Improved nozzle thermal protection

Abstract

1. A nozzle 1 for a spacecraft engine, the nozzle 1 comprising a nozzle body 10 extending along a main direction ZZ from a proximal end 12 fixed to the spacecraft engine, the nozzle body 10 having a plurality of stiffeners 20 extending radially from an outer surface of the nozzle body 10 relative to the main direction ZZ, the nozzle 1 comprising a thermal insulation system comprising at least one strip of insulating material 30 arranged to surround the outer surface of the nozzle body 10 over at least a portion of the height of the nozzle body 10, the thermal insulation system comprising a plurality of retaining elements 40, each retaining element 40 positioned to surround a strip of insulating material 30 and arranged between two stiffeners 20 of the nozzle body 10.

Description

[Technical field]

[0001] The present disclosure relates to the field of space launchers, and more particularly, to nozzles for space launchers. [Background technology]

[0002] The space launcher includes an engine having a nozzle, commonly referred to as a divergent nozzle, which guides the flow of fluid generated by the engine.

[0003] The nozzle must therefore withstand both thermal and mechanical stresses, but the constraints specific to space launchers, particularly in terms of space requirements, mass, and cost, make these stress-responsive properties particularly complex.

[0004] Known devices, such as those presented in particular in patent application FR 3 060 062 and patent application FR 3 074 539, propose the use of a rigid insulating block, which is positioned around the nozzle. However, the above devices entail significant constraints for the manufacture of the insulating block, which must be manufactured to perfectly correspond to the nozzle geometry. The invention therefore aims to propose an insulating structure that does not have such constraints. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] French Patent Application Publication No. 3060062 [Patent Document 2] French Patent Application Publication No. 3074539 Summary of the Invention

[0006] In order to at least partially address these challenges, the present disclosure relates to a nozzle for a spacecraft engine as set forth in claim 1, the nozzle comprising a nozzle body extending along a main direction from a proximal end fixed to the spacecraft engine and a free distal end, the nozzle body having a plurality of stiffeners extending radially from an outer surface of the nozzle body, the nozzle comprising a thermal insulation system, the at least one strip of insulating material arranged to surround the outer surface of the nozzle body over at least a portion of a height of the nozzle body, the height being measured along the main direction, the thermal insulation system comprising a plurality of retaining elements, each retaining element being positioned to surround a strip of insulating material and being disposed between two stiffeners of the nozzle body.

[0007] According to one example, each holding element comprises a cable associated with a tensioning system.

[0008] According to one example, each holding element comprises a covering made of a thermal insulating material.

[0009] According to one example, the tensioning system is a turnbuckle.

[0010] According to one example, a retaining element is arranged in each space between two stiffeners.

[0011] According to one example, the insulation system comprises at least two overlapping strips of insulating material.

[0012] According to one example, the insulation system comprises a plurality of strips of insulating material, each strip of insulating material positioned to at least partially cover an adjacent strip of insulating material.

[0013] The present disclosure also relates to a spacecraft comprising a nozzle as described above.

[0014] The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention, given by way of non-limiting example. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 shows an example of a nozzle structure. [Diagram 2] FIG. 2 is a detailed schematic diagram of the nozzle stiffener arrangement. [Diagram 3] FIG. 3 shows an example of an insulation system. [Figure 4] FIG. 4 shows an example of an insulation system. [Diagram 5] FIG. 5 illustrates the effect of tensioning the retention elements of an example insulation system and is a schematic diagram of the system before tensioning. [Figure 6] FIG. 6 illustrates the effect of tensioning the retention elements of one example insulation system and diagrammatically represents the system after tensioning the retention elements. [Figure 7] FIG. 7 shows an example of an insulation system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In all figures, common elements are identified by the same reference numbers.

[0017] FIG. 1 shows an example of the structure of a nozzle 1 .

[0018] The nozzle 1 as presented has a nozzle body 10 having the general shape of a truncated cone about a main axis ZZ defining a main direction, with curved walls.

[0019] The height of the nozzle 10 is defined along a principal axis ZZ which extends between a proximal end 12, typically fixed to an engine of a space launcher, and a distal end 14, typically free, the nomenclature of "proximal" and "distal" being arbitrary herein.

[0020] The nozzle body 10 includes a plurality of stiffeners 20. Each stiffener 20 is typically a rib extending from the outer surface of the nozzle body 10 in a radial direction relative to the primary axis ZZ.

[0021] The stiffeners 20 are typically evenly spaced apart and extend from the distal end 14 over all or a portion of the height of the nozzle 1, typically between 50% and 80% of the height of the nozzle 1. Figure 2 shows an example of a detailed view depicting the arrangement of the stiffeners 20.

[0022] The reinforcement 20 typically has a dimension, measured along a radial direction relative to the main axis ZZ, comprised between 30 and 60 mm.

[0023] The stiffeners 20 are typically spaced apart by a distance comprised between 30 and 100 mm measured along the direction defined by the main axis ZZ.

[0024] To achieve thermal insulation of the nozzle 1, a thermal insulation system is arranged around the nozzle body 10 over all or part of its height.

[0025] 3 and 4 show an example of an insulation system in which a strip of insulating material 30 and a number of retaining elements 40 are positioned around a portion of a nozzle body 10 including a stiffener 20.

[0026] The strip of insulating material 30 is sized to cover at least two consecutive stiffeners 20. In the illustrated example, two strips of insulating material 30 are positioned, each extending the full height of the nozzle body 10 including the stiffeners 20, but covering only a portion of the circumference of the nozzle body 10.

[0027] According to one example, the insulation system comprises one or more strips of insulating material 30 forming a panel, these strips being positioned so as to overlap from end to end or at their junctions or to cover all of the reinforcement 20. Each strip of insulating material 30 typically has sufficient dimensions to be able to go completely around the nozzle body 10. The two distal ends of the strip of insulating material 30 then typically overlap over a defined width, typically comprised between 30 and 100 mm, to ensure the continuity of the thermal protection. As a variant, the strip of insulating material 30 can be dimensioned to cover only a portion of the outer periphery of the nozzle body 10. To cover the entire circumference of the nozzle body 10, it is therefore necessary to position several strips of insulating material 30. The strips of insulating material 30 are then positioned so as to ensure the continuity of the thermal protection, their adjacent distal ends overlapping over a defined width, typically comprised between 30 and 100 mm. More generally, the strips of insulating material 30 may overlap along a direction defined by the main axis ZZ and / or along the circumference of the nozzle body 10 .

[0028] The strip of insulating material 30 used to wrap the nozzle body 10 can be identical or different, especially with regard to dimensions. For example, the strip of insulating material 30 can consist of a casing made of alumina fibers, silica and boron oxide, for example fibers of the material sold under the name "Nextel®", which is filled with an insulating material made of polycrystalline wool, for example the material sold under the name "Fibermax®". The strip of insulating material 30 is a flexible element that can be freely positioned around the nozzle body 10, independently of the parts of the nozzle and the arrangement of the stiffeners 20.

[0029] The retaining elements 40 are then positioned around the nozzle body 10. Each retaining element 40 is positioned between two successive reinforcements 20. The retaining elements 40 are typically elastic means, means with elastic or tensioning functions, or straps connected to a tensioning system. According to one example, each retaining element 40 typically comprises a metal cable surrounded by an insulating material and a tensioning system such as a turnbuckle. By way of example, the retaining elements 40 may be composed of a steel cable or a material sold under the name "Inconel®", the cable being surrounded by an insulating material typically made of a material sold under the name "Fibermax®", which is surrounded by a casing made of a material sold under the name "Nextel®" or a material made of one or more layers of a material sold under the name "Nextel®". The cable may also be made from a material sold under the name "Fibermax®", fiberglass surrounded by insulation, or carbon fiber.

[0030] The tensioning of each retaining element 40 will enclose the strip of insulating material 30 that is enclosed between the nozzle body 10 on the one hand and the retaining element 40 on the other hand. This tensioning thus accommodates the retaining element in the space between two successive reinforcements 20 as well as between the strips of insulating material 30. The tensioning of the different retaining elements 40 thus makes it possible to substantially deform the strip of insulating material 30 to conform to the geometric shape of the nozzle body 10 with the reinforcements 20 and to obtain a continuous and stable layer of insulation around the nozzle body 10.

[0031] According to one example, a retaining element 40 is positioned in each space between two successive stiffeners 20, as represented for example in FIG.

[0032] Figures 5 and 6 show the effect of tensioning the retaining element 40 on a portion covering the strip of insulating material 30. As mentioned above, the strip of insulating material 30 disposed around the nozzle body 10 is typically dimensioned such that their ends overlap over a defined width. This is shown diagrammatically in Figure 5. When tensioning the retaining element 40, it then compresses the strip of insulating material 30, particularly the overlapping portion, to obtain a substantially uniform thickness, as diagrammatically represented in Figure 6.

[0033] 7 depicts one exemplary embodiment in which two strips of insulating material 30 are superimposed, designated by reference numerals 30a and 30b to indicate the strip of insulating material in contact with the nozzle body 10 and the outermost strip of insulating material, respectively.

[0034] Tensioning of the retaining element 40 causes the different strips of insulating material 30 a and 30 b to conform over the exterior surface of the nozzle body 10 having the stiffener 20 .

[0035] During operation, any air between the divergent nozzle 10 and the insulating material 30a, and any air present between the different strips of insulating material 30, will typically escape in the portion covering the distal ends of the strips of insulating material as represented diagrammatically in Figures 5 and 6.

[0036] It is understood that this exemplary embodiment is not limiting and any number of strips of insulating material 30 may be overlapped to obtain the desired properties, and the operation remains unchanged. The use of several overlapped strips of insulating material 30 allows in particular the use of strips of insulating material 30 having distinctive properties, in particular in terms of thickness and / or thermal properties and / or mechanical properties.

[0037] The proposed insulation system is particularly advantageous for the following reasons:

[0038] This has good resistance to blast waves and vibrations of the nozzle 1 due to the ignition of the auxiliary booster of the spacecraft. The strip of insulating material 30 bears over its entire surface against the outer wall of the nozzle body 10, which is in fact rigid, and has good resistance to external vacuum pressure, since any air present between the nozzle body 10 and the strip of insulating material 30 or between different strips of insulating material 30 can escape in the areas covering the strip of insulating material 30.

[0039] The insulation system is also advantageous in terms of installation, since it does not require any structural modifications to the nozzle 1 and only the addition of a strip of insulating material and a tensioning element. Its mass and cost are also low. Moreover, the different elements of the proposed insulation system are not subjected to mechanical stress during operation, so that the reliability of the insulation system is guaranteed. Moreover, unlike known devices using rigid insulating elements, the strip of insulating material 30 does not require specific dimensions in order to fit the geometry of the nozzle 1. The strip of insulating material 30 is flexible and can be freely positioned around the nozzle body 10, and the fit to the geometry of the nozzle 1 is guaranteed during the tightening of the holding element 40.

[0040] Although the invention has been described with reference to specific exemplary embodiments, it is apparent that modifications and variations can be made to these embodiments without departing from the scope of the invention as defined by the claims. In particular, the individual characteristics of the different embodiments shown and described can be combined in additional embodiments. The specification and drawings are therefore to be considered in an illustrative rather than a restrictive sense.

[0041] It is also clear that all features described with reference to a method, either alone or in any combination, may be substituted for an apparatus, and conversely, all features described with reference to an apparatus, either alone or in any combination, may be substituted for a method.

Claims

1. In the nozzle (1) of a spacecraft engine, The nozzle (1) comprises a nozzle body (10) extending along a main direction (Z-Z) from a proximal end (12) fixed to the engine of the spacecraft to a free distal end (14); The nozzle body (10) has a plurality of stiffeners (20) extending radially from an outer surface of the nozzle body (10) relative to the main direction (Z-Z); The nozzle (1) is provided with a thermal insulation system, the insulation system comprises at least one strip of flexible insulating material (30) disposed to surround the exterior surface of the nozzle body (10) over at least a portion of the height of the nozzle body (10); the height is measured along the main direction (Z-Z); The insulation system comprises a plurality of retention elements (40); Each retaining element (40) is disposed between two stiffeners (20) of said nozzle body (10); A nozzle (1) for a spacecraft engine, wherein each of the retaining elements (40) surrounds the strip of flexible insulating material (30) and is positioned to fit over the strip of flexible insulating material (30) on the outer surface of the nozzle body (10) and over the stiffener (20), and each of the retaining elements (40) has a covering made of a thermal insulating material.

2. The nozzle (1) according to claim 1, wherein each holding element (40) comprises a cable associated with a tensioning system.

3. The nozzle (1) according to claim 2, wherein the tensioning system is a turnbuckle.

4. Nozzle (1) according to any one of claims 1 to 3, wherein a retaining element (40) is arranged in each space between said two stiffeners (20).

5. Nozzle (1) according to any one of the preceding claims, wherein the thermal insulation system comprises at least two superimposed strips of the flexible insulating material (30).

6. The nozzle (1) according to any one of claims 1 to 5, wherein the insulation system comprises a plurality of strips of flexible insulating material (30), each strip of flexible insulating material (30) positioned to at least partially cover an adjacent strip of flexible insulating material (30).

7. A spacecraft comprising a nozzle (1) according to any one of the preceding claims.

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