Patent Publication Number: US-2020291898-A1

Title: Auxiliary booster with optimised architecture

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to the field of solid propellant boosters, and more particularly, auxiliary boosters intended to be attached to the main body of a launcher. 
     As illustrated in  FIG. 1 , an auxiliary booster  10  comprises a shell  11  having a cylindrical shape extending in a longitudinal direction between a rear face  12  in communication with a nozzle  13  and a closed front face  14 . The shell  11 , which constitutes the reservoir of the auxiliary booster, contains a solid propellant charge  17 , an initiation device  18  being present at the front face  14  of the shell. The front face  14  of the shell  11  is covered with a cap or conical structure  15  which ensures aerodynamic protection of the front face. The cap  15  is attached to the shell  11  by means of a skirt  16  applied to the front face of the shell. 
     Document U.S. Pat. No. 5,131,610 discloses an auxiliary booster of this type. The connection between the skirt  16  and the front face of the shell 
       11 , on the one hand, the connection between the cap  15  and the skirt  16 , on the other hand, must have excellent mechanical strength in order to resist the aerodynamic loads to which the auxiliary booster is subjected. These parts, as well as their connections, are costly and complex to implement. 
     Thus there exists a need for solid propellant auxiliary boosters having reduced manufacturing costs. 
     OBJECT AND SUMMARY OF THE INVENTION 
     This aim is achieved thanks to a solid propellant auxiliary booster intended to be attached to the main body of a launcher, the booster comprising a cylindrical body extending in a longitudinal direction between a rear face in communication with a nozzle and a front face formed by a conical structure connected to the cylindrical body of the booster, the cylindrical body delimiting a first internal volume and the conical structure of the front face delimiting a second internal volume, said auxiliary booster containing a solid propellant charge, characterized in that the first internal volume of the cylindrical body communicates with the second internal volume of the conical structure, in that the solid propellant charge is present both in the first and second internal volumes and in that the auxiliary booster also comprises an ignition device of the solid propellant charge present at the rear face of said auxiliary booster. 
     In producing a conical structure in the continuation of the cylindrical body of the booster, the architecture of the front portion of the booster is greatly simplified, in particular because it is no longer necessary to apply a skirt to ensure the connection between the body of the booster and the aerodynamic protection element, nor to have to manage delicate connections between three elements (booster shell, skirt and cap). 
     In addition, by combining the internal volume of the cylindrical body with the internal volume of the conical structure, the solid propellant charging capacity of the auxiliary booster is increased. Consequently, for a given charge volume, it is possible to produce auxiliary boosters with smaller dimensions and to thus further reduce their manufacturing cost. 
     Moreover, placing an ignition device for the solid propellant charge at the rear face of the auxiliary booster allows optimizing the charge volume in the assembly formed by the cylindrical body and the conical structure. 
     According to one embodiment of the auxiliary booster of the invention, the cylindrical body and the conical structure of the front face are of metallic material. 
     According to another embodiment of the auxiliary booster of the invention, the cylindrical body and the conical structure of the front face are of organic matrix composite material. 
     The invention also has as its object a manufacturing method of a solid propellant auxiliary booster intended to be attached to the main body of a launcher, the booster comprising a cylindrical body extending in a longitudinal direction between a rear face in communication with a nozzle and a front face formed by a conical structure connected to the cylindrical body of the booster, the cylindrical body delimiting a first internal volume and the conical structure of the front face delimiting a second internal volume, said auxiliary booster containing a solid propellant charge, characterized in that the method comprises the production of an assembly comprising the cylindrical body and the conical structure forming the front face of the booster, the first internal volume of the cylindrical body communicating with the second internal volume of the conical structure, in that the solid propellant charge is present both in the first and second internal volumes, and in that an ignition device of the solid propellant charge is placed at the rear zone of said auxiliary booster. 
     According to one embodiment of the invention, the assembly comprising the cylindrical body and the conical structure of the front face is produced of metallic material, the conical structure being attached by welding or brazing or other mechanical connection to the upstream end of the cylindrical body. 
     According to one particular feature of the method of the invention, each of the cylindrical body and the conical structure of the front face are charged with solid propellant before or after their assembly. 
     According to one particular feature of the method of the invention, the cylindrical body is produced by assembly of a plurality of cylindrical shroud segments, each segment being charged with solid propellant before or after its assembly with another segment. 
     According to another embodiment of the invention, the assembly comprising the cylindrical body and the conical structure of the front face is produced in organic matrix composite material. The cylindrical body and the conical structure can be produced together, i.e. in a single piece. The cylindrical body and the conical structure can also be produced separately and then assembled together, the cylindrical body and the conical structure being able to be charged with solid propellant before or after their assembly. The cylindrical body can also be produced from shroud segments manufactured independently of one another and then assembled, the segments being able to be charged with solid propellant before or after their assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will be revealed by the following description of particular embodiments of the invention, given by way of non-limiting examples, with reference to the appended drawings, in which: 
         FIG. 1  is a schematic section view of an auxiliary booster according to the prior art, 
         FIG. 2  is a schematic section of an auxiliary booster conforming to one embodiment of the invention, 
         FIGS. 3A to 3D  show the manufacturing steps of the auxiliary booster of  FIG. 2 , 
         FIG. 4  shows a manufacturing alternative of the booster of  FIG. 2 , 
         FIG. 5  is a schematic section of an auxiliary booster conforming to an embodiment of the invention, 
         FIGS. 6A to 6D  show the manufacturing steps of the auxiliary booster of  FIG. 4 , 
         FIG. 7  shows a manufacturing alternative of the booster of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 2  shows an auxiliary booster  100  conforming to an embodiment of the invention. The auxiliary booster  100  comprises a cylindrical body  110  extending in a longitudinal direction X-X′ between a rear zone or portion  120  which, in the example described here, is in communication with a nozzle  130  and a front face  140  formed by a conical structure  150  connected to the cylindrical body  110  of the booster. 
     In this embodiment, the cylindrical body  110  and the conical structure  150  forming the front face  140  are produced of metallic material, for example steel or titanium or aluminum. 
     The cylindrical body  110  delimits a first internal volume  111  while the conical structure  150  of the front face  140  delimits a second internal volume  151 . In conformity with the invention, the first internal volume  111  of the cylindrical body  110  communicates with the second internal volume  151  of the conical structure  150 . Still in conformity with the invention, a solid propellant charge  160  is present both in the first and second internal volumes  111  and  151 . In other words, in the present invention, the shell of the reservoir of the auxiliary booster is constituted both by the cylindrical body  110  and the conical structure  150  of the front face  140  which form together (combination of the first and second internal volumes  111  and  151 ) a common volume occupied by the solid propellant charge  160 , differing from the auxiliary boosters of the prior art like that described in document U.S. Pat. No. 5,131,610, in which the shell forming the solid propellant reservoir is closed at the front face of the cylindrical body, preventing communication between the internal volume of the cylindrical body and the conical structure applied to the front face of the auxiliary booster. 
     One layer of a thermal protection material  102  is present on the internal surface of the cylindrical body  110  and of the conical structure  150 . 
     The solid propellant charge  160  includes a central channel  161  extending in the longitudinal direction X-X′ and forming a combustion chamber as well as a duct for circulating the hot gases originating in the combustion of the propellant in the direction of the nozzle  130 . 
     In the example described here, the propellant charge  160  is present in particular in the entire internal volume  151  of the conical structure, i.e. from the rear end  152  until the front end  153  of the conical structure  150 . Still in the example described here, the central channel  161  present in the solid propellant charge  160  is interrupted at an intermediate position located between the rear end  152  and the front end  153  of the conical structure  150 . 
     The central channel can also extend until the front end  153  of the conical structure  150 . 
     The booster  100  also comprises an ignition device  170  for the solid propellant charge  160  present inside the cylindrical body in proximity to the rear zone  120  of the booster. 
     The booster  100  can also comprise a rear coupling device (not shown in  FIG. 2 ) which, depending on the specific design of the auxiliary booster, is located at the skirt of the rear zone or the lower portion of the cylindrical body  110  and a front coupling device (not shown in  FIG. 2 ) which, depending on the specific design of the auxiliary booster, is located at the conical structure  150  or the upper portion of the cylindrical body  110 . The coupling devices are intended to allow the attachment of the auxiliary booster to the main body of a launcher (not shown in  FIG. 2 ). 
     As illustrated in  FIGS. 3A to 3D , two parts, corresponding respectively to the cylindrical body  110  and to the conical structure  150  ( FIG. 3A ) are produced independently from a metallic material for the manufacture of the auxiliary booster  100 . The cylindrical body  110  and the conical structure  150  are then assembled by attaching the rear end  152  of the conical structure  150  to the front end  113  of the cylindrical body  110  by welding or brazing or another mechanical assembly ( FIG. 3B ). After having formed the thermal protection material layer  102  on the inner surface of the cylindrical body  110  and the conical structure  150 , the solid propellant charge  160  is poured into the internal common volume  103  consisting of the combination of the internal volume  111  of the cylindrical body  110  and of the internal volume  151  of the conical structure  150  ( FIG. 3B ) by using tooling allowing the provision of the central channel  161  in the charge ( FIG. 3C ). The rear zone  120 , equipped here with the nozzle  130  and with the ignition device  170 , is then attached to the rear end  112  of the cylindrical body  110  by welding or brazing or another mechanical connection ( FIG. 3D ). The auxiliary booster  100  as shown in  FIG. 2  is then obtained. 
     According to a variant embodiment illustrated in  FIG. 4 , the cylindrical body  110 ′, the conical structure  150 ′ and the rear zone  120 ′ are assembled prior to filing the booster with the solid propellant. In this case, the solid propellant  160 ′ is poured into the common internal volume constituted by the combination of the internal volume  111 ′ of the cylindrical body  110 ′, the internal volume  151 ′ of the conical structure  150 ′ and possibly all or part of the internal volume  121 ′ of the rear zone  120 ′. The solid propellant is poured through the opening  122 ′ present in the rear zone  120 ′ and by using tooling  20 ′ allowing the provision of the central channel in the solid propellant charge  160 ′. 
     According to another variant embodiment of the auxiliary booster  100 , each of the cylindrical body  110  and the conical structure  150  can be charged with solid propellant before their assembly. 
     According to another variant embodiment of the auxiliary booster  100 , the cylindrical body  110  is produced by assembly of a plurality of cylindrical shroud segments, each segment being charged with solid propellant before its assembly with another segment. 
       FIG. 5  illustrates an auxiliary booster  200  according to another embodiment of the invention and which differs from the auxiliary booster  100  described above in that at least the cylindrical body and the conical structure forming the front end of the booster are made of composite material, namely a fibrous reinforcement densified by a matrix. 
     As for the auxiliary booster  100  described previously, the auxiliary booster  200  comprises a cylindrical body  210  extending in a longitudinal direction X-X′ between a rear portion or zone  220  which, in the example described here, is in communication with a nozzle  230  and a front face  240  formed by a conical structure  250  extending in the continuation of the cylindrical body  210  in the axial direction X-X′. 
     The cylindrical body  210  delimits a first internal volume  211  while the conical structure  250  of the front face  240  delimits a second internal volume  251 . In conformity with the invention, the first internal volume  211  of the cylindrical body  210  communicates with the second internal volume  251  of the conical structure  250 . Still in conformity with the invention, a solid propellant charge  260  is present both in the first and second internal volumes  211  and  251 . 
     In other words, in the auxiliary booster reservoir shell is constituted both by the cylindrical body  210  and the conical structure  250  of the front face  240  which together form (combination of the first and second internal volumes  211  and  251 ) a common volume occupied by the solid propellant charge  260 , differing from the auxiliary boosters of the prior art like that described in document U.S. Pat. No. 5,131,610 and in which the shell forming the reservoir for the solid propellant is closed at the front face of the cylindrical body, preventing communication between the internal volume of the cylindrical body and the conical structure applied to the front face of the auxiliary booster. 
     A layer of a thermal protection material  202  is present in the inner surface of the cylindrical body  210  and of the conical structure  250 . The solid propellant charge  260  includes a central channel  261  extending in the longitudinal direction X-X′ and forming a combustion chamber as well as a duct for circulating the hot gases originating from the combustion of the propellant in the direction of the nozzle  230 . 
     In the example described here, the propellant charge  260  is present in particular in the entire internal volume  251  of the conical structure, i.e. from the front end  252  until the front end  253  of the conical structure  250 . Still in the example described here, the central channel  261  present in the solid propellant charge  260  is interrupted at an intermediate position located between the rear end  252  and the front end  253  of the conical structure  250 . The central channel can also extend to the front end  253  of the conical structure  250 . 
     The booster  200  also comprises an ignition device  270  of the solid propellant charge  260  present in the interior of the cylindrical body in proximity to the rear face  220  of the booster. 
     The booster  200  can also comprise a rear coupling device (not shown in  FIG. 5 ) which, depending on the specific design of the auxiliary booster, is located at the rear zone  220 , the skirt of the rear zone or the lower portion of the cylindrical body  210 , and a front coupling device (not shown in  FIG. 5 ) which, depending on the specific design of the auxiliary booster, is located at the conical structure  250 , the point  311  or the upper portion of the cylindrical body  210 . The coupling devices are intended to allow the attachment of the auxiliary booster to the main body of a launcher (not shown in  FIG. 5 ). 
     The cylindrical body  210  and the conical structure  250  are produced together by filament winding as illustrated in  FIG. 6A . To this end, a mandrel  300  is used including, in its front portion, a base  310  intended to allow the formation of the conical structure  250 , a cylinder  320  connected to the base  310  for the formation of the cylindrical body  210  and a rear portion  360  allowing the mandrel to be supported on a rotating shaft on its rear portion. The base  310  comprises a conical point  311  intended to form the front end of the conical structure  250  secured to a conical support  312  widening on the side opposite the conical point  311 . The conical point  311  and the conical support  312  can be produced from a composite or metallic material. 
     The conical point  311  is retained in a first element or counter-point  331  of the shaft  330  of the mandrel  300 . A second element  332  of the rotating shaft  300  is connected both to the inner surface of the base  310 , i.e. on the side opposite the one including the point  311 , and to the rear portion  360  of the cylinder  320 . The shaft  330  is supported by two pins  340  and  350 , at least one of which comprises a motor (not shown) to drive the mandrel  300  in rotation in the direction indicated by the arrow SR in  FIG. 5A . The pin  340  can for example comprise a motor and be secured to the rear portion  360  so as to drive the cylinder  320  in rotation. 
     In the example described here, the cylindrical body  210  and the conical structure  250  are produced by continuous winding of a strand  31  by means of a winding-laying head  33  capable of moving parallel to the axis of the mandrel  300  on a rail  34  so as to form a winding  32  on the mandrel  300 . The strand  31  is impregnated with a precursor of the matrix, or with the matrix itself. The direction of the winding on the mandrel is adjust depending on the orientation of the strands of the fibrous reinforcement that it is desired to obtain. The cylindrical body and the conical structure can also be produced by draping fibrous plies on the mandrel  300 . 
     The cylindrical body  210 , the rear end  220  and the conical structure  250  can in particular be produced by winding or draping of an organic matrix composite (thermosetting or thermoplastic). 
     An elastomer strip winding can be produced on the mandrel  300  before the filament winding of the strand  31  in order to form the internal layer of thermal protection material  202  of the booster. 
     Once the winding is finished, depending on the nature of the matrix, the polymerization or hardening of the resin is carried out so as to form a structural shell comprising the cylindrical body  210  and the conical structure  250  as illustrated in  FIG. 6B . The solid propellant charge  260  is then poured into the common internal volume  203  consisting of the combination of the internal volume  211  of the cylindrical body  210  and of the internal volume  251  of the conical structure  250  ( FIG. 6B ) by using tooling  40  allowing the provision of the central channel  261  in the charge ( FIG. 6C ). The rear zone  220  is then attached, equipped here with the nozzle  230  and the ignition device  270 , to the rear end  212  of the cylindrical body  210 , by adhesion for example ( FIG. 6D ). The auxiliary booster  200  as shown in  FIG. 4  is then obtained. 
     According to a variant embodiment illustrated in  FIG. 7 , the cylindrical body  210 ′, the conical structure  250 ′ and the rear zone  220 ′ are produced together or assembled before filling the booster with the solid propellant. In this case, the solid propellant  260 ′ is poured into the common internal volume consisting of the combination of the internal volume  211 ′ of the cylindrical body  210 ′, the internal volume  251 ′ of the conical structure  250 ′ and possibly all or a portion of the internal volume  221 ′ of the rear zone  220 ′. The solid propellant is poured through the opening  222 ′ present on the rear zone  220 ′ and by using tooling  40 ′ allowing the provision of the central channel in the solid propellant charge  260 ′. 
     The cylindrical body and the conical structure of composite material can be produced together, i.e. in a single piece. The cylindrical body and the conical structure can also be produced separately and then assembled together, the cylindrical body and the conical structure being able to be charged with solid propellant before or after their assembly. The cylindrical body can also be produced from shroud segments manufactured independently of one another and then assembled, the segments being able to be charged with solid propellant before or after their assembly. 
     Moreover, the elements constituting the auxiliary booster, namely the cylindrical body, the conical structure forming the front face and the rear zone, can be produced, some of metallic material and others of composite material. For example, an auxiliary booster of the invention can consist of a cylindrical body of composite material with a front face and a rear zone of metallic material.