Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B10/00—Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding
  • F42B10/32—Range-reducing or range-increasing arrangements; Fall-retarding means
  • F42B10/48—Range-reducing, destabilising or braking arrangements, e.g. impact-braking arrangements; Fall-retarding means, e.g. balloons, rockets for braking or fall-retarding

Definitions

• the technical field of the invention is that of methods and devices making it possible to ensure the correction of the trajectory of a gyrostabilized projectile.
• This deployment is controlled on a trajectory at a given instant programmed before firing or on a trajectory, or else at an instant which is determined on a trajectory according to the coordinates of the targeted target and the coordinates of the projectile (measured by an inertial unit or a system satellite positioning system (GPS)).
• GPS satellite positioning system
• Such a method makes it possible to modify the range of the projectile, it thus makes it possible to correct the errors due to variations in the initial speed which are essentially linked to the firing conditions (atmospheric conditions, temperature, dispersion of the characteristics of the propellant powders, wear of the tube of tear).
• a gyrostabilized projectile has a lateral diversion movement relative to the firing axis, a movement which is essentially due to the fact that the projectile has a longitudinal axis which has an angle with respect to its velocity vector.
• This angle is naturally adopted by the projectile and it allows it to balance the gyroscopic torque undergone. It is proportional to the speed of rotation of the projectile and to its moment of inertia in roll. It is also inversely proportional to the static margin of the projectile, that is to say to the distance separating the center of gravity of the projectile from the focus of the aerodynamic forces.
• the induced diversion reaches from 300m to 800m for ranges ranging from 15 km to 25 km. This diversion also varies according to the firing conditions (dispersion on the speed of rotation of the projectile, lateral wind ). It is known from patent WO02061363 to correct this derivation by deploying aerodynamic fins ensuring braking of the rotation. These fins are arranged at the level of the warhead, or of a median part of the projectile body, or else at the level of the base.
• Patent FR276,689 describes another solution in which deployable fins are arranged at the base of the projectile. These fins also provide moderate braking of the rotation but, because of their arrangement behind the projectile, they mainly have the effect of reducing the static margin of the projectile, thus allowing an increase in the bypass. This solution also has drawbacks.
• the fins are a complex and fragile mechanism. It is therefore difficult to arrange them at a part of the projectile subjected to the pressure of the propellant gases, therefore very mechanically stressed. The arrangement of the fins in the rear part of the projectile also complicates their integration and assembly.
• the fins are then very far from the projectile warhead which generally carries the rocket for controlling the ignition and which incorporates the electronic control means.
• the control of the fins from the rocket therefore requires the establishment of an electrical connection between the front and rear of the projectile which complicates the production of such a projectile.
• the method according to the invention is easy to implement. It authorizes the production of projectiles whose diversion can be corrected using a simple device, easy to integrate into a projectile, possibly in an existing projectile.
• the subject of the invention is a method for correcting the trajectory of a gyro-stabilized projectile, a method in which at least a correction is made to the axial position of the aerodynamic center of thrust of the projectile, a method characterized in that the correction of the axial position of the center of thrust is obtained by modifying at least once the length of the projectile in flight, modification which is caused by a control means.
• the modification of the length of the projectile in flight can be obtained by ejecting a section of the projectile.
• the section thus ejected will advantageously be disposed at a front part of the projectile.
• the modification of the length of the projectile in flight can be obtained by the relative translation of a front part of the projectile relative to a rear part.
• the invention also relates to a projectile implementing such a method.
• This projectile comprises means of simple design and ensuring at least a correction of its derivation on trajectory.
• the projectile may comprise at least one section made integral with a projectile body by an unlockable connecting means.
• the unlockable section on the trajectory may be a cap disposed at a front part of the projectile.
• the projectile may include a telescopic warhead mounted to slide relative to the body of the projectile, warhead constituting a front part of the projectile which can move relative to a rear part formed by the body of the projectile, the warhead being made integral with the body by an unlockable connecting means.
• the warhead may contain a gas generator which will be initiated on the trajectory by the control means, the pressure of the gases causing the shear of the warhead / body connection means and the translation of the warhead forwards until a stop thus leading to an elongation of the projectile.
• the unlockable connecting means is actuated by the control means and the release of the warhead allows the latter to be translated rearward relative to the body under the effect of aerodynamic pressure thus leading to a shortening of the projectile.
• the projectile comprises a base mounted to slide relative to the body of the projectile, base constituting a rear part of the projectile which can move relative to a front part formed by the body of the projectile, the base being made integral with the body by an unlockable connecting means.
• the projectile may comprise at least one flap, the radial deployment of which will be caused by the control means, flap ensuring aerodynamic braking of the projectile and a shortening of the scope thereof.
• FIGS. 1a and 1b schematize a first embodiment of a projectile according to the invention, FIG. 1a showing the projectile before correction and FIG. 1b after correction,
• FIGS. 2a and 2b show diagrammatically a second embodiment of a projectile according to the invention, FIG. 2a showing the projectile before correction and FIG. 2b after correction,
• FIG. 3a and 3b show schematically a third embodiment of a projectile according to the invention, Figure 3a showing the projectile before correction and FIG. 3b after correction,
• FIGS. 4a and 4b show diagrammatically a fourth embodiment of a projectile according to the invention, FIG. 4a showing the projectile before correction and FIG. 4b after correction,
• FIGS. 7a, 7b and 7c show diagrammatically a sixth embodiment of a projectile according to l invention, FIG. 7a showing the projectile before correction, FIG. 7b after correction of the shunt and FIG. 7c after correction of the range, - FIG. 8 is a diagram showing the area of correction that it is possible to obtain with a projectile incorporating a device ensuring correction of the range and the bypass.
• a projectile 1 according to a first embodiment of the invention and implementing the correction method according to the invention comprises a body 2 which is not shown in detail and which will incorporate an explosive arranged in an envelope and initiated by a rocket 3, for example a proximity rocket or a chronometric rocket.
• the body 2 may alternatively contain a dispersible payload, for example submunitions.
• the projectile is for example a 155mm artillery shell.
• the projectile comprises a cap 4 disposed at a front part of the projectile.
• This cap forms a section of projectile 1 which is linked to the body 2 thereof by means unlockable link, for example a shear pin 5.
• the cap 4 contains a gas-generating pyrotechnic charge 6 which can be initiated by an electronic control means 7.
• This control means will for example comprise a microprocessor, programmed before firing or on a trajectory, and which will cause the pyrotechnic charge 6 to ignite at a desired time.
• the pressure of the gases generated by the latter will cause the shearing means 5 to shear, which will lead to the ejection of the cap 4 on the trajectory.
• the ejection of the cap 4 has the effect of modifying the length of the projectile in flight 1 (here the projectile is shortened).
• the invention makes it possible to reduce the static margin by 15% this which leads to a deviation of 100 m to 25 km.
• the maximum potential for adjusting the bypass is 100 m and it depends on the moment at which the cap is ejected.
• FIG. 5a thus shows a network of curves of. derivation corresponding to such a decrease in the static margin.
• the lowest curve (Cl) corresponds to the firing of the projectile without ejection of the cap (maximum static margin).
• the upper curve (C4) corresponds to the firing of the projectile with an ejection of the cap after 10 seconds of flight, which corresponds to the maximum diversion that it is possible to obtain.
• the intermediate curves correspond to derivations obtained for cap ejections ordered respectively after 40 s (curve C2) and 20s (curve C3). It is thus possible to vary the lateral diversion from almost 100 m to 25 km.
• the embodiment of Figures la and lb provides for modifying the axial position of the center of thrust by ejecting part of the projectile (the cap).
• the length of the projectile in flight will be modified at least once by controlling not an ejection of a part of the projectile but a relative translation of a front part of the projectile relative to a part back.
• the projectile 1 has a body 2 shown here schematically and which will contain an explosive or other dispersible payload (submunitions for example).
• the explosive will be initiated (or the payload dispersed) by the rocket in a known manner and not shown here.
• the body 2 has an external cylindrical bearing surface 10 on which is slidably disposed a warhead 11 which carries the rocket 3.
• the warhead is made integral with the body by at least one transverse shear pin 12 which constitutes an unlockable connection means.
• the warhead 11 contains a gas-generating pyrotechnic charge 13 which can be initiated by an electronic control means integrated into the rocket 3.
• This control means will for example comprise a microprocessor, programmed before firing or on a trajectory, and which will cause the ignition of the pyrotechnic charge 13 at a desired instant.
• the pressure of the gases generated by the latter will cause the shearing of the connecting means 12 and the translation of the warhead 11 forwards (in the direction FI), therefore the elongation of the projectile.
• the warhead translates forward, guided by at least one radial pin 14 which slides in a groove 15 carried by the warhead 11 (preferably three radial pins regularly distributed angularly).
• the pin 14 constitutes an axial stop which limits the translation of the warhead forwards.
• the telescopic warhead constitutes a front part of the projectile which can move relative to a rear part formed by the body of the projectile.
• the mass of the warhead is small compared to the total mass of the projectile, the displacement of the center of gravity G is therefore negligible compared to that of the aerodynamic focus F.
• the initial static margin Do is less than the final static margin Di.
• firing tables will be established making it possible to define, for a given projectile geometry and given firing conditions, the networks of the derivation curves obtained as a function of the distance between the projectile and the weapon and according to the instants at which the static margin of the projectile is modified.
• FIG. 5b shows a network of derivation curves corresponding to such an increase in the static margin.
• the highest curve (Cl) corresponds to the firing of the projectile without translation of the warhead (minimum static margin).
• the lower curve (C'4) corresponds to the firing of the projectile with a translation of the warhead after 10 seconds of flight, which corresponds to the minimum diversion that it is possible to obtain.
• the intermediate curves correspond to derivations obtained for translation of the warhead controlled respectively after 20 s (curve C3) and 40s (curve C'2). It is thus possible to vary the lateral diversion from almost 100 m to 25 km.
• the invention makes it possible to increase the static margin by 15% which leads to a diversion of 100 m to 25 km.
• the maximum adjustment potential of the bypass is 100 m and it depends on the instant at which the translation of the warhead is controlled.
• Figures 3a and 3b show another embodiment which differs from the previous in that the unlockable connecting means is constituted by a pyrotechnic retractor 16 (shown diagrammatically integral with the body 2 and with its sliding latch rod 16a engaged in the warhead 11 ). This retractor maintains the warhead 11 in its advanced position shown in Figure 4a.
• a pyrotechnic retractor 16 shown diagrammatically integral with the body 2 and with its sliding latch rod 16a engaged in the warhead 11 . This retractor maintains the warhead 11 in its advanced position shown in Figure 4a.
• Figures 4a and 4b show a projectile according to a fourth embodiment of the invention.
• This projectile 1 is again shown schematically. It comprises a body 2 which is not shown in detail and which will incorporate an explosive placed in an envelope and initiated by a warhead rocket 3, for example a proximity rocket or a chronometric rocket.
• the body 2 may also contain a dispersible payload, for example submunitions.
• the projectile 1 comprises a base 8 which is slidably mounted on an external cylindrical surface 18 arranged on the outside of the body 2.
• the base 8 is made integral with the body 2 by at least one shearable transverse pin 19 which constitutes an unlockable connection means.
• a gas-generating pyrotechnic charge 20 is disposed in a housing at the rear of the projectile body. This charge can be initiated by an electronic control means 21. The latter is here represented near the charge 20. It could alternatively be integrated into the rocket 3 and connected to an igniter (not shown) of the charge 20 by wires of connection.
• the control means will for example comprise a microprocessor, programmed before firing or on a trajectory, and which will cause the pyrotechnic charge 20 to ignite at a desired instant.
• the pressure of the gases generated by the charge 20 will cause the connecting means 19 to shear. and the translation of the base 8 backwards (in the direction F3), therefore the elongation of the projectile.
• the base 8 translates backwards while being guided by at least one radial pin 22 which slides in a groove 23 carried by the base 8 (preferably three radial pins regularly distributed angularly) will be provided.
• the pin 22 constitutes an axial stop which limits the translation of the base 8 towards the rear.
• the base constitutes a rear part of the projectile which can move relative to a front part formed by the body of the projectile.
• This device makes it possible to reduce the static margin due to the fact that the aerodynamic focus is moved back towards the rear of the projectile without significantly moving the position of the center of gravity G (mass of the base much less than the total mass of the projectile).
• the initial static margin Do is therefore greater than the final static margin Di.
• the network of branch curves is similar to that shown in Figure 5a.
• the embodiments described above make it possible to make a correction only to the derivation of a projectile.
• FIGS. 6a, 6b and 6c show an embodiment of a projectile 1 according to the invention incorporating means ensuring a correction in range and means ensuring a correction in diversion.
• a telescopic warhead 11 is made integral with the body 2 of the projectile by an unlockable connecting means 16 which is a pyrotechnic retractor.
• the retractor 16 is actuated by the rocket 3, the warhead translates towards the rear and the projectile 1 is shortened
• the rocket 3 controls the radial deployment of flaps 17. These flaps ensure the aerodynamic braking of the projectile, therefore the shortening of its trajectory.
• the mechanical structure of the flaps is not described in detail and reference may be made to one or other of the patents FR2786561 and FR2792400 for more details on such a structure. It is then possible by playing on the relative instants of triggering of the telescopic warhead (correction in diversion) and aerodynamic flaps (correction in range) to make two successive trajectory corrections allowing to obtain a point of impact on the ground located within a large adjustment range.
• FIG. 8 shows the range of adjustment that it is possible to obtain for an artillery shell of 155mm mass 42 kg fired with an initial speed of 810 m / s and an angle of elevation of 50 °.
• This shell is fitted with a retractable warhead allowing the static margin to be reduced by 15% and comprising deployable flaps ensuring a doubling of the projectile's drag.
• the projectile according to the invention makes it possible to vary the range in a range of 500 m and the diversion in a range of 100 m.
• FIGS. 7a, 7b and 7c show another embodiment of the invention combining correction in range and correction in derivation.
• This mode differs from the previous one in that the derivation correction is obtained according to the solution described above with reference to FIGS. 2a and 2b.
• the telescopic warhead 11 is made integral with the body 2 of the projectile by an unlockable connecting means 12 which is a pin which can be sheared by the pressure of the gases generated by a pyrotechnic gas generator 13.
• the generator 13 is controlled by the rocket 3, the warhead moves forward and the projectile 1 lengthens (Figure 7b).
• the static margin is increased (D ⁇ > Do) which decreases the derivation of the projectile.
• the rocket 3 controls the radial deployment of flaps 17. These flaps ensure the aerodynamic braking of the projectile, therefore the shortening of its trajectory.
• an artillery shell of 155mm mass 42 kg fired with an initial speed of 810 m / s and a site angle of 50 ° is provided with a telescopic warhead making it possible to increase the static margin by 15 %.
• This shell also includes deployable flaps ensuring a doubling of the projectile drag.
• FIGS. 4a and 4b projectile with sliding base
• rocket provided with braking flaps.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)

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• 2002
  • 2002-11-08 FR FR0214137A patent/FR2847034B1/fr not_active Expired - Fee Related
• 2003
  • 2003-11-05 US US10/517,146 patent/US20050173588A1/en not_active Abandoned
  • 2003-11-05 EP EP03767914A patent/EP1565703A2/de not_active Withdrawn
  • 2003-11-05 WO PCT/FR2003/003302 patent/WO2004044517A2/fr not_active Ceased

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