IL185597A - Shell replaceable aft module - Google Patents

Description

185597/2 Shell Kit Israel Aerospace Industries Ltd. iwo¾<» iv iNfi n»¾»yjin The Inventors: :0>N>i»3ttn Menachem CHAIMOVITCH Pavel BRUK pra tno Ralph WERNER Hannan Gilo Moshe Tsabari C. 176141 Shell Kit Israel Aerospace Industries Ltd. t»Niv)>!7 fl> i fi n»\yynn The Inventors: : tJ>N».

Fin-stabilized shells are also known, for example as disclosed in US 2001/0030260, and some do not require to be fired from a rifled weapons barrel. On the other hand, some types of fin stabilized shells are initially spin stabilized at the firing phase, to be subsequently stabilized by means of deployable fins, once the spin has been reduced at some point in the trajectory. For example, terminally guided shells can be controlled via thrusters, controllable fins, or drag inducing arrangements to provide trajectory correction. Some such shells are also provided with base bleeding, for example as disclosed in the following patents US 6,779,754 discloses a long-range artillery shell that is fin-stabilized in its trajectory and which is designed to be fired in a rifled gun barrel, and has a so-called base-bleed unit with a number of stabilization fins that are deployable after the shell has left the barrel. The fins, when activated, are radially displaceable to project outside the external periphery of the shell through slots or through-holes in the wall of the shell, but are initially radially retracted inside the propellant motor section or propellant chamber of the base-bleed unit between dedicated protective walls that isolate the fins from the surrounding propelling charges of the propellant motor and also divide the inside of the propellant motor into sectors that are separated from each other. 01761410\6-03 - 2 - US 6,886,775 discloses a fm-stabilized artillery shell comprising a body part which can be axially displaced rearwards, in the direction of flight of the shell, once the latter has left the barrel from which it has been fired, and which in the original position is fully retracted in the shell, and in which a number of deployable fins are in turn secured, and from which the fins are automatically deployed as soon as the body part has reached its rear position in which it is locked relative to the rest of the shell.

US 6,695,252 discloses a missile or projectile tail section that includes an outflow device and a number of deployable fins. The outflow device may be a base bleed device that includes a slow-buming propellant which fills the vacuum created by the projectile's motion through the air. The fins are stowed canted relative to planes that include the axis of the tail section.

US 4,546,940 discloses a projectile adapted to be given a rotation on being fired which makes the projectile spin-stabil ized. The projectile is provided with stabi l izing fins which are extended at a desired point in the trajectory of the projectile and brake the rotation of the projecti le. The fi ns are held in the retracted position, in an embodiment shown, by covering plates which are held in place by a so-cal led base bleed unit. A delay device is adapted to be separated from the projectile at the desired point in the trajectory, so that the covering plates are removed and expose the fins, as a result of wh ich these can be extended.

US 6,352,218 discloses a method and a device designed for use with such shells that are equipped with a base-bleed unit for extended range and which during the first phase of their trajectory are spin-stabilized but which in the subsequent phase are subjected to spin deceleration by fins that deploy from the shell body and take over the stabilizing function. More exactly a method and device are disclosed that enables the said shells to achieve an effective and functional deployment of the fins at the desired point in time with simultaneous ejection of the base-bleed unit which at this point in time either no longer performs any useful function since it is burnt-out and solely constitutes a dead-weight or its function is no longer required. The basic idea behind the invention is that the base-bleed unit and the fin protector that initially surrounds the fins shall be permanently integrated with each other and thereby can be removed/ejected as a single unit. 01761410X6-03 - 3 - While a spin-stabilized shell usually provides greater accuracy and has less air resistance than an equivalent fin-stabilized shell, it is known that correcting the trajectory of a spinning shell is more demanding than that of a fin stabilized shell SUMMARY OF THE INVENTION The present invention relates to a conversion kit for a shell, the shell originally designed for being equipped with a base bleed module or the like, comprising a casing comprising a plurality of stabilizing fins and adapted for enabling said fins to be deployed from a stowed configuration accommodated within the casing, to a deployed configuration wherein at least a portion of the fins are radially projecting from the casing; a deployment arrangement for selectively deploying said fins to said deployed configuration; said kit being configured for being equipped to said shell in a manner corresponding to that employed for equipping said base bleed module or the like to said shell.

By "equipped" is meant to include any suitable manner/configuration/system and so on for associating the base bleed module or the like, or the kit, with the shell, such as to provide an integrated shell comprising the base bleed module or the like, or the kit, said integrated shell being capable of being fired as a unit from a suitable weapon. Thus, "equipped" may include affixing, mounting, joining, adhering or any other suitable manner, which provides the aforesaid integrated shell.

In one embodiment, the shell comprises a base bleed module attachment arrangement for enabling the shell to be equipped with the base bleed module or the like, the attachment arrangement comprising an externally threaded cylindrical projection, inwardly displaced radially from the shell casing at the aft end thereof, and defining a shell mating face, and wherein said casing comprises a kit mating face, substantially complementary to the shell mating surface, the casing further comprising an internally threaded surface complementary to the externally threaded cylindrical projection. 01761410\6-03 - 4 - The casing may comprise a generally cylindrical housing having a base wall, having a plurality of circumferentially spaced casing slots corresponding to said plurality of fins, said fins being deployably accommodated within said slots. For example, said fin may comprise a shaped slot therethrough and is slidingly and pivotably mounted with respect to the corresponding casing slot via a fixed pin received in said shaped slot, such that translation of the fin in an aft direction with respect to the casing also rotates the fin in a radially outward direction to enable deployment of the fin to said deployed configuration. The deployment arrangement may comprise a piston arrangement including a fin engagement element and a selectively operable driving device for selectively providing aft displacement of said fin engagement element with respect to said casing, whereby to translate said fins in said aft direction. Optionally, the driving device is a pyrotechnic device actuable via a control unit according to present conditions. Said conditions may include a predetermined time period after a shell comprising said kit is fired, and/or may include an acceleration or velocity of a shell comprising said kit is within a predetermined threshold after the shell is fired.

In some embodiments, the kit may further comprise a control system for computing trajectory corrections. The control system may optionally comprise a suitable sensor system for determining, in real time or close thereto, the trajectory of said shell when equipped with said kit, including, for example, any one of a GPS device or other satellite based systems, INS platform based on MEMS, or the like. Optionally, the kit further comprises a suitable arrangement for carrying out said trajectory corrections. In one embodiment, said arrangement for carrying out said trajectory corrections comprises at least one of at least one fin, at least one tlmister and at least one drag inducing arrangement, configured to be controllable in a manner to provide steering in at least one degree of freedom.

The present invention is also directed to a shell, equipped with the kit according to any variation thereof, as defined herein. The shell may be configured to be fired from any one of a rifled or non-rifled weapons barrel.

The present invention is also directed to a method for converting a spin stabilized shell into a fin stabilized shell, comprising: (a) providing said shell, said shell being originally designed for being equipped with a base bleed module or the like; (b) providing a kit according to any variation thereof, as defined herein; and 01761410X6-03 - 5 - (c) equipping said shell with said kit in a manner corresponding to the manner in which said shell is designed to be equipped with the base bleed module or the like.

Optionally, said shell is previously equipped with said base bleed module, and further comprising the step of removing said base bleed module prior to step (a).

Further optionally, subsequent to step (c), said shell is fired from a rifled barrel providing spin stabilization to said shell, and further comprising the step of deploying the fins during trajectory of the fired shell to reduce the spin of the shell, said fins providing stability to the shell. Alternatively, subsequent to step (c), said shell is fired from a non-rifled barrel, and further comprising the step of deploying the fins during trajectory of the fired shell to provide stability to the shell.

The method may further optionally include the step of providing a trajectory correction to the shell during said trajectory.

A feature of at least some embodiments of the invention is that it enables an existing spin-stabilized shell design that is configured for being fitted with a base bleed module or unit to be retrofitted instead with a deployable fin unit, resulting in a fin-stabilized shell. Such a fin-stabilized shell may be fired from a non-rifled weapon barrel, which are generally cheaper and simpler than equivalent rifled barrels, and thus increases the versatility of the particular shell design, which can then be used with either type of barrel the shell being fitted with either a base bleed module or a deployable fin unit, as required. Such a shell, if designed with a fixed guide band may be modified to exclude the band altogether, or to replace the same with a rotating band (when the shell is nevertheless used with a rifled barrel) or to replace the same with a smooth band that will not induce any spinning when the shell is fired through a rifled or non-rifled barrel.

Alternatively, such a fin-stabilized shell may be fired from a rifled weapons barrel, so that it is initially spin-stabilized, and the fm unit is configured for deploying the fins at a particular point in the trajectory of the shell, for example once the velocity has been reduced to a relatively low supersonic Mach number, for example Mach number of about 1.30.

Another feature of at least some embodiments of the invention is that it enables an existing spin-stabilized shell design to be converted to a terminally guided shell configuration. The replacement of spin stabilization with fin stabilization facilitates trajectory control if the shell is further equipped with means including mechanisms, systems etc. that enable a change of the trajectory to be selectively effected. In one such 01761410X6-03 - 6 - example, the trajectory may be controlled via thrusters, controllable fins, drag inducing devices, and so on, which may optionally be included in the deployable fin unit that replaces the base bled unit of the basic shell design.

The ability to retrofit an existing shell to be fin-stabilized and controllable also enables such a retrofit shell to be developed to production standard much faster, and more cheaply, than shells having the same performance, but designed and developed independently of an existing shell design that incorporates a base bleed module.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal cross-sectional side view of a prior art shell comprising a base bleed module; Fig, la illustrates in greater detail the base bleed module and the manner in which the shell is equipped therewith.

Fig. 2 is a fragmented cross-sectional side view of a shell comprising a kit according to a first embodiment of the invention, with the fins in the retracted or stowed configuration.

Fig. 3 is a fragmented cross-sectional side view of a shell comprising a kit according to the embodiment of Fig. 2, with the fins in the deployed configuration.

Fig. 4 is a fragmented isometric top/aft view of a shell comprising a kit according to the embodiment of Fig. 2, with the fins in the retracted or stowed configuration.

Fig. 5 is a fragmented isometric top/aft view of a shell comprising a kit according to the embodiment of Fig. 2, with the fins in the deployed configuration.

DETAILED DESCRIPTION OF EMBODIMENTS Referring to Fig. 1, a typical prior art spin-stabilized shell 10, for example the M401 shell, manufactured by Israel Military Industries Ltd, Israel comprises an aerodynamically contoured shell casing 11, defining an enclosed volume accommodating an explosive charge or material 12 therein, including a hollow charge, a 01761410N6-03 - 7 - fuse 13 at the fore end thereof, and a base bleed module 20 mounted to the aft end of the casing 11. The casing 11 comprises a guide band 15 affixed thereto, configured for cooperating with the rifled bore of the weapon barrel to induce a spin on the shell 10 as it is propelled therethrough by means of the expanding gases generated as the propellant charge (not shown) is ignited. Referring particularly to Fig. la, the shell comprises an externally threaded cylindrical projection 18, inwardly displaced radially from the casing 11 at the aft end thereof, and an annular mating face 17. Optionally, a lug 19 may be provided at the fore tip of the shell.

The base bleed module 20 comprises a generally cylindrical casing 22 having a blunt aft end 24 comprising an exhaust port 25, and the casing 22 comprises a suitable gas generating mechanism 29 to provide, in operation, a desired base bleed via exhaust port 25. The casing 22 comprises a tubular portion 26 having an annular mating face 27, complementary to mating surface 17, the annular portion 26 comprising an internally threaded surface complementary to the externally threaded cylindrical projection 18. The shell 10 is configured for engaging the base bleed module 20 with the shell casing 11 by screwing the base bleed module 20 onto the projection 18 until the mating faces 17, 27 abut.

Referring to Figs. 2 to 5, a conversion kit according to a first embodiment of the invention, generally designated 100, comprises a generally cylindrical casing 110, including a tubular portion 112, a disc-shaped base wall 114 and an engagement portion 116, and further comprises a plurality of deployable stabilizing fins 120, typically identical to one another.

Engagement portion 160 is configured for enabling engagement of the casing 110 to the particular shell 190 that it is desired to have equipped with the kit 100, the shell 190 having been designed to be fitted with a base bleed module or the like. In the illustrated embodiment, the shell 190 is similar to shell 10 illustrated in Figs. 1 and la, and thus comprises an externally threaded cylindrical projection 118, inwardly displaced radially from the shell casing 111 at the aft end thereof, and an annular mating face 117. Tubular portion 112 comprises a mating face 127, complementary to mating surface 117, the tubular portion 112 also comprising an internally threaded surface complementary to the externally threaded cylindrical projection 118.

Alternatively, the engagement portion may be adapted to the particular engagement arrangement that the shell is provided with for engagement to a base bleed 01761410X6-03 - 8 - module or the like, when this is different to that described above. For example, the shell may be configured for having the base bleed module or the like affixed thereto via a bayonet fit, adhesive, press fit and so on, and thus the engagement portion is similarly or complementarily configured.

In the illustrated embodiment, the kit comprises eight fins 120, but the skilled practitioner will appreciate that more than eight fins may be provided, for example 9, 10 11, 12 or more, or less than eight fins may be provided, for example 2, 3, 4, 5, 6 or 7, according to the particular requirements of the shell which is to be equipped with the kit 100.

Each fin 120 may be configured as a substantially flat plate, optionally further configured to comprise rounded edges, and/or an aerodynamically contoured cross-section. In any case, and referring to the retracted or stowed configuration illustrated in Figs. 2 and 4, in this embodiment each fin 120 comprises: a generally linear trailing edge 121 substantially parallel to the base wall 114; a generally linear fin root edge 122 that is longitudinally aligned with axis 199 when the fin 120 is in the retracted configuration; a generally linear fin outer edge 123 that is generally aligned with the outer surface of the tubular portion 112 when the fin is in the retracted configuration; and a leading edge 124 of the fin 120, which may be swept and linear as illustrated, or alternatively curved, for example. Each fin 120 further comprises a projection including cam 125 extending forward of the leading edge 124, the operation of which will be described herein. Cam 125 comprises a first cam surface 125a that is substantially aligned with a plane orthogonal to axis 199, and a second cam surface 125b set at an obtuse angle with respect thereto in an inward radial direction and aft longitudinal direction B. The cam 125 further comprises a third cam surface 125c substantially orthogonal to cam surface 125b in an inward radial direction and forward longitudinal direction.

In other embodiments, the fins may have any other suitable shape, as required for providing the required level of stabilization for the particular shell to which the kit is to be fitted, the fin shape enabling the same to be stowed within the casing, at least in a radial manner.

Each fin 120 further comprises a curved slot 126 extending through the thickness of the fin 120. The fin configuration of the illustrated embodiment maximizes fin area within the space constraints of the casing 110. 01761410\6-03 - 9 - The tubular portion 112 comprises a plurality of longitudinal slots 132, i.e., aligned with the longitudinal axis 199 of the casing 110, which is coaxial with the longitudinal axis 99 of the shell when affixed thereto. Each longitudinal slot 132 merges and is contiguous with a corresponding radial slot 134 provided in the base wall 114, to provide an L-shaped slot 130. Thus a plurality of contiguous slots 130 are provided, corresponding to the plurality of fins 120. Each slot 130 is dimensioned to enable a corresponding fin 120 to be passed therethrough to assume a deployed position, as illustrated in Figs. 3 and 5.

The casing 110 is provided with a transverse pin 135 radially displaced inwardly from the each slot 130, and each pin is received in the corresponding curved slot 126 comprised in the corresponding fin 120. Cooperation between the curved slot 126 and pin 135 allows the corresponding fin 120 to be rotated/translated along a radial/longitudinal plane with respect to the corresponding slot 130 in a predetermined manner, between the fully deployed position illustrated in Figs. 3 and 5, wherein at least a portion of each of the fins 120 are radially projecting from the casing, and the retracted or stowed position illustrated in Figs. 2 and 4. In particular, the particular shape of the curved slot 126 and the position of the corresponding pin 135 within the casing 110 are such that when the corresponding fin 120 is subjected to a longitudinal translation in the aft direction B (Fig. 2), the fin 120 is concurrently rotated in a radially outward direction Q.

The kit 100 further comprises a fin actuation mechanism for selectively deploying the fins to the deployed position from the stowed or retracted position. In the illustrated embodiment, the fin actuation mechanism is configured for deploying all the fins 120 substantially simultaneously, and is in the form of a piston arrangement 160, coaxially arranged with respect to axis 199, and comprising an inner piston rod 162 and an outer piston cylinder 164 adapted for axial translation with respect to the rod 162. A through aperture 119 is provided in the base wall 116, coaxial with axis 199, and sized to allow the cylinder 164 to axially pass therethrough with a radial clearance. The rod 162 comprises a longitudinal end base 165 that, when the kit 100 is engaged with the shell 190, is in abutting contact with a rear bulkhead 198 of the shell 190. An actuation disc 166 is comprised on the fore end of the cylinder 164, and comprises a substantially flat engagement surface 167, arranged substantially orthogonal to axis 199, and a cylindrical edge 168, substantially orthogonal to surface 167, and the engagement 01761410\6-03 - 10 - surface 167 is in contact with the cam 125 of each fin 120. In the retracted configuration shown in Figs. 2 and 4, disc 166 is in contact with the first cam surface 125a via engagement surface 167, while in the deployed configuration shown in Figs. 3 and 5, engagement surface 167 is in contact with the third cam surface 125c, the edge 168 being in simultaneous contact with the second cam surface 125b, locking the fins in position.

The piston arrangement 160 further comprises a driving element for axially displacing the cylinder 164 from the rod 162. In the illustrated embodiment, the driving element is in the form of a pyrotechnic device (not shown) accommodated between the rod 162 and cylinder 164, and operatively connected to a control unit (not shown). On receiving a suitable signal or command from the control unit, the pyrotechnic device is activated, and typically expanding gases generated by the device drive the cylinder 164 away from the rod 162 in an axial direction.

Alternatively, the driving element may be in the form of springs or any other configuration that enables the cylinder 164 to be selectively translated away from the rod 162 in an aft longitudinal direction B. In any case, it is to be noted that since the rod 162 is in abutting contact with bulkhead 198, any relative axial movement between the cylinder 164 and rod 162 will effectively result in the cylinder 164 moving along an aft direction B.

Optionally, and as illustrated for this embodiment, the surface area provided by each fin may be increased in a longitudinal manner such that, in the retracted configuration, the trailing edges 121 extend in aft direction B beyond the base wall 116. Accordingly, a temporary plug element 170 may be provided to house the fin portions 129 of the fins 120 that project beyond base wall 116, and thus maintain the cylindrical profile of the kit 100. Thus, plug element 170 comprises a generally cylindrical form, having a plurality of radial/longitudinal slots 172, corresponding to the plurality of slots 130 in casing 110, for housing the fin portions 129. The plug element 170 further comprises an axially arranged abutment element 175 that in the retracted configuration is in abutment with the aft free end 166 of cylinder 164.

Thus, a spin-stabilized shell 190 designed for use with a base bleed unit may be converted to a fin-stabilized shell, at least for a part of its trajectory, by providing kit 100. The shell 190 is fitted with kit 100 by engaging casing 110 to the shell 190 in a similar manner to that intended for the corresponding base bleed module, i.e., by 01761410\6-03 - 11 - screwing the casing 110 onto the projection 118 until the mating faces 117, 127 abut. Of course, if the shell 190 is already equipped with a base bleed module, this is removed prior to engaging casing 110 to shell 190.

In operation, the shell 190, equipped with kit 100, may be fired from a non-rifled weapons barrel and the control unit is configured for actuating the piston arrangement 160 at preset conditions, for example a particular time period after firing, as determined by means of a timer for example, or when the acceleration or velocity of the shell 190 has dropped to a threshold value, as determined by suitable accelerometers, pressure transducers, and so on, as in known in the art.

Alternatively, the shell 190, equipped with kit 100, may be fired from a rifled weapons barrel and exits the barrel in a spin stabilized condition. The control unit is configured for actuating the piston arrangement 160 at preset conditions, which may be similar to or different from those corresponding to a non-rifled weapon, for example, when the velocity of the shell falls to below a present threshold, for example about 1.3 Mach number. Deployment of the fins (see below) dramatically reduces spin and the shell is subsequently fin stabilized, though may still carry some spin. Deployment of the fins may optionally be carried out at any desired part of the trajectory.

Operation of the kit 100 is as follows. Following a suitable control signal or the like from the control unit, the piston arrangement 160 is actuated, and the expanding gases generated by the pyrotechnic device translates the piston cylinder 164 in an aft direction with respect to the rod 162, which is abutted to bulkhead 168. In doing so, the cylinder free end pushes against the abutment element 175 until the plug element 170 is completely separated and ejected from the casing 110. At the same time, as the cylinder 164 is moved in the aft direction, engagement surface 167 provides an aft translation to the fins 120 via contact with cam 125, which together with the contour of corresponding slot 126 and position of pin 136, result in the fins being translated in an aft direction and radially deployed to the deployed position, the fins being locked in place when the engagement surface 167 and edge 168 are respectively abutted against the third cam surface 125c and the second cam surface 125b.

Ejection of the plug element 170 reduces the weight of the shell and allows a greater range to be attained. Thus, a similar configuration of kit casing and ejectable plug element may be used for any desired axial length of the kit 100 for providing corresponding weight and range advantages. 01761410\6-03 - 12 - A second embodiment of the invention (not illustrated) comprises all the elements and features of the first embodiment, and thus provides a conversion kit for replacing the base bleed module or the like designed for a particular shell with a fin stabilized unit, and thus converting a spin-stabilized shell to a fin stabilized shell. In contrast to the first embodiment, at least some of the fins are actuatable in their deployed positions to enable the trajectory of the shell to be controlled, and a trajectory control system is also provided, operatively connected to the controllable fins. The trajectory control system may comprise any suitable sensor system , for determining, in real time or close thereto, the trajectory, i.e., the position and altitude of the shell, for example a GPS device or other satellite based systems, INS platform based on MEMS, and the like, and a computer for computing the trajectory required to place the shell within a predetermined radius of a predetermine target via trajectory corrections, and for controlling the fins to execute the required trajectory corrections.

In a variation of the second embodiment, additionally to or alternatively to the controllable fins, the kit may comprise at least one other fin, thrusters and/or drag inducing arrangements to provide the aforesaid trajectory correction, configured to be controllable in a manner to provide steering of the shell in at least one degree of freedom.

In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps.

Finally, it should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to".

While there has been shown and disclosed example embodiments in accordance with the invention, it will be appreciated that many changes may be made therein without departing from the spirit of the invention. 01761410\6-03

Claims (22)

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1. Conversion kit for a shell, the shell originally designed for being equipped with a base bleed module or the like, comprising a casing comprising a plurality of stabilizing fins and adapted for enabling said fins to be deployed from a stowed configuration accommodated within the casing, to a deployed configuration wherein at least a portion of the fins are radially projecting from the casing; a deployment arrangement for selectively deploying said fins to said deployed configuration; said kit being configured for being equipped to said shell in a manner corresponding to that employed for equipping said base bleed module or the like to said shell.

2. Kit according to claim 1, wherein the shell comprises a base bleed module attachment arrangement for enabling the shell to be equipped with the base bleed module or the like, the attachment arrangement comprising an externally threaded cylindrical projection, inwardly displaced radially from the shell casing at the aft end thereof, and defining a shell mating face, and wherein said casing comprises a kit mating face, substantially complementary to the shell mating surface, the casing further comprising an internally threaded surface complementary to the externally threaded cylindrical projection.

3. Kit according to claim 1 or claim 2, said casing comprising a generally cylindrical housing having a base wall, having a plurality of circumferentially spaced casing slots corresponding to said plurality of fins, said fins being deployably accommodated within said slots.

4. Kit according to claim 3, wherein each said fin comprises a shaped slot therethrough and is slidingly and pivotably mounted with respect to the corresponding casing slot via a fixed pin received in said shaped slot, such that translation of the fin in an aft direction with respect to the casing also rotates the fin in a radially outward direction to enable deployment of the fin to said deployed configuration.

5. Kit according to claim 4, wherein said deployment arrangement comprises a piston arrangement including a fin engagement element and a selectively operable 01761410\6-03 - 14 - driving device for selectively providing aft displacement of said fin engagement element with respect to said casing, whereby to translate said fins in said aft direction.

6. Kit according to claim 5, wherein said driving device is a pyrotechnic device actuable via a control unit according to present conditions.

7. Kit according to claim 6, wherein said conditions include a predetermined time period after a shell comprising said kit is fired or an acceleration or velocity of a shell comprising said kit is within a predetermined threshold after the shell is fired.

8. Kit according to any one of claims 1 to 7, further comprising a control system for computing trajectory corrections.

9. Kit according to claim 8, wherein said control system comprises a suitable sensor system for determining, in real time or close thereto, the trajectory of said shell when equipped with said kit

10. Kit according to claim 9, wherein said sensor system comprises a GPS device or other satellite based systems, INS platform based on MEMS, or the like.

11. Kit according to any one of claims 8 to 10, wherein said kit comprises a suitable arrangement for carrying out said trajectory corrections.

12. Kit according to claim 1 1, wherein said arrangement for carrying out said trajectory corrections comprises at least one of at least one fin, at least one thruster and at least one drag inducing arrangement, configured to be controllable in a manner to provide steering in at least one degree of freedom.

13. A shell, equipped with the kit as defined in any one of claims 1 to 12.

14. Shell according to claim 13, configured to be fired from any one of a rifled weapons barrel and non-rifled weapons barrel.

15. Method for converting a spin stabilized shell into a fin stabilized shell, comprising: (a) providing said shell, said shell being originally designed for being equipped with a base bleed module or the like; (b) providing a kit as defined in any one of claims 1 to 12; and (c) equipping said shell with said kit in a manner corresponding to the manner in which said shell is designed to be equipped with the base bleed module or the like. 01761410\6-03 - 15 -

16. Method according to claim 14, wherein said shell is previously equipped with said base bleed module, and further comprising the step of removing said base bleed module prior to step (a).

17. Method according to claim 15 or claim 16, wherein subsequent to step (c), said shell is fired from a rifled weapons barrel providing spin stabilization to said shell, and further comprising the step of deploying the fins during trajectory of the fired shell to reduce the spin of the shell, said fins providing stability to the shell.

18. Method according to claim 15 or claim 16, wherein subsequent to step (c), said shell is fired from a non-rifled weapons barrel, and further comprising the step of deploying the fins during trajectory of the fired shell to provide stability to the shell.

19. Method according to any one of claims 17 to 18, further comprising the step of providing a trajectory correction to the shell during said trajectory.

20. Conversion kit for converting a spin stabilized shell into a fin stabilized shell, said shell originally adapted for being equipped with a base bleed module or the like, substantially as herein described with reference to the appended drawings.

21. A fin stabilized shell, substantially as herein described with reference to the appended drawings.

22. Method for converting a spin stabilized shell into a fin stabilized shell, said shell originally adapted for being equipped with a base bleed module or the like, substantially as herein described with reference to the appended drawings. For the Applicants, REINHOLD COHN AND PARTNERS 01761410X6-03