Variable transmission optical solar sail

Abstract

Herein is presented an optical solar sail system attached to a space vehicle acted on by solar radiation emanating in a solar radiation vector comprises: (i) at least one functional surface comprising a designated sheet; (ii) a first controller configured to control the sail's transmission of solar radiation; (iii) a second controller configured to control the satellite orbit and attitude of the space vehicle; and (iv) an energy source in communication with the first controller, wherein the designated sheet of the at least one functional surface is configured to selectively transmit or reflect solar radiation and wherein said the control of said selectivity is configured to enable the at least one functional surface to control the forces resultant from solar radiation pressure acting on at least one space vehicle.

Description

[0001] VARIABLE TRANSMISSION OPTICAL SOLAR SAIL

[0002] FIELD OF THE INVENTION

[0003] This invention relates to space vehicles in general, and to the modulation of solar radiation pressure acting on space vehicles in particular.

[0004] BACKGROUND OF THE INVENTION:

[0005] Controlling the orbit and attitude of space vehicles can be achieved with varying approaches, but the manipulation of the solar radiation pressure acting on the space vehicle allows for significantly lower energy demands, which in turn facilitate the long term operation required by many space vehicle applications. Solar sails are systems designed to exploit the solar radiation pressure produced by solar radiation in an analogous fashion to how sails are used by ships to exploit wind over bodies of water, propelling the vehicle substantially in the direction of the solar radiation. However, controlling the amplitude and direction of the solar radiation pressure acting on a space vehicle equipped with a solar sail is not trivial, and given the very demanding requirements for accuracy and reliability of that control, operators of space vehicles are left to use cruder and more energetically consumptive means of orbit and attitude adjustment to account for the lack of control afforded by solar sail systems.

[0006] These crude and energetically demanding means of space vehicle control preclude the full realization of the potential of using solar sails. Said full realization would exploit the passive acceleration afforded to space vehicles by the manipulation of solar radiation pressure to produce highly efficient and accurately controllable space vehicles for a number of different applications. In order to use only solar radiation pressure for propulsion, a solar sail must be able to selectively vary the effect of solar radiation, in a manner roughly analogous to a wing utilizing control surfaces such as ailerons or rudders rather than simple fixed wing kites. This is the technical problem currently lacking solution, which represents a crucial obstacle in the realization of truly efficient and accurately controllable solar sail systems.

[0007] So called “Electric Solar Sails” were first taught in 2004 by P. Janhunen as means of propulsion in interplanetary space, and is conceptually similar to the “plasma brake ” which could be employed by low Earth orbit satellites to reduce orbit decay time after their operational lifetime has been concluded. Both the E-sail and the plasma brake rely on a network of electrically charged wires extending out from the space vehicle and maintained at a very high voltage, thus producing an electrostatic field that interacts with solar radiation. Both technologies do not employ an actual physical surface, and are prone to a number of mechanical and electrical control vulnerabilities. The benefits of the operating principle of both technologies, however, is a level of tunability regarding the mechanical interaction with solar radiation, thereby - theoretically - affording to a space vehicle a level of control of momentum whilst using an external source of thrust.

[0008] Applying this benefit to conventional solar sail architecture, wherein a reflective surface interacts with the solar radiation and is acted on by solar radiation pressure, has been a research challenge for at least a decade. In the field of metamaterials, which relates to a class of materials able to modulate their functional parameters, some researchers have proposed tunable solar sails by modulating transparency. The practical considerations of building solar sails from this highly mechanically vulnerable and untested class of materials has, unfortunately, precluded their use in the realization of a tunable solar sail.

[0009] To the best of the authors’ understanding, no publication of the prior art teaches a method for varying the effect of solar radiation pressure on the surface of solar sail, and therefore no person skilled in the art or having ordinary skill in the art could conceivably realize a system capable of varying the effect of solar radiation pressure and the resultant forces on a vehicle travelling through space.

[0010] SUMMARY OF THE INVENTION:

[0011] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, devices and methods which are meant to be exemplary and illustrative and not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other advantages or improvements.

[0012] According to a first aspect of the invention, an optical solar sail system attached to a space vehicle acted on by solar radiation emanating in a solar radiation vector comprises: (i) at least one functional surface comprising a designated sheet; (ii) a first controller configured to control the sail’s transmission of solar radiation; (iii) a second controller configured to control the satellite orbit and attitude of the space vehicle; and (iv) an energy source in communication with the first controller, wherein the designated sheet of the at least one functional surface is configured to selectively transmit or reflect solar radiation and wherein said the control of said selectivity is configured to enable the at least one functional surface to control the forces resultant from solar radiation pressure acting on at least one space vehicle.

[0013] According to another aspect of the invention, the selectivity of the designated sheet is enabled by controlling the voltage and gradient thereof across the designated sheet.

[0014] According to another aspect of the invention, the selectivity of the designated sheet is enabled by controlling the temperature and gradient thereof across the designated sheet.

[0015] According to another aspect of the invention, the selectivity of the designated sheet is enabled by controlling relative mechanical position of sheet components. According to another aspect of the invention, the transmission of the designated sheet is determined by its transparency / opaqueness properties. When the space vehicle is in solar shadow, and thus when the functional surface is not intercepted by a solar radiation vector, the ability of said functional surface to selectively transmit or reflect said solar radiation reduces to a point of negligibility with respect to control of the space vehicle. If the space vehicle is both in solar shadow and in a region of orbit with some extent of atmospheric density, then the functional surface can be operated as a passive control surface to modulate the extent and transformation of atmospheric drag.

[0016] According to another aspect of the invention, the vector normal to the plane of the at least one functional surface is configured to be modulated to control the forces acting on the at least one space vehicle.

[0017] According to another aspect of the invention, the vector normal to the plane of the at least one functional surface is configured to be modulated relative to the solar radiation vector.

[0018] According to another aspect of the invention, the solar sail is configured to be folded and unfolded by a designated mechanism.

[0019] According to another aspect of the invention, the solar sail further comprises at least one reflector whose reflective surface is not in the plane of the functional surface, and wherein said reflector is located behind the designated sheet of the at least one functional surface with respect to the vector of solar radiation.

[0020] According to another aspect of the invention, the orientation of the at least one reflector is relative to the at least one functional surface is controllable by the first controller. According to another aspect of the invention, control of the properties of the designated sheet of the at least one functional surface is configured to modulate the solar radiation pressure acting on the at least one reflector.

[0021] According to another aspect of the invention, control of the properties of the designated sheet of the at least one functional surface is configured to induce angular torque on the space vehicle in the plane normal to the vector of solar radiation.

[0022] According to another aspect of the invention, control of the properties of the designated sheet of the at least one functional surface is configured to provide control over the space vehicle’s attitude.

[0023] According to another aspect of the invention, wherein: (i) the at least one functional surface is not in the plane normal to the vector of solar radiation; and (ii) the center of at least one of the at least one functional surfaces does not intersect the path of solar radiation intersecting the center of mass of the space vehicle, such that the selectivity of said at least one of the at least one functional surfaces is configured to induce rotation of the space vehicle in the plane normal to the vector of solar radiation.

[0024] According to another aspect of the invention, each of the at least one functional surfaces are controlled independently by the first controller.

[0025] According to another aspect of the invention, the transmission of solar radiation by the at least one functional surface is modulated for a designated duration by the first controller.

[0026] According to another aspect of the invention, the second controller modulates the first controller to modulate the selectivity of the at least one functional surface to modulate the apogee of the space vehicle in orbit. According to another aspect of the invention, the space vehicle is an artificial satellite.

[0027] According to another aspect of the invention, the first controller and second controller are combined into a multi-functional controller.

[0028] According to another aspect of the invention, a method for modulating the solar radiation pressure acting on a space vehicle comprises the steps of: (i) configuring an optical sail system comprising at least one functional surface having a designated sheet in a plane intersecting with the vector of solar radiation; (ii) controlling the transmission of solar radiation through said designated sheet of the at least one functional surface with a first controller; (iii) modulating the forces acting on the space vehicle resulting from solar radiation pressure produced by the solar radiation transmitted or reflected through the at least one functional surface with a second controller; and (iv) adjusting the orbit or attitude of the space vehicle with the resultant forces produced by the solar radiation pressure, whereby the extent of solar radiation transmitted or reflected by an optical sail system produces solar radiation pressure that generates forces that act on the space vehicle to modulate its attitude and / or orbit.

[0029] According to another aspect of the invention, the method for modulating the solar radiation pressure acting on a space vehicle further comprises a step operated before step (iii): configuring at least one reflector whose reflective surface is not in the plane of the functional surface, wherein said reflector is positioned behind the at least one functional surface with respect to the vector of solar radiation.

[0030] According to another aspect of the invention, the solar radiation pressure acting on the at least one reflector produces a resultant force acting on the space vehicle that rotates the space vehicle in a plane substantially normal to the vector of solar radiation. According to another aspect of the invention, the plane of the at least one functional surface of the optical sail is not normal to the vector of solar radiation, such that solar radiation pressure acting on the space vehicle not in the path intersection the space vehicle’s center of gravity produces a rotational force on the space vehicle substantially in the plane normal to the vector solar radiation.

[0031] According to another aspect of the invention, the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface is achieved by the modulation of temperature and gradient thereof across the designated sheet.

[0032] According to another aspect of the invention, the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface is achieved by the modulation of voltage and gradient thereof across the designated sheet.

[0033] According to another aspect of the invention, the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface is achieved by the relative mechanical position of components of the designated sheet.

[0034] BRIEF DESCRIPTION OF THE FIGURES:

[0035] Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments may be practiced. The figures are for the purpose of illustrative description and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention.

[0036] FIGS. 1A & IB constitute an overview of a space vehicle equipped with a solar sail, according to two embodiments of the invention. FIGS. 2A & 2B constitute a schematic demonstrating attitude control in two dimensions afforded to a space vehicle equipped with a solar sail, according to two embodiments of the invention.

[0037] FIGS. 3A & 3B constitute a schematic demonstrating torque control around the vector of solar radiation, according to some embodiments of the invention.

[0038] FIG. 4A-4D constitutes four schematics of active reflector devices, according to some embodiments of the invention.

[0039] FIG. 5A-5H constitute a series of schematics demonstrating the linear control of transmission across the solar sail, according to some embodiments of the invention.

[0040] FIGS. 6A-C constitutes three schematics demonstrating the torque control afforded to a solar sail installed with rings of passive reflector devices, according to some embodiments of the invention.

[0041] DETAILED DESCRIPTION OF SOME EMBODIMENTS:

[0042] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components, modules, units and / or circuits have not been described in detail so as not to obscure the invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0043] Throughout the following detailed description of some embodiments, the term “center of pressure ” refers to the point on a surface where the total sum of solar radiation pressure acts on the surface. The term “positional translation ” refers to the controlled movement in physical space, which can refer to modulations of a space vehicle’s attitude or orbit, depending on the astrodynamics context in which said space vehicle is in.

[0044] Reference is made FIG. 1, which constitutes an overview of a space vehicle equipped with a solar sail, according to two embodiments of the invention.

[0045] In FIG. 1A, a tethered configuration 101 configures a space vehicle 105 to a solar sail 110 having four quarters 121, 122, 123, and 124, each composed of a plurality of tiles comprising a functional surface with a designated sheet. At the center of the solar sail 110 is the central point 130, out from which the divisions 140 between the four quarters 121, 122, 123, and 124. At the furthest point of the divisions 140 are points 150 which are connected by tethers 170 to the space vehicle 105. The tethered control of the solar sail 110 with respect to the space vehicle 105 affords the latter control over the center of gravity of the combined apparatus, which can be integrated into the second controller of the invention to calculate the effect the variable properties of different tiles of the solar sail 110 will have on the forces resulting from the solar radiation pressure.

[0046] In FIG. IB, a fixed configuration 102 configures a space vehicle 105 to a solar sail 110 having four quarters 121, 122, 123, and 124, each composed of a plurality of tiles comprising a functional surface with a designated sheet. At the center of the solar sail 110 is the space vehicle 105 itself, out from which the dividers 140 between the four quarters 121, 122, 123, and 124. Without tethers, the fixed configuration has a greater degree of mechanical durability, and can maintain control of the forces acting on the space vehicle 105 as a result of solar radiation pressure acting on the solar sail 110 by varying the extent to which solar radiation reflects from or transmits through the designated sheet of the functional surfaces of each of the plurality of tiles in each of the quarters of the solar sail.

[0047] A person skilled in the art will recognize that the division of a solar sail into four geometrically equivalent quadrants is an arbitrary division, and according to different embodiments of the invention a solar sail may be divided into any number of equivalent or non-equivalent sections.

[0048] Reference is drawn to FIG. 2, which constitutes a schematic demonstrating attitude control in two dimensions afforded to a space vehicle equipped with a solar sail, according to two embodiments of the invention. A space vehicle 105 and solar sail 110 are positioned such that the former is in the center of the latter when normal to the vector of solar radiation, which is the viewing perspective. The solar sail 110 has four quarters 121, 122, 123, and 124 each composed of a plurality of tiles comprising a functional surface with a designated sheet, wherein the four quarters are divided by dividers 140.

[0049] In FIG. 2A, a movement of the space vehicle 105 is controlled by the variable transmission of solar radiation through the solar sail 110 as a result of the tuning of the designated sheet of each of the functional surfaces in the plurality of tiles from which the solar sail 110 is composed. A target coordinate 201 is defined by a second controller in the space vehicle 105, according to some embodiments, and the tangential coordinate 210 and radial coordinate 220 is thereby defined. In order to achieve the movement defined by said coordinates, the designated sheets of the functional surfaces in the plurality of tiles in an area 230 of the solar sail are tuned to be reflective, and therefore to be acted upon by solar radiation pressure, whilst the remaining area 240 of the solar sail is tuned to transmit solar radiation, and therefore not to be acted upon by solar radiation pressure. In this way, a space vehicle 105 configured with a solar sail 110 can tune the position of the center of pressure on the solar sail 110, and thereby operate and modulate positional translations in both radial and tangential coordinates, using only the passive solar radiation as a means of propulsion.

[0050] In FIG. 2B, the solar transmission properties of the four quarters 121, 122, 123, and 124 can be modulated in order to produce tunable positional translations in the X 250 and Y 260 directions. By maintaining any quarter as either opaque or transparent and then pulsing the opposing quarter, the location of the center of pressure can be selected with respect to the space vehicle 105 on the solar sail 110 in either the X 250 or Y 260 coordinates.

[0051] For example, maintaining quarter 121 as opaque and pulsing quarter 123 will produce a center of pressure substantially within the quarter 121 but closer to the space vehicle 105 than without the pulsing, and by increasing the duration in a pulse of quarter 123 in which said quarter is opaque, the center of pressure is brought closer to the space vehicle. Similarly, maintaining quarter 122 as transparent and pulsing quarter 124 will produce a center of pressure substantially within the quarter 142 but closer to the space vehicle 105 than without the pulsing, and by increasing the duration in a pulse of quarter 123 in which said quarter is transparent, the center of pressure is brought closer to the space vehicle. These relationships can be modulated together simultaneously so as to position the center of pressure anywhere on the solar sail 110, thereby moving the space vehicle in both the X 250 or Y 260 coordinates.

[0052] It will be appreciated by person skilled in the art that the division of four quarters is a simplification, and that any number or configuration of solar sails according to other embodiments of the invention can maintain the same functionality as demonstrated in FIG. 2. Reference is drawn to FIG. 3, which constitutes a schematic demonstrating torque control around the vector of solar radiation, according to some embodiments of the invention. In FIG. 3A, a solar sail 110 having a center 140 is positioned normal to the vector of solar radiation, such that the axis 305 is parallel to said vector and intersects with said center. In each of the four quarters there are two tiles 301 and 302 having a functional surface with a designated sheet through which the transmission of solar radiation can be tuned, wherein the configuration of tiles 301 and 302 is arranged with rotational symmetry around axis 305. In FIG. 3B, a side view of tiles 301 and 302 is shown, with a reflector device 340 positioned beneath, and solar radiation emanating from above. For tile 302, the solar radiation 320 reflects off the tile itself, producing a solar radiation pressure that acts on the tile in the opposite direction to the reflected solar radiation. However, by modulating the properties of tile 301 to maintain its transparency to solar radiation, solar radiation 330 is allowed to pass to the right hand surface 345 of the reflector device 340, thereby reflecting to the right side direction 335 and producing a solar radiation pressure that acts on the reflector device in the opposite direction to the reflected solar radiation 335. Due to the opacity of the tile 302, the solar radiation 320 does not reach the left hand surface 346, though this can also be modulated to counteract the forces produced by the solar radiation on surface 345 by tuning the tile 302 to be more transparent to solar radiation 320.

[0053] When the configurations shown in FIG. 3B are operated as in FIG. 3A, the space vehicle can achieve a torque in a counterclockwise direction around the axis 305 from the perspective of the solar radiation. Similarly, torque can be applied in a clockwise direction around the axis 305 from the perspective of the solar radiation if tile 301 is tuned to be opaque and tile 302 is tuned to be transparent. According to other embodiments of the invention, the reflector device has surfaces positioned at any angle, either in a fixed or adaptable position, wherein the direction of reflected solar radiation, and therefore the vector of solar radiation pressure produced thereby, is also able to be modulated. According to other embodiments of the invention, the reflector device only has one surface. According to other embodiments of the invention, the reflector device has three or more surfaces.

[0054] Embodiments of the present invention can be divided into three categories: (a) as utilizing passive reflector devices; (b) as utilizing active reflector devices; and (c) not utilizing any reflector devices. In the third case, if the solar sail deviates from the plane normal to the vector of solar radiation, then the vector of solar radiation pressure will also deviate from the vector of solar radiation, and thus affect an attitude adjustment on the space vehicle. As such, a space vehicle equipped with the solar sail of the present invention does not actually require a reflector device positioned on the opposing side of the solar sail with respect to the source of solar radiation, however the attitude control afforded to such a space vehicle may be limited in many instances, not least in not providing any means of deviation from the plane normal to the vector of solar radiation if the solar sail is not already deviated. For this reason, both passive and active reflector devices in a range of embodiments are taught herein.

[0055] According to some embodiments, the solar sail is composed of multiple solar sails in different planes, such that there is always a solar sail not in plane with the plane normal to the vector of solar radiation. According to some other embodiments, the solar sail is at least partially curved, so that at least some regions of the solar sail are not in plane with the plane normal to the vector of solar radiation, even the majority of the solar sail substantially is.

[0056] Reference is drawn to FIG. 4, which constitutes four schematics of active reflector devices, according to some embodiments of the invention. In each of the schematics FIG. 4A-D, a solar sail is positioned above the device, such that solar radiation can be selectively transmitted onto said reflector devices. In FIG. 4A, a simple reflector device 401 is mounted on a rotatable base 405, and contains two reflective surfaces 410 and 420. In FIG. 4B, a simple reflector device 402 is mounted on a rotatable base 405, and contains a single reflective surface 430. In FIG. 4C, a more complex reflector device 403 is mounted on a rotatable base 405, and contains a single reflective surface 430 itself rotatable with a limited range of motion through an axel 440. In FIG. 4D, a yet more complex reflector device 404 is mounted on a rotatable base 405, and contains a single reflective surface 430 itself rotatable with an expanded range of motion through an axel 450. By installing one or more active reflector devices on the side of solar sail opposite to the source of solar radiation, solar radiation can be utilized to afford to the space vehicle a fine and adaptive level of attitude and orbit control, without necessarily modifying the position of the solar sail itself.

[0057] Reference is drawn to FIG. 5, which constitutes a series of schematics demonstrating the linear control of transmission across the solar sail, according to some embodiments of the invention. A square solar sail has corners 501, 502, 503, and 504, and is composed of a plurality of tiles comprising a functional surface with a designated sheet. By modulating the properties of the designated sheets in each of the functional surfaces in each of the tiles to transmit or reflect solar radiation, the solar radiation pressure on each tile can be modulated. By producing a linear gradient, this effect and its resultant effect on the positional translation of the space vehicle can be modulated in highly controllable manner. In FIGs. 5A-D said linear gradient is modulated substantially between the dividers connecting the 501, 502, 503, and 504, whilst in FIGs. 5E- H said linear gradient is modulated substantially along the dividers connecting the 501, 502, 503, and 504. Reference is made to FIG. 6, which constitutes three schematics demonstrating the torque control afforded to a solar sail installed with rings of passive reflector devices, according to some embodiments of the invention. In many cases, it will be desirous for a space vehicle to utilize rings of passive reflector devices 650 with reflective surfaces 660 to produce torque control. According to some embodiments of the invention, a solar sail is installed with a ring 630 of passive reflector devices 650 having a single reflective surface 660 on the opposing side of the solar sail to the source of solar radiation, and wherein said ring of passive reflectors is configured to reflect solar radiation in manner that produces a substantive torque in the clockwise direction. According to other embodiments, a solar sail is installed with a ring 640 of passive reflector devices 650 having a single reflective surface 660 on the opposing side of the solar sail to the source of solar radiation, and wherein said ring of passive reflectors is configured to reflect solar radiation in manner that produces a substantive torque in the counterclockwise direction. In the case presented in FIG. 6A, a transmission distribution configuration 610 ensures that the ring 640 receives solar radiation, such that the dark shading indicates transmission, and thus that the solar sail in FIG. 6A produces a counterclockwise rotation around the vector of solar radiation. In the case presented in FIG. 6B, a transmission distribution configuration 620 ensures that the ring 630 receives solar radiation, such that the dark shading indicates transmission, and thus that the solar sail in FIG. 6B produces a counterclockwise rotation around the vector of solar radiation. In FIG. 6C, a schematic of each of the rings 630 and 640 of passive reflector devices 650 having a single reflective surface 660 is shown, according to some embodiments. According to other embodiments, the ring of reflectors is a continuous ring with a single continuous reflective surface.

[0058] According to some embodiments, the transmissive properties of tiles of the solar sail are modulated with a pulse wave modulation (PWM) pattern, affording to the controllers of the solar sail’s transmissive properties a fine level of control for a greater adaptability of the space vehicle’s position in its orbit.

[0059] Although the present invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.

Claims

CLAIMS1. An optical solar sail system attached to a space vehicle acted on by solar radiation emanating in a solar radiation vector, comprising:(i) at least one functional surface comprising a designated sheet;(ii) a first controller configured to control the sail’s transmission of solar radiation;(iii) a second controller configured to control the satellite orbit and attitude of the space vehicle; and(iv) an energy source in communication with the first controller, wherein the designated sheet of the at least one functional surface is configured to selectively transmit or reflect solar radiation and wherein said the control of said selectivity is configured to enable the at least one functional surface to control the forces resultant from solar radiation pressure acting on at least one space vehicle.

2. The system of claim 1, wherein the selectivity of the designated sheet is enabled by controlling the voltage and gradient thereof across the designated sheet.

3. The system of claim 1 , wherein the selectivity of the designated sheet is enabled by controlling the temperature and gradient thereof across the designated sheet.

4. The system of claim 1, wherein the selectivity of the designated sheet is enabled by controlling relative mechanical position of sheet components.

5. The system of any one of claims 2 or 3, wherein the transmission of the designated sheet is determined by its transparency / opaqueness properties.

6. The system of claim 1, wherein the vector normal to the plane of the at least one functional surface is configured to be modulated to control the forces acting on the at least one space vehicle.

7. The system of any one of claims 1 or 6, wherein the vector normal to the plane of the at least one functional surface is configured to be modulated relative to the solar radiation vector.

8. The system of claim 1, wherein the solar sail is configured to be folded and unfolded by a designated mechanism.

9. The system of claim 1, wherein the solar sail further comprises at least one reflective element whose reflective surface is not in the plane of the functional surface, and wherein said reflective element is located behind the designated sheet of the at least one functional surface with respect to the vector of solar radiation.

10. The system of claim 9, wherein the orientation of the at least one reflective element is relative to the at least one functional surface is controllable by the first controller.

11. The system of any one of claims 9 or 10, wherein control of the properties of the designated sheet of the at least one functional surface is configured tomodulate the solar radiation pressure acting on the at least one reflective element.

12. The system of claim 11, wherein control of the properties of the designated sheet of the at least one functional surface is further configured to induce angular torque on the space vehicle in the plane normal to the vector of solar radiation.

13. The system of claim 11 , wherein control of the properties of the designated sheet of the at least one functional surface is further configured to provide control over the space vehicle’s attitude.

14. The system of any one of claims 1-4, wherein:(i) the at least one functional surface is not in the plane normal to the vector of solar radiation; and(ii) the center of at least one of the at least one functional surfaces does not intersect the path of solar radiation intersecting the center of mass of the space vehicle, such that the selectivity of said at least one of the at least one functional surfaces is configured to induce rotation of the space vehicle in the plane normal to the vector of solar radiation.

15. The system of claim 1, wherein each of the at least one functional surfaces are controlled independently by the first controller.

16. The system of claim 1 , wherein the transmission of solar radiation by the at least one functional surface is modulated for a designated duration by the first controller.

17. The system of any one of claims 1-4, wherein the second controller modulates the first controller to modulate the selectivity of the at least one functional surface to modulate the apogee of the space vehicle in orbit.

18. The system of claim 1, wherein the space vehicle is an artificial satellite.

19. The system of claim 1, wherein the first controller and second controller are combined into a multi-functional controller.

20. A method for modulating the solar radiation pressure acting on a space vehicle, comprising the steps of:(i) configuring an optical sail system comprising at least one functional surface having a designated sheet in a plane intersecting with the vector of solar radiation;(ii) controlling the transmission of solar radiation through said designated sheet of the at least one functional surface with a first controller;(iii) modulating the forces acting on the space vehicle resulting from solar radiation pressure produced by the solar radiation transmitted or reflected through the at least one functional surface with a second controller; and(iv) adjusting the orbit or attitude of the space vehicle with the resultant forces produced by the solar radiation pressure, whereby the extent of solar radiation transmitted or reflected by an optical sail system produces solar radiation pressure that generates forces that act on the space vehicle to modulate its attitude and / or orbit.

21. The method of claim 20, further comprising a step operated before step (iii): configuring at least one reflective element whose reflective surface is not in the plane of the functional surface, wherein said reflective element is positioned behind the at least one functional surface with respect to the vector of solar radiation.

22. The method of claim 21, wherein the solar radiation pressure acting on the at least one reflective element produces a resultant force acting on the space vehicle that rotates the space vehicle in a plane substantially normal to the vector of solar radiation.

23. The method of claim 20, wherein the plane of the at least one functional surface of the optical sail is not normal to the vector of solar radiation, such that solar radiation pressure acting on the space vehicle not in the path intersection the space vehicle’s center of gravity produces a rotational force on the space vehicle substantially in the plane normal to the vector solar radiation.

24. The method of claim 20, wherein the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface isachieved by the modulation of temperature and gradient thereof across the designated sheet.

25. The method of claim 20, wherein the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface is achieved by the modulation of voltage and gradient thereof across the designated sheet.

26. The method of claim 20, wherein the selectivity of transmission of solar radiation through the designated sheet of the at least one functional surface is achieved by the relative mechanical position of components of the designated sheet.

Images