Abstract:
The invention relates to an ammunition comprising an explosive charge confined in a compartment and a deconfinement device capable of deconfining the explosive charge under a pressure or temperature rise within the ammunition. The invention neutralizes the ammunition on command. According to the invention, the ammunition further includes means for activating the deconfinement device, these means being controllable.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to foreign France patent application No. 0903515, filed on Jul. 17, 2009, the disclosure of which is hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The invention relates to an ammunition comprising an explosive charge confined in a compartment and to a deconfinement device capable of deconfining the explosive charge through the effect of a rise in pressure or temperature within the ammunition. The invention applies notably to the in-flight neutralization of ammunitions. 
       BACKGROUND OF THE INVENTION 
       [0003]    In current conflicts, armed forces are often near civilian areas, or even based in areas of civilian habitation. To avoid collateral damage, in particular to prevent the risk of harming civilian populations, modern ammunitions are becoming increasingly sophisticated. Ammunitions may notably be designed to cause damage over a relatively limited perimeter and may also be provided with guiding means. Guiding generally results in better impact precision. It therefore makes it possible to destroy a target with a limited risk of hitting the neighbouring environment. The ammunition may be guided by a ground guiding system or by a device incorporated into the ammunition. A ground guiding system makes it possible to redirect the ammunition if it is sufficiently anticipated. A redirection may be necessary for example if the target has moved or if the objective has been changed. However, an ammunition incorporating a guiding device generally becomes completely autonomous after it has been launched. It is then no longer possible to modify the target. Whatever the type of guiding, safety problems arise in several circumstances. For example, the ammunition may adopt an aberrant trajectory, that is to say a trajectory not enabling it to reach its target. The ammunition may also encounter an obstacle in its path. Finally, the mission may have to be abandoned for various reasons, notably should the presence of civilians near the target be discovered after the ammunition has been launched. These safety problems create a need to be able to neutralize an ammunition after it has been launched. The expression “neutralize the ammunition” is understood to mean the ability to prevent its explosive charge from exploding, that is to say to prevent it decomposing in a few microseconds. Furthermore, the capability of neutralizing an ammunition may also prove necessary even if the ammunition has not been launched. 
         [0004]    The neutralization of an unlaunched ammunition is for example of interest when the place where it is stored is threatened with an attack. It is then desirable for the ammunition, which may be close to allied military forces, to be prevented from exploding. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention notably provides a solution for neutralizing, on command, an ammunition, whether or not it has been launched. For this purpose, the subject of the invention is an ammunition comprising an explosive charge confined in a compartment and a deconfinement device capable of deconfining the explosive charge under a pressure or temperature rise within the ammunition, characterized in that it includes means for activating the deconfinement device, said means being controllable. 
         [0006]    The invention notably has the advantage that the explosion of the ammunition may be prevented at any moment before its impact. In particular, even if it is impossible to turn the ammunition away from its target, the invention enables it to be made less destructive. In addition, if the ammunition has already been fitted with a deconfinement device, very few structural modifications are necessary in order to make it in accordance with the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention will be better understood and other advantages will become apparent on reading the detailed description of an embodiment given by way of example, the description being accompanied by the appended drawings which show: 
           [0008]      FIG. 1 , an example of an ammunition according to the invention in a partial sectional view in a longitudinal plane thereof, the ammunition being in the safety position; and 
           [0009]      FIG. 2 , the ammunition of  FIG. 1  in the same view as in  FIG. 1 , the ammunition being in the aligned position. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  shows an example of an ammunition according to the invention in a partial sectional view in a longitudinal plane thereof. In this figure, the ammunition is in the safety position.  FIG. 2  shows the same ammunition example as that of  FIG. 1  in which the ammunition is in the aligned position. For the rest of the description, the ammunition is considered to be a rocket. However, the invention applies to any type of ammunition that contains an explosive charge, notably missiles and projectiles. The rocket  1  comprises a body  2  of elongate shape and a safety and arming device  3  lying along the extension of the body  2 . The safety and arming device  3  is assembled at one of its ends to the body  2 , so as to form a cap, and at another end to a propulsion unit (not shown) capable of delivering a thrust in order to propel the rocket  1 . The body  2  and the safety and arming device  3  form a sealed casing  4  defining a compartment  5 . The compartment  5  contains an explosive charge  6 . The safety and arming device  3  comprises a pyrotechnic priming chain  7  capable of triggering the explosion of the explosive charge  6 . The pyrotechnic priming chain  7  comprises for example a rotor  8 , a detonator  9  and a pyrotechnic relay  10 . The detonator  9  is mounted on the rotor  8  so as to be able to come into alignment with a first end of the pyrotechnic relay  10 , as shown in  FIG. 2 , by a rotational movement of the rotor  8 . A second end of the pyrotechnic relay  10  opens into the compartment  5  so as to be able to trigger the explosion of the explosive charge  6 . In  FIG. 1 , the pyrotechnic priming chain  7  is represented in what is called the safety position, also called the misaligned position in so far as the detonator  9  is not aligned with the pyrotechnic relay  10 . In this position, triggering the detonator  9  does not operate the pyrotechnic relay  10 . Thus, even should the detonator  9  be accidentally triggered, there is no risk of the rocket  1  exploding. The rocket  1  also includes a deconfinement device  12 . The deconfinement device  12  allows the explosive charge  6  to be deconfined from its compartment  5  for the purpose of preventing a violent reaction of the explosive charge  6  when it reaches its decomposition temperature. The deconfinement device  12  falls within the context of the MURAT label, in which MURAT is the French acronym for “munition à risques atténués”, meaning low vulnerability ammunition. A low vulnerability ammunition is an ammunition which satisfies the requirements in terms of performance, availability and operation and for which the probability of inopportune initiation, together with the violence of the reaction and the collateral damage that would result when the ammunition is accidentally actuated, is reduced to the minimum. In particular, the deconfinement device  12  makes the rocket  1  insensitive to thermal attack, such as fires and external heating that may occur accidentally on the site where the rocket is stored. The deconfinement device  12  comprises for example assembly pins  121 ,  122  that couple the body  2  to the safety and arming device  3 . These pins  121 ,  122  are designed to rupture under a pressure or temperature rise within the compartment  5 . Should the pins  121 ,  122  rupture, the body  2  and the safety and arming device  3  are decoupled, the sealing between the casing  4  and the compartment  5  being lost. Any rise in internal pressure is then prevented. The deconfinement device  12  may for example make use of the change in phase (solid phase to liquid phase) of the explosive charge  6  when its temperature increases. The phase change means that the density of the explosive charge  6  decreases and therefore the pressure in the compartment  5  increases. This pressure generates a thrust force that ruptures the pins  121 ,  122 . The pins  121 ,  122  may also be ruptured by initiating the decomposition of the explosive charge  6 . Decomposition of the explosive charge  6  is accompanied by substantial gas generation. The gases then cause the pressure rise necessary for mechanically rupturing the pins  121 ,  122 . After such a rupture, the explosive charge  6 , or its decomposition gases, may escape freely and prevent an internal pressure rise. The explosive charge  6  may possibly continue to decompose, but without an increase in pressure. Therefore, there is no risk of the decomposition reaction getting out of control. The rocket  1  is deactivated. In the example described with reference to  FIG. 1 , the deconfinement device  12  comprises assembly pins  121 ,  122 . Of course, any other mechanical link having a predetermined point of rupture may be envisaged for coupling the body  2  to the safety and arming device  3  without departing from the scope of the invention. More generally, the deconfinement device  12  may be any means for destroying the sealing of the compartment  5 . 
         [0011]    According to the invention, the rocket  1  comprises controllable means for activating the deconfinement device. These means consist of technical means for intentionally activating the deconfinement device  12  in response to a command by an operator or a controller. They comprise for example an igniter  14  and a powder charge  15 . The term “igniter” is understood to mean any device capable of producing a flame, hot gases and/or hot particles allowing the combustion of a powder charge. In one particular embodiment, the powder charge  15  is placed in the compartment  5  with the explosive charge  6 . This embodiment enables the temperature and pressure to rise within the compartment  5  both directly, by the combustion of the powder charge  15 , and indirectly, by slow decomposition of the explosive charge  6  caused by the combustion of the powder charge  15  in the vicinity thereof. It should be noted that not all types of explosive charge decompose with the combustion of a powder charge. The pressure rise is then due only to the combustion of the powder charge  15 . This pressure rise in the compartment  5  enables the deconfinement device  12  to be activated. In the example shown in  FIGS. 1 and 2 , the pressure rise generates forces tending to shear the pins  121 ,  122  in the same way as if the rocket  1  were subjected to accidental thermal heating. 
         [0012]    According to one particular embodiment, shown notably in  FIGS. 1 and 2 , the means for activating the deconfinement device furthermore include a channel  16  capable of connecting an outlet of the igniter  14  to the powder charge  15 . This channel  16  enables the flame, the hot gases and/or the hot particles to be guided right to the powder charge  15 , notably when the igniter  14  is not located in the immediate vicinity of the powder charge  15 . The igniter  14  is for example fitted into the safety and arming device  3 . Advantageously, the channel  16  includes a non-return valve  17  that opens to allow the flame, hot gases and/or hot particles to flow to the powder charge  15 . In the closed position, said valve seals the casing  4  and therefore allows the pressure to rise inside the compartment  5 . 
         [0013]    In an alternative embodiment, the igniter  14  is mounted on the rotor  8 . It is preferably mounted so that its outlet comes into alignment with one end  161  of the channel  16  at the same time that the detonator  9  comes into alignment with the pyrotechnic relay  10 . This alternative embodiment allows a mission in flight to be rapidly abandoned. This is because when an ammunition is in flight, the detonator  9  and the pyrotechnic relay  10  are aligned. The deconfinement device  12  may thus be activated without having to modify the position of the rotor  8  beforehand. 
         [0014]    According to one particular embodiment (not shown), the means for activating the deconfinement device comprise means for detecting that the trajectory actually followed by the rocket  1  is deviating from a predetermined trajectory. These means may be only partly installed in the rocket  1 . This is for example the case when the actual trajectory of the rocket  1  is tracked by a radar or with the aid of a global navigation satellite system, such as a GPS (global positioning system) device. If it is detected that the rocket  1  is following a trajectory incompatible with its objective, the rocket  1  can then be neutralized by the means for activating the deconfinement device  12 . 
         [0015]    According to another particular embodiment, the means for activating the deconfinement device comprise means for receiving a rocket neutralization command, this command being issued remotely. Said means may for example be a radio receiver capable of receiving a signal transmitted by an operator or a controller.