WO2009029299A1

WO2009029299A1 - Extended range non-lethal projectile

Info

Publication number: WO2009029299A1
Application number: PCT/US2008/062177
Authority: WO
Inventors: Danen M. Lynn; John A. Kapeles; John A. Hultman
Original assignee: Defense Technology Corporation Of America
Priority date: 2007-08-30
Filing date: 2008-05-01
Publication date: 2009-03-05

Abstract

A non-lethal projectile having a generally hollow projectile body and a driving band for engaging barrel rifling positioned on the projectile body and a nose section attached to the projectile body. The projectile body includes a hardened driving band, a thickened projectile body side wall or longitudinal ribs positioned on an internal surface of the longitudinal body to minimize the deflection of the driving band with respect to barrel rifling lands.

Description

EXTENDED RANGE NON-LETHAL PROJECTILE

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to the field of non-lethal munitions utilized by law enforcement and military forces, and the need to extend the effective range of these munitions. Longer range non-lethal engagements are desired to provide additional stand off distance between military forces and suspected combatants, and to allow greater time to determine the intent of the combatant so that a response can be made using an appropriate level of force. In modern engagements, it is often difficult to initially distinguish combatants from non-combatants, and this situation can result in a response using a high level of force in order to protect personnel and assets. Longer range non-lethal weapons provide a means to determine the intent of a potential combatant and allow sufficient time and distance to deter or control the threat without resorting to lethal force. [0002] Non-lethal projectiles typically have low mass and are fired at low velocity to control the kinetic energy delivered to the target. Most non-lethal projectile bodies are made from a plastic or molded polymer material to keep the overall density, weight, and hardness down for optimal non-lethal characteristics, and non-lethal projectile noses are typically made of a foamed polymer or other compliant material. The use of metal is avoided as a structural material for the projectile, only being used in some cases as ballast to adjust the projectile mass properties. The low-mass non-lethal projectiles can be accelerated very quickly with relatively small propelling charges, and tend to experience significant deceleration from opposing aerodynamic forces during flight.

[0003] Non-lethal impact munitions which impart kinetic energy through blunt trauma to redirect, control, or incapacitate aggressive human targets, depend on accurate shot placement to achieve the desired outcome while minimizing the risk of serious injury. As a result, the most accurate non-lethal impact munitions are based on a spin-stabilized design, where the non-lethal projectile incorporates a driving band that engages the rifling grooves in the launcher barrel to impart spin to the projectile. Typical ranges for spin-stabilized non-lethal projectiles are 10 to 50 meters, with reasonable accuracy and only modest trajectory drop. [0004] Spin stabilized projectile designs have attempted to maximize the gyroscopic stability by controlling the aerodynamic and mass properties while maintaining a reasonable surface area of impact for optimal non-lethal characteristics. The gyroscopic stability is maximized when the majority of the mass of the projectile is concentrated at a fixed distance from the axis of rotation, such as in the case of a hollow cup spinning about its longitudinal axis. This type of projectile design incorporates a hollow projectile with a forward face, bore riding sidewalls extending rearward from the forward face, and is open at the rear. The hollow projectile design achieves the goal of concentrating the mass of the projectile at a distance from the axis of rotation, and produces an extremely stable projectile in flight when coupled with a low-density non-lethal projectile nose.

[0005] In addition to maximizing the gyroscopic stability, it is desirable to control the mass properties of the projectile to place the center of gravity at the location of the projectile driving band. Placement of the center of gravity at the bore-riding surface of the projectile allows for more stability as the projectile engages the barrel rifling and travels down the barrel.

[0006] The hollow, spin-stabilized projectile of previous designs has a major problem: concentration of the mass at a distance from the axis of rotation for optimal stability produces thinner sidewalls at the location of the driving band, which can be made to deflect when the projectile engages the barrel rifling during firing. During the rapid initial projectile acceleration and engagement, sufficient deflection of the sidewall can occur so that the projectile driving band is prevented from fully engaging the rifling and is driven forward along the barrel without turning with the rifling grooves. This causes the plastic driving band to slip along the rifling lands, shearing off the plastic material along the edges of the lands and leaving this debris in the barrel. This slippage in the barrel rifling results in incomplete spin up, and in extreme cases, no spin up of the projectile prior to leaving the barrel. For the case of no spin, the projectile is unstable and begins to tumble soon after leaving the barrel. For incomplete spin up, the projectile has stability for a short distance until normal deceleration causes the spin rate to decrease to the point of instability. In both cases, the instability results in erratic flight and complete loss of accuracy. A secondary consequence of the slippage in the barrel is the plastic shavings that are stripped off the driving band and left to accumulate around the rifling lands in the barrel. Build up of this material on either side of the lands can form a "ramp" that effectively decreases the engagement height of the lands and promotes further slippage of the projectile in the barrel.

[0007] The muzzle velocity requirements of short and medium range non-lethal munitions do not typically result in slippage of the projectile in the barrel rifling due to the initial acceleration. As the projectile is propelled along the barrel, only minor deflection and slippage in the rifling lands occurs, and the projectile is ultimately spun up before exiting the barrel.

[0008] In order to extend the range of non-lethal munitions, the velocity must be increased significantly to control the trajectory drop over the longer ranges. This requires greater propelling force and pressure, and results in the low-mass projectile experiencing greater initial acceleration as it engages the barrel rifling. As the plastic side walls of the projectile deflect, this higher acceleration can increase the tendency for the driving band on the projectile to slip relative to the metal rifling lands in the barrel rather than engaging and causing the projectile to spin. As the projectile is pushed with greater force down the barrel, little or no spin up is accomplished, resulting in unstable flight once the projectile leaves the barrel.

[0009] There are several approaches that can be used to address the issue of projectile slippage in the rifling lands at higher velocity and the resulting projectile instability. These can include minimizing the deflection of the driving band, and hardening the material of the driving band to make it less likely to shear when engaging the barrel rifling. For many projectile designs (lethal as well as non- lethal), the deflection of the driving band is addressed by incorporating some supportive structure under the driving band. For example, some projectile designs do not incorporate a hollow cavity in the projectile, instead utilizing a solid mass to form the projectile body. These types of designs minimize or eliminate the deflection of the driving band when forced into the rifling lands, but at the same time can decrease the gyroscopic stability of the projectile.

[0010] hi addition, many of these designs place the projectile driving band well behind the projectile center of gravity, resulting in increased contact of the nose of the projectile with the barrel sidewall as the projectile travels down the barrel. The increased contact with the barrel sidewall interferes with the complete spin up of the projectile, which can affect the stability of the projectile after it leaves the barrel. This phenomenon can be particularly detrimental for the case of non- lethal projectiles, which often incorporate compliant or frangible nose materials that can deform or be damaged through contact with the barrel rifling. For the case of a non-lethal projectile that incorporates a frangible nose, the increased contact can damage the projectile nose, resulting in leakage of contents contained within the nose. Typical fill materials for non-lethal projectiles can include chemical irritants or marking compounds, and leakage of these materials from the projectile nose in the barrel or as the projectile leaves the barrel can compromise the effective deployment of the munitions. In addition, leakage of the projectile fill materials during flight will destabilize the projectile and degrade the accuracy.

[0011] Practical considerations often determine the location of the projectile driving band. For example, in the case of a 40MM non-lethal munition, both the overall shell height and the distance from the bottom of the shell to the driving band must be limited so that the driving band does not engage the barrel rifling when the munition is inserted in the barrel.

For this reason, the driving band on 40MM projectiles rests just above and in contact with the shell casing when the projectile is inserted in the shell. The hollow non- lethal projectile complies with this constraint by locating the projectile driving band at the rear of the projectile behind the center of gravity, with the hollow projectile body extending forward from the driving band. The resulting projectile has high gyroscopic stability, but experiences significant deflection of the driving band and projectile instability as the projectile travels down the barrel. [0012] Another potential solution to address slippage in the rifling lands is to make the projectile and driving band out of a harder material that will not shear as easily when forced into the rifling lands. Many spin stabilized projectile bodies and driving bands are made out of a metal such as aluminum, which produces repeatable engagement in the rifling lands without slipping, even at high velocities. However, there are drawbacks to using aluminum as the projectile body material for a non-lethal projectile. First, aluminum is significantly denser than the plastic materials typically used for the non-lethal projectile body, increasing the weight of the projectile, as well as the delivered kinetic energy to the target. Lower velocities must be used to control the delivered energy, which can adversely affect the flight trajectory, especially for a longer range munition. Second, the harder aluminum can cause more damage to the body upon impact than plastic, resulting in greater risk of injury. [0013] The optimal extended range non-lethal projectile design should incorporate a generally hollow body to concentrate the mass of the projectile at a fixed distance from the axis of rotation, while minimizing the deflection of the driving band when forced into the rifling lands, and the tendency of the projectile material to shear and cause slippage in the barrel rifling. In addition, the projectile driving band should be placed near the projectile center of gravity, to minimize instability as the projectile travels along the bore and to avoid possible damage to the projectile nose. [0014] Current short or medium range non-lethal projectile designs can function with some deflection of the driving band due to the lower initial acceleration and muzzle velocity, while others incorporate structure in place of the hollow portion in the projectile body, sacrificing some degree of gyroscopic stability. Similarly, the shorter range projectile designs are more tolerant of projectile instability as the projectile travels down the barrel, because the lower acceleration and muzzle velocities decrease the potential for projectile nose damage by contact with the barrel rifling.

[0015] Longer range non-lethal projectile designs must maximize the gyroscopic stability to achieve optimum aim point accuracy, and higher initial projectile acceleration and velocity is required to produce acceptable flight trajectories. The projectile center of gravity must be located near the projectile bore riding surface to minimize interference with the spin-up of the projectile, as well as the potential for damage to the projectile nose. The projectile weight and hardness must be controlled, so that the non-lethal impact characteristics are maintained. The need exists for a non-lethal projectile design that is light weight, can be fired at higher velocities for longer range applications without experiencing slippage or instability in the barrel rifling, and has optimum gyroscopic stability for high accuracy.

SUMMARY OF THE INVENTION

[0016] The present invention is directed to the design of a non-lethal projectile suitable for extended range applications, that includes a generally hollow projectile body with a driving band for engaging barrel rifling; a projectile nose made out of either a compliant or frangible material; and a propulsion system capable of propelling the projectile to engage the barrel rifling and impart spin to the projectile. The projectile body design incorporates features that minimize the deflection of the driving band when forced into the barrel rifling lands, and decreases the tendency for the projectile to slip in the lands. The projectile design places the driving band near the location of the projectile center of gravity to minimize the potential for instability as the projectile travels down the barrel, and potential damage to the projectile nose. The projectile is designed so that the generally hollow projectile body can be inserted into the propulsion shell base, so that the distance from the bottom of the shell to the driving band can be controlled while maintaining optimal gyroscopic stability. In projectile designs where the driving band is not located at the center of gravity, several features can be incorporated into the projectile design to minimize deflection of the driving band. These include a specific increase in the thickness of the wall extending from the forward face of the projectile body to the rear of the projectile, longitudinal structural members that are molded or placed along the interior surface of the hollow projectile to increase the stiffness of the projectile wall, or incorporation of a harder material for the driving band which decreases the tendency for the driving band material to shear when forced at higher velocity into the barrel rifling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a cross-sectional view of a non-lethal extended range projectile of the present invention optimizing the center of gravity location and gyroscopic stability incorporating a compliant nose section;

[0018] FIG. 2 is a cross-sectional view of an alternative embodiment non-lethal extended range projectile of FIG. 1 incorporating a frangible nose carrying a payload;

[0019] FIG. 3 is a side view of the non-lethal extended range projectile of FIG. 1 inserted into a propulsion shell base;

[0020] FIG. 4 is a second alternative embodiment non-lethal extended range projectile having an increased side wall thickness and a compliant nose section; [0021] FIG. 5 is an end perspective view of a third alternative embodiment non-lethal extended range projectile incorporating a longitudinal side wall ribs for increased stiffness; and

[0022] FIG. 6 is a fourth alternative embodiment non-lethal projectile incorporating an integral driving band of a different material than the projectile body. DETAILED DESCRIPTION OF THE INVENTION

[0023] As shown in Figs. 1-6, the non- lethal munition 10 of the present invention can be divided into three main components: the projectile body 12, the projectile nose 14, and the propulsion system 16. These are described below. [0024] The projectile body 12 incorporates a forward face 18 with side walls 20, 22 extending to the rear 24 of the projectile, and a driving band 26 positioned around the external surface 28 of the side walls 20, 22. The forward face 18 may or may not incorporate a recess 30 to locate the projectile nose 14 for assembly. The rear of the projectile is open, and a generally hollow cavity 32 is formed by the rear edge 34 of the forward face and the internal surface 36 of the side walls. The projectile body is typically made of a plastic, or a rigid molded polymer to provide strength without excessive weight. [0025] Figs. 1-3 of the invention illustrate the projectile driving band 26 at the approximate axial location of the forward face 18, so that the driving band is structurally supported by the forward face. In these embodiments, the projectile side walls extending to the rear of the projectile are intended to be inserted and contained within the propulsion shell base, allowing the distance from the bottom of the shell to the driving band to be controlled as shown in Fig. 3. This design allows placement of the driving band at the approximate location of the projectile center of gravity 38, while allowing for optimal gyroscopic stability due to the generally hollow projectile body. Small axial variations in the location of the center of gravity can occur due to variations in the projectile nose 14 as shown in Fig. 1 or payload material 40 as shown in Fig. 2, but this will not adversely affect the balance of the projectile significantly as long as the center of gravity is maintained approximately near the bore-riding surface 42 of the driving band. Analysis and testing of various projectile designs have shown that placement of the driving band edge 44 within approximately 0.1 calibers of the projectile center of gravity will result in a stable configuration while engaging the barrel rifling and traveling down the barrel.

[0026] The external diameter 46 of the projectile side walls 20, 22 is tapered toward the aft end 24 of the projectile to produce a "boat tail", which reduces the base drag of the projectile in flight. This configuration is shown in Figs. 1 and 2 for different non-lethal nose designs. Fig. 3 shows the projectile inserted into the propulsion shell base 48. The shell base 48 has an open end 50 to accept the projectile 10. The opposite end 52 includes a cavity 54 for placement of a propellant 56 and an initiating charge 58. The cavity 54 and open end 50 are separated by a bulk head 60 and vent hole 62. A rupture disk 64 may be positioned between the vent hole and the propellant. [0027] As shown in Fig. 4, another embodiment of the non-lethal munition 10 of the present invention minimizes the deflection of the driving band 26 by increasing the stiffness of the side walls 20, 22 extending to the rear 24 of the projectile from the forward face 18. This design maintains the ratio of the internal diameter of the hollow cavity 32 to the external diameter 66 of the driving band to be 0.8 or less. Experimental studies with different projectile body materials indicate that this ratio will provide the required stiffness to minimize deflection of the side wall and driving band, while allowing the projectile mass to be concentrated at a fixed distance from the axis of rotation 68 for optimal gyroscopic stability. This projectile design is better suited for medium range engagements using non- frangible projectile nose materials, because the center of gravity location is not optimal. [0028] One set of test data is shown below in Table I, where projectile bodies with two different side wall thicknesses were subjected to the same deflection, measuring the force required to produce the deflection. Table 1 shows the results of the tests. The deflection was set at 0.150" standard for each body, and the force was measured at that distance. An average of 1411 pounds of force was required to produce the deflection of the projectile body with thickened sidewalls (0.72 ratio of the internal diameter of the hollow cavity to the external diameter of the driving band), as opposed to an average of 858 pounds for the thinner-walled base (ratio of 0.81).

Table I: Deflection Test Data

[0029] The two projectile body designs tested above were also analyzed to verify that the gyroscopic stability had not been adversely affected by the increased sidewall thickness. Both designs have a gyroscopic stability of 2.03. One projectile design having a ratio of the internal diameter of the hollow cavity to the external diameter of the driving band of 0.72 is shown in Fig. 4.

[0030] Another embodiment of the non-lethal munition 10 of the present invention incorporates longitudinal ribs 70 on the internal surface of the generally hollow cavity 32 of the projectile as shown in Fig. 5, which can be formed in place during the molding of the projectile body, or bonded in place as a secondary operation after the projectile body is manufactured. The ribs 70 act to stiffen the projectile body side wall 20 and minimize deflection of the driving band 26, while having only a minor effect on the gyroscopic stability.

[0031] Still another embodiment non-lethal munition 10 of the present invention minimizes deflection of the driving band 26 by incorporating a separate driving band that is made of a harder material relative to the plastic or rigid polymer material of the projectile body 12. A metal, such as aluminum, is made into a ring with the dimensions of the driving band and co-molded with the plastic body or assembled after body manufacturing as a secondary operation, hi this projectile design, the hard material such as aluminum makes contact with the metal rifling lands in the barrel, while keeping the low weight and generally desirable non-lethal characteristics of the plastic projectile body. Fig. 6 illustrates one possible configuration of this embodiment where a thin aluminum driving band 26 is molded into a plastic projectile body 12, maintaining the external contour of the projectile side wall

20 and driving band dimensions, but providing increased structure and hardness to the driving band to minimize deflection and shear when engaging the lands of the barrel rifling. [0032] For long range non-lethal projectiles that must withstand extreme velocities, a driving band made of a plastic or polymer material may experience shear and slip in the barrel rifling, even if the deflection is minimized by structurally supporting the driving band. This issue can be addressed by incorporating the metal driving band described above as an integral part of the optimized projectile design of Fig. 1, to provide the most robust interface between the driving band and the barrel rifling. Because the higher density metal is used for the driving band, the optimized projectile center of gravity is not affected. [0033] These features have been described for the example of a 40MM non-lethal munition, but they could be applied to other calibers and training ammunition applications. The invention has been described with respect to specific embodiments thereof, but it is to be understood that changes and modifications can be made therein which are within the full intended spirit of the invention as hereinafter claimed.

Claims

WHAT IS CLAIMED IS:

1. A non- lethal projectile comprising: a projectile body having a forward face and a side wall extending rearward that forms a generally hollow cavity; a driving band positioned on an external surface of the side wall at approximately a location of the forward face, such that a projectile center of gravity falls within an axial dimension of the driving band, or at least one edge of the driving band is within 0.1 calibers of the projectile center of gravity; and a projectile nose made of a compliant or frangible material that is less dense than a material of the projectile body.

2. The projectile of claim 1, wherein the side wall is tapered rearwardly.

3. The projectile of claim 1 , wherein the projectile nose is a frangible projectile nose which contains a payload that includes one of an irritant, inflammatory chemical, or compound that marks a target in the visible, ultraviolet, or infrared spectrum.

4. The projectile of claim 1 further having means for stiffening the projectile side wall.

5. The projectile of claim 4 wherein the means for stiffening the projectile wall is the driving band being made of a harder or denser material than the material of the projectile body.

6. The projectile of claim 5 wherein the driving band is made of aluminum.

7. A non-lethal projectile comprising: a projectile body having a forward face and a side wall extending rearward that forms a generally hollow cavity; a driving band positioned on an external surface of the side wall; a projectile nose made of a compliant or frangible material that is less dense than a material of the projectile body; and a mechanical means for stiffening the side wall to minimize deflection of the side wall and driving band.

8. The projectile of claim 7, wherein the means for stiffening the side wall is a thickened side wall portion having a ratio of an internal diameter of the generally hollow cavity to an external diameter of the driving band of 0.8 or less.

9. The projectile of claim 7, wherein the means for stiffening the side wall are longitudinal ribs on an inside surface of the side wall.

10. The projectile of claim 7, wherein the means for stiffening the side wall is a driving band made of a harder or denser material relative to the projectile body.

11. The projectile of claim 7, wherein the projectile nose is a frangible projectile nose which contains a payload that includes one of an irritant, inflammatory chemical, or compound that marks a target in the visible, ultraviolet, or infrared spectrum.

12. A non-lethal munition comprising: a projectile body having a forward face and a side wall extending rearward that forms a generally hollow cavity; a driving band positioned on an external surface of the side wall at approximately a location of the forward face, such that a projectile center of gravity falls within a driving band axial dimension, or at least one edge of the driving band is within 0.1 calibers of the projectile center of gravity; a projectile nose made of a compliant or frangible material that is less dense than a material of the projectile body; and a propulsion system comprised of a cylindrical tube with an open end to accept the projectile body and an opposite end having a cavity for placement of a propellant and initiating charge, the cavity and open end separated by a bulk head and a vent hole.

13. The munition of claim 12, wherein the projectile nose is a frangible projectile nose which contains a payload that includes an irritant, inflammatory chemical, or a compound that marks a target in the visible, ultraviolet, or infrared spectrum.

14. The munition of claim 12, further having means for stiffening the projectile side wall.

15. The projectile of claim 14 wherein the means for stiffening the projectile wall is the driving band being made of a harder or denser material than the material of the projectile body.

16. The projectile of claim 15 wherein the driving band is made of aluminum.

17. A non-lethal munition comprising: a projectile body having a forward face and a side wall extending rearward that forms a generally hollow cavity; a driving band positioned on the external surface of the side wall; a projectile nose made of a compliant or frangible material that is less dense than a material of the projectile body; a means for stiffening the side wall to minimize deflection of the side wall and driving band; a propulsion system comprised of a cylindrical tube with an open end to accept the projectile body and an opposite end having a cavity for placement of a propellant and an initiating open end separated by a bulk head and a vent hole.

18. The munition of claim 17, wherein the means for stiffening the side wall is a thickened side wall portion having a ratio of an internal diameter of the generally hollow cavity to an external diameter of the driving band of 0.8 or less.

19. The munition of claim 17, wherein the means for stiffening the side wall are longitudinal ribs on an inside surface of the side wall.

20. The munition of claim 17, wherein the means for stiffening the side wall is a driving band made of a harder or denser material relative to the projectile body.