Abstract:
The invention concerns a launch vehicle comprising a shroud ( 1   a,    5   a ) supporting auxiliary propellers ( 2, 3 ) applying in operation excess flow of stresses to the shroud ( 1   a,    5   a ), said device comprising means for coupling the payload ( 4 ) with the launch vehicle shroud. The invention is characterized in that the coupling means are designed to ensure a mechanical coupling between the payload ( 4 ) and the shroud along the direction of the launch vehicle longitudinal axis (X), and to cause them to be disengaged along radial and tangential directions. The invention is useful for neutralizing the effects on the payload of excess stresses applied on the launch vehicle shroud by the auxiliary propellers ( 2, 3 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for supporting a payload in a launch vehicle for launching said payload, said launch vehicle including a shell supporting at least one booster which in operation applies excess forces to said shell, said device including a system for mechanically connecting said payload to said shell of the launch vehicle. 
     2. Description of the Related Art 
     This kind of device is disclosed in applicant&#39;s international patent application WO 98/32658, corresponding to U.S. Pat. No. 6,244,541, with issue date of Jun. 12, 2001. It is designed to be integrated into a launch vehicle for launching a payload into space, shown diagrammatically in FIG. 1 of the accompanying drawings, in which the launch vehicle includes a first stage  1  equipped with boosters  2  and  3  fixed to the shell  1   a  of the first stage in diametrally opposite positions and parallel to the longitudinal axis X of the shell. FIG. 1 also shows diagrammatically a payload such as a satellite  4  mounted on the shell  5   a  of a second stage  5  of the launch vehicle by means of an adapter in the form of a frustoconical skirt  6 . The satellite is conventionally protected by a nose-cap  7  while passing through the atmosphere. The shells  1   a  and  5   a  are cylindrical, co-extensive and fastened together. 
     As explained in the patent application previously cited, the thrust developed by the boosters  2 ,  3  applies high axial forces to the shell  1   a  of the first stage, in particular at the points  8 ,  9  at which the boosters  2 ,  3  are attached to the first stage. FIG. 2 of the accompanying drawings shows the intensity F of these forces as observed at the periphery of the shell  1   a.    
     The forces are much more pronounced at the attachment points  8 ,  9  (at angular positions of 90° and 270°, respectively) and it they were transmitted to the skirt  6  via the shell  5   a  of the second stage  5  they would cause asymmetrical deformation of the skirt, which could damage the satellite if no countermeasures were applied. FIG. 3 of the accompanying drawings shows in cross section the “deformation” of the shell of the launch vehicle subjected to the distribution of forces shown in FIG. 2 by boosters  2 ,  3  fixed to the shell at points  8 ,  9 , respectively. 
     According to the patent application previously cited, transmission of deformation to the satellite is prevented by installing between the satellite and the launch vehicle, for example at the level of the larger base  6   b  of the skirt  6 , whose other base  6   a  receives the satellite, a suspension device consisting of an annular chamber with flexible walls and filled with a fluid. The “excess” forces received by the annular chamber in line with the attachment points  8 ,  9  are uniformly distributed circumferentially by the fluid in the chamber and the skirt  6  is therefore subjected to perfectly symmetrical forces that do not deform the skirt asymmetrically. The integrity of the satellite is therefore protected while the boosters  2 ,  3  are operating. 
     Means are provided for varying the pressure of the fluid contained in the annular chamber. Thus the pressure can be lowered from a relatively higher value ensuring good mechanical cohesion of the launch vehicle and the skirt  6 , as is necessary in particular when the boosters  2 ,  3  are operating, to a relatively lower value for filtering forces such as vibration or shock forces propagating in the launch vehicle, in particular at the time of separation of stages of the launch vehicle and the nose-cap  7 . 
     The device described in the patent application previously cited achieves the stated objective. However, it implies the use of either an annular chamber with flexible walls or a chamber with two complementary rigid annular walls mobile axially relative to each other, the chamber being sealed by at least one O-ring whose length is equal to the circumference of the chamber. 
     Because it is integrated into a launch vehicle, this kind of device must be very reliable. It can be very costly to achieve this because of the sealing problems that arise when using an annular chamber with flexible walls or an annular chamber incorporating an O-ring with the same circumference. 
     If the annular chamber with flexible walls solution is adopted, the flexible wall is greatly stiffened when the pressure in the chamber is high, to the point where forces transmitted by the device pass through the wall rather than through the fluid that it confines, which renders the device ineffective at high pressures. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is precisely to provide a device for supporting a payload in a launch vehicle for launching said payload into space that is free of the above drawbacks and which in particular prevents the transmission of excess forces from the launch vehicle to the satellite, combined with highly reliable operation and moderate production cost. 
     The above objective of the invention, and others that will become apparent in the course of the following description, are achieved with a device for supporting a payload in a launch vehicle for launching said payload, said launch vehicle including a shell supporting at least one booster applying excess forces to said shell when in operation, and said device including means for mechanically connecting said payload to said shell of said launch vehicle, characterized in that said connecting means are designed to ensure mechanical coupling of the load and the shell in the direction of a longitudinal axis of the launch vehicle and decoupling thereof in radial and tangential directions. 
     As will be seen later, the connecting system prevents significant transmission of excess forces to the payload whilst ensuring mechanical cohesion of the launch vehicle/payload combination. 
     In one preferred embodiment of a device in accordance with the invention, the connecting means include an annular rim fastened to said payload and an annular groove fixed with respect to said shell, accommodating said rim so that is able to slide in any radial direction or tangential direction, and stopping any movement of said rim relative to said groove in the axial direction. 
     In accordance with another feature of the device in accordance with the invention, the connecting means further include at least one thrust bearing system mechanically connecting the shell and the payload in at least one of said radial and tangential directions. The thrust bearing system is at a node of the deformation of said shell in the presence of excess forces in cross section in a plane passing through said thrust bearing system. It is even more preferable for the thrust bearing to be disposed at a displacement node of said shell in a tangential direction and therefore in a tangential direction passing through that node. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent on reading the following description and examining the accompanying drawings, in which; 
     FIG. 1 is a diagram showing part of a prior art satellite launch vehicle, as described in the preamble to this description, 
     FIG. 2 is a graph representing the peripheral distribution of the axial forces applied to the shell of the launch vehicle when the boosters  8  and  9  are operating, and has been commented on in the preamble to this description, 
     FIG. 3 shows a cross section of the shell of the launch vehicle when deformed by the forces applied to the shell by the boosters, and has been commented on in the preamble to this description, 
     FIG. 4 is a diagrammatic plan view of the device according to the present invention, and 
     FIGS. 5 and 6 are views of the device shown in FIG. 4 in section taken along the lines III and IV, respectively. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     The device in accordance with the invention is located at the level of a plane P perpendicular to a longitudinal axis X of the launch vehicle (see FIG.  1 ), and that median plan can be at any level between the bases  6   a  and  6   b  of the skirt  6 . It is advantageously at the level of the base  6   b.  Even more generally, the device could be installed at any level between the payload and the attachment points  8 ,  9  of the boosters  2 ,  3 . 
     FIG. 4 shows that the device is generally circular, It Is essentially made up of axially superposed annular members between which are installed a plurality of spring thrust bearings  12   i , a plurality of hydraulic thrust bearings  13   j  and, in accordance with the present invention, a plurality of mechanical connection thrust bearings  14   i . 
     The structure and the operation of the spring thrust bearings  12   i  and the hydraulic thrust bearings  13   j  constitute the subject matter of U.S. patent application, Ser. No. 09/868,641, with filing date of Sep. 25, 2001, which is based on the French patent application 98/16561, with filing date of Dec. 29, 1998. Reference may be had to the U.S. patent application for more details of the thrust bearings. Briefly, their function is to filter the shock referred to in the preamble of this description, by appropriately and temporarily reducing the axial stiffness of the launch vehicle, at the level of the plane P, which shock occurs in particular on jettisoning the nose-cap  7  and on separation of the stages of the launch vehicle. 
     Note that the thrust bearings mentioned above are regularly distributed and interleaved with each other. By way of illustrative and non-limiting example only, the device shown therefore comprises four spring thrust bearings  12   i  (i from 1 to 4), four mechanical connecting thrust bearings  14   i  (i 1 to 4), and eight hydraulic thrust bearings  13   j  (j from 1 to 8) equi-angularly distributed with an increment of 22.5°. 
     At the level of the base  6   b  of the skirt  6  the shell  1   a,    5   a  of the launch vehicle has substantially the same circular shape as the device shown in FIG. 2, which follows the contour of said shell. When the boosters  2  and  3  fixed to the shell at points  8  and  9 , respectively, are operating, they apply to the shell  1   a,    5   a  of the launch vehicle excess forces around the attachment points  8  and  9 , as described above with reference to FIG.  2 . These excess forces deform the shells  1   a,    5   a  (see FIG.  3 ), including in the plane passing through the thrust bearings  12   i ,  13   j  and  14   i . 
     As confirmed by computation, mock-ups have shown that this deformation passes through four equi-angularly distributed points on the cross section of the shell of the launch vehicle. This distribution of the points is offset by an angle a from an axis passing through the attachment points  8 ,  9 , as shown in FIG.  4 . 
     This is explained by the composite material from which the shell of the launch vehicle is constructed. By way of illustrative and non-limiting example only, the angle α can be of the order of approximately 10°. 
     Clearly, deformation of the shell of the launch vehicle can damage the satellite if it propagates to the skirt  6  and then to the satellite  4 . 
     An object of the present invention is precisely to prevent such propagation of deformation, in order to protect the physical integrity of the satellite. 
     In accordance with the invention, that object is achieved by decoupling the deformation of the skirt  6  and the deformation of the shell  5   a  of the second stage radially and tangentially, by providing at each of the four points mentioned above a mechanical connection thrust bearing  14 , coupling the skirt  6  and the shell  5   a  of the second stage  5 . 
     Turn now to FIGS. 5 and 6 of the accompanying drawings, which are partial views of the support device according to the invention in axial section taken along the lines III and IV, respectively, in FIG. 4, passing through a main section of the device and a respective one ( 14   3  of the thrust bearings  14   i . It must be understood that the other thrust bearings of the same type are identical to that to be described. 
     By way of illustrative and non-limiting example only, the support device in accordance with the present invention is described as associated with and integrated into the suspension device described in the aforementioned U.S. patent application, Ser. No. 09/868,641. Of course, the two devices could be used independently of each other. 
     FIGS. 5 and 6 respectively show a first annular member  10  fixed to the skirt  6  by circumferentially distributed nut and bolt fasteners such as that referenced  15  and a second annular member  11  mounted on the second stage  5  of the launch vehicle by a connecting system ( 20   a,    20   b,    22 ,  23 ) forming part of the present invention. 
     The annular member  11  has a first annular flange  17  and a second annular flange  18  fastened by nut and bolt fasteners such as that referenced  19 . 
     The first flange  17  takes the form of a ring whose axis is parallel to the axis X of the launch vehicle and which has two axially offset radial annular rims. One rim  17   a  projects outward and has nut and bolt fasteners such as that referenced  19  passed through it and the other rim  17   b  faces inward and engages in an annular groove delimited by rings  20   a,    20   b  assembled by nut and bolt fasteners such as that referenced  21 . The ring  20   b  is fixed to the second stage  5  by nut and bolt fasteners such as that referenced  16 . The members  17   b ,  20   a ,  20   b  are part of the connecting system of the device according to the present invention. 
     Shoes  22 ,  23  allow the rim  17   b  of the flange  17  to slide in the groove delimited by the rings  20   a,    20   b,  in the direction transverse to the axis X of the launch vehicle, for a reason explained later. 
     The flange  17  can be clamped by the shoes  22 ,  23  to prevent the flange from being separated from the shoes by external forces applied to the flange. 
     The second flange  18  carries the spring and hydraulic thrust bearings mentioned above (not visible in FIGS. 5 and 6) and described more completely in the patent application previously cited, to which reference may be had for further details concerning them. The thrust bearings fasten the annular member  10  and the flanges  17  and  18 , with the member  10  pressed against the flange  18 . 
     For the purpose of describing the present invention, the member  10  and the flanges  17 ,  18  are considered to form an annular unitary assembly ( 10 ,  17 ,  18 ), i.e. an undeformable block, which is not the case when that assembly is used to filter shock, as described in the U.S. patent application previously cited. 
     Turn now to FIG. 6 of the accompanying drawings, which shows the device in accordance with the invention in section, including one ( 14   3 ) of the mechanical connection thrust bearings forming part of the connecting system of the support device according to the invention. 
     In a preferred embodiment of the present invention, the thrust bearing  14   3  takes the form of a pin with a radial axis Y (see FIG. 6) passing through respective radial holes  24 ,  25  in the flange  17  and in a lug  26  projecting from the ring  20   a  and facing the flange  17 . 
     Starting from one end, the pin  14   3  includes a head  27 , a screwthreaded part  28  adapted to be fixed in the hole  24 , which is threaded accordingly, and a smooth-surfaced part  29  adapted to slide freely in the hole  25  in the lug  26 . 
     It is therefore clear that the flange  17  is free to move in the radial direction Y toward or away from the lug  26 . 
     Clearly, the same relative movements of the lug  26  and the flange  17  could be obtained by screwing the pin into the hole  25  and having the pin free to move in the hole  24 . 
     The annular assembly ( 10 ,  17 ,  18 ) is therefore tree to be deformed radially at the level of the thrust bearings  14   i  by the excess forces generated by the boosters  2 ,  3 . 
     Because they hold the holes  24  and  25  in alignment on the axis Y, the pins  14   i  prevent tangential movement (in a direction T perpendicular to the axes X and Y, see FIG. 4) of the flange  17  relative to the lug  26  and therefore of the skirt  6  and the satellite  4  attached to the assembly ( 10 ,  17 ,  18 ) relative to the shell  5  of the second stage and to the shell of the first stage, which is fastened to that of the second stage. To prevent it from being crushed by tangential forces, the hole  25  can be lined with a sleeve  30  made of an appropriate metal. 
     In accordance with the invention, by placing the pins  14   i  at the nodes of tangential displacement of the shell of the launch vehicle when subject to excess forces, a mechanical connection is established between the satellite  4  and the launch vehicle which ensures the global cohesion of the resulting combination, without impeding radial and/or tangential deformation of the flange  17  relative to the ring  20   a,  which is necessary for decoupling these members from excess forces on the shell of the launch vehicle generated by the boosters. The tangential coupling established by the pins or thrust bearings  14   i  has no effect on this decoupling because the thrust bearings are located at the nodes of tangential displacement, i.e. at points where no tangential forces are applied between the shell and the annular assembly ( 10 ,  17 ,  18 ). 
     Thanks to the invention, axial load errors at the interface between the shell  5   a  and the skirt  6  and due to the operation of the boosters  2 ,  3  can be very significantly reduced. In one particular embodiment of the device according to the invention, the magnitude of the load variations at this interface was reduced to less than 5 N/mm, i.e. to a level that caused no significant asymmetrical deformation of the skirt  6 , which correctly protects the satellite carried by the skirt from transmission of such deformation. 
     This result is obtained thanks to the coupling system described above, which provides mechanical coupling of the launch vehicle and the satellite along the longitudinal axis X of the launch vehicle through cooperation of the annular rim  17   b  and the groove delimited by the rings  20   a,    20   b  and decoupling of the launch vehicle and the satellite in the radial and tangential directions (except at the tangential displacement nodes). The decoupling prevents any significant transmission of excess forces to the satellite. 
     Of course, the invention is not limited to the embodiment described and shown, which is provided by way of example only. Thus the mechanical coupling by the thrust bearings of the ring  20   a  and the annular assembly ( 10 ,  17 ,  18 ) could be established at radial displacement nodes of the deformation of the shell of the launch vehicle, rather than at the tangential displacement nodes. 
     It is possible to compute the positions of the radial displacement nodes and the tangential displacement nodes and to verify the positions obtained on a mock up. The thrust bearings used to establish this coupling are very similar to the thrust bearings  14   i  except that the axes of the pins are tangential rather than radial and therefore pass through aligned holes on a tangential axis like the axis T (see FIG. 4) in the corresponding lugs of the annular assembly ( 10 ,  17 ,  18 ) and the ring  20   a,  respectively. 
     Experiments and computation have shown that the mechanical cohesion of the launch vehicle/satellite obtained with “radial” thrust bearings disposed where the deformations of the shell in the radial direction are substantially zero is good, although slightly less good than with “tangential” thrust bearings. 
     Alternatively, said cohesion could be provided by a system of thrust bearings including both radial thrust bearings and tangential thrust bearings. 
     Similarly, the device according to the invention has been described as integrated into the suspension device with hydraulic and spring thrust bearings described in the U.S. patent application previously cited. Clearly, the support device according to the invention could be physically separated from any such suspension device, or even used in isolation if there is no need to treat the shock that the suspension device is intended to filter. 
     The invention being thus described, it will be apparent that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be recognized by one skilled in the art are intended to be included within the scope of the following claims.