Patent Publication Number: US-6666141-B2

Title: Variable increment modular artillery propellant

Description:
FIELD OF THE INVENTION 
     The present invention provides an optimally modular and proportionately structurable packaging system and method for composing propellant charges without undue limitations on the number of zones (power or amounts of propellant needed for a particular shot) that can be fired. The invention is a method and system for packaging solid explosive artillery propellant in proportional amounts. Modules in the proportions specified by this invention can be combined to compose a total amount of loaded propellant that is nearly optimum for shooting at a specific target. One of the unique aspects of this invention includes its teachings that a sufficiently large number of zones could be composed using only two different sizes of charge containers thereby providing efficiency and ease in handling, shipping, and manufacturing. 
     DESCRIPTION OF THE PRIOR ART 
     Artillery projectiles are fired using total amounts of propellant that are selected to reach a designated target along a predetermined trajectory with a specific projectile type. Different guns use different kinds of propellant; for example: liquid propellant, bags of solid propellant, and rigid canisters of solid propellant. For a specific gun and propellant type, the amount of propellant used for a given shot, the zone, varies depending upon the distance to the target and the shape of the desired trajectory. Liquid propellant guns. allow a nearly infinite number of zones by metering the amount of liquid used. Liquid propellant guns are therefore theoretically capable of firing whatever trajectory is optimum to engage the target. Contemporary solid propellant systems are not as flexible. Because solid propellant is manufactured in uniformly sized modules, such as bags or combustible canisters, the number of different zones that can be fired is comparatively small. One or more modules of propellant are loaded prior to shooting the gun. Modules are indivisible and only complete modules can be loaded. Hence solid propellant guns must shoot along trajectories limited by the zones available. These result from using an integral number of modules (of the order of two to six), and these are not always the optimum shots. 
     SUMMARY OF THE INVENTION 
     The present invention achieves flexibility and adaptability to a variety of zones for solid propellants. The VIMAP structure provides a modular system of charge increments that can be assembled to compose different zones. The invention permits a module-based increment to be packaged in different ways, for example combustible canisters or bags. Specifically, various zones of total propellant power are constructed using two different module sizes. The modules are manufactured so that their propellant power is in the ratio of two consecutive integers greater than one. For example, the consecutive integers may be 2 and 3 or 3 and 4. In other words, an arrangement based on the integers 2 and 3 shall yield a smaller module that is ⅔ the propellant power of the larger. Similarly, if based on the integers 3 and 4, the smaller module shall be ¾ of the propellant power of the larger. Such modules would be combined in different arrangements to compose numerous zones. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of typical module assemblies, A and B, based on the integers 3 and 4. The propellant power of A-Module is considered to be unity and propellant B-Module is ¾. The assemblies indicate, for sample purposes, various arrangements and combinations of the Modules A and B. 
     FIG. 2 is a perspective view of basic modules showing interlocking canisters and bags of charge. 
     FIG. 3 is a graphical representation of the flight characteristics of a typical artillery projectile (the M549). A specific trajectory is a single point on this graph; its time of flight (TOF) is indicated on the vertical axis and the range to the target is indicated on the horizontal axis. Each broken line represents the locus of trajectories that can be achieved for a specific muzzle velocity. The muzzle velocity of a given shot is determined by the propellant zone used to fire it. 
     FIG. 4 Labeled Table I shows the zones that can be constructed from combinations of A and B modular charge increments that can be expressed by the integers 3 and 4. The power of an A-Module is equal to unity. The B-Module power is ¾. 
     FIG. 5 Labeled Table II shows the zones that can be constructed by combinations of A and B modular charge increments that can be expressed by the integers 2 and 3. The power of an A-Module is equal to one and the B-Module is ⅔. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a large number of combinations to yield different zones by utilizing only two sizes. Because propellant is dangerous to handle and difficult to measure precisely, the power of a module is fixed when it is manufactured. Once built, modules cannot be subdivided to obtain smaller charges. Further, a major reduction in module physical size is precluded by handling and structural concerns. 
     Heretofore, unicharge systems could only fire a limited number of zones corresponding to a fixed number of modules. Zone  1  would use 1 module, zone  2  used 2 modules, etc. An optimum shot might require an intermediate zone such as 1½. Such shots are impossible in present systems and a suboptimal shot (e.g., either zone  1  or zone  2 ) would be fired instead. The present invention overcomes these and other limitations as discussed hereinbelow. 
     FIG. 1 shows how Variable Increment Modular Artillery Propellent (VIMAP) modules consisting of two sizes can be combined to obtain different zones. A module structure  10  is composed of 6 A-Module  12 . The A-Module  12  represents a unit of charge. Thus, the A-Module  12  provides a specified propellant with a known capability. In module structure  10  the six A-Module  12  compose a zone  6  assembly. Similarly, module structure  14  is composed of A-Modules  12  and B-Modules  16 . The power of a B-Module  16  is related to the power of an A-Module  12  by a ratio of integers such as ⅔ or ¾. Thus, the module structure  14  provides three unitary A-Modules  12  and three fractional B-Modules  16 . When the fraction for B-Modules is ¾, then assembly  14  represents a total propellant zone of 5¼; i.e., 1+1+1+¾+¾+¾. Further module structure  18  is composed of two A-Modules  12  and one B-Module  16 . Additionally, Module structure  24  is composed entirely of B-Modules  16 . 
     FIG. 2 shows how modules are combined to form a system. In the preferred embodiment, an A-Module  12  and a B-Module  16  are composed by interlocking combustible case canisters  26  to thereby form a module structure  10 . An alternate embodiment shows an A-Module  12  and a B-Module  16  packaged in semi-rigid bags  27  to form the module structure  10 . 
     FIG. 3 is a graphical representation of the flight characteristics of a typical artillery projectile (the M549). A specific trajectory is a single point on this graph. The time of flight (TOF) of a projectile is indicated on the vertical axis. Each line  30  represents the set of trajectories fired at a constant quadrant elevation (the angle between the horizontal and the barrel of the gun or cannon from which the projectile is being fired). The highest and lowest practical quadrant elevation (QE) depend upon the projectile&#39;s aerodynamics and these are shown by curves  28 . 
     The solid curved lines  32  and the dotted curved lines  40  are curves of constant muzzle velocity. The muzzle velocity required for a given shot can be determined by interpolating between these lines. 
     A cannon can generally fire at any QE between its upper and lower limits, however, it can only achieve muzzle velocities defined by the zones its propellant can generate. The lines  32  represent the muzzle velocities that can be achieved with a typical system of one fixed size for the modules of charge. The line  34  represents zone  2  (consisting of two modules of charge) and the rightmost line  38  represents zone  6  (6 modules of charge) Zone  1  is not used in practice because it does not provide enough impetus to guarantee that the projectile will leave the barrel of the cannon. Other points on the graph represent shots that could be fired by some other cannon, but such shots cannot be fired by a cannon whose projectile propulsion system has zones given by the lines  30 . 
     The dotted lines  40  represent the locus of additional trajectories that can be fired by a cannon implementing the VIMAP system with modules in the ratio of 3 to 4. The dotted lines  40  lying between the zone  5  line  36  and the zone  6  line  38  represents zones of propellant powers (zones) 5¼, 5½ and 5¾. The addition of these intermediate zones substantially increases the number of different trajectories that can be fired and greatly improves the battlefield effectiveness of the cannon. 
     FIGS. 4 and 5 Tables I and II provide a sample of modular compositions between A-Modules  12  and B-Modules  16 . The tables show the total propellant power (zone) as well as the total number of units in a structure. For example, to compose a propellant power (zone) of 2 and ¾, referring to Table I, we need two A-Modules  12  and one B-Module  16 . 
     The description hereinabove relates to some of the most important features which set and determine, inter alia, the structural parameters of the present invention. The operations of the present invention, under a best mode scenario, are discussed hereinbelow. 
     Module structure  10  shown in FIG. 1 is composed of six A-Modules, the total power of the structure is defined to be zone  6 . Any shot on the zone  6  line  38  of FIG. 3 can be shot with this assembly of modules. The distance to the target and the TOF are given by the coordinates of the point along the axes. By pointing the gun low, a zone  6  shot can engage a target located 30 km away and the projectile will fly for approximately 78 seconds before impact; this is point  42  on FIG.  3 . By raising the cannon&#39;s elevation angle slightly, zone  6  can be used to shoot at a target that is 35 km distant and the projectile will fly for approximately 100 seconds. This shot is labeled  44  on FIG.  3 . Raising the cannon angle higher yet will result in a high trajectory shot like the “lob” of a tennis ball. Point  46  labels such a shot at a target that is 35 km from the gun; this zone  6  shot will fly for slightly under 140 seconds before impact. The “high” shot  46  and “low” shot  42  are both zone  6  shots at a target located 35 km away. The basic precept of the present invention includes that unitary and fractional modules may be combined to increase the number of zones that can be fired and hence increase the number of different trajectories (shots) that can be fired at a given target. A propellant system with only unitary modules is limited to the zones  32 , hence only two different trajectories (points  44  and  46 ) can be used to attack a target that is 35 km away. A VIMAP system using modules in the ratio 3:4 adds additional zones  40 . This doubles the number of trajectories that can be used to attack a target at 35 km, as the shots labeled  48  and  50  can be fired at such targets using zone 5¾. 
     FIG. 3 shows two shots ( 44  and  46 ) that can be fired at a target 35 km away using zone  6 . The “high” shot  46  flies for about 140 seconds and the “low” one  44  flies for about 100 seconds. By firing the “high” shot  46  first then lowering the gun, and then firing the “low” shot 44 forty seconds later, both shots will arrive at the target simultaneously, achieving twice the destructive power of a single shot. Missions in which several shots are fired at a single target and timed to arrive at the same time are called “Multiple Round Simultaneous Impact” (MRSI) missions. By increasing the number of zones a cannon can fire, the present invention substantially increases its ability to fire MRSI missions. 
     Referring to FIG. 3, a system of unitary charges can fire only one trajectory  42  at a target that is 30 km away; this is a zone  6  trajectory. With such a unitary system, a MRSI mission cannot be fired at a target at the 30 km range. A VIMAP system using the ration 3:4 would add three zones between 5 and 6 and permit targets at the 30 km range to be attacked using any of 5 additional trajectories  52 . With the system, a MRSI mission can be fired with the trajectories ( 52 , 42 ) timed so that six rounds would land simultaneously at the target. 
     FIG. 4, Table I shows the numerous total propellant power levels that can be composed from only two module sizes when the A-Module  12  is defined to have charge 1 and B-Module has charge ¾. FIG. 5, Table II shows the corresponding combinations when an A-Module  12  is defined to have charge 1 and a B-Module  16  has charge ⅔. Such combinations are required to permit a specific target at a specific range from the gun to be attached along several trajectories. Combustible case canisters  26  or rigid bags  27  (see FIG. 2) can be combined to form many different assemblies with varying amounts of total charge. More significantly, the canisters  26  which contain the charge of A-Modules  12  and B-Modules  16  are of the same physical dimensions. Thus, both modules use the same canister except that B-Module  16  canisters are filled with less propellant than A-Module  12  canisters. This feature provides an advantage of uniformity in physical size to thereby enable ease of manufacturing and handling. 
     The unicharge system in the current and proposed state of the art uses modules (canisters) of equal propellant power. The maximum size of an assembly of canisters depends upon the canister size and is limited by the constraints of the gun tube. One existing implementation uses assemblies of from 2 to 6 canisters, while another (using smaller canisters) uses from 2 to 8. Because the amount of propellant in a module is fixed at manufacture and because modules cannot be broken into smaller ones, this limits the number of different zones that can be fired, and amounts of propellant power equivalent to fractional module quantities are impossible. The VIMAP device and method needs modules built in only two different propellant power increments to enable the construction of assemblies with a desired level of propellant power. Under the best mode scenario declared herein, FIG. 4, Table I shows the variety of total power increments this invention provides when the module sizes are based on the integers 3 and 4. Per this table, an A-module  12  of unit propellant power and a B-Module  16  of ¾ the power of an A-Module provide nearly 4 times as many different zones (total amounts) of propellant power than existing systems which use only unitary A-Modules  16 . FIG. 5, Table II, shows the diversity and proportionality that results from a system in which the module sizes are based on the integers 2 and 3. In FIG. 5, Table II, B-Modules  16  are defined to be ⅔ the power of A-Modules  12 , and there are approximately 3 times as many zones possible than could be constructed only from A-Modules. This diversity and proportionality is because the present invention uses sequential integers to proportion and form the basis for the modules and their respective power levels. 
     The technique of composing charge assemblies from two sizes of modules manufactured so that their relative power is equivalent to the ratio of two successive integers is the key aspect of the present invention. FIG. 4, Table I, shows combinations derived from the integers 3 and 4; the power of a B-Module  16  is ¾ the power of an A-Module  12 . An equivalent way of stating the same relation is to say that an A-Module  12  is {fraction (4/3)} the power of a B-Module  16 . FIG. 5, Table II, shows combinations derived from the integers 2 and 3. In FIG. 5, the power of a B-Module  16  is ⅔ the power of an A-Module  12 . An equivalent way of stating this is that an A-Module  12  is {fraction (3/2)} the power of a B-Module  16 . Other systems of charge (not depicted) can be constructed from (for example) the integers 4 and 5, or 5 and 6, and so on. The large number of different combinations that can be achieved by this technique and the structural organizations resulting therefrom are conducive to Multiple Round Simultaneous Impact (MRSI) missions and enable variable power increments in a modular context. 
     While a preferred embodiment of the VIMAP has been shown and described, it will be appreciated that various changes and modifications may be made therein without departing from the spirit of the invention as defined by the scope of the appended claims.