Frangible kinetic energy projectile for air defense

A Kinetic Energy penetrator round is shown effective in neutralizing incoming air borne threat munitions such as rockets, artillery, or mortars for instance, without posing a threat in urban environments to harm bystanders on the ground. There are also no hazards or expense with this round of cleaning up unexploded ordnance, which might have occurred with other types of rounds due to unreliability of self destruct mechanisms. Shown herein is a kinetic energy penetrator for air defense that merely self destructs beyond its operational range into fragments that are not lethal to personnel on ground; no pyrotechnic or energetic materials means are used to activate this self destruct process. A full bore projectile structure is shown that is composed of plural axi-symmetric circular disks stacked on each other and tied by a shape memory metal wire of Nitinol. While operational as a joined group, the disks are a formidable round to kill an incoming air target. After the self destruct phase however, each disk is separated from adjacent disks on either side by a spring mechanism that enables separation after the process is initiated in flight when the Nitinol wire deforms due to heating from air drag. Each disk then proceeds alone with low enough terminal kinetic energy on the ground to be less than lethal.

BACKGROUND AND BRIEF SUMMARY OF INVENTION

Kinetic Energy penetrators are very effective in neutralizing incoming air borne threat munitions such as rockets, artillery or mortars, for instance. These penetrators are typically monolithic cylindrical objects that are made from high density materials, to enhance their ability to penetrate and defeat the threat and are spin stabilized in their flight to their target. However, the high kinetic energy and ballistic mass of these penetrators poses a problem in urban environments, because they still possess enough energy to kill bystanders and friendly troops when they return to the ground. This problem restricts the use of an otherwise effective air defense munitions. Other solutions to this problem are self destructing high explosive munitions, which after a preset time in flight detonate, after it has passed its effective operational range. The problem with this class of projectiles is that of dealing with the hazards of cleaning up unexploded ordnance, which occur due to unreliability of the self destruct mechanism. Shown herein is a kinetic energy penetrator for air defense, that self destructs beyond its operational range into fragments that are not lethal to personnel on ground. The penetrator does not use pyrotechnic or energetic materials means to activate the self destruct process. The proposed solutions are mechanisms that still allow the use of dense materials, but effectively reduce collateral damage by fragmenting the penetrator without the use of pyrotechnic means. A full bore projectile structure is shown that is composed of a plurality of axi-symmetric disks stacked on each other. Preferred embodiments include a circular disk with a hole in the center, such that a stack of such disks creates a channel through the axis of the projectile, thus the penetrator structure would be composed of a coaxial stack of axi-symmetric disks. Each disk is sized so that its individual ballistic coefficient ensures that aerodynamic drag (compared hypothetically to the drag if it were the shape of a rod or needle rather than circular) is sufficient to reduce terminal energy to below levels established for lethal injury to ground personnel which is considered to be approximately 75 Joules on impact. Another embodiment utilizes disks which although are not all alike are sized according to ballistic need for improved flight characteristics on a case by case basis. Each disk also retains its stability in flight from the spin imparted to its parent projectile. This ensures that a maximum frontal area of the disk is presented to the air stream for the remainder of the flight, ensuring maximum drag and therefore minimal terminal energy. Each disk is separated from succeeding disks on each side by a spring mechanism that enables separation after the separation process is initiated in flight. This is true even if no airborne target is hit by the round. However, if a target is engaged by this round, the respective disks will also separate because the round is almost certain to break apart on impact. Once on the ground, disks pose no explosive ordnance problems. Also, the fact that no pyrotechnic materials are used will reduce logistical burden and therefore also reduce lifecycle costs.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide a formidable kinetic energy air defense round which at the same time will not be a significant risk to innocent ground targets, and;

It is a further object of the present invention to provide a kinetic energy penetrator for air defense that self destructs beyond its operational range into fragments that are not lethal to personnel on ground, and;

It is a still further object of the present invention to provide a kinetic energy penetrator for air defense that does not use pyrotechnic or energetic materials means to activate any self destruct process, and;

It is yet another object of the present invention to provide a kinetic energy penetrator for air defense that does not result in any explosive ordnance cleanup operations following extensive use of this air defense.

These and other objects, features and advantages of the invention will become more apparent in view of the within detailed descriptions of the invention and in light of the following drawings. It should be understood that the sizes and shapes of the different components in the figures may not be in exact proportion and are shown here for visual clarity and for purpose of explanation.

DETAILED DESCRIPTION

FIG. 1shows a partial exploded view of a frangible kinetic energy air defense round according to the invention. The round includes a number of “n” separate disks110, which are mounted between a base (also called end cap)103, and a nose disk121(which could have a disk110substituted therefore if easier for manufacture purposes). In practice, the nose disk121will lead the round during flight. It will be appreciated that the total weight of the assembled round is actually distributed between the disks110, the base103and the nose disk121. The weight of this round fully assembled may be considerable so that when fired it can be formidable to destroy a flying target, yet the individual disks110or base103, or nose disk121will do far less harm hitting an unintended target on the ground than would the weight of the entire round, if the intended flying target were missed for instance. Although two disks110are shown inFIG. 1, this quantity could in theory be changed to a larger or smaller number as may be desired. On the nose side of base103, and on the nose side of each disk110, four equidistantly placed springs115are included, which springs fit respectively into four recessed holes118that are on the base side of each adjacent disk110and also on the base side of nose disk121. The depth of the recessed holes is shallow enough so that all springs115are normally in a compressed state when the round is assembled, as shown by the cross sectional view of a fully assembled round (FIG. 2). The nose side of each disk110and also the nose side of base103, also contain four protruding, equidistant, rectangular cross section, robust tabs109which are sized to fit into the four slots112found on the base side of each adjacent disk110and also on the base side of nose disk121. These interlocking male and female features on opposing sides of the disks serve as shear surfaces to provide adequate torque transfer between the base103and its adjacent disk and also thereafter between all adjacent disks, and therefore between the whole stack of disks, and the nose disk121, during spin up in the rifling of a launching weapon. As illustrated in the cross sectional viewFIG. 3, cup shaped base103of the projectile is also axisymmetric, with a mass302that matches that of each single disk110, for reasons of providing aerodynamic stability of the assembled round. Similarly, nose disk121is also designed to include a mass202that is comparable to that of each single disk110, also for reasons of providing aerodynamic stability of the assembled round. As shown byFIG. 2, there is a central open passageway208beginning at the nose side of end cap305of base103that passes all the way through the round to the nose side of nose disk121. The passage takes the form of (hidden lines) recessed cylindrical passage105in base103, as well as round passageways120(not fully shown in all the Figures) through each disk110, preferably of equal diameter to105and to each other disk110, and also through the nose disk121. As illustrated byFIG. 2, wire means206are positioned through passageway208, so that they are attached at209in base103such as by welding or by other means. The wire means are bent over at the nose side of nose disk121so as to hold the round together. The assembled round shown inFIG. 2may be used as shown or may be further enclosed in an ammunition body with a nose cone for protection or convenience, if desired, but the nose cone must still be able to transfer heat to the wire means and also be easily frangible along with the body. Although two wires are shown here by illustration, in practice this quantity could be increased as deemed necessary to properly hold the round together. As further may be seen inFIG. 2, round200is assembled in a normally compressed state; all disks are placed in position with all springs compressed, and then the end of wire means206are bent over (or tied, braid in some adequate manner), so as to hold the round together at nose disk121. There are slip band obturator means106on base103, so that upon firing through a rifled barrel, the assembled round will spin, which aids in flight stability. The wires are made of a shape memory alloy material (SMA) such as Nickel Titanium (NiTi=Nitinol), CuSn, InTi, TiNi, MnCu, CuZnAl, or for instance, gold cadmium alloys. Although the wires may be as shown when the round200is assembled, more or less at room temperature, however in flight by reason of air resistance these wires will become heated, soften, and change their shape. Effectively then, the wires will no longer hold in place, or hold the round together when sufficiently heated, and this will allow nose disk121and the disks110to separate off the wires, further aided by the compressed springs pushing apart all the disks and also the nose disk. It can be appreciated that various variations to wire means206geometry and the specific wire material's mechanical response to heating can be used to time the event when the projectile will begin disintegration in flight, and therefore to design for the effective range of the projectile.