CRYOSTIST FOR A ROOM COMPONENT

Description

DOMAINE TECHNIQUE

[0001] The present invention relates to the field of the space industry, in particular to thermal control devices for artificial satellites, space probes and the like.

[0002] The invention relates more particularly to a cryostat, intended to receive a component, such as for example an optical component, operating at very low temperature. The cryostat is intended to be embarked, with the component, in a spacecraft such as a satellite, for example a scientific Earth observation satellite. ÉTAT DE L'ART

[0003] Some space components, such as infrared optical detectors, must be operated at very low, stabilized temperatures, known as cryogenic temperatures, to ensure their performance. For infrared (IR) imaging, for example, a cryostat allows for temperature decoupling between the satellite platform on which the cryostat is fixed and the interior of the cryostat in which the optical component is enclosed, including IR sensors designed to operate at cryogenic temperatures (around 60K).

[0004] FR2410211 discloses a liquid cryogen (helium) cryostat intended to cooperate with an optical system, for example in the context of astrophysics and infrared spectroscopy experiments. The cryostat comprises a tank containing liquid helium, suspended inside a sealed enclosure in which a vacuum has been created. The tank is provided with a neck on which are mounted heat exchangers intended to recover the enthalpy of the cryogenic gas and on which are in turn mounted radiation panels cooled by the exchangers and intended to limit the energy transmitted to the helium bath as a result of external radiation and thermal conduction in the neck of the tank and in its suspension members.

[0005] This type of cryostat has a particularly complex architecture, composed of a large number of assembled parts, which results in long and costly integration processes. The assembly of these parts is all the more critical given that the space sector requires compliance with very demanding geometric, mechanical and thermal specifications. Furthermore, this type of architecture generally limits the size and shape of the devices that it can accommodate in a useful space of limited volume.

[0006] US 3,253,423 discloses another cryostat of complex manufacture. PRESENTATION DE L'INVENTION

[0007] The invention aims to overcome at least one of the aforementioned drawbacks. In particular, one objective of the invention is to propose a cryostat of simple architecture, easy to manufacture at a controlled cost, and capable of housing components of various shapes and sizes, while having a reduced size and mass. Another objective of the invention is to provide a cryostat capable of withstanding temperature variations between its external and internal environment as well as significant accelerations and mechanical forces, without this altering its performance.

[0008] To do this, the invention proposes a cryostat intended to accommodate at least one spatial component operating at cryogenic temperature, the cryostat comprising: a central enclosure, closed and cooled, configured to receive the spatial component, successive metal screens, spaced from each other, including an inner screen, an outer screen and one or more intermediate screens, the inner screen being configured to support said spatial component and delimiting the central enclosure to receive said spatial component, the intermediate screen(s) and the outer screen being arranged around each other so as to each delimit a closed volume receiving the previous screen of smaller size, a cooling device for cooling the central enclosure to cryogenic temperature, external securing elements fixed to the outer screen, for securing the cryostat to a satellite platform, internal junction elements between screens, which keep said screens spaced from each other.

[0009] The cryostat according to the invention is characterized in that it comprises at least one single-piece part comprising a succession of partitions including an interior partition, an exterior partition and one or more intermediate partitions, corresponding respectively to a part of the interior screen, a part of the exterior screen and a part of the intermediate screen(s), said partitions being spaced from each other and held together by at least a part of the interior junction elements between screens.

[0010] According to a possible characteristic, the cooling device comprises one or more cold fingers for cooling the central enclosure and, for each of the cold fingers, a transverse passage passing through the successive metal screens to the central enclosure to receive said cold finger, the cold finger(s) not being in contact with the screens.

[0011] According to a possible characteristic, the interior junction elements between screens are arranged between the successive screens and configured to ensure by themselves a mechanical hold between the exterior screen and the interior screen, said interior junction elements being configured to withstand determined forces induced at least by a mass of the spatial component and masses of the screens.

[0012] According to a possible characteristic, the internal junction elements between screens comprise double V-shaped rods between the successive screens, the Vs being distributed angularly around a main axis or a central point of the cryostat in at least three radial directions.

[0013] According to a possible characteristic, the interior junction elements between screens comprise several sets of simple rods, the simple rods of the same set being aligned along a straight line crossing the screens, the straight lines of two distinct sets being non-parallel and non-coplanar with each other.

[0014] According to a possible characteristic, the interior junction elements between screens are made in a single block with at least part of the screens.

[0015] According to a possible feature, the single-piece part of the cryostat is made by additive manufacturing.

[0016] According to a possible characteristic: the cryostat comprises a plurality of single-piece parts as previously defined, that is to say each having an interior partition, an exterior partition and one or more intermediate partitions, the partitions of two separate single-piece parts among said single-piece parts corresponding to two separate parts of the screens, the intermediate or interior partitions, of two separate and adjacent single-piece parts among the plurality of single-piece parts, which are in the extension of one another being non-contiguous, the exterior partitions, of two separate and adjacent single-piece parts among the plurality of single-piece parts, which are in the extension of one another being contiguous and fixed to one another.

[0017] In other words, two adjacent one-piece parts are fixed to each other by their outer partitions and only by them.

[0018] According to a possible characteristic, the intermediate or interior partitions which are in the extension of one another, have opposite ends of which at least one of these opposite ends has a step so as to form a chicane with the other opposite end.

[0019] According to a possible characteristic, the external securing elements are either all fixed on the external partition of only one of the single-block parts, or distributed on the external partitions of several of the single-block parts.

[0020] According to a possible characteristic, at least one of said single-piece parts is an annular structural part of which each interior, intermediate and exterior partition is annular.

[0021] According to a possible feature, each of the cryostat screens is entirely formed by the assembly of the partitions of the single-piece parts.

[0022] Alternatively, the cryostat comprises at least one single-piece annular structural part as previously defined and: the cryostat comprises at least one series of independent covers including, for each series, an inner cover, an outer cover and one or more intermediate covers, each series of covers corresponding respectively to another part of the screens, the covers of the same series being arranged one inside the other, at a distance from each other, without internal joining elements; in other words, unlike the partitions of the annular structural part (or more generally of the aforementioned monobloc parts), the covers are not directly linked together; each of said covers coming in the extension of and being fixed to one of the partitions of said annular structural part, each of the screens of the cryostat thus being entirely formed by at least one of the partitions of the annular structural part and by one of the covers of each series.

[0023] It should be noted that, in this variant, the cryostat may comprise several single-piece parts corresponding to different parts of the screens, the screens being integrally formed by the addition (to the partitions of said single-piece parts) of one or more series of independent covers, corresponding respectively to one or more other parts of the screens.

[0024] According to one possible feature, at least a portion of each of the covers is provided with a gold coating.

[0025] According to a possible characteristic, each of the cold fingers defined above is thermally insulated from the screens, a thermally insulating coating being arranged against at least one of the cold fingers in the transverse passage of said cold finger and / or a thermally insulating bellows coating being arranged, around at least one of the cold fingers, in the transverse passage of said cold finger and between the screens.

[0026] The invention extends to a spacecraft, for example a satellite, characterized in that it comprises a space component, which operates at cryogenic temperature and is arranged in a cryostat according to the invention, the cryostat being fixed on a platform of the spacecraft.

[0027] The fundamental concepts of the invention having just been set out above in their most elementary form, other details, characteristics and advantages will emerge on reading the description which follows and with reference to the appended drawings, giving as non-limiting examples of the embodiment of a cryostat in accordance with the principles of the invention. BREVE DESCRIPTION DES FIGURES

[0028] There figure 1 is a schematic perspective view of a first example of a cryostat according to the invention, comprising two single-piece parts. The figure 2 represents the cryostat of the figure 1 seen in section along a median longitudinal plane. The figure 3 is a front view of a single-piece part of the cryostat of the figure 1 . There figure 4 is a perspective view of the one-piece part of the figure 3 , on the closed side. The figure 5 is another perspective view of the one-piece part of the figure 3 , on the open side. The figure 6 is a perspective view, from the closed side, of the other single-piece part of the cryostat of the figure 1 . There figure 7 is another perspective view of the one-piece part of the figure 6 , on the open side. The figure 8 represents the cryostat screens of the figure 1 , seen in section through a transverse plane, showing interior V-shaped junction elements. The figure 9A is a partial section along a longitudinal plane AA of the screens of the figure 8 . There figure 9B is a partial section along a longitudinal plane BB of the screens of the figure 8 . There figure 10 is a schematic sectional view of the cryostat of the preceding figures with its two assembled monobloc parts, showing the configuration of the internal joining elements. figure 11 is a perspective view of the one-piece part of the figure 3 and a space component operating at cryogenic temperature, shown separately and intended to be housed therein. The figure 12 is a front view of the one-piece part of the figure 3 containing the spatial component with, separately represented, functional organs of the cryostat, such as cold fingers. The figure 12A represents a cold finger passing through the screens according to an exemplary embodiment. The figure 12B represents a cold finger passing through the screens according to another exemplary embodiment. The figure 13 represents the elements of the figure 12 assembled, seen from the front. The figure 14 is a perspective view of the cryostat of the figure 12 fully assembled. The figure 15 is an exploded perspective view of a second example of a cryostat according to the invention, comprising three single-piece parts, namely an annular central part, a base and a cover. The figure 16 is a perspective view of the annular central portion and base of the cryostat of the figure 15 , with one or more detectors and their equipment (the spatial component) fixed to the base. The figure 17 is a perspective view of the cryostat of the figure 15 containing the space component operating at cryogenic temperature, before its closure by the cover. The figure 18 is a top view of the cryostat of the figure 17 without the cover. The figure 18bis shows a detail of the arrangement of the ends of partitions forming screens, relating for example to the second example of cryostat of the figures 15 à 18 . There figure 19 is an exploded perspective view of a third example of a cryostat according to the invention, comprising an annular monobloc part and two series of covers. The figure 20 is a sectional view through a median longitudinal plane of the cryostat of the figure 19 equipped with various functional organs and containing a space component operating at cryogenic temperature. The figure 21 shows a detail of the figure 20 , in perspective. The figure 22 shows a satellite according to the invention.

[0029] The different figures and the elements of the same figure are not necessarily represented at the same scale. Furthermore, these figures are all schematic, with varying degrees of detail. Finally, note that, in all the figures, identical or equivalent elements bear the same numerical reference. DESCRIPTION DETAILLEE

[0030] In the present description, reference is made to a cryostat intended primarily for an optical instrument, such as an infrared interferometer, on board a meteorological type satellite. This non-limiting example is given for a better understanding of the invention and does not exclude the use of the cryostat in other applications, for example to cooperate with other measuring instruments in observation, telecommunications or astrophysical study satellites.

[0031] Throughout the description, the term “satellite” designates an artificial satellite, and the synonymous expressions “additive manufacturing” and “3D printing” are used interchangeably to designate any computer-assisted process for shaping a part by stacking successive layers or by any addition of material.

[0032] The space component operating at cryogenic temperature is, for example, a sensitive component constituting a detector such as an optical detector.

[0033] There figure 1 represents a cryostat 100 according to a first exemplary embodiment formed from two single-piece parts 10a and 10b, joined together.

[0034] Each single-piece part 10a, 10b comprises a succession of partitions including an interior partition 13a(1), 13b(1), an exterior partition 13a(3), 13b(3) and intermediate partitions 13a(2), 13b(2).

[0035] External securing elements 20 allow the cryostat to be fixed to a satellite platform (not shown).

[0036] When assembled, the single-piece parts 10a and 10b form a succession of closed metal screens 13, arranged around each other. The inner, intermediate and outer partitions of the single-piece parts thus form respectively an inner screen, intermediate screens and an outer screen.

[0037] As seen on the figure 2 , the smaller screen 13, located inside all the others, delimits a closed central enclosure 14 whose useful volume has a shape and dimensions adapted to the integration of one or more spatial components operating at low or very low temperatures (of the order of 60K for example).

[0038] The inner metal screen that delimits the cryogenic enclosure is, for example, not watertight but forms a barrier to thermal radiation. The intermediate metal screens are, for example, not watertight but each form a barrier to thermal radiation.

[0039] In the illustrated example, the body 10 generally has a symmetry of revolution around a longitudinal axis X.

[0040] The single-piece structural parts 10a and 10b each have (see Fig. 4 And 6 ) a cylindrical external partition 11a, 11b, open on one side with a circular section and extended on the other side by a conical portion 12a, 12b. The open circular side is provided with a circular fixing flange 111a and 111b. These flanges allow a junction and a fixing of the external partitions between them, for example via suitable tightening means such as bolts inserted into facing holes.

[0041] Each interior partition 13a(1) or respectively intermediate partition 13a(2) of the single-piece part 10a is arranged in the extension of an interior partition 13b(1) or respectively intermediate partition 13b(2) of the single-piece part 10b. The facing ends 130a and 130b of two interior or intermediate partitions located in the extension of one another remain at a distance from one another. The areas of rapprochement of these facing ends are offset longitudinally (that is to say that these areas of rapprochement between interior or intermediate partitions are not located in the same transverse plane) to increase the barrier effect to thermal radiation and allow their assembly while maintaining a reduced distance between successive screens.

[0042] Providing non-joining intermediate and interior partitions in this way makes it possible to limit the friction between the partitions and the erosion of the partitions which occurs at their junction under the effect of the vibrations to which the cryostat is subjected. Such erosion must be avoided because it can produce particles likely to detach from the partitions, migrate towards the central enclosure of the cryostat and pollute the spatial component located there.

[0043] Furthermore, one of the facing ends 130a is extended in a U-shaped profile to create a baffle 130c with the other end 130b, and thus further increase the barrier effect to thermal radiation. Alternatively, one and / or the other of the facing ends could have been extended in an L-shaped profile.

[0044] The formation of such a 130c chicane at the crossing of a screen makes it possible to limit radiative heat exchanges between consecutive screens by forming barriers.

[0045] In order to maintain the space component operating at cryogenic temperature at low or very low temperatures, the enclosure 14 is cooled by two cold fingers 60 each arranged in a transverse passage 15 passing through the successive metal screens from the outer screen to the inner screen to arrive at the central enclosure 14.

[0046] One could also consider a cryostat operating using a single cold finger.

[0047] The body 10 of the cryostat thus comprises a succession of metal screens 13. These screens each act as an obstacle to thermal radiation and thus allow the central enclosure 14 to be kept at regulated temperatures. All of the screens thus perform a thermal insulation function for the space component operating at cryogenic temperature in relation to the external space environment and in relation to the satellite platform.

[0048] In the example presented, each single-piece part 10a, 10b comprises a plurality of successive partitions 13a, 13b, coaxial and spaced from one another which, when the single-piece parts are assembled, integrally form the successive screens.

[0049] The partitions 13a, 13b of each single-piece part 10a, 10b may, for example, have identical shapes but with increasing sizes from the inner partition 13a(1), 13b(1) to the outer partition 13a(3), 13b(3), passing through successive intermediate partitions 13a(2) and 13b(2). Thus, in the two single-piece parts, the partitions comprise cylindrical sections open at one end and closed at the other end by substantially conical sections.

[0050] Each of the two single-piece parts is a structural part, each of whose interior, intermediate and exterior partitions has an annular portion. The annular portion of each partition is extended, in a single block, by a conical closed portion.

[0051] The circular openings of the partitions each come opposite a circular opening of another partition to form a screen. Thus each screen is composed of a conical portion extended by a portion of circular section itself coming in the extension of another circular portion extended by a conical portion.

[0052] The two single-block parts include an identical number of partitions (eight in the example illustrated, i.e. six intermediate partitions), which are therefore combined in pairs, the number of partitions being able to vary depending on the insulation performance required.

[0053] The paired intermediate partitions 13a(2) and 13b(2) have their circular section portion opposite and in line with each other.

[0054] The two single-piece parts 10a and 10b are also fixed together by the fixing flanges 111a, 111b at their external partition.

[0055] The opposite and distant ends of the intermediate partitions also form, for example, a step. For each pair of associated partitions 13a(2), 13b(2), the end of one of the partitions, for example the end 130a of the partition 13a(2), has a U-shaped section over its entire periphery, which defines a “female” part, inside which the end 130b, as the “male” part, of the other partition 13b(2) projects, which has a straight section over its entire periphery. These two ends remain at a distance from each other. The same applies to the interior partitions 13a(1) and 13b(1).

[0056] The distribution of the male and female parts may be, for example, alternated between the partitions 13a, 13b of one and the other of the single-piece parts.

[0057] The area of ​​convergence between two partitions 13a and 13b thus forms a baffle 130c which helps to limit thermal radiative exchanges between two successive screens 13.

[0058] This rapprochement zone is preferably carried out without contact, in order to limit friction between partitions under the effect of vibrations to which the cryostat is subjected. The successive metal screens thus create successive non-watertight obstructions.

[0059] The junctions (i.e. the areas of rapprochement) follow, for example, a truncated cone arrangement, shown in a broken line on the figure 2 .

[0060] So, as illustrated in the figure 5 , the partitions 13a of the single-piece part 10a for example protrude relative to the plane containing the assembly face of the flange 111a, with an increasing projection length from the outer partition 13a(3) to the inner partition 13a(1). The partitions 13b of the single-piece part 10b, visible on the figure 7 , are set back relative to the plane containing the assembly face of the flange 111b, with an increasing setback length from the outer partition 13b(3) to the inner partition 13b(1), so that the single-piece part 10b has a shape complementary to that of the single-piece part 10a, to allow a connection according to the configuration illustrated in figure 2 .

[0061] The interior partitions 13a(1) and 13b(1) of the monobloc structural parts 10a and 10b have an identical diameter D which delimits useful volumes 14a and 14b respectively, the association of which forms the central enclosure 14 receiving the spatial component to be cooled.

[0062] It should be remembered that the thermal insulation provided by the cryostat 100 requires that the screens 13 be spaced apart from each other and maintained in this position. In addition, the junction elements coming into contact with two successive screens are optimized to limit heat exchange by conduction.

[0063] To this end, the partitions 13a, 13b of each single-piece part 10a, 10b are connected to each other by internal joining elements 30, the arrangement of which makes it possible to optimize both the stiffness, the mechanical strength and the thermal conduction of the mechanical-thermal structure of the cryostat. The cryostat as a whole thus has good thermal resistance between the central enclosure 14 and the external environment. The cryostat also has good stiffness and mechanical strength taking into account the conditions of use of the cryostat, which can be extreme in terms of accelerations and vibrations experienced (in particular during the launch phase of the spacecraft in which the cryostat is installed).

[0064] The cryostat as a whole thus has good thermal resistance between the central enclosure 14 and the external environment.

[0065] For example, in each single-piece part, the internal joining elements 30 may be distributed radially in several groups uniformly distributed over 360°. For example, the internal joining elements 30 are distributed in three groups along three straight lines forming two by two an angle of 120° as shown in the figure 3 .

[0066] Furthermore, external securing elements 20 hold the external screen, and therefore the body 10 of the cryostat, to a satellite platform (not shown). These external securing elements are optimized both in mechanical terms so as to guarantee good retention of the cryostat, and in thermal terms, so as to limit heat exchanges between the body 10 of the cryostat and its external environment (in particular said satellite platform).

[0067] The external securing elements 20 are, for example, in the shape of bipods and each comprise two V-shaped branches 21 which each end in a sole 22 allowing the cryostat to be fixed to the satellite platform, for example, by suitable holes 221 which will receive specific fixing elements such as screws, washers and nuts.

[0068] In the illustrated example, the cryostat 100 comprises three external bipods 20, two of which are bipods 20a secured to one of the single-piece parts 10a, and one bipod 20b secured to the other single-piece part 10b. By virtue of the different orientations of the bipods, all degrees of freedom of the external screen 13(3) relative to the satellite platform are eliminated.

[0069] The single-piece part attached to two bipods is, for example, intended to support the space component operating at cryogenic temperature.

[0070] As shown in the figure 4 , the space component operating at cryogenic temperature, such as an optical detector, operates through a front window 121, arranged at the top of a conical portion and closed by one or more panes.

[0071] The external bipods 20 connect the cryostat 100 to a satellite platform, being physically in contact with the latter, and therefore constitute a conduction medium in which thermal diffusion is established between the platform and the cryostat.

[0072] The internal junction elements 30, connecting the screens 13 together, also provide mechanical support, while limiting thermal transfers by conduction, thanks to specific arrangements.

[0073] Single-piece parts comprising several partitions, each forming a portion of screen, can be obtained by additive manufacturing (3D printing).

[0074] The interior junction elements between screens are, for example, made from a single block with partitions, particularly if additive manufacturing is used.

[0075] The construction material is for example invar or titanium.

[0076] The geometric arrangement of the interior joining elements 30, between the screens 13 will for example be optimized and validated by series of simulations and mechanical and thermal tests carried out using computer tools and experimental installations.

[0077] THE figures 8 , 9A et 9B schematically show a geometric arrangement of the internal junction elements 30 according to an exemplary embodiment of the invention. For better readability, the screens 13 are shown in reduced number in these figures. This geometric arrangement was chosen on the basis of mechanical and thermal simulations; it makes it possible to obtain the expected results in terms of mechanical strength and thermal resistance.

[0078] As shown in the figure 8 , the internal joining elements 30 are distributed in three radial directions, that is to say in three groups uniformly distributed over 360° in a transverse plane, the axes of said groups defining two by two an angle here equal to 120°. For each single-piece part, each group of internal joining elements comprises for example an internal joining element 30 between each pair of consecutive screens.

[0079] The internal junction elements between screens are optimized in terms of section both to guarantee the mechanical strength of the cryostat and to limit thermal conduction (the smaller the section of the internal junction element 30, the lower the thermal conduction).

[0080] In the example of realization of the figures 8 à 10 , each internal junction element 30 is formed by a double V-shaped rod, comprising two branches defining a plane. As explained below, this plane can be inclined relative to a transverse plane of the cryostat body.

[0081] In reference to the figures 9A et 9B , showing their longitudinal position, the internal joining elements 30 are for example inclined relative to a transverse plane (in this case, the bases of the Vs are all located in the same first transverse plane while the free ends of the branches of the Vs are located in transverse planes close to this first transverse plane), this inclination occurring alternately in the direction of one or the other of the axial ends of the body 10.

[0082] As shown in the figure 12 , two cold fingers 60 pass through the screens to cool the central enclosure 14. Each cold finger is arranged at a distance from the screens.

[0083] As shown in the figure 12A , a thermally insulating coating 105, for example of the multi-layer type, also called “MLI” (acronym for the English multi-layer insulation ), can be arranged, in the transverse passage 15, against each cold finger 60, thus reinforcing the thermal insulation of the cryostat.

[0084] Alternatively or possibly in combination, as shown in figure 12B , a thermally insulating bellows covering 106, for example made of polymer, can be arranged, around each cold finger 60, in the transverse passage 15 and between the screens 13.

[0085] THE figures 15 à 18 represent an exemplary embodiment in which the cryostat 100 is made up of three single-piece parts: a base 110a, an annular central part 110b and a cover 110c, which assemble to form the body of the cryostat. The single-piece parts each comprise a plurality of insulating partitions 113a, 113b and 113c, and have shapes adapted to the integration of a given spatial component 300. The shapes of the different single-piece parts 110a, 110b and 110c are also complementary so that each partition of a single-piece part is associated with one of the partitions of each of the two other single-piece parts to form a screen.

[0086] More particularly, according to this exemplary embodiment, the body of the cryostat 100 has a generally parallelepiped shape of which the central single-piece part 110b materializes the lateral faces, and of which the base 110a and the cover 110c materialize respectively the lower face and the upper face.

[0087] The central monobloc part 110b comprises a succession of annular partitions 113b arranged at a distance from each other in a coaxial manner around a main axis X (materialized on the figure 15 ). It comprises in particular an interior partition 113b(1) delimiting the enclosure 114 which receives the spatial component 300 operating at cryogenic temperature, intermediate partitions 113b(2), and an exterior partition 113b(3).

[0088] In this example, the intermediate partitions and the inner partition are of similar shape and of increasing dimensions from the inside to the outside. On the other hand, the outer partition 113b(3) moves away in places from the outermost intermediate partition to form housings for receiving various functional members of the cryostat such as electrical connection means.

[0089] The base 110a and the cover 110c comprise flat partitions 113a and 113c arranged at a distance from each other and having decreasing dimensions from the outside of the cryostat towards the inside, giving the base and the cover a pyramidal appearance. This pyramidal appearance, clearly visible in the detail of the figure 16 , allows good accommodation of the cryostat.

[0090] As shown in the figure 18bis , the interior partitions 113b(1), 113c(1) and intermediate partitions 113b(2), 113c(2) of the two single-piece parts are arranged in the vicinity of each other to form a screen closed in a non-tight manner, having their ends at a distance from each other. These two single-piece parts can correspond to the central single-piece part 110b and the cover 110c or to the central single-piece part 110b and the base 110a.

[0091] In this example of embodiment of the cryostat 100 in three single-piece parts, only the base 110a is provided with external bipods 20 (forming external joining elements between the cryostat and a satellite platform), which makes it possible to concentrate the force paths only in said base.

[0092] Like the embodiment described above, the external bipods 20 and the internal joining elements can be made from the same material as the partitions 113a, 113b or 113c with which they are associated, for example from a metallic material having suitable thermal and mechanical properties, preferably titanium.

[0093] Titanium offers a good compromise between mechanical properties (sufficient stiffness and strength) and thermal properties (relatively low thermal conductivity compared to other metals such as aluminum, for example). Titanium is also compatible with 3D printing.

[0094] The use of an additive manufacturing technique, such as laser powder bed fusion technology, is advantageous in that it allows the manufacturing of several elements (partitions, internal joining elements, and external joining elements) in a single monolithic part. In addition, additive manufacturing allows the production of metal parts with fine, complex and intricate shapes, as is the case with monobloc parts (presence of a plurality of internal partitions connected by joining elements) with a precise configuration.

[0095] Other manufacturing techniques may be used, as may materials other than titanium, including materials not compatible with 3D printing, the latter being only an optional, albeit advantageous, manufacturing method of the cryostat according to the invention. Even if additive manufacturing is not used, the design of the cryostat according to the invention remains relatively simple. In any event, the cryostat according to the invention has at least the advantage of compactness and that of being able to accommodate one or more space components operating at cryogenic temperature of various shapes and sizes.

[0096] Depending on the overall geometry of the cryostat, which is first dictated by the shape of the spatial component it is intended to accommodate, and depending on the number of single-piece parts that make up the cryostat, as well as the material(s) chosen, thermal and mechanical computer simulations are performed to determine the number of screens 13, as well as their thicknesses and the thickness of the vacuum blades separating them, making it possible to achieve, without specific coatings or SLI sheets (acronym for "SLI"), Single Layer Insulation ”) nor multi-layer insulation MLI ( Multi Layer Insulation ), thermal and mechanical performances equivalent to or superior to those of cryostats of the prior art.

[0097] Typically, this number has been estimated at seven screens under certain usual operating conditions.

[0098] More generally, the number of screens can be adapted according to the missions, to comply with precise thermal specifications. For example, it may happen that the target temperatures in the interior volume of the cryostat are higher than the values ​​mentioned above (60K and 100K), in which case a smaller number of intermediate screens, for example two or three, would be sufficient to ensure the targeted thermal insulation.

[0099] Another advantage of the invention is that, if one wishes to increase the thermal insulation performance of a cryostat, one can choose to add one or more screens to an already proven initial design, without this significantly impacting the design, qualification and manufacturing process of the cryostat. This is even more true when 3D printing is used. Indeed, it proves less expensive and less restrictive to add an additional intermediate screen to the cryostat, which will be manufactured by 3D printing at the same time as the initial screens, than to insert single-layer SLI or multi-layer MLI insulation sheets between two successive screens of an initial cryostat, for example.

[0100] The installation of a space component, such as a sensor, in the cryostat is illustrated in the figures 11 à 14 .

[0101] Firstly, the spatial component 300 is positioned inside the first single-piece part 10a and fixed to the internal partition 13a(1) using suitable connecting means. An electrical connector 40 and cold fingers 60 are then installed on the body of the cryostat.

[0102] At least one transverse channel is for example made in the successive screens up to the central enclosure for the passage of electrical power supply means and / or means of communication with the spatial component, which channel is closed at the level of the external screen by a thermally insulated connection interface.

[0103] Preferably, bellows 50 are provided around the cold fingers 60 to limit the effects of micro-vibrations generated by the compressor on the fingers and to thermally insulate them. The cold fingers are inserted into passages 15 provided in the body, the passages 15 passing through all of the partitions 13a to the central enclosure 14.

[0104] Other functional organs are installed before closing the cryostat, including: specific electrical wiring 80 between the electrical connection interface 40 and the spatial component 300 operating at cryogenic temperature, which wiring is housed in a channel provided in the various partitions 13a, this channel passing through said partitions to the central enclosure 14. multi-layer thermal braids 71 ​​and 72 made of aluminum (cf. fig.13 ) between the cold fingers 60 and the spatial component operating at cryogenic temperature, which braids are also inserted into the passages 15 in the extension of the cold fingers, a transparent thermal screen 90 (not shown in the figures 11 à 14 but a similar screen is visible on the fig. 17 ) which is placed frontally in front of the focal plane of the spatial component 300. Then, the second single-piece part 10b is assembled to the first in order to close the cryostat, thus isolating the spatial component, such as an optical sensor, as shown in the figure 14 .

[0105] The cryostat can then be mounted on a satellite platform using its external securing elements (bipods) 20.

[0106] THE figures 19 à 21 illustrate a third example of embodiment according to the invention.

[0107] This cryostat 200 comprises a single monobloc part 210a, a first series 210b of independent upper covers 213b and a second series 210c of independent lower covers 213c.

[0108] The single-piece part 210a is, for example, made by 3D printing. The covers are, for example, made by 3D printing or machining, then treated to add a gold plating.

[0109] The single-piece part 210a is similar to the central single-piece part 110b of the exemplary embodiment of the figures 15 à 18 in that it is generally annular and cylindrical with axis X, and in that it comprises a plurality of partitions, including an inner partition 213a(1), which partially delimits a central enclosure 214 intended to receive the spatial component to be maintained at very low temperatures, an outer partition 213a(3) and several - in the example two - intermediate partitions 213a(2). All the partitions are generally cylindrical, coaxial, spaced from each other; they have increasing dimensions going from the inner partition 213a(1) to the outer partition 213a(3).

[0110] The partitions of the single-piece part 210a are made integral with each other by internal joining elements which can be double V-shaped rods as previously described for the example of embodiment of the figures 8 à 10 .

[0111] There figure 21 shows an alternative embodiment for the internal joining elements. In this alternative, the internal joining elements comprise several sets, including a set 230 and a set 231, of single rectilinear rods. The rods 230(1), 230(2) and 230(3) of the same set 230 (same for the set 231) are aligned and extend in a longitudinal plane containing the main axis X of the single-piece structural part 210a, in a direction inclined relative to a transverse plane. In other words, the rods of the same set extend in the same direction, which intersects the main axis X but forms with this axis an angle which is not equal to 90°.

[0112] Furthermore, the directions in which the single rods are aligned form angles with a transverse plane (or with the X axis) which preferably vary from one set to another, so that the connection points between the outer partition 213a(3) and the rod 230(3) associated with said partition are located at heights (along the X axis) which vary from one set of rods to another.

[0113] Alternatively, the straight lines along which the two sets of rods 230 and 231 are arranged have the same angle of inclination relative to the central axis X of the single-piece part.

[0114] As previously explained for the interior V-joint elements, the alignment of the rods in sets, with judiciously chosen angles and / or directions, offers a good compromise between mechanical resistance and thermal resistance.

[0115] In addition to the central monobloc part 210a, the cryostat comprises a first series of upper covers 210b comprising an inner upper cover 213b(1), one or more - in the example two - intermediate upper covers 213b(2), and an outer upper cover 213b(3).

[0116] The cryostat similarly comprises a second series of lower covers 210c, comprising an inner lower cover 213c(1), two intermediate lower covers 213c(2) and an outer lower cover 213c(3).

[0117] The inner covers, respectively upper 213b(1) and lower 213c(1) come in the axial extension of the inner partition 213a(1) of the single-piece part 210a and are fixed to the latter. The inner partition 213a(1) and the two inner covers 213b(1) and 213c(1) thus form an inner screen which delimits a closed enclosure 214 intended to accommodate the spatial component 300 to be cooled.

[0118] The smaller of the lower intermediate covers 213c(2) and the smaller of the upper intermediate covers 213b(2) come in the axial extension of the smaller of the intermediate partitions 213a(2) of the single-piece part 210a and are fixed to said partition to form a first intermediate screen surrounding the inner screen. Similarly, the larger of the lower intermediate covers 213c(2) and the larger of the upper intermediate covers 213b(2) come in the axial extension of the larger of the intermediate partitions 213a(2) of the single-piece part 210a and are fixed to said partition to form a second intermediate screen surrounding the first intermediate screen.

[0119] Finally, the outer covers, respectively upper 213b(3) and lower 213c(3), come in the axial extension of the outer partition 213a(3) of the single-piece part 210a and are fixed to this partition to form an outer screen.

[0120] In other words, unlike the aforementioned partitions, the covers are not linked together and therefore do not form structural monobloc parts capable of supporting and transmitting forces from one screen to another.

[0121] Preferably, the upper covers 213b(1) to 213b(3) and lower covers 213c(1) to 213c(3) are fully covered with a gold coating. This gold coating makes it possible to modulate the emissivity and absorptivity properties governing radiative transfer and thus to optimize the radiative environment. This gold plating of the cover is for example obtained by electrolytic deposition on a part obtained by machining or 3D printing.

[0122] The cryostat 200 further comprises external securing elements 20 in the form of bipods for securing it to a satellite platform. All the external bipods 20 of the cryostat 200 are fixed to the single-piece part 210a so that all the forces to which the space component operating at cryogenic temperature is subjected pass through this single-piece part, the rigidity of which is guaranteed by the internal junction elements between screens.

[0123] On the other hand, the connection interface 240 for the power supply and control of the instrument, as well as the recovery of the measurement data captured by the instrument, can be carried by an external cover, for example the upper external cover 213b(3).

[0124] Of course, the cryostat also includes a device for cooling the enclosure 214, for example at least one insulated cold finger 260 which passes through the screens and can be extended by a thermal braid to reach and cool the central enclosure 214.

[0125] The cold finger may be insulated from the screens by a multi-layer insulation (MLI) sleeve, such as sleeve 105 shown in figure 12A , the passage provided in the screens to receive the insulated cold finger preferably being large enough so that the MLI sleeve is not in contact with the partitions 213a. Alternatively or in combination, the cold finger may be insulated from the screens by a bellows polymer film, such as film 106 of the figure 12B , coming into contact with the partitions 213a.

[0126] The cryostat 200 further includes a transparent thermal screen 290 which fills and thermally insulates an opening 221 (see Fig. 19 ) arranged in the body of the cryostat opposite the space component operating at cryogenic temperature, such as an optical detector.

[0127] The cryostat according to the invention is not limited to the examples illustrated. Thus, for example, the cryostat could comprise two single-piece parts and a single series of independent covers, for example a central single-piece part, similar to the annular central part 210a of the figure 19 , a lower one-piece part forming a base such as the base 10a of the fig. 15 à 18 , and a series of upper independent covers such as covers 213b(1) to 213b(3) of the figure 19 In this case, the external securing elements can either all be fixed to the central monobloc part, or all fixed to the lower monobloc part (base), or distributed over the two monobloc parts.

[0128] Alternatively, the cryostat could comprise a single monobloc part and a single series of independent covers, namely for example: a single-piece part, comprising a cylindrical section corresponding to a central annular part of the body and a conical or flat section corresponding to a lower part (or base) of the body, and a series of upper covers.

[0129] Other combinations are of course possible.

[0130] In the various combinations proposed above, the term "monobloc" in the expression "monobloc part" implies that this part is in the form of a single block such as for example a monolithic block obtained for example by 3D printing.

[0131] A single-piece part is, for example, self-supporting and sufficiently rigid to absorb, in operation, all the forces undergone by the cryostat and the component it contains. Because it perfectly meets the requirements at very low temperatures and because it has improved mechanical behavior, the mechanical-thermal structure of the cryostat 100 or 200 according to the invention is particularly suitable for missions carrying ultra-sensitive instrumentation, in particular for infrared detection, which must operate at extremely low temperatures to draw up precise maps of tiny temperature fluctuations, sometimes of the order of a hundred thousandth of a degree. Such instrumentation may include optical surfaces (lenses, mirrors, etc.), infrared sensors, bolometers, etc.Of course, this is not limiting to the applications of the cryostat of the invention, which can cooperate with other types of instruments or components operating at less extreme temperatures. The use of additive manufacturing technology makes it possible to manufacture this judicious design while offering a competitive cost and manufacturing time.

Claims

1. A cryostat (100; 200) for at least one space component (300) operating at cryogenic temperature, the cryostat comprising: - a central, closed and cooled enclosure (14; 114; 214), configured to receive the space component, - successive metal shields (13), spaced apart from one another, including an internal shield, an external shield and one or more intermediate shield(s), the internal shield being configured to support the space component (300) and delimiting the central enclosure (14; 114; 214) to receive said space component, the intermediate shield(s) and the external shield being arranged around one another so that each delimits a closed volume receiving the preceding shield of smaller size, - a cooling device for cooling the central enclosure at cryogenic temperature, - external securing elements (20) fastened to the external shield, for securing the cryostat (100; 200) to a satellite platform, - internal inter-shield joining elements (30; 230, 230(1), 230(2), 230(3), 231), which hold said shields (13) spaced apart from one another, the cryostat being characterized in that it comprises at least one integral portion (10a; 210a) comprising a series of partitions (13a; 213a) including an internal partition (13a(1); 213a(1)), an external partition (13a(3); 213a(3)) and one or more intermediate partition(s) (13a(2); 213a(2)), respectively corresponding to a portion of the internal shield, a portion of the external shield and a portion of the one or more intermediate shield(s), said partitions being spaced apart from one another and held together by at least one portion of the internal inter-shield joining elements (30; 230, 230(1), 230(2), 230(3), 231).

2. The cryostat according to claim 1, wherein the cooling device comprises one or more cold finger(s) (60; 260) for cooling the central enclosure and, for each of the cold fingers, a transverse passage (15) passing through the successive metal shields (13) up to the central enclosure (14; 114; 214) for receiving said cold finger, the cold finger(s) not being in contact with the shields.

3. The cryostat according to claim 1 or 2, wherein the internal inter-shield joining elements (30; 230, 230(1), 230(2), 230(3), 231) are arranged between the successive shields and configured to confer mechanical strength on their own between the external shield and the internal shield, said internal joining elements being configured to withstand determined forces induced at least by a mass of the space component (300) and masses of the shields (13).

4. The cryostat according to one of claims 1 to 3, wherein the internal inter-shield joining elements comprise V-shaped double rods (30) between the successive shields, the Vs being angularly distributed around a main axis (X) or a central point of the cryostat according to at least three radial directions.

5. The cryostat according to one of claims 1 to 4, wherein the internal inter-shield joining elements comprise several sets (230, 231) of single rods (230(1), 230(2), 230(3)), the single rods of a same set being aligned according to a straight line passing through the shields, the straight lines of two distinct sets (230, 231) being non-parallel and non-coplanar with one another.

6. The cryostat according to one of claims 1 to 5, wherein the internal inter-shield joining elements (30; 230(1), 230(2), 230(3), 231) are made integral with at least a portion of the shields (13).

7. The cryostat according to one of claims 1 to 6, wherein said integral portion is made by additive manufacturing.

8. The cryostat according to claim 1 to 7, characterized in that: - the cryostat comprises a plurality of integral portions (10a, 10b; 110a, 110b, 110c) each having an internal partition (13a(1), 13b(1); 113a(1), 113b(1), 113c(1)), an external partition (13a(3), 13b(3); 113a(3), 113b(3)) 113c(3)) and one or more intermediate partition(s) (13a(2), 13b(2); 113a(2), 113b(2)) 113c(2)), the partitions of two distinct integral portions among said integral portions corresponding to two distinct portions of the shields, - the intermediate (13a(2), 13b(2); 113b(2), 113c(2); 113a(2), 113b(2)) or internal (13a(1), 13b(1); 113b(1), 113c(1); 113a(1), 113b(1)) partitions of two distinct and adjacent integral portions (10a, 10b; 110b, 110c; 110a, 110b) among the plurality of integral portions which are in line with one another being non-contiguous, - the external partitions (13a(3), 13b(3); 113b(3), 113c(3); 113a(3), 113b(3)) of two distinct and adjacent integral portions among the plurality of integral portions which are in line with one another being contiguous and fastened to one another.

9. The cryostat according to claim 8, wherein the intermediate (13a(2), 13b(2)) or internal (13a(1), 13b(1)) partitions which are in line with one another have facing ends, at least one of these facing ends having a recess so as to form a baffle (130c) with the other facing end.

10. The cryostat according to one of claims 1 to 9, wherein the external securing elements (20) are either all fastened on the external partition of only one of the integral portions, or distributed over the external partitions of several ones of the integral portions.

11. The cryostat according to one of claims 1 to 10, characterized in that at least one (110b; 210a) of said integral portions is an annular structural portion wherein each internal (113b(1); 213a(1)), intermediate (113b(2); 213a(2)) and external (113b(3); 213a(3)) partition is annular.

12. The cryostat according to one of claims 1 to 11, characterized in that each of the shields of the cryostat is entirely formed by the assembly of the partitions of the integral portions (10a, 10b; 110a, 110b, 110c).

13. The cryostat according to claim 11, wherein: - the cryostat comprises at least one series (210b, 210c) of independent cowls including, for each series, an internal cowl (213b(1), 213c(1)), an external cowl (213b(3), 213c(3)) and one or more intermediate cowl(s) (213b(2), 213c(2)), each series of cowls respectively corresponding to another portion of the shields, the cowls of the same series being arranged inside one another, at a distance from one another, with no internal joining elements, - each of said cowls (213b(1), 213b(2), 213b(3), 213c(1), 213c(2), 213c(3)) lying in line with and being fastened to one of the partitions (213a(1), 213a(2), 213a(3)) of said annular structural portion (210a), each of the shields of the cryostat thereby being entirely formed by at least one of the partitions of the annular structural portion and by one of the cowls of each series.

14. The cryostat according to claim 13, wherein at least one portion of each of the cowls (213b(1), 213b(2), 213b(3), 213c(1), 213c(2), 213c(3)) is provided with a golden coating.

15. The cryostat according to one of claims 2 to 14, wherein each of the cold fingers (60; 260) is thermally insulated from the shields, a heat-insulating coating being arranged against at least one of the cold fingers (60) in the transverse passage (15) of said cold finger, and / or a bellow-fashioned heat-insulating coating being arranged around at least one of the cold fingers (60), in the transverse passage (15) of said cold finger and between the shields (13).

16. A spacecraft characterized in that it comprises a space component (300) which operates at cryogenic temperature and is arranged in a cryostat according to one of claims 1 to 15, the cryostat being fastened on a platform of the spacecraft.