Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41A—FUNCTIONAL FEATURES OR DETAILS COMMON TO BOTH SMALLARMS AND ORDNANCE, e.g. CANNONS; MOUNTINGS FOR SMALLARMS OR ORDNANCE
  • F41A3/00—Breech mechanisms, e.g. locks
  • F41A3/02—Block action, i.e. the main breech opening movement being transverse to the barrel axis
  • F41A3/10—Block action, i.e. the main breech opening movement being transverse to the barrel axis with sliding breech-block, e.g. vertically
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41A—FUNCTIONAL FEATURES OR DETAILS COMMON TO BOTH SMALLARMS AND ORDNANCE, e.g. CANNONS; MOUNTINGS FOR SMALLARMS OR ORDNANCE
  • F41A21/00—Barrels; Gun tubes; Muzzle attachments; Barrel mounting means
  • F41A21/16—Barrels or gun tubes characterised by the shape of the bore
  • F41A21/18—Grooves-Rifling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41A—FUNCTIONAL FEATURES OR DETAILS COMMON TO BOTH SMALLARMS AND ORDNANCE, e.g. CANNONS; MOUNTINGS FOR SMALLARMS OR ORDNANCE
  • F41A21/00—Barrels; Gun tubes; Muzzle attachments; Barrel mounting means
  • F41A21/16—Barrels or gun tubes characterised by the shape of the bore
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41A—FUNCTIONAL FEATURES OR DETAILS COMMON TO BOTH SMALLARMS AND ORDNANCE, e.g. CANNONS; MOUNTINGS FOR SMALLARMS OR ORDNANCE
  • F41A21/00—Barrels; Gun tubes; Muzzle attachments; Barrel mounting means
  • F41A21/28—Gas-expansion chambers; Barrels provided with gas-relieving ports
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B14/00—Projectiles or missiles characterised by arrangements for guiding or sealing them inside barrels, or for lubricating or cleaning barrels
  • F42B14/06—Sub-calibre projectiles having sabots; Sabots therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B14/00—Projectiles or missiles characterised by arrangements for guiding or sealing them inside barrels, or for lubricating or cleaning barrels
  • F42B14/06—Sub-calibre projectiles having sabots; Sabots therefor
  • F42B14/061—Sabots for long rod fin stabilised kinetic energy projectiles, i.e. multisegment sabots attached midway on the projectile
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B14/00—Projectiles or missiles characterised by arrangements for guiding or sealing them inside barrels, or for lubricating or cleaning barrels
  • F42B14/06—Sub-calibre projectiles having sabots; Sabots therefor
  • F42B14/068—Sabots characterised by the material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B14/00—Projectiles or missiles characterised by arrangements for guiding or sealing them inside barrels, or for lubricating or cleaning barrels
  • F42B14/06—Sub-calibre projectiles having sabots; Sabots therefor
  • F42B14/08—Sabots filled with propulsive charges; Removing sabots by combustion of pyrotechnic elements or by propulsive-gas pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B5/00—Cartridge ammunition, e.g. separately-loaded propellant charges
  • F42B5/02—Cartridges, i.e. cases with charge and missile
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B5/00—Cartridge ammunition, e.g. separately-loaded propellant charges
  • F42B5/38—Separately-loaded propellant charges, e.g. cartridge bags

Definitions

• the present invention relates to an ammunition and weapon system.
• the invention relates to such a system in which a projectile is pushed by a propulsion gas resulting from the combustion of a propellant charge inside a barrel closed at one end by a breech and open at its other end.
• Firearms include all weapons that use an exothermic chemical reaction in their operation. By semantic shift, this term is often associated with tube weapons whose principle is based on the launch of a projectile inside a barrel.
• a propellant charge is ignited inside the barrel between the projectile and the breech.
• the generation of propulsion gases and their expansion propel the projectile in an acceleration phase until it leaves the barrel.
• This phase of ballistics is called interior ballistics.
• cartridge case sometimes also called a case
• ammunition the components necessary for firing (primer, propellant powder, projectile) to be brought together in a single block. called ammunition.
• the cannons have a geometry quite close to a hollow cylinder whose internal section is relatively constant over the trajectory of the projectile (except for conical cannons).
• the minimum diameter of the chamber and the barrel is the minimum diameter allowing the passage of the projectile. This is all the more true since breech-loading weapons have taken precedence over muzzle-loading weapons even if certain uses are still common (light mortars).
• the socket draws two chambers, the high pressure chamber, which contains the propellant charge, and in which the combustion takes place, and a low pressure chamber in which the expansion of the propulsion gases which push on the base of the projectile takes place.
• This construction is made necessary by the use of propellant powders which require a relatively high operating pressure so that combustion is maintained and repetitive from one ammunition to another.
• the first option is to increase the duration of the projectile propulsion phase simply by increasing the length of the barrel. This is the simplest parameter for a weapon designer to modify and, therefore, is the most used in the final phase of weapon design. Depending on the constraints governing the desired use, the length of the barrel is the subject of a compromise between the bulk of the weapon and the desired initial speed. The gain in initial projectile speed by increasing the barrel length is neither infinite nor linear, so it is sometimes necessary to resort to other tricks.
• the second option is the maximization of the pressure of the propulsion gases at the rear of the projectile through the composition of the propellant powder used, its initial geometry, the quantity of powder, etc.
• This method remains limited by the performance of the materials and manufacturing processes used in the construction of cannons that cap the maximum internal pressure. This is all the more problematic as the thermal stresses involved in each shot deteriorate the resistance of the barrel.
• the designer of the ammunition may be obliged to resort to the adoption of a lightweight projectile known as “under-calibrated”.
• the projectile which will impact the target is very elongated and has a diameter significantly less than the internal diameter of the gun which is used in order to limit its drag during the external ballistic phase and concentrate the energy on impact. to maximize terminal effects.
• devices are used to seal the guidance of the projectile in the barrel in order to contain the propulsion gases behind the projectile and maximize the thrust during the interior ballistics phase.
• the shoe is made of a low density material such as aluminum or certain polymers. It can be in one piece pressing on the rear face of the projectile (SLAP ammunition) or in several parts united around the projectile by belts and releasing it by spreading radially (APFSDS ammunition).
• the sealing function was fulfilled by a wad placed behind the projectile (at the time of paper cartridges). As the means of production improved and the geometry of cannons and projectiles became better controlled, this function was fulfilled by the tightening and deformation of the projectile (made of lead then lined with copper) in the canon. For larger caliber ammunition, it is not uncommon to see this function performed by a part surrounding the projectile called a belt. Typically, the belt is made of copper alloy or polymer to minimize friction with the barrel through a
• the main parameter allowing the maximum pressure supported by the barrel to be increased is the elastic (and breaking) limit of the material used after thermal and mechanical treatment. This limit is all the lower as it is impacted by the thermal regime of the gun during its use (repeated and close shots for machine guns and automatic cannons), but also by the limited choice of material adapted by the behavior desired in the event of obstruction (ductile behavior is preferable in order to minimize the projection of fragments in the event of destruction of the barrel).
• the invention relates to an ammunition and weapon system, in which a projectile is pushed by a propellant gas resulting from the combustion of a propellant charge inside a barrel closed at one end by a breech and open at its other end, characterized in that at least part of the propulsion gases generated by the combustion of the propellant charge pass through a nozzle bringing the propulsion gases at a supersonic speed, placed in the barrel, between the breech and the projectile, and comprising a convergent, a neck and a divergent, one following the other towards the open end of the barrel.
• the nozzle is formed inside a removable chamber relative to the barrel so as to allow the loading of the propellant charge through the rear end and the loading of the projectile through the front end of the chamber;
• the nozzle is formed inside a case forming an ammunition grouping the projectile and the propellant charge before firing;
• the projectile is positioned relative to the barrel before firing, by complementarity between the shape of a base of the projectile or of one or more sabots and a portion of the nozzle;
• the propellant charge comprises an initiator composition, a rapid combustion charge and a slow combustion charge;
• At least one part of the barrel has a conical section and in that the projectile is associated with at least one degradable shoe when it moves in this conical section part of the barrel;
• the shoe is made of a material depositing on the barrel as it moves through it, to form a thermal protection layer for it which is then evacuated;
• phase change namely liquefaction, evaporation or sublimation, of the material constituting the sabot, or which may result from a reaction of the material constituting the sabot with the propulsion gases resulting from the combustion of the propellant charge, or from the self-combustion of the hoof material, or a combination of at least two of the three processes described;
• the shoe is composed of at least one of the following materials: nitrocellulose, nitroglycerin, shellac, gum arabic, gum tragacanth, gelatin, dextrin, asphalt, polybutadienes, polyesters, polyurethanes, polyfluoroelastomers, silicones, polyvinyls, graphite, potassium , centrality, camphor, phthalate esther, nitroguanidine, nitroaminoguanidine, triaminoguanidine nitrate, N - butyl - N (2 nitroxyethyl) nitramine;
• the barrel comprises a part of conical section, followed by a part of rifled straight section, the guidance of the projectile being carried out by the sabot in the conical section of the barrel and by direct contact between the projectile and the barrel in the straight section of this one.
• Figure 1 represents a sectional view of an embodiment of a system according to the invention with an ammunition in the firing position;
• Figure 2 represents a sectional view of this system according to the invention with the ammunition fired
• Figure 3 represents a sectional view on an enlarged scale of a part of this system according to the invention.
• FIG 4 shows a sectional view on an enlarged scale of a part of another embodiment of a system according to the invention with ammunition in the loading position;
• Figure 5 shows a sectional view on an enlarged scale of a part of this other embodiment of the system according to the invention with fired ammunition;
• Figure 6 represents a sectional view of an embodiment of a munition of a system according to the invention.
• This system actually uses a sub-caliber projectile guided by at least one degradable sabot inside a barrel of which at least part has a conical section.
• I designates the breech of a cannon
• - 2 designates a combustion chamber which can be removable relative to the barrel so as to allow the loading of a propellant charge through the rear end and the loading of a projectile through the front end of the chamber,
• - 3 designates a nozzle with a convergent 3a, a neck 3b and a divergent 3c, one after the other towards the open end of the barrel,
• - 4 designates the barrel with a portion of conical section 4a and a portion of straight section, for example rifled 4b,
• - 7 designates a projectile with a projectile base 7a and a projectile warhead 7b
• the caliber of the projectile is then consistent with the diameter of the barrel at the muzzle of the latter, but the internal diameter of the barrel near the chamber is significantly greater than the caliber of the projectile to accommodate the passage of the sabot.
• the sabot is not so much a part in itself as a degradable joint between the projectile and the barrel. It will be gradually trimmed as the projectile passes through the portion conical shape of the barrel by the variation in the diameter of the barrel then degraded by the temperature of the propulsion gases pushing on the base of the projectile.
• the goal is that in addition to carrying out the functions of guiding the projectile in the barrel, sealing between the barrel and the projectile, and maximizing the thrust surface of the propulsion gases during the internal ballistics phase, the transfer in the manner forming the degradable sabot on the internal face of the conical portion of the barrel produces a protective layer making it possible to limit, at least in part, the thermal transfers between the propulsion gases and the barrel.
• This functionality is obtained by the degradation of the material acting as a degradable shoe at a temperature lower than that of the propulsion gases.
• the material chosen for the degradable clog must therefore meet a certain number of criteria.
• the density of the material used as well as the quantity of material used must allow the surface mass of the sabot to be lower than that of the projectile alone so that the undercalibration of the ammunition results in an improvement in performance. mouth.
• the mechanical strength of the sabot material must be sufficient to allow the transmission of the additional thrust to the projectile, but also sufficiently low so that friction against the internal wall of the barrel causes ablative wear of the sabot.
• the combustion of the residues resulting from the deterioration of the sabot during firing must be as complete as possible and therefore take place while the projectile has not yet left the barrel.
• the combustion temperature of the sabot material must be as low as possible in order to maximize the thermal protection of the barrel.
• the shoe is composed of at least one of the following materials: nitrocellulose, nitroglycerin, shellac, gum arabic, gum tragacanth, gelatin, dextrin, asphalt, polybutadienes, polyesters, polyurethanes, polyfluoroelastomers, silicones, polyvinyls , graphite, potassium, centrality, camphor, phthalate esther, nitroguanidine, nitroaminoguanidine, triaminoguanidine nitrate, N - butyl - N (2 nitroxyethyl) nitramine.
• the variation in barrel diameter is continuous, progressive, but not necessarily linear.
• a final portion of the barrel, at the muzzle, can have the diameter necessary to rest directly on the projectile and give it a rotation necessary for its gyroscopic stabilization.
• the master torque of the projectile (maximum surface area of the projectile section along its main axis) is a key parameter in each of the phases of the ballistic, but has an inverse influence during interior ballistics and exterior ballistics.
• a strong master torque allows greater acceleration of the projectile due to the large surface area on which the pressure of the propulsion gases is applied.
• a strong master torque also considerably increases the drag force to which the projectile will be subjected during the external ballistic phase, which increases the energy loss, particularly for distant targets.
• a projectile with a low master torque will lose less energy during the free flight phase.
• the propulsion phase of this projectile will be negatively affected by this choice, which will limit the initial speed of the projectile.
• the other large family of solutions for sub-calibration of the ammunition is the use of a so-called “sabot” munition where the projectile with low master torque is enclosed by a sabot providing sealing with the barrel during the phase. interior ballistics.
• the main advantage of this solution lies in the use of a significant master torque over the entire length of the barrel which maximizes the thrust on the projectile until it exits the barrel.
• this process also affects the efficiency of the propulsion, because part of the energy is used to accelerate the sabot, the mass of which can be of the order of 30% of the mass of the projectile.
• the sabot system is rarely used in conjunction with a rifled barrel.
• the non-concentricity of the projectile in the sabot causes a precession movement which will only be damped by the presence of a stabilizing tail moving the center of drag to the rear of the center of gravity of the projectile. Consequently, sabot ammunition is most often used in conjunction with a smoothbore cannon, the projectile being mainly stabilized by a tail having a certain incidence in relation to the axis of the projectile in order to grant it additional gyroscopic stability via the rotation of the projectile in the initial phase of external ballistics (transient ballistics).
• sabot technologies are implemented: a monolithic sabot pushing the projectile from the rear and positioning the projectile via lateral petals which will move apart when exiting the barrel.
• SLAP Stimble Light Armor Penetrator
• the other solution consists of several sabots taking the form of a portion of a hollow piece of revolution which surrounds the projectile laterally. The sabots separate from the projectile upon exiting the barrel under the effect of aerodynamic forces and inertia.
• the resulting ammunition is designated APDS for “Armor Piercing Discarding Sabot” when the projectile is without a stabilizing tail, and APFSDS for “Armor Piercing Fin-Stabilized Discarding Sabot” when the stabilization of the projectile is obtained by a rear tail.
• a solution like that proposed by the invention consisting of a mixture between these two solutions is not one of the options likely to be retained during the design of a new weapon due to the accumulation of disadvantages (reduction of the thrust surface as the projectile advances in the barrel and increase in the mass propelled by a sabot mass) without there being any accumulation of advantages.
• disadvantages reduction of the thrust surface as the projectile advances in the barrel and increase in the mass propelled by a sabot mass
• the conicity of the barrel reduces the thrust surface of the combustion gases on the base of the projectile
• the adoption of a sabot reduces the thrust efficiency by the addition of a propelled mass whose energy is not transmitted to the target.
• the new idea lies in no longer considering that the sabot has a fixed mass, but that its mass can decrease as it advances in the barrel from the moment when this sabot is made of a material capable of degrading/eroding on the barrel walls.
• the material which will be detached from the sabot by its abrasion inside the conical barrel then forms a layer on the internal wall of the barrel.
• This layer must be evacuated, preferably between each shot, so that the performance of the weapon is constant over time. If the risk of obstruction is relatively low, pronounced fouling of the barrel is considered a negative point for the maintenance of a weapon, in particular when the weapon operates repeatedly via an automation using gas borrowing in the barrel. Thus, it becomes necessary to manage the evacuation of the sabot in a form other than a support for the projectile.
• One solution is to choose the material constituting the sabot as indicated previously, giving it the properties necessary for its evacuation in the form of gas at the same time as the propulsion gases resulting from the combustion of the propellant charge. This implies that the material used for the degradable sabot must have a vaporization or sublimation temperature lower than the temperature of the propulsion gases during firing. A lot of polymers fall into this category, waxes are also quite good candidates.
• the material of the degradable sabot interact with the propulsion gases resulting from the combustion of the propellant charge in the form of a chemical reaction (acid-base or redox).
• the oxygen balance of the propellant charge may be large enough for the excess oxygen to react with the material making up the degradable sabot to form a gas which mixes with the propulsion gases and will therefore be evacuated like the latter.
• Materials with properties conducive to this type of strategy are polymers composed mainly of carbon chains, graphite, etc. Materials that are difficult to oxidise or whose oxidation residues are not in the gaseous state at the temperature and at the pressure present in the barrel are not good candidates for the manufacture of a degradable sabot.
• the advantage is that the combustion of the material serving as a degradable sabot, then as a protective layer, is ensured by exposure to the temperature and pressure of the propulsion gases.
• the energy contained in the degradable sabot is added to that of the propellant charge in the form of an increase in the quantity of gas of propulsion in the barrel behind the projectile as well as an increase in the temperature of the propellant gases in the barrel.
• the weapon designer will be able to allow a certain reduction in the wall thickness of the barrel in order to reduce the mass of the weapon, the removal of a rapid barrel replacement system (generally present on infantry machine guns) or an increase in the firing rate acceptable if weapon mass is not an issue.
• a rapid barrel replacement system generally present on infantry machine guns
• weapons combining high power of each shot and precision are generally already equipped with long and large diameter barrels. Thus there is no particular penalty for these weapons due to the adoption of a degradable sabot ammunition associated with a barrel with moderate conicity.
• the evacuation of the protective layer of the barrel is for example obtained:
• phase change namely liquefaction, evaporation or sublimation, of the material constituting the sabot, or which may result from a reaction of the material constituting the sabot with the propulsion gases resulting from the combustion of the propellant charge, or from the self-combustion of the hoof material, or a combination of at least two of the three processes described.
• Another constraint to take into account is the need to keep the projectile coaxial with the barrel while it is accelerated by the sabot in the conical section of the barrel.
• the concentricity of the projectile in the barrel does not pose a particular problem, because breaking the contact on one side of the barrel automatically causes an imbalance in the radial forces of the barrel on the degradable sabot which will be redirected towards an equilibrium position in the center of the barrel. canon. In this case, it is the taper of the barrel which ensures the permanent refocusing of the projectile in the barrel.
• the front faces and rear are significantly more resistant than the heart of the hoof.
• the phenomenon of recentering of the projectile in the barrel applies independently to the front of the degradable sabot and to the rear of the degradable sabot, which ensures the coaxiality of the projectile in relation to the barrel.
• the condition of coaxiality of the projectile in the barrel lies in the positioning behind the center of gravity of the assembly projectile and degradable sabot in relation to the contact zone between the sabot and the barrel. Indeed, if this condition is met, when the projectile is no longer coaxial with the barrel, the center of gravity of the projectile and degradable sabot assembly shifts towards the "advanced" side due to the rotation of the assembly. projectile and degradable sabot around the center of the guidance.
• the distribution of the mass of the projectile and degradable sabot assembly on the thrust surface of the propulsion gases is modified with a greater mass on the "ahead” side and a lesser mass on the "lagging” side.
• the thrust pressure of the propulsion gases being relatively uniform, the acceleration on the “lagging” side will be greater than that on the “leading” side, which will have the effect of returning the projectile to a coaxial position with the gun.
• the appropriate shape for the base of the degradable sabot to fulfill this last condition of stability is quite close to a cone pointing towards the breech of the weapon.
• This shape makes it possible to satisfy the condition of coaxiality by short guidance when the master torque of the barrel is important (close to the breech) and to gradually move to long guidance as the diameter of the degradable shoe decreases by the taper of the barrel.
• this shape can be complementary to a nozzle shape as described below. Two obvious advantages can be gained from this configuration.
• the first advantage concerns the rigidity of the ammunition for guiding and chambering the ammunition in the barrel. Indeed, it is thus possible to reduce the transmission by the degradable sabot of lateral forces on the tip of the projectile during these operations by working the shape of the base of the projectile so that there is contact between the base of the projectile. projectile and the neck and/or the divergent part of the nozzle of the case.
• the second advantage of this configuration relates to the industrialization of the ammunition. Indeed, in a configuration where the base of the projectile is in contact with the neck and/or the divergent of the nozzle of the case, the production of the degradable sabot is possible by injection of the material selected for the degradable sabot into an impression positioning the projectile and being closed by the case.
• Another point of the system according to the invention relates to the presence, during the thrust phase of the internal ballistics, of a separation between the chamber, place of combustion of the propellant charge, and the projectile. This separation is achieved by means of a nozzle allowing gases to pass at supersonic speed inside the barrel. To do this, several architectures are possible depending on the nature of the desired weapon and the accepted disadvantages:
• the nozzle can be permanently fixed and formed directly by the barrel.
• the propellant charge can be placed through the muzzle of the gun if the propellant charge is in the form of a powder fine enough to enter the chamber through the nozzle and the neck.
• the propellant charge is introduced into the chamber through the breech in the form of pellets or a blank cartridge.
• the projectile is always introduced through the muzzle of the cannon. All types of conventional or under-calibrated projectiles are compatible with these configurations.
• the weapon is necessarily exclusively powered by the breech
• two solutions are available to the weapon designer: the separate loading of the propellant charge in the chamber and the projectile in the barrel on the one hand, or the integration of the nozzle inside the case without any particular modification to be made to the weapon.
• This last configuration is favored because of its practicality for loading operations, evacuation of shooting waste, unloading the weapon or cleaning the system.
• the nozzle can be formed inside a removable chamber relative to the barrel so as to allow the loading of the propellant charge through the rear end and the loading of the projectile through the front end of the chamber or this nozzle can be formed inside a case forming an ammunition grouping the projectile and the propellant charge before firing.
• the projectile can be placed inside the ammunition case by complementarity between the shape of a base of the projectile or of one or more sabots and a portion of the nozzle as long as the ammunition is assembled.
• Modeling the internal ballistics of firearms is well known and is based on a set of equations making it possible to determine the evolution of certain parameters in order to deduce the evolution of the speed and position of the projectile during firing.
• One of these equations represents the energy balance inside the gun and highlights the partial transfer of the energy released by the propulsive charge into kinetic energy of the projectile.
• the two phenomena limiting the transfer of energy are none other than the non-transformation of part of the thermal energy of the propulsion gases (which acts as a form of potential energy reserve allowing the continuation of propulsion of the projectile in the barrel, while the combustion of the propellant charge is completed), and the setting in motion of the propulsion gases (energy which is lost).
• the static pressure exerted on the internal walls of the barrel is linked to the static pressure at the breech as well as to the speed of the propulsion gases at the location of the barrel considered.
• the barrel is made of a tube whose wall thickness is often quite close to, or even greater than, the diameter of the projectile. This implies that the internal stress bearable by the barrel during a shot is less and less correlated with the increase in the external diameter of the tube (hypothesis of thin hollow cylinders), but that the limiting factor becomes the limit to the breakage of the material used for the core of the barrel.
• the limit on the maximum operating pressure of ammunition is directly linked to innovation in the field of high toughness materials, including at high temperatures, and whose failure mode is compatible with the safety of the weapon. Indeed, in the event of obstruction, a barrel which bursts (which opens according to a crack without creating and dispersing fragments) is preferable to bursting behavior (brittle rupture with projection of shards).
• the device which allows the transition between a high pressure tank on the side of the breech (which we call chamber) and the barrel, where the pressure is lower and the speed of the propulsion gases is particularly high, is not nothing but a nozzle. This is characterized by a neck, the narrowest passage through which the propulsion gases pass, a convergent accelerating the propulsion gases to a sonic speed and a divergent bringing the propulsion gases to a supersonic speed.
• the entire propellant charge is in the chamber which is closed by the neck of the nozzle and the projectile.
• a priming phase begins which can be modeled in the same way as the internal ballistics of a traditional firearm of the same type. It is nevertheless necessary to take into account the pressure loss as the nozzle passes.
• the end of the priming phase is characterized by a speed of passage of the propulsion gases through the neck at the speed of sound in this same gas.
• a shock wave is created at the neck and decouples the chamber, where a strong static pressure reigns forcing the combustion of the still unburned powder, from the barrel, in which the nozzle ejects the product of the combustion of the propellant charge at supersonic speed and lower static pressure.
• propulsion gases are compressed again at the base of the projectile which thus continues its propulsion phase in the barrel.
• the pressure applying on the internal walls of the barrel is significantly lower than the pressure exerted in the chamber, with a distribution passing through a minimum at the exit of the nozzle and a progressive recompression towards the pressure at the base of the projectile .
• the projectile can then be placed inside the ammunition case by complementarity between the shape of a base of the projectile or of one or more sabots and a portion of the nozzle as long as the ammunition is assembled.
• the construction and operating constraints of the barrel - ammunition pair mean that the thickness of the material of the barrel is significantly greater on the breech side than on the muzzle side of the barrel. In fact, it is often easier, and less costly in terms of performance, to reinforce the chamber than the entire barrel.
• the reduction in static pressure inside the barrel is also accompanied by a reduction in the temperature of the gases in the barrel.
• the sabot technique is as well suited as the deformable projectile technique in a conical barrel. It should be noted, however, that the degradable sabot projectile technique accelerated by a conical barrel offers certain synergies if it is combined with the adoption of a nozzle in the barrel.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)

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• 2022
  • 2022-05-23 FR FR2204909A patent/FR3135778B1/fr active Active
• 2023
  • 2023-05-22 EP EP23728694.3A patent/EP4529607A1/de active Pending
  • 2023-05-22 IL IL317165A patent/IL317165A/en unknown
  • 2023-05-22 KR KR1020247039017A patent/KR20250036063A/ko active Pending
  • 2023-05-22 WO PCT/EP2023/063569 patent/WO2023227496A1/fr not_active Ceased
  • 2023-05-22 US US18/867,514 patent/US20250383173A1/en active Pending

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