MADE-IN-SPACE TELESCOPES
20240369820 ยท 2024-11-07
Inventors
Cpc classification
B64G1/222
PERFORMING OPERATIONS; TRANSPORTING
International classification
B64G1/10
PERFORMING OPERATIONS; TRANSPORTING
Abstract
Disclosed is a made-in-space telescope (52a) comprising primary mirror made by spinning liquid precursor in two orthogonal axes to form a paraboloid surface and subsequently allowing or causing it to solidify. Several mirror material variants are disclosed. Depending on mirror material used, it can be subsequently coated with reflecting coating.
Extended/deployed (120a) or formed (130) boom assists in controlling the spin of the telescope for mirror forming.
Several telescope embodiments based on the boom design are disclosed.
Boom variants include 3-D printed/extruded (130), corrugated (120), telescopic (190a), coiled (192a), folded (193c), taut cable (195a), stiffened cable ((197), and compound boom made with anisotropically pliable elements (198).
Several system elements such as primary mirror support (42a), supporting struts (160) and (162), and several boom variants (120), (140), (192a) are made with shape memory materials and deploy from their stowed configurations upon being heated.
Heat pipe based implementations are additionally disclosed for heat-activated shape memory system elements.
Claims
1. A space-based imaging system comprising an imaging mirror, said mirror having a generally parabolic cross section along at least one of its axes, said mirror supported by a mirror support structure, wherein said mirror is produced from solidified liquid precursor material while said imaging system is in space, wherein said mirror support structure comprises substantially a disk, said disk further comprising a top surface and a bottom surface, said disk further comprising circular edge wall, said wall perpendicular to said top surface of said disk, said wall located along a periphery of said disk and in communication therewith, wherein said system further comprises a substantially elongated counterweight boom, said boom perpendicular to said top surface of said disk, said boom disposed to face said top surface of said disk and extend distally from it, said boom located along the line through the center of said top surface of said disk, said boom in communication with said imaging system by its proximal terminus only, said disk capable of being rotated around a first axis, said first axis perpendicular to said top surface of said disk and disposed through a center of combined mass of said disk and said boom, said disk capable of being simultaneously rotated around a second axis, said second axis orthogonal to said first axis, wherein center of rotation around said second axis is disposed through a center of combined mass of said disk and said boom.
2. The system of claim 1, further comprising at least one reflective coating on said mirror surface, said coating deposited onto said mirror surface while said imaging system is in space.
3. The system of claim 1 wherein said mirror support structure further comprises at least one light baffle.
4. The system of claim 1 wherein said mirror support structure further comprises at least one aperture.
5. The system of claim 1, wherein said precursor material is selected from the group consisting of: a. alkali metals, b. aluminum, c. mercury, d. metals and alloys thereof, e. metal glasses and alloys thereof, f. epoxies and mixtures thereof, g. epoxies containing thermal expansion coefficient-reducing additives, h. thermoplastic polymers and mixtures thereof, i. thermoplastic polymers containing thermal expansion coefficient-reducing additives, j. thermosetting polymers and mixtures thereof, k. thermosetting polymers containing thermal expansion coefficient-reducing additives, l. glasses and mixtures thereof, m. pitch and mixtures thereof, n. sugar solutions, o. aqueous solutions and p. photocurable polymers and mixtures thereof. q. photopolymers containing thermal expansion coefficient-reducing additives, r. cycloaliphatic epoxies and mixtures thereof, s. cyanoacrylates and mixtures thereof t. styrenic compounds, u. vinyl ethers, v. N-vinyl carbazoles, w. lactones, x. lactams, y. cyclic ethers, z. cyclic acetals, aa. cyclic siloxanes, bb. phthalic diglycol diacrylates,
6. The system of claim 1 further comprising at least one radiation source, said radiation source emitting radiation capable of solidifying said precursor upon exposure.
7. The system of claim 1, wherein said precursor material is liquefied while in space prior to production of said mirror.
8. The imaging system of claim 1, further comprising rotation system, said rotation system capable of rotating said imaging system simultaneously along said first axis and said second axis, said rotation system is selected from the group consisting of: a. propulsion systems based on chemical reactions, b. propulsion systems based on decomposition of materials, c. propulsion systems based on vaporization, d. propulsion systems based on compressed gas or gases, e. positioning systems based on moving inertial mass or masses, f. propulsion systems based on ion propulsion.
9. The imaging system of claim 1, wherein said mirror support structure further comprises a heater.
10. The imaging system of claim 1, wherein said mirror support material is selected from a group consisting of: a. shape memory materials, b. superelastic materials, c. pliable materials.
11. The imaging system of claim 1, wherein said boom is selected from a group consisting of: a. deployable structures created via additive manufacturing process or processes, b. deployable structures created via extrusion process or processes, c. deployable structures made with shape memory materials, d. deployable foldable structures, e. deployable telescopic structures, f. deployable uncoiling helical structures, g. deployable structures comprising pliable members which stiffen during and after deployment, h. deployable structures comprising pliable members which form stiff assemblies when held together during and after deployment, i. pliable members deployed and tensioned by a tractor craft, j. deployable structures made with shape memory materials utilizing heat pipe technology, k. hereinabove members comprising counterweight at their distal termini, l. hereinabove members comprising deployment velocity reducing elements, m. hereinabove members comprising vibration reducing elements.
12. The imaging system of claim 1, wherein said boom is capable of being severed from the rest of said system.
13. A space-based imaging system comprising an imaging mirror assembly, said mirror assembly further comprising a mirror support, said support comprising substantially a disk, said disk further comprising a top surface and a bottom surface, said top surface further comprising a substantially circular wall along its periphery, said wall perpendicular to said top surface and in cooperation therewith, said imaging system further comprising a substantially elongated counterweight boom, said boom perpendicular to said top surface of said disk, said boom disposed to face said top surface of said disk and extend distally from it, said boom in communication with said imaging system by its proximal terminus only, said imaging system capable of rotating along two orthogonal axes, namely, first axis and second axis, said first axis passing perpendicular to said top surface of said support and through combined center of gravity of said support and said boom, wherein a center of rotation around said second axis is through center of gravity of said support and said boom, said imaging system further comprising a dispensing mechanism for introducing liquid precursor material into said support to produce said mirror upon solidification, said mirror produced while said system is in space.
14. The system of claim 13, wherein said precursor material is selected from the group consisting of: a. alkali metals, b. aluminum, c. mercury, d. metals and alloys thereof, e. metal glasses and alloys thereof, f. epoxies and mixtures thereof, g. epoxies containing thermal expansion coefficient-reducing additives, h. thermoplastic polymers and mixtures thereof, i. thermoplastic polymers containing thermal expansion coefficient-reducing additives, j. thermosetting polymers and mixtures thereof, k. thermosetting polymers containing thermal expansion coefficient-reducing additives, l. glasses and mixtures thereof, m. pitch and mixtures thereof, n. sugar solutions, o. aqueous solutions and p. photocurable polymers and mixtures thereof. q. photopolymers containing thermal expansion coefficient-reducing additives, r. cycloaliphatic epoxies and mixtures thereof, s. cyanoacrylates and mixtures thereof t. styrenic compounds, u. vinyl ethers, v. N-vinyl carbazoles, w. lactones, x. lactams, y. cyclic ethers, z. cyclic acetals, aa. cyclic siloxanes, bb. phthalic diglycol diacrylates,
15. The system of claim 13 wherein said support structure further comprises at least one light baffle.
16. The system of claim 13 wherein said support structure further comprises at least one aperture.
17. The system of claim 13 wherein said support structure further comprises at least one heating element.
18. The imaging system of claim 13, wherein said mirror support material is selected from a group consisting of: a. shape memory materials, b. superelastic materials, c. pliable materials.
19. The system of claim 13, wherein said boom is selected from a group consisting of: a. deployable structures created via additive manufacturing process or processes, b. deployable structures created via extrusion process or processes, c. deployable structures made with shape memory materials, d. deployable foldable structures, e. deployable telescopic structures, f. deployable uncoiling helical structures, g. deployable structures comprising pliable members which stiffen during deployment, h. deployable structures comprising pliable members which form stiff assemblies when held together during deployment, i. pliable members deployed and tensioned by a tractor craft, j. deployable structures made with shape memory materials utilizing heat pipe technology, k. hereinabove members comprising counterweight at their distal termini, l. hereinabove members comprising deployment velocity reducing elements, m. hereinabove members comprising vibration reducing elements.
20. The system of claim 13 further comprising rotation inducing system, said rotation inducing system capable of rotating said imaging system simultaneously around said first axis and said second axis.
21. The system of claim 13 wherein said dispensing mechanism comprises a container, said container containing said precursor material, said container further comprising an egress aperture for said precursor material, said aperture communicating with said mirror support.
22. The container of claim 21 further comprising at least one heater element.
23. The container of claim 21 further comprising a piston within, said piston capable of moving inside said cylinder, said piston capable of ejecting said precursor material through said egress aperture, said piston being driven by a piston driving mechanism.
24. The container of claim 23 further comprising at least one heater element.
25. The container of claim 23 wherein said piston driving mechanism is selected from the group consisting of: a. compressed gas, b. compressed elastic element, c. shape memory actuator, d. electrical motor drive assembly, e. pyrotechnical gas generator f. gas or vapor generator based on decomposition of materials.
26. The imaging system of claim 13 further comprising at least one radiation source, said radiation source emitting radiation capable of solidifying said precursor upon exposure.
27. The imaging system of claim 13 further comprising a rotation system, said rotation system capable of rotating said imaging system simultaneously along said first axis and said second axis, said rotation system is selected from the group consisting of: a. propulsion systems based on chemical reactions, b. propulsion systems based on decomposition of materials, c. propulsion systems based on vaporization, d. propulsion systems based on compressed gas or gases, e. positioning systems based on moving inertial mass or masses, f. propulsion systems based on ion propulsion.
28. A method of producing while in space an imaging system based on a paraboloid mirror comprising the steps of: a. providing mirror support structure, said support structure comprising substantially a circular disk, said disk comprising two surfaces, namely, a top surface and a bottom surface, said disk further comprising a circular wall, said wall perpendicular to said top surface, said wall located along a periphery of said disk, said wall located on said top surface and in communication therewith, b. extending or generating a substantially elongated counterweight boom, said boom perpendicular to said top surface, said boom located along the line through the center of said top surface, said boom extending distally from said top surface of said disk, said boom in communication with said imaging system by its proximal terminus only, c. spinning said support structure around a first axis, said first axis perpendicular to said top surface of said disk and disposed through a center of combined mass of said disk and said boom, d. simultaneously spinning said support structure around a second axis, said second axis orthogonal to said first axis, wherein center of rotation around said second axis is through a center of combined mass of said disk and said boom, e. placing a mirror precursor material on said top surface of said disk, f. allowing said precursor material to assume a parabolic shape as a result of said structure spinning around said first and said second axes, g. subsequently allowing or causing said precursor material to solidify in said parabolic shape.
29. The method of claim 28, wherein said liquid precursor material is stored in liquid form within said system prior to production of said mirror.
30. The method of claim 28, wherein said liquid precursor material is produced in space by liquefying a solid precursor material.
31. The method of claim 28, wherein said precursor material is selected from the group consisting of: a. alkali metals, b. aluminum, c. mercury, d. metals and alloys thereof, e. metal glasses and alloys thereof, f. epoxies and mixtures thereof, g. epoxies containing thermal expansion coefficient-reducing additives, h. thermoplastic polymers and mixtures thereof, i. thermoplastic polymers containing thermal expansion coefficient-reducing additives, j. thermosetting polymers and mixtures thereof, k. thermosetting polymers containing thermal expansion coefficient-reducing additives, l. glasses and mixtures thereof, m. pitch and mixtures thereof, n. sugar solutions, o. aqueous solutions and p. photocurable polymers.
32. The method of claim 28, further comprising the steps of depositing at least one reflective coating on a surface of said mirror upon its solidification.
33. The method of claim 28, wherein said mirror support material is selected from a group consisting of: a. shape memory materials, b. superelastic materials, c. pliable materials.
34. The method of claim 28, wherein said support structure further comprises at least one heating element.
35. The method of claim 28, wherein said mirror precursor material upon solidification can be subsequently re-melted and re-formed.
36. The method of claim 28, wherein said support structure further comprises at least one source for curing polymers.
37. The method of claim 28, wherein said boom is selected from a group consisting of: a. deployable structures created via additive manufacturing processes, b. deployable structures created via extrusion processes, c. deployable structures made with shape memory materials, d. deployable foldable structures, e. deployable telescopic structures, f. deployable structures comprising pliable members which stiffen during deployment, g. deployable structures comprising pliable members which form stiff assemblies when assembled together during deployment, h. pliable members tensioned by a tractor craft, i. hereinabove members comprising counterweight at their distal termini.
38. The method of claim 28 where said boom is capable of being severed from the rest of said system.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DESCRIPTION OF THE EMBODIMENTS
[0158] In the foregoing description like components are labeled by the like numerals.
[0159] It should be noted that the collective designation telescope refers not only to telescopes in the conventional sense, but space-borne structures utilizing imaging systems.
[0160] There are two fundamental telescope designs presently disclosed, namely, 1. a direct imaging type, and 2. a Cassegrain-type with a folded light path.
[0161] The direct-imaging system uses the primary mirror 40a and imager system 24 located in integrated assembly 70.
[0162] The Cassegrain telescope design uses two mirrors: primary mirror 42a and secondary mirror 25 located in integrated assembly 72. Primary mirror 42a has aperture 44 in its center to permit light reflected by secondary mirror 25 to reach imager system 80 located in main system enclosure 170.
[0163] There are two major types of the deployable mirror support disclosed: rigid supports 40 and 42 which are both based on shape memory materials, and pliable support 450 stretched for deployment by shape memory support hoops 400 or 420, or their respective superelastic variants 401 and 421.
[0164] Referring to
[0165] Mirror support 42 is further connected to integrated assembly 72 by deployable struts 160, all shown in their respective stowed configurations. Integrated assembly 72 contains, in addition to the secondary mirror 25 (not shown), UV exposure sources 90 (not shown) and reflective coating deposition sources 98 (not shown).
[0166] Additionally, telescope 52 comprises heating elements 55a, 55b and 55c used for deployment of primary mirror support 42, solar panels 180 (shown in their stowed configuration) and propulsion unit 150.
[0167]
[0168]
[0169]
[0170] An alternate telescope embodiment 50 is shown on
[0171]
[0172] Referring to
[0173] On
[0174] Alternatively, boom generator 135 can contain its own supply of boom material precursor and umbilical 132 would be used only to supply power.
[0175] Still alternatively, boom generator 135 can also contain its own power source in addition to the material precursor supply, in which case umbilical 132 is not required.
[0176] Referring to
[0177]
[0178] On
[0179] Alternatively, counterweight 152 can be ready-made and pre-installed in generator 137 to interface with boom 130 being subsequently formed.
[0180] Referring to
[0181] Deployable boom assembly 140 comprises several deployable elongated elements 165 coiled for their stowed configuration and periodically interconnected by snubber/stiffener elements 300. At its distal end boom assembly 140 contains a counterweight 152.
[0182]
[0183]
[0184] Referring to
[0185] Deployable boom assembly 190 comprises a plurality of nested telescopic elements extendable into a full-length boom by the action of compressed gas, chemically/pyrotechnically generated gas, thermally generated steam or due to action of shape-memory coiled actuator(s) contained within (not shown) which straighten upon being heated. At its distal end boom assembly 190 contains a counterweight 152.
[0186]
[0187]
[0188] Referring to
[0189] Deployable boom 192 comprises a coiled element preferably of shape memory material extendable into a full-length boom by application of heat. At its distal end boom 192 contains a counterweight 152. Alternatively, boom 190 can be is made out of a superelastic material and held in stowed configuration by removable/frangible/meltable constraining element(s) (not shown).
[0190]
[0191]
[0192] Referring to
[0193] Boom 193 comprises a folded shape memory rod which unfolds into a full-length elongated boom upon application of heat. At its distal end boom 193 contains a counterweight 152. Alternatively, boom 193 can be made from straight sections made with conventional materials, such as metal or fiber composite connected by shape memory or superelastic hinge elements (not shown). Alternatively, the hinges between straight sections can be spring-loaded.
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[0197] Referring to
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[0201] Referring to
[0202]
[0203]
[0204]
[0205] Telescope 68 comprising coiled support hoop 400 instead of folded hoop 420 would have a similar deployed configuration (not shown).
[0206]
[0207] Referring to
[0208] Tractor 138 is launched outwardly from telescope 64, extending boom 195 into its deployed configuration 195a and subsequently maintaining it under tension and assisting in the rotation of the telescope for its primary mirror generation by serving as a counterbalance.
[0209] As shown on
[0210] Tractor 138 can contain its own propellant, or can be fed with gaseous, steam or liquid propellant from main system enclosure 170 or integrated assembly 70 through boom 195a.
[0211] Alternatively, boom 195a can have more than one lumen and each lumen can be connected to its respective nozzle to impart the required momentum/tension vector to tractor 138.
[0212] Alternatively, tractor 138 can have remotely controlled valves operated via boom 195a by a controller located in main system enclosure 170 or being a part of the overall telescope control system.
[0213] Still alternatively, tractor 138 can have its own controller to effect maneuvering autonomously or semi-autonomously by controlled activation of nozzles 139. It can also be wirelessly controlled from system controller (not shown) located in system enclosure 170.
[0214] A pressurized propellant could be also delivered through boom 195a and then via the valves to nozzles 139. In case a liquid propellant is used, it can be expelled directly or made to decompose and generate propulsion gas or gasses. Two- or several component propellant (commonly known as hypergolic) can be mixed at the nozzles 139 to generate exhaust products.
[0215] Still alternatively, a steam generated by heating water can also be used as a propellant.
[0216] Alternatively, ion-or electro-hydrodynamic engines can be substituted for nozzles 139. These propulsion techniques and their respective propellants are well known in the art.
[0217]
[0218] As shown on
[0219] Depending on the stiffener material used, curing assembly can be implemented for UV-or thermal curing as shown on
[0220] If the stiffener material is a UV-curable epoxy, curing assembly 470 is made to contain one or more UV sources 474 located in housing 472.
[0221] In case thermoplastics or low melting metals or solders are being used for stiffener, curing assembly variant 470a contains an electro-magnetic induction coil 485 located in housing 473.
[0222] Alternatively, depending on the type of stiffener precursor materials used, infrared (IR) or microwave heating sources can be employed.
[0223] At its distal end boom 196a contains counterweight 152 to aid in telescope spinning maneuvers.
[0224] Alternatively, cable 196 can be pre-impregnated with stiffener material precursor prior to launch, such as a thermally- or UV-curable epoxy or low melting metal or alloy powder, thus removing the need for a coater.
[0225] The stiffener would be cured with curing assembly 470 or 470a, again, depending on the impregnating stiffening material used.
[0226] Optionally cable 196 can be over-coated with energy absorbing material or materials to dampen oscillations arising from maneuvers during telescope mirror's forming or aiming operations.
[0227] Additionally, the outer layer of cable 196 can be made of- or contain piezo-electric energy dissipating fibers or devices. These vibration energy absorbing techniques are known in their respective arts.
[0228] Referring to
[0229] De-spooling assemblies 222-222a comprise driven rollers with their associated drives. Rollers of de-spooling assemblies 222-222a have complementary concave-convex cross sections which match cross section profiles of 205 members. As members 205 emerge from de-spoolers 222-222a, they assume their deployed straight shapes 205a and pass through binder/snubber disks 302 via apertures 207 as shown on
[0230] Each disk 302 contains binding agent (not shown) inside its apertures 207 which binds it to members 205a when disk 302 is brought inside curing/heating assembly 480 by de-spooled members 205a and becomes permanently attached to them as 302a.
[0231] In addition to its primary function of binding together members 205a disk 302 can act as a snubber to reduce/eliminate any vibrations of boom 198 encounter during its deployment or primary mirror forming maneuvers. For this function, the binding agent used to attach disk 302 to members 205a can be a viscoelastic polymer, or the disk itself can be made to contain piezo-electric elements which would convert mechanical vibrations into electricity and then dissipate it.
[0232] Alternatively, binding agent can be dispensed before disc 302 enters assembly 480. Binding agent can comprise thermoplastic compound, UV-curable epoxy or low melting metal or alloy. By cycling operation of assembly 480 and coordinating it with operation of de-spoolers 222-222a, and disk 302 releasing mechanism (not shown), attached disks 302a are positioned along members 205a at controlled intervals along their length.
[0233] Curing/heating assembly 480 is equivalent to curing assembly 470 or 470a in its construction, which would depend on the binder agent, and material of 205 members and 302 disks.
[0234] Alternatively disks 302 can be made to be mechanically attached onto members 205a, for example by snapping them via a spring-loaded latching mechanism or an elastomeric insert. Disc securing features, such as depressions or notches can be incorporated into members 205 for this purpose at regular intervals and disks 302 can be made to have features interfacing with the corresponding locating/securing features of members 205.
[0235] Alternatively, depending on the materials utilized for disks 302 and members 205, disks 302 can be welded onto members 205 via arc or spot welding. The resulting boom comprising crossed members 205a and disks 302a is rigid in three dimensions.
[0236] Attached disks 302a, in addition to providing stiffness to the assembly can contain damping features which would eliminate or diminish vibrations of the boom 198 during its deployment and/or telescope maneuvers.
[0237] Still alternatively, two or more members 205 can be welded or glued together as they are de-spooled, either in a continuous seam or intermittently along their deployed length 205a.
[0238] The resulting boom comprising welded or glued crossed members 205a is rigid in three dimensions.
[0239] At its distal end boom 198 contains counterweight 152 to aid in telescope spinning maneuvers.
[0240] Shape-memory materials used in the instant mirror support construction may include shape-memory alloys (SMAs) or shape-memory polymers (SMPs).
[0241] Shape-memory alloys comprise numerous alloys such as AgCd, AuCd, cobalt-, copper-, iron-, nickel- and titanium-based, with most well-known and used being CuAlNi and NiTi alloys (the latter known as nitinols).
[0242] Shape-memory polymers comprise linear block polymers such as polyurethanes, polyurethanes with ionic or mesogenic components made by prepolymer method, block copolymer of polyethylene terephthalate (PET) and polyethyleneoxide (PEO), block copolymers containing polystyrene and poly(1,4-butadiene), and an ABA triblock copolymer made from poly(2-methyl-2-oxazoline) and polytetrahydrofuran.
[0243] Also, cross-linked PEO-PET block copolymers and PEEK can be used as shape-memory elements of instant invention.
[0244] Some of these SMPs can be made to contain carbon which makes them electrically conductive. This conductivity can be advantageous for their direct heating with electrical current of the mirror support and boom made from them.
[0245] Superelastic materials used in some of the telescope embodiments may be NiTi alloys, graphenes, thermoplastic elastomeric materials (known as TPEs in the art) and such.
TELESCOPE DEPLOYMENT AND OPERATION
[0246] The operation of the telescope is illustrated below primarily via examples of its 50a (direct imaging type) and 52a (Cassegrain type) variants. Alternative telescope variants follow similar procedures, unless described previously.
1. Struts Deployment
[0247] Referring to
[0248] On
[0249] An alternate heating mechanism of struts 160 is shown on
[0250] Shape memory materials preferably utilized for struts' 160 construction, particularly metallic Ni-based alloys are advantageously suited for direct heating by electric current as they possess high electrical resistivity.
2. Boom Generation or Deployment
[0251] An extendable boom is used as a counterweight for the telescope during its rotation. There are several embodiments of the boom, utilizing divers technologies.
[0252] To provide large radius of rotation to the telescope which influences the final shape of the formed mirror, and decrease its required rotational speeds and associated with it stresses on system components, the boom is made very long.
[0253] It is also made very slender, in order not to obscure the field of view of the mirror.
[0254] The cross section of the boom is preferably smaller than the diameter of the integrated assembly 70 or 72, as to minimize its obscuration of the object of interest.
[0255] The boom can be left in place after mirror generation, or it can be jettisoned after the mirror is made, as shown on
[0256] As an example of deployment of shape memory-based boom, referring to
[0257] Alternatively, boom 130 for example, can be 3-D printed.
[0258] Alternate boom configurations' deployment and/or generation has been described previously.
3. Mirror Support Deployment
3a. Rigid Mirror Support 40 or 42 Deployment
[0259] Referring to
[0260] Deployment of mirror support 40 or 42 is conducted preferably sequentially in stages starting from the outermost section by either passing electrical current from sources 210a, 210b and 210c directly through the support sections, as shown on
[0261] The outermost corrugation becomes side wall 46 of mirror support upon deployment.
[0262] The controlled sequential deployment of sections of mirror support is preferable as it minimizes the physical size of the heating systems, because the required connections remain close to the center of the support while the support assumes its (greatly enlarged) deployed shape.
3b Pliable Mirror Support 450 Deployment
[0263] Referring to
[0264] At its fabrication, support hoop 400 or 420 is trained into a circular form 400a or 420a, respectively, to set its memorized shape. Afterwards, it is either coiled or folded into a compact pre-deployment shape 400 or 420, respectively.
[0265] Shape memory materials preferably utilized for support hoops' 400 or 420 construction, such as metallic Ni-based alloys are advantageously suited for direct heating by electric current, as they possess high electrical resistivity.
4. Mirror Generation Process
4a Spinning the Telescope in Two Orthogonal Axes
[0266] Referring to
[0267] Rotation around the telescope's Y-axis creates a centripetal force analogous to the gravitational force on the Earth's surface. Rotation around the telescope's Z-axis creates its own centripetal force which distributes liquid mirror precursor material 60 inside deployed mirror support 42a. The cooperative action of these two forces creates a paraboloid mirror surface.
[0268] The focal length of the resulting mirror can be calculated from the following equation (2).
[0269] Where [0270] f is the focus length of the resulting paraboloid mirror [0271] R.sub.CM is the radius of rotation around telescope center of mass [0272] .sub.Y is angular velocity around telescope's Y-axis [0273] .sub.Z is angular velocity around telescope's Z-axis
[0274] The Coriolis' force contribution and liquid surface tension of mirror material 60, while would be present, to a first approximation are not included in this analysis. It is expected that the Coriolis' force will effectively tilt the center line of the created paraboloid. This tilt is predictable and ascertainable from the system operation parameters and will be readily compensated for by the mechanical design of the mirror support and downstream optical system design.
[0275] It is worth noticing that the focal length of the resulting mirror does not depend on the absolute magnitudes of the orthogonal rotational velocities but rather on their ratio.
[0276] Thus, a mirror of a given focal length can be formed with an infinite variety of orthogonal rotational velocities, including very low ones, as long as their ratio remains the same.
[0277] At lower rotational velocities the forces acting on rotating components are also lower as well, as are the resulting stresses on the system. With lower stresses on them, the system components can be made thinner and lighter.
[0278] Proper selection of the mirror material 60 and intrinsic material or surface treatment or coating of support 40a or 42a would ensure its proper wetting by material 60.
[0279] The spinning of the telescope is effected by propulsion unit 150 utilizing reactive propulsion with liquid, hot gaseous propellants (mono- and hypergolic), compressed (cold) gas jets, chemical gas generators, ion engines, and such.
[0280] The spinning of the telescope can be further controlled/assisted by tractor 138 of telescope variant 64 maintaining tension on deployed pliable boom 195a and potentially additionally applying a rotating vector to the telescope.
[0281] Alternatively, as an example, for telescope variant 52b shown on
[0282] Rotation can also be effected for example by the deployed boom 195a on
4b. Mirror Precursor Dispensing
[0283] Mirror precursor can be deposited and held in the liquid state in the mirror support prior to deployment. Alternatively, it can be liquefied prior to mirror generation.
[0284] Still alternatively, referring to
[0285] As shown on
[0286] As shown on
[0287] Referring to
[0288] A frusto-conical light baffle 47 and side wall 46 prevent precursor 60 from spilling into aperture 28a and spilling out of support 42a, respectively.
[0289] Piston 65 for expelling precursor 60 from volume 34 can be actuated by a spring, a shape memory actuator, compressed gas, an electro-mechanical drive, a pyrotechnic gas generator, and the like. Actuators of these types are well known in the art.
[0290] Assembly 30c further contains aperture 28a through which imager system 80 receives light from secondary mirror 25. Additionally, assembly 30c, if required, can contain an annular heater element similar to heater 68 to heat/melt mirror precursor material prior to deposition.
5. Solidification of Mirror Precursor Material
5a.
[0291] In case of liquid mercury, molten metals or polymers, two part epoxies or thermosetting polymers used as precursor, liquid mirror material 60 is then permitted to cool/polymerize and solidify, at which point the rotation of the telescope can be stopped.
[0292] The cooling rate of material 60 may have to be controlled for a particular mirror material, for example a flash cooling to create an amorphous metal glass with superior surface quality.
[0293] Metals and alloys with low melting temperature include sodium (Na), potassium (K), indium (In), gadolinium (Ga), tin (Sn), lead (Pb) and mercury (Hg) as well as various alloys of these metals.
[0294] Thermo-setting polymers are also suitable, such as polyesters, phenolic resins, vinyl esters, polyurethane; silicones, polyamides, polyamide-imides, and others.
[0295] Thermoplastic polymers such as polypropylene, polyethylene, polyvinylchloride, polystyrene, polyethylenetheraphthalate and polycarbonate and others can be also be used.
5b. Curing of Photopolymer Precursor Material
[0296] In case of a photopolymer precursor being used, liquid mirror material 60 is cured by exposure to ultraviolet (UV) light supplied by UV light source or sources 90 located in assembly 70 or 72. Most of UV-curable materials require UV irradiation in the 240-405 nm wavelength range. Such illumination is achievable with UV light-emitting diodes (LEDs), vapor-discharge lamps, or lasers. Such LEDs are commercially available. For example, UV LED Model 6868 by Inolux Company (San Jose, California, USA) produces 10 Watts of optical output at 365 nm wavelength while occupying a relatively small 6.86.83.7 mm.sup.3 envelope suitable for compact co-location of many such LEDs for a powerful precursor curing solution which would be capable of reliable and fast curing of photopolymer precursor.
[0297] Photopolymers are widely used in industry as potting and adhesive compounds. Commonly used photopolymer materials comprise cycloaliphatic epoxies, cyanoacrylates and such. For example, UV-curable polymer Model UV18Med by Master Bond Corporation (Hackensack, New Jersey, USA) is cured by exposure to 320-365 nm UV light source, does not contain or create volatile compounds and has an exceptionally low shrinkage upon curing. Another example is a UV22 nanosilica-filled UV-curable photopolymer system by Master Bond, Inc. which has high dimensional stability, very low thermal expansion coefficient and meets NASA low outgassing requirements for use in vacuum of space, thus making it suitable for the instant application.
[0298] UV-curable polymers can also be cured with ionizing radiation, such as, for example gamma rays emitted by Cobalt-60 (.sup.60Co).
[0299] Some UV-curable photopolymers benefit from being post-cured with heat. Heat can be provided by infrared (IR) or microwave sources installed for his purpose in assembly 70 or 72.
6. Reflective Coating(s) Deposition
6a.
[0300] Metallic precursor materials intrinsically possess high reflectivity and do not generally require reflective coatings.
6b.
[0301] In contrast, since cured photopolymers, two-part epoxies or thermoset or thermoplastic polymers do not generally possess high intrinsic reflectivity, or are transparent/translucent, they have to be coated with metallic or dielectric reflective films after the mirror is solidified.
[0302] Referring to
[0303] Alternatively, instead of direct heating of material sample 320 by heater 260, it can be heated and vaporized with an electron beam or a laser beam, as is known in the art.
[0304] While providing momentum to the coating particles via accelerating voltage also helps to keep their stream pointed onto the mirror surface and minimize or eliminate its spillover and possible contamination of the adjacent telescope structures. Any coating particles not intercepted by mirror support 40a or 42a or 450a will be launched into space and away from telescope due to their acquired momentum.
[0305] To further prevent coating materials from settling onto-and potentially contaminating the nearby imager system 24, source(s) 98 can be recessed with respect to the coater output openings 99 as shown on
[0306] Several sources 98 may contain different materials and their respective deposition can be independently controlled, simultaneously or sequentially, to effect, for example, a multi-layer coatings.
[0307] The coating materials can comprise metals, for example gold (Au), silver (Ag) or aluminum (Al), or dielectric materials such as SiO.sub.2, Si.sub.3N.sub.4, CaF.sub.2, GeO.sub.2, MgF.sub.2, Al.sub.2O.sub.3. High reflectivity multilayer coatings utilizing these and similar materials are well known in the art.
[0308] For example, high reflectivity multilayer coatings are customarily made with alternating layers of materials with low refractive indices such as magnesium fluoride (MgF.sub.2) and silicon dioxide (SiO.sub.2) and materials with large refractive indices, such as zinc sulfide (ZnS) and titanium dioxide (TiO.sub.2). For high reflectivity in extreme ultra-violet (EUV) alternating layers of molybdenum (Mo) or tungsten (W) can be interposed with lightweight materials such as silicon (Si).
[0309] Since the mirror operates exclusively in the deep vacuum of space, chemically reactive materials otherwise unsuitable for terrestrial applications, such as alkali metals, may also be readily used for coatings. Advantageously, some alkali metals such as potassium (K) have unique reflectance properties which can be advantageously exploited in space environment.
7. Imaging
7a. Imaging by Direct Imaging Telescope
[0310] Direct telescope imaging is effected by direct imager system 24 located in integrated assembly 70 shown on
[0311] Imager system 24 captures image created by telescope's primary mirror and provides it in electronic form for downstream post-processing. System 24 may contain several distinct optical instruments (not shown in detail) as is frequent for space imaging systems.
[0312] Assembly 70, comprises enclosure 92 which, in addition to imager system 24 contains integrated controller 77, UV curing sources 90 and coating deposition sources 98. Controller 77 may contain image post-processing and transport hardware in addition to sub-controllers for curing sources 90 and coating deposition sources 98.
7b. Imaging by Cassegrain-Type Telescope
[0313] For the Cassegrain-type telescope configuration 52a secondary convex mirror 25 located in integrated assembly 72 conveys light reflected by the primary mirror to imager system 80 located in main system enclosure 170.
[0314] Referring to
[0315] System 80 may contain several distinct optical instruments (not shown in detail) as is frequent for space imaging systems.
[0316] Integrated assembly 72 shown on
8. Mirror Support Deployment and Surface Creation Operations Sequences
[0317] Referring to
[0318] Struts 160 are extended by activating voltage source 210 (step 610), passing electric current directly through struts 160, heating them above their material's transition temperature and extending them into their deployed configuration 160a.
[0319] Heater 55a is activated (step 620) and distal corrugated portion of mirror support 40 or 42 extends outwardly with the outermost fold forming a side wall 46.
[0320] Subsequently, heaters 55b and 55c are sequentially activated (in steps 630 and 640, respectively) which causes middle-and proximal corrugations of support 40 or 42 respectively to extend, and the entire support to assume its deployed configuration 40a or 42a.
[0321] Referring to
[0322] Struts 160 are extended by activating voltage source 210 (step 610a), passing electric current directly through struts 160, heating them above their material's transition temperature and extending them into their deployed configuration 160a.
[0323] Voltage source 210a is activated (step 620a) and heats up distal corrugated portion of mirror support 40 or 42 which as a result extends outwardly with the outermost fold forming side wall 46.
[0324] Subsequently, voltage sources 210b and 210c are sequentially activated (in steps 630a and 640a, respectively) which causes middle-and proximal corrugations of support 40 or 42 respectively to heat and extend, and the entire support to assume its deployed configuration 40a or 42a.
[0325] Referring to
[0326] Subsequently, boom 120a or 130a or 140a or 190a or 192a or 193a or 195a or 198 is deployed or formed (step 715).
[0327] Mirror support 40 or 42 is then deployed and assumes its deployed respective configuration 40a or 42a as described previously (step 720).
[0328] Telescope is then spun around two orthogonal axes (step 730).
[0329] Photopolymer precursor material 60 is then dispensed into support 40a or 42a (step 740) and, still in liquid state, creates a paraboloid surface due to telescope spinning action.
[0330] Precursor 60 is then cured into solid paraboloid form by its exposure to UV light(s) 90 (step 750). Steps 740 and 750 may be repeated to build up the mirror thickness, without stopping rotation of the telescope.
[0331] In case of a meltable precursor 60, it is first melted and then dispensed in step 740a bypassing UV curing step 750.
[0332] After precursor 60 solidified, coating material heater(s) 260 of integrated assembly 70 or 72 are turned on causing melting and/or vaporization of coating material(s) 320 (step 760).
[0333] Subsequently high voltage source(s) 250 is activated which applies high voltage to accelerating grid(s) 280 of integrated assembly 70 or 72 which ionizes and propels coating ions toward the mirror surface.
[0334] After coating deposition is finished (by, for example, monitoring reflectivity of the mirror by a probe beam), coating operation is complete.
[0335] If precursor 60 has high native reflectivity (for example being a metal), the coating steps 760 and 770 can be omitted.
[0336] After the mirror has been formed and coated, the boom can be optionally jettisoned in step 780.
ADDITIONAL SYSTEM COMPONENTS IMPLEMENTATIONS AND PROCCESS SEQUENCES
Pliable Mirror Support 450 Deployment
[0337]
[0338] Voltage source 210 is activated (step 810) and heats up struts 162 which assume their deployed configuration 162a (step 820).
[0339] Voltage source 220 is then activated (step 830) and directly heats coiled hoop 400 by passing electric current through it. As a result, hoop 400 assumes its deployed circular configuration 400a (step 840). Alternatively, if folded hoop 420 is used instead, source 220 heats it up and it assumes its respective circular shape 420a (step 850).
Mirror Support Hoop Super-Elastic Variants and Their Deployment
[0340] Mirror support hoop 400 or 420 can be made self-opening by exploiting the super-elastic properties of shape-memory materials, such as, for example NiTi (nitinol) alloys. At above their phase-transition temperatures such alloys exhibit super-elastic properties which are characterized by very large elastic coefficients: the items made from them after removal of constraint return to their original shape even after being greatly deformed.
[0341] Mirror support hoop 401 or 421 made from these materials and operated in its super-elastic mode (vs. temperature-sensitive shape-memory mode), unfold on its own in space into its deployed shape 401a or 420a once released, after being compressed into-and held in its respective stowed configurations.
[0342] Referring to
[0343] A circular thermal cutter 407 is positioned on sleeve 405 along its circumference. Upon being heated by electrical current supplied by source 221, cutter 407 thermally cuts through sleeve 405 which opens up, releasing hoop 401 which assumes its deployed configuration 401a. This deployment mechanism is well known in the art.
[0344] Referring to
[0345]
[0346] Alternatively, if folded superelastic mirror support 421 is used, steps 830a and 850a are substituted by steps 860a and 870a, where thermal cutter 413 cuts through retaining cord 411 releasing superelastic folded hoop 421 which assumes its deployed circular configuration 421a, respectively.
Mirror Performance Testing, Calibration and Repair
[0347] To verify mirror shape and to test its alignment and surface quality telescope is oriented to point towards a bright star, which can serve as a virtually ideal point light source.
[0348] By analyzing the shape and size of the image of the star the surface quality of the mirror, its shape and alignment can be ascertained. By utilizing the results of these measurements the subsequent images produced by the imager system 24 can be optically or digitally corrected if required. The calibration and verification can be repeated periodically throughout the service life of the telescope if there is a suspicion that the mirror shape and alignment have somehow changed.
[0349] If the mirror has been damaged, deformed, its surface has aged, or if there was a defect produced during its generation, it can potentially be over-cast with a new layer of liquid precursor. To re-cast the mirror surface with a molten or mixed precursor, the precursor material melting or mixing, casting and coating (if required) operations will be repeated and telescope be re-spun. The entire mirror can be heated for the material to melt, or a new batch of the mixed or molten precursor material deposited onto the existing material layer. In the former case, mirror support 40a or 42a will have to contain a heater or heaters.
[0350] To overcoat the mirror an additional batch of liquid mirror precursor is dispensed onto the previously solidified mirror surface 64. Telescope is then re-spun to spread precursor material and for it to form new paraboloid surface 64, and then the precursor is allowed to cool and solidify, or, in case of a photopolymer 60 used, it is again cured with UV light source(s) 90 and coated as previously. This operation will necessitate an additional capacity of the precursor material holding tank 30 and its variants, or additional precursor holding tanks, or a controlled dispensing action of material expelling piston 65 which will not dispense the entire volume of precursor 60 in the first mirror forming operation, but will preserve some for potential re-casting operations. A dedicated heater in addition to heater 63 may be required to maintain precursor 60 in liquid form, or to heat/thaw it prior to dispensing.
Precursor Material Variants
[0351] Numerous precursor material variants are suitable for generating the mirror, such as: [0352] a. alkali metals, [0353] b. aluminum, [0354] c. mercury, [0355] d. metals and alloys thereof, [0356] e. metal glasses and alloys thereof, [0357] f. epoxies and mixtures thereof, [0358] g. epoxies containing thermal expansion coefficient-reducing additives, [0359] h. thermoplastic polymers and mixtures thereof, [0360] i. thermoplastic polymers containing thermal expansion coefficient-reducing additives, [0361] j. thermosetting polymers and mixtures thereof, [0362] k. thermosetting polymers containing thermal expansion coefficient-reducing additives, [0363] l. glasses and mixtures thereof, [0364] m. pitch and mixtures thereof, [0365] n. sugar solutions, [0366] o. aqueous solutions and [0367] p. photocurable polymers and mixtures thereof. [0368] q. photopolymers containing thermal expansion coefficient-reducing additives, [0369] r. cycloaliphatic epoxies and mixtures thereof, [0370] s. cyanoacrylates and mixtures thereof [0371] t. styrenic compounds, [0372] u. vinyl ethers, [0373] v. N-vinyl carbazoles, [0374] w. lactones, [0375] x. lactams, [0376] y. cyclic ethers, [0377] z. cyclic acetals, [0378] aa. cyclic siloxanes, [0379] bb. phthalic diglycol diacrylates,
Precursor Container Variants
[0380] Several variants of container system 30 for the mirror precursor material 60 are presented on
[0381] Precursor container variant 30a in addition comprises heater 63 to melt material 60. This container can be used with material 60 which would be solid or excessively viscous during launch. Piston 65 used to expel precursor can be actuated with a pre-compressed spring, a shape-memory type actuator, electrical motor driving a screw-type actuator assembly or an eccentric, compressed gas, or with a pyrotechnic gas generator.
[0382] Precursor container variant 30c is made annular and comprises central aperture 28a through which imaging can take place.
Heat Pipe Implementations for Shape Memory Components
[0383] Utilizing heat pipe technology facilitates fast heating and subsequent deployment of shape-memory components since their heating does not rely on a relatively slow heat diffusion phenomenon or direct heating with electric current, but rather employs a heating source only at the proximal end of the part.
[0384] Using heat pipe technology also simplifies overall system design by removing the necessity to provide electrical connections on both (proximal and distal) ends of deploying components if their direct electrical heating is employed.
[0385] Mirror supports 40 and 42, struts 160, corrugated boom 150, coiled boom 190, coiled boom elements 165 and support hoops 400 and 420 can all be realized as heat pipes rather than solid parts.
[0386] For example, a heat pipe variant 164 of strut is shown in cross section on
[0387]
Strut Variants
[0388] Additionally, struts 160 can be formed to transform from cylindrical cross section into a T(160b), an I(160c) or a Y(160d) cross sections upon heating and deployment, as shown on
[0389] Similarly, as shown on
[0390] Additionally struts 160 and 162 can be 3-D printed or extruded, similarly, for example to boom 130.
System Components Superelastic Implementations
[0391] Most of the shape memory-based system components can be implemented in their superelastic variants. Above their transition temperature, shape memory materials behave superelastically, so, for example the NiTi alloys similar to shape memory types (albeit having different stoichiometry) can be used for superelastic components.
[0392] For example, mirror supports 40 and 42 can be made from superelastic materials, folded/compressed and mechanically constrained prior to deployment, and deploy spontaneously into their original shape when the constraints are removed.
[0393] Similarly, struts 160 and 162 can be made superelastic, as well as some booms, for example 120, 140, 192 and 193.
Deployment Speed Retarders and Vibration Dampers Use
[0394] Due to the boom's high length-to-diameter aspect ratio, during its own deployment or forming and mirror forming and potentially aiming maneuvers it is expected to experience various vibrational and twisting moments.
[0395] In the vacuum of space and depending on the mechanical losses of the boom structure these moments can generate persistent oscillations unless controlled.
[0396] This is particularly important for superelastic-type deployable elements which may store significant mechanical potential energy, in order to achieve their soft deployment and avoid large oscillations and/or vibration.
[0397] Therefore, retarding, deployment speed-controlling and energy dissipating devices and structures in addition to, for example 300 used in boom variant 140, and binder/snubber disks 302 of boom 198 are proposed as well.
[0398] For this function, the binding agent used to attach disk 302 to members 205a can be a viscoelastic polymer, or the disk itself can be made to contain piezo-electric elements which would convert mechanical vibrations into electrical charges and then dissipate them.
[0399] Piezo-electric or mechanically dampening coatings or laminates or embedded (in case of members 205, for example) are possible. Additionally, the outer layer of cable 196 can be made of-or contain piezo-electric energy dissipating fibers or devices. These vibration energy absorbing techniques are known in their respective arts.
[0400] Alternatively, magnetic-type dampers utilizing eddy currents can be used. For example, a permanent magnet surrounding a conductive rod (for example, strut 160) would induce eddy currents when the rod is moving inside the magnet's field, generating opposing e.m.f., reducing movement and would eventually dissipate energy via ohmic losses. Such devices are known in the art and are operational at cryogenic temperatures encountered in space.
Precursor Curing Source Variants.
[0401] Curing light sources 90 do not have to produce just an ultraviolet light in order to cure precursor 60, but visible or even infrared light can be used instead of-or in conjunction with, UV. Some photopolymers can be cured by visible light, as described in U.S. Pat. No. 9,902,860 to Li et al., or even by either UV or IR radiation per U.S. Pat. No. 5,466,557 to Haley et al. Yet other photopolymers are best cured by a combination of UV exposure followed by thermal/IR post-curing.
[0402] Alternatively, heating and curing of the precursor can be done with microwaves. Since sun's radiation emission spectrum peaks in the violet, UV-curable precursor photopolymers can be exposed to sunlight for curing, either as a backup to the UV sources, or the precursor primary curing mechanism. This is advantageous for large and very large mirrors for which large and very powerful UV light sources may be challenging to implement.
[0403] Additionally, cross-linking of precursor polymeric material(s) can be accomplished by exposing them to other types of radiation, such as for example, of ionizing type.
[0404] To that extend, to enable fast cure of epoxy-type precursors of both photo-curable and two-part types, and enable their curing even in very thick cross sections, ionizing radiation source(s) can be used.
[0405] For example, a Cobalt-60 (.sup.60Co) gamma-ray source would fast cure/crosslink epoxies at significant layer thicknesses. An alternative gamma-ray source could be Iridium-192 (.sup.192Ir).
[0406] There is also a number of other radioactive gamma emitters that have a very wide range of half-lives and photon energies that can be selected for a particular mission.
[0407] The use of such sources for curing/cross-linking epoxies and polymers is known in the art.
[0408] Because high energy gamma rays such as created by Cobalt-60 readily penetrate metals, the gamma ray source can be contained in the main system enclosure and pointed outwards, through mirror support, to illuminate and cross link mirror material precursor from below.
[0409] Mirror support 40a or 42a may be made reflective on its both surfaces to minimize heating by sunlight and minimizing the resulting heat-induced stress in the formed mirror.
[0410] Alternatively, it can have a thermally absorbent coating on its obverse surface, to facilitate melting of solid precursors by the sun.
[0411] Dispensing of liquid precursor photopolymers may proceed in several successive stages, to enable curing of a single layer at a time, if required.
[0412] Composition of the deposited precursor layers can be made to vary by pre-filling precursors in the precursor container in a particular sequence or by employing several precursor material dispensers in sequence.
[0413] While described reflective coating deposition process uses vaporized material deposition, other ways of depositing reflective and protective coatings can be used for the mirror. For example, there exists a well-known material sputtering process. Additionally, chemical metals deposition techniques exist, such as electro-less nickel, tin and copper deposition processes.
Additional System Features
[0414] 1. While precursor material is dispensed from container assembly 30 at the center of mirror support 40, the dispensing can be conducted from elsewhere as well, for example at the periphery of support 40, or 42, or 450.
[0415] To accomplish the filling of the mirror support the rotation of telescope has to be controlled, for example, by initially spinning the telescope around the Y-axis with angular velocity .sub.Y and generating artificial gravity as shown on
[0422] Although descriptions provided above contain many specific details, they should not be construed as limiting the scope of the present invention.
[0423] All features disclosed in the specification, including the claims, abstract, and drawings, and all the steps in any method or process disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
[0424] Each feature disclosed in the specification, including the claims, abstract, and drawings can be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise.
[0425] Thus, the scope of this invention should be determined from the appended claims and their legal equivalents.