US3498224A - Fragmentation warhead having circumferential layers of cubical fragments - Google Patents

Description

March 3, 1970 P. E. CORDLE. ETAL 3,498,224

FRAGMENTATION WARHEAD HAVING CIRGUMFERENTIAL Filed Oct. 4, 1968 LAYERS OF CUBIC-AL FRAGMENTS 3 Sheets-Sheet 1 32 32 I2 33 I9 I 44 43 .l 42 4| F I6. I

INVENTORS. PAUL E. CORDLE RICHARD P. BIRGE BY ROY MILLER ATTORNEY. GERALD F. BAKER AGENT.

March 3, 1970 P. E. CORDLE ETAL 3,493,224

FRAGMENTATION WARHEAD HAVING CIRCUMFERENTIAL LAYERS 0F CUBICAL FRAGMENTS Filed Oct. 4, 1968 3 Sheets-Sheet 2 OO- Om 00 Oh Ow u402 20:02:- unbu manhunt O 1 Ou On 0* On March 1970 P. E. CORDLE ETAL FRAGMENTATION WARHEAD HAVING CIRCUMFERENTIAL LAYERS 0F CUBICAL FRAGMENTS 3 Sheets-Sheet 5 Filed Oct. 4, 1968 o. omw E 000 n A tor-bum 44200 20mm wumau m0 m30 KDOL wmm :0 m0 wioz 2 393 .3 23m 2.: a um: mumno to :2.

M20 0 uw u United States Patent Of US. Cl. 102-67 4 Claims ABSTRACT OF THE DISCLOSURE A missile warhead comprising an explosive charge surrounded by varying members of circumferential layers of steel cubes resulting in varying the charge to metal ratio with respect to the warhead longitudinal axis which yields a predictable fragment beam pattern made up of fragments having varying velocities.

GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention relates to warheads and particularly to warheads incorporated in missiles and more particularly to a guided missile warhead partially surrounded by preformed metal cubes. The weapon is a passive, air-to-surface, all-weather weapon designed to seek out and destroy certain enemy targets. It requires a warhead that will be effective against such targets, withstand all designated operational environments, be safe to handle, store and transport, and provide properly designed interfaces to allow assembly to adjacent components. The basic physical characteristics of the warheads are shown in the accompanying drawing as will be explained later.

Explosive warheads have, of course, been designed with accompanying means for producing fragments and shrapnel of various types and for various purposes. The former explosive devices were primarily designed for anti-personnel weaponry. However, such fragmentation explosive devices do have industrial applications, for example, in oil well perforation. In either case, fragmentation which is uncontrolled is not desirable because production of indiscriminate fragmentation is inefficient and wasteful of explosive material.

Increased efficiency of a fragmentation weapon against targets for which it was designed depend upon control of fragment size and pattern. Consequently, the size, weight, distribution and charge-to-metal ratio have been carefully considered in designing a warhead according to the present invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a longitudinal cross sectional view of a warhead according to the present invention;

FIG. 2 is enlarged view of a detail of the device of FIG. 1;

FIG. 3 is an exploded view of the warhead of FIG. 1;

FIG. 4 is a graphical showing of the fragment pattern in a static firingof the Warhead;

FIG. 5 is a graphical illustration of the fragment pattern in a dynamic firing of the warhead; and

FIG. 6 is a graph showing the typical conditional kill probability of a warhead according to the invention against a selected target.

3,498,224 Patented Mar. 3, 1970 DETAILED DESCRIPTION OF A PREFERRED EM- BODIMENT OF THE INVENTION A warhead according to the invention is generally designated by numeral 10 in FIG. 1 and is shown as a missile warhead section. The warhead section 10 is designed for use in a passive air-to-surface all-weather weapon designed to seek out and destroy certain enemy installations. The weapon requires a warhead that will be effective against such targets, withstand all designated operational environments, be safe to handle, store and transport, and provide properly designed interfaces to allow assembly to adjacent components.

As shown in FIG. 1, an explosive charge 12 is fitted with a conventional arming and booster device 16 and the assembly is fitted into an outer casing 18. The forward end of the warhead 10 is ogival in form, leaving a space 21 between warhead 10, casing 18 and front plate 23, which space is preferably filled with a foam material 20. A stout pad 22 is inserted between the warhead and the forward end of casing 18. Because electrical wiring for guidance controls is often necessary, the warhead 10 is shown with an electrical conduit 28 including connector ends 24, 26 and passing through the warhead 10. Surrounding the explosive 12 is one or more layers of preformed cubical fragmentation elements 32.

As shown in FIG. 2 these fragmentation elements 32 may be separated between sections by a plurality of starting devices 30, 30a, etc. As shown in FIG. 3 the warhead shown is divided into five sections. The explosive in the first section 41 is surrounded by the case 18 only. Beginning with section 42, however, one or more rows of 7 inch steel cubes, for example, surround the explosive. Section 43 has two layers of cubes, section 44, three layers and the ogival section 45 has four rows.

OPERATIONAL CONDITIONS Warhead 10 is required to function effectively under a wide variety of missile terminal conditions. The expected Circular Error Probable (CEP) for the missile is 30 feet. Angular approach to the target will vary between 20 to 60, with the normal distribution of approach angles centered about 45. Terminal velocities will vary between 690 and 1,100 feet per second, as dictated by launching conditions. Target heights will be variable.

Analysis of a number of possible targets considered for attack by the warhead has indicated that a revetted radar, structurally similar to the US. Radar System SCR/584, is the least vulnerable. Primary efforts to establish target vulnerability criteria for warhead analysis have involved the screen and pedestal assembly of the SCR/584 with no consideration given to the van or mounting stand because of the relative ease with which they might be protected.

After careful inspection and measurement of the SCR/ 5 84 radar, the following target vulnerability factors in terms of vulnerable areas evolved:

(l) Pedestal assembly fully exposed and unarmored- (2) Pedestal assembly fully armored with /8-11'101'1 steel, but transmission lines, cables, and potentiometer housings unmodified-1.0 ft.

(3) All vulnerable areas protected, except the dipole and feed horn assemblies0.25 to 0.50 ft.

These are considered to be average areas as projected perpendicular to the line of flight of the fragment beam, regardless of screen orientation. Vulnerable area is defined as any portion of the assembly that is equivalent to 0.125- inch thick armor plate or less.

3 DESIGN APPROACH A feasibility study, involving several types of warheads, preceded the selection of the variable charge-to-metal, directed fragmentation warhead. The development of this concept involved two phases: the evolution and evaluation of an analytical model and a series of static and dynamic tests to empirically substantiate the design.

ANALYTICAL MODEL The design of the analytical model involved the evaluation of the cumulative effects of five separate warheads joined in tandem, as shown in FIG. 3. Each warhead section employs a uniform charge-toqnetal ratio, and upon detonation results in a specific initial fragment velocity Whose vector leads a plane perpendicular tothe longitudinal axis by approximately 7. Values of initial fragment velocities in each warhead section were determined from the Gurney solid cylinder relationship:

fl 1+O.5 C/M and the Gurney spherical relationship:

Where V and V =Initial fragment velocity. a=Explosive energy C/ M :Charge-to-metal ratio equations. As may be expected from these conditions, the

fragmentation pattern presented to an area some uniform distance away (large in proportion to the size of the warhead) will be extremely dense, but will be presented in a relatively narrow beam (in the order of 10 wide).

Since the missile can approach its target in such a variety of terminal situations, and the fixed-angle influence fuze possesses a functional tolerance that is related to target pulse rates and internal circuitry, the warhead must retain a nearly uniform capability over a relatively wide angular range. From the extreme conditions of low velocity approaches and high frequency pulse rates to high velocity and slow pulse rates, this angular range was determined to be from 55 to 75 off the longitudinal axis when the nominal fuze function angle of 70 was employed.

FIG. 5 demonstrates the manner in which the variable charge-to-metal warhead satisfies the limits of the missiles functional tolerances. The dynamic spread or fanning effect of various sections in the warhead is realized from the addition of missile and fragment velocity vectors, resulting in a relatively uniform capability. As may be seen by considering only one section of the warhead, this effect would not be realized from a cylindrical warhead employing only one charge-to-metal ratio.

In the event that the missile approaches the target with a shallow approach angle and falls short, it is possible that ground intercept may occur before the fuze intercept angle is real z d. A situation sue as h W l s l n a contact burst, requiring utilization of the fragment pattern from the ogival section of the warhead. While the fragmentation from the ogive is less effective than that of the fuze function zone, a limited capability is retained.

With the compatibility of the warhead and missile performance characteristics established, conditional warhead effectiveness statements could be made for a variety of terminal situations. A program was written for the IBM 7090 computer that resolves effectiveness problems in terms of kill probability versus miss distance for any missile terminal aspect desired. Program input variables include: target height, target vulnerable area, missile approach angle, missile terminal velocity, effective fuze function angle, and fragment size. FIG. 6 shows a typical set of conditional kill probability curves that result from the conditions noted. Numerous runs have been made to specify the proper choices of fragment size, effective fuze function angle, delivery tactics, etc.

DESIGN EVALUATION At the completion of the analytical program a number of warheads were fabricated to the design predicted by the computer program. These heads were fired both statically in an arena of witness plates and dynamically from the track at the Naval Weapons Center K-2 Range. The fragment patterns and velocities were assessed and fed into the computer program. Except for a minor change in the ogival radius, the warhead authenticated the pr dicted design and allowed the disclosure of the functional warhead design in June 1962.

We claim:

1. An ex losive fragmentation warhead comprising:

an ogival section, and

a plurality of substantially cylindrical sections;

said ogival section and all save one of said substantially cylindrical sections being surrounded with one or more rows of cubical fragments;

separator means between rows of fragments around said sections;

said explosive being enclosed in a substantially cylindrical housing; and said housing including means for attaching said housing to adjacent components to form a missile.

2. An explosive warhead according to claim 1 wherein the fragments are of metal and each section has a uni form charge-to-metal ratio resulting in a specific fragment velocity vector leading a plane perpendicular to the longitudinal axis of the warhead by approximately 7 3. An explosive warhead according to claim 1 wherein said fragments are of metal and are individually coated with plastic.

4. An explosive warhead according to claim 2 wherein said fragments are individually coated with plastic.

References Cited UNITED STATES PATENTS 1,272,984 7/1918 Mutro 10267 2,281,213 4/1942 Thaden 10256 X 2,972,949 2/1961 MacLeod 102-67 3,263,612 8/1966 Throner "102-67 3,298,308 1/1967 Throner 10267 FOREIGN PATENTS 1,202,477 7/1958 France.

BENJAMIN A. BORCHELT, Primary Examiner CHARLES T. JQRDAN, Assistant Examiner

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