This invention relates generally to the electrospray emission field, and more specifically to a new and useful system and method in the electrospray emission field.
The following description of the preferred embodiments of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention.
As shown in
The apparatus 10 preferably functions to produce ions (and/or charged droplets) from working material (e.g., working fluid, propellant, etc.), where the ions can be used to generate thrust (e.g., with high efficiency, high thrust density, high specific impulse, etc.) and/or can otherwise be used or analyzed. For example, the apparatus can be mounted to and/or included in a spacecraft (e.g., a satellite such as a CubeSat, U-class spacecraft, picosatellite, nanosatellite, microsatellite, minisatellite, ESPA-class spacecraft, geostationary spacecraft, 1-kg, 10-kg, 50-kg, 100-kg, 500-kg, 1000-kg, 2000-kg, etc.; Space Shuttle; interplanetary probes; extra-solar probes; etc.). However, the apparatus can additionally and/or alternatively be used in biomedical field (e.g., to dose a working material in an injection needle), in electrospray devices (e.g., for electrospray ionization, for electrospray mass spectrometery, etc.), and/or any other suitable field.
Variations of the technology can confer several benefits and/or advantages.
First, the inventors have discovered that reactions (e.g., chemical reactions, electrical reactions, etc.) between an electrically conductive surface (e.g., an electrode, a frame, etc.) and working material can shorten a lifetime of and/or degrade performance of an electrospray device. For instance, an electrospray device may only operate at a desired performance for a time scale on the order of days, weeks, months, etc.; whereas a desired operation time scale (e.g., attaining a desired performance) is typically longer (e.g., weeks, months, years, decades, etc.). The inventors have discovered that, in some variants of the apparatus, coating electrically conductive surfaces (particularly, but not exclusively, electrically conductive surfaces that incidentally or intentionally contact working material) with a dielectric, manufacturing or forming the surfaces from dielectric materials, and/or otherwise mitigating the impact of incidental contact between working material and a surface can enable an apparatus to have a longer lifetime (e.g., while maintaining at least a threshold performance such as a target impulse, target thrust, target specific impulse, etc.) relative to apparatuses that do not include the dielectric (e.g., dielectric coating) or other mitigation strategies or materials.
Second, variants of the technology can undergo shorting between an emitter array and an electrode, which can lead to degradation and/or failure in other emitter arrays and/or electrodes. Examples of the apparatus can mitigate (e.g., diminish the impact of, plan for, account for, etc.) the effect of this shorting by coupling the electrode to a (shared) ground plane through balancing electronics (e.g., a high impendence resistor).
Third, variants of the apparatus can decrease (e.g., decrease, mitigate, avoid, reduce a probability of, etc.) an impact of (e.g., performance deviation, system instability, efficiency decrease, change in system operation, impact to apparatus lifetime, etc. to one or more electrodes or apparatuses as a whole) a shorting event (such as can occur when working material contacts an electrode with different electric potential) on an electrode. For example, a high impedance resistor between each electrode and a common power supply can reduce the current passed through an electrode during a shorting event. High impedance resistors can provide a technical advantage of passively reducing an effective emission voltage for devices which have higher extractor current than others, thereby balancing the beam-emitted current of devices operating in parallel.
However, variants of the technology can confer any other suitable benefits and/or advantages.
As used herein, “substantially” or other words of approximation (e.g., “about,” “approximately,” etc.) can be within a predetermined error threshold or tolerance of a metric (e.g., a manufacturing tolerance), component, or other reference (e.g., within 0.001%, 0.01%, 0.1%, 1%, 5%, 10%, 20%, 30%, etc. of a reference), or be otherwise interpreted.
As shown in
The emitter array 100 preferably functions to emit (e.g., eject, release, disperse, etc.) working material. The emitter array preferably includes a plurality of emitters, but can include a single emitter, non-emitting structures, and/or any suitable emitters. The emitter array is preferably in fluid communication with a reservoir 180 (e.g., a reservoir or working material management system as disclosed in U.S. patent application Ser. No. 17/410,157 titled ‘PROPELLANT APPARATUS’ filed on 24 Aug. 2021 which is incorporated in its entirety by this reference; via a manifold, propellant management device, etc.; etc.) and/or other working fluid source, but can be arranged in any manner. The emitter array is preferably aligned to an electrode (e.g., an extractor electrode as shown for example in
The working material 15 preferably functions to provide a solution of ions (e.g., cations, anions) that can be used to generate thrust, but can additionally or alternatively include a material to be analyzed and/or that can perform any other suitable function. The working material is preferably an ionic liquid (e.g., an ionic compound such as an anion bound to a cation that is liquid at temperature T<100° C.). However, additionally or alternatively, the working material can include a monopropellant (e.g., hydroxylammonium nitrate (HAN), ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), ammonium nitrate (AN), hydrazinium nitrate (HN), Advanced Spacecraft Energetic Non-Toxic (ASCENT) propellant, etc. optionally associated with one or more ionic or molecular fuel such as tris(ethano) ammonium nitrate (TEAN), ammonium azide (AA), hydrazinium azide (HA), 2-hydroxyethylhydrazinium nitrate, methanol, ethanol, glycerol, glycine, urea, etc.), a room temperature ionic solid (RTIS), an electrically conductive fluid, a high temperature ionic liquid (e.g., an ionic liquid that is liquid at T>100° C.), and/or any other suitable material. The ionic liquid is preferably imidazolium based (e.g., includes derivatized imidazolium ions such as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-Tf2N), 1-ethyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide (EMIM-Beti), etc.); however, any suitable ionic liquid(s) (or class thereof) can be used.
Emitters 150 of the emitter array 100 can be capillary emitters (e.g., an emitter or array thereof as disclosed in U.S. patent application Ser. No. 17/216,425 titled ‘APPARATUS FOR ELECTROSPRAY EMISSION’ filed on 29 Mar. 2021, which is incorporated in its entirety by this reference), porous emitters (e.g., an emitter or array thereof as disclosed in U.S. patent application Ser. No. 16/879,540 titled ‘APPARATUS FOR ELECTROSPRAY EMISSION’ filed on 20 May 2020 or U.S. patent application Ser. No. 16/511,067 titled ‘METHOD AND APPARATUS FOR A POROUS ELECTROSPRAY EMITTER’ filed on 15 Jul. 2019, U.S. patent application Ser. No. 16/511,067 titled ‘METHOD AND APPARATUS FOR A POROUS ELECTROSPRAY EMITTER’ filed 15 Jul. 2019, U.S. Pat. No. 8,791,411 titled ‘METHOD AND APPARATUS FOR A POROUS ELECTROSPRAY EMITTER’ filed 15 Mar. 2013, U.S. Pat. No. 8,324,593 titled ‘METHOD AND APPARATUS FORA POROUS METAL ELECTROSPRAY EMITTER’ filed 6 May 2009, U.S. Pat. No. 8,030,621 titled ‘FOCUSED ION BEAM FIELD SOURCE’ filed 15 Oct. 2008, U.S. Pat. No. 7,863,581 titled ‘FOCUSED NEGATIVE ION BEAM FIELD SOURCE’ filed 9 Jun. 2008, each of which is incorporated in its entirety by this reference), surface emitters (e.g., guard emitters), non-capillary emitters, and/or any suitable emitters.
In an illustrative example, an emitter array can include a plurality of emitter combs (e.g., where teeth of the comb act as emission sites). In this example, the teeth of a comb (e.g., an apex separation) can be between about 10-1000 μm (e.g., 10, 20, 25, 30, 40, 50, 60, 70, 75, 80, 90, 100, 200, 300, 500, 750, 1000 μm, values or ranges therebetween, etc.) and each comb can be separated by between about 100 and 1000 μm (e.g., 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 m, 650 μm, 700 μm, 750 μm, 800 μm, 850 μm, 900 μm, 950 μm, 100 μm, values or ranges therebetween, etc.). A comb length can be between about 1 mm and 100 mm (e.g., 1 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 7.5 mm, 8 mm, 9 mm, 10 mm, 20 mm, 40 mm, 50 mm, 60 mm, 80 mm, 100 mm, values or ranges therebetween, etc.). An emitter array extent can be between about 1 mm and 100 mm (e.g., 1 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 7.5 mm, 8 mm, 9 mm, 10 mm, 20 mm, 40 mm, 50 mm, 60 mm, 80 mm, 100 mm, values or ranges therebetween, etc.). In variations of the first specific example, the emission sites can be separated sites (e.g., individual cones, capillary emitters, etc.). In a second specific example, the emitter array can include a hexagonal grid of emitters (e.g., cone emitters, cylindrical emitters, porous emitters, capillary emitters, etc.), where a separation between emitters can be between about 10-1000 μm (e.g., 10, 20, 25, 30 ,40, 50, 60, 70, 75, 80, 90, 100, 200, 300, 500, 750, 1000 μm, values or ranges therebetween, etc.).
The apparatus can include a plurality of emitter arrays. Each emitter array can be electrically isolated from other emitter arrays, can be in electric communication with other emitter arrays (e.g., a first subset of emitter arrays or working material associated therewith can be maintained at a first electric potential and a second subset of emitter arrays or working material associated therewith can be maintained at a second electric potential), and/or otherwise have any suitable electrical properties. The emitter arrays can be fed by a common reservoir, sets of emitter arrays can share a reservoir, can each be associated with a reservoir, and/or can otherwise be associated with a reservoir or working material source.
The emitter array (and/or reservoir, manifold, etc.) can include (e.g., be in electrical communication with) an electrode (e.g., a working electrode), which can function to set or maintain an electrical potential of working material within or emitted from the emitter array(s).
The emitter array (and/or working material thereof) is preferably in electrical communication with an electrode (e.g., distal electrode) which functions to maintain the working material at an electric potential. The distal electrode can be arranged within the emitter array, within a reservoir, within a manifold connecting a reservoir to the emitter array (e.g., by including a conductive material such as silicon black or a carbon xerogel in the manifold), and/or can otherwise be arranged. The distal electrode is preferably in electrical communication with a power supply (optionally via balancing electronics). The distal electrode preferably has a large surface area (e.g., a specific surface area that is at least 100 m2cm−3, 200 m2cm−3, 300 m2cm−3, 400 m2cm−3, 500 m2cm−3, 600 m2cm−3, 650 m2cm−3, 700 m2cm−3, 800 m2cm−3, 900 m2cm−3, 1000 m2cm−3, 2000 M2cm−3, 3000 m2cm−3, 4000 m2cm−3, 5000 m2cm−3, 6000 m2cm−3, 7000 m2cm−3, 8000 m2cm−3, 9000 m2cm−3, 1000 m2cm−3, values therebetween, >10000 m2cm−3, etcl; at least 100 m2g−1, 200 m2g−1, 300 m2g−1, 400 m2g−1, 500 m2g−1, 600 m2g−1, 650 m2g−1, 700 m2g−1, 800 m2g−1, 900 m2g−1, 1000 m2g−1, 2000 m2g−1, 3000 m2g−1, 4000 m2g−1, 5000 m2g−1, 6000 m2g−1, 7000 m2g−1,8000 m2g−1, 9000 m2g−1, 10000 m2g−1, values therebetween, >10000 m2g−1, etc.; etc.), which can help decrease the likelihood of an electrochemical reaction at the distal electrode. However, the distal electrode can have a low surface area (e.g., less than 100 m2cm−3, less than 100 m2g−1, etc.; for instance when a high volume or higher mass electrode is used) and/or any suitable surface area.
The frame 200 preferably functions to align the emitter array (and/or emitters thereof) to the electrode (e.g., extractor electrode) such as to align emitters (and/or emission of working material therefrom) to openings in the electrode, to provide support for the emitter array and/or electrode, to maintain a separation distance between the emitter array and the electrode, to isolate (e.g., mechanically, electrically, from high energy particles, etc.) the emitter array and/or electrode (e.g., from an external environment), and/or can otherwise function. The frame preferably surrounds the emitter array (as shown for example in
The frame can have a square, rectangle, polygon, circle, oval, elliptical, and/or have any suitable cross-section (e.g., cross-section through a plane perpendicular to a working material emission axis, cross-section for an opening where an emitter array and/or electrode is supported, cross-section through a plane parallel to a working material emission axis, etc.). In a first specific example, a frame can have a square cross-section and support a single emitter array and associated electrode. In a second specific example, a frame can have a rectangular cross-section and support four emitter arrays and four associated electrodes. However, a frame can have any suitable shape and support any suitable number of emitter arrays and/or electrodes.
The frame can include (e.g., be made from) electrically conductive materials (e.g., silicon, metals such as gold, alloys, etc.), dielectric materials (e.g., polymers, rubbers, glasses, ceramics, as shown for example in
In some variations, as shown for example in
The electrode 300 (e.g., field electrode, ground electrode, extractor electrode, etc.) preferably functions to expose the working material to an electric field (e.g., by having a different electric potential than the working material, working electrode, acting as a ground plane, etc.). However, the electrode can otherwise function. The electrode preferably opposes the emitter array across a gap (e.g., a gap with a separation distance as described above), but can be integrated into the emitter array (e.g., for a portion of an emitter structure) and/or otherwise be arranged. The electrode is preferably connected to the frame, but can be separate from and/or otherwise interfaced with the frame.
The electrode can be a wire electrode, a grid electrode (e.g., include through-holes arranged on a grid such as a grid matching an emitter array pattern, as shown for example in
The apertures preferably match the emitter array (e.g., each emitter is aligned to an aperture). For instance, a plurality of emitters can eject working material through a common aperture and/or each emitter can be aligned to a unique aperture. However, the apertures can otherwise be arranged. In a specific example, rectangular apertures can be aligned to (e.g., arranged above) a comb of emitters. In a second specific example, a hexagonal grid of apertures can be aligned to a hexagonal array of emitters. A spacing between the apertures preferably matches a spacing between emitters (in at least one dimension). For instance, the aperture spacing can be between about 10-1000 μm. However, the apertures can be arranged in any manner and/or have any spacing.
The electrode(s) preferably have a low nominal electrical current (eg., during operation such as when working material is being emitted). In a first specific example, a low nominal electrical current can be 0 A, 1 fA, 5 fA, 10 fA, 50 fA, 100 fA, 500 fA, 1 pA, 5 pA, 10 pA, 50 pA, 100 pA, 500 pA, 1 nA, 5 nA, 10 nA, 50 nA, 100 nA, values or ranges therebetween. In a second specific example, a low nominal electrical current can be a percentage of an emitted ion current (e.g., current of working material emitted) such as <0.001%, 0.001%, 0.002%, 0.005%, 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, and/or values or ranges therebetween. However, the electrode can have a high nominal electrical current (e.g., where one or more mitigation can offset an impact of a high nominal electrical current on the lifetime of the apparatus; >100 nA; >1% of an emitted ion current; etc.).
The apparatus can include a plurality of electrodes. Each electrode can be electrically isolated from other electrodes (e.g., connected to different power supplies, grounds, etc.), can be in electric communication with other electrodes (e.g., a first subset of electrodes can be connected to a common ground, to a common reference, to a common power supply, to a common power supply output, etc.; and a second subset of electrodes can be connected to a second ground, to a second reference, to a second power supply, to a second power supply output, etc.), can be connected to a power supply, connected to a reference, connected to a ground, and/or otherwise have any suitable electrical connections. Electrodes connected to a common potential source (e.g., power supply, power supply terminal, ground, reference, etc.) are preferably connected in parallel, but can be connected in series.
In some embodiments, the electrode connection to the common potential source (e.g., power supply) can include balancing electronics 400, which can function to reduce an amount of current that passes through an electrode during a shorting event, identify electrodes (e.g., electrode segments, number of electrodes, specific electrodes, etc.) that have experienced a shorting event (e.g., based on a measured current), and/or can otherwise function. These embodiments are particularly beneficial when low nominal extractor currents are used, when an instantaneous performance of different emitter arrays is similar (e.g., differs by less than about 1%, 2%, 5%, 10%, 20%, etc.), and/or can be used in any suitable situations. The balancing electronics can be passive and/or active. The balancing electronics are preferably high impedance resistors (e.g., resistors with an impedance greater than or equal to an impedance of a nominally firing thruster; 100 kΩ, 500 kΩ, 1 MΩ, 5 MΩ, 10 MΩ, 50 MΩ, 100 MΩ, 500 MΩ, 1 GΩ, 10 GΩ, >10 GΩ, values or ranges therebetween, etc.; etc.), but can additionally or alternatively include a low voltage relay (e.g., a field effect transistor switch, solid state relay, reed relay, electromechanical relay, etc.), a diode (e.g., Zener diode), capacitors, inductors, active circuit element (e.g., measure a voltage drop and change the circuit such as modify potential, using a switch, etc. based on the measured voltage drop), a fuse (e.g., a one-time disconnecting switch, fast acting fuse, time delay fuse, progressive fuse, etc.), and/or any suitable electrical components can be used.
A surface of the electrode (particularly but not exclusively a surface of the electrode proximal an emitter array) is preferably substantially flat (e.g., has a surface roughness less than a threshold roughness such as <10 μm, <1 μm, <100 nm, etc.). However, the electrode can have any suitable surface roughness. Features (e.g., particles, structures, corners, etc.) of the electrode preferably have a radius of curvature greater than about 5 μm (e.g., >10 μm, >20 μm, >50 μm, >100 μm, etc.). However, the features can have a radius of curvature that is less than about 5 μm. The radius of curvature can depend on a density of the features, a peak local electrical field generated by features, on an electric potential, a working material, an electrode material, and/or depend on any suitable property of the apparatus or component(s) thereof. As an illustrative example, chemical polishing (e.g., in a heated etchant bath under ultrasonication) can be used to smooth sharp corners and remove (e.g., reduce the number of) irregularities at the scale of 1 to 10 micrometers. In a second illustrative example, annealing can be used to smooth sharp corners (e.g., by heating a material to a temperature near (e.g., within 1° C., 5° C., 10° C., 20° C., 50° C., etc.; to a temperature that depends on a radius of curvature of the sharp features; etc.) a phase transition temperature (e.g., a glass transition temperature, a melting temperature, etc.). However, the features can have any suitable radius of curvature (and/or distribution of radii of curvature).
The electrode can include (e.g., be made of) semiconductors (e.g., silicon), metals (e.g., gold, titanium, chromium, silver, copper, tungsten, etc.), glasses (e.g., a transparent conductive oxide such as indium tin oxide, fluorine doped tin oxide, etc.; semiconducting glass; etc.), polymers (e.g., conductive polymers such as polyacetylene, polyphenylene vinylene, polypyrrole, polythiophene, polyaniline, polyphenylene sulfide, etc.), alloys (e.g., metal alloys), composite materials (e.g., carbon-filled PEEK, carbon filled polyimide, etc.), carbonaceous electrodes (e.g., graphite, graphene, carbon nanotube, graphite oxide, etc.), conductive liquid(s) (e.g., ionic liquids, molten salts, ionic solutions, etc. such as contained within a channel, capillary, between plates, within a cavity, low melting temperature metals, etc.), dry polymer electrolytes, gel electrodes, ceramic electrolytes, organic ionic plastic crystals (e.g., 1,2,4-triazolium perfluorobutanesulfonate, imidazolium methanesulfonate, etc.), and/or other suitable material. The electrode (e.g., electrode materials) preferably has a low yield (e.g., less than about 1%, 2%, 5%, 10%, 20%, etc.) of secondary electron emission or backscatter electron emission, but can have any suitable yield of secondary electron emission or backscattered electron emission.
In some embodiments, an electrode can undergo a process that interrupts (e.g., ceases, prevents, hinders, decreases, etc.) an electrical communication between working material and the electrode (e.g., working material in contact with the electrode such as during a shorting event). Examples of such interruption processes include: thermal fusing (e.g., melting, evaporation, sublimation, into a nonconductive phase, etc. such as when electrical current passes through the electrode), melt and reflow (e.g., to break a connection from nearby thermal events such as arcing), conductive material displacement (e.g., by gas bubble generation due to heating, electrochemistry, etc.), etching, and/or any suitable process.
In a first specific example, an electrode can have a thickness (e.g., be a thin film) such that working material that impinges upon the electrode can etch through the electrode (e.g., to prevent or end shorting that otherwise occurs when the electrode and working material are in contact, act as a degradable electrode, degradable coating, etc.). For instance, the electrode (or conductive material thereof such as a coating as discussed below) can have a thickness between about 10-200 nm (e.g., to ensure a sufficient grain size for electrical properties, a thickness that can be etched through, etc.). However, the electrode can have a greater thickness (e.g., greater than 200 nm) or smaller thickness (e.g., less than about 10 nm). The electrode material preferably does not react with the working material unless an electric current is present (e.g., an electrical current greater than a threshold electrical current such as 1 fA, 5 fA, 10 fA, 50 fA, 100 fA, 500 fA, 1 pA, 5 pA, 10 pA, 50 pA, 100 pA, 500 pA, 1 nA, 5 nA, 10 nA, 50 nA, 100 nA, 500 nA, 1 μA, values or ranges therebetween, <1 pA, >1 μA, etc.), but the electrode material can react with the working material in the absence of an electric current. Exemplary electrode materials that can be used (particularly but not exclusively) in this first specific example include titanium, chrome (e.g., chromium), silicon, boron, iron, bismuth, zinc (e.g., zinc solid, zinc mercury amalgam, etc.), tantalum, nickel, silver (e.g., with a sulfur source), and/or any suitable electrode material can be used.
In a second specific example (as shown for instance in
In variations of the second specific example, the electrode can include low melting point, low boiling point, low sublimation point, etc. conductive materials. For instance, indium, thallium, tin, lead, bismuth, alloys, amalgams, conductive polymers (e.g., that can undergo a phase transition to a nonconductive state at or above a threshold temperature), and/or any suitable materials (e.g., metals with a melting point less than a threshold temperature such as 300° C., 350° C., 500° C., etc.) can be used as the conductive material. In these variations, the conductive material can undergo a phase change (e.g., boil, sublime, melt, etc.) when a shorting event occurs (e.g., due to resulting heat generation) and be shuttled away from the shorting location (thereby interrupting, ending, decreasing an amount of electricity channeled, etc.).
In a third specific example (as shown for instance in
The first, second, and/or third specific examples interruptible electrodes can be combined in any manner. For instance, a capillary can include a coating that can be etched away, a capillary can be made of a memory metal, a memory metal can include a coating that can be etched away, and/or the electrodes can be combined in any manner.
An electrode can optionally be segmented (e.g., as shown for example in
Each segment can be connected to the power supply using the same balancing electronics, each segment can have separate balancing electronics, a subset of segments can be connected to the power supply via balancing electronics (e.g., where the remaining segments are connected to the power supply without using balancing electronics), different segments can be connected to different power supplies, and/or the segments can otherwise be connected to the power supply(s).
Each segment of the electrode can be operated at the same and/or different electrical potential. In an illustrative example, an electrode can be striped (e.g., include bars) with a predetermined number of segments (e.g., each grid can be a segment; a set of 2, 3, 4, 5, 10, 20, etc. grids can form a segment; quadrants; octants; orthants; sectors; etc.) with each segment having a lower electrical potential (e.g., 1 V, 2 V, 5 V, 10 V, 20 V, etc.) lower than the previous segment such that across the emitter array the emission drops according to the current-voltage performance of the emitters. In variations of this illustrative example, the segments can have an electrical potential that is determined based on a thruster response, emitter response (e.g., a measured emitter response), a target thruster operation (e.g., a gradient to achieve a target operation), operation instructions (e.g., where instructions can be sent to the electrode to change, modify, update, etc. the electrical potential of each segment individually, in concert, etc.), based on shorting events (e.g., in other segments), based on a dynamic electrode geometry (e.g., gap distance varying with voltage), and/or can otherwise be determined.
In some embodiments, an electrode (e.g., an extractor electrode, a distal electrode, accelerator electrode working electrode, etc.) can include a thermal element (e.g., heating element, cooling element), which can function to modify a temperature of the electrode, the emitter array, working material, the frame, and/or any suitable material or structures. For example, the thermal element can be used to cause decomposition of the working material, accelerate working material degradation, cause a phase change in the working material (and/or electrode, coating, etc.), otherwise facilitate (e.g., initiate) a reaction in any accumulated working material or working material byproducts, change an emission (e.g., firing) operation (e.g., raising a temperature of working material to increase an emission current of working material, lowering a temperature of working material to decrease an emission current of working material, etc.), and/or can otherwise function. The thermal element could be the electrode itself and/or another component (e.g., a resistive heater, a radiative heater, a thermo-electric cooler, a heat sink, etc.). In some variants, the thermal energy can be provided by a radiant (and/or non-integrated) source (e.g., the sun, nuclear source, exothermic reaction, endothermic reaction, etc.), where the electrode can include (e.g., be made of, be coated with, etc.) a high-absorptivity (e.g., with an absorptivity that depends on the source, absorptivity greater than about 0.8, etc.) material. In related variants, coupling the thermal element with a material (e.g., a coating, a substrate, etc.) that is low-emissivity (e.g., thermal emissivity less than about 0.2) could enable less power to be used to reach a high temperature. However, any suitable thermal element(s) can be used.
In a variant of the thermal element, the thermal element can enable a temperature control between about −50 and 100 ° C. (e.g., −55-105° C., −50-0° C., −20-0° C., −10-0° C., −50-50° C., −20-70° C., 0-70° C., 0-100° C., 20-70° C., 20-100° C., values or ranges therebetween), or over a temperature range that extends below −50° C. or above 100° C. The temperature (or temperature range) can be associated with a linear, nearly-linear (e.g., regression fit greater than about 0.9), polynomial, and/or complex apparatus response. In a specific example, instructions can be transmitted to modify a temperature of the apparatus or components thereof (e.g., the working material, electrodes, etc.) such as to modify an emission current of working material (e.g., in connection to and/or independent of modifying the emission current by changing an electric potential).
The apparatus can optionally include one or more secondary electrodes 360, which can function to mitigate (e.g., prevent, hinder, decrease) the exposure of a failed emitter and/or electrode to still working electrodes, to a space environment, and/or to any suitable environment. However, additionally or alternatively, the secondary electrode(s) can function to protect the apparatus (e.g., emitters, working material, electrode, etc.) from electrons or other charged particles (e.g., to protect the emitters from electrons or other charged particles such as protons, secondary ions, ion fragments, cosmic rays, etc. from interacting with the emitter surface), can function as an accelerator electrode(s), can function as a redundant electrode (e.g., in the event of failure, shorting events, etc. in the electrode), and/or can function in any manner. The secondary electrode can be supported by the frame, supported by an auxiliary structure, mounted to a spacecraft, and/or can otherwise be arranged and/or supported. The secondary electrode can be between the emitter array and the electrode and/or oppose the emitter array across the electrode. The secondary electrode can be offset from (e.g., above, distance between, etc.) the electrode by any amount between about 0-10 mm (e.g., 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 500 μm, 1 mm, 2 mm, 3 mm, 5 mm, 7 mm, 9 mm, 10 mm, 10.5 mm, values or ranges therebetween, etc.; in the same plane as, preferably but not exclusively when the thickness of the secondary electrode is greater than the electrode; etc.), but can have a separation larger than 10 mm. However, a secondary electrode can otherwise be arranged.
The secondary electrodes are preferably at approximately the same potential as the electrode (e.g., when the electrode acts as a ground plane, the secondary electrode can also act as a ground plane; within a threshold electrical potential of the primary electrode such as within 1 V, 5 V, 10 V, 50 V, 100 V, 500 V, 1000 V, values or ranges therebetween, >1000 V, <1 V, etc.; etc.), but can be at a different potential.
A secondary electrode can be the same as the electrode (e.g., same structure), a halo electrode (e.g., have an aperture such that working material from all or a subset of emitters pass through the same aperture; have an aperture that surrounds the electrode, emitter array, etc.; etc.), and/or can have any suitable structure. A secondary electrode can have any suitable electrode structure (e.g., such as structures described above for electrodes) and/or any suitable structure and/or composition.
In some variants (e.g., when the electrode is a grid electrode), openings in the secondary electrode can be the same as in the electrode, can be larger than in the electrode (e.g., to decrease a risk of working material impinging on the secondary electrode), and/or can be smaller than in the electrode (e.g., to provide better protection, shielding, etc.). In a first specific example, a grid electrode can have a pair of bars that cooperatively define an opening associated with a given emitter (e.g., working material emitter from the emitter is intended to pass through the opening in the bars; such that a different pair of bars is associated with each emitter, emitter structure, etc.; etc.) and a secondary electrode can similarly have a pair of bars that cooperatively define an opening associated with the emitter. In variants of the first specific example, such as for electrodes that include a grid of holes that working material passes through, holes in the electrode can be the same size as holes in the secondary electrode (e.g., a hole in the electrode can be aligned to or associated with an emitter and the holes in the secondary emitter can be associated the same emitter or emission structure). In a second specific example (as shown for example in
In some variants, in addition or alternative to the secondary electrodes, conductive shielding can be provided between emitter arrays and/or between electrodes.
In some embodiments, a frame and/or an electrode can include (e.g., be made from) a substrate 220, 320 that is coated with a coating material 240, 340 (e.g., a coating material can be deposited on, disposed on, grown on, in contact with, supported by, etc. a substrate). However, the substrate can be bare (e.g., not include a coating). The substrate can function to provide mechanical support, electrical stability, and/or otherwise stabilize the electrode and/or frame and/or otherwise function. The substrate is preferably dielectric, but can be conductive, semiconducting, and/or have any suitable electrical properties. Examples of substrate materials include: ceramics (e.g., alumina, titania, yttria, etc.), glasses, composites (e.g., including a matrix such as an epoxy resin; a reinforcement such as woven glass fibers, nonwoven glass fibers, paper, etc.; filler such as ceramics, titanate ceramics; etc.), laminates (e.g., polytetrafluoroethylene, FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-2, CEM-4, CEM-5, G-10, RF-35, etc.), metals (e.g., aluminum, copper, etc.), insulated metal substrate, polymers (e.g., polyimide, polytetrafluoroethylene, ceramic-filled polytetrafluoroethylene, etc.), and/or any suitable material(s). The substrate is preferably resilient to reactive species (e.g., atomic oxygen, plasma, atomic hydrogen, solar particles, etc.), but can have any suitable chemical compatibility to reactive species. The substrate thickness can be between about 10 μm and 10 mm, less than 10 μm thick, and/or greater than 10 mm thick. In a specific example, the substrate size (e.g., width, thickness, etc.) can be between about 50-500 μm, which can be beneficial for conferring sufficient mechanical stiffness while mitigating a risk of working material impinging upon the electrode.
The coating can function to protect, stabilize, confer a property (e.g., electrical conductivity, stiffness, chemical resistance, physical resistance, adhesion, electrical properties, multifunctionality, behavior change with material removal, etc.), and/or can otherwise function. The electrode and/or frame can include a dielectric coating (e.g., a passivating coating), a reactive coating (e.g., a degradable coating, a coating that undergoes an electrochemical reaction with working material at a threshold electrical potential, where the reaction byproduct can be dielectric or otherwise limit or stop electrical shorting between working material and the electrode as shown for example in
The coating can cover surfaces (e.g., of the electrode, of the frame, etc.) facing (e.g., directed toward, with a broad face in view of, proximal, as shown in
A substrate can include a plurality of coatings. Each coating can be the same (e.g., materials, type, thickness, etc.) or different (e.g., materials, type, thickness, etc.). For instance, an electrode can be made of a substrate (e.g., a dielectric substrate) that includes an electrically conductive coating, where the electrically conductive coating can be protected with a dielectric coating. However, any suitable number and/or types of coating can be used.
The coating (e.g., coating materials) preferably has a low yield (e.g., less than about 1%, 2%, 5%, 10%, 20%, etc.) of secondary electron emission or backscatter electron emission, but can have any suitable yield of secondary electron emission or backscattered electron emission.
In variants that use a dielectric coating, the coating is preferably not too thick (e.g., can have a thickness that is between about 50-500 μm, thickness <about 500 μm, etc.) as thick dielectric coatings can build up charge and lead to a screening of the working material from the target electric field. However, thick dielectric coatings can be used to tune a local electric field (e.g., for individual emitters, for clusters of emitters, etc.; configured to limit or hinder further impingement of working material on an electrode; etc.), dielectric charging can be mitigated (e.g., using a charge extractor), and/or can otherwise be used. Examples of dielectric coating materials include: silicon oxides (e.g., SiOx), silicon nitride (e.g., SiNx), silicon oxynitrides (e.g., SiOxNy), polymers (e.g., polyether ether ketone (PEEK), polyimide, polytetrafluoroethylene, ceramic-filled polytetrafluoroethylene, etc.), resin (e.g., glass-reinforced UV-cured resin, UV-cured resin, etc.), ceramics (e.g., metal ceramics, aluminum oxide, yttrium oxide, titanium oxide, zinc oxide, zirconium oxide, hafnium oxide, tungsten oxide, barium titanate, silicon aluminum oxynitride, silicon carbide, magnesium silicate, titanium carbide, uranium oxide, yttrium barium copper oxide, etc.), and/or any suitable coating material can be used. A breakdown voltage of the dielectric (e.g., dielectric coating, dielectric baffle, dielectric frame, substrate, etc.) is preferably at least 2 kV. However, the dielectric breakdown voltage can be less than 2 kV. The breakdown voltage can depend on a thickness of the coating, a uniformity of the coating, a surface roughness of the coating, a coating material, an impurity of the coating (e.g., impurity concentration, impurity identity, etc.), and/or can depend on any suitable property of the coating.
The optional power supply 500 preferably functions to generate one or more electric signals (e.g., electric potentials, current, etc.). The electric signal(s) are preferably direct current (DC), but can additionally or alternatively be alternating current (AC) (e.g., where a frequency can depend on an operation of the apparatus, can be fixed, etc.; low frequency; etc.), pulsating current, variable current, transient currents, and/or any current. The power supply can be in electrical communication with the emitter array, the substrate, the working material, the reservoir, the distal electrode, the counter electrode, an external system (e.g., satellite such as small satellites, microsatellites, nanosatellites, picosatellites, femto satellites, CubeSats, spacecraft, etc.), an electrical reference (e.g., an electrical ground), and/or any suitable component. The power supply preferably generates large electric potentials such as at least 500 V, 1 kV, 1.5 kV, 2 kV, 3 kV, 4 kV, 5 kV, 10 kV, 20 kV, 50 kV. However, the power supply can generate electric potentials less than 500 V and/or any suitable electric potential. The electric potentials can depend on the working material, the emitter material, emitter separation distance, emitter geometry, emitter parameters, emitter array properties, emitter-electrode separation distance, and/or any suitable properties. The power supply is preferably able to output either polarity electric potential (e.g., positive polarity, negative polarity), but can output a single polarity. For example, the power supply can simultaneously (e.g., concurrently), contemporaneously (e.g., within a predetermined time such as 1 ns, 10 ns, 100 ns, 1 μs, 10 μs, 100 μs, 1 ms, 10 ms, 100 ms, 1 s, 10 s, 1 ns-10 μs, 1 μs-100 μs, 100 μs-10 ms, 1 ms-1 s, etc.), serially, or otherwise output a first (polarity) electric potential (e.g., to working material associated with a first subset of emitters, to working material associated with a first subset of emitter arrays, to a first distal electrode, to a first reservoir, etc.) and a second (polarity) electric potential (e.g., to working material associated with a second subset of emitters, to working material associated with a second subset of emitter arrays, to a second distal electrode, to a second reservoir, etc.). However, the power supply can switch polarity, the apparatus can include more than one power supply (e.g., one power supply associated with each emitter array, two or more power supplies associated with each emitter array, one power supply associated with each subset of emitter arrays, etc.) and/or the power supply(s) can be otherwise arranged.
In a specific example, the power supply can be the same as any power supply as described in U.S. patent application Ser. No. 17/066,429 titled “SYSTEM AND METHOD FOR POWER CONVERSION” filed 8 Oct. 2020, which is incorporated herein in its entirety by this reference. However, any power supply can be used.
In an illustrative example (as shown for example in
The apparatus can optionally include a control system (e.g., computing system, processor, microprocessor, sensor, etc.) which can control the apparatus operation (e.g., based on instructions received from an operator such as a terrestrial operator, based on a feedback, based on measured electrical signal(s) such as extractor current, based on predetermined operations, etc.).
The apparatus (particularly, but not exclusively, the frame and/or electrodes) can be made (e.g., manufactured, coated, shaped, etc.) using patterning (e.g., photolithography, shadow masking, etc.), deposition (e.g., growth; chemical vapor deposition (CVD) such as atmospheric pressure CVD, low pressure CVD, plasma enhanced CVD, etc.; physical vapor deposition (PVD) such as sputtering, evaporative deposition, electron beam PVD, etc.; epitaxy; etc.), etching (e.g., dry etching, plasma etching, reactive-ion etching, deep reactive ion etching, wet etching, chemical etching, etc.), forming (e.g., microextrusion, microstamping, microcutting, etc.), laser-based techniques (e.g., laser direct-writing, microstereolithiography, multiphoton lithography, laser CVD, laser-induced forward transfer, laser ablation, etc.), 3D printing (e.g., fused filament fabrication), and/or using any suitable techniques.
Embodiments of the apparatus and/or method can include every combination and permutation of the various apparatus components and the various method processes, wherein one or more instances of the method and/or processes described herein can be performed asynchronously (e.g., sequentially), concurrently (e.g., in parallel), or in any other suitable order by and/or using one or more instances of the apparatuses, elements, and/or entities described herein.
As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.
This application claims the benefit of U.S. Provisional Application No. 63/150,502 filed 17 Feb. 2021 and U.S. Provisional Application No. 63/283,705 filed 29 Nov. 2021, each of which is incorporated in its entirety by this reference.
Number | Date | Country | |
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63150502 | Feb 2021 | US | |
63283705 | Nov 2021 | US |