Abstract:
A method and device enable the linear separation of two elements attached to each other through two connecting surfaces which are conical in this example, of a first element and a second element respectively, using thermite placed on the other side of the wall of the outer element, facing a connecting arrangement placed between both connecting surfaces. An electrical triggering of the thermite causes a quick and local warming-up, at the connecting arrangement which, after melting, enables both elements to be separated.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the French patent application No. 1357637 filed on Aug. 1, 2013, the entire disclosures of which are incorporated herein by way of reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a linear separation, as smooth as possible, of a first element with respect to a second element, which are rigidly connected beforehand The invention is preferably applicable to spatial launchers, for separating stages from each other, of a launcher and of its cap or a stage and the payload, of missiles, space probes, or even planes, in the case of a payload release. The purpose of this separation is to reduce the weight of the on-board assembly, or to release a payload. These applications are characterized in that there is a need for separating objects that may be fragile, for example a satellite, and the connection of which has had to undergo high mechanical loads, as those undergone when propelled by a launcher. 
         [0003]      FIGS. 1A and 1B  illustrate the principle of separation between two elements  1  and  2  of a launcher. The first element  1  is preferably an element with the rank n, preferably a first engine stage. The second element is an element with the rank n+1, either a second engine element, or a payload, for example a satellite. The linear separation, in the launcher axis, thus has to be carried out without deteriorating the base of the second element and, in the case where it is desired to recover the first element  1 , without deteriorating the surface thereof, where the connection between both these elements  1  and  2  was located. 
         [0004]    In the current state of the art, the connecting/separating system is mostly of four types, which are the following ones: 
         [0005]    1) the connections by bolting, riveting and pyrotechnic cutting off by pressure and local temperature rise of the structure. These systems, due to their operation, generate ejected material debris. Moreover, the cutting off causes a significant impact in the structure, which may be damageable for the payloads of the launcher; 
         [0006]    Patent document FR 2,947,808 shows an example of implementing such a solution. 
         [0007]    2) The connections by bolting, riveting and pyrotechnic cutting off by rupturing the structure, through the deformation of a pyrotechnic element. This solution is the most employed and does not generate debris, but causes a very significant impact; 
         [0008]    3) the connections by pyrotechnic bolting and rupturing or separating the nut. This type of solution generates much less impact than the two previous ones, but requires several bolts to transmit strains from one element to the other, thus generating higher failure risks because of the number of devices involved; 
         [0009]    4) the connections by straps and rupturing the same by pyrotechnic bolts. This type of solution does not enable high strains to be transmitted between both elements and does not allow for too large of diameters for the launchers. Also in this case, the stress relief causes a high impact in the structures. 
         [0010]    Generally, in the current state of these techniques, systems coming from these connecting-separating solutions have the feature of leaving most of the time, asperities on the external shape of the launcher, after the separation. 
         [0011]    The purpose of the invention is to overcome the abovementioned drawbacks. 
       SUMMARY OF THE INVENTION 
       [0012]    To that end, a first main object of the invention is a method for linearly connecting and separating two elements linearly connected to each other, by a defined local connection, and that have to be securely linearly separated, the separation occurring by a quick warming-up, at or near the connection, this warming-up being remotely triggered. 
         [0013]    According to the invention, the method comprises:
       connecting both elements at two respective corresponding surfaces of both these elements, by connecting means placed between two respective connecting surfaces of both elements, one of both connecting surfaces being a first separating surface of a separating wall having a second separating surface, opposite to the first separating surface;   providing, on the second separating surface of the separating wall of the material, thermite, inflammable by an electrical control connection;   pyrotechnically triggering the thermite to cause, only by its warming-up, the quick warming-up, and not the explosion, and the destruction of the connecting means.       
 
         [0017]    A second main object of the invention is a device for connecting and linearly separating both elements linearly connected to each other by a defined local connection and that have to be securely separated, the separation occurring by a quick warming up, at or near the connection, the warming-up being remotely triggered. 
         [0018]    According to the invention, the device comprises:
       means for connecting both elements, these connecting means being placed between two respective connecting surfaces of both elements, one of both connecting surfaces being the first surface of a separating wall, which has a second surface opposite to the first separating surface;   thermite, placed on the second separating surface; and   means for remotely pyrotechnically triggering the thermite.       
 
         [0022]    In the preferential embodiment of the invention, both connecting surfaces are respective surfaces of both elements, the separating wall being the walls of one of both elements. 
         [0023]    In this case, advantageously, both connecting surfaces are conical. 
         [0024]    The connecting means comprise soldering or gluing. 
         [0025]    Preferably, the separating wall is that of the element placed outside the other element, the material being placed in an outer cavity of this wall of the outer element. 
         [0026]    A third object of the invention is an aeronautic launcher comprising at least one carrier stage comprising a first element and a stage carried by and attached to the carrier stage and comprising a second element, the launcher being characterized in that it comprises a plurality of previously described devices, distributed on the entire periphery of the launcher between both stages to secure them, and then separate them. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The invention and its different characteristics will be better understood upon reading the following description, accompanied with several figures, respectively representing: 
           [0028]      FIGS. 1A and 1B , a scheme representing the separation of two elements of a launcher; 
           [0029]      FIG. 2 , in cross-section, the principle of the method according to the invention; 
           [0030]      FIG. 3 , in cross-section, one embodiment of the device according to the invention; 
           [0031]      FIG. 4 , in an isometric view, a certain embodiment of the device according to the invention; and 
           [0032]      FIG. 5 , in cross-section, a detail of the embodiment of the device according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]      FIG. 2  shows a scheme of the method and the device according to the invention, applied to two elements  1  and  2 , which are, in the preferential application of the invention, for the first element  1 , an aerospace or aeronautic launcher with the rank n, for example the first stage of a launcher on the end of which is attached the second element, which is either a second launcher with a rank n+1, that is preferably a second launcher stage, or an operational load, for example containing equipment or a facility to be put into orbit. The front end of the first element  1  is conical, that is the outer wall  12  of this first element  1  is conical to facilitate the separation thereof, this conicity being optional. Correspondingly, the back end of the second element  2  has an inner wall  22 , which is conical, with the same conicity as the outer wall  12  of the first launcher.  1 . The interface between both these surfaces, the outer surface  12  of the first launcher  1  and the inner surface  22  of the second launcher  2 , comprises connecting means  11  to securely and reliably secure the elements  1  and  2  to each other. These connecting means  11  are, preferably, a soldering distributed on the entire periphery of both these surfaces. These connecting means can also be a glue provided in the same way. It is set out that the solder or glue tape is placed in a housing or recess of the upper structure, that is, of the second element  2 . 
         [0034]    To immobilize both elements  1  and  2 , the latter are brought to the melting temperature of the solder or glue used for this assembly. For example, if these structures to be assembled are made of titanium and if the solder chosen is a silver alloy, the entire zone to be assembled is brought to the melting temperature of the silver alloy, that is, about 960° C. For this, several conventional methods are chosen, for example induction soldering, oven heating soldering, under a neutral atmosphere, or resistance soldering. For the assembly relative to the present invention, it is noted that induction soldering or resistance soldering are more suitable for high volumes. Once the soldering is carried out, the heating means are removed and the connection is thus operational. 
         [0035]    To carry out the disengagement of both elements, that is the first element  1  and the second element  2 , in a housing or recess  23  provided in the outer surface  26  of the second element  2 , on a so-called second separating surface  21 , facing the connecting means  11 , are introduced heating means comprising a layer  24  of thermite (definition of thermite: a mixture of a metal fuel that can often be aluminum, but not only, and an oxidant, often a metal oxidant). It is set out here that the term thermite encompasses nanothermites. The first separating surface comprises the connecting surface  22  of the second element  2 . The wall of the second element  2  here becomes a separating surface. Via a remote triggering by an electrical control connection  60 , the quick warming-up of this thermite material  24  is triggered when it is desired to disengage the first element  1  from the second element  2 . Hence, the connecting means  11 , that is solder or glue, melt and both elements, that is the first element  1  and the second element  2 , are separated. 
         [0036]    The materials used to make up this thermite can be sheathed thermite. This type of material, by an exothermal oxidoreduction reaction, produces temperatures in the order of 2800°, from 1230° C. to 2770° K, by including the nanothermites. It is set out that the connecting means are thus placed surrounding the entire connection, that is, on the periphery of the assembly of the first element  1  and the second element  2 . 
         [0037]    The connection represented is advantageously completed with a first inner seal  15 , placed between the first element and the second element and a second outer seal  16 , placed between the first element and the second element, but outside the assembly. 
         [0038]      FIG. 3  shows again the same place, described by the present invention, in cross-section. However, triggering means have been represented. They comprise an igniter  30  of the type used by the pyrotechnical equipment. It is placed outside the second element, projecting from the outer surface  26  of the second element. A back-plate  31 , made of several elements, ensures connection between this igniter  30  and the heating means, here comprising a thermite tape  24 . The attachment of the igniter  30  to the second element  2  can be made by means of a screw-nut system  32 , embedded in the thickness of the second element  2 . 
         [0039]      FIG. 4  shows this igniter  30 , screwed to the outer surface  26  of the second element  2 . It can also be located inside. If a plurality of igniters  30  is thus necessary, on the entire periphery of the assembly, a same number of back-plates  31  is used to join the thermite tape  24  and the igniters  30 . The back-plate  31  fills the housing  23 , provided on the entire circumference of the outer surface  26  of the second element  2 . These igniters  30  will thus cause the instantaneous ignition of the thermite tape  24 , or of the equivalent material, if any. The temperature generated in the entire junction is adjusted by the amount of material making up the thermite, and the metal environment of the assembly. The heat emission diffuses in the structure, at the connection, which in turn transmits this heat to the solder, or glue  11 . The latter  11  will reach its melting temperature and the disengagement of the first element  1  from the second element  2  will thus occur. 
         [0040]    With regard to  FIG. 5 , a housing or recess  25  in which the connecting means  11  are placed, such as solder or glue, can be provided. This is a shallow cavity, surrounding the periphery of the inner surface  22  of the second element  2 . 
         [0041]    In the case of both elements of an aerospace launcher, the first element  1  and the second element  2  are intentionally under pressure. Hence, they will move away from each other, under the so-called champagne cork effect, along the linear axis of the assembly. In the case where there is no pressure inside these both elements, or between the structures, the distancing can be made by any other known means such as springs, distancing rockets, pneumatic means, or the like. 
         [0042]    After the first element and the second element are disengaged, the internal structure of the second element has again a surface with neither protuberance, nor pull-out. 
         [0043]    Moreover, the invention meets a provision of Article 5 of the Space Operations Act (SOA), relating to the Satellite Lunching Operators, in order to ensure the environment protection of the outer space, in particular for restricting risks related to space debris. 
         [0044]    While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.