RO132502B1 - Process for correcting the trajectory of a projectile - Google Patents

Description

The present invention is in the field of self-propelled artillery projectiles and relates to a device for correcting the trajectory of a projectile. The invention also relates to a method of correcting the trajectory of a projectile.

The European patent application EP 1783451 A2 is known which refers to an artillery projectile stabilized by a rotational movement, which has, in the warhead, a braking device, which reduces the longitudinal deviation of the projectile trajectory, and on the circumference of the projectile, by a number of elements that can generate impulses, which, judiciously operated, can reduce the transverse deviation of the actual point of impact of the projectile in the target area from the point initially aimed by the sight.

International patent application WO 02/061363 A2 discloses a two-axis projectile trajectory correction system, improving the trajectory of the post-launch spin-stabilized artillery projectile by tracking it with a detection system, which includes: a distance adjustment system, located inside the artillery projectile stabilized by rotation, a deflection adjustment system, also located in the artillery projectile and a command module, located in the artillery projectile, but operationally coupled to the control system distance adjustment and to the yaw adjustment system.

In the present application, the invention is described with a ground-to-ground self-propelled projectile, i.e. a self-propelled projectile launched from the ground and whose impact position is on the ground, but it can be applied in the same way to an air-to-ground self-propelled projectile launched from an aircraft or a sea-to-surface, sea-to-sea or surface-to-sea self-propelled projectile launched from or towards a ship. More generally, the invention applies to any projectile that is not guided.

A self-propelled artillery projectile is propelled by means of a propellant. In recent years, developments in self-propelled projectile boosters have allowed their range to be greatly increased. Indeed, thanks to a new motorization, that is, through an additional supply of energy to the engines, the range of a self-propelled projectile could be multiplied by two, going from about 20 km to 40 km. A self-propelled projectile being an unguided projectile, there are dispersions on impact. In other words, a nominal (and therefore desired) trajectory is provided when launching the self-propelled projectile. But in practice, the actual trajectory of the self-propelled projectile differs from the nominal trajectory. This results in scatter on impact, meaning the impact of the self-propelled projectile is not the original intended impact. The self-propelled projectile having an explosive head, a dispersion on impact can cause numerous collateral damages. And this dispersion on impact is even more important than the range of the self-propelled projectile.

In order to improve the performance of self-propelled artillery projectiles, both an increase in their range due to the improvement of the performance of the propellants and also a minimization of the dispersion upon impact are needed.

There are several possibilities for minimizing dispersion. First, it is possible to convert the self-propelled projectile (unguided projectile) into a missile (guided projectile). This transformation is complex and expensive. Indeed, this requires the integration of a continuous identification system of the projectile position and a continuous piloting system throughout the trajectory. There are also correction devices with a satellite geolocation system (known by the abbreviation of GPS from its Anglo-Saxon acronym Global Positioning System). This type of device, in addition to being quite expensive, is limited for its user, as it forces the latter to obtain the necessary rights to use the satellite network in question. Moreover, trajectory corrections are made at the level of some side thrusters. Thrusters are certainly very effective at making lateral trajectory corrections, but they are not very effective at making a longitudinal correction. Therefore, it is necessary to mount a large number of thrusters, which means a much larger size and mass of the assembly, resulting in a limitation of the range and also requiring the possible adaptation of the launchers. 3

The invention aims to overcome all or part of the problems mentioned above by proposing a trajectory correction device by applying to the projectile on the one hand a sequence of discrete corrections and on the other hand a deployment of an aerodynamic brake on its trajectory, after finding at the beginning of the trajectory a 7 deviation between the nominal trajectory and the real trajectory of the projectile.

For this purpose, the object of the invention is a device for correcting a real trajectory 9 of a projectile intended to travel a nominal trajectory, characterized in that it comprises:11

- a propellant positioned on the projectile and intended to bring a lateral correction to the actual trajectory of the projectile;13

- an aerodynamic brake positioned on the projectile and intended to bring an axial correction to the real trajectory of the projectile;15 and in that it includes:

- a means of correction of the trajectory incorporated on the projectile, capable of activating 17 the propellant and the aerodynamic brake;

- a means of measuring the real trajectory of the projectile, intended to determine a deviation between the real trajectory and the nominal trajectory;

- a calculation means for determining a sequence of at least one correction in 21 deviation functions;

- means for transmitting the sequence from the computing means to the trajectory correction means.

According to one embodiment, the device comprises a modular block, and the modular block 25 may comprise the trajectory correction means and the thruster.

According to another embodiment, the projectile being launched from a launch module 27, the launch module comprises means for measuring the actual trajectory, calculation means and transmission means. 29

Advantageously, the projectile being comprised of a warhead and a propellant configured to be removably secured relative to each other, the modular block is positioned between the warhead and the propellant. 31

Advantageously, the aerodynamic brake is positioned on the thruster.

Advantageously, the modular block additionally comprises the aerodynamic brake. 33

Advantageously, the projectile being launched from a launch module, the correction means comprises: 35

- an antenna intended to allow communication with the launch module;

- an information storage means intended for recording the sequence of at least one 37 correction;

- a means of storing electrical energy intended to feed the means of correction; 39

- a timer;

- a device for determining the rolling position of the projectile, 41

- a thruster and airbrake activation unit.

The invention also has as its object a method of correcting a real trajectory 43 of a projectile intended to travel a nominal trajectory, implementing the correction device, comprising the following successive steps: 45

- measuring the real trajectory of the projectile by means of the measuring device and determining the deviation between the real trajectory and the nominal trajectory; 47

- determination by means of the means of calculation of the sequence of at least one correction according to the deviation; 49

- transmission of the sequence from the calculation means to the trajectory correction means;

- activation by means of correction means of the thruster and the aerodynamic brake according to the transmitted sequence.

Advantageously, the actual trajectory of the projectile comprising a first phase during which the correction means is able to communicate with the transmitting means and a second phase during which the correction means is autonomous, measuring the actual trajectory of the projectile, determining the sequence of at least of a correction and transmission of the sequence to the correction means are done during the first phase, and activation of the thruster and airbrake are done in the second phase.

Advantageously, the correction brought by the propellant is unobtrusive.

Advantageously, the correction brought by the airbrake is unobtrusive.

The invention will be better understood and other advantages will appear upon reading the detailed description of an exemplary embodiment, a description illustrated by the accompanying drawing in which:

- fig. 1, schematically represents a condition in which the invention can be implemented;

- fig. 2, schematically represents a first embodiment of the device according to the invention;

- fig. 3, schematically represents a launch module from which the projectile can be launched;

- fig. 4 and 5 schematically show a projectile comprising a correction device according to the invention, according to a second and a third embodiment;

- fig. 6, schematically represents a correction means of the correction device according to the invention;

- fig. 7, illustrates steps of the method of correcting a real trajectory of a projectile intended to travel a nominal trajectory, according to the invention;

- fig. 8, is a schematic representation of a nominal trajectory and an actual trajectory of a projectile.

For clarity, the same elements will bear the same references in different figures. For better visibility and increased understanding, elements are not always represented to scale.

Fig. 1 schematically represents a condition in which the invention can be implemented. A self-propelled projectile is propelled from a launcher 10 which most often consists of a cylindrical hollow tube. In fig. 1, the launcher 10 is positioned on a man's shoulder. The launcher can also be positioned on a stabilized or unstabilized truck, or on a fixed mount on a ship. The conditions under which such a projectile is propelled are a source of dispersion in the trajectory of the projectile. It is easy to understand that from a support such as a human that is not completely still or an unstabilized vehicle, it will be difficult to obtain an actual trajectory that is the desired nominal trajectory, since differences in projectile positioning can occur by at launch. Additionally, near land or sea, weather conditions are also a source of dispersion in projectile trajectory. Indeed, the trajectory of the projectile is also sensitive to variations in pressure, temperature, local turbulence, especially related to wind. These external conditions are difficult to control and generate dispersion upon projectile impact. Similarly, in the case of an air-to-ground self-propelled projectile launched from, for example, a helicopter, the wind from the helicopter's rotor will disrupt the trajectory of the self-propelled projectile at the start of the launch phase.

Finally, propellant characteristics may also play a role in impact dispersions.

The Circle of Probable Error (known by its abbreviation CEP) allows quantification of the contribution of different sources of projectile dispersion. It was found that the main causes of the dispersion, or about 80% of the CEP, are concentrated on the first tenth of the 3 trajectories. In other words, the vast majority of projectile trajectory dispersion is generated by projectile launch and the start of the firing phase. In order to correspond to the desired nominal trajectory, any real trajectory must therefore be potentially corrected, radially and/or axially. 7

Fig. 2 schematically represents a first embodiment of a device 11 according to the invention. A projectile 12 is intended to travel a nominal trajectory. The device 9 correction 11 of a real trajectory, according to the invention, comprises a propellant 13 positioned on the projectile 12 and intended to bring a lateral correction to the real trajectory of the projectile 12. 11

It comprises an aerodynamic brake 14 positioned on the projectile 12 and intended to bring an axial correction to the actual trajectory of the projectile. The correction device 11 comprises a trajectory correction means 15 incorporated on the projectile 12, capable of activating the thruster 13 and the aerodynamic brake 14. More precisely, the trajectory correction means 15 is a means of piloting the trajectory correction devices. The correction means 15 is capable of piloting the thruster 13 and triggering the aerodynamic brake 14. The correction device 17 comprises a measuring means 16 of the actual trajectory of the projectile 12, intended to determine a deviation between the actual trajectory and the nominal trajectory. The correction device 19 comprises a calculation means 17 intended to determine a sequence of at least one correction according to the deviation. The correction device 11 comprises a transmission means 18 of the sequence 21 from the calculation means 17 to the trajectory correction means 15.

The correction device 11 may comprise a modular block 19 and the modular block 23 19 may comprise the trajectory correction means 15 and the thruster 13.

Fig. 3 schematically represents a launch module 20 from which the projectile 25 12 can be launched. The launch module 20 can comprise the means of measuring 16 of the real trajectory, the means of calculation 17 and the means of transmission 18. 27

Fig. 4 and 5 schematically represent the projectile 12 comprising a correction device 11 according to the invention, according to a second and a third embodiment. The projectile 12 is 29 comprised of a warhead 21 and a propellant 22 configured to be removably secured to each other. According to the invention, and as represented in fig. 4, the modular block 19 can be positioned between the head 21 and the thruster 22. This configuration is particularly advantageous. Indeed, in addition to being compact, it has the advantage of being compatible with existing material. It is therefore possible to use a pre-existing head 21 and a thruster 22 and to insert between the head 21 and the thruster 22 the modular block 19. 35

As represented in fig. 5, the aerodynamic brake 14 can be positioned on the propeller 14 or at the level of the head 21. The aerodynamic brake 14 can be positioned in any position on the propeller 14. In particular, it can be positioned at the rear of the propeller 14 at the level of the stabilizer. The airbrake 14, once actuated, increases 39 the forward resistance of the projectile 12, which then allows the distance traveled by the projectile 12 to decrease. As already mentioned above, the airbrake 14 will thus allow 41 an axial correction of the actual trajectory of the projectile 12.

Alternatively, the modular block 19 may additionally comprise the aerodynamic brake 14. 43

In other words, in such a configuration, the thruster 13 and the aerodynamic brake 14 are integrated into the modular block 19. 45

Fig. 6 schematically represents a correction means 15 of the correction device 11 according to the invention. The correction means 15 may comprise an antenna 23 intended to enable communication with the launch module 20, an information storage means 24 intended to record the sequence of at least one correction, an electrical energy storage means 25 intended to supply the correction means 15 , a timer 26, a device for determining the roll position 27 of the projectile 12, an activation unit 28 of the thruster 13 and the aerodynamic brake 14. The timer 26 allows the measurement of elapsed time and will allow the correction means 15 to determine when to activate the thruster 13 and/or the airbrake 14. The roll position determination device 27 will allow the correction means 15 to determine precisely when to activate the thruster 13. Indeed, since the thruster brings a lateral correction and the projectile 12 being in rotation itself during its trajectory, it is important that the propellant 13 fires at the right time when the projectile 12 is in the correct roll position. In other words, the correction means 15, in the correction sequence, knows that from a given moment it is necessary to trigger a propellant 13 when the projectile 12 has the appropriate roll. The rolling position determination device 27 can be, for example, a magnetometer or a gyroscopic system.

Fig. 7 illustrates the steps of the process of correcting an actual trajectory of a projectile 12 intended to travel a nominal trajectory, according to the invention. The correction procedure includes the following successive stages:

- measuring the real trajectory of the projectile 12 by the measuring means 16 and determining the deviation between the real trajectory and the nominal trajectory;

- determination by the calculation means 17 of the sequence of at least one correction according to the deviation;

- transmission of the sequence from the calculation means 17 to the trajectory correction means 15;

- activation by means of the correction means 15 of the thruster 13 and the aerodynamic brake 14 in accordance with the transmitted sequence.

The actual trajectory of projectile 12 can be divided into two phases. The actual trajectory of the projectile 12 then comprises a first phase during which the correction means 15 is able to communicate with the transmission means 18 and a second phase during which the correction means 15 is autonomous. Measuring the actual trajectory of the projectile 12, determining the sequence of at least one correction, and transmitting the sequence to the correction means 15 are done during the first phase. The activation of the thruster 13 and the aerodynamic brake 14 is done during the second phase.

Fig. 8 is a schematic representation of a nominal trajectory 30 and an actual trajectory 31 of a projectile 12. By initiating a firing of the projectile 12, this projectile 12 is desired to follow a nominal trajectory 30. For the reasons previously explained, disturbances will generate dispersions at the level of the real trajectory 31 of the projectile. These disturbances occur mainly in the first phase 33 of the trajectory. Once projectile 12 is launched, the trajectory correction procedure is implemented. First, after about 10% of the trajectory, the actual trajectory measuring means 16 of the projectile 12 determines a deviation between the actual trajectory 31 and the nominal trajectory 30 of the projectile 12. The measuring means 16 may be a conventional beam trajectory determining radar of short action, because intervening in the first phase 33 of the trajectory, the projectile is still at a short distance from the measuring means 16. The calculating means 17 determines a sequence of at least one correction according to the deviation determined in the previous stage. The calculation means 17 can therefore determine a sequence of one or more necessary corrections depending on the deviation. The calculation means can be any specific software and using a trajectory determination with six degrees of 1 freedom. Advantageously, the calculation means 17 is implanted on the measuring means 16 of the actual trajectory 31. But it can also be separate. Once the correction sequence 3(s) is determined, the latter is transmitted to the trajectory correction means via the sequence transmission means 18 from the computing means 17. The transmission means 5 18 is generally ground based (or in aircraft or even on a ship, in the respective case, of an air-to-ground or sea-to-ground self-propelled projectile) and dialogues in 7-wire communication with the computing means 17. One can also imagine a different mode of communication between the computing means 17 and the transmission medium 18, for example a wireless communication mode 9. The transmission means 18 communicates with the correction means 15 positioned on the projectile 12 via radio frequency. It may be, for example, a means of transmission by 11 short-range radio frequency communications. More generally, it can be any other transmission means for transmitting information between the calculation means 17 and the correction means 13 15. The transmission of information between the transmission means 18 and the projectile 12 is done in the first phase 33 of the trajectory during which the means of correction 15 is able to 15 communicate with the transmission means 18, that is, when the projectile 12 has not moved too far from its launch module 20. This configuration has the advantage of gathering all 17 the computing power (measuring means 16, computing means 17, means of transmission 18) and keep it on the ground. In other words, once projectile 12 has been fired, computing power does not19 leave with projectile 12. It is retained and can be used again for another fire.21

Then the second phase 34 begins during which the correction means 15 is autonomous.

In other words, as soon as it enters the second phase 34 of its trajectory, the projectile 12 is 23 too far from the transmission means 18 to receive any further information. Since the transmission means 18 has transmitted the correction sequence(s) to the correction means 25 positioned on the projectile 12, the correction means 15 then activates the thruster 13 and the aerodynamic brake 14 according to the transmitted sequence to make the necessary corrections 27 so that the actual trajectory of the projectile 12 to correspond to the initially desired nominal trajectory. 29

The correction device 11 may comprise several thrusters. Each thruster generates a calibrated lateral thrust upon firing. Generally, 4 to 31 per 10 thrusters are required 13. This choice represents a good compromise between efficiency and built-in mass. The firing of a thruster 13 is determined according to the calculated correction sequence 33. The device for determining the rolling position 27 of the projectile 12 and the timer will determine at what moment the activation unit 28 will activate the propellant 13. Furthermore, for the proper development of the correction sequence, the compatibility between the rotation speed of the projectile 12, the time trigger and possible trigger dispersions. 37

Each thruster 13 provides a discrete radial correction to the trajectory of the projectile 12.

The release of the aerodynamic brake 14 is also determined by the sequence of 39 corrections. The correction device may comprise several air brakes, but in general a single brake is sufficient. Indeed, the aerodynamic brake 14 brings a discrete axial correction 41 to the trajectory of the projectile 12. It is enough to make it so that there is a trajectory whose impact will be farther axially than desired and to activate the aerodynamic brake 43 once 14.

Finally, the projectile 12 follows an actual corrected trajectory 35 whose impact corresponds to that of the nominal trajectory 30. In general, the correction device 11 allows 3 an accuracy gain of about a factor of 5 to 10. This accuracy gain is of critical importance because the projectile may be fitted with a unitary warhead, and any gain in accuracy may translate into a reduction in collateral damage and/or an improvement in the impact efficiency of the weapon. Moreover, the correction device according to the invention has many other advantages. Indeed, it is cheap, independent of satellite geolocation systems, modular and compatible with already existing material.

Claims (3)

Claims 1 1. Method of correcting the actual trajectory (31) of a projectile (12) intended to travel a nominal trajectory (30), the projectile (12) being equipped with a thruster (13) for lateral trajectory correction, an aerodynamic brake ( 14) and trajectory correction means (15) cooperating with a launch module (20) comprising projectile trajectory measurement means (16), calculation means (17) and transmission means (18) ), the actual trajectory (31) being composed of a first phase (33), in which the projectile (12) is near the launch module (20) and the correction means (15) is able to communicate with 9 the transmission means (18), and a second phase (34), in which the correction means (15) is autonomous, characterized in that it comprises the following successive stages separated on the two phases of the projectile trajectory as follows: In the first phase (33):13 - measurement of the actual trajectory (31) of the projectile (12) by the measuring means (16);15 - determining the deviation of the real trajectory (31) from the nominal trajectory (30); - determination by the calculation means (17) of a sequence of corrections; 17 - transmission by the transmission means (18) of the sequence of corrections to the correction means (15); 19 And in the second phase (34): - triggering the correction sequence by the correction means (15); 21 - activation of the thruster (13) for lateral correction of the trajectory and the aerodynamic brake (14) according to this sequence.23 2. Trajectory correction method according to claim 1, characterized in that the correction brought by the lateral trajectory correction thruster (13) is discrete.25 3. Trajectory correction method according to claims 1 or 2, characterized in that the correction brought by the aerodynamic brake (14) is discrete.27