Abstract:
A base cone for a projectile including: a cone member being movable between a retracted position and an extended deployed position, the deployed position being longer in an axial direction than the refracted position; a member adapted to connect the cone member to a trailing portion of the projectile; and a release mechanism for releasing the cone member from the refracted position to the extended deployed position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/259,178 filed on Nov. 8, 2009, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to munitions, and more particularly to a speed-adaptive deployable boat-tailing cone for munitions for range extension. 
     2. Prior Art 
     Boat-tailing consists of the reduction of the aft cross-sectional area of a flying object in order to reduce drag. Boat-tailing is most effective and critical for supersonic flights. For each speed of a projectile and the flying altitude, there is an optimal boat-tailing angle. For example, if the boat-tailing is two extreme, i.e., the aft cross-sectional area is reduced too rapidly along the length of the flying object, then aft shock becomes too strong, boundary layer separation occurs and drag is considerably increased. If the rate of reduction in the aft cross-section is too slow, then the amount of reduction in the drag is minimal. 
     At supersonic speeds, the optimal boat-tailing cone angle is a function of Mach number. The boat-tailing angle is the largest at the highest projectile speeds and is gradually decreased as the projectile speed approaches the subsonic speeds. It has been shown that base drag accounts for up to 50% of total drag on a projectile during supersonic flight. With base bleed and boat-tailing, drag in supersonic flight has been shown to be significantly reduced. 
     SUMMARY OF THE INVENTION 
     It is therefore highly desirable to provide projectiles, particularly gun-fired projectiles, whether subsonic or supersonic, with appropriate boat-tailing to reduce the drag and thereby significantly increase their range. 
     In addition, it is highly desirable that the boat-tailing section be deployable from an initial configuration that occupies minimal length and volume of the projectile, thereby would neither add significantly to the length of the projectile nor occupy a considerable volume of the projectile. 
     In addition and particularly for supersonic rounds, the boat-tailing angle can be variable to achieve maximum drag reduction as the speed of the projectile varies. The boat-tailing angle may be made to be varied to a number of discrete angles rather than being varied continuously as the speed of the projectile is reduced. With such a design, a very simple and inexpensive boat-tailing mechanism is achieved that would also not occupy a considerable amount of space. 
     In most gun-fired munitions, the round is designed with a relatively flat base where it interacts with the high pressure gases generated by the detonated charges to accelerate the round along the gun barrel. Thus, an objective is to provide the method and the means of providing boat-tailing cones (hereinafter also referred to as “base cones”) for projectiles, particularly gun-fired projectiles that are retracted to a relatively small volume at the base of the projectile and deployed after the projectile has exited the gun barrel. The base cones may be deployed automatically upon the round exiting the barrel or may be programmed to deploy certain amount of time into the flight or following the detection of certain event(s). 
     Accordingly, a base cone for a projectile is provided. The base cone comprising: a cone member being movable between a retracted position and an extended deployed position, the deployed position being longer in an axial direction than the retracted position; a member adapted to connect the cone member to a trailing portion of the projectile; and a release mechanism for releasing the cone member from the retracted position to the extended deployed position. 
     The cone member can be tapered from a first diameter at the trailing edge of the projectile to a second diameter, the second diameter being smaller than the first diameter. The base cone can further comprise a cap disposed to cover the second diameter. The base cone can further comprise a mass disposed on at least a portion of the cone member for facilitating extension of the cone member into the extended deployed position due to an acceleration of the projectile. 
     The cone member can include a helical strip. The helical strip can include stops at an edge of the helical strip for restricting movement of the helical strip in the longitudinal direction. 
     The cone member can be a bellows. The base cone can further comprise a biasing member for biasing the bellows in the extended deployed position. 
     The cone member can comprise a plurality of ribbon members having a rolled configuration in the retracted position and at least partially unrolled configuration in the extended deployed position. The plurality of ribbons can be connected to each other. The plurality of ribbons can include stiffening ribs. 
     The cone member can include a plurality of rings, each successive ring in the longitudinal position is smaller in diameter than the previous ring. The base cone can further comprise one or more linkages connecting two or more of the plurality of rings. The base cone can further comprise a cap disposed to cover a last of the plurality of rings in the longitudinal direction. The base cone can further comprise a biasing member for biasing the plurality of rings in the extended deployed position. 
     The cone member can includes a plurality of plate members. The plate members can be interconnected. 
     The release mechanism can be one or more of a cable and bolt. The cable or bolt can be released by one or more of an electrical or explosive initiation. 
     The release mechanism can include at least first and second release mechanisms, the first release mechanism being adapted to extend the cone member in a first extended deployed position and the second release mechanism being adapted to extend the cone member in a second extended deployed position, the second extended deployed position being longer in the longitudinal direction then the first extended deployed position. 
     Also provided is a projectile comprising: a shell having a base; and a base cone connected to the base, the base cone including: a cone member being movable between a refracted position and an extended deployed position, the deployed position being longer in an axial direction than the retracted position; a member adapted to connect the cone member to the base of the projectile; and a release mechanism for releasing the cone member from the retracted position to the extended deployed position. 
     Still further provided is a method for deploying a base cone from a projectile. The method comprising: firing a projectile, and deploying a cone member disposed on a trailing edge of the projectile from a retracted position to an extended deployed position, wherein the extended deployed position is aft of the trailing edge of the projectile in a longitudinal direction of the projectile. 
     The cone member can be deployed in a single discrete step from the retracted position to the extended deployed position. 
     The cone member can be deployed in two or more discrete steps from the refracted position to at least one intermediate position to the extended deployed position. 
     The deploying can be based on an elapsed time after firing. 
     The deploying can be based on a speed of the projectile. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIGS. 1   a ,  1   b  and  1   c  illustrate a first embodiment of a base cone for a munition, in which  FIG. 1   a  illustrates the base cone not being deployed,  FIG. 1   b  illustrates the base cone being fully deployed and  FIG. 1   c  illustrates a partial sectional view of the base cone of  FIG. 1   b.    
         FIGS. 2   a ,  2   b  and  2   c  illustrate a second embodiment of a base cone for a munition, in which  FIG. 2   a  illustrates the base cone not being deployed,  FIG. 2   b  illustrates the base cone being fully deployed and  FIG. 2   c  illustrates a sectional view of the base cone of  FIG. 2   a.    
         FIGS. 3   a ,  3   b ,  3   c  and  3   d  illustrate a third embodiment of a base cone for a munition, in which  FIG. 3   a  illustrates the base cone not being deployed,  FIG. 3   b  illustrates the base cone being fully deployed,  FIG. 3   c  illustrates a portion of the base cone of  FIG. 3   a  and  FIG. 3   d  illustrates the portion of  FIG. 3   c  being deployed. 
         FIGS. 4   a  and  4   b  illustrate first and second variations of the third embodiment. 
         FIGS. 5   a ,  5   b ,  5   c ,  5   d  and  5   e  illustrate a fourth embodiment of a base cone for a munition, in which  FIG. 5   a  illustrates a perspective view of the base cone not being deployed,  FIG. 5   b  illustrates a perspective sectional view of the base cone of  FIG. 5   a ,  FIG. 5   c  illustrates a side perspective view of the base cone of  FIG. 5   a ,  FIG. 5   d  illustrates the base cone of  FIG. 5   a  being partially deployed and  FIG. 5   e  illustrates a sectional view of the base cone being fully deployed. 
         FIGS. 6   a ,  6   b ,  6   c  and  6   d  illustrate a fifth embodiment of a base cone for a munition, in which  FIG. 6   a  illustrates the base cone not being deployed,  FIG. 6   b  illustrates a sectional of the base cone of  FIG. 6   a ,  FIG. 6   c  illustrates a sectional of the base cone being fully deployed and  FIG. 6   d  illustrates a portion of the base cone of  FIG. 6   c  being deployed. 
         FIGS. 7   a ,  7   b  and  7   c  illustrate a sixth embodiment of a base cone for a munition, in which  FIG. 7   a  illustrates a portion of the base cone being fully deployed,  FIG. 7   b  illustrates the base cone not being deployed and  FIG. 7   c  illustrates the portion of  FIG. 7   a  when not deployed. 
         FIGS. 8   a  and  8   b  illustrate a seventh embodiment of a base cone for a munition, where  FIG. 8   a  illustrates an undeployed state and  FIG. 8   b  illustrates a fully deployed state. 
         FIGS. 9   a  and  9   b  illustrate a eighth embodiment of a base cone for a munition, where  FIG. 9   a  illustrates an undeployed state and  FIG. 9   b  illustrates a fully deployed state. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The first embodiment of the base cone  20  is shown in  FIGS. 1   a ,  1   b  and  1   c . The base cone is constructed by a strip  15  (which may be formed of spring steel or the like) that is wound as a tapered helix  13  as shown in  FIG. 1   b . The lips  14  of the strips are formed such that they interlock as shown in  FIG. 1   c . In the pre-deployed configuration, the tapered helix  13  is compressed to form a relatively thin “disc”  11  at the base  10  of the projectile  17 . In the pre-deployed configuration, the tapered helix is held in its state via certain keeper or locking mechanisms. Numerous types of such locking mechanisms may be used, such as a cable or bolt that may be released electrically or with explosive charges. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding cable or any other known methods in the art. The base cone tapered helix  13  can be biased as a helical spring to deploy in the direction of the arrow  16  once it is released by the locking mechanism. The base cone tapered helix  13  may be provided with a cap  12 , which is affixed to the last coil of the tapered helix  13 . The release mechanism may be provided to release the full length “L” of the base cone at once or may be provided to release portion of such length “L” up until the entire length is released. That is, the entire length “L” of the base cone may be released in stages as a function of time, speed or other factors. The base cone can be attached to the projectile  17  by any means known in the art, or in some cases, at least a portion of the base cone can be formed integrally therewith. 
     Another embodiment  30  of the tapered base cone is shown in  FIGS. 2   a ,  2   b  and  2   c . The base cone is constructed as a bellows  31  as shown in  FIG. 2   a  in its collapsed configuration, with its cutaway view shown in  FIG. 2   c . The bellows  31  may be formed from any material known in the art, such as an elastomer or flexible metal. In its collapsed configuration, the base cone bellow  31  is held in its state via certain keeper or locking mechanisms (as discussed above). Numerous types of such locking mechanisms, such as those described for the previous embodiment may be used to perform this function. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding wire or any other known methods in the art. The base cone bellows is fixed to the base of the projectile  33 . The base cone bellows  31  can be formed of a material that is biased to deploy out away from the projectile base or can be biased with a biasing member or means to deploy out away from the projectile base into the base cone  32  once it is released by the locking mechanism, which may be all at once or staged in portions. The base cone  32  may be provided with a cap  34 , which can be integral to the base cone bellows  31 . 
     Another embodiment  40  of the tapered base cone is shown in  FIGS. 3   a ,  3   b ,  3   c  and  3   d . The base cone is constructed by a plurality of “ribbons”  41  as shown in  FIG. 3   a , which are formed similar to a retractable tape measure coil or the like to offer higher cantilever stiffness than a flat plate, i.e., with curved cross-sections to make them resistant to bending, but with thin enough thickness so that when bent, they would not cause permanent (plastic) deformation. A circular array of rolled ribbons  42 , as shown in their rolled (pre-deployment) configuration in  FIG. 3   b , are mounted to the base  43  of the projectile  44  (shown partially) by any means known in the art or formed integrally therewith, occupying a relatively thin and small volume. A close-up view of a rolled ribbon  42  is shown in  FIG. 3   c . The ribbon  42  in its deployed configuration  45  (forming a portion of the base cone  40 ) is shown in  FIG. 3   d . The rolled ribbons  42  can be biased to deploy to the configuration  45  shown in  FIG. 3   d  (i.e., configuration  41  shown in  FIG. 3   a ). However, in the pre-deployment state of the base cone  40 , the rolled ribbons  42  are held in their rolled state via certain keeper or locking mechanisms (not shown). Numerous types of such locking mechanisms, such as those described for the previous embodiment may be used to perform this function. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding cable or bolt or any other known methods in the art. The rolled ribbons  42  are biased to deploy out away from the projectile base  43  (and the projectile  44 ) into the base cone  40  once they are released by the locking mechanism. The base cone  40  may be provided with a cap (not shown), which is affixed to the tip  46  of the rolled ribbons  42 . An end  42   a  of each of the ribbons  42  can be provided with a relatively heavy mass which unfolds the ribbon when the ribbon experiences the firing acceleration. 
     The ribbons  41  ( FIG. 3   a  and as shown individually in  FIG. 3   d  and enumerated as  45 ) may be stiffened against bending in their deployed configurations in many different ways. For example, deployed ribbons  47  may be provided with gussets  48  as shown in  FIG. 4   a . The adjacent ribbons  47  may also be held together with elements such as rings  49  (or wires or the like) as shown in  FIG. 4   b.    
     In yet another embodiment, the base cone  50  has a telescopic design and is constructed with a number of “ring” type segments  51  as shown in  FIGS. 5   a - 5   e . The segments can have interlocking lips (not shown) similar to those shown for the embodiment  20  as shown in  FIG. 1   c . The first ring segment  52  is affixed to the base of the projectile  54 . The base cone  50  is preferably provided with a cap  55 , which is affixed or is preferably integral to the last ring  56  as shown in  FIG. 5   b . In the pre-deployed configuration shown in  FIG. 5   a , the telescopic rings  51 ,  52  and  56  are held together by one or more link mechanisms  58 . As shown in  FIGS. 5   d  and  5   e , the link mechanisms  58  can have link arms  59  rotatably connected at pivot points  60 . The link mechanisms can also be provided in pairs  58   a ,  58   b  as shown in  FIG. 5   e  and such pairs can be provided in several sets ( 58   c ,  58   d ) at angular intervals around the base cone.  FIGS. 5   d  and  5   e  illustrate link mechanisms  58   a ,  58   c  having one link  59   a  pivotably connected to a base plate  61  at one end and to the other link arm  59   b  at the other end and the link  59   b  being pivotally connected to an intermediate plate  62  at the other end. Similarly,  FIGS. 5   d  and  5   e  illustrate link mechanisms  58   b ,  58   d  having one link  59   c  pivotably connected to the intermediate plate  62  at one end and to the other link arm  59   d  at the other end and the link  59   d  being pivotally connected to the cap  55  at the other end. 
     The telescopic rings  51 ,  52  and  56  are maintained in their un-deployed state as shown in  FIGS. 5   a - 5   c  via certain keeper or locking mechanisms, such as a cable  63  or bolt  63  that can be disengaged electrically or via an explosive charge as is well known in the art. Numerous types of such locking mechanisms may be used. The locking mechanism may also be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of the holding cable  63  or bolt  63  or any other known methods in the art. As discussed above with regard to the embodiment of  FIG. 1   a , the locking mechanism can be provided in stages, such as a secondary cable  63   a  or bolt  63   a  as shown in  FIG. 5   d  that maintains the telescopic rings  51 ,  52  and  56  in an intermediate position between un-deployed and fully deployed. The secondary cable  63   a  or bolt may be released in the same manner as the primary cable  63  or bolt  63  after an elapsed time period or upon sensing a predetermined criteria, such as speed. 
     Once released, the telescopic rings  51 ,  52  and  56  can be biased in the deployed configuration shown in  FIGS. 5   d  and  5   e , such as with compression spring  64 , an inflatable balloon or other means known in the art. The compression spring  64  can be maintained in the base cone by holding cups  64   a  in the base plate  61  and cap  55  and an intermediate open cup  65  in the intermediate plate  62 . 
     In yet another embodiment, the base cone  6 . 0  consists of panels  6 . 1  which are held together longitudinally by flexible elements  6 . 2 . In the pre-deployed configuration of the base cone  6 . 0 , each set of longitudinal panels  6 . 3  shown in  FIG. 6   d  is “rolled up” (indicated by numeral  6 . 4  in  FIGS. 6   a  and  6   b ), and stored at the base (preferably in a “housing segment  6 . 5  as shown in  FIG. 6   b ) of the projectile  66 . In the pre-deployed configuration shown in  FIGS. 6   a  and  6   b , rolled-up panels  6 . 4  are held in their un-deployed state via certain keeper or locking mechanisms (not shown). Numerous types of such locking mechanisms may be used. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding wire or any other known methods in the art. The panels  6 . 1  of the longitudinal panel sets  6 . 3  may be held together at certain intervals by certain means such as elastic elements or the like (not shown) or rings affixed to at least one set of panels located certain distance along the base cone  6 . 0  to hold the longitudinal panel sets together to the desired shape of the base cone  6 . 0  and also to provide the means to stiffen the base cone  6 . 0 . The base cone  6 . 0  may be provided with a cap (not shown), which is affixed to the outer side of the outer panel set  6 . 7 . 
     In an alternative embodiment of the embodiment of  FIG. 6  is shown in  FIG. 7   a , in which the panels  68  are deployed telescopically to the deployed configuration as panels  69  shown in  FIG. 7   a . Guides (not shown) are provided on the edges of the panels  68  to allow their deployment to the extended position  69  and preferably their interlocking in the extended position. In  FIG. 7   c , one set of the panels  68  are shown in their pre-deployed configuration as panel sets  70 . each of the panel sets  70  may be constructed similarly to the base cone described with regard to  FIGS. 5   a - 5   e . In  FIG. 7   b , the panel sets  70  are shown as mounted in the base  71  of the projectile (similar to the rolled-up longitudinal panels  64  in  FIG. 6   a ). In the pre-deployed configuration shown in  FIG. 7   b , panel sets  70  are held in their un-deployed state via certain keeper or locking mechanisms (not shown). Numerous types of such locking mechanisms may be used. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding cable, bolt or any other known methods in the art. The panels  69  may be held together at certain intervals by certain means such as elastic elements or the like (not shown) or rings affixed to at least one set of panels located certain distance along the base cone to hold the panel  69  together to the desired shape of the base cone and also to provide the means to stiffen the base cone. The base cone may be provided with a cap as described for the aforementioned embodiments, which is affixed to the outer side  73  of the outer panels  72  ( FIG. 7   a ). 
     In yet another embodiment shown in  FIG. 8 , the base cone  80  consists of a tapered helical (or the like) spring  81  of circular or any other convenient cross section shown in its deployed configuration in  FIG. 8   a . In  FIG. 8   b  the spring  81  is shown in the pre-deployed configuration of the base cone  80  as positioned at the base (preferably housing)  82  of the projectile  83 . The base cone  80  is provided with a cap  84  (or an element with a similar structure) that can be affixed to the last coil of the spring  81 . In the pre-deployment configuration of the base cone  80  shown in  FIG. 8   b , the spring  81  is biased to extend to its deployed configuration of  FIG. 8   a  by preloading it in compression an appropriate amount. 
     In the pre-deployment configuration of the base cone  80  shown in  FIG. 8   b , the spring  81  is held in its un-deployed state via certain keeper or locking mechanisms. Numerous types of such locking mechanisms may be used. In the base cone  80 , the spring  81  is locked in its deployed (extended) configuration shown in  FIG. 8   a  by the cable  85 , which is attached to the cap  84  on one end and to the base of the projectile  82  on the other end. In its pre-deployment configuration shown in  FIG. 8   b , the cable  85  is retracted to the length  86  (e.g., through a retaining ring  87 ) and locked in place. The locking mechanism (not shown) may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding wire or any other known methods in the art. The spring  81  is covered by a non-extensible fabric or the like  88 . The covering  88  is preferably tightly held in place over the spring  81  when the base cone is deployed as shown in  FIG. 8   a  and is folded and stored in the projectile base  82  (indicated by the numeral  89  in  FIG. 8   b ) in the pre-deployed state of the base cone. 
     Another embodiment  90  is shown in  FIG. 9 . In this embodiment  90 , plates  91  are attached to the base cavity  92  of the projectile  93  by joints that allow the plates to be rotated out from their pre-deployment position shown in  FIG. 9   b  to their deployed position shown in  FIG. 9   a  to form the base cone  90 . The base cone provided by this embodiment  90  has relatively limited length equivalent to close to the diameter of the base cavity in which the plates  91  are mounted. In the pre-deployed configuration shown in  FIG. 7   b , the plates  91  are held in their un-deployed state via certain keeper or locking mechanisms (not shown). Numerous types of such locking mechanisms may be used. The locking mechanism may be designed to release the base cone due to the firing (setback) acceleration or set-forward acceleration or by certain programmed action such as release or cutting of a holding cable, bolt or any other known methods in the art. In their deployed configuration, the plates  91  may be held together at certain intervals by certain means such as elastic elements or the like (not shown) to provide the means to stiffen the base cone. The base cone plates  91  may form 3-dimensional surfaces such that in their deployed configuration they would collectively form a surface that covers the end of the base cone similar to the caps used to close the end of the base cones in the previously disclosed embodiments. 
     The mechanisms used to deploy the base cone in the above embodiments may be activated automatically, e.g., the firing setback or set-forward may act on an inertia element (displacing mass) to turn or displace a lever that unlocks the deployment mechanism (preferably by the force of a preloaded linear or rotary or other type of spring/elastic element). 
     In one embodiment, the aforementioned base cone deployment mechanism may be initially developed to a first length and cone angle and then sequentially to other sets of cone length and/or cone angles. Such sequential and step-wise base cone length and/or angle may be desirable to achieve optimal base cone configuration as the speed of travel of the projectile varies during the flight. The mechanism of varying the base cone length and/or angle can be actuated by sequential release of preloaded springs (which would require minimal electrical energy to achieve) as compared to the use of electrical motors which require a considerable amount of electrical energy and occupy a considerable amount of space. 
     It is appreciated by those familiar with the art that different types of structures, for example rings, struts, gussets, cables, etc., may be used to stiffen the base cones structures when necessary. 
     In many cases, the means used to deploy a base cone may also be used to stiffen the base cone structure. For example, a balloon may be inflated in the interior space of the embodiments of  FIGS. 1-3 , thereby causing them to deploy. The inflated balloon, particularly if it is constructed with relatively inextensible material, may also be used to stiffen the structure of the base cone and prevent it from collapsing. 
     The base cone caps (e.g., the caps in the base cone embodiments of  FIGS. 1-3 ) are preferably provided with “support legs” or solid supports to cover the gap between the cap and the projectile base to allow the pre-deployed base cone resistant to high firing pressures. Alternatively, the projectile base may be formed to touch the cap surface to support them during the firing. 
     It is appreciated that the gap between the cap and the projectile base may be used by the projectile as an added available space for any purpose including for providing the means to generate base bleed gasses to further reduce drag during the flight. 
     While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.