US3731633A

US3731633A - Air-to-surface missile

Info

Publication number: US3731633A
Application number: US00584943A
Authority: US
Inventors: D Davis
Original assignee: US Air Force
Current assignee: US Air Force
Priority date: 1966-10-05
Filing date: 1966-10-05
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

An improved missile, which when in stabilized flight is constituted of upper and lower longitudinal casing portions, a warhead including explosive material confined to the lower casing portion and forming part of the last-mentioned casing portion, the outer surface of the warhead being fragmentized and at its front end, takes the shape broadly of a semicylinder which tapers down in depth (as measured from the horizontal axis of the semicylinder) along the length of the warhead to a curved shape at the rear end but having less depth than at the front end. The same thickness of explosive material is contained in the warhead throughout its length. Thus, the outer surface of the warhead projects upwardly toward said horizontal axis as its rear end is approached to cause the exploded fragments to leave in a direction rearwardly of the warhead in order to increase the lethal effect of the missile.

Description

United States Patent 1 Davis [54] AIR-TO-SURFACE MISSILE [75] Inventor: Dale M. Davis, Freeport, Fla.

[73] Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, D.C.

[22] Filed: Oct. 5, 1966 [21] Appl. No.: 584,943

521 US. Cl .Q ....l02/67 [58] Field of Search ..102/24, 56, 67, 68, 102/493, 49.6

[ 1 May 8,1973

Primary ExaminerVerlin R. Pendegrass Attorney-Harry A. Herbert, Jr. and Herbert H. Brown [57] ABSTRACT [56] References Cited than at the front end. The same thickness of explosive UNITED STATES PATENTS material is contained in the warhead throughout its length. Thus, the outer surface of the warhead pro- 2,337,765 12/1943 Nahimey ..l( )2/67 X jects upwardly toward said horizontal axis as its rear MacLeOd end is approached to cause exploded fragments to 3,145,656 8/1964 Cook et al. ..l02/56 x leave in a direction rearwardly of the warhead in order to increase the lethal effect of the missile.

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AIR-TO-SURFACE MISSILE The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to air-to-surface missiles, but more particularly, to the warhead portion contained within the fragment type of weapon.

An object of the invention is to provide a warhead in which the direction that the fragments take during the explosion or burst is controlled in order to increase the lethal area at ground level.

When a missile or bomb is exploded on the ground, and is without velocity, the lethal area of the fragments is theoretically at a maximum. However, a good percentage of the fragments would be driven into the ground and therefore would have lost their effectiveness. On the other hand, should the missile be dropped vertically and exploded on contact with the ground, the lethal area would still be quite large but a greater number of fragments would enter the ground. In practice, neither of these conditions would actually obtain because the missile is generally delivered by plane or under its own propulsion and the missile would reach the burst point at some angle with respect to the vertical axis and with some velocity. These conditions affect the lethal area in an inverse sense in that the smaller the angle at the point of burst with respect to ground, the less becomes the lethal area obtained, whereas the latter becomes greater as I the velocity is increased. However, the angle of delivery is found to be more sensitive than the velocity at the point of delivery in obtaining the optimum area of destruction at ground level. Under warfare conditions, it is sometimes more feasible, in order to avoid radar detection, to attack the target in a long dive which would ordinarily present the missile at a small angle of inclination with respect to a horizontal line passing through the burst point. This is normally the worst condition of approach from the standpoint of obtaining the optimum lethal effect at the ground target area because the velocity at this angle tends to slew the fragment pattern in the forward direction and thus may miss important parts of the target.

Accordingly, another object of the invention is to provide a warhead in which the aforesaid slewing effect caused by the low angle of approach can be counteracted in large measure by a redistribution of the exploding fragments to give a rearward component to the effect of the velocity. This particular object is obtained in brief by providing a warhead in which the fragmented surface does not take on the shape ofa cylinder which is conventional, but instead it is flattened along the lower portion as itextends toward the rear and this fragmented portion is curved upwardly at the rear so as to approach the longitudinal axis of the missile. This configuration provides a surface oriented in such manner that the fragments will take a rearward oblique direction as they are driven toward the ground. The fragment pattern would therefore show a greater concentration of hits by the fragments at the rear of the lethal area which would offset the effect of forward velocity.

It has been noted that at a given burst point, particularly when warheads of cylindrical configuration are employed, a considerable part of the total available fragments escape upwardly because they are driven from the top portion of the missile in a radial direction. These fragments are lost as far as lethal effect is concerned. The upper casing portion therefore need not be fragmentized nor, indeed, be present except to maintain symmetry and aerodynamic advantage of the missile as a whole.

Accordingly, another object of the invention is to provide an air-to-ground missile having a warhead of such construction that the fragmented portion of the casing can be used to produce the optimum lethal effect at ground level. This object is obtained, in brief, by giving to the warhead a construction which is devoid of an upper exploding portion, the entire charge of explosive being carried in the lower casing portion which may be fragmented into a number of layers. Thus, the fragmentary area which would normally extend all around a cylindrical warhead is now confined to only the lower case portion, and the latter would carry additional fragmented areas'which could be used to better advantage than if the latter had covered the upper part of the warhead. v

The invention will be better understood when reference is made to the following description and the accompanying drawings in which:

FIG. 1 represents a diagram drawn to a threedirectional coordinate system as employed in the other figures in accordance with orthographic convention;

FIG. 2 is a chart of a one-quarter (quadrant) of a cal- I culated pattern for the average relative fragment densifeet and in which the missile has no velocity;

FIG. 4 depicts a chart showing the effect in the pat tern obtained when themissile referred to in FIG. 3 is exploded at 25 feet and given a velocity of 3,000 feet per second; I

FIG. 5 represents a plan view of the improved warhead;

FIG. 6 is a sectional view taken along line 66 in I FIG. 5;

FIGS. 6A, 6B, 6C, 6D and 6E represent cross sections taken along the lines .A-A, BB, C-C, D--D and EE, respectively, in FIG. 6;

FIG. 7 illustrates the improvement in the fragment pattern at ground level in using the improved warhead;

FIG. 8 shows the general location of the improved warhead in a typical air-to-surface missile; and

FIG. 9 represents a cross section, somewhat enlarged, taken at the line 9-9 in FIG. 8.

The problem with which the invention is concerned, i.e., the procurement-of a warhead which would be most effective against a target when the missile has considerable approach velocity and a low delivery angle, necessarily involves actions which take place simultaneously in the vertical plane, also in a horizontal plane, and usually in two directions. It is, therefore, convenient to present these actions or movements by means of an orthographic diagram. In FIG. 1 the Y axis has been chosen as the earth trace of the missile path with the X axis as the ground lateral. The (PM) missile path is assumed to be in the Y-Z plane. The height of burst is represented by H and an arbitrary range position by S. The position of the target on the ground is denoted by O. The flight of the aircraft is assumed to be along the Y axis and the missile is delivered toward the burst point B after being released by the aircraft, at an angle measured from the Z or vertical axis. FIG. 2 shows a quadrantal chart indicating equal distances from the burst point B ofa typical but unimproved warhead of a density in terms of fragments per square inch normal to a fragment ray. The

densities

165, 26, etc., have been calculated on a comparative basis, assuming a condition in which the warhead was detonated statically on the ground at the point B and the angle 6 was assumed to be 30. The pattern was extended to lOO feet, an arbitrary selection for illustration only, in which the average in the 90 to 100 foot zone is 0.67. The density figures given on the chart are merely approximations to show in general, the manner in which the lethal effect falls off rapidly away from the burst point if this pattern were projected vertically on to the ground. This decay effect is present in greater or less degree depending upon the lethal pattern, which, in turn, is controlled by the height H of burst, also by the missile velocity at the burst point, in addition to the fragment velocities as these leave this point, as well as the angle of delivery.

FIG. 3 illustrates a low angle (actually horizontal) burst at low (zero) missile velocity with a 24 foot height of burst. The zones, or areas 1 to 10, in this and the remaining figures illustrate zones of fragment density as per the invention shown in FIG. 2, i.e., l 165 fragments/sq. inch, 2 26 fragments, etc. The longitudinal coverage on the earth trace of the flight path of over 13 feet is obtained and a resulting increase in the lethal area to 6,200 square feet. This was, in effect, obtained by the redistribution of fragments near the aim point. The maximum fragment intensity on the ground has been moved from the excessively heavy zone 1 (distribution of 165 per square inch in FIG. 2) to the zone 3 intensity of 9 per square inch. However, further examination of this figure shows in the Y-Z plane that a considerable part of the fragments are wasted on account of being dispersed into the atmosphere as indicated by the diagram to the left of the burst point B. In fact, if the top half of the warhead were cut off and thrown away, the lower half of the warhead would be just as effective as a missile in which the fragments extended both over the top and the bottom portions. If the air burst shown in FIG. 3 were taken and velocity added (3,000 feet per second missile, 5,000 feet per second fragment), the pattern shown in FIG. 4 would be obtained. It will be noted that the pattern of FIG. 3 is practically duplicated except that FIG. 4 shows a forward slewing of the ground level pattern, i.c., along the Y lateral from the point B because of the missile velocity. The lethal area is approximately 6,200 square feet. The maximum fragment intensity has again decreased from the heavy zone 1 distribution (which theoretically has taken place in the air between the burst point and the target 0) to the zone 3 intensity of9 per square inch at ground level. However, it will be further noted, and this is in contrast to the pattern of FIG. 3, that the pattern of FIG. 4 has been slewed forward of the burst point B and away from the center of the target 0. This is the direct result of the relatively high velocity of the missile (3,000 ft. per second) and also the fact that the missile was delivered at the low angle of 15 (9 with respect to the level of the ground. Even though the area of fragment dispersion is considerable, (6,200 square ft.) actually the kill" effect would be relatively small since most of the lethal area would occur at a distance away from the target.

In order to bring the fragment dispersion area closer to the target, thereby reducing the forward slewing effect, under conditions of high angle 0 or low angle of inclination, I add a rearward velocity component to the majority of the fragments. In addition, the number of fragments per square inch of the lower surface of the warhead is increased, particularly at the rear, in order to render the lethal area more concentrated on or near the target. This increase in the number of fragments is produced, without increasing the weight of the missile by rearranging the fragments which would normally be available at the top of the warhead and positioning them in the lower portion of the member in addition to removing the explosive material normally contained in the upper portion of the warhead to the lower portion. Consequently, the devastating power would be concentrated in the lower half of the warhead and this would serve to widen and intensify the fragment pattern in the direction of missile delivery. In order further to reduce the forward slewing effect, and in accordance with another aspect of my invention, I flatten the shape of the lower surface of the warhead, giving it a pseudo-eh liptical shape rather than the usual circular configuration. The degree of flatness becomes greater as the rear of the warhead is approached which causes the rear portion to curve upwardly toward the horizontal axis of the missile. Since the fragments during the explosion tend to be driven out normal from their starting surface, an intensified spray of fragments would be exploded to the rear of the warhead and as the missile follows the Y axis to reach the burst point, a considerably greater concentration of fragments would appear in the ground pattern which contains the target 0.

One physical shape that the improved warhead may take is shown in FIGS. 5 and 6. Reference character 1 shows the explosive material, such as Trinitrotoluene (TNT), contained within a thick shell 2 of several layers of metal which have been fragmentized in the usual manner. The shell, as shown in cross section in FIG. 6A, takes on a semicircular shape at the right or forward end, and then is slightly flattened as at 68, passing through partial elliptical shapes of varying depth, i.e., degrees of flatness, indicated in FIGS. 6C and 6D, and ending with a shallow portion (FIG. 6E). A thin metal plate 3 may optionally be secured in any suitable manner to the top of the warhead at a position as would correspond to the horizontal axis of the missile. It will be noted that the rate of change of shallowness ofthe elliptical body, i.e., the degree of flatness increases more rapidly from a position at about half the length of the warhead, (approximately at the section line C-C in FIG. 6A) to the left-hand or rear of the member. An imaginary tangential line 4 indicates the average slope of the surface and will show that there is a definite inclination which would cause the fragments to explode in a direction normal to this sloping surface. This rearward movement would offset, at least in some degree, the effect of a considerable missile velocity and a low delivery angle at the burst point. Moreover, in

view of the fact that the under side of the warhead carries one or more additional layers of fragments which would correspond to the layer or layers normally provided over the top of the warhead, the lethal area at ground level would not only be of greater width along the Y axis but would also provide a greater intensity of fragments at and about the target 0.

FIG. 7 shows a typical lethal pattern at ground level and as calculated from a burst of the improved warhead at a height (H) of 50 feet, missile velocity (Vm) of 3,000 feet per second, and a delivery angle of 75, i.e., 15 with respect to the horizontal axis. The lethal area would be about 15,800 square feet which would greatly exceed the area (6,200 square feet) obtained in FIG. 4 in which the conditions of operation are identical with those in FIG. 7 except that the burst occurred at the lower height of 25 feet. It will be noted that there is no fragment pattern extending to the left of the burst point B which is also different from that shown in FIG. 4 because there is little or no dispersion of the fragments upwardly from the burst point. A further study of FIG. 7 will show that the lethal area, as a whole, draws much closer to the target 0 than in FIG. 4, due both to its increased size and also its position with respect to the axes X, Y, which pass through the target. Furthermore, the longitudinal dimension of the fragment pattern along the Y axis has been increased from 13 feet (FIG. 4) to 48 feet (FIG. 7) and is virtually centered under the burst point. In addition, the forward slewing of the pattern caused by the missile velocity has been modified until it is no longer objectionable.

Both the initiator 5 and the booster 6 for exploding the charge 1 are preferably positioned at the forward end of the warhead, as indicated in FIG. 6'. Since there is a deflection of the fragment pattern in the direction of detonation, this procedure tends to increase the density near the target to assist in offsetting the effect of missile velocity.

The improved warhead is usually placed in the midsection of a missile typically illustrated in FIG. 8. The forward or cone end 7 of the missile may carry the usual sensors or other control devices. The usual stabilizing fins for guiding purposes are indicated at 8. The tail or rear end 9 of the missile is usually provided with an impulse motor (not shown) which operates on the well-known jet principle. Additional stabilizing and antiroll surfaces 10 including a rudder may also be provided at the tail end.

The intermediate section, generally indicated at 11 (FIG. 8), comprises a top half casing 12 of smooth, thin metal and a bottom half which consists of the improved warhead. The thin, semicylindrical casing 12 is desirable for aerodynamic reasons, also to strengthen the missile in the longitudinal direction. The fragmented case 2 preferably is made up of several layers of metal, with partially cut-through grooves indicated by the short radial lines in FIG. 9 to permit multitudinous fractures when the explosive material I is set off by the booster 6 (FIG. 6). The explosive material I, to which is added the amount normally contained in the upper portion of the casing, takes the shape of an annular ring of varying length except for the extreme rear portion. The material extends to about midway of the height of the casing as a whole, as seen in FIG. 9, the upper surface of which carries the plate 3. The empty space, in-

dicated at 13 directly above the plate, can be used if desired to contain any additional control accessories (not shown).

It has been pointed out that notwithstanding the greater thickness of explosive material and also of the increased fragmentization of the lower case portion, the missile containing the improved warhead is no heavier than the conventional form. The same quantity of explosive material and fragmentized metal is employed except that in accordance with my invention all of these elements are constrained to the lower half of the casing. The latter is given an explosive orientation as will offset the forward slewing effect due to missile speed and the low angle of delivery.

While a certain specific embodiment has been described, it is obvious that numerous changes may be made without departing from the general principle and scope of the invention.

1 claim:

1. A missile which, when in stabilized flight, is constituted of upper and lower longitudinal casing portions; a warhead contained solely in the lower casing portion and forming part of said lower casing portion, the upper longitudinal portion of the missile being constituted of a semicircular casing in cross section of smooth metal, said warhead having a casing constituted of at least one layer of fragmentized metal, said casing having a curved configuration in section, and an explosive material contained within the casing and coinciding in shape therewith.

2. A cylindrical missile according to claim 1 and in which a metal plate extends along the length of the warhead portion and is positioned between the upper and lower longitudinal portions of the missile, said explosive material being confined to a position below said plate, the space above said plate and within the missile being empty of explosive material.

3. A cylindrical missile according to claim 1 and in which the fragmentized lower casing of the warhead has a general semicircular configuration in cross section at its forward end and the configuration becomes progressively flattened to a general elliptical shape in cross section as the rear end of the warhead is approached, said explosive material conforming to the shape of the warhead casing.

4. A cylindrical missile according to claim 3, in which the degree of flattening of the lower casing portion of the warhead becomes greater at the rear end to provide a configuration which slopes upwardly toward the upper longitudinal portion of the missile which would serve to disperse the fragments at the moment of explosion in an angular direction rearwardly of the warhead.

5. A warhead for a missile which comprises a fragmentized hollow casing of a general rectangular shape in plan, and having a periphery generally of a semicircle in cross section at one end and passing continuously through pseudo-elliptical sections toward the other end, said sections being of a progressively decreasing depth so as to present a flattened exterior at said other end and a layer of explosive material of uniform thickness within said casing and conforming to the interior shape thereof.

6. A warhead for a missile in accordance with claim 5 and in which a booster and a fuze are positioned at the end of the warhead having the semicircular cross section.