exemplary arrangement of layers of armor utilizing a magnetic layer to disperse a shaped charge in accordance with the present invention. Referring to  FIG. 1A , the armor comprises an outer cladding layer  104  having a hard surface  118 , a magnetic layer  102 , an inner cladding layer  106  and a shield layer  108  spaced from the inner cladding layer  106  by an expansion space  110 . An RPG  104  contacts the outer cladding layer  104  and triggers the shaped charge explosive  112 . The explosive then melts a metal core and propels the molten metal  114  forward to penetrate the armor. The molten metal  114  penetrates the outer hard surface layer  104  and then encounters the magnetic field layer  102 . Upon encountering the magnetic field layer  102 , the metal jet  114  is dispersed  116 . The jet may still be concentrated enough to penetrate the inner cladding  106 , but continues to expand  116  in the space between the inner cladding and the blocking shield  108 . Upon reaching the blocking shield, the blast  116  is dispersed sufficiently to be stopped by the blocking shield  108 . 
     The magnetic layer  102  is magnetized parallel to the surface of the area to be protected  124  and perpendicular to the expected direction of the metal jet  114 . This ensures that the incoming projectile  112  will have to cut through the magnetic lines of force contained within the magnetic armor  122  in order to reach the intended target  124 . When such a conducting projectile  114  begins to penetrate the magnetic armor  122  and begins to cut through the magnetic lines of force contained within, the projectile  114  will be subjected to a braking force that is in accordance with Lenz&#39;s law:
 
 F=Qv×B  
 
     where,
         F is the force vector;   Q is the charge;   v is the velocity vector of the charge;   B is the magnetic field vector; and   × is the vector cross product operation.       

     When a conductor, such as the molten metal jet  114 , penetrates the magnetic field  102 , electric currents are generated within the conductor  114  and are experienced as eddy currents, or shorted current loops. These currents are oriented to generate counter-acting magnetic forces that oppose the field contained within the armor, thus slowing the forward progress of the conductor. Since the conductor is liquid, the slowing of the jet allows portions of the tail to catch up with the leading portion causing the jet to change from a pencil shape to that of a mushroom with the head toward the front. The increased cross section of the jet  114  caused by passage through the magnetic field  102  makes the expanded jet  116  vulnerable to conventional shielding or armor  108 , since the pressure (force per square area) has been greatly reduced. Thus, the benefit of expanding the jet by using the magnetic layer is further enhanced by using a stopping shield  108  spaced from the magnetic layer to stop the expanded jet  116 . 
     The outer cladding layer  104  may provide multiple benefits to the armor assembly  122 . The outer layer  104  is a hard protective layer to protect the typically more fragile magnetic material  120  in the magnetic layer  102 . The outer layer  104  may also be a ferromagnetic material to enhance the magnetic field by providing a return path for the field and also may provide a magnetic shielding function to keep the strong magnetic field contained within the armor and minimize the long range effect of the magnetic field. The outer layer also provides a hard surface  118  to trigger warheads  112  just prior to the magnetic layer  102 . Further benefit may be obtained by having an additional outer layer (shown later in  FIG. 4 ) spaced from the outer cladding layer to trigger warheads early. In some embodiments, the outer layers  104  and  106  may not be necessary, permitting the magnetic layer  102  to be used alone. 
     The magnetic layer  102  may comprise a permanent magnetic material such as Neodymium Iron Boron (NdFeB) magnetic material or other magnetic material. NdFeB is also called Neodymium magnetic material in this disclosure. Neodymium magnetic material is inexpensive, lightweight, and relatively non-toxic. Neodymium magnets may be extremely strong, permitting minim thickness of the magnetic layer  102 . The magnetic layer  102  may be one continuous layer of magnetic material; however, magnetization may be greatly simplified by magnetizing smaller individual magnets  120  and assembling the multiple magnets  120  as shown in the  FIG. 1A . 
     An inner cladding layer  106  may be provided to hold and protect the magnetic material  102 . The inner cladding  106  may also be ferromagnetic and thus further contain and shield the magnetic field in a similar manner as the first cladding layer  104 . The inner cladding layer  106  may also be a factor in the spreading of the jet  114  and may be optimized in thickness and material for best performance. 
     The blocking layer  108 , if used, may also be the inner cladding layer  106 ; however, for best performance, the blocking layer  108  is an additional layer spaced from the magnetic layer  102  and cladding layers  104  and  106 . The spacing  110  allows the jet  114  to further expand  116  before impacting the blocking layer  108 . The blocking layer  108  is preferably high strength, high temperature material such as conventional steel armor. The blocking layer  108  is used to stop the expanded jet  116  of molten metal that emerges from the magnetic layer  102  after being velocity dampened. In the case of an add-on installation of magnetic armor, the magnetic layer assembly  122  may be added to the top of existing armor, using the existing armor for the blocking layer  108 . In some cases, additional material may be added to augment existing armor for the blocking layer  108 . 
       FIG. 1B  (prior art) illustrates the action of a shaped charge warhead  112  on conventional armor  126 . In contrast with the armor if  FIG. 1A , the conventional armor  126  of  FIG. 1B  does not disperse the shaped charge  114 , which penetrates the armor  126  and invades the protected space  124 . 
       FIG. 2  illustrates a perspective view of the magnetic  102  and cladding layers  104 ,  106  of  FIG. 1A . Referring to  FIG. 2 , the magnetic layer  102  comprises a plurality of magnets  120  assembled with the field in the same direction, parallel to the cladding plates  104 ,  106  and perpendicular to the direction  202  of the threat warhead as shown. Note that the warhead may come from any direction to penetrate the armor. 
       FIG. 3  illustrates an alternate layer stack including two magnetic layers in accordance with the present invention.  FIG. 1A  illustrates the basic layers that illustrate the principle of the invention; however, the system may be augmented with additional layers as needed for a particular application.  FIG. 3  shows an additional magnetic layer assembly  322  including cladding layers along with an outer protective layer  302 . Referring to  FIG. 3 , the armor system  300  comprises a first magnetic assembly  122  comprising a magnetic layer  102  and a first cladding layer  104  and a second cladding layer  106 . The armor system  300  further includes a second magnetic assembly  322 , also comprising a second magnetic layer  306  and third  308  and fourth  310  cladding layer. The second magnetic assembly  322  is spaced from the first magnetic assembly  122  with an air space  312  to allow expansion of the jet  114  to further weaken the jet  114 . The armor system  300  also includes a blocking layer  108  spaced from the second magnetic assembly  322 . Also shown is a top plate  302  to trigger the warhead  112  prematurely at a distance  304  from the first magnetic assembly  122 . As many magnetic layers and additional layers may be used as are needed for a particular application. 
       FIG. 4  illustrates an application of the invention and illustrates an angled orientation to the threat direction. Referring to  FIG. 4 , a tracked vehicle with existing armor  108  is fitted with magnetic armor  122 . The nose of the vehicle is designed to provide a wedge shape to deflect the threat in addition to preventing penetration of the armor. The armor  122  is arranged at an angle (not perpendicular) to the threat direction  202  to cause the threat to impact the armor at an angle. The angle impact will tend to deflect warhead energy and/or cause the threat to take a longer path through the armor  122 , effectively increasing the thickness of the armor  122 . In the angled armor embodiment, the magnetic direction may be preferably in a horizontal plane so that the magnetic vector is most nearly perpendicular to the threat direction. 
     CONCLUSION 
     Thus described is a new protective armor system especially adapted to defending against armor piercing shaped charge weapons, yet is light enough to be used for mobile equipment including tanks and armored troop carriers and maintains integrity and effectiveness when attacked repeatedly. 
     While particular embodiments of the invention have been described, it will be understood, however, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is, therefore contemplated by the appended claims to cover any such modifications that incorporate those features or those improvements which embody the spirit and scope of the present invention.