STEERABLE PROJECTILE

Abstract

There is provided a projectile, a system and a related method of operation of a projectile comprising: a front ogive section; an aft section; and a control module; wherein the front ogive section is rotatably connected to the aft section by a coupling device, the front ogive section further comprising an asymmetric surface such that the asymmetric surface exerts an imbalance upon the projectile, where in use, the angular rotation of the front ogive section can be selectively adjusted relative to the aft section by commands from the control module to the coupling device influencing a helical trajectory of the projectile in flight thereby causing a change in direction thereby steering the projectile towards a target.

Claims

1. A projectile comprising: an aft section; a front ogive section rotatably connected to the aft section by a coupling device, the front ogive section comprising an asymmetric surface such that the asymmetric surface exerts an imbalance upon the projectile; and a control module; wherein in use, an angular rotation of the front ogive section can be selectively adjusted relative to the aft section by commands from the control module to the coupling device, in a first arrangement, the coupling device is coupled, such that the front ogive section spins at a same angular rotation as the aft section, the projectile travelling in a first helical trajectory, in a second arrangement, the coupling device is decoupled, such that the front ogive section spins at a different angular rotation relative to the aft section, the projectile travelling in a second helical trajectory, said first helical trajectory comprises a smaller radius than the second helical trajectory, and selective activation between the first and second arrangements, causes a change in direction thereby steering the projectile towards a target.

2. The projectile according to claim 1, wherein the asymmetric surface is an aerodynamic lifting surface.

3. The projectile according to claim 2, wherein the aerodynamic lifting surface is a truncated ogive.

4. The projectile according to claim 1, wherein the projectile is capable of deforming to create the asymmetric surface after firing.

5. The projectile according to claim 1, comprising a retractable element to selectively create the asymmetric surface.

6. The projectile according to claim 1, wherein the coupling device is a passive coupling device.

7. The projectile according to claim 6, wherein the passive coupling device is a brake or clutch.

8. The projectile according to claim 1, wherein the projectile has an outer profile that is continuous.

9. The projectile according to claim 1, wherein the projectile is a spun projectile to be fired from a rifled barrel.

10. The projectile according to claim 1, wherein the projectile comprises a receiver for receiving guidance instructions.

11. The projectile according to claim 10, wherein the receiver is a beam rider receiver.

12. The projectile according to any claim 1, wherein the projectile comprises a transmitter to transmit the position of the projectile.

13. A system for controlling a projectile, the system comprising: the projectile according to claim 1, and; a targeting system, wherein the control module of the projectile receives guidance instructions from the targeting system thereby enabling the projectile to be steered to the target.

14. The system of claim 13, wherein the control module system is governed by the quasi-dynamic guidance law equation: $V_{VV}\left(d\right)=\left[\begin{array}{c}{V}_{Lim}\left(d\right)-\xi \\ V_k\\ 0\end{array}\right]\forall d\in \left\{\begin{array}{l}{d}_1\le d\\ d_2\le d<d_1\\ 0\le d<d_2\end{array}\right),$ wherein V.sub.PT(d) is a lateral speed at which the projectile closes the target, V.sub.lim(d) is a maximum lateral speed correction the projectile is capable of making at full, saturated actuator effort, ξ is a delay modification value, V.sub.k is a constant speed, d is a lateral distance to target, d.sub.1 is a distance to switch from V.sub.lim(d) - ξ to V.sub.k, d.sub.2 is a level of accuracy of the projectile.

15. A method of controlling the projectile of claim 1, the method comprising: firing the projectile from a barrel; determining a location of the target; calculating guidance commands to change the trajectory of the projectile to intercept the target; and causing said guidance commands to instruct the control module to steer the projectile to-a the target.

16. The method of claim 15, wherein causing said guidance commands to instruct the control module to steer the projectile to the target results in the control module causing the coupling device to selectively couple and decouple the front ogive section and the aft section based on the guidance commands.

17. The projectile according to claim 1, wherein the coupling device is an active coupling device.

18. The projectile according to claim 1, wherein in the second arrangement, the coupling device is decoupled, such that the front ogive section spins at a slower angular rotation relative to the aft section.

19. A projectile comprising: an aft section; a front ogive section rotatably connected to the aft section by a coupling device, the front ogive section comprising an asymmetric surface such that the asymmetric surface exerts an imbalance upon the projectile; and a control module configured to cause the coupling device to selectively couple and decouple the front ogive section and the aft section, based on commands from the control module to the coupling device, thereby steering the projectile towards a target; wherein in use, an angular rotation of the front ogive section can be selectively adjusted relative to the aft section by the commands from the control module to the coupling device, in a first arrangement, the coupling device is coupled, such that the front ogive section spins at a same angular rotation as the aft section, the projectile travelling in a first helical trajectory, and in a second arrangement, the coupling device is decoupled, such that the front ogive section spins at a different angular rotation relative to the aft section, the projectile travelling in a second helical trajectory.

20. The projectile according to claim 19, wherein the first helical trajectory comprises a smaller radius than the second helical trajectory.

Description

[0092] Several arrangements of the invention will now be described by way of example and with reference to the accompanying drawings of which;-

[0093] FIG. 1 shows a generic arrangement of the projectile.

[0094] FIG. 2 shows a force diagram of the projectile of FIG. 1.

[0095] FIGS. 3a & 3b show a helix trajectory plot of a rifled projectile.

[0096] FIG. 4 shows a system of a rifled projectile fired from an artillery gun.

[0097] FIG. 5 shows a system of a rifled projectile fired from a hand held weapon.

[0098] FIG. 6 shows a method of controlling a projectile.

[0099] Turning to FIG. 1, there is provide a projectile 100 comprising: a front ogive section 102, an aft section 104; and a control module 106; wherein the front ogive section 102 is rotatably connected to the aft section 104 by a coupling device 108, the front ogive section 102 further comprising an asymmetric surface 110, where in use, the angular rotation of the front ogive section 102 can be selectively adjusted relative to the aft section 104 by commands from a control module 106 to the coupling device 108, such that the asymmetric surface 110 exerts an imbalance upon the projectile to selectively alter the trajectory of said projectile, and thereby steer and course correct the projectile.

[0100] In the present arrangement, the projectile is a gun launched projectile, such as a medium calibre shell wherein the front ogive section 102 and aft section 104 are made from steel. For simplicity, features such as fuzes, driving bands, and other typical features are not shown.

[0101] In the present arrangement, the coupling device 108 is an active coupling device in the form of a servo motor. The servo motor allows both clockwise and anticlockwise rotation of the front ogive section 102 with respect to the aft section 104.

[0102] In the present arrangement, the projectile rotates about axis X.

[0103] In the present arrangement, the projectile comprises an electrical slip ring (not shown) between the front ogive section 102 and the aft section 104.

[0104] In the present arrangement, the asymmetric surface 110 is an aerodynamic lifting surface, specifically a truncated ogive. Said asymmetric surface extends α°, in this example 90°, around the plane face of the projectile as seen in Section A-A.

[0105] In the present arrangement, the projectile 100 comprises a continuous surface such that the outer profile of the projectile 100 is smooth blended surface absent from protruding fins or protruding control surfaces.

[0106] In the present arrangement, the projectile may comprise a receiver for receiving guidance instructions from an external targeting system in the form of an optical receiver 112. Said optical receiver 112 is in communication with the control module 106 and is a beam rider receiver such that the optical receiver senses the intensity of a guidance laser (not shown) wherein the control module 106 is configured to detect drift of the laser focus from the optical receiver 112 wherein the control module 106 issues commands to the coupling 108 in order to remain on the laser path.

[0107] Turning to FIG. 2, there is provided the projectile of FIG. 1 as a force diagram. The projectile 200 comprising both front ogive section 202 and aft section 204 travelling at velocity v. In this arrangement the projectile is fired from a rifled barrel, the aft section 204 and ogive 202 both rotate at the same clockwise angular rotation ω1 & ω2 respectively against oncoming airflow A. The oncoming airflow A is deflected by the asymmetric surface 210 to create a first imbalanced force vector F.sub.c on the projectile.

[0108] On command of the control module (not shown), the servo motor changes the rate of angular rotation of the ogive 202, to either a reduced clockwise ω2′ angular rotation rate or an anticlockwise ω3′ with respect to the aft section 204 which continues to rotate at angular speed ω1 thereby creating a second imbalanced force vector F.sub.c on the projectile, i.e. altering the angle of the force vector F.sub.c about the axis X.

[0109] Alternatively, the coupling device may be a passive coupling device in the form of a brake. The brake can be selectively braked and un-braked to uncouple the front ogive section from the aft section thus allowing the front ogive section to slow due to an aerodynamic roll damping moment.

[0110] Turning to FIGS. 3a & 3b, there is provided a projectile 300 as shown in FIG. 1, travelling in a helical path substantially along the axis x after firing from a rifled barrel.

[0111] In FIG. 3a, the front ogive section and aft section are in the coupled mode, i.e. both sections spin at the same angular rotation, the helix radius is r1 on the superimposed YZ plane.

[0112] In FIG. 3b, the front ogive section and aft section are in the decoupled mode, i.e. the front ogive section is spinning at a different angular rotation compared to the aft section, the helix radius is r2 on the superimposed YZ plane, wherein radius r2 is greater than radius r1. The control force from the aerodynamic surfaces on the ogive act in a tangential direction for longer, resulting in a larger radial acceleration. The projectile thus travels further radially before the control force rotates to oppose the motion. The result is that in the decoupled state, the trajectory forms a larger helix r2 diameterthan in the coupled mode r1. When the control module calculates that the projectile is on trajectory to hit the intended target, the front ogive section and aft section re-couple such that the front ogive section is restored to the spin rate of the faster spinning aft section thus returning to a helix radius r1 as shown in FIG. 3a.

[0113] Turning to FIG. 4, there is provided a system 400 for controlling a projectile, the system comprising a projectile 402 as shown in FIG. 1 fired from a rifled artillery gun 404 towards a target 406 along a nominal trajectory 408. After firing, the coupling device of projectile 402 is coupled such that the front section spins at the same angular rotation as the aft section, the projectile travelling in a first helical trajectory with radius r1. Later in flight, the projectile 402′ coupling device is decoupled, the front section spins at a different angular rotation relative to the aft section, the projectile travelling in a second helical trajectory with radius r2, wherein the first helical radius r1 is smaller than the second helical radius r2, thereby enabling the projectile 402 to be steered to the target 406.

[0114] In the present arrangement, there is provided an external targeting system in the form of a laser designator 410. Said laser designator is trained on the target 406 by beam 412. The laser designator in optical communication with the projectile 402 comprising an optical receiver on the projectile via optical signals 414.

[0115] Turning to FIG. 5, there is provided a system for controlling a projectile 500, the system comprising a projectile 502. In the present arrangement, said projectile 502 is a small arms calibre bullet fired from a rifle 504 towards a target 506 along a nominal trajectory 508. After firing, the coupling device of projectile 502 is coupled such that the front section spins at the same angular rotation as the aft section, the projectile travelling in a first helical trajectory with radius r1.

[0116] Later in flight, the projectile 502′ coupling device is decoupled, the front section spins at a different angular rotation relative to the aft section, the projectile travelling in a second helical trajectory with radius r2, wherein the first helical radius r1 is smaller than the second helical radius r2. The second helical radius corrects the projectile flightpath such that the projectile is on a trajectory which will hit the target 506 wherein the front ogive section couples with the aft section to travel in a third helical trajectory with radius r3, wherein the third helical radius is smaller than radius r2, thereby enabling the projectile 502 to be steered to the target 506. The projectile is further able to couple and decouple multiple times during flight to switch between larger and smaller helical trajectories in order to correct the trajectory to target 506.

[0117] In the present arrangement, there is provided an internal guidance system within the control module (not shown) of the projectile 502 in the form of an accelerometer and gyroscope wherein the projectile can inherently calculate its position and issue instructions to the coupling device to guide the projectile 502 to the target 506 without reference to an external targeting system.

[0118] Turning to FIG. 6, there is provided a method flow diagram 600 for controlling a projectile as herein described, the method comprising: [0119] 610: firing the projectile from a barrel; [0120] 620: determining the target location, [0121] 630: calculating guidance commands to change the trajectory of the projectile to intercept the target, [0122] 640: causing said guidance command to instruct the control module to steer the projectile to a target; [0123] wherein in a first arrangement the coupling device is coupled, such that the front section spins at the same angular rotation as the aft section, the projectile travelling in a first helical trajectory, [0124] in a second arrangement the coupling device is decoupled, such that the front section spins at a different angular rotation relative to the aft section, the projectile travelling in a second helical trajectory, [0125] wherein in a first arrangement the coupling device is coupled, such that the front section spins at the same angular rotation as the aft section, the projectile travelling in a first helical trajectory, [0126] said first helical trajectory comprising a smaller radius than the second helical trajectory, comprising the step of selective activation between the first and second arrangements, to cause a change in direction, [0127] 650: thereby enabling the projectile to be steered to the target.