SPACE VEHICLE CLIP INTENDED TO FORM AN ANNULAR CONNECTION AND COMPRISING AN AXIALLY DEFORMABLE ELASTIC MEMBER

Abstract

The attachment system (4) for a space vehicle (1) comprises a first support frame (5), a second support frame (6), and a fastener (7) for mechanically connecting the first frame (5) to the second frame (6). The second frame (6) comprises a base (60) and a mast (62) extending in a longitudinal direction (XX) of the attachment system (4) and at least partially in an orifice (53) of the first frame (5), the fastener (7) being configured to connect the first frame (5) to the mast (62) according to an annular connection. The attachment system (4) comprises an elastic member located around the mast (62) and configured to deform elastically axially.

Description

TECHNICAL FIELD The invention relates to the field of space applications. It relates to an attachment system for connecting a thruster to a main body of a space vehicle or for connecting a payload to a main body of a space vehicle. STATE OF THE PRIOR ART In most launchers, a propellant is mechanically connected to a main body by a ball joint. Any misalignments of the propellant relative to the main body do not cause significant moments on the main body. In some of these launchers, the side of the propellant is covered with large elastomeric pads to dampen vibrations between the propellant and the main body. The known ball joint is difficult and expensive to install. Furthermore, the shock absorbers are specific to each launcher. They are relatively heavy, expensive, and bulky. STATEMENT OF THE INVENTION The invention aims to at least partially solve the problems encountered in the solutions of the prior art. In this regard, the invention relates to a fastening system for a space vehicle. The fastening system comprises a first support frame, a second support frame, and a fastener for mechanically connecting the first frame to the second frame. According to the invention, the second frame comprises a base and a mast extending in a longitudinal direction of the attachment system and which extends at least partially into an orifice of the first frame. The attachment is configured to connect the first frame to the mast according to an annular connection. The attachment system comprises an elastic member located around the mast and elastically deformable axially. Thanks to the invention, the second frame is connected to the first frame, transmitting the propulsive forces to it, and misalignments between the frames do not cause excessive moments on the first frame. Vibrations between the frames are effectively and cost-effectively attenuated. The spacecraft's footprint is reduced. The invention may optionally comprise one or more of the following features combined with each other or not. Advantageously, the attachment system comprises a means for tightening the first frame towards the base. Preferably, the orifice passes through the first frame. Preferably, the first armature is located axially between the base and the clamping means. According to a particular embodiment, the attachment comprises a ball joint rigidly secured to the first frame and in which the mast is configured to slide axially. Preferably, the ball joint is a radial ball joint configured to withstand high radial loads, in particular compared to an axial ball joint of a space vehicle attachment of known structure. According to an advantageous embodiment, the elastic member comprises at least one spring washer centered around the longitudinal axis. According to another particular embodiment, the elastic member is located axially between the base and the first frame and / or between the first frame and the clamping means. Advantageously, the elastic member comprises a first assembly and a second assembly axially spaced from the first assembly. The first assembly is configured to bias the first reinforcement axially in the opposite direction of the second reinforcement. The second assembly is configured to bias the first reinforcement axially towards the second reinforcement. The invention also relates to a space vehicle comprising a main body, at least one thruster and an attachment system as defined above which mechanically connects the thruster to the main body. Preferably, the space vehicle comprises a launcher, a probe and / or a satellite. It may be reusable or not. According to a particular embodiment, the elastic member comprises spring washers stacked axially at least partially in opposition, so that the elastic member has a variable stiffness. Preferably, the elastic member is configured to have greater stiffness in a cruise phase of the space vehicle than just before takeoff or than when the space vehicle is at rest on the ground. According to an advantageous embodiment, the space vehicle comprises pyrotechnic means for separating the first frame from the second frame. Preferably, the pyrotechnic means is located inside the mast. The invention also relates to a method for mechanically connecting a thruster to a main body of a space vehicle using an attachment system as defined above. The connection method comprises inserting the mast into the hole of the first frame to connect it to the second frame in an annular connection, the elastic member being inserted around the mast and being axially elastically deformable. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood by reading the description of exemplary embodiments, given for purely indicative and non-limiting purposes, with reference to the appended drawings in which: Figure 1 is a partial schematic representation of a space vehicle comprising an attachment system according to a first embodiment of the invention; Figure 2 is a perspective representation of a fastening system according to the first embodiment; Figure 3 is a longitudinal sectional view of the attachment system according to the first embodiment; Figures 4 to 6 illustrate the method of connecting a thruster to a main body of a space vehicle using the attachment system according to the first embodiment. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Identical, similar or equivalent parts of different figures bear the same numerical references so as to facilitate the transition from one figure to another. Figure 1 depicts a space vehicle 1. The space vehicle 1 is a launch vehicle configured to release a payload (not shown) such as a probe or satellite into outer space. The space vehicle 1 comprises a main body 2 and thrusters 3, typically two to four thrusters 3. The thrusters 3 are each mechanically connected to the main body 2 by one of the attachment systems 4 which will be described below. The space vehicle 1 also comprises separation means 8 (figure 3) intended to separate each thruster 3 from the main body 2. Main body 2 houses the payload of spacecraft 1. It is located in the center of spacecraft 1 relative to thrusters 3 and is therefore also called central body 2. The thrusters 3 are typically solid or liquid rocket thrusters. They are preferably distributed symmetrically with respect to the longitudinal direction of the main body 2. Referring to Figures 2 and 3, the attachment system 4 comprises a first support frame 5, a second support frame 6, and a fastener 7 configured to connect the first frame 5 to the second frame 6. The attachment system 4 is substantially annular in revolution around its longitudinal axis XX. The terms "lower" and "upper" are used to describe relative orientations with respect to this axis. In this document, an axial direction is a direction parallel to that of the longitudinal axis XX. A radial or transverse direction is a direction orthogonal to an axial direction and intersecting the longitudinal axis XX. The first frame 5 comprises an upper grid 52 and a lower plate 51 which is integral with the upper grid 52. The upper grid 52 is rigidly secured to an external wall of the main body 2, for example by being fixed to this wall. The lower plate 51 is crossed by a through orifice 53 which is substantially centered around the longitudinal axis XX. The second frame 6 comprises a base 60 and a connecting mast 62 which projects from the base 60 in the direction of the longitudinal axis XX. The base 60 has at least partially a plate shape. The connecting mast 62 is in one piece with the base 60. The attachment 7 comprises a ball joint 9 which is located in the orifice 53 passing through the lower plate 51, and an elastic member 10. The ball joint 9 is a radial ball joint, that is to say that it is intended to support strong radial loads relative to the longitudinal axis XX, for example along the axis YY or along the axis ZZ which are represented in figure 3. Its bearing surface 91 is rigidly integral with the lower plate 51. The bearing 91 is for example force-mounted in the orifice 53. The ball joint 9 comprises a movable central body 92 which is movable according to three degrees of freedom in rotation. The movable body 92 surrounds the mast 62 which is slidably mounted relative to the movable body 92 in the axial direction. The mast 62 and the ball joint 9 therefore mechanically connect the first frame 5 to the second frame 6 according to an annular connection. The second frame 6 is connected to the first frame 5 with a degree of translational connection along the YY axis and a degree of translational connection along the ZZ axis. The second frame 6 is connected to the first frame 5 with a degree of elastic connection along the XX axis, a degree of rotational freedom along the XX axis, a degree of rotational freedom along the YY axis and a degree of rotational freedom along the ZZ axis. The elastic member 10 comprises spring washers 11, 13, 15, 18 which are stacked along the longitudinal axis XX, being located around the mast 62. These spring washers are also known as “Belleville” washers. They are retained along the longitudinal axis XX at the upper end of the attachment 7 by a clamping means 19. The washers 11, 13, 15, 18 are stacked axially at least partially in opposition, so that the elastic member 10 has a variable stiffness depending on the operating regime of the space vehicle 1. The elastic member 10 may have a greater stiffness in a cruising phase of the space vehicle 1 than just before takeoff when the space vehicle 1 is still on the ground or than when the space vehicle 1 is at rest on the ground. Indeed, the significant stiffness of the stack of washers 11, 13, 15, 18 makes it easier to control the space vehicle 1, in particular during a possible change of direction in flight. The stack of washers 11, 13, 15, 18 has greater flexibility in regimes where it serves above all to dampen the axial vibrations of one of the thrusters 3 relative to the main body 2, but also to connect the thrusters 3 more easily to the main body 2. More precisely, the washers 11, 13 form a first set 12 of washers, that is to say a first stage 12 of washers, which is located axially between the base 60 and the lower plate 51. The washers 15, 18 also form a second set 14 of washers, i.e. a second stage 14 of washers, which is located axially between the lower plate 51 and the clamping means 19. The first stage 12 is configured to deform elastically axially in compression, which makes it possible to limit the axial movements of the base 60 in the direction of the lower plate 51. The first group 11 of washers preferably has a greater stiffness than that of the second group 13 of washers. The second group 13 is preferably intended to dampen axial vibrations when the space vehicle 1 is on the ground or just before its takeoff. The first group 11 of washers is mainly intended to dampen axial vibrations during a cruising regime of the space vehicle 1. The second stage 14 is configured to deform elastically axially in tension, which makes it possible to limit the axial displacements of the base 60 opposite the lower plate 51. The second stage 14 comprises a third group 15 of washers. The third group 15 has a stiffness lower than that of the first group 11 and that of the second group 13. In particular, it has a flexibility which is substantially equal to the cumulative flexibility of the first group 11 and the second group 13. The third group 15 serves to dampen the axial vibrations generated when the propellant 3 tends to move away from the main body 2, in particular just before the separation of the propellant 3 from the main body 2. The elastic member 10 also comprises a group 18 of clamping washers. The group 18 of clamping washers has a stiffness lower than that of the first group 11 or that of the second group 13. The group 18 of clamping washers serves to allow small axial displacements of the first stage 12 and the second stage 14 along the mast 62, that is to say an axial play of the first stage 12 and the second stage 14 to dampen axial vibrations between the thruster 3 and the main body 4. The group 18 of clamping washers is axially compressed between the second stage 14 and a clamping means 19. The clamping means 19 is in mechanical contact with the group 18 of clamping washers which it compresses in the direction of the base 60. It is a nut clamping the mast 62 and located axially opposite the base 60 relative to the attachment 7. The attachment 7 comprises axially in the direction from the base 60 towards the plate 51 successively the first group 11 of washers, the second group 13 of washers, the radial ball joint 9, the third group 15 of washers, the group 18 of clamping washers and the clamping means 19. The means 8 for separating the propellant 3 from the main body 4 is formed by a pyrotechnic ring 8. The pyrotechnic ring 8 is located at the attachment 7 between this propellant 3 and the main body 2. The pyrotechnic ring 8 is located axially just below the radial ball joint 9. It is inside the mast 62. The position of the ring 8 allows the attachment 7 to break at a location where the moments exerted on the main body 2 are the lowest, which makes it possible to limit the separation forces exerted on the main body 2 when it is separated from the propellant 3. Fastener 7 is installed as follows: First and with reference to Figure 4, the first group 11 of washers is arranged around the mast 62, then the second group 13 of washers is stacked axially around the mast 62 above the first group 11. With reference to figure 5, the first frame 5 is axially brought closer to the second frame 6, the axial ball joint 9 is placed in the through hole 53 surrounding the mast 62. Referring to Figure 6, the group 18 of clamping washers is finally placed around the mast 62, bearing against the upper surface of the lower plate 51. The nut 19 is placed around the mast 62 and compresses the clamping group 18. When all the propellant or substantially all the propellant of the thruster 3 has been used, it tends to move away axially from the main body 2, i.e. downwards in Figure 6. An order is then given to the pyrotechnic ring 8 to separate the thruster 3 from the main body 2. The pyrotechnic ring 8 explodes, which causes the mast 62 to break just under the ball joint 9. In general, all the thrusters 3 are separated simultaneously from the main body 2. The main body 2 continues its course before releasing the payload such as a probe or a satellite. By virtue of the invention, the second frame 6 is connected to the first frame 5, transmitting the propulsive forces to it. Any misalignments between the frames 5, 6 do not cause excessively high moments on the first frame 5, due to the ball joint 9. The radial ball joint 9 supports significant radial forces between the propellant 3 and the main body 2. The elastic member 10 attenuates the vibrations between the frames 5, 6 effectively and at a lower cost. The ball joint 9 is thus subjected to reduced axial forces. The size of the space vehicle 1 is reduced, since the elastic member 10 is located at the level of the attachment 7. Of course, various modifications can be made by those skilled in the art to the invention which has just been described without departing from the scope of the disclosure of the invention. According to an alternative embodiment (not shown), the first frame 5 is secured to a payload, the second frame 6 is secured to a main body 2 of the launcher, and the attachment system 4 is configured to connect the payload to the main body via the frames 5, 6. According to an alternative embodiment (not shown), the connection mast 62 is fixed to the base 60, for example by clamping. The stiffness of the first stage 12 and that of the second stage 14 can be easily modified and are adapted according to the number of thrusters 3 and / or the main body 2. In particular, the more thrusters 3 the space vehicle 1 comprises, the more the elastic member 10 can be chosen with a low stiffness. According to an alternative embodiment (not shown), the first stage 12 comprises only one group 11 of washers configured to deform elastically axially in compression. According to an alternative embodiment (not shown), the second stage 14 comprises several groups 15 of washers which are each configured to deform elastically axially under tension. The elastic member may also comprise an elastically deformable polymer material such as an elastomer. According to an alternative embodiment (not shown), the bearing surface 91 of the ball joint is in one piece with the lower plate 51. 5

Claims

CLAIMS 1. Attachment system (4) for space vehicle (1), comprising: a first support frame (5), a second support frame (6), and a fastener (7) for mechanically connecting the first frame (5) to the second frame (6), characterized in that the second frame (6) comprises a base (60) and a mast (62) extending in a longitudinal direction (XX) of the attachment system (4) and at least partially in an orifice (53) of the first frame (5), the attachment (7) being configured to connect the first frame (5) to the mast (62) according to an annular connection, the attachment (7) comprising a ball joint (9) which is at least partially rigidly secured to the first frame (5) and in which the mast (62) is configured to slide axially, the attachment system (4) comprising an elastic member (10) located around the mast (62) and elastically deformable in the longitudinal direction (XX).

2. Attachment system (4) according to the preceding claim, comprising a means (19) for clamping the first frame (5) in the direction of the base (60), the orifice (53) preferably passing through the first frame (5) and the first frame (5) preferably being located axially between the base (60) and the clamping means (19).

3. Attachment system (4) according to any one of the preceding claims, in which the elastic member (10) comprises at least one spring washer centered around the longitudinal axis.

4. Attachment system (4) according to any one of the preceding claims, in which the elastic member (10) is located axially between the base (60) and the first frame (5) and / or between the first frame (5) and the clamping means (19).

5. Fastening system (4) according to any one of the preceding claims, in which the elastic member (10) comprises a first assembly (12) and a second assembly (14) axially spaced from the first assembly (12), the first assembly (12) being configured to bias the first armature (5) axially in the opposite direction to the second armature (6), and the second assembly (14) being configured to stress the first reinforcement (5) axially in the direction of the second reinforcement (6).

6. Space vehicle (1) comprising a main body (2), at least one thruster (3) and an attachment system (4) according to any one of the preceding claims mechanically connecting the thruster (3) to the main body (2).

7. Space vehicle (1) according to the preceding claim, wherein the elastic member (10) comprises spring washers (11, 13) stacked axially at least partially in opposition, so that the elastic member (10) has a variable stiffness, the elastic member (10) preferably being configured to have a greater stiffness in a cruising phase of the space vehicle (1) than when the space vehicle (1) is on the ground.

8. Space vehicle (1) according to any one of claims 6 to 7, comprising pyrotechnic means (8) for separating the first frame (5) from the second frame (6), the pyrotechnic means (8) preferably being located inside the mast (62).

9. Method for mechanically connecting a thruster (3) to a main body (2) of a space vehicle (1) using an attachment system (4) according to any one of claims 1 to 5 comprising: inserting the mast (62) into the orifice (53) of the first frame (5) to connect it to the second frame (6) according to an annular connection, the elastic member (10) being inserted around the mast (62) and being elastically deformable axially.

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