WO2011006506A1

WO2011006506A1 - Foldable frame supporting electromagnetic radiation collectors

Info

Publication number: WO2011006506A1
Application number: PCT/DK2010/050186
Authority: WO
Inventors: Anders Schmidt Kristensen; Lars Damkilde
Original assignee: Aalborg Universitet
Priority date: 2009-07-15
Filing date: 2010-07-14
Publication date: 2011-01-20

Abstract

The present invention relates to flexible frames supporting electromagnetic radiation collectors, such as antennas, antenna reflectors, deflectors or solar collectors, for celestial or terrestrial applications, which can be folded to be stored and/or transported. The method for stowing deforms the flexible frame into a stressed configuration. Once released from the stressed configuration the flexible frame restores its initial configuration without any external intervention.

Description

FOLDABLE FRAME SUPPORTING ELECTROMAGNETIC RADIATION COLLECTORS

FIELD OF THE INVENTION

The present invention relates to flexible frames supporting electromagnetic radiation collectors which can be folded to be stored and/or transported.

BACKGROUND OF THE INVENTION

Collectors for electromagnetic radiation (EMr) generally encounter problems when transportation is needed due to their large dimensions. For both terrestrial and celestial application transport of large EMr collectors is difficult and can easily lead to damage of the collectors due to incorrect stowing.

EMr collectors, such as solar panels and antenna systems, where efficiency of collection is related to surface area, are normally provided in large structures with the disadvantage of not being easily movable.

For terrestrial application large solar panels or antenna systems are not easily transported due to there sizes. Even when provided in small sizes, solar panels or antenna systems are cumbersome and transportation by a person may be hindered.

For celestial application, large solar panels or antenna systems are generally vital for the operation of artificial satellites. To be launched and put in orbit, these satellites are subjected to harsh transport condition and generally disposed in a rocket or space ship with limited inner volume. Therefore transportation also for celestial application is limited by the size, encumbrance and dimensions of these systems.

In general for celestial application antenna reflectors are designed to facilitate reflector shape modification for stowage. One often-used approach is to use a segmented reflector with a cantilever rib frame which unfolds on deployment as an umbrella unfolds.

To facilitate transportation of these structures several stowing solutions have been found. US 2008/0223431 discloses a foldable solar panel comprising multiple cell assemblies and multiple flexible seams, wherein each folding cell assembly has two symmetric folding cell assembly halves and a flexible secondary seam.

US 4,371,134 describes an artificial satellite arrangement with foldable solar generators and antennas. These generators comprises an assembly of panels bearing solar cells articulated on one another in succession so as to occupy either a folded position for launching for which said panels are folded in a zigzag form on one another, or an unfolded position for operation for which said panels are at least substantially in line with one another. Unfolding of the generator is controlled by a drive mechanism receiving orders from the satellite.

US 4,555,585 discloses a foldable solar cell panel apparatus which has at least two panel portions which are connected together at a foldable edge to form at least one foldable pair. The panel needs the presence of folding and unfolding system means for folding and unfolding the solar cell panel apparatus.

US 5,857,648 discloses a precision deployable boom assembly for terrestrial and celestial applications which comprises an extendable and retractable boom.

These systems have the disadvantage of being costly, complicated manufacture systems and of requiring delicate folding procedure for proper stowage.

Moreover, the systems described in the prior art, require specific unfolding manoeuvre which generally require active unfolding device assistance for a correct deployment. The need of active unfolding devices is a main disadvantage of these systems as an active intervention to produce appropriate deployment is rather difficult specifically in celestial application. Deployments which are assisted by booms or articulate unfolding devices are also particularly hard to control for systems which are in motion in 1 or 2 dimensions, e.g. satellites. For these systems in motion, conservation of the correct momentum is crucial to avoid undesired deviation from the desired orbit. Reproduction in space of the exact deployment movement tested on earth is vital to avoid variation in the system momentum which can lead to damage of the solar collectors or antenna systems or in the worst case loss of satellites caused by dramatic variations their orbit. US 5,574,472 discloses a method for stowing a unitary flexible antenna reflector in a confining envelope. The reflector, once deformed for stowing into a U-shaped configuration, is maintained in a deformed state by attaching a restraining element between the diametrically opposed positions on the edge of the reflector. The main disadvantage of the flexible antenna reflector disclosed by US 5,574,472 is that the deformation into a U-shaped configuration of the reflector does not efficiently reduce the encumbrance of the reflector as it simply increases the reflector curvature. For example, this method of stowing an antenna reflector was used on the MSAT-I satellite, launched on April 20, 1996, where two folded spring-back antenna having 6.8 m by 5.25m elliptical shape where stowed. In the stowed configuration the two antennas were rolled together into a 4.9 m high truncated cone on top of the spacecraft, therefore by only partially reducing the reflector dimension.

In accordance there is a need for a method for stowing EMr collectors which can be efficiently folded so as to reduce their size and which can be unfolded to their initial configuration without the intervention of an active unfolding device.

SUMMARY OF THE INVENTION

Accordingly, the invention preferably seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination by providing a method for stowing a flexible frame which efficiently reduces its size by deforming the electromagnetic radiation collectors supported.

In particular, it may be seen as an object of the present invention to provide a method for stowing a flexible frame supporting EMr collectors that solves the above mentioned problems of the prior art by deforming the flexible frame into a stressed configuration to reduce its size. This stressed configuration is obtained by twisting and folding the flexible frame following the method described by embodiments of the invention.

It may be seen as a further object of the present invention to provide a method for stowing a flexible frame supporting EMr collectors for celestial and terrestrial application, which solves the above mentioned problems of the prior art or provide an alternative to the prior art.

It may also be seen as an object of the present invention to provide a method for stowing a flexible frame supporting EMr collectors for celestial application, such as antennas, which solves the above mentioned problems of the prior art by twisting and folding the flexible substrate so as to stored strain energy. The release of this stored strain energy in space provides rapid deployment of the frame without the need of external intervention.

The above described objects and several other objects are intended to be obtained in a first aspect of the invention by providing a method for stowing a flexible frame supporting a collector of electromagnetic radiations, the method comprising : i) deforming by twisting and folding said flexible frame into a stressed configuration to reduce its size, and ii) maintaining said flexible frame in said stressed configuration.

An electro-magnetic radiation collector is a device capable of collecting electromagnetic radiation characterized by specific wavelengths, energies and

frequencies, within the range of the electromagnetic (EM) spectrum. For example antennas are EMr collectors which are able to collect for example radio

frequencies, e.g. 1000 MHZ to 50 MHZ. Another example of an EMr collector is a solar collector or a light collector.

Celestial applications are herein defined as application which occurs in planets atmosphere, in controlled or uncontrolled airspace, in the outer space or on objects in the outer space.

Terrestrial applications are herein defined as applications which take place on the surface of the planet earth.

Reducing size of the flexible frame is herein defined as reducing the space occupied by it, by reducing its dimensions, high, length, width, volume, cross section or area.

The method allows for storing in the stressed configuration of the energy needed for deployment. In celestial application this energy is introduced and stored in gravity conditions and released in non-gravity conditions upon deployment of the flexible frame.

The invention is particularly, but not exclusively, advantageous for reducing the size of transportable EMr collectors. The specific twisted and folded position described by the invention avoids problem in unfolding when compared to other method wherein unfolding may cause entanglement, e.g. no wires are present. A further advantage of the invention is that once installed the collectors can be easily, for example in terrestrial application, re-stowed during sudden typhoon, rain, snow, hail or other adverse atmospherical condition, which may produce severe damage to the collectors.

The above described object and several other objects are intended to be obtained in a second aspect of the invention by providing a flexible frame supporting a collector of electromagnetic radiations, characterized in that, the flexible frame is twistable into at least two loops and the at least two loops are foldable into an overlapping configuration to provide a compact configuration.

In the following, a number of preferred and/or optional features, elements, examples and implementations will be summarized. Features or elements described in relation to one embodiment or aspect may be combined with or applied to the other embodiments or aspects where applicable. As an example, a feature or element described in relation to the flexible frame may be implemented as a step in the method where appropriate. Also, explanations of underlying mechanisms of the invention as realized by the inventors are presented for explanatory purposes, and should not be used in ex post facto analysis for deducing the invention.

In some embodiments deforming the flexible frame according to the first aspect of the invention, comprises: i) twisting the flexible frame to obtain at least two loops, ii) folding the at least two loops into an overlapping configuration.

The deformation by twisting turns the flexible frame into a coil configuration, to which it follows folding of the twisted frame into a closed coil configuration having at least two intermeshing convolution. Closed is defined as having neither beginning nor end. The closed coil configuration is induced by the closed configuration of the frame.

In some other embodiments deforming of the flexible frame further comprises compressing the at least two loops into a compact configuration.

Compressing may comprise pressing, bending, folding or twisting so as to obtain a compact configuration.

Compact configuration is herein defined as a configuration where the loops in the overlapping configuration are closely and firmly united, e.g. by pressing the loops together. Compacting the twisted and folded frame is not necessary but

advantageous as it substantially reduces the encumbrance of the frame.

In some embodiments the step of maintaining said flexible frame in the stressed configuration includes the use of means for holding the stressed configuration. Means for holding comprises devices with the function of holding tight and securing the stressed configuration, i.e. the overlapping configuration, e.g. a coil configuration, so as to avoid undesired opening during the transport.

These devices may be clamps, clips, couplers, tube locks which can be opened by either mechanical intervention, or in particular for celestial application by the use of pyrotechnic devices, such as small explosion charges, or by electrical resistance that can be burned.

Means for holding may also include a pouch with the function of securing the stressed configuration during transport. The opening of this pouch allows for self unfolding of the flexible frame with no need of external intervention, as once removed the holding means, the frame return into it initial configuration without needing active or external deployment means.

In some other embodiments, the flexible frame is connected to a carrier structure.

Carrier structures are structures carrying the flexible frame, which is connected to them. Examples of these carrier structures, hereafter simply referred as structure, are, for celestial applications, satellites, spacecrafts, and spacestations. In this case the EMr collectors, e.g. solar energy converters, supported on the flexible frames are connected to the structure to provide energy. For terrestrial

applications these structures can be any structure which can benefit from a reduction of sizes of this flexible frame supporting EMr collectors, for example to obtain an easier transportable structure. For example, where personal

transportation is required, e.g. tracking expeditions, a foldable frame supporting a solar collector, which can be easily folded for transport and unfolded before use, may provide electricity to sources of light or devices such as mobile phones, computers or other electronic devices.

In some embodiments the method, according to the first aspect of the invention further comprises releasing the flexible frame from the stressed configuration. Once released the flexible frame self restores its initial configuration without any external intervention. The method according to the first aspect of the invention describes a way of deforming the frame, by twisting and folding, which allows for storing of the energy necessary for the unfolding so that virtually no external energy, e.g. by external intervention, is needed during the unfolding process. The simple removal of the holding means allows for self restoring of the initial configuration of the flexible frame. Once released the flexible frame restores its initial configuration because it was folded into an unstable configuration, i.e. the stressed

configuration, and the frame is made with materials with properties which allows for storage of the energy introduced through the folding.

In terrestrial applications unfolding without any external intervention may be advantageous as the unfolding process may occur at a certain distance from the user. For example a pouch holding the frame supporting a solar cell may be thrown at a distance from the user and than unfold into its operative state without user intervention.

External intervention is herein defined as an intervention, e.g. an act performed, to the frame by bodies which are not the flexible frame in itself. For example, a deployment performed by an astronaut on the already released flexible frame can be defined as an external intervention. Another example of external intervention is the deployment of the flexible frame into its initial configuration after its release by a boom. The absence of an external intervention is particularly advantageous in celestial application, as generally restoring of the initial operative configuration of a satellite, to which the flexible frame supporting EM collectors is connected, may require deployment means.

This is further advantageous as the exact unfolding process, which occurs in space, can be reproduced in the terrestrial test allowing for optimization of the carrier structure functionality before the structure is launched and put in orbit. This is particularly advantageous as it may reduce expensive corrections and reparations to the functionality of the satellite which otherwise need to be performed when the structure is in orbit.

In some embodiments according to the first aspect of the invention, the flexible frame released from the stressed configuration restores its initial configuration without substantial modification of the structure momentum. This is particularly advantageous in celestial application. Generally in space structures connected to the flexible frames are in motion in 1 or 2 dimensions, having a specific momentum which needs to be preserved in order to avoid undesired deviation from their desired orbit. In order to preserve the structure momentum, the deployment of the flexible frame can be tested on earth so that the exact deployment movement can be reproduced in space allowing for preservation of the desired system, i.e. carrier structure and frame connected, momentum. Minimal or not significative modifications to the structure momentum induced by the deployment of the flexible frame can be taken in consideration during the test on earth and corrective solutions can be found before the structure is sent in orbit.

In particular, for celestial application it can be of particular advantage that the opening of the device occurs avoiding introduction of external energy so as to keep the all system into an energy neutral state. In the case in which the frame is connected to a structure, e.g. a satellite, keeping the system, i.e. the structure connected to the frame, into an energy neutral state will avoid undesired acceleration of the system during the deployment of the flexible frame.

Vibrations due to the unfolding of the flexible frame may be damped by using damping systems.

The speed of unfolding of the flexible frame can also be controlled by constructing the frame using appropriate structural materials. Some structural materials or combination of materials and composites can be devised to exhibit high structural damping. This is advantageous in order to control the speed of unfolding so as to avoid an excessive speed.

In some preferred embodiments according to the first aspect of the invention the collector of electromagnetic radiations is a solar collector.

In some other embodiments according to the first aspect of the invention the collector of electromagnetic radiations is a light collector.

A solar collector is able to collect the EM radiation emitted by the sun which largely lies in the visible and near infrared area of the EM spectrum. Similarly a light collector is able to collect light, e.g. from the sun or from other sources of natural or artificial light, which includes radiations in the UV, visible and near LR. regions of the EM spectrum. A solar or light collector can be for example a material having photovoltaic properties, such as silicon, which is sensible to radiation emitted in a specific region of the EM spectrum, e.g. in the Uv/visible/N.I.R. regions which identify the solar emission.

The material having photovoltaic properties may be in the form of thin or thick films of material or blends, e.g. materials having photovoltaic properties and nanoparticles, deposited on substrate. Example of these films may be, inorganic or organic semiconductor materials, for example amorphous Si, CIGS films, CdTe thin films, polymeric or hybrids, i.e. polymeric/inorganic films, polymer blends with bulk hetero junction systems.

Collector substrates may be semi-rigid substrate like thin metal, or composite, e.g. metal/polymer, plates, thin films or foils. In other embodiments substrate may be textile materials, including plastified or metalled layers, so as to adjust and tune stiffness, rigidity and elasticity properties of the substrate.

In some other embodiments according to the first aspect of the invention the collector of electromagnetic radiations is a part of a solar energy converter.

In other embodiments according to the first aspect of the invention the collector of electromagnetic radiations is a part of a light energy converter.

A solar or light collector may also include a device for converting the collected radiation into a different form of energy. In this specific embodiment the solar collector may be referred as to solar energy converter, for example a solar cell, which converts solar or light radiation into electricity.

A solar energy converter may comprise a single solar cell or panel or a module composed by more than one cell or panel assembled together so as to synergically collect solar radiation.

Solar energy converters and collectors may have different structures, for example single solar cell, panels or modules may be connected in series or parallel depending on the desired output, i.e. optimized voltage or current. Strategic location of the solar panels or modules in the solar energy converters may also be used to obtain maximum efficiency of conversion. For example panels may be facing opposite direction in order to average light collection independently from the position of the source of light. Cells, panels or modules maybe also arranged into the collector in a way to facilitate the twisting and folding process of frame. For example, cells may be provided so as to leave a central opening in the structure which may facilitate the deformation by twisting and folding.

Though the description given here of solar energy converters have been limited to some embodiments, examples of several kinds of solar energy converters are well known to those skilled in the art. Thereby the use of other well know solar energy converters by the person skilled may be anticipated and remain within the scope of the invention.

In some embodiments the flexible frame according to the second aspect of the invention further comprises means for holding the overlapping configuration.

In some embodiments the flexible frame according to the second aspect of the invention is a foldable solar collector, e.g. for terrestrial or celestial application.

In some other embodiments the collector of electromagnetic radiations according to the second aspect of the invention is able to receive and transmit

electromagnetic radiations, e.g. a transducer designed to transmit or receive electromagnetic waves.

In some embodiments the collector able to receive and transmit electromagnetic radiations is an antenna.

In some embodiments the collector able to receive and transmit electromagnetic radiations is an antenna reflector.

For example an antenna reflector may be a corner reflector which is able to deflect a front of electromagnetic radiations back along a vector that is parallel to but opposite in direction from the radiation's source.

Another example of antenna reflector may be a parabolic reflector which is the most common antenna reflector mainly due to its high gain, which enables high data rate transmission at low power.

The use of mesh antennas, composed by for example by RF reflective mesh may be advantageous. As mesh antennas are generally composed of a knitted lightweight metallic mesh, the flexible frame supporting mesh antennas can be twisted and folded following the method disclosed with no damage to the discontinuous mesh structure. In other embodiments the flexible frame may be supporting inflatable antennas.

For example the flexible frame may support an inflatable antenna made of thin flexible material which is twisted and folded prior to launch and then inflated after deployment in space. Once deployed and inflated the antenna can be made more rigid by either exposing to sun irradiation the flexible material previously impregnated with a resin.

In some other embodiments the collector able to receive and transmit

electromagnetic radiations is a deflector.

A deflector is defined as a device intended to turn aside a flow of electromagnetic radiation. An example of deflector could be a mirror which receives and transmit back electromagnetic radiation in the visible region. Another example of deflector may be a deflector for cosmic radiations, which deployed in space, receives cosmic radiations and bounces them back.

In some embodiments the flexible frame according to the second aspect of the invention is functionally connected to a carrier structure.

The first and second aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The structure according to the invention will now be described in more detail with regard to the accompanying figures. The figures show also ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure Ia is a schematic drawing of the flexible frame.

Figure Ib is a schematic drawing of the flexible frame supporting a collector of EMr.

Figure 2 is a drawing of the flexible frame in the unfolded configuration.

Figure 3a is a drawing of the flexible frame in the twisted configuration. Figure 3b and figure 3c shows two steps of the folding of the flexible frame from the twisted configuration.

Figure 3d shows the folded configuration in a compact configuration.

Figure 4a and 4b show the twisted and folded configuration with three loops, respectively.

Figure 5, 6, 7 show examples of three types of flexible frames supporting a collector of electromagnetic radiations according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure Ia shows a schematic drawing of the flexible frame 1 on which is supported a collector 2 of electromagnetic radiations, shown in figure Ib. The specific outline of the frame is linked to its function. The flexible frame may have any form which has the ability of storing energy in the frame by the method described by the invention and to be folded into a compact configuration. While in this embodiment the flexible frame is shown circular in other embodiments it may assume different forms, e.g. triangular or square.

Figure 2 is a drawing of the flexible frame 1 in the unfolded configuration. The flexible frame may have the characteristics of being light in weight, thin, and highly elastic. It may have a very high yield strength point so that the frame deforms elastically and returns to its original shape, i.e. no plastical deformation is present, even when the high level of mechanical stress is applied. Example of materials that can be used to produce the frame are metal or metal composite such as aluminium or aluminium based alloys, titanium, zinc alloys or magnesium alloys. Polymers, polymer composites or metal/fiber reinforced materials may be also used as flexible frame materials. For celestial applications substantial resistance to cosmic rays is also an important characteristic of the frame and the EMr collector. Therefore, for celestial application polymers or polymer composites maybe not used as frame materials unless presenting sufficient resistance to cosmic rays degradation.

Being the EM collector made of light weight thin films, the flexible frame does not experience a heavy load therefore it can be produced in very thin structure. Figure 3a is a drawing of the flexible frame in the twisted configuration. To deform the flexible frame into the twisted configuration the flexible frame may be hold at its diametrically opposed sides 3 and 4 and then twisted along the axis 5 formed between the two holding positions 3 and 4 as indicated by the arrow 6. In figure 3a the frame is twisted by 180° so that the frame assumes a figure-of-eight shape or two loops 7 and 8 which lie in the same plane. This is particularly advantageous for obtaining a configuration with reduced hindrance, so as to allow the folding of the two loops into a compact and closed coil configuration having two

intermeshing convolutions in the same plane.

Figure 3b and figure 3c show the folding of the flexible frame from the twisted configuration when the two convolutions lie in the same plane. One convolution is folded following the arrow 9 in figure 3b so as to produce a coil configuration where the two intermeshing convolutions are overlapping as shown in figure 3d. In this configuration the coil configuration may be maintained by the presence of means for holding (not shown). The coil configuration may not require a strong holding means. A single or multiple strap thin wire or for celestial application a burnable resistance or a pyrotechnic device are examples of holding means. Other examples of holding means are pin lock type, magnetic lock system or electrically activated hook devices, e.g. the electricity necessary for the opening may be also provided by the solar energy converter in its folded position. Releasing of the holding means allows for restoration of the initial configuration of the flexible frame. The release will be initially slow but will increase its speed of opening proportionally to the elasticity of the frame. Specifically for celestial application the releasing of the stressed configuration by removal of the holding means would be advantageously carried out virtually without introduction of energy in the structure. As the introduction of energy is virtually zero, this is condition is referred here after as energy neutrality. Energy neutrality is advantageous to avoid influence from the releasing of the flexible frame into a system, e.g. a satellite connected to the frame.

In other embodiments the degree of twisting may be different, so that the two loops formed may lie in separate planes. This allows for folding of the two loops formed into a less compact configuration. While the formation of two loops on the same plane is not essential, indeed leads to a very compact folded configuration. The twisting may continue so that formation of more convolutions is possible. For example figure 4a shows the twisted configuration where three loops or

convolutions (10, 11 and 12) lie on the same plane. Figure 4b shows the folded compact configuration where the three convolutions formed are folded to create a closed coil, e.g. by interposing the third convolution between the first and the second convolution. In other embodiments more convolutions can be formed with the advantage of reducing the coil diameter and therefore increasing the stowing capacity.

Figure 5 shows an example of a flexible frame 1 supporting a collector 2 of electromagnetic radiations which is produced in a continuous film sheet. Film sheets can be provided in materials which are light in weight, not brittle, elastic and can be folded without substantial loss of their mechanical, physical and optical properties.

In some embodiments the collector of electromagnetic radiations is formed by units.

Figure 6 shows an embodiment where the flexible frame supports a collector of electromagnetic radiations which is formed by units 13.

In some embodiments the collector of electromagnetic radiations is formed by units mounted on a substrate along reinforced folding lines.

For example when the collector is a solar collector, these units are single solar cells, e.g. 13 mounted on a substrate 14, e.g. a solar sail, and may be connected together. This configuration using single units may be advantageous as more robust to the mechanical stress which occurs during the twisting and folding as the solar cells may be mounted on a substrate along reinforced folding lines.

Figure 7 shows another embodiment where the collector of electromagnetic radiations 16, e.g. a solar cell is provided in a single film with a central void 15. The presence of the void may facilitate the folding of the frame.

EXAMPLE 1

A circular self deployable unfolding solar panel supported by the flexible frame according to the invention with frame thickness of 20 mm have, after twisting, folding and compressing, a compact configuration height of 40 mm in the case of two intermeshing convolution or 60 mm in the case of three intermeshing convolution, with a respective diameter ratio of 1,8 or 2,5.

The satellite M-SAT 1 launched in 1996 had the dimension of a cone truncated with a top diameter of 1500 mm, a bottom diameter of 3000 mm and a cone height of 4900 mm and storing two solar panels.

In a satellite with the dimension of M-SATl, the present method will allow for storing of 62 solar panels with a diameter ranging between 5500-2700 mm or 40 solar panels with a diameter ranging between 7500-3750 mm respectively for the two or three intermeshing convolution coil configuration. Clearly the present method gives an advantage by increasing the storage capacity of a satellite, such M-SATl, by at least 40 times.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A method for stowing a flexible frame supporting a collector of electromagnetic radiations, the method comprising :

• deforming by twisting and folding said flexible frame into a stressed configuration to reduce its size,

• maintaining said flexible frame in said stressed configuration.

2. The method according to claim 1, wherein deforming said flexible frame comprises:

• twisting said flexible frame to obtain at least two loops

• folding said at least two loops into an overlapping configuration.

3. The method according to claim 2, wherein said twisting is by 180° and said at least two loops lie in the same plane.

4. The method according to any of the preceding claims, wherein said deforming said flexible frame further comprises:

• compressing said at least two loops into a compact configuration.

5. The method according to any of the preceding claims, wherein said step of maintaining said flexible frame in said stressed configuration includes the use of means for holding said stressed configuration.

6. The method according to any of the preceding claims further comprising :

• releasing said flexible frame from the stressed configuration.

7. The method according to claim 6, wherein said released flexible frame self restores its initial configuration without any external intervention.

8. The method according any of the preceding claims, wherein said flexible frame is functionally connected to a carrier structure.

9. The method according to any of the preceding claims, wherein said collector of electromagnetic radiations is able to receive and transmit electromagnetic radiations.

10. The method according to any of the preceding claims, wherein said collector of electromagnetic radiations is an antenna.

11. The method according to any of the preceding claims, wherein said collector of electromagnetic radiations is an antenna reflector.

12. The method according to any of the preceding claims, wherein said collector of electromagnetic radiations is a deflector.

13. The method according to any of the preceding claims, where said collector of electromagnetic radiations is a solar collector.

14. The method according to any of the preceding claims, where said collector of electromagnetic radiations is a part of a solar energy converter.

15. A flexible frame supporting a collector of electromagnetic radiations, characterized in that, said flexible frame is twistable into at least two loops and said at least two loops are foldable into an overlapping configuration to provide a compact configuration.

16. The flexible frame defined in claim 15 further comprising means for holding said overlapping configuration.

17. The flexible frame defined in any of the claims 15 or 16, wherein said collector of electromagnetic radiations is able to receive and transmit electromagnetic radiations.

5 18. The flexible frame defined in any of the claims 15-17, wherein said collector of electromagnetic radiations is an antenna.

19. The flexible frame defined in any of the claims 15-17, wherein said collector of electromagnetic radiations is an antenna reflector.

10

20. The flexible frame defined in any of the claims 15-17, wherein said collector of electromagnetic radiations is a deflector.

21. The flexible frame defined in any of the claims 15-20, wherein said collector of 15 electromagnetic radiations is formed by units.

22. The flexible frame defined in any of the claims 15 or 16, wherein said frame is a foldable solar collector.

20 23. The flexible frame defined in claim 22, wherein said frame is a foldable solar collector for celestial application.

24. The flexible frame defined in any of the claims 22 or 23 wherein said solar collector is formed by units mounted on a substrate along reinforced folding lines.

25

25. The flexible frame according to any of the claims, wherein said frame is functionally connected to a carrier structure.