Abstract:
A fuse and a fusing method comprising initiating detonation of a first booster comprising a circular shaped charge and thereby causing detonation of a second booster.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of the filing of U.S. Provisional Patent Application Ser. No. 61/029,435, entitled “Ring Booster for Fuze”, filed on Feb. 18, 2008, and the specification and claims thereof are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not Applicable. 
     COPYRIGHTED MATERIAL 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention (Technical Field) 
     The present invention relates to boosters for fuzes. 
     2. Description of Related Art 
     Current booster designs for fuzes are configured to provide axial and/or radial initiation of main explosive charges. A fuze design that will survive the environment of hard target penetration (with protective shock absorbing/encapsulating shroud) cannot reliably initiate the main charge when an axial FZU (Fuzing Unit) power connection is required in the explosive train design. The present invention provides a solution for this problem. 
     A typical prior art fuzing configuration  10  is shown in  FIG. 1 , comprising fuze/fuze well/fuze retainers  12  (e.g., comprising 0.11″ thickness steel), isolator material  14  (e.g., comprising 0.365″ thickness polyrubber), fuze cases  18  (e.g., of 0.11″ thickness stainless steel), first booster  16  (e.g., 1.8″ diameter explosive material), and second booster  20  (e.g., 2.42″ diameter explosive material). 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention comprises a fuze and a fuzing method comprising: initiating detonation of a first booster comprising a circular shaped charge; and thereby causing detonation of a second booster. In the preferred embodiment, the first booster comprises a central conical portion surrounded by a raised ring. A detonation shaper is employed between the boosters, preferably conforming substantially to the shape of the first booster and/or comprising copper and/or molybdenum. The first booster preferably comprises PBXN-5 explosive, and the second booster PBXN-9 explosive. The second booster can comprise a central void, most preferably sized to permit passage of a FZU power connection therethrough. Alternatively, the second booster can comprise no voids and/or an insensitive, shock resistant, explosive. 
     Further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings: 
         FIG. 1  is a cutaway view of a prior art explosive device with two boosters for the fuze; 
         FIG. 2  is a cutaway view of the booster configuration according to the invention; 
         FIG. 3  provides simulation results for the device of  FIG. 2  at time zero; 
         FIG. 4  provides simulation results for the device of  FIG. 2  at about time 1.2×10 −5  sec; and 
         FIG. 5  provides simulation results for the device of  FIG. 2  at about time 1.5×10 −5  sec. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is of a fuze, a method of making a fuze, and a fuzing method preferably for hard target penetrators. The fuze of the invention survives the penetration and perforation of hard (reinforced concrete) targets and functions in particular with respect to voids deep beneath these targets, e.g., rooms protected by many feet of reinforced concrete. Although the explosive train caused by the invention will reliably initiate the solid booster and main charge of the penetrator, the fuze design is preferably usable with current penetrators which utilize a power source known as an “FZU” which connects to the front of the fuze. To enable this connection to be made, the second booster preferably has a central void area for the FZU connection. These configurations cannot be reliably initiated with standard booster configurations, as the first booster output is not sufficient to both perforate the isolation material and cause high order detonation of the second booster (with the center void) and the main charge. 
     The fuze of the invention preferably has at least two boosters, most preferably two. The output of the first booster must project the detonation wave through the protective material and into the second booster at sufficiently high levels to detonate the second booster and main charge. With the center-line void area for the FZU connection, the major portion of the first booster output, whether with conventional or flyer-plate output as found in conventional booster designs, has reduced capability to initiate the second booster and the main charge. The invention provides a novel output for the first booster in the form of a ring-shaped Circular Shaped Charge which will focus the output toward the circular-shaped second booster, focusing and concentrating the detonation output of the first booster into the second booster after passing through the isolation material. Calculations using CTH hydro code indicate that effective initiation of the second booster and main charge is achieved with this unique configuration. This approach is also useful with the HTVSF (Hard Target Void Sensing Fuze). 
       FIG. 2  illustrates the preferred device  30  of the invention, comprising first booster  32 , second booster  34  (with central void with FZU power connection  38 ), and detonation shaper  36 . The first booster preferably has a central conical portion  32 ′ surrounded by a raised ring  32 ″, as illustrated. The detonation shaper preferably corresponds in shape to the first booster, and preferably comprises copper, molybdenum, or other shaped charge liner material. The first booster can be any appropriate fuzing explosive, but preferably comprises PBXN-5 explosive. Similarly, the second booster can be any appropriate fuzing explosive, but preferably comprises PBXN-9 explosive. 
     As shown in  FIGS. 3-5 , CTH hydrocode (Sandia National Laboratories) modeling of the invention of  FIG. 2  utilizing the circular shaped charge booster output indicates adequate shock margin for successful high order initiation of the main charge. 
     The present invention enables utilization of the fuze in penetrators requiring forward axial FZU connections which would not otherwise be viable weapons. The cost of implementing the new design is minimal, and there is no volume or weight increase. For penetrators having protective shrouds around the fuze and first booster, but not employing a FZU as the power source, the second booster does not require a hole through the axis and also functions better with the shaped first booster output according to the invention. Other shapes such as shallow cones are possible as well. While the preferred embodiment of the invention is directed to a fuze employed with projectiles designed to penetrate hard and/or deeply buried targets, the invention is also useful in fuzes of any sort. A further application of the shaped booster output of the invention is for initiation of insensitive (shock resistant) explosives because reduced sensitivity explosive fills what would otherwise require an unnecessarily large booster to initiate. 
     Note that in the specification and claims, “about” or “approximately” means within twenty percent (20%) of the numerical amount cited. 
     Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.