FR2784962A1 - SOLAR GENERATOR FOR SATELLITES - Google Patents

Abstract

Solar generator for satellite having a support structure (1) of sandwich construction with a lower skin and an upper skin (3a, 3b) between which there is a honeycomb core (2). Resonators are integrated or coupled to the support structure (1) to reduce the sound pressure. The cavities (28) of the honeycomb core (2) form, with the perforated sheet (4), Helmholz resonators to reduce the charges resulting from the sound pressure at launch of the rocket. One can also use spring elements as resonators; these have for example a tongue shape.

Description

The present invention relates to a generator

  space for satellites with a large number of solar cells

  laires to a support structure with a nested core

  of bees between an upper skin and a lower skin.

  The satellites are supplied with energy by solar cells fixed on very resistant carbon fiber sandwich structures. Such structures are exposed to considerable loads especially

  at the time of launch; these charges result from the vibra-

  tions. These are accelerations up to 30 g. The vibration frequency range is of the order of at least

Hz to 100 Hz.

  Document US 4,394,529 describes a so-

  area with a large number of solar cells on a sandwich structure. The sandwich structure is formed of aluminum honeycomb cores and between the layers

  or the strata, there is kevlar. To increase the resistance

  tance, the rear side of the support structure has

  an arrangement of rods forming stiffening elements

due to vibrations.

  In addition to the vibrations mentioned above, there is also, as an additional load, the sound pressure, created by the noise of the engines of transport rockets at launch, under the aerodynamic covering of the tip of the rocket. The main stress of the sound pressure is essentially in a frequency range from about 150 Hz to about 500 Hz. This constitutes a particular risk for light structures or components sandwiched with thin skins. The stresses generated by the sound pressure increase strongly with the size of the panels, this is why, one can realize large solar generators only with a significant weight. In addition, the deformations of the structure caused by the sound lead

  damage to sensitive solar cells.

  The present invention aims to develop a solar generator for spacecraft or satellites

  in which the constraints generated or the risks of dom-

  1FTFTIULUJT 1fl mages of rooms under the effect of sound pressure are

  while keeping the weight low.

  To this end, the invention relates to a solar generator of the type defined above, characterized in that the resonators are integrated in the support structure and / or

are coupled to it.

  The solar generator according to the invention comprises

  a large number of solar cells and a sup-

  habit having a honeycomb core between a superior skin

  lower and a lower skin as well as integrated resonators and / or coupled to the support structure. Thanks to the resonators integrated or coupled to the structure, the sound load is reduced and thus the risk to which the

  rooms. The stress on the structure is reduced. In by-

  particular, we can greatly reduce the constraints

  sonic in the frequency range

  between 100 Hz and 1000 Hz by resonators.

  Preferably, the resonators are formed by a sheet and cavities preferably provided in the upper skin and / or the lower skin of the honeycombs. The cooperation between the cavities and the sheet gives a structure of Helmholz resonators which reduce

  considerably load by sound.

  The sheet advantageously has holes and

  can for example be perforated, microperforated or be

  se in the form of a net. This gives a particular resonator-

  effective and allows very simple and inexpensive manufacturing. The size of the holes distributed statistically

  in the sheet first allows a bandwidth of fre-

  particularly high for resonators of

  Helmholz to reduce the load by sound to low frequencies

very different quences.

  Advantageously, the sheet is located in an area with a very thin wall of the support structure relative to the other areas, and which is particularly exposed to sound. In thin-walled areas, the leaf (s) are particularly effective. The size of the holes in the sheet and that of the cavities of the nest structure II E fTI1.s1 Ifl of bees or its geometry can be tuned so that

  the resonators have a frequency range between-

  be 100 Hz and 1000 Hz and preferably between 150 Hz and

500 Hz.

  The resonators can also be spring elements, distinct for example tongue-shaped springs preferably provided on at least one of the skins. Such discrete resonators can be provided in

  plus the Helmholz resonators discussed above. The cons-

  truction of the discrete resonators can be variable; they can have a low or wide frequency bandwidth. These discrete resonators are preferably provided in a reinforced range on the rear side of the structure of

  support, because at this level, they are particularly effective

these.

  The skin is formed for example of a network of fi

  bres advantageously having a mesh size less than

  the inner section of the honeycomb cavities.

  The present invention will be described below using a preferred embodiment shown schematically in the accompanying drawings in which: - Figure 1 is a partially exploded view, from below, of a support structure of a solar generator according to the invention, FIG. 2 is a top view of the solar generator comprising resonators integrated in the support structure,

  - Figure 3 shows another support structure to cons-

  sandwich construction with elements inducing ef-

  strong, - Figure 4 shows the relationship between sound pressure and frequency at launch of a rocket,

  - Figure 5 shows the behavior of the support structure

  port under the effect of the load by sound as a function of the frequency produced, and - Figure 6 is a partial section of a solar generator with resonators according to another embodiment of the invention. Figure 1 shows a support structure 1 of the solar generator according to the invention in a bottom view

  partially exploded. A honeycomb core 2 in aluminum

  minimum is provided between a lower skin 3a and a su-

  pterior 3b. The components are bonded by an adhesive 11 shown diagrammatically and they form a structure in

  sandwich. The lower skin 3a carries a cover sheet

  truly flexible 4 which is perforated or microperforated according to a preferred embodiment. The perforation is not shown in FIG. 1. The cells or honeycombs 21 of the nucleus 2 form standing hollow bodies with cavities 28 reaching up to the level of the skins 3a, 3b. In combination with the cavities 28 in the honeycomb structure 2, the sheet 4 forms a large number of separate resonators working according to the Helmholz principle. This results in very high sound absorption of the support structure 1. On the upper side of the support structure 1 which does not appear in FIG. 1, there are solar cells

  to make the solar generator according to the invention.

  Besides aluminum, it is also possible to use other materials such as, for example, polyamide-paper, aramid fibers, plastics reinforced with glass fibers or carbon fibers for the nuclei of cells or

  honeycombs 2. The skins 3a, 3b are in particular fi-

  carbon fiber with epoxy resin and a structure

  ticular. In the preferred embodiment, the

  sheet 4 is a perforated sheet of Kapton. In a general way

  neral, materials or fabrics with holes or passages are particularly suitable allowing air to oscillate in the cavities of the nest structure

bees 1.

  Figure 2 is a perspective view of the general

  solar, from above. The cells 5 are provided on the upper side of the support structure 1. The composite sandwich structure based on glass fibers with the core in

  honeycombs 2, the lower skin 3a and the upper skin

  superior 3b giving a very high resistance or rigidity despite a light construction. Beside the honeycombs 21

  preferably used and having a hexagonal section

  gonale called here honeycomb structure, we can also

  Also use honeycombs 21 having a different geometry. The solar cells 5 are provided on an electrical insulating wire and are connected by this to the structure.

  support structure 1 or upper skin 3b.

  FIG. 3 schematically shows another embodiment of the invention with blocks 7 of fibers

  carbon bonded in cores 2 for induction of charges.

  The skins 3a, 3b are reinforced in these places by elements

  additional laminate elements or lining elements 8. To connect the different components together, there are layers of adhesive 9. The sheet 4 is provided with holes at the level of the honeycomb core 2 where it is perforated and it forms with the cavities of the honeycomb core 2 and

  skin 3a, a multiplicity of Helmholz resonators.

  The upper skin 3b which carries the so-

  laires 8 is formed here of a continuous closed layer composed

  fiber site while the lower skin 3a is shaped

of net or has holes.

  Figure 4 shows a diagram giving the pres-

  phonic sion as a function of frequency. It appears that the

  sound pressure for example at the launch of the rocket

  teuse has a maximum in a frequency range com-

  taken between 150 Hz and around 500 Hz. In this range, the stresses of the support structure generated by the

  sound pressure are the most important.

  The behavior of the structure under the effect of the noise load is shown in Figure 5. In this case, the maximum is in a range between 102 and

  103 Hz. In this frequency range, we find the os-

  strongest cillations of the structure under the effect of the

sound load.

  To increase the width of the frequency bands

  resonators, according to another embodiment not shown

  presented here, the sheet 4 is provided with holes of different dimensions. In particular, prefabricated sheets with holes of statistical distribution dimensions make it possible to obtain a larger frequency bandwidth

  with simpler and less expensive manufacturing. For rea

  read the resonators which must be particularly effective

  caces in given frequency ranges, the geometry of the honeycombs or the size of the cavities inside the honeycomb cores 2 is defined as a function of the

size of the holes in the sheet 4.

  Figure 6 shows another embodiment of a solar generator according to the invention. In this case, the

  resonators are tongues 10 in the form of pre-

  views on the lower skin 3a or the side of the support structure 1 facing the solar cells 5. The oscillation behavior of the resonators is defined by the springs and the geometry of the tongues 10. Depending on the particular requirements, it is possible to produce resonators with different frequencies. In this case too, the structures

  21 in the shape of honeycombs give cavities 28 perpen-

  dicular to the skins 3a, 3b. Such discrete resonators are particularly advantageous in the reinforced range of the support structure 1, on the rear side of the generator

  solar. These resonators can be provided in addition to the res-

  Helmholz sounders, integrated, described above or even

  independently of these on the support structure 1.

  The considerable noise load generated by engine noise is effectively reduced by integration

  according to the invention resonators in the structure of sup-

  port 1 of the solar generator or by their coupling to the struc-

support structure 1.

  By applying sheet 4 of particular shape,

  the honeycomb core 2 forms a set of reson-

  Helmholz teachers. In this particular realization of

  resonators, no additional parts are required which

  could significantly increase the weight of the generator

  laire. Sheets 4 are particularly effective in the thin-walled areas of the exposed support structure

at the risk of noise.

  The present invention effectively reduces

  noise constraints especially in a range

  frequency between 100 Hz and 1000 Hz.

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Claims (10)

R E V E N D I C A T I ON S   1) Solar generator for satellites comprising a   appears to be solar cells (5) and a support structure   (1) having a honeycomb core (2) between a skin   and a top skin (3a, 3b), characterized in that the resonators are integrated in the support structure   (1) and / or are coupled thereto.   2) Solar generator according to claim 1, characterized in that the resonators are Helmholz resonators formed in   the honeycomb core by a sheet (4) and cavities tees (28).   3) Solar generator according to claim 2, characterized in that   the sheet (4) has holes and / or is perforated, mid   croperforated or has a mesh structure.   4) Solar generator according to one of claims 2 or 3, characterized in that   the sheet (4) has holes of sizes distributed sta- tistically.    ) Solar generator according to one of claims 2 to 4,   characterized in that the sheet (4) is provided in an area of the support structure (1) having a relatively thin wall thickness   compared to that of other areas.   6) Solar generator according to any one of the claims   above, characterized in that the resonators have a frequency range between Hz and 1000 Hz, preferably between 150 Hz and 500 Hz. it ivmiT [i 7m î _   7) Solar generator according to any one of the claims   tions 3 to 6, characterized in that the size of the holes in the sheet (4) and that of the cavities (28) are defined according to the frequency range of the sound pressure.   8) Solar generator according to any one of the claims.   above, characterized in that   the resonators include spring elements (10),   trimmed, provided on the upper and / or lower skin.   9) Solar generator according to any one of the claims   above, characterized in that   the resonators are tongues (10) in the form of res- spells.   10) Solar generator according to any one of the claims   tions 8 and 9, characterized in that the resonators are provided in a reinforced range on the side   back of the support structure (1).   11) Solar generator according to any one of the claims   above, characterized in that the lower and / or upper skin (3a, 3b) is formed of   composite fiber net with a smaller mesh size   smaller than the internal section of the cavities (28) in the core honeycomb (2). il 1TT1I BJ IR _â U7