WO2007115998A1

WO2007115998A1 - Device for controlling the initiation of the warhead of a rocket and method for launching the rocket equipped with such a device

Info

Publication number: WO2007115998A1
Application number: PCT/EP2007/053312
Authority: WO
Inventors: Vincent Fraissigne; Grégoire Brisson
Original assignee: Tda Armements S.A.S
Priority date: 2006-04-07
Filing date: 2007-04-04
Publication date: 2007-10-18
Also published as: FR2899679A1

Abstract

The invention relates to rockets (31) with exploding warheads (32) or to similar projectiles and, in particular, to rockets with explosive warheads launched from aircraft. The invention relates to a device intended to be mounted on a rocket (31) that has an exploding warhead to improve the precision of the point of initiation of the warhead by controlling the time of initiation. According to the invention, the moment of initiation is determined by the device by determining the distance (D) covered by the rocket or the journey time that has elapsed since the time of launch. The invention also relates to a method for launching the rocket (31) implementing the device. The invention applies in particular to the firing of rockets (31) with exploding warheads from a helicopter in hovering or traversing flight.

Description

Device for controlling the firing of the charge of a rocket and method of launching a rocket equipped with such a device.

FIELD OF THE INVENTION

The invention relates to rockets with explosive charge or the projectiles assimilated and in particular rockets with explosive charge launched from a helicopter type aircraft, for example.

BACKGROUND OF THE INVENTION - PRIOR ART

The explosive part, or charge, of conventional rockets with explosive heads is fired upon impact. Explosive rockets are rockets whose explosive charge, possibly accompanied by splinters, is intended to cause as much damage as possible around the firing point. Considering the nature of the projectile and its dimensions, the desired effect here is less the total destruction of the objective than the provocation of damage likely to alter the functioning or the general organization of the objective pursued.

This type of projectile is, for example, conventionally used to disrupt convoys of vehicles by causing some convoy vehicles damage sufficient to put them out of order to roll. These immobilized vehicles then require more or less long interventions for their rehabilitation or in the case where this restoration is not possible for their release to an area where they are not likely to impede the progress of other vehicles .

This type of rocket can easily equip a wide variety of vehicles, especially helicopter type aircraft, and allow a quick first response to a detected threat.

In general, the launching of a rocket is performed so that it follows a grazing trajectory whose length is both a function of the initial acceleration suffered by the rocket, and the angle initial fire in the vertical plane given to the rocket by the launch device equipping the launcher, the helicopter for example. Other factors affect the range, for example the speed of translation of the launcher. As regards the initial acceleration, this is given at the moment of launch by firing the rocket propellant, whose operating time is relatively short. For the remainder of the flight following the stopping of the thruster, the rocket follows a ballistic trajectory, essentially a function of the value of the launch angle, the acceleration communicated by the thruster, the initial speed of the launcher , aerodynamic forces suffered and the gravitational attraction to which the rocket is subjected during the entire duration of the flight. The acceleration communicated by the thruster is generally of fixed value, related to the quantity and the energetic value of the substance contained in the propellant. As a result, the only possible action to adapt the length of the trajectory of the rocket to the distance separating the objective of the launcher is to impose a launch angle whose value is such that the trajectory followed by the rocket leads it to hit the ground at the desired impact zone.

Such rockets have the advantage of being a very simple implementation, this implementation does not require in particular that the launcher has sophisticated means. In practice, the launcher measures the distance separating it from the objective and determines the firing angle to be applied from a trajectory model. The firing angle is then applied and the rocket is launched. This type of rocket also has the advantage of being of inexpensive manufacture, insofar as it does not include any trajectory correction device.

On the other hand, all the uncertainties that affect the different parameters determining the trajectory of the rocket have a direct impact on the point of impact. The diagrams in Figures 1 and 2 illustrate the consequences of these inaccuracies on the trajectory followed by the rocket and on the actual position of the point of impact. This vagueness As a result, the point of real impact of the rocket lies in an area of uncertainty around the theoretical point, an area whose size depends in particular on the distance traveled. Because of the extent of the area of uncertainty, the effectiveness of a shot is greatly diminished. Therefore, to achieve the desired disorganization effect, it is usually necessary to fire a large number of rockets. This results in a limitation of the operational capabilities of the launcher, which can carry only a limited number of ammunition, mainly when the launcher is a helicopter.

PRESENTATION OF THE INVENTION

An object of the invention is to solve the problem posed by the existence of the aforementioned uncertainties and to reduce their effect on the operational capabilities of the launcher. For this purpose, the invention relates to a device for controlling the firing of the explosive charge of a rocket, the device being mounted on the rocket, comprising in combination: - means for performing the acquisition and storage a parameter relating to the distance initially separating the rocket from the desired firing point, this parameter being supplied to the rocket by the launcher before the launch,

- means to determine the distance traveled by the rocket since launch,

means for comparing the distance traveled by the rocket with the distance separating at launching the rocket from the desired firing point and for firing the charge when the two distances are equal.

According to an alternative embodiment of the invention, the means for estimating the distance traveled include a timer set to zero at the moment of launching the rocket and the parameter relating to the distance is the travel time required for the rocket to rally. the desired firing point. According to another preferred variant of the invention, the means for estimating the distance traveled comprise an axial accelerometer and the parameter relating to the distance is the same distance initially separating the rocket from the desired firing point; the distance traveled by the rocket being obtained by double integration of the acceleration measured with respect to time.

According to a variant deduced from the preferred embodiment variant, the acquisition means also acquire the speed of the wearer at the moment of launching the rocket, this speed being integrated over time and used for calculating the distance traveled.

According to another variant deduced from the preferred embodiment, the device according to the invention further comprises means for detecting an abnormal variation in the acceleration and firing the rocket when the measured acceleration is considered abnormal. .

The invention also relates to a method for launching an explosive charge rocket comprising a firing control device according to the invention, the method itself comprising the following steps:

a step of measuring the carrier-objective distance and the speed of the carrier,

a step of determining the desired firing point of the charge of the rocket, this firing point being located above and substantially in line with the objective,

a step of determining the theoretical trajectory of the rocket and the firing angle allowing the rocket following such a trajectory to rally the desired firing point,

- a step of pointing the rocket according to the angle of fire,

a step of transmitting the parameters useful for the rocket, a launching step of the rocket; this method being implemented by the wearer.

In addition to the fact that it significantly improves the effectiveness of conventional explosive rockets, the device according to the invention has the advantage of being simple in design, inexpensive and compact. It also has the advantage of not requiring the installation of sophisticated complementary means on the wearer. It can also advantageously be associated with an ignition device on impact.

DESCRIPTION OF THE FIGURES

The characteristics and advantages of the invention will become clear from the description which follows, description accompanied by the appended figures which represent:

for FIGS. 1 and 2: an illustration, in the case of a conventional rocket not equipped with the device according to the invention, of the effects of the uncertainties associated with the firing parameters, in particular with the firing angle, on the position of the point of impact.

for FIG. 3: an illustration of the operating principle of an explosive charge rocket equipped with the device according to the invention,

for FIGS. 4 and 5: schematic diagrams of two variants of the device according to the invention,

- For Figures 6 and 7: curves illustrating for use cases, taken as non-limiting examples, the efficiency gain obtained through the device according to the invention.

DETAILED DESCRIPTION We first consider Figures 1 and 2. These two figures illustrate the technical problem induced by the uncertainties on shooting parameters.

As has been said above, an explosive charge rocket is a projectile comprising a thruster whose operating time is short, and which after the extinction of the thruster a ballistic trajectory. This projectile, simple structure, is also generally not equipped with rudder and can not flex its course. Also, when one wants to launch a rocket on an objective having a given position with respect to the launch vehicle, a helicopter for example, one generally proceeds to a measurement of the distance separating the launcher from the target, then one determines the trajectory allowing the rocket to reach the location of the target. In the case of rockets with explosive heads, the destructive effect is achieved when the rocket hits the ground. We are talking about firing at impact.

The choice of the trajectory is made by choosing the angle of fire. In theory, if the angle of fire is controlled, if the propulsive force has its nominal value and if no external factor, weather or other, disturbs the race of the rocket, it comes into contact with the ground at planned point and explodes in the area where the objects, structures or vehicles are located, which one wishes to damage. In practice, depending on the nature of the launcher, control of the launch angle is more or less complete. Thus, in the case of a helicopter for example, the accuracy with which the rocket is oriented according to the determined firing angle varies according to the qualities of the pilot, depending on the nature of the shot, hovering shot or shot in movement and according to the means available to achieve this orientation. For example, if the helicopter is equipped with steerable launch tubes, the orientation accuracy will probably be better than if the helicopter is equipped with fixed tubes and the orientation is obtained by pitching the aircraft, as illustrated in FIG. Figure 2. In practice, there is also uncertainty about the propulsion force of the rocket. This uncertainty however remains low insofar as it depends in particular on the mass of fuel contained in the propellant, and that this mass is well controlled in manufacturing. It is the same for the mass of the rocket.

Other parameters generate uncertainties: poor knowledge of the speed of the carrier at the moment of the shot, aerodynamic disturbances related to the rocket itself or to external factors (wind for example).

The result of these inaccuracies is that, as shown in particular in the diagrammatic view from above of FIG. 1, the point of impact for a given rocket lies in a domain 11 delimited by an ellipsoid centered on the zone 12 chosen as objective and whose axis passing through the foci corresponds substantially to the axis

13 connecting the launcher 14 to the objective 12.

As a result, in the current state of the art, it is often necessary to achieve the designated goal of firing a large number of rockets, a significant portion of which does not reach the target, but will strike the ground somewhere within the dispersion zone 11.

The length I of the minor axis of the ellipsoid is also a function, in particular, of the product of the angular error α, produced on the direction of launch in the bearing, by the distance D separating the thrower from the objective. The length L of the major axis can, in turn, be calculated by considering the range deviation obtained when the actual firing angle in the vertical plane differs more or less from the theoretical firing angle of the maximum value. of the error. In the case of a firing on a relatively tense trajectory, for which the firing angle is small, it is possible to simply estimate the length of this axis by considering the height h at which the rocket is located as it passes. in line with the objective during a too long shot represented by the trajectory 21 in FIG. 2. The distance L from the point where the objective is situated to the point of impact 22 can then be approximated by the quotient of the height h by the tangent of the arrival angle θ of the rocket relative to the horizontal.

Thus, for example, for an angular dispersion at a bearing of α equal to 1 °, the lateral dispersion of the point of impact (small axis I of the ellipsoid 11), at a distance of 2 km, will have a value of approximately 35 m. Similarly, for an angular dispersion in site β equal to 1 ° with respect to the nominal firing angle e and an angle of arrival θ of 5 °, h will be of the order of 35m and the dispersion in range around point of impact (long axis L of the ellipsoid) can be estimated at about 400m. It should be noted that, as illustrated in Figure 1 and as shown in the example, the range of dispersion of the point of impact is much greater, for angular errors identical in the field and in the site, the lateral dispersion, which justifies the ellipsoid shape of the dispersion zone 11.

FIG. 3 is now considered which illustrates the operating principle of the device according to the invention.

The device according to the invention aims to reduce the loss of efficiency due to dispersion over the distance between the actual point of impact and the launch point. Lateral dispersion, considered acceptable elsewhere, is not subject to any particular treatment. More specifically, the device according to the invention proposes to reduce the distance between the firing point of the load and the target.

FIG. 3 represents the case of a shot that is too high, such as the trajectory 21 of FIG. 2. The case of a shot too short, such as the trajectory 23 of FIG. 2, will be described later: this situation will be avoided by introducing a systematic bias upward on the firing angle. As illustrated in Figure 3, the device according to the invention has for main object to operate a firing of the rocket 31 conditioned by a distance criterion. For this purpose it is designed to determine the distance traveled by the rocket at any time after the launch, then to compare this distance with the distance D separating the launcher from the desired firing point. When the distance traveled is equal to the distance D, the charge of the rocket is fired. The firing point 32 is, according to the invention, defined as a point of the trajectory located in line with the zone 12 corresponding to the objective to be achieved. For the trajectory 21, where the rocket is fired with an initial angle of e + β, the firing of the charge will occur at the height h above the ground.

If we take as for the previous example a shot made on an objective located at a distance D equal to 2km, and a dispersion β on the firing angle of the rocket equal to 1 °, we obtain in the vertical plane a distance between the firing point and the target equal to h, which is approximately 35 meters. This value is therefore advantageously comparable to the lateral dispersion which affects the position of a conventional rocket, known from the prior art. Thanks to the firing device according to the invention, the effectiveness of the rocket is thus advantageously no longer affected by the position of the point of impact that would correspond to the extension of the actual trajectory followed by the rocket.

FIGS. 4 and 5 are now considered. These show in a synoptic manner all the means that make up the device according to the invention, according to two variant embodiments.

The device according to the invention is an autonomous device that fires the charge of the rocket at a time corresponding to the passage of the rocket in line with the objective to be damaged.

To determine when the rocket passes to the corresponding point, the device according to the invention determines in a first embodiment, illustrated in Figure 4, the time elapsed since the launch of the rocket. This time is compared to the travel time required for the rocket to reach the desired firing point, the launcher calculated travel time based on the distance to which the objective and the speed of the launcher, if this one makes a shooting in movement. When the elapsed time measured by the device is equal to the time of theoretical course provided by the launcher, the device according to the invention explodes the charge of the rocket which is then in line with the objective.

In this variant embodiment, the device according to the invention therefore comprises acquisition means 41 for acquiring and storing the parameters supplied by the launcher. Among these parameters are mainly the theoretical travel time required for the rocket to reach the explosion point 32 from the launcher. The device according to the invention also comprises, in this variant, means 42 for determining the time elapsed since the launch of the ammunition, a chronometer for example. These means are set to zero by the launcher, or on its order, at launch. Finally, the device comprises decision means 43 which compare the elapsed time with the stored travel time and which cause the load of the rocket to explode as soon as the measured time is equal to the desired travel time.

In a second variant embodiment, a preferred variant illustrated in FIG. 5, the device according to the invention, in order to be able to determine when the rocket passes in line with the objective, determines the distance traveled by the rocket since the launch. . The distance traveled is compared with the distance D separating the thrower from the objective, distance which in the case of a shooting along a grazing trajectory is substantially equal to the distance that the rocket must travel along its trajectory. As soon as the distance traveled is equal to the theoretical distance of travel, the device according to the invention detonates the load of the rocket which is then in line with the objective. In this second embodiment, the device according to the invention therefore comprises acquisition means 51, intended as means 41 to acquire and store the useful parameters provided by the launcher. The useful parameters are here mainly the theoretical distance of course and the own speed of the launcher, if it launches a shooting in motion. The device according to the invention also comprises, in this second variant, means 52 for determining at any moment the distance traveled. The means 52 consist mainly of an accelerometer 53 making it possible to determine the axial acceleration of the rocket, followed by a dual integrator 54. The means 52 thus perform the calculation of the distance traveled by performing a double integration over time. measured acceleration. The first integration allows to determine at any moment the current speed of the rocket from the speed of the launcher and the measured acceleration. The integration of the speed makes it possible to determine the distance traveled.

Gravity is not measured by the accelerometer 53. When calculating the distance traveled it can be either neglected or added on the basis of a theoretical value of its component on the rocket axis. The device further comprises decision means 55 which compare the distance traveled to the length of the theoretical trajectory separating the rocket at the time of launching the desired explosion point. As soon as the distance traveled is equal to the length of the theoretical trajectory the means 55 explode the charge of the rocket.

This second variant also advantageously makes it possible to implement means making it possible to detect an abnormal acceleration of the rocket. Such a situation can then be reported to the decision means which, in the event that this variation is considered unacceptable, can trigger the firing of the load.

To make the most of the device according to the invention, it is possible to voluntarily increase the firing angle of the rockets so that the rocket always reaches the objective of the objective, even for a shot too short . In the case of a nominal fire, the rocket will then fly over the objective at an altitude H. For a shot too long, the target will be flown at an altitude higher than H. A compromise must be sought at the level of the increase of the angle of fire so that the the benefit obtained on the trajectories that are too short is not canceled out by the increase in distance between the firing point and the target introduced for the other trajectories.

As a result, a method for launching an explosive charge rocket comprising a firing control device according to the invention making it possible to make the most of the device can be described by the following steps:

a step of determining the theoretical trajectory of the rocket and the firing angle allowing the rocket following such a path to reach the firing point,

- a step of pointing the rocket according to the angle of fire,

a step of transmitting the parameters useful for the rocket, a launching step of the rocket;

Nevertheless, it is of course possible to use the rockets equipped with a firing device according to the invention with a launcher only capable of determining the trajectory leading the rocket to an impact on the objective. The remainder of the description shows in this connection that even in this configuration the device according to the invention increases the efficiency of the shots.

We are now interested in FIGS. 6 and 7. The curves presented by these two figures make it possible to demonstrate the advantageous nature of the device according to the invention. These two figures correspond to an exemplary implementation of the device according to the invention. In this example, we consider a short-range fire from a helicopter-type launcher hovering for the figure. 6, and moving for Figure 7. In this example, the objective is a group of vehicles.

The gain on the effectiveness of a rocket with explosive head is studied according to whether it is equipped with the device according to the invention. The imperfections of the device are taken into account through the dispersion at 1σ over the firing distance, including both the measurement error of the carrier-target distance and the measurement error of the distance traveled. In these figures, the horizontal line of ordinate 1 corresponds to the effectiveness of a rocket with conventional explosive head, not equipped with the device according to the invention.

In this example we present the case where the rocket according to the invention is drawn without modification of the firing angle, the firing being carried out in the same way as for a conventional rocket (curves 61 and 71 in dashed lines), and the case or the angle of fire is increased voluntarily (shooting offset) so that the nominal trajectory of the rocket passes above the objective (curves 62 and 72 in full lines). The introduction of an offset makes it possible to increase the effectiveness of the shot by avoiding impacts ahead of the target. These impacts resulting from trajectories that are too short do not allow the firing device according to the invention to operate and the rocket is then destroyed by the firing system on impact. The introduction of an offset also makes it possible to reduce the collateral damage following the rocket explosion for which the dispersion in site would have generated angles of fire too weak.

The study of FIGS. 6 and 7 shows that the device according to the invention makes it possible to substantially increase the firing efficiency, even in the less favorable cases where the firing of rockets equipped with the device according to the invention is achieved by the same way (without offset) as that of conventional rockets.

Claims

1. Device for controlling the firing of the explosive charge of a rocket, said device being mounted on the rocket and comprising in combination:

means for acquiring and memorizing a parameter relative to the distance initially separating the rocket from the desired firing point, this parameter being supplied to the rocket by the launcher before the launch,

- means for determining the distance traveled by the rocket since launch, - means for comparing the distance traveled by the rocket to the distance separating at the launching time the rocket from the desired firing point and to perform the firing rocket when the two distances are equal.

2. Device according to claim 1, wherein the means for estimating the distance traveled comprises a timer set to zero at the moment of launching the rocket, the parameter relating to the distance initially separating the rocket from the desired firing point. being the travel time required for the rocket to reach the desired firing point.

3. Device according to claim 1, wherein the means for estimating the distance traveled comprises an axial accelerometer, the parameter relating to the distance initially separating the rocket from the desired firing point being this distance itself; the distance traveled by the rocket being obtained by double integration of the acceleration measured with respect to time.

4. Device according to claim 1, wherein the means for estimating the distance traveled comprise an axial accelerometer, the parameter relating to the distance initially separating the rocket from the desired firing point being this distance itself; the distance traveled by the rocket being obtained by double time integration of the measured acceleration completed by a term representing the influence of gravity.

5. Device according to any one of claims 3 or 4, wherein the acquisition means also acquire the speed of the wearer at the time of firing, this speed being integrated over time and used for calculating the distance traveled.

6. Device according to any one of claims 3 to 5, further comprising means for detecting an abnormal variation of the measured acceleration and firing the charge of the rocket when the measured acceleration is considered abnormal .

7. A method for launching an explosive charge rocket comprising a charge firing control device according to any one of the preceding claims, characterized in that it comprises at least the following steps:

a step of measuring the carrier-objective distance, a step of determining the desired firing point of the charge of the rocket,

a step of determining the theoretical trajectory of the rocket and the firing angle allowing the rocket following such a path to reach the desired firing point, a step of orienting the rocket in accordance with the firing angle,

a step of transmitting the parameters useful for the rocket,

- a launching stage of the rocket; this method being implemented by the launcher.

8. The method of claim 7 further comprising a step of measuring the speed of the carrier.

9. A method according to any one of claims 7 or 8 wherein the desired firing point is above and substantially in line with the objective.