EP0610129A1 - Method for launching and controlling, from a moving vehicle, a non-vertically guided projectile with braked trajectory - Google Patents

Abstract

Method of launching a projectile (2) which is not guided vertically, with a trajectory (5) which is compound, free, of adjustable duration, then retarded, against a target (4) from a moving vehicle (1) in which method, before launch, and for various positions of the vehicle (1), the target (4) is identified, the distance from the target (4) to an anticipated virtual trajectory at maximum range (6) of the projectile (2) is calculated and the projectile (2) is launched after the said distance has crossed a minimum, and then, in the calculation, the maximum-range trajectory (6) is replaced by a compound trajectory (25), in which the transit time (TB1) of the free trajectory (26) is controlled in such a way that the distance from the target (4) to the trajectory of the projectile (25) remains equal to this minimum and the projectile (2) is sent a free-trajectory transit time signal (26). <IMAGE>

Description

• 1- on détermine la position de la cible dans un repère tridimensionnel lié au véhicule,
• 2- on fixe ladite durée réglable à une valeur maximale, on calcule, en tenant compte de la vitesse du véhicule et dans ledit repère, la trajectoire virtuelle anticipée du projectile, de portée maximale,
• 3- on calcule la distance de la cible à ladite trajectoire virtuelle et
  • - on lance le projectile après que ladite distance ait franchi un minimum.

The present invention relates, first of all, to a method of launching and controlling on a target, from a mobile vehicle, at least one projectile not guided vertically, with mixed trajectory, with free portion, of adjustable duration , then with a braked portion, in which, in a first phase of approach before launching, and for each of various successive positions of the vehicle,

• 1- the position of the target is determined in a three-dimensional frame linked to the vehicle,
• 2- the said adjustable duration is fixed at a maximum value, the speed of the vehicle is calculated, taking into account the speed of the vehicle and in said reference, the anticipated virtual trajectory of the projectile, of maximum range,
• 3- the distance from the target to said virtual trajectory is calculated and
  • - the projectile is launched after said distance has crossed a minimum.

To launch from a mobile vehicle, for example an aircraft, a vertically unguided projectile, such as a bomb or a rocket, the pilot gives the aircraft an appropriate drop angle so that the target is on the trajectory of the projectile. In the case of an airplane, this angle is determined by its trajectory, while, in the case of another vehicle, on land or at sea, it can, for example, rockets, be adjusted by pivoting the launching device. The free trajectory portion is followed by a braked trajectory portion, a parachute then braking the bomb in order to improve the angle of impact on the ground, so that it explodes and, if possible, reaches the target under a sufficient impact angle to guarantee the desired effectiveness.

There was the problem of precisely regulating the trajectory of the bomb and in particular the angle, or slope, and the moment of launching, otherwise the bomb fell "short" or exceeded the target.

Furthermore, if the aircraft must, in a single attack pass, send several bombs to the target, it cannot launch them simultaneously because there would be a risk of collision between these bombs.

To avoid this risk, the drops are carried out successively, leaving a safety time interval between them. Each bomb then had its own trajectory, therefore, in general, incorrect. The problem of adjusting the trajectory to obtain a group fire also arose when the bombs had different masses or ballistic characteristics.

As a result, it was necessary to "water" an entire area with a greater number of bombs and the aircraft would possibly make several passes, with the risks that this entailed.

Also, when the target spans a large area, such as an airstrip, more bombs are needed to cause sufficient damage. The problem then was to carry out a concentration fire by distributing the impact points evenly, so as not to waste projectiles.

Both of the above problems, group fire or concentration fire, are related to the fundamental problem of adjusting the range of bombs in the vertical plane of their trajectory.

The present invention aims to solve the problem of range adjustment.

• - dans une seconde phase d'approche, on détermine la position de la cible, on fixe ladite durée réglable, on calcule une trajectoire virtuelle anticipée du projectile comme lors de la première phase d'approche, mais en remplaçant, dans le calcul, après franchissement dudit minimum, la trajectoire de portée maximale par une trajectoire mixte dont on asservit la durée de parcours de la portion de trajectoire libre par le minimum de ladite distance de la cible pour que, pour chacune des diverses positions du véhicule lors de cette seconde phase d'approche, la distance de la cible à la trajectoire du projectile soit égale à ce minimum et, avant l'expiration de ladite durée de parcours du projectile, on transmet au projectile un signal de durée de parcours de portion de trajectoire libre.

To this end, it relates to a process of the type mentioned above, characterized in that:

• - in a second approach phase, the position of the target is determined, said adjustable duration is fixed, an anticipated virtual trajectory of the projectile is calculated as during the first approach phase, but replacing, in the calculation, after crossing of said minimum, the maximum range trajectory by a mixed trajectory for which the duration of travel of the portion of free trajectory is controlled by the minimum of said distance from the target so that, for each of the various positions of the vehicle during this second phase approach, the distance from the target to the trajectory of the projectile is equal to this minimum and, before the expiration of said duration of travel of the projectile, a signal of duration of travel of portion of free trajectory is transmitted to the projectile.

Thus, whatever the conditions for launching the projectile, the latter is braked at the right time so that its trajectory reaches the target.

It will be noted that the relative position of the target, when the latter is mobile, can be predicted and account can be taken of its expected displacement during the free flight time of the projectile.

Advantageously, the impact angle on the ground of the trajectory of the projectile is calculated during the first phase as well as during the second approach phase and the launch is prohibited until a projectile trajectory is present, with horizontal, an angle of impact greater than a determined value.

In this case, the braked portion of the trajectory did not always have the time necessary for the bomb to have the best efficiency, with an effect in a sector completely surrounding its point of impact.

The problem of the effectiveness of the projectile is thus resolved since the projectile not only reaches the target, but strikes it, if it has a horizontal surface, at an angle of impact sufficient to ensure the effectiveness of its action.

In addition, it is possible to carry out a group fire of projectiles launched successively towards the same point of a quasi-point target, or of projectiles of different masses or aerodynamic characteristics, possibly launched simultaneously. We then proceed for all the other projectiles as for the first launched.

When several projectiles must be launched in a so-called concentration shot, respectively at several points on a target, the projectiles are assigned respectively several points of impact on the target and a duration of free trajectory portion is transmitted to each projectile as a function of the position of the corresponding point of impact.

This provides the desired distribution of impact points.

The invention also relates to a post-launch guidance method according to the launch method of the invention, in which, the projectile comprising a data receiver arranged to cooperate, after launch, with a transmitter of the vehicle, one continues, after launch , the calculation of a virtual trajectory of the projectile coinciding with its real trajectory and the corresponding signals of travel time of the portion of free trajectory are transmitted to the projectile.

• - la figure 1 représente un avion et des trajectoires prévues de bombes et
• - la figure 2 est un schéma par blocs illustrant le procédé de l'invention.

The invention will be better understood using the following description of the preferred embodiment of the method of the invention, with reference to the appended drawing, in which:

• FIG. 1 represents an airplane and planned trajectories of bombs and
• - Figure 2 is a block diagram illustrating the method of the invention.

An airplane 1 carries, in this example, two bombs 2 and 3, here similar, which must hit a target 4, here on ground 5.

There is, on board the aircraft 1, a viewfinder 11 providing a signal 19 making it possible to acquire the relative position of the target 4 relative to the aircraft 1. In this example, the viewfinder 11 comprises an optical orientable sight associated with a computer (not shown). The angle of sight of the optics with respect to a reference stabilized with respect to the earth and indications of position of the airplane 1 in this reference, coming from a set 12 inertial unit-computer of the airplane 1, are provided to the viewfinder 11 to generate the signal 19. It will be understood that a precise navigation device could just as easily provide the position of the target 4 without having to see it.

There is also, on board the aircraft 1, a computer 13 receiving, from the assembly 12, in which it is, here, included, the position indications of the aircraft 1 as well as the position signal 19 target 4.

The computer 13, having in memory the characteristics of the bombs 2 and 3 necessary for the calculation of their trajectories after dropping, such as mass, coefficient Cx of aerodynamics, cyclically runs a trajectory calculation algorithm providing the maximum range of the bombs 2 and 3, taking into account their speed vector and its angle on the horizontal as well as the attitude and altitude of the airplane 1 with respect to the horizontal plane of the target 4.

The bombs 2 and 3 include a braking device, here a parachute, the activation of which is delayed relative to the moment of release. The delay TB1, TB2 of activation of the parachute is adjustable, so that the bombs 2 and 3 have a mixed trajectory formed by a portion of free trajectory, or smooth phase, not intentionally braked, of duration, therefore length, controlled, followed, if ordered, by a portion of the braked trajectory.

The computer 13 is directly connected to each bomb 2, 3 by a data link 14, 15. In this example, provision is made for the connection to be maintained after dropping, so that, to make these connections 14, 15, the computer 13 is associated with two radio transmitters transmitting respectively to two radio receivers placed in the bombs 2, 3. It will be understood that links by unwinding cable could be provided, the influence of braking due to cables being then taken into account for the calculation of the trajectory of the bombs 2, 3.

The computer 13 can also calculate the horizontal range of a bomb 2, 3 under the conditions of position and speed of the airplane 1 indicated, as a function of the duration of travel of the portion of free path.

The bombs 2, 3 are dropped using the process below.

In a first approach phase before launch, and for each of various successive positions of the airplane 1, the target 4 being identified by means of the viewfinder 11, the computer 13 cyclically calculates a portion of the free trajectory 6 of the bombs 2 , 3, corresponding to the maximum horizontal reach P obtainable, taking into account the release conditions.

When the horizontal distance from the target 4 to the airplane 1 becomes equal to the maximum drop range P, the computer 13 supplies the pilot of the airplane 1 with a first firing solution signal.

In a second approach phase, in order to maintain the target 4 on the trajectory of the bomb 2 as the airplane 1 moves, the position of the target 4 is determined as before and the computer 13 fixes the adjustable duration TB1 by calculating an anticipated virtual trajectory of the bomb 2 as during the first approach phase, but by replacing, in the calculation, after crossing the minimum above, the trajectory of maximum range 6 by a mixed trajectory 20 which it controls the travel time TB1 of the free trajectory portion 21 by the minimum of the distance from the target4 so that, for each of the various positions of the aircraft 1 during this second approach phase, the distance from the target 4 to the trajectory 20 of the bomb 2 is equal to this minimum and, before the expiration of said travel time TB1, it transmits to the bomb 2 a travel time signal TB1 of the portion of free trajectory 21. It will be understood that, s 'he was not As planned to maintain data links, such as 14, 15, between the computer 13 and the bombs 2, 3, the journey time signal TB1 should be transmitted before dropping.

In this example, the first fire solution signal does not authorize launch, because there is a additional condition, which is that the trajectory of the bomb 2, 3 makes, upon impact, an angle A, on the horizontal, which reaches a threshold value A0, here 82 degrees. This trajectory can, in practice, be a portion of a free trajectory, like 6, if the corresponding climax is high enough for the trajectory of the bomb 2, 3 to approach the vertical enough, or it can be a mixed trajectory, which requires a lower height of apogee since the trajectory presents a transition bringing it more quickly towards the vertical.

To satisfy this condition on the impact angle A of the trajectories of the bombs 2, 3 at their intersection with the horizontal plane of the target 4, the computer 13 supplies, as explained below, a second signal of the firing solution, authorizing the release, when the impact angle A reaches the value A0. As the aircraft 1 approaches the target 4, here without losing altitude, the length of the free trajectory portion decreases and that of the braked trajectory portion, starting from higher, increases progressively, which causes l increase in impact angle A.

It will be noted that, if the target 4 is masked by a relief, of known horizontal position and height, one can introduce the additional condition that it is guaranteed that the mixed trajectory 20 is aerial to the target 4, this is that is to say has a height of apogee sufficient to ensure an overview of this relief. This can also be the case when the trajectory of the bombs 2, 3 must remain above a volume of airspace in which countermeasures are likely to be applied to the bomb 2, 3.

The computer 13 then compares the mixed trajectory 20 with the coordinates, in horizontal position and altitude, of the relief in question and authorizes a bomb launch 2, 3 only when the mixed trajectory 20 is located above the relief. The latter is also considered as a target which, in this case, must always be avoided and exceeded by the mixed trajectory 20, that is to say that the launch takes place only after passage of the mixed trajectory 20 by the top of the relief, after the distance between the mixed path 20 and the top of the relief has passed a minimum.

The pilot then drops the bomb 2 at an instant T1, at a point 7 of the path 8 of the airplane 1, represented by a dotted line. Here, instead of storing in the bomb 2, before its release, the delay, with respect to the release time T1, of activation of the parachute calculated at the time of the release, the computer 13 continues the calculation of this delay. The bomb 2 follows, for a journey duration equal to the delay TB1 above, a trajectory 20 formed by a portion of free trajectory 21 which will be followed, at an instant T1 + TB1, by a portion of braked trajectory 22. When the corresponding time has elapsed, the computer 13 sends the bomb 2 a brake control signal. This brake control signal, transmitted after launch, which, as indicated, could have been replaced by another brake control signal memorized in the bomb 2 before launch, makes it possible to take into account a movement of the target 4 which would have been unpredictable at launch. It is indeed possible, with the computer 13 to predict by extrapolation the movements of the target 4, but this is only statistical and therefore cannot take into account an avoidance maneuver performed by the target 4 as a function of the threat detected. The order to open the bomb 2 parachute is memorized and controls the opening of the parachute when the time TB1 has elapsed since the release.

The bomb 3 is then dropped at a point 9 of the trajectory 8, at an instant T2, and, as the aircraft 1 has approached the target 4 since the previous release, the computer 13 commands, with a shorter delay TB2 as for the bomb 2 (TB1), the opening of the bomb parachute 3. The bomb 3 follows a trajectory 25 formed by a portion of free trajectory 26 followed by a portion of braked trajectory 27. A trajectory of the bomb 3, for which the duration of travel of the portion of free trajectory would be equal to that (21) of the bomb 2, is represented by a dotted line which exceeds the target4 by a horizontal distance D.

The difference CI Tb of the travel times of the free trajectories of the bombs 2 and 3 is proportional to the duration CI TI = T2 - T1 separating the two drops. However, since the release conditions may have varied from one bomb 2, 3 to another and the bombs 2, 3 being slightly slowed down by the air over their portion of the free path, the following corrective terms are introduced.

The distance D between impacts on the ground 5, assumed to be horizontal, of the bombs 2 and 3 in the absence of correction of the delay in opening the parachute is equal to the difference CI TI between the moments of release multiplied by the horizontal speed 1 Vi the point of intersection of the trajectory of one of the bombs 2, 3 with the ground 5, calculated in a known manner by the computer 13. The range correction on the bomb 3, that is to say the value of the distance D between impacts, is equal to the horizontal speed 1 Vb of the bomb 3 at the end of the free trajectory portion 26, shorter in this example than the free trajectory portion 21, multiplied by the duration of the anticipation of the signal of corresponding bomb brake control 3.

This anticipation is equal to the delay TB1 of the bomb brake control signal 2, with respect to its release time T1, minus the delay TB2, here reduced, of the bomb brake control signal 3 with respect to its time T2 release. So we have :

It will be noted that the horizontal speed 1 Vi of the point of impact on the ground 5 is a phase speed, that is to say corresponds to the displacement of a path virtual roof which is the end of the braked trajectory portion. It can therefore take values independent of the horizontal speed of the airplane 1, in particular larger if the airplane 1 carries out a resource suddenly increasing the range of the bombs 2, 3, so that the precise determination of CI TI then has a great importance. A follow-up, observation, of the free trajectory portion of the bomb 2, 3 and a braking command signal transmitted after dropping, taking into account the observed trajectory of the bomb 2, 3, make it possible to further improve the precision of the bombing.

Conversely, the airplane 1 can maneuver so that the horizontal phase speed 1 Vi is low between the drops, that is to say that the quasi-parabolas of the two free paths pass substantially through the target 4, which, in this particular case, makes the bombardment accuracy not very dependent on the difference between the delays of the brake control signals.

It will also be noted that, unlike this example, the retardation of the braking of the bomb 3 could be greater than that of the bomb 2 if the airplane 1, although approaching the target 4, carried out a maneuver reducing the range P .

In the case where, unlike the group shooting above, it would be necessary to distribute homogeneously, in concentration shooting, the impact points over a large area of target 4, it will be understood that the above method is applicable by providing , unlike braking delay between bombs, a offset correction, positive or negative, calculated according to the same principle and shifting the impact points on the ground by the desired distance 5. Bombs are then assigned several points respectively impact on target 4 and a duration of free path portion TB1, TB2 is transmitted to each bomb as a function of the position of the corresponding point of impact.

In this example, the computer 13 provides a launch prohibition signal when the duration of travel of the portion of free path is reduced to a determined threshold value preventing any range correction. This value, if it is other than zero, allows the aircraft to avoid parachutes. It may depend on the flight conditions of the aircraft 1, that is to say on the speed at which it will deviate, after launching, from the trajectory of the bombs 2,3.

It will be understood that a length of portion of free path as well as the duration of corresponding journey can be adjusted.

Claims (6)

1. Method of launching and controlling on a target (4), from a mobile vehicle (1), at least one projectile (2, 3) not vertically guided, with a trajectory (25) mixed, with a portion free, of adjustable duration, then with a braked portion, in which, in a first approach phase before launch, and for each of various successive positions of the vehicle (1), 1- the position of the target (4) is determined in a three-dimensional coordinate system linked to the vehicle (1), 2- the said adjustable duration is fixed at a maximum value, the speed of the vehicle (1) is calculated, taking into account the anticipated virtual trajectory (6) of the projectile (2, 3), of maximum range, 3- the distance from the target (4) to said virtual trajectory (6) is calculated and - the projectile (2, 3) is launched after said distance has crossed a minimum,
characterized by the fact that:
in a second approach phase, the position of the target (4) is determined, said adjustable duration is fixed (TB1, TB2), an anticipated virtual trajectory of the projectile (2, 3) is calculated as in the first phase d approach, but by replacing, in the calculation, after crossing said minimum, the trajectory of maximum range (6) by a mixed trajectory (25) for which the travel time (TB1, TB2) of the free trajectory portion ( 26) by the minimum of said distance from the target (4) so that, for each of the various positions of the vehicle (1) during this second approach phase, the distance from the target (4) to the trajectory of the projectile ( 25) is equal to this minimum and, before the expiration of said travel time (TB1, TB2), a transmission time signal of portion of free path portion (26) is transmitted to the projectile (2, 3). 2. Method according to claim 1, in which the impact angle (A) on the ground of the trajectory of the projectile (2, 3) is calculated during the first phase (6) as well as during the second phase of approach (25) and the launch is prohibited until a projectile trajectory (25) has, with the horizontal, an impact angle (A) greater than a determined value (AO). 3. Method according to one of claims 1 and 2, wherein, several projectiles (2, 3) are launched by assigning them respectively several points of impact (4) on the target and is transmitted to each projectile (2, 3 ) a duration of the free trajectory portion (TB1, TB2) as a function of the position of the corresponding point of impact (4). 4. Method according to one of claims 1 to 3, in which said journey time is compared (TB1, TB2) with a threshold value and a signal for prohibiting the launching of the projectile (2, 3) is generated when it is less than said value of threshold. 5. A method of guidance after launch according to the method of one of claims 1 to 4, in which, to prevent the passage of the projectile (2, 3) in a space to be avoided, - we determine the position of space, - the distance between a vertex of space and the mixed trajectory (25) is calculated and - the projectile (2, 3) is only launched after said distance has passed a minimum. 6. Guidance method after launch according to the method of one of claims 1 to 5, wherein, the projectile (2, 3) comprising a data receiver arranged to cooperate, after launch, with a transmitter of the vehicle (1 ), after launching, the calculation of a virtual trajectory (6; 25) of the projectile (2, 3) coinciding with its real trajectory is continued and the corresponding signals for the duration of the course of travel are transmitted to the projectile (2, 3) the free trajectory portion (26).

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