Patent Publication Number: US-6334394-B1

Title: Propellant charge arrangement for barrel-weapons or ballistic drives

Description:
This application claims Paris Convention priority of DE 199 17 633.7 filed Apr. 19, 1999 the complete disclosure of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a propellant charge arrangement for barrel-weapons or ballistic drives. 
     The performance of chemically reacting propellant charges is determined essentially by the ratio of charge mass and its energy density to the mass of the object to be accelerated (projectile or rocket). One therefore always tries to match the mass of the propellant charge and its energy density to the specific case at hand. 
     In addition to conventional propellant charges, recently, arrangements comprising consolidated propellants of high energy density have been examined which are triggered by means of electrical energy, e.g. in the electro-thermal chemical cannon. Ignition and combustion of such consolidated propellants is problematic, since the charge arrangement has to be broken up and disintegrated, thereby requiring defined surfaces to achieve time-controlled ignition and combustion at high propellant charge conversion speeds. 
     This is also the case for recently examined liquid propellant charges which have to be converted into a corresponding dispersion. 
     For acceleration of projectiles in barrel-weapons, combustion of the propellant charge and acceleration of the projectile is a dynamic process which occurs within an extremely short time within which the gas evolution of the propellant charge must be matched to the mass of the projectile. One must also take into consideration the fact that, with acceleration of the projectile, the volume to be filled by the propellant increases. These overlapping processes must be matched to ensure that the projectile reaches the desired muzzle velocity. In this connection, the gas-pressure/time-curve is decisive. This is generally a Gaussian curve, i.e. the pressure increases very rapidly and exponentially to a maximum pressure and drops somewhat less steeply and exponentially with increasing acceleration of the projectile towards the muzzle. The conversion speed of the propellant charge has similar characteristics with a slightly more symmetric development of the Gaussian curve. For the drive performance, the pressure/time integral is decisive and has an upper limit given by the maximum admissible gas pressure in the charging room. The ideal case would be a trapezoidal pressure development, wherein the maximum pressure and also the muzzle pressure would be smaller, with the integral of the pressure/time curve being larger. 
     A conventional propellant charge arrangement (U.S. Pat. No. 5,612,506) comprises an electric ignition system disposed on the axis of the propellant charge room having a central rod electrode and several wire electrodes disposed at an axial distance from one another and insulated from one another. This structurally complicated electrode is surrounded concentrically by a wire basket which accommodates a powdery ignition substance, preferably polyethylene powder. The wire basket is surrounded concentrically by the oxidator, e.g. ammonium nitrate. The electrode structure should enable plasma ignition migration from the front to the rear through the propellant charge arrangement such that the propellant gas generation approximately follows the propulsion of the projectile in the barrel-weapon to result in an approximately trapezoidal pressure/time curve. Apart from the demanding and mechanically sensitive electrode construction, this propellant charge arrangement has very low energy density due to the fuel/oxidator selection and the relatively large inactive mass of the electrode structure. 
     It is the underlying purpose of the invention to provide a propellant charge arrangement consisting of a core charge and a consolidated propellant surrounding the core charge, which approximates, as closely as possible, the ideal trapezoidal development of the pressure/time curve during combustion. 
     SUMMARY OF THE INVENTION 
     This object is achieved by a propellant charge arrangement comprising a core charge of conventional construction having an ignition system and with a consolidated propellant surrounding the core charge which has its own high electrical energy ignition system which can be controlled in a delayed manner after triggering the ignition system for the core charge, wherein construction and arrangement of the consolidated propellant and its ignition system are selected such that, during combustion of the core charge, the consolidated propellant is disintegrated, by the triggering of its associated ignition system, into fragments of essentially regular geometry and the fragments are accelerated into the gas volume generated during combustion of the core charge. 
     While the core charge and its ignition system are of conventional construction, e.g. consist of a conventional gun powder which is ignited pyrotechnically or electrically, the propellant charge surrounding it comprises a consolidated propellant having its own ignition system. The core charge is initially ignited in the conventional manner and the ignition system of the consolidated propellant surrounding same is triggered in a delayed manner. The latter is an ignition system operating with high electrical energy, wherein a large amount of plasma energy is released locally e.g. by arc discharge, which can preferably be controlled in time and/or space. The consolidated propellant is thereby disintegrated into fragments in a defined sequence. Construction of the consolidated propellant and its arrangement as well as that of the ignition system can be effected such that fragments of relatively uniform geometry are generated, which consequently have relatively uniform surfaces to effect uniform ignition and combustion. With appropriate outer insulation and arrangement of the ignition system, these fragments are accelerated into the gas volume developed during combustion of the core charge and are completely transformed therein. With e.g. a barrel-weapon, the volume increase and pressure reduction due to the acceleration of the projectile are thereby immediately compensated for. This propellant charge arrangement structure reduces the maximum pressure, while maintaining the generated maximum pressure for a longer time. Instead of a peak, the pressure/time diagram has a pressure plateau with reduced pressure levels such that the projectile is accelerated with a lower gas pressure of longer duration. Moreover, the muzzle pressure is reduced without reducing the muzzle velocity. 
     The formation of fragments of essentially regular geometry can be achieved e.g. by providing the consolidated propellant with an essentially uniform design structure. This can e.g. be effected by inhomogeneities of essentially uniform geometric arrangement. When the ignition system is triggered, the consolidated propellant is broken up along the inhomogeneities and accelerated towards the inside in correspondingly uniform fragments, wherein the generated surfaces provide effective ignition and combustion. 
     With solid charges, the inhomogeneities can be formed e.g. by bordering layers between neighboring layers of the consolidated propellant. They are preferably disposed essentially linearly in a pattern. 
     A structure of this type can be realized in a particularly simple manner by arranging the consolidated propellant in at least two layers, wherein the linear inhomogeneities in one layer extend at an angle, e.g. at a right angle, with respect to the linear inhomogeneities in the other layer. In this case, the consolidated propellant comprises individual strips of propellant which are separated from one another by the inhomogeneities or bordering layers, wherein the strips of the two layers disposed one on top of the other, cross each other. 
     Disintegration of the consolidated propellant into uniform fragments can be realized or supported when the ignition system of the consolidated propellant comprises electrical conductors associated with an essentially uniform arrangement of the consolidated propellant. The energy required for disintegration and ignition is also released in a geometrically uniformly distributed manner and supports the disintegration into uniform fragments, enabled by the structured geometry of the consolidated propellant. Moreover, the energy required for uniform ignition or uniform initial combustion is supplied by this ignition system. 
     The electrical conductors can be disposed e.g. in a ladder-shaped manner, wherein the conductor configuration can taper in a trapezoidal manner depending on the arrangement and design of the overall propellant charge. 
     The conductors can be embedded in the consolidated propellant or disposed on the surface of the consolidated propellant facing away from the core charge. 
     The ignition system can be improved by at least partially surrounding the electrical conductors with a pressure-generating layer of pyrotechnical material or fine-grained propellant charge powder to increase the energy locally released at the conductors. 
     Instead or additionally, the consolidated propellant can be surrounded, at its surface facing away from the core charge, by a gas-generating layer of pyrotechnical material or fine-grained propellant charge powder, wherein the electrical conductors are preferably embedded in this layer. A further peripheral pressure component with isostatic effect is thereby generated to support disintegration and acceleration of the fragments as well as their ignition and combustion. 
     In a further embodiment, the at least two layers of the consolidated propellant have variable transparency to optimally utilize and precisely control the radiative energy generated during arc discharge. For example, that layer of the consolidated propellant into which the electrical conductors are embedded or on which they are disposed, can have a higher transparency than the subsequent layers in the direction of the core charge. 
     The arc discharges generated along the conductor paths at defined spatial and time intervals and the high temperature plasmas generated thereby, break up the structured consolidated propellant in a defined and reproducible manner such that ignition and combustion of the disintegrated consolidated propellant occurs at predetermined locations and times. This is done at a defined time following combustion of the core charge. The higher conversion speed of the consolidated propellant compensates for the volume increase during acceleration of the projectile as well as for pressure reduction in the charging room. The high gas pressures associated with high temperature plasma generation and with ignition and combustion of the consolidated propellant fragments overlap, in a time-delayed manner, with the gas pressure curve of the core charge to increase drive performance. The conversion speed can be increased by radiation transport from the high temperature plasmas and by appropriately layered transparency or radiative absorptivity. 
     The invention is described below using embodiments shown in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a perspective view of a first embodiment of the propellant charge arrangement; 
     FIG. 2 shows a sector-shaped section of the consolidated propellant of the arrangement in accordance with FIG. 1; 
     FIG. 3 shows a sector-shaped section of a further embodiment of the consolidated propellant; 
     FIG. 4 shows a detailed flat, unfolded view of the embodiment in accordance with FIG. 3; 
     FIG. 5 shows a section of a further embodiment of the consolidated propellant, similar to FIG. 3; 
     FIG. 6 shows a flat unfolded view of FIG. 5, with detailed illustration of the structure; 
     FIG. 7 shows a perspective view of a further variant of the propellant charge arrangement; 
     FIG. 8 shows a sector-shaped section of the consolidated propellant for the propellant charge arrangement of FIG. 7; 
     FIG. 9 shows a first phase of an example of use of the propellant charge arrangement in barrel-weapons; 
     FIG. 10 shows a second phase of an example of use of the propellant charge arrangement in barrel-weapons; 
     FIG. 11 shows a third phase of an example of use of the propellant charge arrangement in barrel-weapons; 
     FIG. 12 shows a pressure/time diagram of various propellant charges with separate ignition; 
     FIG. 13 shows a pressure/time diagram of the propellant charge arrangement in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The propellant charge arrangement  1  has a cylindrical shape. It comprises a core charge  2  and a consolidated propellant  3  surrounding same. The core charge  2  is of conventional construction, e.g. comprising gun powder. The core charge  2  also has an ignition system  4  comprising a centrally disposed pyrotechnical charge (in the embodiment according to FIG. 1) or in the form of an electrical system. 
     The outer consolidated propellant  3  has its own ignition system  5  comprising e.g. ladder-shaped electrical conductors  6 ,  7  which are fed with high voltage via triggered spark gaps to generate arc discharges distributed in time and space for formation of a high temperature plasma. 
     FIGS. 3 and 4 more clearly show the structure proximate the consolidated propellant. The consolidated propellant  3  is disposed inside the wall  8 , e.g. of a barrel-weapon with an intermediate insulation layer  9 . The consolidated propellant comprises two layers  10 ,  11 . The electrical conductors  6 ,  7  are disposed between the outer layer  11  and the insulating layer, peripherally on the outer layer  11 . The two layers  10  and  11  comprise linear inhomogeneities  12  or  13  generated e.g. by forming each layer  10 ,  11  from neighboring propellant strips  14  or  15 . 
     The embodiment in accordance with FIGS. 5 and 6 differs from that of FIGS. 3 and 4 only in that a pressure-amplifying layer  16 , e.g. of pyrotechnical material or propellant charge powder is disposed between the insulating layer  9  and the consolidated propellant  3  in which the electrical conductors  6 ,  7  of the ignition system are completely or partially embedded. 
     In the embodiment in accordance with FIGS. 7 and 8, the propellant charge arrangement  1  comprises a core charge  2  with ignition system  4  corresponding to the embodiment according to FIG.  1 . However, the consolidated propellant comprises liquid propellants and has an inner charge  17  and an outer charge  19  separated from each other by a bordering layer  18 . The bordering layer  18  constitutes the ignition system, having conductors  6 ,  7 . In this embodiment, the outer liquid charge  19  has a larger transparency than the inner liquid charge  17 . 
     FIGS. 9 to  11  show various phases during combustion of the propellant charge arrangement  1  in a schematically illustrated barrel-weapon. The barrel-weapon  20  comprises a barrel  21  and a charging room  22  in which the propellant charge arrangement  1  is accommodated. The propellant charge arrangement comprises the conventional core charge  2  and the consolidated propellant  3  surrounding same. A projectile  23  is disposed in the barrel and its rear extends into the propellant charge room  22 . As shown in the figure, the propellant charge room  22  has a larger inner cross-section than the cross-section of the projectile  23  and the cross-section of the core charge  2  is somewhat smaller than that of the projectile  23 . The outer cross-section of the consolidated propellant  3  is, however, larger and fills the propellant charge room. After ignition of the core charge  2  and conversion of the solid propellant into the gaseous phase  24 , the projectile  23  begins to accelerate. The outer consolidated propellant  3  is ignited in a time-overlapping, possibly sequential manner and is disintegrated into fragments, the fragments being accelerated into the gas volume  24 . At the same time, ignition and conversion of the propellant fragments of the consolidated propellant  3  begins. The projectile  23  experiences a uniform, approximately constant pressure along a relatively long path and leaves the barrel  21  with the desired high muzzle velocity at reduced muzzle pressure. 
     FIG. 12 shows the pressure-time dependence for two propellant charges of different construction, e.g. for a conventional propellant charge (curve  1 ) and for a consolidated propellant (curve  3 ). The propellant charge arrangement in accordance with the invention generates the pressure development of curve  3  and shows a marked pressure plateau  27  with a time-delayed pressure decrease having a lower maximum pressure  25  and a slightly advanced rise.