Phased array electrostatic thrusters

Abstract

A phased array electrostatic thruster includes an ion source, a plurality of thruster stages, and a controller. Each thruster stage includes an attractor-repeller and a power output coupled to the attractor-repeller. The controller is communicably coupled to the power output and configured to control the power output in phases to switch operation of the attractor-repeller between an attractor operating mode and a repeller operating mode.

Description

Atty. Dkt. No.: 143360-0106PHASED ARRAY ELECTROSTATIC THRUSTERS CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims the benefit of and priority to (a) U.S. Provisional Application No. 63 / 761,858, filed February 21, 2025, and (b) U.S. Provisional Application No. 63 / 819,525, filed June 6, 2025, the entire disclosures of which are hereby incorporated by reference herein.BACKGROUND

[0002] The present disclosure relates to electrostatic thrusters and / or asymmetrical capacitors, which utilize a voltage potential for generating thrust.SUMMARY

[0003] One aspect of the present disclosure relates to a phased array electrostatic thruster including an ion source, a plurality of thruster stages, and a controller. Each thruster stage includes an attractor-repeller and a power output coupled to the attractor-repeller. The controller is communicably coupled to the power output and configured to control the power output in phases to switch operation of the attractor-repeller between an attractor operating mode and a repeller operating mode.

[0004] In some embodiments, a number of thruster stages is greater than a number of phases applied across the plurality of thruster stages.

[0005] In some embodiments, the attractor-repeller includes an insulator disposed across a portion of an outer surface thereof.

[0006] In some embodiments, the ion source is one of a plurality of ion sources that are coupled with respective ones of the attractor-repellers.

[0007] In some embodiments, the plurality of ion sources each include an emitter.

[0008] In some embodiments, each thruster stage includes a pair of attractor-repellers, the ion source disposed between the pair of attractor-repellers.-1- 4919-8285-9408Atty. Dkt. No.: 143360-0106

[0009] In some embodiments, the attractor-repeller of at least one thruster stage of the plurality of thruster stages at least partially forms the ion source.

[0010] In some embodiments, the attractor-repellers of adjacent thruster stages of the plurality of thruster stages are defined by a single wall.

[0011] In some embodiments, an inlet of the plurality of thruster stages is larger than an outlet of the plurality of thruster stages.

[0012] In some embodiments, the controller is configured to reverse the phases.

[0013] In some embodiments, the attractor-repeller is a first attractor-repeller of a first thruster stage of the plurality of thruster stages. Controlling the power output in phases to switch operation of the first attractor-repeller between the attractor operating mode and the repeller operating mode may include (i) in a first phase, applying a first voltage potential between the ion source and the first attractor-repeller such that the first attractor-repeller has a polarity opposite to charged particles generated by the ion source, thereby controlling operation of the first attractor-repeller in the attractor operating mode, and (ii) in a second phase, applying a second voltage potential such that the first attractor-repeller has substantially the same polarity as the charged particles, thereby controlling operation of the first attractor-repeller in the repeller operating mode to repel the charged particles toward a second attractor-repeller of a second thruster stage of the plurality of thruster stages downstream from the first thruster stage.

[0014] In some embodiments, the controller is configured to distribute a voltage potential associated with a respective phase across at least two adjacent thruster stages of the plurality of thruster stages such that a first voltage difference between the ion source and a first attractor-repeller nearest to and following the ion source is less than a second voltage difference between the ion source and a second attractor-repeller more distant from and following the ion source than the first attractor-repeller.

[0015] Another aspect of the present disclosure relates to an electrostatic thruster including a plurality of attractor-repellers arranged along a flow direction and an emitter electrode, the-2- 4919-8285-9408Atty. Dkt. No.: 143360-0106attractor-repellers and the emitter electrode together configured to form an ion source in at least one phase of operation.

[0016] In some embodiments, the electrostatic thruster includes a power output coupled to each attractor-repeller of the plurality of attractor-repellers and a controller communicably coupled to the power output and configured to control the power output in phases to switch operation of respective ones of the attractor-repellers between an attractor and a repeller.

[0017] In some embodiments, the electrostatic thruster includes an alternating-current power supply coupled to the emitter electrode, a direct-current power supply coupled to an attractor-repeller of the plurality of attractor-repellers, and a capacitor electrically coupled between the alternating-current power supply and the emitter electrode such that a voltage of the emitter electrode floats with changes in voltage of the attractor-repeller.

[0018] In some embodiments, the attractor-repeller is a first attractor-repeller. The controller may be configured to (i) in a first phase, operate the alternating-current power supply to apply alternating voltage to the emitter electrode such that the emitter electrode and the first attractor-repeller together generate a cloud of charged particles, and (ii) in a second phase, operate the direct-current power supply to supply direct-current voltage to (a) a second attractor-repeller of the plurality of attractor-repellers of a downstream stage to attract the cloud of charged particles and (b) the first attractor-repeller of an upstream stage of substantially the same polarity as the cloud of charged particles such that the first attractor-repeller repels the cloud of charged particles toward the downstream stage.

[0019] In some embodiments, an attractor-repeller of the plurality of attractor-repellers includes an insulator disposed across a portion of an outer surface thereof.

[0020] In some embodiments, the electrostatic thruster includes a plurality of emitter electrodes, including the emitter electrode, arranged along the insulator spaced from the attractor-repeller by a distance.

[0021] In some embodiments, the distance is a first distance, and the first distance is less than or equal to half of a second distance between an uninsulated portion of the attractor--3- 4919-8285-9408Atty. Dkt. No.: 143360-0106repeller and a respective emitter electrode of the plurality of emitter electrodes nearest the uninsulated portion.

[0022] Still another aspect of the present disclosure relates to electrostatic thruster including a plurality of stages arranged along a flow direction and a controller. Each stage includes an attractor-repeller having an insulated upstream portion and an uninsulated downstream portion and a plurality of emitter electrodes disposed on opposing sides of the attractorrepeller along the insulated upstream portion and spaced from an outer surface of the attractor-repeller. The controller is configured to control voltages applied to the attractorrepeller and the plurality of emitter electrodes in phases such that, in a first phase, the plurality of emitter electrodes and the attractor-repeller of a respective stage of the plurality of stages together generate a cloud of charged particles, and, in a second phase, the attractor-repeller of an upstream stage of the plurality of stages repels the cloud of charged particles while the attractor-repeller of a downstream stage of the plurality of stages attracts the cloud of charged particles.

[0023] This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements.BRIEF DESCRIPTION OF THE FIGURES

[0024] FIG. l is a perspective view of an electrostatic thruster, according to an embodiment.

[0025] FIG. 2 is a side view of a phased array electrostatic thruster, according to an embodiment.

[0026] FIG. 3 is a waveform diagram indicating voltage polarity for stages of a phased array electrostatic thruster as a function of time, according to an embodiment.

[0027] FIG. 4A is an electric field diagram of the phased array electrostatic thruster of FIG.2 in a first stage of operation, according to an embodiment.-4- 4919-8285-9408Atty. Dkt. No.: 143360-0106

[0028] FIG. 4B is an electric field diagram of the phased array electrostatic thruster of FIG.2 in a second stage of operation, according to an embodiment.

[0029] FIG. 5 is a waveform diagram indicating voltage polarity for stages of a phased array electrostatic thruster as a function of time, where the phased array electrostatic thruster includes stages having overlapping polarities in time, according to an embodiment.

[0030] FIG. 6 is a waveform diagram indicating voltage polarity as a function of time for stages of a phased array electrostatic thruster that includes a shorter ion generation period having a more dynamic transition from one polarity to another for the stages as compared to the waveform diagram of FIG. 5.

[0031] FIG. 7 is a waveform diagram indicating voltage polarity as a function of time for stages of a phased array electrostatic thruster in which a high voltage potential is spread across multiple stages, according to an embodiment.

[0032] FIG. 8 is a perspective view of a phased array electrostatic thruster that can be formed using the phased array electrostatic thruster design of FIG. 1, according to an embodiment.

[0033] FIG. 9 is a side view of a phased array electrostatic thruster including emitters disposed between attractor-repeller electrodes of the same stage, according to an embodiment.

[0034] FIG. 10A is an electric field diagram of the phased array electrostatic thruster of FIG. 9 in a first stage of operation, according to an embodiment.

[0035] FIG. 10B is an electric field diagram of the phased array electrostatic thruster of FIG. 9 in a second stage of operation, according to an embodiment.

[0036] FIGS. 11 A and 1 IB are side views of a phased array electrostatic thruster including emitters disposed between attractor-repeller electrodes of the same stage, according to another embodiment.

[0037] FIG. 12A is an electric field diagram of the phased array electrostatic thruster of -5- 4919-8285-9408Atty. Dkt. No.: 143360-0106FIGS. 11 A-l IB in a first stage of operation, according to an embodiment.

[0038] FIG. 12B is an electric field diagram of the phased array electrostatic thruster of FIGS. 11 A-l IB in a second stage of operation, according to an embodiment.

[0039] FIG. 13 is a perspective view of a phased array electrostatic thruster that may be formed using the phased array electrostatic thruster designs of FIG. 9 or FIGS. 11 A-l IB, according to an embodiment.

[0040] FIG. 14 is a perspective view of a phased array electrostatic thruster that may be formed using the phased array electrostatic thruster designs of FIG. 9 or FIGS. 11 A-l IB, in which attractor-repeller electrodes within the same stage that are arranged in an enclosed shape, according to an embodiment.

[0041] FIG. 15 is a side view of a phased array electrostatic thruster in which attractorrepeller electrodes of adjacent stages are formed into a shared wall, according to an embodiment.

[0042] FIG. 16 is a side view of a phased array electrostatic thruster in which attractorrepeller electrodes of adjacent stages define a converging flow passage, according to an embodiment.

[0043] FIG. 17 is a side view of a phased array electrostatic thruster including a combined dielectric barrier discharge attractor-repeller electrode, according to an embodiment.

[0044] FIG. 18 is an electric field diagram of the phased array electrostatic thruster of FIG.17 showing electric field line approximations for the phased array electrostatic thruster during at least one stage of operation, according to an embodiment.

[0045] FIG. 19 is a waveform diagram indicating voltage polarity as a function of time for each stage of a phased array electrostatic thruster that may be used with the phased array electrostatic thruster of FIG. 17, including an overlay indicating when the ion generation occurs for each phase, according to an embodiment.

[0046] FIG. 20 is a perspective view of a phased array electrostatic thruster that may be -6- 4919-8285-9408Atty. Dkt. No.: 143360-0106formed using the phased array electrostatic thruster design of FIG. 17, according to an embodiment.

[0047] FIG. 21 is a perspective view of a phased array electrostatic thruster that may be formed using the phased array electrostatic thruster design of FIG. 17, according to another embodiment.DETAILED DESCRIPTION

[0048] Before turning to the figures, which illustrate certain exemplary embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.Overview

[0049] Electrostatic thrusters (which can also be referred to as electrohydrodynamic (EHD) thrusters and / or electroaerodynamic (EAD) thrusters) are a type of electric device that uses electrostatic forces to generate thrust and propulsion, such as through air or another fluid. As shown in FIG. 1, an embodiment of an electrostatic thruster 10 (e.g., a thruster assembly, etc.) is shown that includes an emitter 12, a collector 14, spacers 16, and a power source 18. In other embodiments, the electrostatic thruster 10 can include additional, fewer, and / or different components.

[0050] The emitter 12 is configured to generate a “cloud” of charged particles (e.g., ions) under an applied voltage from the power source 18. In some embodiments, and as shown, the emitter 12 includes an electrode, which can include a conductive wire mounted at a distance apart from the collector 14 by the spacers 16. In the embodiment of FIG. 1, the spacers 16 are made from an electrically insulative material with high electrical resistance, which may include a dielectric material such as fiberglass, epoxy, or another electrical insulator, to provide a fixed gap size between the emitter 12 and the collector 14 and to generate a desired field strength (Coulomb force) at the emitter 12.-7- 4919-8285-9408Atty. Dkt. No.: 143360-0106

[0051] The collector 14 is configured to generate a force due to the attraction between the charged particles and the collector 14. In some embodiments, and as shown, the collector 14 is made from a sheet of metal or another lightweight conductive material. The voltage potential between the charged particles and the collector 14 generates a force on the collector 14 in the direction of the emitter 12.

[0052] The thrust produced by the electrostatic thruster 10 may be adjusted by increasing the voltage potential applied to the emitter 12. However, increasing the voltage potential on the emitter 12 can also result in greater numbers of charged particles being repelled from the emitter 12 in the opposite direction as the collector 14 (“reverse repelling”), which can cause reverse thrust and result in reduced overall thruster efficiency. Additionally, in the embodiment shown in FIG. 1, charged particles passing the trailing edge of the collector 14 can interact with the collector 14 to produce a reverse pull opposite from the net thrust vector produced by the electrostatic thruster 10 (“reverse pulling”), which can cause further reduction in system efficiency.

[0053] Referring to the remaining figures generally, embodiments of the present disclosure relate to phased array electrostatic thrusters that are configured to increase thrust and efficiency relative to existing designs. In contrast to existing designs in which charged particles (ions) are produced at a constant rate by an emitter and attracted by a collector, the phased array electrostatic thrusters of the present disclosure use an active approach to create clouds of charged particles, while accelerating those clouds in a single direction through a number of attractor-repeller stages. The phased array electrostatic thrusters are configured to control the voltage potential on these attractor-repeller stages in a number of phases, so that the charged clouds can be propelled by an identical polarity of attractor-repeller stages on one side of the charged clouds, while simultaneously being attracted by opposite polarity attractor-repeller stages on the other side of the charge clouds. Beneficially, such configurations can substantially reduce or eliminate losses caused by reverse repelling at the emitter and / or reverse pulling downstream the collector.

[0054] Due to the use of alternating attractor-repeller stages, the phased array electrostatic thrusters of the present disclosure can also enable the use of multiple ion sources per-8- 4919-8285-9408Atty. Dkt. No.: 143360-0106attractor-repeller electrode, which can enable greater production of charged particles across the phased array electrostatic thruster, without substantially increasing reverse thrust.

[0055] As used herein, “ion source” refers to at least one electrode configured to emit a “cloud” of charged particles (e.g., ions) under an applied voltage from a power source. In some embodiments, the ion source includes a conductive wire or needles. In other embodiments, the ion source may refer to an active (e.g., decoupled) ion source, such as a dielectric barrier discharge (DBD) ion source (e.g., a DBD emitter), an emitter electrode combined with an intermediate electrode, or any other type of ion source. An example of at least one type of DBD ion source is provided in PCT Application No. PCT / IB2025 / 052968, filed March 20, 2025, the entire contents of which are hereby incorporated by reference herein for any and all purposes. Examples of an intermediate electrode arrangement are provided in Dutch Patent Application No. 2036471, filed December 8, 2023, and U.S. Provisional Application No. 63 / 761,858, filed February 21, 2025, the entire contents of which are hereby incorporated by reference herein for any and all purposes.

[0056] As used herein “attractor-repeller” and “attractor-repeller electrode” refer to an electrode of the phased array electrostatic thruster that is configured to switch polarities periodically during operation and between two different operating modes. For example, and as will be further described, a controller of the phased array electrostatic thruster may control a power output to switch the attractor-repeller between an attractor operating mode in which the attractor-repeller is configured to attract charged particles toward the attractorrepeller, and a repeller operating mode in which the attractor-repeller is configured to repel charged particles away from the attractor-repeller. In some embodiments, the controller may be configured to control the power output to switch operation of the attractor-repeller to function as an attractor to attract a cloud of charged particles during a first timeframe of operation of the phased array electrostatic thruster, and to function as a repeller to repel the same cloud of charged particles during a second timeframe of operation, as will be further described.

[0057] As used herein, “dielectric breakdown” refers to a process whereby an insulating material and / or fluid (e.g., gas) between the emitter and the collector is subjected to high-9- 4919-8285-9408Atty. Dkt. No.: 143360-0106enough voltage to cause an electrical shorting between the ion source and the attractorrepeller (e.g., to cause arcing / sparks and an electrical short through the plasma in the gap between the ion source and the attractor-repeller).Thruster with Offset Ion Source and Attractor -Repeller

[0058] Referring to FIG. 2, a phased array electrostatic thruster 100 is shown, according to an embodiment. The phased array electrostatic thruster 100 (which may also be referred to as a staged electrostatic thruster, a phased array electrostatic thrust system, or a phased array electrostatic thrust assembly) includes multiple individual electrostatic thrusters, shown as stages 101; a support structure (not shown); and a power system 110.

[0059] In some embodiments, and as shown, the multiple individual electrostatic thrusters are arranged in stages in series along a streamwise direction (e.g., a flow direction of fluid flow across the stages when generating thrust). In some embodiments, the phased array electrostatic thruster 100 includes at least three stages, which can enable continuous propulsion across the phased array electrostatic thruster 100. In the embodiment of FIG. 2, the phased array electrostatic thruster 100 includes four or more stages, shown as a first stage 101a, a second stage 101b, a third stage 101c, and a fourth stage 101 d (collectively, stages 101). Such an arrangement can enable more advanced pulse / wave shaping and field control techniques, which can further improve system efficiency, as will be further described. In some embodiments, the phased array electrostatic thruster 100 is controlled using at least two electrical phases. For example, two phases may be used to demonstrate the operational principle of the phased array electrostatic thruster 100. In other embodiments, at least three phases are used to provide substantially continuous propulsion. In still other embodiments, at least four phases are used to facilitate more advanced pulse and / or wave shaping and to provide enhanced control over the electric fields and fluid flow through the multiple stages 101.

[0060] In some embodiments, the phased array electrostatic thruster 100 includes the same number of stages 101 as electrical phases used to control the phased array electrostatic thruster 100. In other embodiments, the phased array electrostatic thruster 100 may include more stages 101 than electrical phases. In such embodiments, the electrical phases may be -10- 4919-8285-9408Atty. Dkt. No.: 143360-0106chained along the stages 101. For example, in a phased array electrostatic thruster that includes eight stages, the system may be configured such that the first and fifth stage are connected to a first electrical phase, a second and sixth stage are connected to a second electrical phase, and so on.

[0061] In some embodiments, and as shown, each of the stages 101 includes at least one ion source 102 (which may also be referred to as an emitter or an exciter) and an attractorrepeller 104. In the embodiment of FIG. 2, each of the stages 101 includes a single ion-source-and-attractor-repeller pair. In the embodiment of FIG. 2, the phased array electrostatic thruster 100 includes an ion source 102 disposed at an inlet 103 of the phased array electrostatic thruster 100. In other embodiments, the phased array electrostatic thruster 100 only includes ion sources 102 downstream from an initial attractor-repeller 104 at the inlet 103.

[0062] In the embodiment of FIG. 2, the ion source 102 is spaced apart from the attractorrepeller 104 along a flow direction through the phased array electrostatic thruster 100. In some embodiments, the ion source 102 includes a conductive wire of small size relative to the attractor-repeller 104 (e.g., a wire having a diameter of about 0.1 mm). In other embodiments, the ion source 102 includes a needle emitter, a DBD emitter, or another type of ion source now known or hereinafter developed.

[0063] In other embodiments, only certain stages 101 of the phased array electrostatic thruster 100 include an ion source. For example, in some embodiments, only the first stage or the second stage of the phased array electrostatic thruster 100 include an ion source. In other embodiments, the system includes an ion source only at certain periodic intervals of stages 101 (e.g., at the first stage and then again at every fifth stage, etc.).

[0064] The attractor-repeller 104 is configured to generate a force responsive to a voltage potential between the charged particles and the attractor-repeller 104. Unlike existing electrostatic thrust devices, which include a collector configured to provide only an attractive force to attract the charged particles toward the collector, the attractor-repeller 104 of the present disclosure is configured to switch between providing attractive and repulsive forces during different phases of operation.-11- 4919-8285-9408Atty. Dkt. No.: 143360-0106

[0065] In some embodiments, and as shown, the attractor-repeller 104 is also configured to discharge as few ions as possible during operation. As shown in FIGS. 2, 4A, and 4B, the attractor-repeller 104 is electrically insulated (e.g., includes at least a partial insulation layer) by an electrical insulation layer (e.g., a dielectric material), shown as insulator 106, along at least a portion of the outer surface thereof. In some embodiments, the attractorrepeller 104 includes the insulator 106, and the insulator 106 is applied along a portion of the attractor-repeller 104 that faces toward the ion source 102. In some embodiments, the insulator 106 is applied across, and covers, a substantial portion of a body and / or outer wall of the attractor-repeller 104 that extends away from the ion source 102. In some embodiments, the insulator 106 may be arranged along the body of the attractor-repeller 104 in any of the arrangements described in Dutch Patent Application No. 2036471, filed December 8, 2023. Beneficially, the insulator 106 can spread out the electrical field strength across the attractor-repeller 104 and increase the path length across which ions cannot be discharged and continue to provide thrust. In other embodiments, the attractorrepeller 104 may be an uninsulated attractor-repeller that does not include any dielectric materials.

[0066] In the embodiment of FIG. 2, the attractor-repeller 104 of each of the stages 101 includes an insulator 106 applied across an outer surface of a body thereof. In some embodiments, a thickness of the insulator 106 decreases along the flow direction from the leading edge to the trailing edge of the attractor-repeller 104. The insulator 106 is configured to reduce the number of charged particles that are discharged as they move across the attractor-repeller 104, so that at least some of the charged particles may continue to pass between adjacent stages 101 of the phased array electrostatic thruster 100 during operation.

[0067] As shown in FIG. 2, a distance Di is defined between the ion source 102 of a respective stage 101 and a leading edge of the corresponding attractor-repeller 104 in the respective stage 101. For example, a distance Di between the first stage ion source 102a and a leading edge of the first stage attractor-repeller 104a is shown in FIG. 2. In some embodiments, Di can be determined based at least in part on an electric field strength in the gap between the ion source 102 and the attractor-repeller 104 or a timing of the motion of-12- 4919-8285-9408Atty. Dkt. No.: 143360-0106the charged particles 128 from the ion source 102 toward the attractor-repeller 104, among other factors.

[0068] As shown in FIG. 2, each attractor-repeller 104 defines an insulated length D2 and an uninsulated length D3 along the flow direction. In some embodiments, the insulator 106 covers an upstream portion of the attractor-repeller 104 having the length D2, and an uninsulated downstream portion has the length D3. Collectively, the sum of D2 and D3 corresponds to a total length of the attractor-repeller 104 in the streamwise direction. For example, in FIG. 2, the insulator 106 of the first stage attractor-repeller 104a covers an upstream portion of the length D2, and a downstream portion of the first stage attractor-repeller 104a has the length D3 and is not covered by the insulator 106. In some embodiments, the insulator 106 covers the substantial entirety of the attractor-repeller 104. In such embodiments, the length D2 may be equal to the total length of the attractor-repeller 104.

[0069] As shown in FIG. 2, a distance D4 is defined between adjacent attractor-repellers 104 in adjacent stages 101 along the flow direction. For example, as shown in FIG. 2, the distance D4 may be defined between a trailing edge of the first stage attractor-repeller 104a and a leading edge of the second stage attractor-repeller 104b. In some embodiments, the distance D4 can be determined based at least in part on a spacing between stages 101 to coordinate the timing of phase changes with a travel time of the charged particles 128 between successive attractor-repellers 104. Although Di, D2, D3, and D4 are described above with reference to the ion source 102 and attractor-repeller 104 of the phased array electrostatic thruster 100 of FIG. 2, it should be understood that corresponding distances may be defined in a similar manner for attractor-repeller electrodes and ion sources of other embodiments described herein (e.g., attractor-repellers 704, 804, 1004, 1104, 1204, 1304, 1504 and ion sources 702, 802, 1002, 1102, 1202, 1332).

[0070] As shown in FIGS. 2, 4A, and 4B, the phased array electrostatic thruster 100 includes a reflector, shown as ion reflector 108, upstream of the ion source 102 at the inlet to the phased array electrostatic thruster 100. The ion reflector 108 is configured to reduce reverse repelling (e.g., reverse thrust) associated with operation of the ion source 102.-13- 4919-8285-9408Atty. Dkt. No.: 143360-0106Examples of reflectors are provided in Dutch Patent Application No. 2036471, filed December 8, 2023. In embodiments in which the phased array electrostatic thruster 100 does not include the ion source 102 at the inlet, the first stage attractor-repeller 104 may function only as a repeller during operation to push charged particles toward later stages.

[0071] The power system 110 (which may also be referred to as a control system) is electrically coupled to the ion source 102 and the attractor-repeller 104 (e.g., a body of the attractor-repeller 104). The power system 110 includes a power supply 112 (e.g., a direct current (DC) power supply) that is configured to generate a voltage potential between the ion source 102 and the attractor-repeller 104 in at least one of the stages 101. In some embodiments, the power supply 112 includes a variable voltage power supply. In other embodiments, the power supply 112 includes a pulsed power supply. For example, the power supply 112 may include a pulsed DC power supply, such as a nanosecond pulse power supply, that is configured to limit the duration of operation of the power supply 112 at a rated voltage (e.g., about 20 kV to 60 kV, 5 kV to 150 kV, 20 kV to 150 kV, 150 kV to 200 kV, or any value between and including the foregoing values, including about 20 kV, about 30 kV, about 40 kV, about 50 kV, about 60 kV, about 70 kV, about 80 kV, about 90 kV, about 100 kV, about 110 kV, about 120 kV, about 130 kV, about 140 kV or about 150 kV, or greater).

[0072] In some embodiments, the power supply 112 is configured to limit the time intervals during which power is supplied (within the rated voltage) to the ion source 102 and the attractor-repeller 104 to time scales that are less than the time required for arcing between the ion source 102 and the attractor-repeller 104 (e.g., having an ON time that is shorter than the time required for an arc to form). Such an arrangement can reduce the risk of dielectric breakdown between the ion source 102 and the attractor-repeller 104. In some embodiments, the power system 110 additionally or alternatively includes a current limiter, such as a resistor rated to voltages of above rated voltage for the respective stage.

[0073] In some embodiments, each of the stages 101 includes its own individual power supply 112, shown as first stage power supply 112a and second stage power supply 112b. In other embodiments, the power system 110 includes a single power supply 112 with-14- 4919-8285-9408Atty. Dkt. No.: 143360-0106multiple variable voltage / switchable outputs (e.g., one output for each of the stages 101). In the embodiment of FIG. 2, each of the power supplies 112 is attached to a common electrical potential, shown as ground 114.

[0074] In some embodiments, and as shown, the power system 110 also includes sensors and a controller 116 that is configured to coordinate operation and allocation of power to each of the stages 101 based on information received from the sensors. In some embodiments, each of the stages 101 includes one, or a combination of, a current sensor 118 configured to generate sensor data indicative of a power output to the respective stage 101; and at least one charged particle sensor, shown as electric field sensor 120 and flow sensor 122, configured to generate sensor data indicative of the arrival and / or the presence of charged particles relative to various locations along the attractor-repeller 104.

[0075] In some embodiments, the current sensor 118 forms part of a current sensing circuit for the respective stage 101. In some embodiments, each of the stages 101 includes its own current sensing circuit, which can enable more accurate control over power allocation to the stages 101. Such an arrangement can also facilitate identification of issues associated with individual stages 101 during operation (e.g., issues associated with loss of power to individual stages 101, etc.).

[0076] In some embodiments, as indicated above, the power system 106 also includes a charged particle sensor. The charged particle sensor may include an electric field sensor 120 configured to monitor changes in the electrical field in the airflow stream passing through the phased array electrostatic thruster 100, such as across the attractor-repeller 104 (e.g., a change in current caused by arriving charged particles), and / or a flow sensor 122 such as an anemometer, pitot tube, or ultrasonic flow sensor that is configured to generate sensor data indicative of the actual flow of the fluid / gas through the phased array electrostatic thruster 100.

[0077] In embodiments including an electric field sensor 120, the electric field sensor 120 may be positioned relative to the attractor-repeller 104 in an area at which, when crossed by the charged particles, substantially reduces the thrust associated with operation of the attractor-repeller 104 in a single operating mode (e.g., when the attractor-repeller 104 is -15- 4919-8285-9408Atty. Dkt. No.: 143360-0106operated as an attractor to pull in charged particles forward of the attractor-repeller 104, such as from a preceding stage of the attractor-repeller 104). For example, and as shown in FIG. 2, the electric field sensor 120 may be positioned at a leading edge of the uninsulated portion of the attractor-repeller 104, shown as transition line 124. Such an arrangement can significantly improve the thrust provided by the phased array electrostatic thruster 100 by enabling controlled switching of the operating mode based on the actual location of the charged particles relative to the attractor-repeller 104.

[0078] The controller 116 is communicably coupled to the electric field sensor 120 and the flow sensor 122 and is configured to coordinate operation of each of the stages 101 (e.g., to control the voltage potential applied to each stage 101 of the phased array electrostatic thruster 100) based on the sensor data received from the electric field sensor 120 and the flow sensor 122.

[0079] In the embodiment of FIG. 2, the controller 116 is configured to determine a phase of each of the stages 101 based on the sensor data (e.g., whether each respective stage 101 should be providing an attractive force, a repelling force, and / or generating charged particles (which depends on the voltage potential between stages 101), or whether the respective stage 101 should be deactivated based on the sensor data), and to control the output voltage potential of the power supply 112 and / or power output from a shared power supply, or multiple power supplies, based on the phases. In some embodiments, the power outputs of one or more stages 101 are implemented as high-impedance outputs during selected portions of the waveform such that the corresponding attractor-repellers 104 and / or ion sources 102 can float electrically when desired.

[0080] For example, referring to FIG. 3, an example waveform 200 that may be implemented by the controller 116 (see also FIG. 2) to generate thrust using the four-stage phased array electrostatic thruster 100 is shown, according to an embodiment. At the start of a first time interval 202, the controller 116 activates (e.g., applies a high voltage potential to) the ion source (e.g., the ion source 102) disposed at an inlet (e.g., the inlet 103) of the phased array electrostatic thruster 100 (e.g., the first stage ion source). At the same time, the controller 116 maintains the first stage attractor-repeller (e.g., the attractor-repeller 104)-16- 4919-8285-9408Atty. Dkt. No.: 143360-0106that is immediately downstream from the first stage ion source at a different voltage potential from the first stage ion source so that the first stage attractor-repeller functions as an attractor to attract ions from the first stage ion source.

[0081] Referring to FIG. 4A, an approximation of the electric field, shown as electrical field lines 126, associated with the first time interval 202 is shown, according to an embodiment. The voltage potential between the first stage ion source 102a and the first stage attractorrepeller 104a creates a cloud of charged particles 128 in the first stage 101a, which are pulled toward the first stage attractor-repeller 104a during the first time interval 202. The first stage attractor-repeller 104a is also pulled toward the charged particles 128, resulting in a thrust vector 130 oriented opposite the direction of movement of the charged particles 128 through the phased array electrostatic thruster 100. The cloud of charged particles 128 contains an electrical charge, which can be positive or negative depending on the polarity of the ion source 102. In some embodiments, in the first phase, the controller 116 may apply a first voltage potential between the first stage ion source 102a and the first stage attractor-repeller 104a such that the polarity of the first stage attractor-repeller 104a is opposite to the polarity of the charged particles 128 generated by the first stage ion source 102a, thereby causing the first stage attractor-repeller 104a to operate in an attractor operating mode. In some embodiments , in a subsequent, second phase, the controller 116 may apply a second voltage potential such that the first stage attractor-repeller 104a has substantially the same polarity as the charged particles 128, thereby causing the first stage attractor-repeller 104a to operate in a repeller operating mode that repels the charged particles 128 toward the second stage attractor-repeller 104b of the second stage 101b downstream from the first stage 101a.

[0082] The controller 116 monitors the location of the charged particles 128 passing across the first stage attractor-repeller 104a based on sensor data received from the electric field sensor 120 and / or the flow sensor 122. The controller 116 determines when the next phase shift and / or adjustment is to occur between the stages 101 based on the location of the charged particles 128 and to maintain thrust in the same direction during operation.|0083] Returning to FIG. 3, at the end of the first time interval 202 (e.g., when the charged-17- 4919-8285-9408Atty. Dkt. No.: 143360-0106particles cross a threshold region of the first stage attractor-repeller 104a of FIG. 4 A), and responsive to sensor data indicating the presence and / or the location of charged particles at the threshold region, the controller 116 deactivates the first stage ion source 102a and activates (e.g., applies a high voltage to) the second stage ion source 102b that is immediately downstream from the inlet ion source, so that the first stage attractor-repeller 104a functions as a repeller and the second stage attractor-repeller 104b functions as an attractor.

[0084] Referring to FIG. 4B, an approximation of the electrical field lines 126 (e.g., an approximation of the electric field) associated with the second time interval 204 is shown, according to an embodiment. During the second time interval 204, the matching voltage between the first stage attractor-repeller 104a and the second stage ion source 102b repels charged particles 128 away from the trailing edge of the first stage attractor-repeller 104a and toward the second stage attractor-repeller 104b. At the same time, the voltage potential between the second stage ion source 102b and the second stage attractor-repeller 104b creates another cloud of charged particles 128 that supplements / replenishes the charged particles 128 passing between the first and second stage attractor-repellers 104a and 104b. As shown in FIG. 3, this process continues with each subsequent stage during operation as the cloud of charged particles 128 moves through the phased array electrostatic thruster 100.

[0085] Although FIG. 3 shows approximately equal time increments of operation of the power outputs for each of the phases, it should be understood that the time increments may differ from one another in various embodiments (e.g., at startup, etc.). For example, in embodiments in which the power system 110 includes the electric field sensor 120 and / or the flow sensor 122, the controller 116 may be configured to activate the second stage 101b based on sensor data indicative of the charged particles 128 reaching an uninsulated region of the first stage attractor-repeller 104a (e.g., a region of the first stage attractor-repeller 104a not insulated by the insulator 106), as described above.

[0086] In some embodiments, the controller may also be configured to operate the phased array electrostatic thruster 100 in reverse (e.g., by operating the DC power supplies to run-18- 4919-8285-9408Atty. Dkt. No.: 143360-0106the phase sequence in reverse) with the same or a modified waveform, to provide reversed thrust.

[0087] Referring again to FIG. 2, in other embodiments, including embodiments that do not include separate sensors along the phased array electrostatic thruster 100, the controller 116 may be configured to control allocation of power to each of the stages 101 based on a combination of (i) speed measurements or airflow measurement of a vehicle supporting the phased array electrostatic thruster 100 or the flow sensor 122, and (ii) the geometry of the thruster (e.g., a distance between each of the stages 101, a length of each attractor-repeller 104, etc.). In still further embodiments, the controller 116 may be configured to control allocation of power to each of the stages 101 using a lookup table and / or an algorithm stored in memory including a list of control periods (e.g., durations of power allocation to each stage, power levels, etc.) that are associated with different fixed or variable flow rates of fluid through the phased array electrostatic thruster 100 (e.g., by use of a timer).

[0088] It should be understood that various different waveforms may be implemented by the controller 116. For example, referring to FIG. 5, a waveform 300 is shown in which the controller 116 maintains overlapping voltage potentials between adjacent stages 101 for a threshold period 306 after switching phases. In such arrangements, the preceding stage can continue to repel the charged particles for a longer time period as compared to the waveform 200 in FIG. 3, which can be beneficial in certain applications.

[0089] Referring to FIG. 6, a waveform 400 is shown in which the controller 116 controls the power outputs to more fluidly ramp the voltage potential for adjacent stages 101 during switching, which can result in a shorter ion generation period. In such a shorter ion generation period, the high voltage potential moves more smoothly and dynamically between adjacent stages 101 during operation. This in turn can reduce pulsations and / or abrupt changes in the thrust vector during operation in certain configurations. In some embodiments, the power output changes in a substantially linear fashion as shown in FIG. 6. In other embodiments, the power output changes non -linearly (e.g., according to a curvilinear function) between adjacent stages 101. In some embodiments, the power output changes at different linear or non-linear rates between different adjacent stages 101. For-19- 4919-8285-9408Atty. Dkt. No.: 143360-0106example, between the first stage 101a and the second stage 101b, the power output may change according to a first linear or non-linear rate, between the first stage 101a and the second stage 101b, the power output may change according to a second linear or non-linear rate that is greater or less than the first linear or non-linear rate, between the second stage 101b and a third stage, the power output may change according to a third linear or nonlinear rate that is greater or less than the first and / or second linear or non-linear rates, and so on.

[0090] Referring to FIG. 7, a waveform 500 is shown in which the controller 116 controls the power outputs to spread out the voltage potential across multiple stages 101 simultaneously (e.g., so that multiple stages together act as a single attractor / repeller stage). Such an arrangement can increase the length of the electric field between where the ion cloud is generated and attracted or repelled, which can be used to provide greater voltage potentials between the ion source and the opposite polarity stage without resulting in dielectric breakdown. In some embodiments, the voltage potential difference between the ion source and the nearest following attractor-repeller (e.g., between the first stage ion source 102a and the first stage attractor-repeller 104a in FIG. 4A) may be less than (e.g., may be maintained lower than) the voltage potential difference between the ion source and a more distant attractor-repeller, such as the second following attractor-repeller (e.g., between the first stage ion source 102a and the second stage attractor-repeller 104b in FIG. 4A). In other words, the controller 116 is configured to distribute a voltage potential associated with a respective phase across at least two adjacent thruster stages 101. In such embodiments, the controller 116 controls the power supplies 112 such that, during the respective phase, a first voltage difference between the ion source 102 and a first attractor-repeller 104 nearest the ion source 102 is less than a second voltage difference between the ion source 102 and a second attractor-repeller 104 that is more distant from the ion source 102 than the first attractor-repeller 104. In this manner, a higher total voltage potential can be applied across multiple stages 101 without resulting in dielectric breakdown (arcing) between the ion source and the attractor-repeller and / or neighboring attractor-repellers.

[0091] Referring to FIG. 8, a perspective view of a phased array electrostatic thruster 600 that may be formed using the phased array electrostatic thruster 100 of FIG. 2 is shown,-20- 4919-8285-9408Atty. Dkt. No.: 143360-0106according to an embodiment. In some embodiments, and as shown, each stage 101 of the phased array electrostatic thruster 600 includes four separate attractor-repellers 104 vertically arranged in a stack, each coupled to a respective ion source 102. In some embodiments, the phased array electrostatic thruster 600 is configured to use the same voltage polarity between the ion source and the attractor-repeller at each stage. In some embodiments, within each stage 101, the ion sources 102 and their corresponding attractor-repellers 104 share the same voltage polarity relationship. In other words, the polarity of the ion source 102 relative to the attractor-repeller 104 is the same for each pair within a respective stage 101. Such an arrangement can prevent attraction between the charged particles 128 passing across the attractor-repellers 104 within individual stages 101 and can reduce the risk of neutralization of the charged particles 128 due to intermixing between the stages 101 in the streamwise direction.

[0092] In some embodiments, the voltage polarity is also the same for all of the ion source and attractor-repeller pairs within each stage.

[0093] In some embodiments, the controller 116 may be configured to leave out every other last stage 101 of the electrostatic thruster during operation (between the upper and lower sections of the phased array electrostatic thruster 600) so that charged particles 128 leaving every other section in the last stage 101 are of opposite polarities. Such an arrangement can allow the charged particles 128 to intermix past the outlet of the phased array electrostatic thruster 600, thereby neutralizing the output fluid. A similar effect can be produced by insulating adjacent sections of the phased electrostatic thruster array (e.g., upper and lower sections as shown in FIG. 8), resulting in insulated and / or spaced apart thrusters with opposite polarities that eject charged particles 128 along a common outlet plane.

[0094] It should be understood that the number of attractor-repellers 104 within each stage 101, and / or spacing between adjacent attractor-repellers 104 within each stage 101 and / or between stages 101 may be different in various embodiments. The arrangement of the ion source 102 relative to the attractor-repeller electrodes may also be different in various embodiments.

[0095] While FIGS. 2-8 described herein may reference first and second stage components -21- 4919-8285-9408Atty. Dkt. No.: 143360-0106(e.g., the first stage ion source 102a and the second stage ion source 102b, the first stage attractor-repeller 104a and the second stage attractor-repeller 104b, and the first stage power supply 112a and the second stage power supply 112b), it should be understood that corresponding third and fourth stage components, shown as third stage ion source 102c and fourth stage ion source 102d, third stage attractor-repeller 104c and fourth stage attractorrepeller 104d, and third stage power supply 112c and fourth stage power supply 112d, may be implemented and operated in the same or a substantially similar manner, including between the second stage 101b and the third stage 101c and between the third stage 101c and the fourth stage lOld.Thruster with Centralized Ion Source

[0096] Referring to FIG. 9, a phased array electrostatic thruster 700 that includes centralized ion sources 702 arranged between attractor-repellers 704 (e.g., a pair of attractor-repellers 704) within the same stage 701 is shown, according to an embodiment. The attractor-repellers 704 may be the same as or substantially similar to the attractorrepellers 104 described above with reference to FIGS. 2-8. The ion sources 702 are disposed vertically between pairs of the attractor-repellers 704 within the same stage 701. In the embodiment of FIG. 9, the ion sources 702 are spaced vertically apart from the attractor-repellers 704 within the same stage 701 by an approximately equal distance (e.g., above and below the attractor-repellers 704 as shown in FIG. 9), which can reduce vertical components of the thrust vector (e.g., the thrust vector 130) between the adjacent attractorrepellers 704 within the same stage 701. In other embodiments, the distances between the ion source 702 and adjacent attractor-repellers 704 within the same stage 701 may be different. As shown in FIG. 9, the ion sources 702 of adjacent stages 701 (e.g., the first stage ion source 702a and the second stage ion source 702b, the second stage ion source 702b and a third stage ion source, the third stage ion source and a fourth stage ion source, etc.) are spaced apart from each other by a distance Ds that extends substantially parallel to the flow direction.

[0097] In some embodiments, the ion source 702 includes a conductive wire. In the embodiment of FIG. 9, the ion source 702 for each stage 701 includes multiple conductive-22- 4919-8285-9408Atty. Dkt. No.: 143360-0106wires spaced apart from one another along a flow direction through the phased array electrostatic thruster 700. In some embodiments, the conductive wires are arranged in an array that extends substantially parallel to the flow direction. In other embodiments, at least one ion source 702 includes a DBD ion source, a knife edge electrode(s), a needle electrode(s), a spiral electrode(s), or another type of ion source now known or hereinafter developed.

[0098] Referring to FIGS. 10A-10B, an approximation of the electric field, shown as electrical field lines 726, associated with two different phases of operation of the phased array electrostatic thruster 700 is shown, according to an embodiment. In a first phase of operation (e.g., during a first time interval, an ion cloud generation phase and / or mode of operation), as shown in FIG. 10A, the controller 716 controls a first stage power supply 712a (e.g., a first power supply, a first power output of a shared power supply, etc.) to generate a voltage potential between a first stage ion source 702a and the first stage attractor-repellers 704a on either side of (e.g., vertically above and below) the first stage ion source 702a. The voltage potential generates a cloud of charged particles 728 (e.g., a localized cloud) within the first stage 701a. The first stage ion source 702a is configured to supply the charged particles 728 responsive to the voltage potential between the first stage ion source 702a and the first stage attractor-repellers 704a on either side of the first stage ion source 702a.

[0099] In a second phase of operation (e.g., during a second time interval, an attractionrepulsion phase and / or mode of operation), as shown in FIG. 10B, the controller 716 controls the power supply 712 of both the first and second stages 701a and 701b to generate a voltage potential between (i) the charged particles 728 and (ii) both the first stage attractor-repeller 704a and second stage attractor-repeller 704b. In some embodiments, and as shown, the controller 716 is configured to control the first stage power supply 712a to maintain high voltage at the first stage ion source 702a, and to control the second stage power supply 712b to apply high voltage to the first stage attractor-repeller 704a, so as to repel the charged particles away from the first stage attractor-repeller 704a.

[0100] In the arrangement of FIG. 10B, the second stage power supply 712b applies a high-23- 4919-8285-9408Atty. Dkt. No.: 143360-0106voltage to both the first stage attractor-repeller 704a and the second stage ion source 702b at the same time, which causes generation of another cloud of charged particles 728 near the trailing edge of the second stage attractor-repeller 704b as the initial cloud of charged particles 728 moves through the phased array electrostatic thruster 700. The charged particles 728 mix as the controller 716 switches the power supplies 712 to the next phase of operation.

[0101] In the embodiment of FIG. 9 and FIGS. 10A-10B, the ion source 702 for each stage 701 is disposed within or near the uninsulated portion of the attractor-repellers 704 of each stage 701, which can increase the electrostatic forces between the ion source 702 and the attractor-repellers 704. In other embodiments, the attractor-repellers 704 may be uninsulated.

[0102] The arrangement of the ion source 702 within each stage 701 may be different in various embodiments. For example, referring to FIGS. 11 A and 1 IB, a phased array electrostatic thruster 800 is shown that includes an ion source 802 that extends across a larger area of the attractor-repellers 804 within each stage 701 as compared to FIG. 9. In other words, a length of the ion source 802 within each stage 701 along a flow direction is greater than a length of the ion source 702 described with reference to FIG. 9. In such an arrangement, the distance Ds between adjacent ion sources 702 in adjacent stages 701 is less than the distance Ds between adjacent ion sources 702 described with reference to FIG. 9. Such an arrangement can increase the number of charged particles 728 produced during operation.

[0103] While FIGS. 9-10B described herein may reference first and second stage components (e.g., the first stage 701a and the first and second stages 701b, the first stage ion source 702a and the second stage ion source 702b, the first stage attractor-repeller 704a and the second stage attractor-repeller 704b, and the first stage power supply 712a and the second stage power supply 712b), it should be understood that corresponding third and fourth stage components, shown as third stage 701c and fourth stage 70 Id, third stage ion source 702c and fourth stage ion source 702d, third stage attractor-repeller 704c and fourth stage attractor-repeller 704d, and third stage power supply 712c and fourth stage power-24- 4919-8285-9408Atty. Dkt. No.: 143360-0106supply 712d, may be implemented and operated in the same or a substantially similar manner, including between the second stage 701b and the third stage 701c and between the third stage 701c and the fourth stage 70 Id.

[0104] In such implementations, and as shown, the attractor-repellers 804 may be substantially covered with insulation, shown as insulator 806, across their entire length, which can ensure a more uniform electric pull on the ion source 802 during operation. In other words, the insulated length D2 of the attractor-repellers 804 may be greater than the insulated length D2 of the attractor-repellers 704. As shown in FIG. 1 IB, in some embodiments, the attractor-repellers 804 include an insulator that defines small openings 824 (e.g., perforations) along its length in the flow direction (e.g., along the insulated length D2 of the attractor-repellers 804), which can increase electrostatic pull between the charged particles 828 and the attractor-repellers 804 while, at the same time, substantially preventing discharge of the cloud of charged particles 828 passing across the attractor-repellers 804.

[0105] Referring to FIGS. 12A and 12B, an approximation of the electric field, shown as electrical field lines 826, associated with two different phases of operation of the phased array electrostatic thruster 800 is shown, according to an embodiment. The controller 816 is configured to control operation of the power supplies 812 in phases. In a first phase, as shown in FIG. 12 A, the controller 816 controls the first stage power supply 812a to apply a high voltage to the first stage ion source 802a in a similar manner as described with respect to the phased array electrostatic thruster 700 of FIG. 10A.

[0106] In a second phase of operation, as shown in FIG. 12B, the controller 816 maintains the high voltage potential of the first stage ion source 802a while at the same time controlling the second stage power supply 812b to apply high voltage potential to both the first stage attractor-repeller 804a and the second stage ion source 802b. This control algorithm is depicted schematically by the waveform 500 of FIG. 7. As shown in FIG. 12B, because the voltage potential on the first stage ion source 802a is similar to (or the same as) the first stage attractor-repeller 804a, the first stage ion source 802a stops producing ions. In embodiments in which the first stage ion source 802a includes a DBD ion source or other type of decoupled ion source, the controller 816 is configured to disable operation of the-25- 4919-8285-9408Atty. Dkt. No.: 143360-0106first stage ion source 802a at the beginning of the second phase.

[0107] As shown in FIG. 12B, during the second phase of operation, the controller 816 controls the power supplies 812 so that the first stage ion source 802a and the first stage attractor-repeller 804a function as repellers, which push the cloud of charged particles 828 toward the next / following stage 801. At the same time, the controller 816 controls the second stage power supply 812b to apply a high voltage to the second stage ion source 802b to produce additional charged particles 828.

[0108] Referring to FIG. 13, a perspective view of a phased array electrostatic thruster 900 that may be formed using the phased array electrostatic thruster 800 of FIGS. 12A and 12B is shown, according to an embodiment. The phased array electrostatic thruster 900 includes multiple individual layers of the phased array electrostatic thruster 800 of FIGS. 12A and 12B that are disposed on top of one another (e.g., along a vertical direction as shown in FIG.13). Such an arrangement can reduce the overall package size relative to the phased array electrostatic thruster 600 of FIG. 8 under certain circumstances. The number and arrangement of adjacent layers of the phased array electrostatic thruster 900 may be different in various embodiments.

[0109] While FIGS. 11 A-12B described herein may reference first and second stage components (e.g., the first stage ion source 802a and the second stage ion source 802b, the first stage attractor-repeller 804a and the second stage attractor-repeller 804b, and the first stage power supply 812a and the second stage power supply 812b), it should be understood that corresponding third and fourth stage components, shown as third stage ion source 802c and fourth stage ion source 802d, third stage attractor-repeller 804c and fourth stage attractor-repeller 804d, and third stage power supply 812c and fourth stage power supply 812d, may be implemented and operated in the same or a substantially similar manner.

[0110] Referring to FIG. 14, another arrangement of a phased array electrostatic thruster 1000 that includes centralized ion sources 1002 is shown, according to an embodiment. The phased array electrostatic thruster 1000 includes attractor-repellers 1004 that are arranged end-to-end in an enclosed arrangement within each stage 1001. In the embodiment of FIG.14, the attractor-repellers 1004 are arranged in a hexagonal arrangement within each stage -26- 4919-8285-9408Atty. Dkt. No.: 143360-01061001. In other embodiments, the shape formed by the attractor-repellers 1004 normal to the flow direction may be different (e.g., triangular, square, circular, etc.). As shown in FIG.14, the phased array electrostatic thruster 1000 includes ion sources 1002 that are disposed within a cavity formed by the attractor-repellers 1004 in each stage 1001, so that each attractor-repeller 1004 surrounds (e.g., circumscribes) a respective ion source 1002. In some embodiments, the ion sources 1002 are disposed at a central position within the cavity, so that the ion sources 1002 are colinear with a central axis of the cavity defined by the attractor-repellers 1004. In the embodiment of FIG. 14, the ion sources 1002 include needle electrodes 1008 that include multiple conductive needle-like (acicular) extensions (e.g., wires, extenders, etc.) spaced apart from one another that are oriented radially toward the attractor-repellers 1004. Such an arrangement can increase space utilization of the cavity defined by the attractor-repellers 1004 within each stage 1001, which can increase generation of charged particles during operation. In other embodiments, the ion source 1002 includes a spiral electrode, or another electrode configuration. As shown in FIG. 14, the attractor-repellers 1004 are electrically insulated (e.g., includes at least a partial insulation layer) by an electrical insulation layer (e.g., a dielectric material), shown as insulator 1006, along at least a portion of the outer surface thereof. In some embodiments, the insulator 1006 is applied along an interior portion of the attractor-repeller 1004 that faces toward the ion source 1002 and an exterior portion of the attractor-repeller 1004 that faces away from the ion source 1002.Single Wall Multi-Stage Thruster

[0111] Referring to FIG. 15, a phased array electrostatic thruster 1100 is shown in which the attractor-repellers 1104 of each stage 1101 are integrated into a shared wall 1128, according to an embodiment. In some embodiments, and as shown, the wall 1128 extends (e.g., spans) across all stages 1101 of the phased array electrostatic thruster 1100. Such an arrangement can reduce manufacturing complexity of the phased array electrostatic thruster 1100 and can also reduce flow losses through the electrostatic thruster in some embodiments.

[0112] In some embodiments, the wall 1128 is an insulated wall that includes an insulator-27- 4919-8285-9408Atty. Dkt. No.: 143360-0106extending across the outer surfaces of the wall 1128. The insulator may be arranged so that the dielectric strength of the insulator decreases along a flow direction through the phased array electrostatic thruster 1100, which can extend the duration and improve uniformity of the electrostatic force between the charged particles and the attractor-repellers 1104 during operation.

[0113] In some embodiments, the insulator and / or the wall 1128 includes openings 1130 disposed between adjacent stages 1101 of the attractor-repellers 1104. Such an arrangement can increase the electrostatic forces at the trailing edge of individual stages 1101 while reducing the amount of discharge of the cloud of charged particles at the trailing edge of the attractor-repellers 1104.

[0114] In the embodiment of FIG. 15, the ion sources 1102 are centralized ion sources 1102 that are arranged between (e.g., vertically between as shown in FIG. 15) adjacent attractorrepellers 1104 within each stage 1101. In other embodiments, the arrangement of the ion source(s) 1102 may be different. For example, at least one of the ion sources 1102 may be placed within the wall 1128 and between adjacent stages 1101 of the attractor-repellers 1104.

[0115] The use of a shared wall thruster can also enable redirection of airflow passing through the phased array electrostatic thruster. For example, referring to FIG. 16, a phased array electrostatic thruster 1200 is shown that is configured to implement the venturi effect on airflow passing through the thruster. The shared walls 1228 across different layers of the thruster converge toward one another near the trailing edge of the shared walls 1228, so that a first distance 1230 between adjacent ones of the shared walls 1228 at a leading edge (e.g., an inlet) of the phased array electrostatic thruster 1200 is greater than a second distance 1232 between the adjacent ones of the shared walls 1228 at a trailing edge (e.g., an outlet) of the phased array electrostatic thruster 1200.

[0116] In some embodiments, the distance between the shared walls 1228 reduces gradually (e.g., continuously or semi-continuously) along the flow direction through the phased array electrostatic thruster 1200. Such an arrangement can accelerate the flow of fluid through the phased array electrostatic thruster 1200 during operation, which may be beneficial in -28- 4919-8285-9408Atty. Dkt. No.: 143360-0106various embodiments. In the embodiment of FIG. 16, the distance between shared walls 1228 decreases along sections of the shared walls 1228 that are disposed between adjacent stages 1201 of the attractors-repellers 1204. Such an arrangement can ensure a more uniform electrostatic force between the ion sources 1202 and the attractors-repellers 1204 in some configurations. In other embodiments, the arrangement of the shared walls 1228 may be different.Thruster with DBD Integrated Ion Source-Attractor-Repeller

[0117] Referring to FIG. 17, a phased array electrostatic thruster 1300 is shown that includes an ion source formed at least partially by an attractor-repeller electrode 1304, according to an embodiment. The attractor-repeller electrode 1304 is configured to function as a portion of the ion source in a first phase of operation and as an attractor-repeller in other phases of operation. Each stage of the phased array electrostatic thruster 1300 includes the attractor-repeller electrode 1304, an emitter electrode 1332, an alternating current (AC) power supply 1334, a DC power supply 1336, and a capacitor 1338.

[0118] The attractor-repeller electrode 1304 and the emitter electrode 1332 together form the ion source for the phased array electrostatic thruster 1300. In some embodiments, and as shown, the attractor-repeller electrode 1304 includes an insulator 1306 covering the outer surface thereof, which may be arranged as described with respect to any of the other embodiments referred to herein. In the embodiment of FIG. 17, the attractor-repeller electrode 1304 is electrically connected to a positive terminal of the DC power supply 1336.

[0119] In some embodiments, and as shown, the emitter electrode 1332 is one of multiple emitter electrodes 1332 that are arranged in an array that extends across a portion of the outer surface of the attractor-repeller electrode 1304. The emitter electrodes 1332 each extend from a support structure of the phased array electrostatic thruster 1300 in a lateral direction (e.g., into and out of the page as shown in FIG. 17). As shown in FIG. 17, the emitter electrodes 1332 are each spaced an approximately equal distance away from the outer surface of the attractor-repeller electrode 1304 (e.g., by a distance D7).

[0120] In some embodiments, the emitter electrodes 1332 form part of a surface integrated-29- 4919-8285-9408Atty. Dkt. No.: 143360-0106ion source that can be applied directly to the attractor-repeller. In some embodiments, the surface integrated ion source includes a support structure and multiple electrodes that are formed onto the support structure. The support structure is made from a dielectric material. For example, the support structure may include a flexible printed circuit board (PCB) made from polyimide (PI), fluorinated ethylene propylene (FEP), or Teflon (Polytetrafluoroethylene (PTFE)), or another dielectric material. The surface integrated ion source may be formed using a flexible PCB manufacturing process that disposes copper onto the dielectric material and so that the dielectric material insulates the electrode(s) from the outer surface of the flexible PCB. The flexible PCB may then be applied directly onto the attractor-repeller (e.g., via a dielectric adhesive and / or by wrapping the flexible PCB around the attractor-repeller) so the flexible PCB engages the attractor-repeller. Such an implementation can, beneficially, reduce manufacturing complexity and ensure a more consistent emitter electrode spacing across the length of the attractor-repeller.

[0121] In the embodiment of FIG. 17, the emitter electrodes 1332 are disposed along an insulated portion of the attractor-repeller electrode 1304 (e.g., a portion of the attractorrepeller electrode 1304 insulated by the insulator 1306) and are spaced apart from an uninsulated portion of the attractor-repeller electrode 1304 to avoid dielectric breakdown. In some embodiments, the distance D? (e.g., a minimum distance, a shortest distance, etc.) between the emitter electrodes 1332 and the outer surface of the attractor-repeller electrode 1304 is less than or equal to half of a distance De between the uninsulated portion of the attractor-repeller electrode 1304 (e.g., a leading edge of the uninsulated portion of the attractor-repeller electrode 1304) and the nearest emitter electrode 1332 along the streamwise direction. Such an arrangement can prevent dielectric breakdown of the fluid between the emitter electrodes 1332 and the attractor-repeller electrode 1304. In some embodiments, and as shown, the emitter electrodes 1332 include two sets of emitter electrodes 1332 disposed on opposing sides (e.g., upper and lower sides as shown in FIG.17) of the attractor-repeller electrode 1304. Such arrangements can significantly increase the number of charged particles produced by the ion source. In other embodiments, the location of the emitter electrodes 1332 may be different.

[0122] The AC power supply 1334 is configured to apply an alternating voltage to the-30- 4919-8285-9408Atty. Dkt. No.: 143360-0106emitter electrodes 1332 during operation. In some embodiments, the AC power supply 1334 is electrically coupled to a common voltage potential, shown as ground 1314, which can be shared with the DC power supply 1336 in various embodiments.

[0123] The capacitor 1338 is disposed between, and electrically couples, the AC power supply 1334 to the emitter electrodes 1332. The capacitor 1338 allows the voltage of the emitter electrodes 1332 to float with changes in the voltage of the attractor-repeller electrode 1304, which can reduce the risk of dielectric breakdown between the emitter electrodes 1332 and the attractor-repeller electrode 1304 during switching between phases. It should be understood that, in various embodiments described herein, the high voltage phase outputs may be of high impedance at specific moments in the wave pattern, which can maintain the attractor-repellers and / or the emitters floating electronically whenever desired.

[0124] The phased array electrostatic thruster 1300 is configured such that, during operation of the AC power supply 1334, the combination of the emitter electrodes 1332 and the attractor-repeller electrode 1304 function as an ion source for the respective stage of the phased array electrostatic thruster 1300. In such an arrangement, AC voltage can be applied to the emitter electrodes 1332 to produce ions, for example, based on the principle of DBD.

[0125] In some embodiments, the AC power supply 1334 is configured to apply a voltage to the emitter electrodes 1332 within a range between 0.1-5 kV at a frequency within a range of about 10 kHz to 100 kHz, which can produce a large ion cloud while avoiding dielectric breakdown at various size ranges of the phased array electrostatic thruster 1300. In other embodiments, the AC power supply 1334 may be configured to apply different voltages at the same or different frequencies.

[0126] In some embodiments, the phased array electrostatic thruster 1300 also includes a controller 1316 that is configured to control operation of the AC power supply 1334 and the DC power supply 1336 for each of the respective stages during operation.

[0127] Referring to FIG. 18, an electric field diagram including an approximation of the electric field, shown as electrical field lines 1326, for the phased array electrostatic thruster-31- 4919-8285-9408Atty. Dkt. No.: 143360-01061300 of FIG. 17 is shown during at least one phase of operation, according to an embodiment. In the phase shown, the controller 1316 activates the ion source by controlling a second stage AC power supply 1334b to apply an alternating voltage to the second stage emitter electrodes 1332b. In response, the ion source produces / supplies a cloud of charged particles 1328 in the area surrounding the second stage attractor-repeller electrode 1304b (which operates in combination with the second stage emitter electrodes 1332b as the ion source for the phased array electrostatic thruster 1300). At the same time, the controller 1316 controls the third stage DC power supply 1336c to apply opposite electrical high voltage potential to the third stage attractor-repeller electrode 1304c as the ion source, which attracts the cloud of charged particles 1328 toward the third stage attractor-repeller electrode 1304c (and vice versa).

[0128] In such an arrangement, the controller 1316 controls the third stage DC power supply 1336c to operate the third stage attractor-repeller electrode 1304c as an attractor. In some embodiments, and as shown, the controller 1316 is also configured to control a DC power supply for the attractor-repeller of at least one proceeding stage (e.g., the first stage DC power supply 1336a as shown in FIG. 18) to apply the same (e.g., equal) voltage potential as the ion source, which acts to repel the charged particles 1328 from the ion source toward later stages 1301 (e.g., toward the third stage attractor-repeller electrode 1304c, etc.).

[0129] In some embodiments, the controller 1316 is also configured to control the first stage DC power supply 1336a to operate the first stage attractor-repeller electrode 1304a as a repeller. For example, during the phase shown in FIG. 18, the controller 1316 is configured to operate the first stage DC power supply 1336a to apply a high voltage potential to the first stage attractor-repeller electrode 1304a that is the same as or similar to the voltage of the charged particles 1328 produced by the ion source. Accordingly, in a first phase, the controller 1316 operates the alternating current power supply 1334b to apply alternating voltage to the second stage emitter electrodes 1332b such that the second stage emitter electrodes 1332b and the associated attractor-repeller electrode 1304b together generate the cloud of charged particles 1328. In a subsequent, second phase, the controller 1316 operates the DC power supplies 1336 to supply a direct current voltage of opposite-32- 4919-8285-9408Atty. Dkt. No.: 143360-0106polarity to a downstream attractor-repeller electrode 1304c to attract the cloud of charged particles 1328, and to supply a direct current voltage of substantially the same polarity as the cloud of charged particles 1328 to the upstream attractor-repeller electrode 1304b so that the upstream attractor-repeller electrode 1304b repels the cloud of charged particles 1328 toward the downstream stage.

[0130] Referring to FIG. 19, an example waveform 1400 that can be implemented by the controller 1316 of FIG. 18 is shown, according to an embodiment.

[0131] It should be understood that the arrangement of the phased array electrostatic thruster 1300 described with reference to FIG. 18 can also be implemented in other array configurations. For example, such an arrangement of emitter electrodes and attractorrepeller electrodes can also be implemented using the shared wall configurations described with reference to FIGS. 15 and 16, according to various embodiments.

[0132] Referring to FIG. 20, a phased array electrostatic thruster 1500 that can be formed using individual stages of the phased array electrostatic thruster 1300 is shown, according to an embodiment. The phased array electrostatic thruster 1500 includes attractor-repellers 1504 that are arranged end-to-end in an enclosed arrangement within each stage 1501. In the embodiment of FIG. 20, the attractor-repellers 1504 are arranged in a hexagonal arrangement within each stage. In other embodiments, the shape formed by the attractorrepellers 1504 normal to the flow direction may be different (e.g., triangular, square, circular, etc.). In some embodiments, and as shown, multiple ones of the phased array electrostatic thruster 1300 may be connected (e.g., chained together), with repeating phases that are shared between every / / th stage 1501 in series along the chain.

[0133] Referring to FIG. 21, a phased array electrostatic thruster 1600 is shown that includes multiple ones of the phased array electrostatic thrusters 1500 of FIG. 20 stacked side-by-side (e.g., along a lateral direction, along a vertical direction, etc.), in addition to a streamwise direction, which can increase the overall thrust provided by the system. The ion polarity applied by each phased array electrostatic thruster 1500 segment (each side-by-side segment) is identical to one another, as described above.-33- 4919-8285-9408Atty. Dkt. No.: 143360-0106

[0134] While FIGS. 17-21 described herein may reference first, second, and third stage components (e.g., the first stage attractor-repeller electrode 1304a, the second stage attractor-repeller electrode 1304b, and the third stage attractor-repeller electrode 1304c; the first stage emitter electrodes 1332a, the second stage emitter electrodes 1332b, and the third stage emitter electrodes 1332c; the first stage AC power supply 1334a, the second stage AC power supply 1334b, and the third stage AC power supply 1334c; and the first stage DC power supply 1336a, the second stage DC power supply 1336b, and the third stage DC power supply 1336c), it should be understood that corresponding fourth stage components, shown as fourth stage attractor-repeller electrode 1304d, fourth stage emitter electrodes 1332d, fourth stage AC power supply 1334d, and fourth stage DC power supply 1336d, may be implemented and operated in the same or a substantially similar manner.

[0135] In some embodiments, and as shown, each of the staged thruster arrays shares at least one attractor-repeller with an adjacent one of the staged thruster arrays, which can reduce system size, and can increase utilization of the ion clouds generated at each stage. As described above, the shape of each one of the enclosed staged thruster arrays can be different in various embodiments. In some embodiments, such as in a four-stage arrangement, or in larger arrangements with greater numbers of stages, the later stage electrodes can be omitted, as the later stages may not contribute as significantly to the overall thrust. For example, in an eight-stage phased electrostatic thruster arrangement, the emitter electrode for the 7th / 8thstages may be omitted, etc.

[0136] In some embodiments, the present disclosure also contemplates methods of operating any of the electrostatic thrusters described herein. By way of example, a method of operating a phased array electrostatic thruster may include applying, by a power system, a voltage potential between an ion source and at least one attractor-repeller of a first thruster stage to generate a cloud of charged particles, and controlling, by a controller, voltages applied to attractor-repellers of a plurality of thruster stages in a sequence of phases such that, in a first phase, an upstream attractor-repeller has a polarity opposite to the cloud of charged particles and operates in an attractor operating mode to attract the cloud of charged particles, and, in a subsequent phase, the upstream attractor-repeller has substantially the same polarity as the cloud of charged particles and operates in a repeller operating mode to-34- 4919-8285-9408Atty. Dkt. No.: 143360-0106repel the cloud of charged particles toward a downstream attractor-repeller operating in the attractor operating mode. In some embodiments, the method includes monitoring, by one or more sensors, at least one of an electric field or a flow condition associated with the cloud of charged particles and determining, by the controller, timing of the sequence of phases based on sensor data and a geometry of the plurality of thruster stages. It should be understood that the foregoing method can be implemented using any of the thruster configurations (e.g., the phased array electrostatic thruster 100, the phased array electrostatic thruster 600, the electrostatic thruster 700, the phased array electrostatic thruster 800, the electrostatic thruster 900, the phased array electrostatic thruster 1000, the electrostatic thruster 1100, the phased array electrostatic thruster 1200, the electrostatic thruster 1300, and / or the electrostatic thruster 1500) disclosed herein.

[0137] The present technology may also include, but is not limited to, the features and combinations of features recited in the following lettered paragraphs, it being understood that the following paragraphs should not be interpreted as limiting the scope of the claims as appended hereto or mandating that all such features must necessarily be included in such claims.A. An electrostatic thruster comprising:an ion source;a plurality of thruster stages, each thruster stage including:an attractor-repeller; anda power output coupled to the attractor-repeller; anda controller communicably coupled to the power output and configured to control the power output in phases to switch operation of the attractor-repeller between an attractor operating mode and a repeller operating mode.B. The electrostatic thruster of paragraph A, wherein a number of thruster stages is greater than a number of phases applied across the plurality of thruster stages.C. The electrostatic thruster of paragraphs A or B, wherein the attractor-repeller includes an insulator disposed across a portion of an outer surface thereof.-35- 4919-8285-9408Atty. Dkt. No.: 143360-0106D. The electrostatic thruster of any of paragraphs A-C, wherein the ion source is one of a plurality of ion sources that are coupled with respective ones of the attractorrepellers.E. The electrostatic thruster of paragraph D, wherein the plurality of ion sources each include an emitter.F. The electrostatic thruster of paragraph A, wherein each thruster stage includes a pair of attractor-repellers, the ion source disposed between the pair of attractorrepellers.G. The electrostatic thruster of paragraph A, wherein the attractor-repeller of at least one thruster stage of the plurality of thruster stages at least partially forms the ion source.H. The electrostatic thruster of paragraph A, wherein the attractor-repellers of adjacent thruster stages of the plurality of thruster stages are defined by a single wall.I. The electrostatic thruster of paragraph H, wherein an inlet of the plurality of thruster stages is larger than an outlet of the plurality of thruster stages.J. The electrostatic thruster of any of paragraphs A-I, wherein the controller is configured to reverse the phases.K. The electrostatic thruster of paragraph A, wherein the attractor-repeller is a first attractor-repeller of a first thruster stage of the plurality of thruster stages, and wherein controlling the power output in phases to switch operation of the first attractor-repeller between the attractor operating mode and the repeller operating mode includes:in a first phase, applying a first voltage potential between the ion source and the first attractor-repeller such that the first attractor-repeller has a polarity opposite to charged particles generated by the ion source, thereby controlling operation of the first attractor-repeller in the attractor operating mode; andin a second phase, applying a second voltage potential such that the first attractor-repeller has substantially the same polarity as the charged particles, thereby-36- 4919-8285-9408Atty. Dkt. No.: 143360-0106controlling operation of the first attractor-repeller in the repeller operating mode to repel the charged particles toward a second attractor-repeller of a second thruster stage of the plurality of thruster stages downstream from the first thruster stage.L. The electrostatic thruster of paragraph A, wherein the controller is configured to distribute a voltage potential associated with a respective phase across at least two adjacent thruster stages of the plurality of thruster stages such that a first voltage difference between the ion source and a first attractor-repeller nearest to and following the ion source is less than a second voltage difference between the ion source and a second attractorrepeller more distant from and following the ion source than the first attractor-repeller.M. An electrostatic thruster comprising:a plurality of attractor-repellers arranged along a flow direction; and an emitter electrode, the attractor-repellers and the emitter electrode together configured to form an ion source in at least one phase of operation.N. The electrostatic thruster of paragraph M, further comprising:a power output coupled to each attractor-repeller of the plurality of attractorrepellers; anda controller communicably coupled to the power output and configured to control the power output in phases to switch operation of respective ones of the attractorrepellers between an attractor and a repeller.O. The electrostatic thruster of paragraph N, further comprising:an alternating-current power supply coupled to the emitter electrode;a direct-current power supply coupled to an attractor-repeller of the plurality of attractor-repellers; anda capacitor electrically coupled between the alternating-current power supply and the emitter electrode such that a voltage of the emitter electrode floats with changes in voltage of the attractor-repeller.P. The electrostatic thruster of paragraph O, wherein the attractor-repeller is a first attractor-repeller, wherein the controller is configured to:-37- 4919-8285-9408Atty. Dkt. No.: 143360-0106in a first phase, operate the alternating-current power supply to apply alternating voltage to the emitter electrode such that the emitter electrode and the first attractor-repeller together generate a cloud of charged particles; andin a second phase, operate the direct-current power supply to supply direct-current voltage to (i) a second attractor-repeller of the plurality of attractor-repellers of a downstream stage to attract the cloud of charged particles and (ii) the first attractor-repeller of an upstream stage of substantially the same polarity as the cloud of charged particles such that the first attractor-repeller repels the cloud of charged particles toward the downstream stage.Q. The electrostatic thruster of any of paragraphs M-P, wherein an attractorrepeller of the plurality of attractor-repellers includes an insulator disposed across a portion of an outer surface thereof.R. The electrostatic thruster of paragraph Q, further comprising a plurality of emitter electrodes, including the emitter electrode, arranged along the insulator spaced from the attractor-repeller by a distance.S. The electrostatic thruster of paragraph R, wherein the distance is a first distance, and wherein the first distance is less than or equal to half of a second distance between an uninsulated portion of the attractor-repeller and a respective emitter electrode of the plurality of emitter electrodes nearest the uninsulated portion.T. An electrostatic thruster comprising:a plurality of stages arranged along a flow direction, each stage including:an attractor-repeller having an insulated upstream portion and an uninsulated downstream portion; anda plurality of emitter electrodes disposed on opposing sides of the attractor-repeller along the insulated upstream portion and spaced from an outer surface of the attractor-repeller; anda controller configured to control voltages applied to the attractor-repeller and the plurality of emitter electrodes in phases such that, in a first phase, the plurality of emitter electrodes and the attractor-repeller of a respective stage of the plurality of stages -38- 4919-8285-9408Atty. Dkt. No.: 143360-0106together generate a cloud of charged particles, and, in a second phase, the attractor-repeller of an upstream stage of the plurality of stages repels the cloud of charged particles while the attractor-repeller of a downstream stage of the plurality of stages attracts the cloud of charged particles.

[0138] As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0139] Various numerical values herein are provided for reference purposes only. Unless otherwise indicated, all numbers expressing quantities of properties, parameters, conditions, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term “approximately.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations. Any numerical parameter should at least be construed in light of the number reported significant digits and by applying ordinary rounding techniques. The term “approximately” when used before a numerical designation, e.g., a quantity and / or an amount including range, indicates approximations which may vary by ( + ) or ( - ) 10%, 5%, or 1%.

[0140] As will be understood by one of skill in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and-39- 4919-8285-9408Atty. Dkt. No.: 143360-0106upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0141] The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic.

[0142] The term “or,” as used herein, is used in its inclusive sense (and not in its exclusive sense) so that when used to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is understood to convey that an element may be either X, Y, Z; X and Y; X and Z; Y and Z; or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.

[0143] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” “upper,” “lower”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ-40- 4919-8285-9408Atty. Dkt. No.: 143360-0106according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0144] Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partial concurrence, unless specified differently above.

[0145] It is important to note that the construction and arrangement of the electrostatic thruster systems as shown in the various exemplary embodiments are illustrative only. Additionally, any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein. Although only one example of an element from one embodiment that can be incorporated or utilized in another embodiment has been described above, it should be appreciated that other elements of the various embodiments may be incorporated or utilized with any of the other embodiments disclosed herein.-41- 4919-8285-9408

Claims

Atty. Dkt. No.: 143360-0106WHAT IS CLAIMED IS:

1. An electrostatic thruster comprising:an ion source;a plurality of thruster stages, each thruster stage including:an attractor-repeller; anda power output coupled to the attractor-repeller; anda controller communicably coupled to the power output and configured to control the power output in phases to switch operation of the attractor-repeller between an attractor operating mode and a repeller operating mode.

2. The electrostatic thruster of claim 1, wherein a number of thruster stages is greater than a number of phases applied across the plurality of thruster stages.

3. The electrostatic thruster of claim 1 or claim 2, wherein the attractor-repeller includes an insulator disposed across a portion of an outer surface thereof.

4. The electrostatic thruster of claim 1, wherein the ion source is one of a plurality of ion sources that are coupled with respective ones of the attractor-repellers.

5. The electrostatic thruster of claim 4, wherein the plurality of ion sources each include an emitter.

6. The electrostatic thruster of claim 1, wherein each thruster stage includes a pair of attractor-repellers, the ion source disposed between the pair of attractor-repellers.

7. The electrostatic thruster of claim 1, wherein the attractor-repeller of at least one thruster stage of the plurality of thruster stages at least partially forms the ion source.

8. The electrostatic thruster of claim 1, wherein the attractor-repellers of adjacent thruster stages of the plurality of thruster stages are defined by a single wall.

9. The electrostatic thruster of claim 8, wherein an inlet of the plurality of thruster stages is larger than an outlet of the plurality of thruster stages.-42-4919-8285-9408Atty. Dkt. No.: 143360-010610. The electrostatic thruster of claim 1 or claim 2, wherein the controller is configured to reverse the phases.

11. The electrostatic thruster of claim 1, wherein the attractor-repeller is a first attractor-repeller of a first thruster stage of the plurality of thruster stages, and wherein controlling the power output in phases to switch operation of the first attractor-repeller between the attractor operating mode and the repeller operating mode includes:in a first phase, applying a first voltage potential between the ion source and the first attractor-repeller such that the first attractor-repeller has a polarity opposite to charged particles generated by the ion source, thereby controlling operation of the first attractor-repeller in the attractor operating mode; andin a second phase, applying a second voltage potential such that the first attractor-repeller has substantially the same polarity as the charged particles, thereby controlling operation of the first attractor-repeller in the repeller operating mode to repel the charged particles toward a second attractor-repeller of a second thruster stage of the plurality of thruster stages downstream from the first thruster stage.

12. The electrostatic thruster of claim 1 or claim 2, wherein the controller is configured to distribute a voltage potential associated with a respective phase across at least two adjacent thruster stages of the plurality of thruster stages such that a first voltage difference between the ion source and a first attractor-repeller nearest to and following the ion source is less than a second voltage difference between the ion source and a second attractor-repeller more distant from and following the ion source than the first attractorrepeller.

13. An electrostatic thruster comprising:a plurality of attractor-repellers arranged along a flow direction; and an emitter electrode, the attractor-repellers and the emitter electrode together configured to form an ion source in at least one phase of operation.

14. The electrostatic thruster of claim 13, further comprising:-43-4919-8285-9408Atty. Dkt. No.: 143360-0106a power output coupled to each attractor-repeller of the plurality of attractorrepellers; anda controller communicably coupled to the power output and configured to control the power output in phases to switch operation of respective ones of the attractorrepellers between an attractor and a repeller.

15. The electrostatic thruster of claim 14, further comprising:an alternating-current power supply coupled to the emitter electrode;a direct-current power supply coupled to an attractor-repeller of the plurality of attractor-repellers; anda capacitor electrically coupled between the alternating-current power supply and the emitter electrode such that a voltage of the emitter electrode floats with changes in voltage of the attractor-repeller.

16. The electrostatic thruster of claim 15, wherein the attractor-repeller is a first attractor-repeller, wherein the controller is configured to:in a first phase, operate the alternating-current power supply to apply alternating voltage to the emitter electrode such that the emitter electrode and the first attractor-repeller together generate a cloud of charged particles; andin a second phase, operate the direct-current power supply to supply direct-current voltage to (i) a second attractor-repeller of the plurality of attractor-repellers of a downstream stage to attract the cloud of charged particles and (ii) the first attractor-repeller of an upstream stage of substantially the same polarity as the cloud of charged particles such that the first attractor-repeller repels the cloud of charged particles toward the downstream stage.

17. The electrostatic thruster of claim 13, wherein an attractor-repeller of the plurality of attractor-repellers includes an insulator disposed across a portion of an outer surface thereof.-44-4919-8285-9408Atty. Dkt. No.: 143360-010618. The electrostatic thruster of claim 17, further comprising a plurality of emitter electrodes, including the emitter electrode, arranged along the insulator spaced from the attractor-repeller by a distance.

19. The electrostatic thruster of claim 18, wherein the distance is a first distance, and wherein the first distance is less than or equal to half of a second distance between an uninsulated portion of the attractor-repeller and a respective emitter electrode of the plurality of emitter electrodes nearest the uninsulated portion.

20. An electrostatic thruster comprising:a plurality of stages arranged along a flow direction, each stage including:an attractor-repeller having an insulated upstream portion and an uninsulated downstream portion; anda plurality of emitter electrodes disposed on opposing sides of the attractor-repeller along the insulated upstream portion and spaced from an outer surface of the attractor-repeller; anda controller configured to control voltages applied to the attractor-repeller and the plurality of emitter electrodes in phases such that, in a first phase, the plurality of emitter electrodes and the attractor-repeller of a respective stage of the plurality of stages together generate a cloud of charged particles, and, in a second phase, the attractor-repeller of an upstream stage of the plurality of stages repels the cloud of charged particles while the attractor-repeller of a downstream stage of the plurality of stages attracts the cloud of charged particles.-45-4919-8285-9408

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