EP1558890B1 - Plasma discharge piloting of a projectile - Google Patents

Description

The present invention relates in particular to the field of arrangements for guiding or piloting self-propelled or non-propelled projectiles or missiles and relates to a method, as well as an associated device, for controlling a projectile, such as, for example, a shell , a bullet or a missile.

The piloting of a flying machine in the atmosphere may in particular be carried out by the deployment of airfoils or by the operation of a pyrotechnic device, for example.

The main disadvantage of the bearing surfaces is at the level of their deployment which requires significant effort, especially as the speed of the machine is too, and a resistance of the device to very high pressures encountered at speeds supersonic. In addition, this type of control requires a long reaction time which can be a major disadvantage if the machine is stabilized by rotation.

The main disadvantage of flying a flying machine by the operation of a pyrotechnic device is that it can operate only once.

The document US 3151259 A discloses a method and apparatus for deflecting and piloting a hypervelocity projectile according to the preambles of claims 1, 3 and 4.

The aim of the invention is to overcome these disadvantages by proposing a method of piloting a hypervelocity projectile, that is to say one whose speed is greater than the speed of sound, having no moving part and which can be implemented as many times as necessary.

The solution provided is a method of piloting a hypervelocity projectile, such as, for example, a shell, a bullet or a missile, having a nose, generally cone-shaped, having a more or less pointed end characterized by it consists in performing a plasma discharge near said end and on a limited sector of the outer surface of the nose.

According to one particular characteristic, the invention relates to a method for deflecting a hypervelocity projectile along a Y direction, such as, for example, a shell, a bullet or a missile, having a nose, generally cone-shaped, having a longer end. or less pointed, characterized in that it consists in carrying out a plasma discharge near said end, on a limited sector of the outer surface of the nose and on the Y direction side.

The invention also relates to a device for controlling a hypervelocity projectile, such as, for example, a shell, a bullet or a missile, having a nose, generally cone-shaped, having a more or less pointed end and characterized in that it comprises means able to emit a plasma discharge near said end and on a limited area of the outer surface of the nose.

According to a particular characteristic, the means capable of emitting a plasma discharge comprise a triggered spark gap, two electrodes and a high voltage generator.

According to another characteristic, said means comprise at least one pair of electrodes. Indeed, said means comprise at least one pair of electrodes if the projectile is rotating or several pairs of electrodes if it is not rotating.

• la figure 1 montre un schéma des ondes de choc engendrées par un projectile supersonique,
• La figure 2 montre le résultat d'une simulation numérique du même engin évoluant dans les mêmes conditions de vol supersonique que précédemment auquel est appliquée une décharge plasma,
• La figure 3 montre la dissymétrie de la distribution de la masse volumique de l'air environnant sur la moitié de la surface du projectile et dans le plan de symétrie de l'écoulement pour l'exemple choisi.
• la figure 4 présente un schéma d'un dispositif selon un mode de réalisation de l'invention,
• la figure 5 montre un exemple d'implantation de quatre couples d'électrodes disposées à π/2 Radians les uns des autres.

Other advantages and characteristics will become apparent in the description of particular embodiments of the invention with reference to the appended figures among which:

• FIG. 1 shows a diagram of the shock waves generated by a supersonic projectile,
• FIG. 2 shows the result of a numerical simulation of the same machine operating under the same supersonic flight conditions as previously, to which a plasma discharge is applied,
• Figure 3 shows the dissymmetry of the density distribution of the surrounding air on half of the projectile surface and in the plane of symmetry of the flow for the chosen example.
• FIG. 4 is a diagram of a device according to one embodiment of the invention,
• FIG. 5 shows an example of implantation of four pairs of electrodes arranged at π / 2 Radians of each other.

In the case of a hypervelocity machine, a shock wave occurs upstream of its nose. When the machine is flying on a straight path, the pressures distributed over its surface are balanced and the shock wave has symmetries depending on the shape of the vehicle. In the case of a projectile consisting of a conical nose, the wave is attached to the tip of the cone and conical.

Figure 1 shows the result of a numerical simulation of a machine flying at a supersonic speed in the direction of the arrow. It shows integrally a machine 1 and half of two other surfaces 2 and 3. The machine comprises a front portion 4 conical and a rear portion 5 cylindrical. Said surfaces 2 and 3 characterize a constant pressure in the flow. The surface 2 attached to the tip of the machine represents the surface of the conical shock wave while the surface 3 attached to the discontinuity of the surface of the machine (cone-cylinder junction) characterizes a wave of relaxation.

The invention applied to such a projectile consists in unbalancing the flow around the nose of the machine by producing a plasma discharge towards the end of the nose as close as possible to the tip, in order to make an incidence of the craft . This plasma discharge carried out on a limited angular sector modifies the boundary layer which surrounds the surface of the machine. The objective is therefore to produce a discharge such that the imbalance of the thermodynamic quantities is large enough to cause the deviation of the vehicle relative to its rectilinear trajectory.

The absence of moving parts and the repeatability of landfills are the main advantages of this technique. Indeed, the control of the machine on its trajectory can be achieved by repetitive discharges actuated on demand according to the desired trajectory.

Figure 2 shows the result of a numerical simulation of the same machine operating under the same supersonic flight conditions as previously, to which a plasma discharge near the tip is applied. Each of the two surfaces 7, 3 shown thereon, characterizes a constant pressure in the flow.

It can be seen that at the tip of the machine 1, the shock wave 7 is deflected under the action of the plasma discharge 6.

Figure 3 shows the dissymmetry of the density distribution of the surrounding air on half of the projectile surface and in the plane of symmetry of the flow for the chosen example. This density is substantially constant and equal to 1 kg / m ³ between the points A and B situated opposite the plasma discharge 6 and downstream, with respect to the Z direction of the projectile, from the plasma discharge (zone C ), while it is very low (of the order of 2,710-2kg / m ³ ) at the skin E of the projectile upstream of the plasma discharge 6. By cons it is maximum, of the order of 3kg / m ³ at point D at the plasma discharge 6.

Figure 4 shows a diagram of a part of a device according to one embodiment of the invention. This part has a cone-shaped nose 4 of a hypervelocity projectile. Near the end of the nose is shown a plasma discharge 6.

To deflect the projectile in a direction Y perpendicular thereto, a plasma discharge 6 is made on a limited sector 8 of the outer surface of the nose and on the Y direction side.

Figure 5 shows an example of implantation of four pairs of electrodes arranged n / 2 Radians from each other and near the end of the projectile nose. These electrodes are connected to a circuit capable of generating an energy between the electrodes composing the said couples which is sufficient for priming the plasma. This circuit comprises a control device 12, a voltage multiplier tripping trigger 11.

Thus, the control device 12 controls via the multiplier tripping trigger 11 on the one hand the generation of the adequate voltage difference and on the other hand the delivery of the voltage generated to the (x) pair (s) corresponding to the direction of desired deviation.

The drag of the machine, the force and the moment of piloting can be determined by calculation. Even in the case where efforts are low, this device is interesting because by acting near the tip of the machine, a small dissymmetry of the flow destabilizes the projectile and allows its piloting. The use of the same device, or of another device according to the invention placed at another place on the projectile, can be used to stabilize the projectile again on its trajectory.

Moreover, this device can be associated with means allowing its control, such as, for example, a GPS system, a self-steering type system, a remote control system, or any other system for knowing the roll position of the machine.

By way of example, for a projectile of 20 mm caliber flying at ground level under normal conditions at a speed corresponding to a Mach number of 3.2 and whose front consists of a cone of 20 ° C angle at the top and a cylindrical portion having no bearing surface, a plasma discharge, whose temperature is about 15000K, is carried out on a surface of 9 mm ² near the tip of the projectile which requires a momentum corresponding to a mass flow rate of an explosive substance of about 10 ^-4 kg / sec corresponding to a power of about 3 kVA. The duration of the discharge between 2 and 4 ms corresponding to an electrical energy of the order of ten Joules.

The intensity of the discharge can be modulated by acting on the thermodynamic parameters such as the temperature in the discharge and the associated momentum.

The plasma is generated by high voltage discharge (s). This (these) discharge (s) is (are) obtained by a voltage multiplier trigger, which, from an electrical or low-level optical signal, and delivers (s) sufficient energy to the priming of the plasma. The design optimizes the stored electrical energy prior to tripping and the voltage pulse appropriate to the conditions of the plasma discharge.

The effect on the aerodynamic effects is interesting. The aerodynamic effects are first evaluated by numerical simulation in the case of the unmanned projectile moving on a straight trajectory at zero incidence. The aerodynamic coefficients are calculated only for the front body of the projectile, the wake is therefore not taken into account:

The drag coefficient is Cx = 0.1157. The coefficient of lift Cz and the moment coefficient Cm calculated at the tip of the projectile are obviously zero.

The aerodynamic coefficients are now determined for the projectile evolving on the straight trajectory at zero incidence and piloted by a plasma discharge modeled under the conditions previously stated:

The drag coefficient is Cx = 0.0949. The lift coefficient is Cz = 0.0268 which corresponds to a force of 6 N oriented in the direction of action of the discharge. The moment coefficient calculated at the point of the projectile is worth Cm = - 0.0356 which corresponds to a moment of 0.1609 mN oriented to accompany the effects of the lift force.

• Une réduction de la traînée du projectile lors de la décharge plasma d'environ 18 % ce qui est très important ;
• que la force de pilotage agit dans la direction de la décharge ;
• que le moment de tangage contribue d'une façon bénéfique à la force de pilotage pour rendre le projectile manoeuvrant.

The analysis of the results of this simulation shows:

• A reduction of the projectile drag during the plasma discharge of about 18% which is very important;
• that the piloting force acts in the direction of discharge;
• that the pitching moment contributes in a beneficial way to the piloting force to make the projectile maneuvering.

Of course, many modifications can be made without departing from the scope of the invention, as described in claims 1 to 6. Thus, the shape of the nose can be any.

Claims (6)

1. Method for deflecting a hyper-fast projectile (1), such as, for example, a shell, a bullet or a missile, according to a direction which is perpendicular to its longitudinal axis, this projectile (1) comprising a nose (4) which is generally in the shape of a cone, and has a more or less pointed end, characterised in that it consists of carrying out a plasma discharge (6) on a limited section (8) of the outer surface of the nose (4) and on the said perpendicular direction side.
2. Method according to claim 1, characterised in that it consists of carrying out a plasma discharge (6) in the vicinity of the said end, on a limited section (8) of the outer surface of the nose (4) and on the said perpendicular direction side.
3. Method for piloting a hyper-fast projectile (1), such as, for example, a shell, a bullet or a missile, comprising a nose (4) which is generally in the shape of a cone, and has a more or less pointed end, and is characterised in that it consists of implementing a method according to claim 1 for each modification of the trajectory of the projectile (1).
4. Device for deflecting a hyper-fast projectile (1), such as, for example, a shell, a bullet or a missile, according to a direction which is perpendicular to its longitudinal axis and comprising a nose (4) which is generally in the shape of a cone, and has a more or less pointed end, and is characterised in that it comprises means which can emit a plasma discharge (6) in the vicinity of the said end, on a limited section (8) of the outer surface of the nose (4) and on the projectile (1) side which is situated on the side in the direction of the deflection.
5. Device according to claim 4, characterised in that the means which can emit a plasma discharge (6) comprise a triggered discharger, two electrodes and a high-voltage generator.
6. Device according to claim 4 or claim 5, characterised in that the said means comprise at least one pair of electrodes.

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