PROJECTIL WITH DENSE BAY DRIVE

Description

[0001] The technical field of the invention is that of propelled projectiles and in particular propelled artillery projectiles.

[0002] There are many known solutions for increasing the range of an artillery projectile. One known solution is to equip the rear part of the projectile with a hollow base or a rear gas generating block (better known by the Anglo-Saxon name Base-Bleed).

[0003] These solutions make it possible to reduce the drag on the projectile base, which is generated by the so-called "dead water" zone behind the base, a zone which is depressed relative to the undisturbed upstream flow.

[0004] The increase in range they provide is interesting in percentage but remains limited in absolute value, we can thus go from 30km of range to around 40km thanks to a Base-Bleed.

[0005] To increase the range of artillery projectiles, it has already been proposed to equip these projectiles with propellants. Thus, patents FR2479905 and FR2522134 describe a shell comprising at its warhead a small powder propellant which is ignited during the initial phase of the trajectory to prolong to a certain extent the impulse resulting from the cannon shot.

[0006] It has also been proposed, for example in patents RU2513326 and US5853143, to equip an artillery projectile with a ramjet-type propellant.

[0007] Such a solution, compared to a self-propelled powder projectile, makes it possible to reduce the mass of the on-board propellant material (the oxidant or comburant then being made up of the oxygen in the air).

[0008] This solution is, however, generally implemented for projectiles with direct firing and for which the aim is to reduce the flight time. See for example patent FR2629584 which describes an anti-helicopter projectile.

[0009] Propelled projectiles have a high ballistic dispersion which also increases significantly with range.

[0010] It therefore becomes essential, if we wish to increase the range of the projectile beyond the classic values ​​of 40 or 42 km and meet the needs of future artillery, and in particular to obtain metric precision associated with a long range (or even independent of the range), to equip the projectile with means to correct its trajectory.

[0011] Known trajectory correction means include control surfaces arranged at the level of the projectile nose cone (usually called "Canards Actuating System" or CAS). These means are generally associated with shells or projectiles that are not propelled by a ramjet, such as those described by patents EP1297292, FR2768809, EP2767794, or FR3054030.

[0012] Indeed, the installation of trajectory correction control surfaces is not very compatible with the geometry of a ramjet projectile and the aerodynamics of the axial air intake which must not present any obstacle or aerodynamic singularity to ensure the initiation of combustion and its nominal operation in the cruise phase.

[0013] Patent DE3321945 describes a projectile fired from a cannon and comprising a payload mounted to slide relative to a propellant. As it leaves the weapon barrel, the acceleration decreases and the payload is pushed out of the propellant barrel by the pressure of the firing gases. The movement of the payload is sufficient to open the air passage into an annular chamber, which ignites the ramjet.

[0014] This projectile has no means of correcting its trajectory. Furthermore, there is no question of closing the air inlet orifice on the trajectory to cut off the ramjet.

[0015] Patent GB2090384 discloses a projectile as defined in the preamble of claim 1.

[0016] The aim of the invention is to propose a ramjet-powered projectile which is nevertheless controllable in order to give it precision in reaching its target regardless of the range, and therefore the flight time.

[0017] The invention is more particularly described in its application to an artillery shell.

[0018] Thus, the subject of the invention is a ramjet-powered projectile, a projectile comprising an external body and a deployable tail, a projectile comprising inside the body a chamber in which is housed an ablatable annular semi-propellant block as well as an envelope containing a military charge, the external body comprising an air inlet to allow air to enter the chamber, the body also comprising a rear opening on which a nozzle is positioned, a projectile characterized in that it comprises a pilot module arranged axially and which extends through the air inlet, the pilot module being able to be moved axially by a motor means, during the flight of the projectile and at a defined instant on the trajectory, called the extinction instant, from a rear position in which it does not block the air inlet, to a front position in which it blocks the air inlet,the pilot module containing at least two canard control surfaces which can be deployed outside the projectile after blocking the air inlet.,

[0019] The control module may contain a calculation means incorporating control algorithms, the calculation means ensuring control of the movement of the control module at the instant of extinction.

[0020] More specifically, the propelled projectile will constitute an artillery projectile intended to be fired by a cannon, a projectile whose external body will carry a sliding belt.

[0021] According to a particular embodiment, the control module may be in its forward position before firing, the control module moving back by inertia during the firing of the gun so as to occupy its rear position in which it will rest against the military charge envelope.

[0022] Advantageously, the projectile may include a locking means ensuring the immobilization of the pilot module in the rear position.

[0023] The motor means may comprise a means for storing elastic potential energy, this means being activated by the recoil of the control module from its front part to its rear part, the locking means being released at the extinction instant defined on the trajectory.

[0024] According to another embodiment, the control module is in its forward position before firing, the control module being able to be moved by the motor means, after firing and at a time, called ignition, defined on trajectory, so as to come and occupy its rear position.

[0025] The motor unit will thus be able to move, progressively or incrementally, at different successive moments defined on the trajectory, the control module from its front position to its rear position.

[0026] According to a variant, the motor means may move the pilot module to its rear position at the end of the piloted phase so as to clear the air intake and thus accelerate the projectile during a terminal phase of its trajectory.

[0027] The control module may include a rear skirt that can slide on an outer wall of the casing when the control module is moved so as to improve the continuity of the air flow during operation of the ramjet and for all longitudinal positions of the control module.

[0028] Advantageously, the projectile will have a rear base closing the nozzle during firing, a base ensuring the maintenance of the rear tail and which is ejected at the exit of the barrel.

[0029] The invention will be better understood on reading the following description of particular embodiments, a description made with reference to the appended drawings and in which: [ Fig. 1 ] is a schematic and longitudinal sectional view of a projectile propelled according to an embodiment of the invention; [ Fig. 2 ] is a curve showing the different phases of flight of the projectile according to this embodiment; [ Fig. 3a ] is a partial and schematic detail view which shows an embodiment of a motor means, the projectile being in the storage phase; [ Fig. 3b ] is a partial and schematic detail view which shows the embodiment of a motor means of the Figure 3a , the projectile being in the propelled phase; [ Fig. 4a ] is a longitudinal sectional view of the projectile according to this embodiment during a phase of its trajectory, the projectile being at the exit of the weapon barrel; [ Fig. 4b ] is a longitudinal sectional view of the projectile according to this embodiment during a phase of its trajectory, the projectile being during its propelled phase; [ Fig. 4c ] is a longitudinal sectional view of the projectile according to this embodiment during a phase of its trajectory, the projectile being during its guided phase; [ Fig. 5 ] is a partial detailed view of an alternative embodiment of a motor means; [ Fig. 6 ] represents curves showing the influence of altitude on the air flow of a ramjet; [ Fig. 7 ] is a curve showing the different flight phases of a projectile using this variant of the motor system.

[0030] Referring to the figure 1 , a ramjet-powered projectile 1 according to one embodiment of the invention comprises a body 2 and a deployable tail 3 which is kept folded, during storage phases and during the ballistic journey in the tube, by a rear thrust base 4. The body 2 carries a sliding belt 5 which ensures gas tightness inside the weapon tube and which also makes it possible to limit by sliding the rotation speed which can be communicated to the projectile by the rifling of the weapon tube (the sliding rate is of the order of 90% minimum). Indeed, an artillery tube is generally rifled to ensure the rotation of the projectiles.

[0031] Base 4 will be ejected at the exit of the weapon tube and tail 3 will deploy to ensure the aerostabilization of the projectile on trajectory.

[0032] Aerostabilization is necessary due to the projectile's architecture (low longitudinal moment of inertia which does not allow gyroscopic stability criteria to be met) and the reduction in roll speed on trajectory when the projectile is in the piloted phase due to the high roll damping coefficient (Clp) of the tail. Aerostabilization is finally necessary to make subsequent piloting possible via control surfaces. The control of control surface deflections to the projectile's roll position is in fact limited in roll speed by the bandwidth of the computer and actuators.

[0033] Since the projectile must be aerostabilized, the presence of a slip belt is therefore necessary to limit the mechanical constraints which increase as the square of the rotation speed and to avoid Magnus effects which can dynamically destabilize the projectile.

[0034] The rotation speed of the shell leaving the tube is of the order of some 10 revolutions per second.

[0035] Such slip belts are well known to those skilled in the art in the field of artillery projectiles. Reference may be made to patents WO03001141, EP1693646 and EP1386120 which describe such belts.

[0036] Deploying tail units are also well known to those skilled in the art (see patent EP0905473).

[0037] The projectile 1 has inside the body 2 a chamber 6 in which is housed an annular block 7 of a fuel consisting of an ablatable semi-propellant.

[0038] Room 6 also receives an envelope 8 which contains a military charge 9, for example an explosive charge.

[0039] The casing 8 is connected to the body 2 by radial connecting arms 10 which are profiled and which are regularly distributed angularly. There are here three groups of three arms 10. The three arms of each group are angularly spaced from each other by 120°.

[0040] The body 2 has an annular air inlet 11 which is closed during storage and firing phases by a control module 12 (this advanced position - figure 1 - is its reference position).

[0041] The air inlet 11 is intended to allow air to enter the chamber 6 when the projectile is in the propelled phase. The body 2 also has a rear opening 13 on which a nozzle 14 is positioned.

[0042] The base 4, whose primary function is to accelerate the projectile by transmitting the thrust of the firing gases to it, also makes it possible to close the nozzle 14 during firing, thus isolating the fuel block 7 of the ramjet from the hot gases of the propellant powder charge which push the projectile out of the weapon barrel.

[0043] The piloting module 12 contains at least two canard control surfaces 15 (arranged in the same plane and materializing a piloting plane) as well as their deployment mechanism (not shown). Such deployable control surface devices are well known and described in particular by patents FR2949848, FR2846080, FR2864613 and FR2891618.

[0044] It is thus easy to integrate canard rudders and their deployment and orientation mechanism into a pilot module with a diameter of around 60 to 90 millimeters which is incorporated into a 155 millimeter caliber projectile.

[0045] The piloting module 12 contains sensors (inertial, magnetic, etc.) and also a calculation means 16 incorporating piloting algorithms allowing the control of the steering of the control surfaces to direct the projectile towards a target whose coordinates will have been entered into the calculation means 16 before firing by a programming means not shown, for example by a connection interface or by contactless programming through an inductive loop connected to the calculation means 16.

[0046] The control module 12 is therefore a subassembly of the projectile which incorporates means for correcting the trajectory of the projectile (deployable control surfaces 15). This control module may also contain the means associated with the control surfaces and enabling their control (calculation means 16). The calculation means could be positioned elsewhere on the projectile, for example in the casing 8, but it is more advantageous to house them in the control module 12 which is mobile relative to the casing 8.

[0047] The control module 12 is arranged axially and it extends through the air inlet 11 and has in particular a tip 12a extending in front of the air inlet 11. The control module 12 can be moved axially along the axis 26 of the projectile by a motor means, during the flight of the projectile and at a desired instant on the trajectory (i.e. a defined instant, called the extinction instant). The movement will be made from a rear position, in which the control module 12 is supported against the casing 8 of the military charge 9, to a front position in which it closes the air inlet 11, thus stopping the combustion of the fuel block 7 and stopping the ramjet. This device therefore makes it possible to control the operating time of the ramjet, which is one of the advantages of the invention.

[0048] The control module 12 comprises a peripheral shoulder 12b which comes to bear against an annular stop surface carried by the body 2 when this module 12 is in the closed position shown in figure 1 .

[0049] Of course, the external profile of the control module 12 is defined so as to promote the flow of air and its entry into the chamber 6 when the control module 12 is in its rear position and the air inlet 11 is clear. This profile is well known to those skilled in the art, and wind tunnel tests are conventionally used to optimize this profile which performs the important function of compressing and heating the flow upstream of the combustion chamber 6.

[0050] The same applies to the external profile of the casing 8 associated with that of the nozzle 14, which transforms into kinetic energy the heat energy created in the combustion chamber 6 and at the origin of the thrust, and in particular that of its rear end 8a which is rounded opposite the neck 14a of the nozzle 14.

[0051] The calculation means 16 makes it possible to control the movement of the control module 12 at a desired instant on the trajectory (i.e. at a defined instant) and it also makes it possible to control the deployment of the fins 15 as will be described later. It is clear that the term “desired instant on the trajectory” means an instant which is predefined by the design of the projectile or which has been defined and programmed before firing. This instant is managed by the calculation means 16 of the control module 12.

[0052] The switching-off time is thus the time at which the control means 12 is moved from its rear position to its front position in which it closes the air inlet 11. The movement is carried out by sliding the control module 12, for example, on one or more columns 17 secured to the casing 8 and which penetrate into the control module 12 when the latter moves back. Alternatively, a single column or central axis may be used. The motor means may consist of a small motor incorporated in the control module 12 and meshing, for example, with a rack carried by one of the columns 17.

[0053] More simply, when there are only two positions necessary for the control module (rear position and front position or air intake closure), and as shown in the diagram figures 3a And 3b, at least one of the columns 17 (or all the columns) may be equipped with a traction spring 18 which will be fixed on the one hand to a collar 19 of the column 17 and on the other hand to the wall of the control module 12. This traction spring 18 will constitute the motor means which is here a means of storing elastic potential energy.

[0054] There figure 3a shows the assembly before firing. The spring 18 is at rest, in the unstretched state. It can be seen that the column 17 passes through a transverse wall 20 secured to the module 12 and which ensures its guidance. It can also be seen that the wall 20 carries an electromagnetic lock 21 (shown very schematically) which is intended to engage in a groove 22 of the column 17. This electromagnetic lock 21 constitutes a locking means which will ensure the immobilization of the control module 12 in the rear position.

[0055] At the time of shooting ( figure 3b ), the control module 12 moves back due to its inertia. A shearable retaining pin (not shown) may be provided between the body 2 of the projectile and the control module 12 to secure the assembly in the storage position. This recoil movement has the effect of tensioning the tension spring 18 (storage of elastic potential energy). The control module 12 comes to bear against the casing 8 of the military charge 9.

[0056] The groove 22 is positioned opposite the electromagnetic lock 21 which ensures the locking of the column 17. In a conventional manner, the electromagnetic lock 21 will comprise a spring pushing a locking finger into the groove 22. No energy is therefore necessary for locking.

[0057] At the extinction instant defined on the trajectory, the calculation means 16 will send a pulse to the electromagnetic lock 21 via a control wire 23, causing the latter to release. The spring 18 then ensures the return of the module 12 to its front position.

[0058] As seen on the figures 3a And 3b , the column 17 may be tubular to allow a wire 24 to pass through, enabling the firing of the military charge 9 to be controlled by means of a detonator 25.

[0059] Of course, these drawings are very schematic. In particular, the method of fixing the columns 17 to the casing 8 is not shown, nor is the method of fixing the detonator 25 or the routing of this wire 24 through the wall of the casing 8. The person skilled in the art is familiar with the various technologies enabling these different functions to be carried out and which are robust in a cannon firing environment (high accelerations, large temperature variation range).

[0060] As a variant, it would be possible to implement one or more compression springs. Other types of locking means could also be defined.

[0061] There figure 2 is a curve showing the different flight phases of the projectile 1 according to the invention.

[0062] The abscissa axis corresponds to the range R of the projectile and the ordinate axis to the altitude H of the projectile.

[0063] For a shot from the origin point O, the projectile goes through several phases.

[0064] When firing the weapon, the thrust base 4 is in place, it keeps the tail unit 3 in the folded position and protects it, as well as the fuel block 7 ( figure 1 ).

[0065] The acceleration of the shot has the effect of making the control module 12 move back, which locks against the casing 8 ( figures 3b et 4a ).

[0066] At the exit of the weapon barrel, the base 4 is ejected (for example by an ejection charge as described by patent FR2768809 or by a force generated by a pressure differential, or even by the effect of the residual rotation communicated by the barrel.

[0067] The ejection of the base 4 at the tube outlet allows the deployment of the fins 3a of the empennage 3 ( figure 4a ) which aerostabilizes the projectile 1 throughout the trajectory by ensuring a residual and maintained roll speed of a few revolutions per second. This roll speed is obtained thanks to an angular setting of the fins 3a relative to the axis 26 of the projectile or by a bevel made on the leading edge or on the trailing edge of each fin 3a. This residual rotation is necessary to pilot the projectile 1 over 360° and essential in the case of piloting by a single plane of control surfaces 15.

[0068] The exit from the weapon tube is at a minimum speed of around 700 m / s, or around Mach 2, which corresponds, from the artillery point of view, to a choice of propellant charges ensuring a shot in "zone 4". There is no upper speed limit to allow the initiation of a ramjet, the only limit of this type of propellant is the speed which is compatible with subsonic combustion inside the projectile, or a projectile speed of around Mach 5 (1700 m / s).

[0069] Such a speed (Mach 2) allows the initiation of the ramjet formed by the general architecture of the projectile 1, once the pilot module 12 is positioned at the rear and the annular air inlet 11 is released.

[0070] This ignition speed is optimal for ignition and operation of the ramjet. The air flow entering chamber 6 through air inlet 11 is compressed, it heats up and spontaneously initiates annular fuel block 7 and is accelerated in nozzle 14, then evacuated.

[0071] The fuel block 7, which is a semi-propellant, lines the walls of the combustion chamber 6 and reacts spontaneously (self-ignition) with the flow from the annular air inlet 11. This air has been compressed and heated following its slowing down by the profile of the air inlet 11, which acts as a static compressor and leads to the priming of the ramjet.

[0072] The combustion of the semi-propellant produces hot gases ejected into the nozzle 14. All of the gases are converted into effective thrust and greatly accelerate the projectile 1. The speed obtained is between Mach 2 and Mach 5 (from 700m / s to 1700m / s) and a maximum altitude of around 25,000 m can be obtained in about one minute.

[0073] The duration of the propelled phase can vary depending on the architecture of the ramjet (section of the air inlet 11, mass of fuel, ejected mass flow rate, etc.) and the firing conditions and can range from a few seconds to a few tens of seconds (1 minute maximum, the limit being set by the altitude).

[0074] This propelled phase is marked by the arrow P on the figure 2 . Projectile 1 is in the configuration of the figure 4b This figure shows the partially consumed fuel block 7.

[0075] Projectile 1 reaches apogee A of the trajectory (H=25 km) after about 50 kilometers ( figure 2 ).

[0076] At this stage (which corresponds to the instant of extinction) the calculation means 16 commands the release of the motor means which causes the return of the control module 12 to its front position ( figure 4c ) in which it closes the annular air inlet 11. The calculation means 16 also causes the deployment of the canard control surfaces 15, after closing the air inlet 11.

[0077] The canard control surface deployment mechanism is a conventional mechanism that does not need to be described in detail. For example, reference may be made to patents FR2949848, FR2864613, FR2846079, FR2846080, WO2012090202 and WO2007133247, which describe such deployment mechanisms.

[0078] The deployment time (or extinction time) is programmed before firing and depends on the conditions of the firing in question. It is clear that, whatever the time at which the forward movement of the control module 12 is triggered, the closure of the annular air inlet 11 will cause the fuel block 7 to be extinguished due to lack of oxygen and the propulsion to stop.

[0079] It is therefore possible, depending on operational needs, to cause the ramjet thrust to stop before apogee A and to allow the projectile to continue its ballistic trajectory. We have delimited on the figure 2 by vertical dotted lines the zone Z in which the ramjet shutdown can be commanded, therefore in which the extinction time can be defined.

[0080] This zone corresponds to operating times between a few seconds and one minute (maximum). Propulsion efficiency is optimal at the start of the trajectory and in all cases before apogee A, which corresponds to maximum ranges for the propelled phase P of between 5 and 50 km.

[0081] Once the canard rudders 15 are deployed, the projectile is in its guided phase G ( figure 2 ) the calculation means 16 will control the piloting of the projectile in the direction of the target T whose coordinates were entered into memory before firing. The calculation means 16 is coupled to a means of positioning the projectile which may include a GPS and / or Galileo type receiver and / or an inertial unit.

[0082] In a conventional manner and which does not need to be described, to carry out the piloting, the deployed control surfaces are pivoted by one or more motors which are controlled by the calculation module 16.

[0083] The control module 12 can also be equipped with infrared target sensors (not shown) located at the level of the warhead of the module 12, sensors used for the final phase of the attack and allowing metric precision to be obtained.

[0084] Different guidance methods are described, for example in patents FR2872928, EP1480000, FR2847033, EP2009387 or EP1840692.

[0085] Due to the thrust obtained in the P-powered phase by the ramjet, it becomes possible to reach ranges greater than 80 km using conventional artillery used in normal firing conditions and at least in charge 4 (which limits tube wear and increases the tube's potential use) and with a classic shell profile while having better firing accuracy (in reference to a classic 40 km firing with Base-Bleed) thanks to the guidance means.

[0086] The precision can be metric or decametric depending on the guidance techniques implemented and the on-board sensors, and it is independent of the flight time, therefore of the range and of the weather conditions.

[0087] The whole point of the invention is to provide these operational advantages using conventional artillery and existing firing charges for artillery systems.

[0088] There figure 5 schematically shows another embodiment of a motor means.

[0089] According to this mode, the motor means is constituted by an electric motor 27 which is equipped with a toothed wheel 28. The latter meshes with a threaded nut 29 which is engaged on a central axis 30 carrying a thread 31. The electric motor 27 is secured to the control module 12 by a flange 33. It is connected to the calculation means 16 by a wired connection 34. Its operation is controlled by the calculation means 16 which will incorporate algorithms ensuring the rotation of the motor 27 in one direction or the other depending on the firing chronometry (therefore the location of the projectile 1 on its trajectory).

[0090] The central axis 30 is integral with the casing 8 and is coaxial with the axis 26 of the projectile 1. The central axis 30 passes through a bottom wall 12c of the control module 12 through a hole 12d which has a diameter greater than that of the axis 30 and does not hinder the rotation of the central axis 30.

[0091] Three columns 17, regularly distributed angularly around the axis 26 (only two are visible in this cross-section), are integral with the casing 8 and slidably fitted into holes in the bottom wall 12c of the control module 12. These columns 17 ensure the guidance of the translational movement of the control module 12 relative to the casing 8 while preventing the relative rotation of the module 12 relative to the casing 8.

[0092] The nut 29 is also immobilized in translation relative to the control module 12 by means of two walls 35 secured to the control module 12.

[0093] The walls 35 may have surfaces covered with an anti-friction coating to facilitate the rotation of the nut 29. Depending on the necessary strokes, they may possibly be drilled so as not to hinder the passage of the column 17.

[0094] The central axis 30 being immobile in rotation and in translation relative to the casing 8, the rotation of the motor 27 will cause the rotation of the nut 29 which, being integral in translation with the control module 12, will cause the axial displacement of the control module 12 along the central axis 30.

[0095] It is thus possible to move the control module 12 to give it: its rear position, resting against the casing 8 of the military load 9; its front position in which the pilot module 12 closes the air inlet 11; but also any intermediate position between these two extreme positions.

[0096] It is thus easy to control the longitudinal position of the control module 12 and, unlike the embodiment previously described, it becomes possible to move the control module 12 axially in a manner decorrelated from the firing of the projectile.

[0097] As seen on the figure 5 , the control module 12 comprises a rear skirt 36 which slides on an external wall 8b of the casing 8. Such an arrangement makes it possible to improve the continuity of the air flow during operation of the ramjet and for all longitudinal positions of the control module 12.

[0098] It also ensures a seal at this level, preventing air from entering the control module 12.

[0099] Thanks to this embodiment of the invention, it thus becomes possible to delay the start of the propulsion phase in relation to the cannon shot.

[0100] We then define a time, called the ignition time, at which the recoil of the control module 12 will be commanded after the shot, thus causing the ignition of the ramjet.

[0101] Such an arrangement proves to be interesting from an operational point of view to improve the stealth of the shot by avoiding the ignition flashes of the semi-propellant block 7. It also makes it possible to optimize the trajectory profile of the projectile 1. This embodiment also makes it possible to avoid exceeding Mach 5 when shooting at high initial speed.

[0102] Thanks to this embodiment, it is also possible to vary the section of the air inlet 11 depending on the altitude of the projectile.

[0103] It is known that a ramjet requires a larger cross-section air inlet for high altitudes.

[0104] The calculation means 16 will thus be able to control, at the end of a first time interval (at the instant of ignition) after the exit of the weapon tube (of the order of a few tenths of a second), the recoil of the control module 12 to open the air inlet 11 of a minimum section allowing the ramjet to be ignited.

[0105] After a second defined time interval, the calculation means 16 will cause the control module 12 to move back again to open the air inlet 11 a little more and thus optimize the operation of the ramjet by increasing the air flow for an altitude at which the air is less dense.

[0106] The calculation means 16 can thus move, progressively or incrementally, at different times on the trajectory, the control module 12 from its front position (air inlet 11 closed) to its rear position (maximum opening of the air inlet 11).

[0107] As an indicative example, we have shown in the figure 6 three curves S 1 , S 2 and S 3 which show the evolution of the admitted air flow (in kilograms per second - Kg / s) through an air inlet of constant section and as a function of the altitude H (in meters) of the projectile 1. This flow decreases with altitude because the air is less dense at altitude and it also depends on the speed.

[0108] According to this indicative example, curve S 1 corresponds to an air inlet section of 3000 mm 2< , curve S 2 corresponds to an air inlet section of 4000 mm 2< and curve S 3 corresponds to an air inlet section of 5000 mm 2< .

[0109] We can therefore see that, to maintain the same flow rate in the ramjet, it is sufficient to increase the section of the air inlet 11. For example, if we want to center the flow rate around 3 kg / s, we will increase the section from a value of the order of 3000 mm 2< between 0 and 3000 m altitude to a section of 4000 mm 2< between 3000 and 6000 m altitude, then to a section of 5000 mm 2< between 6000 m and 9500 m altitude.

[0110] Knowing the altitude of the points at which the section of the air inlet 11 and the firing table of the projectile must be modified, we also know the times at which the calculation means 16 must send the movement orders of the control module 12 as well as the amplitude that must be given to the movement to increase the section (the displacement / section ratio is a construction datum of the projectile). The times between each movement are of the order of 4 to 5 seconds. The increase in the section of the air inlet 11 can also be controlled continuously.

[0111] As an example, we have represented the figure 7 the different flight phases of the projectile 1 according to this variant of the invention.

[0112] After firing, and at a first instant I 1 or ignition instant (here approximately 5 km from the weapon), the control module 12 is moved back to open the air inlet 11 and ignite the ramjet.

[0113] At a second instant I 2 (here approximately 10 km from the weapon), the pilot module 12 is moved back a little further to open the air intake 11 more, which improves the operation of the ramjet at a higher altitude (here 10 km).

[0114] At a third instant I 3 (here approximately 15 km from the weapon), the pilot module 12 is moved even further back to open the air intake 11 to its maximum opening, which improves the operation of the ramjet at an even higher altitude (here 15 km).

[0115] When the projectile 1 is at its apogee A (at the defined extinction instant), the electric motor 27 returns the pilot module 12 to its forward position in which it closes the air inlet 11 which extinguishes the ramjet. At the same time the canard control surfaces 15 are deployed and the piloted phase G begins.

[0116] According to a particular embodiment, it will be possible in the final phase Af, to move the control module 12 back again so as to open the air inlet 11 again and relight the propulsion unit 7 of the ramjet.

[0117] This command will intervene when the projectile 1 is oriented towards its target T and it will therefore no longer be necessary to correct its trajectory. The control surfaces 15 can, during this movement, be embedded on the body 2 around the air inlet 11, which no longer presents any disadvantages, guidance having become unnecessary. The control surfaces can alternatively fold forward in the module according to the design of their kinematics.

[0118] It will also be possible to define canard control surfaces 15 comprising a pivot axis positioning the control surface wing at a radial distance from the control module 12 which thus allows the control module 12 to move backwards, with control surfaces deployed, with minimal mechanical disturbances or interference.

[0119] This final acceleration of projectile 1, lasting approximately 2 seconds, is not essential but it increases the kinetic energy of projectile 1 at the end of its trajectory and also increases the stealth of the attack. The flight of the projectile returns to supersonic speed and the speed at impact on the target is of the order of Mach 2.

Claims

1. - A ramjet-propelled projectile, the projectile (1) comprising an outer body (2) and a deployable tail unit (3), the projectile comprising, inside the body, a chamber (6) in which is housed a block (7) of ablatable annular solid-propellant and an casing (8) enclosing a military load, the outer body (2) comprising an air inlet (11) for allowing air to enter the chamber (6), the body also comprising a rear opening (13) on which a nozzle (14) is positioned, the projectile bring characterised in that it comprises a control module (12) arranged axially and that extends through the air inlet (11), the control module (12) being able to be moved axially by a motor means (18, 27), during the flight of the projectile (1) and at a defined instant on a trajectory, referred to as instant of extinction, from a rear position in which it does not close the air inlet (11) toward a forward position in which it closes the air inlet (11), the control module (12) enclosing at least two canard controls (15) which are deployable outside the projectile (1) after closing the air inlet (11).

2. - The propelled projectile according to claim 1, characterised in that the control module (12) contains a calculation means (16) incorporating driving algorithms, the calculation means (16) controlling the movement of the control module (12) at the instant of extinction.

3. - The propelled projectile according to one of claims 1 or 2, characterised in that it constitutes an artillery projectile intended to be fired by a gun, wherein the outer body of the projectile carries a slipping obturator ring (5).

4. - The propelled projectile according to claim 3, characterised in that the control module (12) is in its forward position before firing, the control module (12) recoiling by inertia during firing so as to occupy its rear position in which it bears against the casing (8) of the military load.

5. - The propelled projectile according to claim 4, characterised in that it comprises a locking means (21) ensuring the immobilisation of the control module (12) in the rear position.

6. - The propelled projectile according to claim 5, characterised in that the motor means (18) comprises an elastic potential energy storage means, this means being activated by the recoil of the control module (12) from its front part to its rear part, the locking means (21) being released at the instant of extinction defined on the trajectory.

7. - The propelled projectile according to claim 3, characterised in that before firing the control module (12) is in its forward position before firing, the control module (12) being able to be moved by the motor means (27), after firing and at a instant, referred to as the ignition instant, defined on the trajectory, so as to come to occupy its rear position.

8. - The propelled projectile according to claim 7, characterised in that the motor means (27) can move, progressively or incrementally, at different successive instants defined on the trajectory, the control module (12) from its forward position to its rear position.

9. - The propelled projectile according to one of claims 7 or 8, characterised in that the motor means (27) can move the control module (12) toward its rear position at the end of the controlled phase so as to clear the air inlet (11) and thus accelerate the projectile (1) during a terminal phase (Af) of its trajectory.

10. - The propelled projectile according to one of claims 7 to 9, characterised in that the control module (12) comprises a rear skirt (36) which can slide on an outer wall (8b) of the casing (8) during the movement of the control module (12) so as to improve the continuity of the flow of air during operation of the ramjet and for all longitudinal positions of the control module (12).

11. - The propelled projectile according to one of claims 3 to 10, characterised in that it comprises a rear base (4) closing the nozzle (14) during firing, the base (4) holding the rear tail unit (3) and being ejected at the exit of the gun.