FR2793017A1 - PROJECTILE WITH BALISTICALLY CONTROLLED - Google Patents

Abstract

The invention concerns a projectile, in particular to be used in the field of fireworks, characterised in that it comprises a leading front face (10) a peripheral envelope (30) separated by a transitional ridge (20) located in a plane (P) perpendicular to the axis (O-O) of the projectile, said front face (10) not extending upstream of said plane (P).

Description

The present invention relates to the field of projectiles.

  It applies to all types of projectiles or rockets

  self-propelled or not, especially ballistic.

  The present invention relates in particular, but not exclusively, to projectiles having applications in the field of

fireworks.

  The object of the present invention is to propose, with simple technical means, a stable projectile with respect to its ballistic axis and

without rotation or roll.

  The present invention can notably be applied in the field of fireworks, for the generation, in the air, of figures, symbols, or even letters or equivalents having a geometry and a

controlled orientation.

  Much work has already been done in this area.

  The method generally proposed for making patterns such as a circle, triangle, number or other forms, consists of storing stars

  in a bomb body in the same layout as the motive itself.

  These stars are agglomerates made from a pyrotechnic composition which burns with a flame color characteristic of the

formulation used.

  At the moment of the explosion of the bomb, the stars are lit and dispersed in the atmosphere and will represent the desired motive by

  several points of light, each point being made by a star.

  The fineness of the pattern depends in this case on the number of stars

embedded in the bomb.

  Document FR-A-2764687 and FR-A-2764688 discloses another solution in the form of a pyrotechnic projectile comprising a body containing a bursting charge and a combustible charge whose ignition and dispersion are ensured. by exploding the bursting charge, wherein the combustible charge is formed by a combustible metal powder with the oxygen of the air, disposed within the bursting charge in a pattern corresponding to the shape of the pattern

fireworks to get in the sky.

  As regards the control of the orientation of the projectiles, it is generally proposed to search for it by means of fins arranged on the

  outer periphery of the projectile.

  However to the knowledge of the Applicant none of the devices so far proposed are fully satisfactory, especially in terms of stability, except embarkation means

  piloting complexes, which the present invention seeks to avoid.

  The study of the parameters governing the stability of a projectile is in

very complex effect.

  For example, a theoretical approach to cylinder aerodynamics can be found in "Theories of Dynamics".

  fluids "A. Bonnet, J. Luneau (Cépadues editions).

  Being reminded that we call "slender", a body whose longitudinal dimension measured parallel to the velocity vector is much larger than its transverse dimensions (Rockets and missiles are characteristic examples of slender bodies) and that the singularities method is a method to solve the Laplace equation (AV = 0) to determine the flow around a

  obstacle, the basis of the theory is as follows.

  The theory of slender bodies is a linearized version of the singularities method. It is therefore applicable only for obstacles whose local slope of the walls, relative to the speed vector at infinity remains sufficiently low. It allows for example to address the calculation of aerodynamic forces on the body of a missile or fuselage of revolution to

low incidences.

  In the framework of the theory of slender bodies, the expression of the moment of pitching with respect to any point A is Mz = 1/2 pO V. SrefLrefCm., 3a0 o Cm 2 Lrea Sve LcaSe, with v the volume of the body considered, L the total length of the craft, XA the distance between the nose is the point A, Sq the surface of the base of the craft, VX. the velocity at infinity upstream, po the fluid density at infinity upstream, Sre, the reference surface, Lref the reference length,

-ca the incidence.

  In the case where A is the instantaneous center of rotation, for example gravity G of a body in free flight, the preceding formula, giving the pitch moment coefficient with respect to G, allows, as a function of

  geometric data of the body, to define its stability conditions.

  The body is stable if, at a change of incidence Act, negative or positive, the moment of the forces acting on the body tends to eliminate

this variation of incidence.

  The condition of stability is thus: ac> 0 aa of o (L - xg) Sq - v> 0 is, since XL> 0 L

0 <'I <1 -'

L LS &,

  It can be deduced that the main parameter to be controlled to obtain a

  stable projectile would be the position of its center of gravity.

  However, the Applicant has found that this parameter was far from sufficient and deviating from the accepted prejudices of those skilled in the art, has developed a new structure that differs from previous projectiles

  known, especially by the geometry of its attacking face.

  Thus, the above object is achieved in the context of the present invention by means of a projectile comprising a front face of attack and a peripheral envelope separated by a transitory ridge situated in a plane perpendicular to the axis of the projectile, and in which the front face

  attack does not extend upstream of this plane.

  In other words, the present invention recommends using a projectile without warhead. However, in the case of such a cylinder without warhead, the volume v of the cylinder is equal to the quantity LSq. It would therefore theoretically that the center of gravity is on the front so that the cylinder is stable at zero incidence to meet the established criteria mentioned above. Thus, the theory suggested that such a cylinder is unstable at low incidences. However, the Applicant has demonstrated that a priori very surprising a projectile meeting the characteristics indicated

  previously, helps to meet the desired goal.

  Other features, purposes and benefits of this

  invention will appear on reading the detailed description which follows and

  with reference to the accompanying drawings, given as non-limiting examples and in which: FIG. 1 represents a schematic side view of a projectile according to the present invention, FIGS. 2 and 3 represent views in axial section of FIG. two embodiments of the front attack face of a projectile according to the present invention, and - Figure 4 shows an axial sectional view of the rear portion of a

  projectile according to an alternative embodiment of the present invention.

  After extensive studies and research and numerous tests, the Applicant has determined that to obtain a projectile stable relative to its ballistic axis and without rotating or rolling, it is desirable to control in particular the following parameters: a) the geometry of the front face 10, b) the length ratio (L1) / transverse dimension (D1), c) the nature of the transition 20 between the front face 10 and the surface

  device 30 and d) the position of the center of gravity of the projectile.

  With regard to the geometry of the leading edge before 10, the Applicant has determined, as previously indicated, that it is desirable for the transition edge 20 between the leading front face 10 and the peripheral surface 30 to be located in a plane P perpendicular to the O-O axis of the projectile. Moreover, the Applicant has determined that unlike known projectiles which have a leading face tapered forward, this leading face 10 should preferably not extend upstream of this

  plane P, to obtain a projectile of great stability.

  Thus preferably, the front face 10 is flat and located in this plane P. However, if necessary, the front face 10 may be concave type recessed relative to this plane P, from the edge 20, as

  illustrated for example in Figures 2 and 3.

  FIG. 2 thus illustrates a variant of concave driving face 10 with continuous curvature, for example globally spherical, while the leading face 10 illustrated in FIG. 3 is staggered (here it has a central cavity 12, bordered by a ring 11 located in the plane P, and delimited by a cylindrical skirt of revolution 13 and a flat bottom 14 parallel to the plane P. The foregoing characteristics have been highlighted by the

  Applicant essentially following many tests.

  Indeed, they go against the generally accepted theories that require, as recalled earlier, a tapered attack face

forward.

  Regarding the ratio between the length L1 and the dimension D1 transverse to the axis OO of the projectile, the Applicant to determine that preferably this ratio L1 / D1 is between 0.25 and 20, very preferably between 0.5 and 12, and even between 1 and 3 and

advantageously of the order of 2.5.

  With regard to the transition 20 between the front face and the peripheral surface 30, the Applicant has determined that it is

  preferably formed of a sharp edge without pronounced chamfer or rounding.

  As regards the position of the center of gravity of the projectile, the Applicant has determined that, preferably, for the munition to be stable at zero incidence, it is necessary for the center of gravity to be located approximately in two-thirds of the front of the munition, preferentially in the half before the ammo, and even very

  advantageously to have good stability in the first third.

  Moreover, the Applicant has found that preferably the projectile, therefore its peripheral surface 30, is included in a

  straight cylinder resting on the transition edge 20.

  The aforementioned peripheral surface 30 may be cylindrical, that is to say

  defined by a straight generatrix parallel to the longitudinal axis O-O.

  However, this last characteristic is not absolutely mandatory.

  The peripheral surface 30 may in fact have, at least over a part of the length of the projectile, recessed areas with respect to the cylinder

  right based on the transition edge 20.

  It is thus possible, for example, to envisage the peripheral surface 30 being delimited by a concave curved generatrix towards the outside of the munition. According to another embodiment, the peripheral surface 30 is delimited by a section which converges towards the rear of the projectile. Preferably, the projectile has a symmetry with respect to its

longitudinal axis O-O.

  It may have a circular cross section, the peripheral surface 30 being then for example cylindrical of revolution. Alternatively, the cross section of the projectile may be polygon type or

have flats.

  On this point the Applicant has indeed found that a cylindrical projectile provided with flats behaves substantially in the same way

  in flight than a cylinder of revolution.

  By way of nonlimiting example, the peripheral surface 30 of the projectile may comprise three flats equi-distributed around the longitudinal axis OO, each flat having for example a rope of a length of the order of 10 mm for a projectile having a diameter of mm. Moreover, the Applicant has determined that, preferably, the propulsion means associated with the projectile are calculated so that the velocity of the projectile in ballistic phase external to the launcher is between 25 and 250 m / s, advantageously of the order of 60 to 120m / s and very

  preferably of the order of 100 m / s.

  The Applicant has indeed determined that these ranges of value were necessary to allow the projectile according to the invention to fly correctly, despite its geometry which deviates from that generally

admitted by those skilled in the art.

  The foregoing essentially concerns the

external ballistics of the projectile.

  The Applicant has also determined that, preferably, it is desirable to treat the internal ballistics elements to obtain a

  projectile stable with respect to its ballistic axis and without rotation or roll.

  In this field, the Applicant has determined that, where appropriate, as illustrated in FIG. 4, the projectile may be equipped at its rear part with a skirt 40, for example cylindrical, or even

  cylindrical of revolution centered on the axis O-O.

  Of course, the present invention is not limited to the particular embodiments which have just been described, but extends to all

variants consistent with his spirit.

Claims (27)

  1. Projectile, characterized in that it comprises a. front face of attack (10) and a peripheral envelope (30) separated by a transition edge (20) located in a plane (P) perpendicular to the axis (O-O) of   projectile, said front face (10) not extending upstream of this plane (P).   2. Projectile according to claim 1, characterized in that the peripheral surface (30) is included in a straight cylinder resting on The transition edge (20).   3. Projectile according to one of claims 1 or 2, characterized by the   that the front face (10) is flat and located in the plane (P) containing the transition edge (20).   4. Projectile according to one of claims 1 or 2, characterized by   the fact that the front face (10) is concave and set back from the plane   (P) containing the transition edge (20).   5. Projectile according to claim 4, characterized in that the front driving face (10) is concave with continuous curvature, for example globally spherical.   6. Projectile according to claim 4, characterized in that the   front attack face (10) is stepped.   7. Projectile according to one of claims 1 to 6, characterized by the   the ratio (L1 / D1) between the length and the transverse dimension of the   projectile is between 0.25 and 20.   8. Projectile according to one of claims 1 to 7, characterized by the   the ratio (L1 / D1) between the length and the transverse dimension of the   projectile is between 0.5 and 12.   9. Projectile according to one of claims 1 to 8, characterized by the   the ratio (L1 / D1) between the length and the transverse dimension of the   projectile is between 1 and 3.   10. Projectile according to one of claims 1 to 9, characterized by   the fact that the ratio (L1 / D1) between the length and the transverse dimension   of the projectile is of the order of 2.5.   11. Projectile according to one of claims 1 to 10, characterized by   the fact that the transition (20) between the front face (10) and the surface   peripheral (30) is sharp without pronounced chamfering or rounding.   12. Projectile according to one of claims 1 to 11, characterized by   the fact that the center of gravity of the projectile is within 2/3 before of it.   13. Projectile according to one of claims 1 to 12, characterized by   the fact that the center of gravity of the projectile is included in the front half of it.   14. Projectile according to one of claims 1 to 13, characterized by   the fact that the center of gravity of the projectile is included in the first third before this one.   15. Projectile according to one of claims 1 to 14, characterized by   the fact that the peripheral surface (30) is cylindrical.   16. Projectile according to one of claims 1 to 14, characterized by   the fact that the section of the peripheral surface (30) converges towards the rear of the projectile.   17. Projectile according to one of claims 1 to 16, characterized by   the fact that the peripheral surface (30) has a symmetry with respect to The longitudinal axis (O-O).   Projectile according to one of Claims 1 to 17, characterized by   the fact that the peripheral surface (30) has a cross-section   symmetrical of revolution around the longitudinal axis (O-O).   19. Projectile according to one of claims 1 to 17, characterized by   the fact that the cross-section of the peripheral surface (30) is of the polygon type.   20. Projectile according to one of claims 1 to 17, characterized by   the fact that the peripheral surface (30) has at least one flat part.   21. Projectile according to one of claims 1 to 17 and 20,   characterized in that the peripheral surface (30) comprises three equi-distributed flats.   22. Projectile according to one of claims 1 to 21, characterized by   the fact that the propulsion means are adapted to generate a speed   projectile in external ballistics between 25 and 250m / s.   23. Projectile according to one of claims 1 to 22, characterized by   the fact that the propulsion means are adapted to generate a speed   projectile in external ballistics between 60 and 120m / s.   24. Projectile according to one of claims 1 to 23, characterized by   the fact that the propulsion means are adapted to generate a speed   in external ballistics phase of the order of 1 OOm / s.   Projectile according to one of claims 1 to 24, characterized by   the fact that the projectile has in its rear part an annular skirt (40).   26. Projectile according to one of claims 1 to 25, characterized by   the fact that it comprises a payload capable of forming fireworks.   27. Projectile according to one of claims 1 to 26, characterized by   the fact that it comprises a payload capable of forming a symbol of   controlled geometry in the air.