Abstract:
A projectile (10) for firing from a barrel, said projectile including a multiplicity of barrel assemblies (12, 13, 14) radially disposed from the centre of mass of the projectile, wherein each of said multiplicity of barrel assemblies includes a plurality of sub-projectiles (16) axially disposed within a barrel; each of said sub-projectiles associated with a discrete propellent charge (17) for propelling a respective sub-projectile from the barrel, wherein said projectile is capable of selectively firing sub-projectiles (16), suitably with the aid of primers (18) each coupled to an electronic controller (15). to provide a predetermined pattern of deployed sub-projectiles. A defence system employing projectiles of the type described is also disclosed, together with a method for disguising the launch location of a projectile utilising divert propulsion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This present invention relates to the deployment of objects in the nature of projectiles and in particular, although not exclusively, to the formation of a predetermined pattern of deployed sub-projectiles by a parent projectile and to a projectile launching method for masking the launch location of a projectile.  
           [0003]    2. Discussion of the Background Art  
           [0004]    Projectiles that incorporate explosive charges have been used as fragmentation devices to deploy a plurality of fragments. In a simple form the casing of such a projectile fragments on detonation of the explosive charge such that individual fragments of the casing are deployed radially to form a fragmentation pattern roughly in the shape of the surface of a sphere.  
           [0005]    In other configurations, the shape of the charge and the configuration of the casing may be varied to control the fragmentation pattern. However, such fragmenting projectiles produce a relatively thin, shell like fragment casing pattern. It is desirable that the depth of the fragmentation be able to be increased or controlled.  
           [0006]    Such projectiles may be particularly suited to defending a designated area whilst avoiding rending the area dangerous after a threat situation has diminished, such as occurs with conventional minefields.  
           [0007]    Existing defences to attacks typically include systems for acquiring and monitoring the trajectory of objects, including flying objects such as rockets and missiles. Examples of trajectory acquisition and monitoring systems are described in U.S. Pat. No. 4,622,458 to Boeck et al and U.S. Pat. No. 5,960,097 to Pfeiffer et al.  
           [0008]    More recently, sophisticated defences to threats which include rounds launched at relatively high angles so as to be thrown or hurled at a target, such as characteristic of mortars, are capable of calculating the source of an attack by deriving the location of a projectile launching apparatus from the trajectory of the projectiles.  
         SUMMARY OF THE INVENTION  
       OBJECT OF THE INVENTION  
         [0009]    It is an object of certain embodiments of the invention to provide a projectile that may be used to deploy sub-projectiles in a predetermined pattern that addresses the problems of the prior art, by providing increased or controlled fragmentation, or at least provides a useful choice for defence purposes.  
           [0010]    It is a further object of certain embodiments of the invention to provide a defence system that has improved control over deployment of projectiles and does not render the defended area unsafe for later civilian use.  
           [0011]    It is an object of other embodiments of the invention to provide a defence system capable of masking the location of a projectile launching apparatus by diverting projectile in flight whereby the location of the projectile launching apparatus is unable, or at least more difficult, to derive.  
         DISCLOSURE OF THE INVENTION  
         [0012]    According to a first form of the present invention, there is provided a projectile including a multiplicity of barrel assemblies radially disposed from the centre of mass of the projectile, wherein each of said multiplicity of barrel assemblies includes a plurality of sub-projectiles axially disposed within a barrel, wherein each of said sub-projectiles are associated with a discrete propellent charges for propelling a respective sub-projectile from the barrel, and wherein said projectile is capable of selectively firing sub-projectiles to provide a predetermined pattern of deployed sub-projectiles.  
           [0013]    Preferably the projectiles of the present invention are particularly adapted for deployment by firing from the barrel of a gun, rather than self-propelled missiles or rockets that are launched from a tube or gantry. In other embodiments the projectiles of the invention may be deployed by dropping from a mobile platform, such as an aircraft or ship, utilising gravity for delivery or, alternatively, adapted for throwing by a soldier or protective services officer in a similar fashion to a conventional manually delivered grenade.  
           [0014]    The projectiles of the invention suited to firing from a barrel may, in a first aspect, be used for intercepting and destroying incoming missiles, particularly of the high altitude ballistic type. In a second aspect, the present invention provides a method of intercepting a missile including the steps of determining the path of the missile, firing a projectile of the type herein described into the path of said missile, and firing selected sub-projectiles to form a predetermined pattern of sub-projectiles in and adjacent to the determined path of the missile.  
           [0015]    The projectiles of the present invention may be used for vehicle self defence. A vehicle coming under attack, in particular from close range, may fire a projectile of the type herein described towards the attackers and deploy the sub-projectiles in a predetermined pattern amongst the attackers. In a third aspect, the present invention provides a self defence method for a vehicle from an attacking force including the steps of determining the location of the attacking force, firing a projectile of the type herein described adjacent to the determined location of the attacking force, and firing selected sub-projectiles to form a predetermined pattern of sub-projectiles in and adjacent to the determined location of the attacking force.  
           [0016]    The projectiles of the present invention may be used for repelling an infantry advance. In a fourth aspect, the present invention provides a method of repelling an infantry including the steps of determining the location of the infantry, firing at least one projectile of the type herein described adjacent to the determined location of the infantry, and- firing selected sub-projectiles to form a predetermined pattern of sub-projectiles in and adjacent to the determined location of the infantry.  
           [0017]    The projectiles of the present invention may be used for forming airborne images, such as fireworks. In a fifth aspect, the present invention provides a method of forming airborne images including the steps of firing a projectile of the type herein described into the air, and firing selected sub-projectiles including image forming matter to form a predetermined pattern of image forming matter in the air.  
           [0018]    The projectiles of the present invention may be used for fire fighting. In a sixth aspect, the present invention provides a method of fire fighting including the steps of determining the location of the fire, firing at least one projectile of the type herein described adjacent to the determined location of the fire, firing selected sub-projectiles to form a predetermined pattern of sub-projectiles in and adjacent to the determined location of the fire, and deploying from the fired sub-projectiles a fire retardant.  
           [0019]    The projectiles of the present invention may be used for generating a fuel-air explosion. In a seventh aspect, the present invention provides a method of generating a fuel-air explosion including the steps of selecting the desired location of the fuel-air explosion, firing at least one projectile of the type herein described adjacent to the desired location of the fuel-air explosion, firing selected sub-projectiles including a fuel to form a predetermined pattern of sub-projectiles, deploying the fuel from the fired sub-projectiles, firing selected sub-projectiles including detonators to form a predetermined pattern of sub-projectiles, detonating said detonators to generate a fuel-air explosion.  
           [0020]    The projectiles of the present invention may be used for deploying a variety of payloads. In a eighth aspect, the present invention provides a method of deploying a payload including the steps of selecting a desired location for the delivery of a payload, firing at least one projectile of the type herein described adjacent to the desired location of the payload, firing selected sub-projectiles including said payload to form a predetermined pattern of sub-projectiles, and deploying said payload from the fired sub-projectiles.  
           [0021]    The projectiles of the present invention may be used for defending a designated area. In a ninth aspect, the invention resides broadly in defence system for defending a designated area, said defence system including:  
           [0022]    at least one monitor for monitoring the designated area to detect any zone therein in which a new presence appears;  
           [0023]    defence means capable of debilitating personnel present anywhere in a remote designated area wherein said defence means includes a weapon capable of firing projectiles wherein the projectiles include an array of barrel assemblies disposed radially from the centre of mass of the projectile, each barrel assembly having a plurality of secondary or sub-projectiles axially disposed within a barrel, which sub-projectiles are associated with discrete propellant charges for propelling said sub-projectiles sequentially from the barrel, wherein said array of barrel assemblies is capable of selectively firing the sub-projectiles from selected barrels whereby said projectile may deploy a predetermined pattern of sub-projectiles; and  
           [0024]    communication means providing communication between the monitor and the defence for triggering selective activation of the defence for delivering a debilitating attack to the detected zone.  
           [0025]    The monitors include one or more on-site sensors deployed in the designated area or remote-sensing means deployed remote from the designated area. Alternatively the monitoring means may include both on-site and remote sensing means.  
           [0026]    The monitoring means may also provide a visual display of the monitored designated zone so that manual override means may be actuated, if desired, to enable manual control of the set defence means.  
           [0027]    A number of secondary or sub-projectiles can be fired simultaneously from a plurality of barrels or in quick succession from the one barrel. In such arrangements the electrical signal may be carried externally of the barrel or it may be carried through the superimposed secondary projectiles which may clip on to one another to continue the electrical circuit through the barrel, or abut in electrical contact with one another. The sub-projectiles may carry the control circuit or they may form a circuit with the barrel.  
           [0028]    The array of barrel assemblies may be arranged adjacent the leading end or the trailing end of the projectile for effecting changes in attitude of the projectile or medially for displacing laterally displacing the projectile. Alternatively the directional control system may include an array of barrel assemblies adjacent both leading and trailing ends of the projectile.  
           [0029]    The or each array of barrel assemblies may fire a sub-projectile in a direction having a longitudinal component in order to provide a consequent addition to the kinetic energy of the projectile or a component in a direction tangential to the longitudinal axis of the missile in order to impart or change projectile rotation about its longitudinal axis. The barrel assembly may fire secondary projectiles across flight surfaces such as a wing to induce a further steering effect to the projectile. Alternatively barrel assemblies may extend through the aerofoil surfaces so as to fire in both directions. This may add structural strength to the aerodynamic design.  
           [0030]    If desired, a separate array or opposing arrays of barrel assemblies may be provided to control projectile rotation about the longitudinal axis of the projectile. The configuration of the arrays may include opposing pairs of barrel assemblies that are fired simultaneously to effect changes in rotation about the longitudinal axis of the projectile only. The sub-projectiles may be selectively actuated before and/or after firing secondary projectiles form the directional control system to negate or utilise the effects on the projectile of such rotation about its longitudinal axis.  
           [0031]    In certain embodiments of the present invention energy required to change attitude and/or the flight direction of the parent projectile may be provided by the firing of sub-projectiles from one or more selected barrel assemblies.  
           [0032]    According to a second form of the present invention, there is provided a method of masking the launch location of a projectile launching apparatus is provided. The method includes the steps of discharging at least one projectile from a barrel assembly, said barrel assembly having a barrel, a plurality of projectiles axially disposed within the barrel for operative sealing engagement with the bore of the barrel, and discrete propellant charges for propelling respective projectiles sequentially through the muzzle of the barrel and, whilst said at least one projectile is in flight, firing at least one sub-projectile from an array of divert propulsion assemblies incorporated therein, each divert propulsion assembly having a plurality of sub-projectiles axially disposed within a divert propulsion barrel, which sub-projectiles are associated with secondary discrete propellant charges for propelling said sub-projectiles sequentially from the divert propulsion barrel, wherein said array of divert propulsion barrel assemblies is capable of selectively firing the sub-projectiles from selected divert propulsion barrels whereby said projectile is accelerated by the reactionary force generated by said firing of sub-projectiles.  
           [0033]    The overall shape of the sub-projectile is not narrowly critical as the sub-projectile is a mass against which the secondary propellant acts and exerts a reactionary force on the breech of the divert propulsion barrel. In the context of the present form of the invention, the breech may be formed by subsequent sub-projectiles remaining in the barrel in sealing engagement with the bore of the divert propulsion barrel. The reactionary force is transferred from the breech of the secondary or divert propulsion barrel to the projectile and results in an acceleration of the projectile.  
           [0034]    The array of barrel assemblies may be disposed radially from the centre of mass of the projectile. Such configurations of barrel assemblies are particularly suited to objects that do not incorporate an in flight propulsion system, ie. rockets and missiles. The firing of sub-projectiles simply displaces the projectile and the projectile continues upon its trajectory, save for the displacement, the apparent trajectory.  
           [0035]    The present invention has particular application to area denial systems wherein the area is subject to shelling by projectiles launched from a pod, such as a mortar box. It will of course be understood that the present invention also has application to disguising the firing location of other projectile launching or firing systems.  
           [0036]    In a preferred embodiment the apparent trajectory may be selected to draw fire from the launch apparatus to other enemy positions.  
           [0037]    The projectiles of the present invention advantageously employ barrel assemblies of the type described in International Patent Application Nos. PCT/AU94/00124 and PCT/AU96/00459. Such barrel assemblies include a barrel;  
           [0038]    a plurality of sub-projectiles axially disposed within the barrel for operative sealing engagement with the bore of the barrel, and discrete propellant charges for propelling respective sub-projectiles sequentially through the muzzle of the barrel.  
           [0039]    The sub-projectiles may be round, conventionally shaped or dart-like and the fins thereof may be off-set to generate a stabilising spin as the dart is propelled from a barrel which may be a smooth-bored barrel. If required, the projectiles carrying the sub-projectiles may be substantially cylindrical, ovoid or spherical in shape.  
           [0040]    The propellant charge may be form as a solid block to operatively space the sub-projectiles in the barrel or the propellant charge may be encased in metal or other rigid case which may include an embedded primer having external contact means adapted for contacting an pre-positioned electrical contact associated with the barrel. For example the primer could be provided with a sprung contact which may be retracted to enable insertion of the cased charge into the barrel and to spring out into a barrel aperture upon alignment with that aperture for operative contact with its mating barrel contact. If desired the outer case may be consumable or may chemically assist the propellant burn. Furthermore an assembly of stacked and bonded or separate cased charges and sub-projectiles may be provided for reloading a barrel.  
           [0041]    Each sub-projectile may include a head and extension means for at least partly defining a propellant space. The extension means may include a spacer assembly that extends rearwardly from the head and abuts an adjacent sub-projectiles assembly.  
           [0042]    The spacer assembly may extend through the propellant space and the head whereby compressive loads are transmitted directly through abutting adjacent spacer assemblies. In such configurations, the spacer assembly may add support to the extension means that may be a thin cylindrical rear portion of the head. Furthermore the extension means may form an operative sealing contact with the bore of the barrel to prevent burn leakage past the sub-projectile.  
           [0043]    The spacer assembly may include a rigid collar which extends outwardly to engage a thin cylindrical rear portion of a malleable head inoperative sealing contact with the bore of the barrel such that axially compressive loads are transmitted directly between spacer assemblies thereby avoiding deformation of the malleable head. Complementary wedging surfaces may be disposed on the spacer assembly and head respectively whereby the head is urged into engagement with the bore of the barrel in response to relative axial compression between the spacer means and the head. In such arrangement the head and spacer assembly may be loaded into the barrel and there after an axial displacement is caused to ensure good sealing between the sub-projectile and barrel. Suitably the extension means is urged into engagement with the bore of the barrel.  
           [0044]    The head may define a tapered aperture at its rearward end into which is received a complementary tapered spigot disposed on the leading end of the spacer assembly, wherein relative axial movement between the head and the complementary tapered spigot causes a radially expanding force to be applied to the sub-projectile.  
           [0045]    The barrel may be non-metallic and the bore of the barrel may include recesses that may fully or partly accommodate the ignition means. In this configuration the barrel houses electrical conductors that facilitate electrical communication between the control means and ignition means. This configuration may be utilised for disposable barrel assemblies that have a limited firing life and the ignition means and control wire or wires therefore can be integrally manufactured with the barrel.  
           [0046]    A barrel assembly may alternatively include ignition apertures in the barrel and the ignition means are disposed outside the barrel and adjacent the apertures. A non-metallic outer barrel that may include recesses adapted to accommodate the ignition means may surround the barrel. The outer barrel may also house electrical conductors that facilitate electrical communication between the control means and ignition means. The outer barrel may be formed as a laminated plastics barrel that may include a printed circuit laminate for the ignition means.  
           [0047]    The barrel assembly may have adjacent sub-projectiles that are separated from one another and maintained in spaced apart relationship by locating means separate from the sub-projectiles, and each sub-projectile may include an expandable sealing means for forming an operative seal with the bore of the barrel. The locating means may be the propellant charge between adjacent sub-projectiles and the sealing means suitably includes a skirt portion on each sub-projectile that expands outwardly when subject to an in-barrel load. The in-barrel load may be applied during installation of the sub-projectiles or after loading such as by tamping to consolidate the column of sub-projectiles and propellant charges or may result from the firing of an outer sub-projectile and particularly the adjacent outer sub-projectile.  
           [0048]    The rear end of the sub-projectile may include a skirt about an inwardly reducing recess such as a conical recess or a part-spherical recess or the like into which the propellant charge portion extends and about which rearward movement of the sub-projectile will result in radial expansion of the sub-projectile skirt. This rearward movement may occur by way of compression resulting from a rearward wedging movement of the sub-projectile along the leading portion of the propellant charge it may occur as a result of metal flow from the relatively massive leading part of the sub-projectile to its less massive skirt portion.  
           [0049]    Alternatively the sub-projectile may be provided with a rearwardly divergent peripheral sealing flange or collar which is deflected outwardly into sealing engagement with the bore upon rearward movement of the sub-projectile. Furthermore the sealing may be affected by inserting the sub-projectiles into a heated barrel that shrinks onto respective sealing portions of the sub-projectiles. The sub-projectile may comprise a relatively hard mandrel portion located by the propellant charge and which cooperates with a deformable annular portion may be moulded about the mandrel to form a unitary sub-projectile which relies on metal flow between the nose of the sub-projectile and its tail for outward expansion about the mandrel portion into sealing engagement with the bore of the barrel.  
           [0050]    The sub-projectile assembly may include a rearwardly expanding anvil surface supporting a sealing collar thereabout and adapted to be radially expanded into sealing engagement with the barrel bore upon forward movement of the sub-projectile through the barrel. In such a configuration it is preferred that the propellant charge have a cylindrical leading portion that abuts the flat end face of the sub-projectile.  
           [0051]    The sub-projectiles may be adapted for seating and/or location within circumferential grooves or by annular ribs in the bore or in rifling grooves in the bore and may include a metal jacket encasing at least the outer end portion of the sub-projectile. The sub-projectile may be provided with contractible peripheral locating rings which extend outwardly into annular grooves in the barrel and which retract into the sub-projectile upon firing to permit its free passage through the barrel.  
           [0052]    The electrical ignition for sequentially igniting the propellant charges of a barrel assembly may preferably include the steps of igniting the leading propellant charge by sending an ignition signal through the stacked sub-projectiles, and causing ignition of the leading propellant charge to arm the next propellant charge for actuation by the next ignition signal. Suitably all propellant charges inwardly from the end of a loaded barrel are disarmed by the insertion of respective insulating fuses disposed between normally closed electrical contacts.  
           [0053]    Ignition of the propellant may be achieved electrically or ignition may utilise conventional firing pin type methods such as by using a centre-fire primer igniting the outermost sub-projectile and controlled consequent ignition causing sequential ignition of the propellant charge of subsequent rounds. Controlled rearward leakage of combustion gases or controlled burning of fuse columns extending through the sub-projectiles may achieve this.  
           [0054]    In other embodiments, the ignition is electronically controlled with respective propellant charges being associated with primers that are triggered by distinctive ignition signals. For example the primers in the stacked propellant charges may be sequenced for increasing pulse width ignition requirements whereby electronic controls may selectively send ignition pulses of increasing pulse widths to ignite the propellant charges sequentially in a selected time order. Preferably however the propellant charges are ignited by a set pulse width signal and burning of the leading propellant charge arms the next propellant charge for actuation by the next emitted pulse.  
           [0055]    Suitably in such embodiments all propellant charges inwardly from the end of a loaded barrel are disarmed by the insertion of respective insulating fuses disposed between insertion of respective insulating fuses disposed between normally closed electrical contacts, the fuses being set to burn to enable the contacts to close upon transmission of a suitable triggering signal and each insulating fuse being open to a respective leading propellant charge for ignition thereby.  
           [0056]    In certain embodiments the barrel assemblies may be of the low-pressure type, which fire grenade-like sub-projectiles although high muzzle pressure barrel assemblies may be used. Respective barrel assemblies may be loaded with different sub-projectiles and the barrel assemblies may have different size bores for accommodating different size sub-projectiles.  
           [0057]    Suitably each sub-projectile includes a trailing collar captively mounted to the sub-projectile body and when stored in the barrel, extends rearwardly to wedge against the nose portion of a trailing sub-projectile body. Suitably a shallow wedge provides the wedging action whereby, in use, the trailing end of the collar is expanded into operative sealing engagement with the barrel.  
           [0058]    The trailing collar may be mounted for limited axial movement relative to the sub-projectile body and the leading end of the collar formed with an annular sealing face engageable with a complementary face formed on the sub-projectile body whereby rearward movement of the sub-projectile body resulting from the reaction of propellant gases thereon forces the its complementary face into sealing engagement with the annular sealing face at the leading end of the collar.  
           [0059]    The complementary face and the annular sealing face may extend substantially radially and be formed with complementary sealing features thereon. However it is preferred that these faces are complementary part-conical sealing faces which wedge into tight sealing engagement with one another. The leading end part may also be expandable into operative sealing engagement with the barrel. Suitably however the wedging between the part-conical faces are relatively steep faces whereby the leading end of the collar is not expanded into operative sealing engagement with the barrel by the wedging action.  
           [0060]    In low pressure applications, preferably each sub-projectile is associated with a high-pressure propellant chamber that exhausts to respective low-pressure propulsion chambers formed between the adjacent sub-projectiles for efficient low muzzle velocity operation. The high-pressure propellant chambers may be formed integrally with the sub-projectile body or the trailing collar or be provided at the exterior of the barrel to communicate therewith through ports provided through the barrel wall.  
           [0061]    Suitably the configuration of the space into which the ignited propellant propagates and the propellant properties are such that only low barrel pressures occur in use, such as in the order of 2,000 psi to 5,000 psi. Typically the collar is such that in its relaxed attitude it does not prevent free movement of the projectile through the barrel either for loading purposes or during firing.  
           [0062]    A pressure pad is mounted on the housing inwardly of the open trailing end. The collar is relocated from the engaged condition upon ignition of the propellant and is retained in a relaxed condition by the pressure pad for passage through the barrel and out the muzzle of the barrel.  
           [0063]    The projectile may be of the conventional type and be conventionally fired or preferably be adapted to be fired from a barrel assembly that includes a plurality of projectiles axially disposed within a barrel wherein each of said projectiles are associated with a discrete propellant charges for propelling said projectiles from the barrel.  
           [0064]    The projectile, in a preferred form, may be generally spherical in shape and have the multiplicity of barrel assemblies radially disposed from the centre of the sphere. The barrel assemblies may be the same or different. For example whilst large diameter barrels may be disposed from the centre of the spherical projectile. Smaller diameter barrels may be positioned between the larger diameter barrels to provide the maximum sub-projectile density in the projectile. It may be desirable to provide the projectile with the maximum barrel packing density and hence firepower. Alternatively it may be desirable to provide the projectile with a variety of barrel bores in order that sub-projectiles of a variety of calibres may be utilised.  
           [0065]    The projectile may be a saboted projectile for advantageous deployment. A spherical projectile may be saboted into a more convenient shape for firing from a conventional deployment system such as in the form of a conventional munition. Alternatively if it is desirable to provide increased muzzle velocity a saboted projectile can accommodate an increased propellant charge without require a prohibitive barrel length.  
           [0066]    Barrel assemblies that are radially disposed from the centre of mass of the projectile allow the projectiles to deploy the sub-projectiles in a regular and readily controlled manner. Barrel assemblies that are radially disposed from the centre of mass of the projectile allow the projectile to maintain its attitude. By deploying sub-projectiles in a manner that results in zero resultant reactive force on the projectile the projectile may be maintained on its desired trajectory  
           [0067]    A number of sub-projectiles can be fired simultaneously, or in quick succession. In such arrangements the electrical signal may be carried externally of the barrel or it may be carried through the superimposed sub-projectiles that may clip on to one another to continue the electrical circuit through the barrel, or abut in electrical contact with one another. The sub-projectiles may carry the control circuit or they may form a circuit with the barrel.  
           [0068]    The projectile of the present invention may deploy the sub-projectiles in a predetermined pattern that may be selected for particular applications. For example, in order to intercept and destroy an incoming missile, it is desirable to deploy the sub-projectiles in a manner that maximises the likelihood of the missile impacting with one or more of the sub-projectiles. Fragmentation systems have been employed to scatter fragments of a projectile in the path of an incoming missile. However, systems such as this that explode the projectile generally produce a band of fragments that disperse and form an expanding spherical shell. The projectiles may deploy the sub-projectiles of the invention in a more homogeneous manner throughout the space occupied by the predetermined pattern. By controlling the timing of the firing of the sub-projectiles it is possible to establish a three dimensional “frag” pattern having a substantially homogeneous distribution of sub-projectiles. Alternatively, the sub-projectiles may be concentrated in areas where the missile is more likely to be intercepted so as to increase the effectiveness of the deployed sub-projectiles.  
           [0069]    The sub-projectile may contain material for forming air-borne images. The image forming material may include, for example, explosive matter, incendiary matter, incandescent or luminous matter or other matter to provide a highly visible temporary image. Alternatively, the image forming matter may include smoke, gas, particles or sheets or strips, such as in the nature of chaff, or other material capable of being dispersed to form, an image. Accordingly, the projectile of the invention may be advantageously employed to launch counter-measures from military aircraft. The image forming matter may also include means for slowing its descent from its dispersed position, such as a parachute and the like.  
           [0070]    The sub-projectiles may be arranged in the barrel assemblies such that once fired and the image forming matter deployed, the desired temporary airborne image is formed. Sub-projectiles containing different image forming matter, either differing in colour or form, may be sequentially loaded into each barrel assembly.  
           [0071]    The image forming matter may be deployed, for example, by explosive means, by stored energy or by separation of separable parts of the sub-projectile to expose the image forming matter or by any other suitable dispersing means.  
           [0072]    The image forming matter may be contained within a housing that may be of any suitable configuration that provides for the containment of the image forming matter and is suitably configured for engagement with the trailing end of the expandable collar of the preceding projectile. Preferably the housing is of the type employed with grenade-like projectiles, having relatively squat shape although projectiles having elongate housings could also be employed.  
           [0073]    The housing may suitably be formed from biodegradable material and/or combustible material. This material may be based on a natural product such as woodchip or a synthetic material, such as a biodegradable polymer.  
           [0074]    Advantageously the projectiles of the present invention may deploy selected sub-projectiles in order to control the course of the projectile. Such deployment may be understood as a divert propulsion system and may be used to affect limited corrections to the position of the projectile for the deployment of the remainder of the sub-projectiles in the desired pattern.  
           [0075]    The projectiles of the present invention may suitably be employed in a defence system of the type described in the present applicant&#39;s International Patent Application No. PCT/AU00/01351. 
       
    
    
     BRIEF DETAILS OF THE DRAWINGS  
       [0076]    In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:  
         [0077]    [0077]FIG. 1 is a cross sectional illustration of a projectile according to a preferred embodiment of the present invention;  
         [0078]    [0078]FIG. 2 is a cross sectional illustration of a saboted projectile for use in a barrel assembly having a plurality of axially disposed saboted projectiles;  
         [0079]    [0079]FIG. 3 is a cross sectional illustration of the firing of saboted projectiles as shown in FIG. 2;  
         [0080]    [0080]FIG. 4 is a side elevational diagram of a defence system according to a further embodiment of the invention; and  
         [0081]    [0081]FIG. 5 is a perspective diagram of the defence system of the further embodiment. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0082]    [0082]FIG. 1 shows a projectile  10  having six (6) large bore barrels  12  of a convenient calibre, although only four (4) are shown in this cross sectional representation. The remaining two (2) large bore barrels (extending perpendicularly to the page) are depicted at  11 . The cross sectional representation also shows four (4) medium bore barrels  13  of medium calibre, and forty-eight (48) small bore barrels  14  of relatively small calibre. The large bore  12 , medium bore  13  and small bore  14  barrels each contain a plurality of axially disposed sub-projectiles  16 , as represented on the drawing. The sub-projectiles are associated with propellant charges  17  and ignition means  18 , which ignition means may be sequentially fired under the control of an electronic controller  15 . In some embodiments, the projectile  10  may also contain an explosive charge for terminal detonation.  
         [0083]    The electronic controller  15 , which is disposed in the centre of the projectile  10  behind the barrels  11 ,  12  in this embodiment, may include sensors for tracking an incoming missile when in-flight. Alternatively, the electronic controller  15  may receive firing instructions from a remote tracking station via a communications link. The sequenced firing of a number of the sub-projectiles may thus be coordinated to provide an improved likelihood of impacting with the targeted incoming missile or similar threat.  
         [0084]    [0084]FIG. 2 shows a projectile of the type shown in FIG. 1 with a sabot  20 , wherein the sub-projectiles are omitted for reasons of clarity. The projectile  10  is retained in a barrel within the sabot  20 . The sabot includes a forward sabot portion  21 , a rearward sabot portion  22  and an expanding sleeve  23  disposed about a chamfered rear surface  24  of the rearward sabot portion. The detonation and firing of a propellant charge in front of the forward sabot portion  21  forces the rearward sabot portion  22  against the expandable sleeve  23  and causes the expandable sleeve to sealably engage with the bore of a parent barrel.  
         [0085]    [0085]FIG. 3 shows a series of projectiles  10  being fired from a parent barrel assembly  30 , having a plurality of parent barrels  31 ,  32  and  33 . Projectile  10 A has been fired from barrel  33  and has discarded its sabot (not shown). Projectile  10 B has been fired from barrel  32  and the sabot  20  is shown in the process of being discarded. The expandable sleeve  23  has detached from the rearward sabot  22  and the rearward sabot  22  has also detached from projectile  10 B. Forward sabot  21  has similarly detached from the projectile  10 B. Projectile  10 C has been more recently fired from barrel  31  and the sabot  20  has commenced detachment from projectile  10 C.  
         [0086]    Referring to FIGS. 4 and 5, it will be seen that a designated area  40  to be defended is monitored by an array of field sensors  41  distributed over the designated area and which may be of any suitable type such as pressure, acoustic or seismic type sensors.  
         [0087]    The illustrated defence system  42  employs a weapon taking the form of a pair of grenade boxes  43  each using the barrel assemblies  30  and coupled to a remote sensing means  44  and to a receiver unit  49  associated with the field sensors  41 . The remote sensing means  44 , which in the embodiment is tower mounted, is adapted to sweep the designated area  40  using electro-optical or microwave techniques to monitor any intrusion into the designated area by a personnel, vehicles or other intruder.  
         [0088]    The receiver unit  49  is adapted to receive signals from the array of field sensors  41 , using a radio frequency (RF) communications link in the embodiment (although a cable link may be employed in the alternative). Upon any sensed intrusion in the area  40 , the zone of the intrusion will be isolated for targeting by projectiles  10  fired from the grenade boxes  43 . Thus the designated area  40  is monitored by either or both of the array of field sensors  41  or by the remote sensing means  44 .  
         [0089]    It is desirable that each grenade box  43  is located in a substantially concealed position, such as a hole in the ground. Once set up, the hole in which the grenade box  43  is placed may be back filled without causing any detrimental effects to the operation of the barrel assemblies  30  therein. In other arrangements, the grenade box  43  may be conveniently concealed in foliage and adjusted by screw jacks  48  associated with a support base  47  for the grenade box.  
         [0090]    A subsidiary control circuit  43   a  (see FIG. 5), provided as a plug-in connection to the grenade box  43 , is fitted on-site but not during transport so as to maintain safety of the weapon during transport. Once fitted with the control circuit  43   a , the weapon is armed and ready to fire in accordance with controls provided by the sensor unit  44  and/or the receiver unit  49 . The control circuit is suitably able to communicate with the electronic controller  15  in a respective projectile, as required.  
         [0091]    A central remote sensor  44  in FIG. 2 is linked to multiple grenade boxes  43  via respective control circuits  43   a . In use, if an intrusion into the detected area is detected at a zone, such as any one of the zones indicated as  50  to  59 , the selected grenade box  43  can be activated to fire one or more projectiles  45  into that particular zone. The sub-projectiles may be subsequently fired a respective projectile  45 , either in accordance with a pre-selected sequence or under remote control, to produce a predetermined pattern of deployed sub-projectiles. The pattern of sub-projectiles is desirably chosen in accordance with the nature of the intruder.  
         [0092]    An intruder coming into the designated area  40  may be in any of a number of forms and may include a plurality of intruders. An intruder may be military personnel, in the form of an infantryman or foot soldier. Alternatively, the intruder may be a manned or unmanned vehicle such as an armoured car or tank. The intruder may have sophisticated defence systems that may track the trajectory of an incoming round and calculate the location of the launch apparatus, thereby enabling an attack on the previously hidden launch apparatus. The defence system of the embodiment allows the trajectory of the projectile to be diverted in flight by launching sub-projectiles, thereby enabling an apparent trajectory to be tracked and the true location of the launch apparatus to be masked. If feasible, the apparent trajectory may be selected to draw enemy fire directed at the defence system  42  to other enemy positions.  
         [0093]    Whilst the above defence system is land based, another aspect of the invention concerns projectiles that might be termed water mines. These water mines may be launched from a ship and remain floating in the water and activated for either remote control or autonomous operation using on-board sensor systems, including radar, sonar or infra-red sensors. A line of such mines, incorporating stabilising or anchoring means such as a suspended weight, could be laid to provide a marine defence perimeter capable or being activated or deactivated as required.  
         [0094]    In another mode of deployment, projectiles of the invention may be dropped from an aircraft such as a helicopter. Stabilising or anchoring means, such as spikes, could be provided to fix retain projectiles in one position on the ground. A first layer of sub-projectiles could include sensor systems for launching to detect the presence of enemy troops or vehicles, which could be engaged as required by grenades in subsequent layers in individual barrels of the projectile. Further sensors may be provided in other layers for surveying the result of an engagement.  
         [0095]    A further mode of deployment is to provide a projectile of a size that can be conveniently hand-held and deployed by throwing, similar to a conventional grenade. However, the incorporation of sub-projectiles in barrels in the hand-delivered projectile enables it to be used in a repeating mode using a pre-set time delay or a remote control facility. This may provide certain advantages in engagements that occur in closed spaces, such as in urban warfare or topography including caves. The sub-projectiles may incorporate non-lethal rounds and an audio annunciation system for warning, perhaps in a siege situation, that additional rounds are capable of being fired if the miscreants involved fail to surrender immediately.  
         [0096]    Projectiles of the invention may be carried into space and delivered into orbit around a planet or moon as required, effectively comprising a satellite. Since the barrel assemblies can be radially dispersed within a generally spherical body, they function very effectively to correct the position of the satellite in orbit, protect a zone around a valuable satellite from space junk, meteorites and the like, or to engage an enemy space vehicle or satellite. A change of position can be undertaken much more rapidly in the low gravity environment because of the energy liberated by firing a solid sub-projectile, rather than a burst of gas as in conventional satellites. The satellite projectiles are suitably constructed so as to be consumed by combustion upon re-entry into the atmosphere subsequent to orbital decay.  
         [0097]    In one particular form, the satellite may comprise a super-projectile which in turn may deploy projectiles of the present invention from radially disposed barrel assemblies therein, and those deployed projectiles may themselves be equipped with sub-projectiles, thus providing a two tiered defence system. This two tiered system of course may be employed in other applications of suitable scale.  
         [0098]    It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is herein set forth in the following claims.