FR2691425A1 - Anti-vibration fairings for reservoirs on spacecraft launchers - using central fairings between two cylindrical reservoirs ring-clamped with spring-loaded tensioners and seal body fairings - Google Patents

Abstract

The anti-vibration fairing carries two similar cylindrical accessories (20) on the spacecraft. Two end fairings are connected by central fairings (28,30a,30b), containing tensioning devices (34) for accessory clamps (32). At least three rings (32) clamp around each accessory, with tensioners (34) between these and adjacent accessories. The central fairing comprises two lateral deflectors (28), end fixed, with seals (58) against the spacecraft body. Complementary crossbeams (30a,30b) fasten by three tensioners (74), each with springing and a ring around the fastener. USE/ADVANTAGE - Space shuttle servo reservoirs, improving aerodynamics, rigidity and absorbing vibrations, with little weight penalty.

Description

ANTI-VIBRATION FAIRING FOR A GROUP OF ACCESSORIES
JUXTAPOSES ON BOARD ON A SPACE MACHINE
LIKE A LAUNCHER.

DESCRIPTION
The invention relates to an anti-vibration fairing intended to be associated with a group of at least two substantially cylindrical juxtaposed accessories, of similar dimensions, fixed to a spacecraft such as a launcher.

 Such a fairing is particularly suitable for being used in association with a group of juxtaposed accessories mounted on an auxiliary thruster of a launcher. I1 can however also be used on a spacecraft of a different nature such as an aircraft, a space shuttle, etc. The accessories can consist of tanks or any other cylindrical element.

 To allow precise control of the trajectory of a launcher equipped with boosters, when it is launched, the orientation of the nozzles of the boosters is adjusted by servo-cylinders actuated by pressurized oil. This oil is initially contained in two or three juxtaposed cylindrical tanks, of similar dimensions, which are fixed on each of the booster boosters. The oil is pressurized by helium.

 The attachment of each of the tanks to the booster can in particular be ensured, on the one hand, by connecting rods connecting the upper or front ends of the tanks to a ring surrounding the booster (this ring also serving to 'attachment of the booster to the main body of the launcher) and, on the other hand, at the lower or rear ends of the tanks, by supports directly connecting the tanks to the rear skirt of the booster.

 These tanks fixed on the booster boosters constitute important protuberances which disturb the aerodynamic behavior of the lower part of the boosters, in particular near the nozzles, and which risk entering into vibration under the effect of vibrations. induced in boosters during launch.

The subject of the invention is precisely a fairing, the design of which, without excessively increasing the weight, - improves the aerodynamic behavior of the part
boost boosters, decreasing or
eliminating aerodynamic interactions between
tanks and booster, on the one hand, and
between the tanks, on the other hand, which has for
effect of improving drag and reducing disturbance
tion of the jet of nozzle - to increase the transverse stiffnesses of these reser
see and avoid their dynamic coupling with the envelope
boost booster; and - to dampen the vibrations of the tanks and, in particular
bind, bending vibrations.

 In accordance with the invention, these various results are obtained by means of an anti-vibration fairing for a group of at least two substantially cylindrical juxtaposed accessories, of similar dimensions, fixed to a spacecraft, characterized in that it comprises two end fairings connected by a central fairing and traction means interposed between the neighboring accessories, inside the central fairing, so as to apply a prestress between these accessories.

 The establishment of a central fairing between the end fairings makes it possible to obtain the desired aerodynamic and anti-vibration behavior. The traction means which connect the neighboring accessories to each other apply an initial prestress making it possible to increase the transverse rigidity of the tanks by making the transverse rigidities of the central fairing participate and to dampen the vibrations. The initial prestresses are such that they do not cause all of the accessories to move.

 According to a preferred embodiment of the invention, the traction means comprise at least three spaced belts which are fixed around each of the accessories, and traction mechanisms connecting together the belts of neighboring accessories. Each of these traction mechanisms preferably comprises at least one first elastic prestressed means.

 Furthermore, the central fairing advantageously comprises two lateral deflectors and, depending on whether the machine supports two or more accessories, one or more pairs of complementary spacers connected together by means of applying spacers to the accessories.

 The two lateral deflectors are fixed on the two extreme accessories of the group of accessories, on both sides of this group, in the extension of the end fairings. In addition, the outer edges of the side deflectors carry seals comprising at least two lips which are in contact with the spacecraft supporting the accessories.

 The fixing of the lateral deflectors on the accessories is advantageously carried out by gluing.

 The lateral deflectors as well as the complementary spacers which form the central fairing include an internal honeycomb structure, covered with a rigid coating of composite material.

The desired mechanical strength is thus obtained for a particularly low increase in weight.

 The spacers preferably comprise feet having surfaces in arcs of a circle intended to come to bear on the belts surrounding each of the accessories. The longitudinal immobilization of the spacers can then be obtained, for example, by means of projecting edges formed on at least one of the three belts and between which the corresponding feet of the spacers are trapped.

 To favor the installation of the spacers, at least one of the surfaces in contact with the belts and of the legs of the spacers is covered with a material promoting sliding, such as polytetrafluoroethylene. The adaptation of the forms can also be facilitated by covering with foam of adequate rigidity the surfaces of the feet of the spacers which are in contact with the belts.

 Furthermore, the means making it possible to apply the spacers to the accessories advantageously comprise at least three traction systems each comprising a second prestressed elastic means and a ring through which one of the traction mechanisms passes.

A preferred embodiment of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which
- Figure 1 is a perspective view schematically illustrating the lower or rear part of a launcher equipped with two booster boosters, one of which visibly carries two juxtaposed cylindrical tanks which can be equipped with a conforming anti-vibration fairing to the invention
- Figure 2 is a perspective view illustrating on a larger scale the central fairing and the traction means which are associated with the two tanks according to the invention, one of the two tanks and part of the central fairing having been purposely omitted, to facilitate understanding
- Figure 3 is a sectional view illustrating the cooperation of one of the feet of one of the spacers of the central fairing with one of the belts fixed around a tank
- Figure 4 shows one of the traction mechanisms which interconnect the belts of neighboring tanks; and
- Figure 5 shows on a larger scale one of the traction systems for applying the additional spacers on the tanks.

 In FIG. 1, the reference 10 designates the lower or rear part of the main body of a launcher. On either side of this lower part are fixed two booster thrusters 12 such as powder thrusters intended to ensure the propulsion of the launcher in a first phase of its launch. These booster thrusters 12 are fixed to the main body of the launcher by known structures which are not part of the invention. These structures generally include a ball joint 13 connecting the front end of each of the booster to the main body of the launcher and connecting rod systems 14 connecting the lower part of each booster to the main body.

More specifically, the connecting rods 14 are articulated on a ring 16 surrounding the lower part of each of the booster boosters 12.

 At its lower end, each booster 12 comprises an adjustable nozzle 18, the orientation of which can be modified remotely using at least two servo-cylinders (not shown), supplied with oil by a group of '' at least two juxtaposed cylindrical tanks 20.

 The cylindrical tanks 20 are filled with oil used to supply each of the aforementioned servo-cylinders. Depending on the case, these reservoirs can be pressurized with pressurized helium, or on the contrary unpressurized or weakly pressurized. They are fixed along the lower part of the corresponding booster thruster 12, so that their longitudinal axes are parallel to the longitudinal axis of this thruster. This fixing can in particular be ensured by connecting rods (not shown) connecting the upper end of each tank 20 to the ring 16 surrounding the corresponding booster 12 and by supports (not shown) directly connecting the lower end of each tank to the rear skirt 22 of the booster. To allow their fixing, the tanks 20 comprise at each of their ends a small diameter cylinder 20a, extending their hemispherical bottom, as illustrated in FIG. 2.

 According to the invention, the protuberances formed on the lower part of each of the booster boosters 12 by the groups of at least two tanks 20 are placed in an anti-vibration fairing, the detailed description of which will now be given.

 This anti-vibration fairing comprises first of all two end fairings 24 and 26, illustrated only in FIG. 1, which respectively cover the upper part and the lower part of each group of tanks 20.

 The anti-vibration fairing according to the invention further comprises, as illustrated more precisely in FIG. 2, a central fairing which connects the end fairings 24 and 26 so as to give the assembly a substantially uniform exterior profile. between these end fairings. This central fairing has not been illustrated in FIG. 1.

 More specifically, the central fairing according to the invention comprises two lateral deflectors 28, arranged on either side of each group of tanks 20, in the extension of the end fairings 24 and 26, and one or more pairs complementary internal 30a and external 30b spacers, arranged between the adjacent tanks, depending on whether the group comprises two or more tanks.

 In addition, the anti-vibration fairing according to the invention comprises traction means which are interposed between the neighboring tanks, inside the central fairing, so as to apply a prestress between these tanks without displacing them.

 As illustrated in FIG. 2, these traction means comprise first of all at least three spaced belts 32 fixed around each of the tanks 20 near its ends and in its central part. The belts 32 are metallic belts which completely enclose the tank 20 and which are glued around the latter, so that their ends are located in a location diametrically opposite with respect to the neighboring tank.

 At least one of the belts 32 which are fixed to each of the reservoirs 20, preferably situated at one of the ends of this reservoir, has, in its part facing the neighboring reservoir, projecting edges 32a (FIG. 3) which give at this point the shape of a U in the section of the belt 32. As will be seen later, these projecting edges 32a have the function of ensuring the longitudinal immobilization of the spacers 30a and 30b.

 The traction means which are interposed between the neighboring reservoirs 20 further comprise traction mechanisms 34 connecting the belts 32 together and whose structure appears more clearly in FIG. 4. As illustrated in this last figure, the attachment of each of the traction mechanisms 34 on the belts 32 which it connects is provided by two fasteners 36, 38 of section in the shape of, fixed on the belts 32. The fastener 36 is made in one piece and the fastener 38 has a removable cover 40.

 The traction mechanism 34 comprises an adjustable length rod formed by a threaded rod 42 screwed into a threaded sleeve 44 able to be immobilized on the threaded rod 42 by a nut 46. At its end opposite to the threaded rod 42 the threaded sleeve 44 comprises a collar 44a on which a self-lubricating ball joint 48 mounted on the sleeve 44 is supported. The self-lubricating ball joint 48 is designed to be received inside the fastener 38 and maintained in the latter after the removable cover 40 has been put in place .

 Furthermore, the end of the threaded rod 42 opposite the threaded sleeve 44 enters the fastener 36 through a hole 36a formed in the latter and supports inside the fastener 36 a spring cup 50 blocked by a nut 52. A prestressed compression helical spring 54 surrounding the threaded rod 42 is supported by one of its ends against the spring cup 50 and by its opposite end on the fastener 36, around the hole 36a. This compression spring 54 thus exerts a tensile force between the fasteners 36 and 38, by means of the threaded rod 42 and the threaded sleeve 44.

 Depending on the stiffness of the compression spring 54 and the value of the compression applied to it during assembly, different tensile forces can be applied between the reservoirs by each of the traction mechanisms 34. A more tensile force can thus be applied important in the central part of the tanks only near their ends.

 As a variant, it is also possible to place between the spring 54 and the fastener 36 or between the spring 54 and the spring cup 50 an elastic washer whose compression carried out during assembly makes it possible, for example, to obtain more vibration damping or less important. The total stiffness of the system then depends, in a known manner, on the stiffnesses of the spring and the washer.

 Referring again to FIG. 2, it can be seen that the side deflectors 28 both have in section the shape of a triangle, one of the sides of which is intended to be applied against the external surface of one of the end tanks of the group of reservoirs 20, has the shape of a reentrant arc of a circle complementary to this external surface. The face of each of the lateral deflectors 28 corresponding to this side in the form of a reentrant arc is intended to be glued to the corresponding tank 20, opposite the neighboring tank. Grooves 56 are provided in this face, at the location of each of the belts 32.

 When the lateral deflector 28 is glued to the reservoir 20, a flat face of this deflector is oriented substantially parallel to the external surface of the booster, without however being in contact with this surface. In order to prevent the surrounding air from entering between the lateral deflector 28 and the booster, which could have the effect of tearing off the deflector, the outer edge of the latter carries a seal 58, at Y-shaped section, which comes into contact with the external surface of the booster by two lips 60.

 The side deflectors 28 advantageously consist of an internal honeycomb structure 62, covered with a rigid coating 64 of composite material, for example consisting of a glass fiber fabric impregnated with polymerized resin.

 The complementary spacers 30a and 30b both have, to the right of the belts 32 which encircle the reservoirs 20, feet 65 (FIG. 3) which have in cross section the shape of isosceles trapezoids whose inclined sides form arcs of reentrant circle whose diameter corresponds to the outside diameter of the belts 32. The surfaces of the feet 65 corresponding to the sides in the form of the above-mentioned reentrant arcs of a circle are intended to be applied against the belts 32. Furthermore and as illustrated more precisely in FIG. the feet of the spacers 30a and 30b which are located in line with the belt or belts 32 comprising the projecting edges 32a are trapped between these edges, so that the spacers are immobilized longitudinally relative to the tanks 20, that is to say - say parallel to the axes of these tanks.

 Between their feet 65, the spacers 30a and 30b preferably have a slightly reduced section in their parts which face each other. On the other hand, the faces of the spacers 30a and 30b facing outwards are flat and continuous and completely seal the inter-reservoir space, in order to avoid any penetration of the surrounding air between these spacers.

 In the same way as the side deflectors 28 and as illustrated in FIG. 3, each of the spacers 30a and 30b preferably comprises a honeycomb structure 66, covered externally over its entire surface with a rigid covering 68 of material composite, such as a glass fiber fabric embedded in a polymerized resin matrix.

 To facilitate the installation of the spacers 30a and 30b, the cross-sectional surface in the shape of an arc of a circle returning from each of the legs 65 of the spacers and / or the surface facing the belts 32 are coated with a material facilitating sliding such as polytetrafluoroethylene 70, as illustrated in FIG. 3.

 As also shown in this figure, a layer of foam 72 can also, in order to compensate for the shape tolerances between the feet 65 and the tanks 20, be interposed between the rigid covering 68 and the material 70 promoting the sliding, on each of the feet spacers 30a and 30b, at the locations corresponding to the cross-sectional surfaces in the form of reentrant arcs.

 The arrangements which have just been described make it possible to facilitate the positioning of the spacers 30a and 30b when a force is exerted between these spacers by means of application of these spacers against the tanks 20.

 As illustrated more precisely in FIG. 5, these means of applying the spacers to the tanks comprise traction systems 74 interposed between the spacers 30a and 30b, opposite the belts 32.

 Each of these traction systems 74 comprises a ring 76 fixed, for example by means of screws 78, to the internal spacer 30a, the closest to the booster. This fixing is facilitated by the presence at this level of an insert 79 in the spacer 30a. It is performed so that the axis of the ring 76 substantially coincides with the axis of the corresponding traction mechanism 34, so that this traction mechanism passes through the ring 76 when the assembly is carried out.

 On the side facing the outer spacer 30b, the ring 76 supports a clip 80, of U-shaped section.

 In the extension of this fastener 80, the outer spacer 30b is traversed over its entire thickness by a hole 81 delimited by an insert 82. This hole 81 has a larger diameter near the outer surface of the spacer 30b, so as to form a housing 83 for a helical compression spring 84. This compression spring 84 bears, by its end facing the ring 76 against a shoulder formed in the bottom of the housing 83 and, by its opposite end, against a spring cup 86.

 A compression preload is applied to the spring 84 by an assembly of adjustable length passing through the spring cup 86, the spring 84, the hole 81 and an opening 91 formed in the clip 80.

This assembly comprises a threaded rod 90, one end of which carries a nut 88, bearing on the spring cup 86, and the end of which is located inside the fastener 80 is screwed into a threaded sleeve 92 blocked by a counter nut 94. The threaded sleeve 92 is terminated by a flange 92a. A self-lubricating ball joint 96 is blocked between the flange 92a and the part of the fastener 80 surrounding the opening 91.

 This arrangement, comparable to that of the traction mechanism 34 described above with reference to FIG. 4, makes it possible to exert between the spacers 30a and 30b a tensile force defined by the preload of the spring 84. This tensile force makes it possible to apply these spacers against the outer surface of the tanks 20 with the desired force.

 When mounting the anti-vibration fairing according to the invention, first of all, the traction mechanisms 34 are put in place between the fasteners 36 and 38, after taking care to place the rings 76 fitted with their fasteners 80 containing the self-lubricating ball joints 96.

 The assembly of each of the traction mechanisms 34 is carried out firstly by mounting the self-lubricating ball joint 48 on the threaded sleeve 44 and by introducing it into the clip 38, before closing the latter by means of the cover 40. then slides, without blocking it with the lock nut 46, the threaded rod 42 into the threaded sleeve 44. When this operation is complete, the spring 54 is put in place by compressing it using a tool appropriate. The spring cup 50 is then blocked on the threaded rod 42 using the nut 52. In order to obtain the desired deflection of the spring 54, the length of the threaded rod 42 is then screwed into the threaded sleeve 44 , then this threaded rod is blocked using the lock nut 46. The tool used to compress the spring 54 during assembly can be removed either before the length adjustment or when this adjustment is complete.

 After mounting the three traction mechanisms 34, the lower spacer 30a is put in place and approached the three rings 76 previously placed around the fasteners 36. These rings are fixed to the spacer 30a by means of the screws 78 and the spacer is kept applied against the tanks 20.

 Each of the threaded rods 90 is then screwed into the threaded sleeve 92 which corresponds to it and locked by means of the lock nut 94. The threaded rods 90 are held in this position and the outer spacer 30b is put in place, so that these threaded rods penetrate into the holes 81. The springs 84 and their cups 86 are then positioned, before compressing these springs using the nuts 88. The rotation of the threaded rod 90 is then prevented by means of a cooperating key for example with a hollow hexagonal imprint (not shown) formed at the end of this threaded rod facing outwards.

 When tightening the nuts 88, the presence of polytretrafluoroethylene 70 and possibly foam 72 facilitates the sliding and adaptation of the shapes of the spacers on the belts 32.

 It should be noted that the embodiment which has just been described can undergo a certain number of modifications without departing from the scope of the invention. Thus, the number of tanks 20 protected by the anti-vibration fairing can be greater than two and these tanks can be replaced by accessories of another type, which may possibly have slightly different dimensions. Furthermore, it should be noted that these accessories could be fixed not on booster boosters of a launcher but directly on the main body of the latter, or on a spacecraft of a different nature such as an aircraft or a spaceship.

 Furthermore, the number of belts 32 and, consequently, of the traction mechanisms 34 and of the traction systems 74 may be greater than three.

In addition, it should be noted that these traction mechanisms and these traction systems can be simplified by replacing the compression springs with traction springs and by directly fixing the ends of these springs on the clips 36 and 38 for the mechanisms 34. and on the fasteners 80 and on the upper spacer 30b for the systems 74.

 In addition, when the accessories with which the anti-vibration fairing is associated consist of pressure tanks, which lengthen by a few millimeters at the time of launch, the initial positioning of the feet of the spacers 30a and 30b takes this elongation into account, so that the feet of the spacers are perfectly opposite the belts 32 when the tanks are pressurized.

 Finally, the end fairings 24 and 26 can be produced separately from the central fairing, as shown, or in one piece with the spacers and the side deflectors.

Claims (13)

 1. Anti-vibration fairing for a group of at least two substantially cylindrical juxtaposed accessories (20), of similar dimensions, fixed to a spacecraft, characterized in that it comprises two end fairings (24,26) connected by a central fairing (28,30a, 30b) and traction means (32,34) interposed between neighboring accessories, inside the central fairing, so as to apply a prestress between these accessories.  2. Fairing according to claim 1, characterized in that the traction means comprise at least three spaced belts (32) fixed around each of the accessories (20), and traction mechanisms (34) connecting the belts of the neighboring accessories.  3. Fairing according to claim 2, characterized in that each of the traction mechanisms (34) comprises at least one first prestressed elastic means (54).  4. Fairing according to any one of the preceding claims, characterized in that the central fairing comprises two lateral deflectors (28) fixed on two extreme accessories from the group of accessories, on either side of this group, in the extension of the end fairings, and the outer edges of which carry seals (58) which are in contact with the spacecraft supporting said accessories.  5. Fairing according to claim 4, characterized in that the side deflectors (28) are glued to the accessories.  6. Fairing according to any one of claims 4 and 5, characterized in that the lateral deflectors (28) comprise an internal honeycomb structure (62), covered with a rigid covering (64) of composite material .  7. Fairing according to any one of claims 4 to 6, characterized in that each of the seals (58) comprises at least two lips (60) which are in contact with the spacecraft.  8. Fairing according to any one of the preceding claims, characterized in that the central fairing comprises, between each pair of juxtaposed accessories, two complementary spacers (30a, 30b) connected by application means (74) of the spacers on accessories.  9. Fairing according to claim 8, combined with any one of claims 2 and 3, characterized in that a first at least of the three belts (32) fixed around each of the accessories (20) comprises means of longitudinal immobilization (32a) of the spacers (30a, 30b).  10. Fairing according to claim 9, characterized in that the spacers (30a, 30b) comprise feet (65) in arcs of circles intended to be supported on said belts (32), the longitudinal immobilization means comprising protruding edges (32a) formed on the first belt, between which are trapped corresponding feet of complementary spacers (30a, 30b).  11. Fairing according to claim 10, characterized in that the spacers comprise an internal honeycomb structure (66), covered with a rigid coating (68) of composite material, and in that a material promoting the sliding covers at least one of the surfaces in contact with the belts (32) and the feet (65) of the spacers.  12. Fairing according to claim 11, characterized in that the rigid coating (68) of the spacers is covered with foam (72) on the surfaces of the feet (65) in contact with the belts (32).  13. Fairing according to any one of claims 8 to 12, combined with one of claims 2 and 3, characterized in that the means for applying the spacers to the accessories comprise at least three traction systems (74) each comprising a second prestressed elastic means (84) and a ring (76) through which one of the traction mechanisms (34) passes.