Patent Publication Number: US-10788297-B2

Title: Artillery projectile with a piloted phase

Description:
This application is a continuation application of U.S. patent application Ser. No. 15/278,653, filed on Sep. 28, 2016, which is in turn claims foreign priority based on French Patent Application No. FR1502030, filed Sep. 29, 2015. The disclosures of the prior U.S. and French applications are hereby expressly incorporated by reference herein in their entirety. 
    
    
     The technical field of the invention is that of artillery projectiles intended to have a trajectory comprising a ballistic initial phase and a piloted phase. 
     The aim today is to provide artillery projectiles (or shells) having an extended range and being able to be piloted for controlling their trajectory, searching and reaching a particular target. 
     The piloting means most often have canard controls which are provided at a front part of the projectile and are controlled by motor-reduction units (individually or on a plane by plane basis). The front part of the projectile incorporates a homing device and a computer allowing to guide and pilot the projectile towards a particular target the signature characteristics of which will have been stored in the computer. A satellite positioning system can also be implemented in the projectile flight control chain. 
     These projectiles can have a significant range at a lower cost due to the firing by an artillery gun which allows to get a shell of 45 kg at an altitude higher than 10 km within one minute of flight. 
     This type of projectile completes the range of shells which can be implemented by a same artillery system. The versatility of a weapon system responds to a recurrent operational need of the forces. 
     Further, the ballistic firing by a gun allows to obtain a relative accuracy for the positioning of the projectile with respect to an area (or firing window) where potential targets are located. 
     With the same accuracy, the artillery projectiles thus have a cost lower than that of missiles which must be piloted on their entire trajectory and which must carry a propelling charge. 
     One of the characteristics of the conventional artillery projectiles is that they are gyroscopically stabilized, the rotation being transmitted by the barrel grooves during the ballistic movement. This stabilization mode becomes a disadvantage for the artillery projectiles having a ballistic phase and a piloted phase because they must have a reduced rotation speed so as not to mechanically stress too much the sensors and the guiding/piloting electronics. 
     It is thus known, for example by patent EP905473, to provide an artillery shell carrying at its rear part a folding stabilizing tail assembly. 
     A rear sabot holds the fins of the tail assembly folded within the barrel of the weapon. It carries a sliding band which allows to communicate to the shell only a reduced rotation speed, in the order of a few tenths of revolutions per second (the usual rotation of a shell of 155 mm without sliding band is in the order of 300 revolutions/second). 
     When exiting the barrel, the sabot is ejected either by the effect of a propellant gas action within the tube, or by the effect of the aerodynamic flow applying thereto when exiting the barrel, the sabot could, for example, carry longitudinal weakened portions causing a cutout in a petal shape when exiting the weapon barrel and the sabot is ejected. 
     The projectile is thus aerostabilized during ballistic phase. 
     The stabilization in supersonic flight requires a static margin (distance between the aerodynamic center and the center of gravity) of the order of −1 caliber. The rear tail assembly further ensures a complementary rotation braking of the projectile. It potentially allows to control the residual rotation speed which can be imposed by the type of on-board sensors and the piloting algorithms. 
     When the projectile reaches the peak of its trajectory (which can be at an altitude higher than 10 km for long range firing), it initiates its descent to the area where potential targets are located. 
     Generally, piloting towards the target is ensured by canard controls provided at a front part of the projectile, as described by patent EP0905473. 
     One of the problems encountered is that the stabilization ensured by the tail assembly is not optimum for piloted steered flight and reduces the trajectory correction performances which are allowed by the canards. 
     Is also known by U.S. Pat. No. 8,894,004 a wing deployment mechanism for a projectile in which the wings are arranged in folded position with their planes parallel to the projectile axis. However, when these wings are in deployed position, they are oriented in a highly stabilizing manner, which still reduces the correction performances of the canards, if they are present. In fact, the wings described by this patent ensure themselves a trajectory correction function by having a capacity to pivot with respect to their main axis, perpendicular to the projectile axis. 
     The invention aims to provide an artillery projectile architecture in which the aerodynamic stabilization ensured by the tail assembly in ballistic phase does not reduce the performances of the piloting means in piloted phase. 
     According to a particular embodiment, a same tilt wing system can besides ensure the aerodynamic stabilization in ballistic phase by generating a stabilizing longitudinal moment (static margin of the order of −1 cal) and can also ensure the maneuverability in piloted phase (by generating lift with a static margin of the order of −0.25 cal). 
     The invention can thus decorrelate the static stability and the lift depending on the flight regimes. 
     The invention thus allows to optimize the definition of the piloting module, particularly the sizes and the selection of components such as the engines, hence the cost of the projectile. 
     The invention thus relates to an artillery projectile intended to have a trajectory comprising a ballistic phase and a piloted phase, the projectile having at least one means ensuring its aerodynamic stabilization on part or all of its trajectory and a means intended to ensure a piloting during the piloted phase, the projectile being characterized in that the aerodynamic stabilization means comprises a wing system having at least two wings which are able to be positioned with respect to the axis of the projectile, at least during the piloted phase, with their sweepback angles being negative, that is, with the free ends of the wings being oriented towards the front of the projectile. 
     According to a first embodiment, the wings of the wing system could deploy during a first part of the ballistic trajectory so as to have positive sweepback angles, a maneuvering means being provided for allowing to change the sweepback angle of the wings and to make it have negative values during a second part of the ballistic trajectory. 
     Each wing could be connected to a housing with respect to which it is mounted in a tilting manner via a wing support, the wing being connected to the support by a rod having means allowing it to pivot with respect to the wing support during the tilting movement of the support with respect to the housing, the wing thus switching from a folded position, in which it is positioned along the projectile with the plane of the wing applied along an outer wall of the projectile, to a deployed position in which the plane of the wing is radially oriented with respect to the projectile, each housing further being pivotably mounted with respect to the projectile body and the maneuvering means allowing to pivot all the housings carrying the wings so as to change simultaneously the sweepback angle of all the wings. 
     The maneuvering means could have a piston having the same axis as the projectile axis, the piston will comprise a rear face which will bear against a lower face of the housings, the piston being able to translate by the action of a motor means, the translation of the piston causing all the housings to pivot simultaneously. 
     Advantageously, the piston could assume a final position at the end of the translation, in which it ensures a locking of all the housings in the position with a negative sweepback angle. 
     The housings of the wings and the maneuvering means could be accommodated within a rear base integral with the projectile body. 
     The projectile could comprise a sabot surrounding the base and covering the wings in their folded position, the sabot carrying a sliding band and being ejected after firing. Each wing could be engaged in a notch of the projectile body when it is in its final position with a negative sweepback angle. 
     According to another embodiment of the invention, the aerodynamic stabilization means could also have a folding tail assembly which will be provided at a rear part of the projectile, the tail assembly being deployed during the ballistic phase. 
     According to a particular embodiment, the tail assembly could be attached to the projectile by a releasable connecting means, the tail assembly being ejected before opening the wing system with negative sweepback angles. 
     The invention will be better understood upon reading the following description of different embodiments, description made with reference to the appended drawings in which: 
    
    
     
         FIG. 1  is an external view of a projectile according to a first embodiment of the invention, the projectile being shown before firing; 
         FIG. 2  is a schematic longitudinal sectional view of the projectile according to this first embodiment of the invention; 
         FIG. 3  is an external and perspective view of the projectile according to the first embodiment during its ballistic phase; 
         FIG. 4  is an external and perspective view of the projectile according to the first embodiment during its piloted phase; 
         FIG. 5 a    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown before the opening of the wings of the wing system; 
         FIG. 5 b    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown with the wings being in the position they occupy during the ballistic phase, hence with the sweepback angles being positive; 
         FIG. 5 c    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown during the beginning of the movement of the maneuvering means; 
         FIG. 5 d    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown during a first intermediary phase of the movement of the maneuvering means; 
         FIG. 5 e    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown during a second intermediary phase of the movement of the maneuvering means; 
         FIG. 5 f    is a partial cross-sectional view of the rear part of this first embodiment, the projectile being shown with the wings in the locked position they occupy during the piloted phase, hence with the sweepback angles being negative; 
         FIGS. 6 a  and 6 b    show a wing and its housing in partial perspective and in an insulated manner,  FIG. 6 a    showing the wing in its folded position and  FIG. 6 b    showing the wing at the beginning of its opening movement; 
         FIGS. 7 a , 7 b , 7 c , 7 d , 7 e  and 7 f    show a partial rear perspective of the projectile,  FIG. 7 a    showing the wings in folded position and  FIG. 7 f    showing the wings in ballistic position, hence with the sweepback angles being positive, the other figures showing intermediary phases of the opening movement of the wings; 
         FIG. 8  is an external view of a projectile according to a second embodiment of the invention, the projectile being shown before firing; 
         FIG. 9  is an external and perspective view of this projectile during its ballistic phase; 
         FIG. 10  is an external and perspective view of this projectile during its piloted phase; 
         FIG. 11  is an external view of a projectile according to a third embodiment during its piloted phase. 
     
    
    
     If referring to  FIGS. 1 and 2 , an artillery projectile  1  according to a first embodiment of the invention comprises a body  2  carrying a fuze  3  provided with target sensors  4  (for example, infrared sensors) evenly and angularly distributed. A single axial sensor could also be provided, with a field sufficient to detect and track a target. The projectile could have, for example, a caliber of 155 mm. 
     The body  2  has a front portion  2   a  and a rear portion  2   b.    
     The rear portion  2   b  encloses an explosive charge  8  and its priming relay  10 . 
     The front portion  2   a  encloses a guiding/piloting electronics  5  (which could comprise a satellite positioning device or GPS), a safety and arming device  6  for the explosive charge  8 , and a piloting means  7  for piloting the projectile. The piloting means  7  here consists in four canard controls  9  which are deployable on the trajectory. The controls  9  will be deployed using a mechanism (not shown) of a known type, for example, that described in patent FR2949848. The deployment of the controls  9  will be controlled at a given time on the trajectory by the guiding/piloting electronics. Motor-reduction units will control the pivoting of the canard controls (or of a plane of canard controls) after deployment in order to allow the piloting. 
     The rear portion  2   b  of the projectile is covered by a sabot  11  which is a composite or metal part comprising a tubular portion  11   a  closed by a bottom  11   b . The sabot  11  carries, at its rear portion, a sliding band  12  which is intended to ensure the tightness to propellant gases when firing the projectile in an artillery barrel. 
     In a conventional manner, described in patent EP905473, the sliding band allows to communicate to the projectile only a part of the rotation induced by the grooves of the weapon barrel. The rotation speed of the projectile when exiting the weapon barrel is thus of the order of a few tenths of revolutions per second (the usual rotation of a shell of 155 mm without sliding band is of the order of 300 revolutions/second). 
     As more particularly seen in  FIG. 2 , the projectile  1  carries, at its rear portion, a rear base  13  which carries housings  14  each connected to a wing  16  and a means  15  for maneuvering these wing housings  14 . 
     The projectile further carries an aerodynamic stabilization means which, according to this first embodiment, consists in a wing system comprising at least two wings  16 . Here, the projectile  1  has six wings  16  evenly and angularly distributed. 
     According to the configuration of the ballistic phase shown in  FIG. 2 , the wings  16  are folded along the projectile  1  with the plane of each wing  16  being applied along an outer wall of the projectile  1 , at the rear portion  2   b.    
     Thus, the sabot  11  also covers the wings  16  during the inner ballistic phase (in the weapon barrel) and ensures their protection against the effect of the propellant gases and the shocks of the barrel depending on the tossing around of the projectile. 
       FIG. 5 a    more precisely shows the rear base  13 , with the sabot  11  being removed. In this figure, the wings  16  are in the position they occupy before opening. Each wing  16  is applied against an outer wall  17  of the projectile  1 . The wall will have a planar profile or a profile corresponding to that of the aerodynamic profile of the wing, thereby allowing the wing  16  to be received. 
     In this  FIG. 5 a   , two wings  16  are visible. 
     Each wing  16  is connected to a housing  14  with respect to which it is pivotably mounted via a wing support  18 . 
     A pivot  19  allows the support  18  of the wing  16  to tilt with respect to the housing  14 . 
     The wing is further connected to the support  18  by a rod  20  comprising means allowing it to pivot with respect to the wing support  18  during the tilting movement of the support  18  with respect to the housing  14 . 
     Such an architecture allowing the wing to pivot around its rod  20  during the opening of the wing is described in detail by patent EP1524488 to which reference can be made for more details. 
     If referring more particularly to  FIGS. 6 a  and 6 b   , a wing  16  can be seen insulated and attached to its housing  14  by the support  18 . It can be noted that the housing  14  has lateral trunnions  14   a  and  14   b  which will allow the housing  14  to be pivotably mounted with respect to the rear base  13 . These trunnions will be accommodated in bearings of the base (not shown). 
     The means allowing the rod  20  to pivot with respect to the support  18  particularly comprise a lateral arm  21  integral with the end of the rod  20  (arm visible in  FIGS. 6 a  and 6 b    and also  FIG. 5 b   ). The arm cooperates with a cam profile  22  carried by the housing  14  ( FIGS. 5 a  and 6 a   ). 
     Thus, during the opening of the wing  16  by the effect of the received aerodynamic loads and of the offset between the point of application of the aerodynamic force and the pivot  19 , the support  18  tilts with respect to the housing  14  on its pivot  19  (the geometrical axis of the pivot  19  is identified in  FIGS. 6 a  and 6 b   ). When tilting, the arm  21  will be driven by the cam profile  22  and cause the wing  16  to pivot with respect to its support  18 . The plane of the wing  16  will pivot by 90° and be positioned in the direction of the aerodynamic flow ( FIG. 5 b   ). 
       FIGS. 7 a -7 f    allow to see different steps of the pivoting of the wing  16 .  FIG. 7 a    shows (as in  FIG. 5 a   ) the different wings positioned along the outer wall  17  of the projectile. 
       FIG. 7 b    shows the beginning of the opening of the wings  16 . The pivoting of the supports  18  applies the arms  21  of each wing against the cam profile  22 . 
     Each wing then pivots with respect to its support  18  along the axis of its rod  20 .  FIGS. 7 c  and 7 d    show two steps for such pivoting of the wing. 
       FIG. 7 e    shows the wing at the end of its pivoting. It then has its plane in the direction of the aerodynamic flow, and the trailing edge of the wing  16  is oriented towards a radial slot  24  provided in the base  13 . 
     When the wing  16  is pivoted, it is locked with respect to its support  18 , for example by bracing of a spring blade (not shown), perpendicular to the plane of the wing  16 , and integral with the housing  14  (such a solution is described in patent EP1798513). 
       FIGS. 5 b  and 7 f    show the rear portion of the projectile when the wings  16  are in the position they occupy during the ballistic phase. It can be seen that, in this position, the wings  16  abut against a rear seating  23  of the base  13 . Each wing is accommodated in a radial slot  24  of the rear seating  13 .  FIGS. 3 and 4  allow to see the rear base  13  with its radial slots  24 . 
     Furthermore, the different housings  14  carrying the wings  16  are pivotably mounted with respect to the rear base  13  by using the trunnions  14   a ,  14   b.    
     As can be seen in  FIG. 5 a   , the rear base  13  encloses a maneuvering means  15  which allows to pivot all the housings  14  carrying the wings  16  so as to change simultaneously the sweepback angle of all the wings  16 . 
     The maneuvering means  15  comprises a piston  25  having the same axis as the axis  26  of the projectile. This piston  25  has a rear face which bears against a lower face  14   a  of the housings  14 . The maneuvering means  15  also has a motor means which can translate the piston  25  via a rod  28  (for example, by a worm screw connection). 
     As the piston  25  is simultaneously in contact with all the housings  14 , the translation of the piston  25  causes all the housings  14 , thus all the wings  16 , to pivot simultaneously. 
     Thus,  FIG. 5 b    shows the rear portion of the projectile when the wings  16  are in their deployed position with a positive sweepback angle α. The sweepback angle is the angle between the leading edge  16   a  of the wing  16  and a plane  29  perpendicular to the axis  26  of the projectile. 
     The positive sweepback angle α is around 60°.  FIG. 3  shows the projectile  1  in this flight configuration which is that corresponding to the ballistic phase. 
     When controlling the motor means  27 , the piston  25  causes all the housings  14  to pivot simultaneously.  FIG. 5 c    thus shows the beginning of the translation movement of the piston  25 , thus of the pivoting of the housings  14  and the associated wings  16 . 
       FIG. 5 d    shows a first intermediary phase of the translation movement of the piston  25 , phase during which the sweepback angles of the wings  16  are zero (wings  16  perpendicular to the axis  26  of the projectile). 
       FIG. 5 e    shows a second intermediary phase of the translation movement of the piston  25 . This phase corresponds to a position of the wings  16  with a sweepback angle θ which is negative, that is, with the free ends  16   b  (see  FIG. 4 ) of the wings  16  being all oriented towards the front of the projectile  1 . 
     Each wing  16  is then engaged in a notch  30  of the projectile body  1 . The notches  30  allow to block the root of each wing  16 . The value of the sweepback angle θ is approximatively −30°. 
     Finally,  FIG. 5 f    shows the final position of the piston  25 . The sweepback angle of the wings  16  has not been changed between  FIG. 5 e    and  FIG. 5 f   , but the piston  25  has continued its stroke and is in a final position at the end of the translation, in which it ensures a blockage of all the housings  14  in the position with a negative sweepback angle θ. 
     To ensure this blockage, the cylindrical peripheral edge of the piston  25  cooperates with the lower face  14   a  of each housing  14 . The piston  25  is, in the final position, arranged at a distance D from the pivot axis of each housing  14  and prevents the wings from returning in a position with a positive sweepback angle. 
     The rigidity of the final position is ensured, each fin being engaged in a notch  30  and blocked by the piston  25 . The operation of the projectile according to the invention is the following. 
     When firing the projectile, the sliding band  12  allows to limit the rotation speed of the projectile to a few tenths of revolutions per second (while the rotation speed of a projectile of 155 mm is higher than 300 revolutions per second for long range firings). 
     The sabot  11  which ensures both the acceleration of the projectile  1  and the tightness to propellant gases separates naturally from the projectile  1  when exiting the weapon barrel, by the action of the aerodynamic forces. 
     As an alternative, an assistance to the separation could be performed, for example, by a propellant gas action or a spring mechanism arranged between the base  13  and the sabot  11 . Patent EP905473 describes such modes of separation by gas action. 
     Once the sabot  11  is ejected, the wings  16  deploy naturally under the action of the centrifugation of the wings and of the dynamics of the projectile when exiting the barrel. 
     When each wing  16  rises against the flow by an aerodynamic effect, it immediately pivots with respect to its housing  14  with its wing support  18  limiting the tilting speed of the wing, and thus the impact at the end of the opening. A heavy wing indeed limits the impact intensity by inertia effect. The mechanism formed by the rod  20  and its arm  21  cooperating with the profiles  22  provided on the housing  14  causes the wing  16  to pivot and to be positioned in the wind&#39;s path, wherein the plane of the wing  16  is radial with respect to the projectile and thus passes through the axis  26  of the projectile. 
     The wings all assume the position shown in  FIGS. 3 and 5   b , position in which they are rearwardly abutting against the rear seatings  23  of the radial slots  24 . Each wing  16  is further locked with respect to its housing  14  by a suitable blocking device, for example the one described by patent EP1798513 (blockage by bracing of a spring blade). 
     The positive sweepback angle of about 60° minimizes the drag in supersonic flight while ensuring a sufficient static margin (of the order of −1 caliber), thereby guaranteeing the stability of the projectile when exiting the barrel, during the most critical flight phase (high-Mach supersonic flight). When the speed decreases, the static margin increases. 
     Once the wings  16  are deployed, the projectile  1  is in its ballistic flight phase. It can climb at an altitude higher than 1000 m with significant propelling charges and a minimum aerodynamic drag configuration. Besides, the wings  16  reduce the rotation speed of the projectile  1 . 
     After a period of time, for example, programmed at a computer of the guiding electronics  5  or programmed in a specific electronic module accommodated within the base, the maneuvering means  15  is controlled for changing the sweepback angle of the wings  16 . This control preferably occurs at the peak of the trajectory, when the projectile initiates its descent to reach the highest ranges. 
     The maneuvering means  15  allows to tilt the wings  16  towards the front of the projectile  1 . The angular amplitude of the tilting is of the order of 90° (the wings switching from +60° to)−30°. 
     The motor means  27  of the maneuvering means  15  could be electrical or pyrotechnic (retractor, lock, cylinder . . . ). The tilting could be performed within a few seconds, as the stability of the projectile during this transitional phase will always be ensured (subsonic flight). 
     Furthermore, the power required to this maneuvering is reduced due to the low air density and the minimum drag of the wings. 
     When the wings  16  have their free end  16   b  oriented towards the front of the projectile (negative sweepback angle), the canard controls  9  are also deployed and operational ( FIG. 4 ). The change of the sweepback angle of the wings  16  was controlled at the vicinity of the peak of the trajectory of the projectile  1 . 
     Due to the negative sweepback angle of the wings, the aerodynamic stability of the projectile  1  is reduced (static margin lower than −0.5 caliber). 
     The optimum value to be selected for the static margin depends on the performances of the projectile flight control chain and the flight goals. 
     With the invention, it is possible to adjust the static margin to the profile of the mission considered. For very-long range firing, strong emphasis will be put on the maneuverability in terminal phase. For short range firing, it will be possible to hold the wings in ballistic position (positive sweepback angle position), and not to control their switch to the front position (negative sweepback angle). The maneuverability will thus be reduced with a projectile which has a very high static stability, but this can be acceptable for a short range firing. 
     The static margin with a negative sweepback position is selected to be just sufficient to ensure the aerostabilization of the projectile, whether the canards  9  are deployed or not. 
     The canard controls  9  will allow to pilot the projectile by changing its incidence. The wings  16  with a negative sweepback angle ensure a high lift and will allow a high maneuverability due to their good aerodynamic lift characteristics. 
     The projectile according to the invention thus allows to ensure both the stability in supersonic ballistic flight and the capacities of important maneuvers in terminal piloting phase in subsonic flight. 
       FIGS. 8 to 10  show a projectile according to a second embodiment of the invention. 
     This embodiment is here shown in a very schematic manner. 
     As in the previous embodiment, the projectile  1  comprises a body  2  carrying a fuze  3  provided with target sensors  4  (for example, infrared sensors) evenly and angularly distributed, or comprising a single axial sensor with a field sufficient to detect and follow a target. The guiding/piloting electronics could also have a satellite positioning device or GPS. The body  2  has a front portion  2   a  and a rear portion  2   b.    
     The rear portion  2   b  encloses an explosive charge and its priming relay (not visible in the figures) and the front portion  2   a  encloses a guiding/piloting electronics, a safing and arming device for the explosive charge, and a piloting means  7  for piloting the projectile. 
     The piloting means  7  here consists in four canard controls  9  which are deployable on the trajectory. 
     The rear portion  2   b  of the projectile is partially covered by a sabot  11  which is a composite or metal part comprising a tubular portion  11   a  closed by a bottom  11   b . The sabot  11  carries, at its rear portion, a sliding band  12  which is intended to ensure the tightness to propellant gases when firing the projectile in an artillery barrel. 
     This projectile  1  differs from the one described above in that the aerodynamic stabilization means comprises:
         on one hand, a wing system formed by wings  16  which are during the ballistic phase in folded position, arranged with the plane of each wing  16  being applied along an outer wall of the projectile  1 , at the rear portion  2   b;      on the other hand, a folding tail assembly  31  which is arranged at a base  34  integral with the rear portion  2   b  of the projectile, rearwardly of the wing system  16 .       

     The tail assembly  31  here consists in fins  32  constituted by steel plates which are, for example, embedded or hinged at their root to the base  34  and lockable in deployed position. These fins  32  are at the beginning elastically winded on a cylindrical portion  33  of the base  34  and held in position by the sabot  11 . 
     The sabot  11  could be ejected after firing, either by the effect of propellant gas action within the barrel, or by the effect of aerodynamic flow applied thereto when exiting the barrel. The sabot could, for example, carry longitudinal weakened portions causing a cutout in a petal shape when exiting the weapon barrel and the sabot is ejected. 
     The ejection of the sabot  11  when exiting the weapon barrel causes the deployment of the fins  32  which ensure the stabilization of the projectile during its entire ballistic phase, as well as its rotation braking. 
     Contrary to the previous embodiment, during this ballistic phase, the wings  16  of the wing system remain in folded position ( FIG. 9 ). 
     The wings  16  are held in folded position, for example, by locks  35  which are integral with the body  2  of the projectile and which engage in holes in the ends of the wings  16 . 
     Furthermore, the base  34  is made integral with the rear portion  2   b  of the projectile body by a pyrotechnic bolt  36 . 
     At the vicinity of the peak of the trajectory, after a period of time which, for example, will be programmed at a computer of the guiding electronics, the pyrotechnic bolt  36  is controlled for causing the separation of the base  34  and the body  2  of the projectile. Furthermore, the locks  35  are controlled so as to release the wings  16 . 
     Each wing  16  is connected to the body  2  of the projectile by a connection of the type described above with reference to  FIG. 5 a    and also described by patent EP1524488. 
     This connection is not drawn in detail. It comprises, as previously described, a housing integral with the body  2  and with respect to which pivots a wing support receiving a rod integral with the wing, which itself can rotate with respect to the support and carries a lateral arm cooperating with a cam profile of the housing. 
     This connection allows the wing to pivot around its rod when opening the wing, thereby allowing to switch from a position in which the plane of the wing bears against the projectile body ( FIG. 9 ) to a position in which the plane of the wing  16  has pivoted by 90° and is positioned in the direction of the aerodynamic flow ( FIG. 10 ), the wing  16  having its leading edge  16   a  in the aerodynamic flow. 
     The cam profiles of the housing will be sized by the one skilled in the art so as to ensure a rotation of the wing with a final position such as shown in  FIG. 10 , with a negative sweepback angle θ, that is, with the free ends  16   b  of the wings being oriented towards the front of the projectile. A rear stop will be positioned so as to ensure that the wings keep this negative sweepback angle. 
     Meanwhile, the canard controls  9  are deployed and operational. 
     Due to the negative sweepback angle of the wings  16 , the aerodynamic stability of the projectile  1  is reduced (static margin lower than −0.5 caliber). This margin is selected to be just sufficient to ensure the aerostabilization of the projectile, whether the canard controls  9  are deployed or not. 
     This embodiment allows to eliminate the transition phase of the wings  16  from a positive sweepback angle to a negative sweepback. 
     The means ensuring the stabilization in ballistic phase and in piloted phase are then distinct and the movement for deploying the wings  16  has also a reduced amplitude. 
     Various alternatives of this embodiment are possible. 
     For example, the fins  32  could be connected to the base  34  by longitudinal grooves which will open onto the rear of the base. Each fin  32  will then be designed to slide axially in the corresponding groove. 
     A stop will be provided at the rear portion of the base  34 . Moving aside the stop will allow the fins  32  to be axially ejected by sliding in the corresponding groove under the effect of the aerodynamic resistance. 
     This ejection of the fins could then occur without requiring that the entire base  34  be ejected. Such an alternative allows to preserve substantially the same length for the projectile  1  during the ballistic and piloted phases. 
     As an alternative, in this last embodiment, wings  16  the plane of which remains positioned radially to the projectile and which pivot each around an axis perpendicular to the axis  26  of the projectile could be implemented. This embodiment requires, however, to have radial grooves in the body  2  of the projectile  1  and wings  16  which then enters into the body  2 . The capacities of the projectile to carry explosives will then be reduced. 
       FIG. 11  shows another embodiment of the projectile according to the invention which differs from the previous embodiment in that the tail assembly  31  is not ejected at the vicinity of the peak of the trajectory. 
       FIG. 11  shows the projectile during its piloted flight phase. The canard controls  9  are deployed as well as the wings  16  which have a negative sweepback angle. The rear fins  32  are still constituted by steel plates embedded or hinged to the base  34 . They remain integral with the projectile during this piloted phase. This embodiment increases a little the aerodynamic drag of the projectile, but could be satisfactory in some configurations.