Explosive warhead

Aug. 25, 1964

M. A. COOK ETAL

3,145,656

EXPLOSIVE WARHEAD

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Aug. 25, 1964

3,145,656

M. A. COOK ETAL

EXPLOSIVE WARHEAD

Filed Aug. 14, 1959

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Sheets-Sheet 2

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INVENTORS.

MELVIN A. COOK WAYNE 0. URSENBACH

BY

ATTORNEYS.

United States Patent Office „ , 3,us,656

Patented Aug. 25, 1S64 ¹ 2

3,145,656 EXPLOSIVE WARHEAD

Melvin A. Cook and Wayne O. Ursenbach, Salt Lake City, Utan, assignors, by mesne assignments, to the United States of America as represented by the Secre- ° tary of the Navy

Filed Aug. 14, 1959, Ser. No. 833,652

Claims. (CI. 102—24)

This invention relates to detonation initiators for ex- io plosive warheads and more particularly to such devices for use with multiple shaped charge, rod, fragmentation and other types of warheads in which optimum performance depends upon the detonation front having a particular geometric configuration.

Toe. successful use of warheads of the type referred to depends largely upon the geometrical configuration of the impinging detonation front. A multiple shaped charge warhead, for example, has a metal liner having a multiplicity of conical portions which collapse and form radially outwardly projecting jets of metal when the warhead is detonated. The proper formation of such jets depends upon the substantially simultaneous initiation of the warhead explosive at all points along the cylindrical surface of a central bore extending between the ends of the warhead._ The initiators heretofore available have generated spherically expanding detonation fronts which cannot effect a simultaneous detonation along a cylindrical surface.

. It is an object of the present invention to provide a device to improve the performance of warheads of the type 30 referred to by generating a detonation front having an opitmum geometrical configuration.

It is a further object to provide a device for detonating a warhead having a cylindrical bore in a manner whereby detonation is effected simultaneously at all points between 35 the ends of the bore.

, ,°t_her objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal section of a multiple shaped charge warhead employing the present invention;

FIG. 2 is a section taken along line 2—2 of FIG. 1;

FIG. 3 is a side elevation of a guided missile in which the device of FIG. 1 is used;

FIGS 4A, 4B and.40 are diagrams illustrating sequential. conditions following the end detonation of an initiator which is loaded into a thin walled sleeve having uniform wall thickness;

FIGS. 5A, 5B and 5C are sections like FIG. 1, but shortened for illustrative purposes, and fllustrating generally corresponding sequential conditions of the device of FIG. 1;

FIG. 6 is a longitudinal section of an alternative form ot the present invention; and

FIG. 7.is a section taken along line 7—7 of FIG. 6.

Referring to the drawing and in particular to FIG 1 a multiple shaped charge warhead 10 consists of a generally cylindrical explosive charge 12 with a metal liner 14 thereabout, the liner being in the form of a multiplicity of conical portions 16 so constructed that when charge 12 is detonated each conical portion collapses and forms a jet of molten metal 18, shown in phanton lines, such warcommonly employed in an anti-aircraft missile 19, rIG. 3 and being old in the art. Explosive charge r2 has a cylindrical bore 20 extending between the ends thereof and is detonated by an axial initiator 22 comprising a cylindrical initiator explosive charge 24 loaded into a tapered sleeve 26 made of an inert material, such as mild steel, having the characteristic of delaying the propagation of a detonation front in proportion to its thickness along the path of the detonation front, as will hereinafter be further described. The sleeve has a thick end 28 decreasing in wall thickness along its length to a thin end 30 and is adapted for end detonation at thick end 28 by means of electric detonator 32. Tapered sleeve 26 is axially disposed within bore 20 between opposite ends thereof and held in a spaced relationship thereto by means of spacers 34, 36, providing an annular space 38 between tapered sleeve 26 and explosive charge 12, the annular space being important to the present invention for reasons which will be hereinafter apparent.

When a cylindrical charge of explosive 40, FIGS. 4A, 4B, 4C, similar, to initiator charge 24 except that it is loaded into a thin walled sleeve 42 having a uniform wall 15 thickness is end detonated, the charge does not detonate simultaneously along its length, there being instead a spherically expanding detonation front, to be hereinafter referred to as the “end on” detonation front, which starts at point A, the. point of detonation, and which propa20 gates end on within the charge along its length so that at sequential intervals after detonation such detonation front might be expected to assume the forms of broken lines 44α, 44b, 44c, which represent spherical surfaces expanding in the directions of the arrows X. There is also 25 a lateral detonation front starting near the intersection of the end on detonation front and the cylindrical boundary of the charge which propagates laterally outward in the form of a generally spherical expanding surface. Such latei ai front does not appear in FIG. 4A since the end on detonation front has not intersected the boundaries of the charge, but at the time interval represened by FIGS. 4B and 4C, such front might be expected to assume the form of broken lines 46b and 46c respectively, which represent generally spherical surfaces expanding in the direction of arrows X. FIG. 4C further illustrates the effect of charge 40 when employed as an axial initiator in a warhead charge 48 like warhead charge 12. Instead of effecting simultaneous initiation along the bore the generally spherical lateral front causes non-simultaneous detonation whereby the end of warhead charge 48 nearest to point A is detonated first causing the asymmetrical collapse of the conical portions 50 of the liner and providing undesired asymmetrically formed jets of metal 52 as shown. ’

It is apparent, from the foregoing explanation that a sleeve about an end detonation initiator charge is in the path of propagation of the lateral detonation front. It has been observed that if such sleeves are made of certain non-explosive inert materials such as steel, glass or brass 50 the propagation of the lateral front is delayed and the magnitude of delay is nearly proportional to the sleeve wall thickness. In fact, magnitudes of delay may be attained which are in the order of the time it takes for the end on detonation front io travel substantial distances along the length of the charge. For example, a mild steel sleeve having a wall thickness of the order of 0.5 inch about a cylindrical charge of cast pentolite 8.0 inches long and 0.625 inch in diameter can delay the propagation of the lateral front by a time interval of the order of 40 micro ₆₀ secs which is approximately the same interval of time it takes for the end on detonation front to travel from one end of the charge to the other. In the present invention the values for the taper in wall thickness of tapered sleeve are chosen to create a propagation delay gradient along ₆₅ the length of charge 24 such that the lateral front, which would otherwise assume the form of an expanding generafly spherical surface is caused to assume the form of an expanding cylindrical surface at the instant it imninges upon the surface of bore 29. The end on detonation 70 front propagates as in the aforesaid case of the initiator charge loaded into a thin walled sieeve and might be expected to assume the form of broken lines 54α, 54Z&gt;, 54c,

3,145,656

FIGS. 5A, 5B, 5C, expanding in the directions of arrows Y at sequential intervals after charge 24 is detonated at point B. The lateral detonation front does not appear in FIG. 5A since the end on detonation front has not intersected the boundaries of the charge. Nor does it appear in FIG. 5B having been delayed by the delay gradient produced by sleeve 26. However, as shown in FIG. 5B sleeve 26 expands and breaks up in the region generally behind broken line 54b, the advancing end on detonation front, causing effects including a shock wave and products j of sleeve expansion and break up which propagate radially outward in the annular zone 56 about the portion of the sleeve which has expanded and broken, up. These effects are undesirable in that they precede the detonation wave and will physically damage an explosive in their patn, and in the case of a typical brittle warhead explosive will break it up before the detonation front reaches it causing failure of detonation. Such undesirable effects are, however, confined within a certain radial distance beyond the sleeve. The purpose of annular space 38 is to provide a buffer zone about tapered sleeve 26 to permit such outwardly propagating effects to expand within such radial distance or space without damaging the warhead charge. Finally, at the time interval after detonation represented by FIG. 5C, the lateral detonation front assumes the form of broken line 53, a generally cylindrical surface expanding in the direction of the impinge arrows Ύ, effecting substantially simultaneous initiation at all points along bore 20, thereby simultaneously and symmetrically collapsing the conical portions 16 of the liner along the length of the warhead forming metal jets 18.

FIGS. 6 and 7 illustrate a multiple shaped charge warhead 60 embodying several variations in the basic principles of the invention, such warhead bemg similar to the device heretofore described except as will be mentioned. A cylindrical initiator explosive charge 62 is loaded into an inner sleeve 64 made of an inert material having the same characteristics as the material employed in the sleeve of the device heretofore described. However, inner sleeve 64 has a double taper with maximum wall thickness at the midpoint between its ends and minimum wall thickness at its ends, the initiator charge being adapted for detonation at the midpoint by means of electric, detonator 66 so that the sleeve wall thickness decreases in either of the opposite directions away from the. point of detonation along its length. It is apparent that such arrangement is the equivalent of placing two end detonated single taper sleeves end to end, with the resultant effect that the device is canable of effecting simultaneous detonation for a warhead of twice the length that can be detonated with a single taper sleeve. An outer sleeve 68 is disposed concentrically about inner sleeve.64 with an annular space 70 therebetween providing a buffer zone to prevent damage to the outer sleeve by the outwardly propagating effects heretofore described. Outer sleeve 68 is aluminum and has a double taper similar to that of the inner sleeve except that the .taper is formed along its inside wall surface, such sleeve serving to effect a second delay gradient in the propagation of the lateral detonation front, it haying been found that such, outer sleeve results in a margin of improvement in attaining a more nearly perfect simultaneous detonation along the length of bore 72 of the explosive charge 74. As with the other sleeves heretofore discussed, undesirable effects may take place within a certain radial distance beyond the sleeve, and a buffer zone is necessary thereabout. It is desirable that the space 65 taken up by the outer sleeve and its buffer zone be. as small as possible to conserve pay load, volume. It has been found that such space can be substantially reduced, if instead of making the outer sleeve of the same material as the inner sleeve, it is made of an inert material such as 70 aluminum which has the characteristics of effecting a delay upon a lateral detonation wave in proportion to its thickness but with the magnitude of such delay substantially less than that attainable with steel, glass, brass, the inert materials heretofore mentioned. A loosely packed 75 explosive 76 such as tetryl with a density of 1.0 gram per cubic centimeter is disposed between the outside wall surface of outer sleeve 68 and warhead charge 74, such explosive being compressible under the outwardly propagating effects and therefore serving as a buffer zone. Employing such explosive in the otherwise void space also adds a margin of explosive energy to the overall explosive capability of the warhead. .

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.