United States Patent 3598051

The present invention comprises a spherical explosive device that, by selive multipoint initiation, concentrates its energy in a beam along any of several aiming axes. Aiming is accomplished by electronically selecting the proper group of detonators, thereby eliminating the necessity of physically aiming the charge as is required in all other focused blast devices. Once fired, these initiators cause a nearly cylindrical detonation wave, converging on the focusing axis, which forces the explosion products out along this axis and causes the warhead energy to be concentrated in the direction of a target rather than being omnidirectionally dissipated as in conventional warheads.

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F42C19/095; (IPC1-7): F42D1/06
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Primary Examiner:
Pendegrass, Verlin R.
I claim

1. In an explosive device, the combination of

2. The explosive device of claim 1 wherein said charge takes the shape of a sphere.

3. The explosive device of claim 1 wherein said detonation initiation means are disposed within the charge.

4. The explosive device of claim 1 and further comprising

5. The method of producing a directed destructive blast utilizing a generally spherical charge of explosive material having pairs of diametrically oppositely disposed detonation initiation means located on the surface of said charge, said method comprising

6. The method of claim 5 and further comprising

7. In an explosive device, the combination of

8. The explosive device of claim 7 wherein said detonation initiation means are disposed within the charge.

9. The explosive device of claim 7 and further comprising


1. Field of the Invention

Although development of the present invention has proceeded in response to the problems involved in destroying or disabling airborne vehicles, successful application can readily be made to any number of environments, such as antiinstallation or antipersonnel situations. The most pertinent application arises in combination with a guided missile system as a method for preventing near misses of unfriendly aircraft. The probability of scoring a direct hit on an airborne object traveling at speeds exceeding that of sound is considerably less than one, even with sophisticated antiaircraft missile systems. In order to inflict crippling damage in a near miss situation, it would be desirable for the missile to explode while in proximity to the target and to focus destructive fragments and blast pressures in the direction of the target. Accordingly, a sensing device, preferably contained in the missile itself, capable of determining proximity to the target will indicate to the missile when it is within range of the target and will cause the missile warhead to explode, directing fragments and blast effects toward the target aircraft. Directing the blast not only causes the mass projected into the area of the target to be greatly increased, but also substantially augments the fragment velocity in the direction of the target.

2. Description of the Prior Art

Devices which exist for directing the blast of a warhead include the electrically controlled directional warhead according to Witow disclosed in U.S. Pat. No. 3,136,251. Plates disposed internally of the warhead are selectively charged on command from any well-known device capable of sensing proximity to a target. The plate oriented toward the target is charged negatively, thereby attracting positively charged gaseous ions produced in the deflagration phase of the explosive process. Free electrons thus produced migrate toward the other plates which are charged positively. This migration tends to set up a shock absorbing layer or cushion around the inner surface of the explosive container which is identified with the positive plates. This cushion absorbs the shockwave occurring during the detonation phase of the explosive process for an instant of time, long enough for the uncushioned area of the container, that is, the area where the negative plate is located, to receive the blast shock an instant sooner and with sufficient severity to fragmentize that area of the container first. Migration of the positively charged gaseous ions in the direction of the negative plate enhances blast flow in that direction.

Zernow et al., in U.S. Pat. No. 3,156,188, discloses a spherical warhead for controlling fragment size by providing an inert perforated barrier encasing the explosive and interior to the metal warhead casing. On detonation, the resulting shockwave is interrupted by the barrier but continues unhindered through the perforations of the barrier causing preferential fractures in the casing. It can be easily seen that a directed blast could be accomplished by perforating only a select portion of the barrier. However, the warhead itself would have to be physically rotated on intercept of a moving target in order to insure that the blast be directed toward the target.

The present invention proposes the use of a spherical charge initiated at a number of points in a local area on the surface of the charge. By electronic selection of the appropriate initiation points and initiation times, the blast is caused to be concentrated along any desired axis of the sphere. The instant invention provides practical and reliable focusing of blast effects in contrast to the device of Witow and avoids the requirement for mechanical orientation of the warhead, for which intercept time is too short, of scored and grooved fragmentation devices such as the device of Zernow.


Focused blast is the term applied to explosions that, by method of initiation, shape of explosive charge, or method of confinement, are directed in a beam or are uniformly distributed in a plane. For practical applications, the explosive charge should have a symmetry that permits producing the blast in any desired direction.

Many arrangements or patterns for the initiating means disposed on the surface of or within the charge may be employed, depending on the directionality desired in the blast. Time delays between initiation on different portions of the explosive are desirable. Also, for some applications a graded composition of the explosive varying from the surface toward the center of the charge may be useful. Hollow charges and combinations of explosive and other material may also be employed.

The concept is not restricted to spherical charges. With appropriate initiation point selection and detonation timing, shapes such as cylinders, cones, or polyhedrons could be utilized.

Accordingly, it is an object of this invention to provide a warhead which is directionally explosive.

It is also an object of this invention to increase the concentration of destructive fragments in the area of a target and to augment the fragment velocity in that direction.

A further object of the invention is to provide a spherical warhead whose blast can be concentrated along any desired axis of the sphere without mechanical movement, through electronic selection and control of initiator points appropriately arranged about the center or axis of the warhead.

Yet another object of the invention is to increase the damage probability of a missile system carrying the invention by increasing the effective range of the warhead.

Another object of the invention is to provide a directionally explosive warhead which is compatible with aircraft intercept kinematics.

Other objects and attendant advantages will become more readily apparent and more easily understood by reference to the following description of the preferred embodiments.


FIG. 1 schematically depicts a top view of a spherical configuration of the present invention as seen along the z-axis, detonation waves being seen converging on the z-axis;

FIG. 2 schematically depicts the device of FIG. 1 as seen along the y-axis and indicating initiation point location and firing sequence;

FIG. 3 depicts the present invention as a sphere of radius a having nine firing axes, the center of the sphere being at the origin of an xyz coordinance system, the z axis of which system is intended to coincide with the axis of a missile on which said invention is mounted; and

FIGS. 4a, 4b and 4c illustrate the method of axis rotation utilized to determine the location of initiation points for certain of the firing axes .


Referring to the drawings and particularly to FIGS. 1 and 2, a sphere 1 of explosive composition, shown from a top and from a side view, has a radius, a, and twelve initiation points 2. The four points 2 lie in the equatorial plane, i.e., the x-y plane, and are initiated first, at t=0, and the eight points 2 lying in the two parallel planes, one above and one below the equatorial plane, are to be initiated later at t=td. The delay time, td, is the time required for the detonation wave from initiation point A, initiated at t=0, to reach the line B-B'.


where D is the detonation velocity of the explosive and φ is the angle shown in FIG. 2. The converging detonation waves, so produced, will focus the explosion products along the z axis.

Such a device has only a single focusing axis. By adding more initiation points 2, the beam can be aimed along any desired axis simply by firing the proper combination of detonators. The method of locating these initiation points is hereinafter described. Location of initiation points should not be restricted to the surface of the charge. For certain applications, disposing the detonators within the charge proves advantageous.

A practical focused blast warhead must be capable of firing along any of several possible axes. The proper firing axis is determined by the relative attitudes of the missile and target at intercept. When these attitudes are optimum for producing target destruction, the appropriate group of detonators is triggered electronically. The entire system, being electronically controlled and fired, would have a nearly instantaneous response.

A systematic method of locating the initiation points has been developed. Such initiation will show that the points 2 occur in pairs which are reflections of each other through the center of the sphere 1. These paired points are always fired simultaneously and certain of them are always delayed, which simplifies the switching network 3 and sensing indicator 4 required to choose them.

A sphere of radius a, having nine firing axes, i.e., axes (1--9), is shown in FIG. 3. The center of the sphere 1 is at the origin of the xyz coordinate system and the z axis coincides with the missile axis. If the z axis were the firing axis, the 12 initiation points would be located at ##SPC1##

where column matrix notation is used for the coordinates. Now let z' in the x'y'z' system be any other firing axis. The initiation points for this axis will have the same coordinates in the x'y'z' system as the initiation points for the z axis in the xyz system. Now the x'y'z' axis can be formed by rotating the xyz axis and the most systematic method of performing this rotation is the method of Euler angles found in Goldstein's Classical Mechanics, Addison-Wesley, 1956. In this approach, the rotation is decomposed into three separate ones as in FIGS. 4a, 4b, and 4c.

1. The xyz system is rotated counterclockwise about the z axis through an angle φ, resulting in the intermediate ξηζ system.

2. The ξηζ system is then rotated counterclockwise, through an angle θ about the ξ axis to produce the ξ'η'ζ' system.

3. Finally, the ξ'η'ζ' system is rotated counterclockwise about the ζ axis through angle Ψ, resulting in the x'y'z' system.

Thus in matrix notation ##SPC2## and the matrix A is the product of the three separate rotation matrices B, C and D where, ##SPC3##

Table I given at the end of this description shows the Euler angles φ, θ and Ψ for the firing axes indicated in FIG. 3. Ψ is zero for all of these, so B reduces to the identity matrix. Thus A=CD or

Now recall that x' is known and x is sought; therefore,

x=A-1- x'

but A is an orthogonal matrix; so, its inverse is equal to its transpose; i.e.,

A- 1 =AT.


x=AT x'


The value of AT for each firing axis found by substituting in the values of φ and θ that appear in Table I. The resulting transformation matrices for each of the nine firing axes are tabulated in accompanying Table II.

By using these matrices and the coordinates of the firing points in the primed system given in Eq.(A1), the positions of the initiation points in the xyz system can be found from Eq.(A8). These are collected in Table III, Table IV gives the initiation points and their firing order for each firing axis.

By careful examination of the initiation points in Table III, it is seen that they are comprised of 21 pairs of points, and that the pairs are reflections of each other through the origin. Furthermore, Table IV shows that the pairs are always fired simultaneously; the ones on the firing axes; i.e., those numbered one through nine, being fired either with or without delay and the others; viz., the ones numbered 10 through 13 and the lettered ones, always being delayed.

The application of the present invention is not limited to an antiaircraft capability. The invention could apply to any situation where a directed blast would be advantageous. Such a situation is seen for armor-piercing projectiles, for antipersonnel projectiles, or for mines and depth charges.

Such a localized detonation prevents the waste of energy and particles of an omnidirectional explosion by directing most of the energy of the explosion, as well as the particles of the explosion, toward the target or targets. The present invention conserves explosive energy needed for a particular purpose and gives increased range and destructiveness to a particular charge.

Many modifications of the present invention are possible in light of the above description. It is believed apparent that the present device is not confined to the specific use or uses described herein; nor is the the invention limited to the particular construction described in these embodiments, it being understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. ##SPC4## ##SPC5## ##SPC6## ##SPC7##