System and method for increasing thrust and efficiency of electrostatic thrusters

Abstract

An electrostatic thruster including an emitter, a collector, a spacer, and a power source. The collector is coupled to the emitter and is spaced apart from the emitter along a streamwise direction. The collector includes a collector body and an insulator. The collector body extends away from the emitter along the streamwise direction from a leading edge of the collector body to a trailing edge of the collector body. The insulator covers the leading edge of the collector body and extends from the leading edge toward the trailing edge of the collector body. The spacer is coupled between the emitter and the collector and is configured to at least partially electrically isolate the emitter from the collector. The power source is electrically coupled to the emitter and the collector body. The power source is configured to generate a voltage potential between the emitter and the collector body.

Description

Atty. Dkt. No.: 143360-0102SYSTEM AND METHOD FOR INCREASING THRUST AND EFFICIENCY OF ELECTROSTATIC THRUSTERSBACKGROUND

[0001] The present disclosure relates to electrostatic thrusters and / or asymmetrical capacitors, which utilize a voltage potential for generating thrust.SUMMARY

[0002] One aspect of the present disclosure relates to an electrostatic thruster including an emitter, a collector, a spacer, and a power source. The collector is coupled to the emitter and is spaced apart from the emitter along a streamwise direction. The collector includes a collector body and an insulator. The collector body extends away from the emitter along the streamwise direction from a leading edge of the collector body to a trailing edge of the collector body. The insulator covers the leading edge of the collector body and extends from the leading edge toward the trailing edge of the collector body on both sides of the collector body. The spacer is coupled between the emitter and the collector and is configured to at least partially electrically isolate the emitter from the collector. The power source is electrically coupled to the emitter and the collector body. The power source is configured to generate a voltage potential between the emitter and the collector body.

[0003] In some embodiments, an insulated portion of the collector body that is covered by the insulator is larger than an uninsulated portion of the collector body.

[0004] In some embodiments, the insulator covers both an upper side and a lower side of the collector body so that only the trailing edge of the collector body is uncovered. In other embodiments, the insulator covers an entire upper side and an entire lower side of the collector body between the leading edge and the trailing edge.

[0005] In some embodiments, the leading edge of the collector body is spaced apart from the emitter along the streamwise direction by a first distance. The insulator extends a second distance along the streamwise direction from the leading edge toward the trailing edge. In some embodiments, the second distance may be greater than the first distance.-1- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0006] In some embodiments, a first dielectric strength of the insulator (e.g., a first thickness of the insulator) at the leading edge of the collector body is greater than a second dielectric strength of the insulator (e.g., a second thickness of the insulator) in at least one location between the leading edge and the trailing edge. In some embodiments, a thickness of the insulator decreases moving away from the leading edge of the collector body. In some embodiments, the thickness of the insulator may decrease continuously moving away from the leading edge of the collector body.

[0007] In some embodiments, the insulator includes an electret material that is configured to maintain a quasi-permanent electrical polarization under an applied electrical field.

[0008] In some embodiments, the insulator includes a plurality of insulating materials.

[0009] In some embodiments, the collector is formed in an airfoil shape that is configured to reduce drag across the collector.

[0010] In some embodiments, the emitter includes a dielectric barrier discharge emitter powered by an alternating current power source or a pulsed power source.

[0011] In some embodiments, the emitter includes a conductive wire that extends substantially parallel to the leading edge of the collector along a lateral direction that is substantially perpendicular to the streamwise direction.

[0012] Another aspect of the present disclosure relates to an electrostatic thruster assembly including an array of electrostatic thrusters and a support structure. At least one electrostatic thruster of the array of electrostatic thrusters includes an emitter and a collector. The collector is coupled to the emitter and is spaced apart from the emitter along a streamwise direction. The collector includes a collector body and an insulator. The collector body extends away from the emitter along the streamwise direction from a leading edge of the collector body to a trailing edge of the collector body. The insulator covers the leading edge of the collector body and extending from the leading edge toward the trailing edge of the collector body on both sides of the collector body. The support structure is coupled to the array of electrostatic thrusters and is configured to at least partially electrically isolate the emitter of the at least one electrostatic thruster from the collector of the at least one electrostatic thruster.-2- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0013] In some embodiments, electrostatic thruster assembly further includes at least one power source electrically coupled to at least a portion of the array of electrostatic thrusters. The at least one power source is configured to generate a voltage potential between (i) the emitter of the at least one electrostatic thruster and (ii) the collector body of the at least one electrostatic thruster.

[0014] In some embodiments, an insulated portion of the collector body of the at least one electrostatic thruster is larger than an uninsulated portion of the collector body.

[0015] In some embodiments, a thickness of the insulator of the at least one electrostatic thruster decreases moving away from the leading edge of the collector body of the at least one electrostatic thruster.

[0016] In some embodiments, the emitter of the at least one electrostatic thruster includes a dielectric barrier discharge power source including an intermediate electrode and an alternating current power source.

[0017] In some embodiments, the array of electrostatic thrusters is mounted onto the support structure in a substantially parallel arrangement so that the collectors of adjacent ones of the array of electrostatic thrusters extend substantially parallel to one another along a lateral direction that is substantially perpendicular to the streamwise direction.

[0018] Another aspect of the present disclosure relates to a method of making an electrostatic thruster. The method includes covering at least a portion of a collector body that extends along a streamwise direction from a leading edge of the collector body to a trailing edge of the collector body with an insulator to form a collector. The covering operation includes covering the leading edge of the collector body with the insulator so that the insulator extends from the leading edge toward the trailing edge on both sides of the collector body. The method further includes coupling the collector to an emitter that is spaced apart from the collector along the streamwise direction using a spacer that is configured to electrically isolate the emitter from the collector; and electrically coupling a power source to the emitter and the collector body so that activation of the power source generates a voltage potential between the emitter and the collector body.

[0019] 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 -3- 4930-5135-2865Atty. Dkt. No.: 143360-0102herein 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

[0020] FIG. l is a perspective view of an electrostatic thruster, according to an embodiment.

[0021] FIG. 2 is a side view of an electrostatic thruster, according to another embodiment.

[0022] FIG. 3 is a side view of an electrostatic thruster including a dielectric barrier discharge ion source, according to an embodiment.

[0023] FIG. 4 is an electric field diagram for an uninsulated electrostatic thruster, according to an embodiment.

[0024] FIG. 5 is an electric field diagram for an insulated electrostatic thruster, according to an embodiment.

[0025] FIG. 6 is a contour plot approximating the electric field for the uninsulated electrostatic thruster of FIG. 4, according to an embodiment.

[0026] FIG. 7 is a contour plot approximating the electric field for the insulated electrostatic thruster of FIG. 5, according to an embodiment.

[0027] FIG. 8A is a contour plot approximating a fluid velocity profile across the uninsulated electrostatic thruster of FIG. 4, according to an embodiment.

[0028] FIG. 8B is a contour plot approximating a fluid velocity profile across the insulated electrostatic thruster of FIG. 5, according to an embodiment.

[0029] FIG. 8C is a side cross-sectional view of an electrostatic thruster including an insulator having variable thickness, according to an embodiment.

[0030] FIG. 9 is a side cross-sectional view of an electrostatic thruster including multiple layers of insulating material, according to an embodiment.

[0031] FIG. 10 is a side cross-sectional view of an electrostatic thruster including multiple sections of insulating material along a streamwise direction, according to an embodiment.-4- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0032] FIG. 11 is a side cross-sectional view of an electrostatic thruster including a single layer of insulating material, according to an embodiment.

[0033] FIG. 12 is a side cross-sectional view of an electrostatic thruster including a layer of insulating material that extends to a trailing edge of the electrostatic thruster, according to an embodiment.

[0034] FIG. 13 is a side cross-sectional view of an electrostatic thruster assembly including an array of electrostatic thrusters, according to an embodiment.

[0035] FIG. 14 is a flow diagram of a method of manufacturing an electrostatic thruster, according to an embodiment.DETAILED DESCRIPTION

[0036] 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

[0037] 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.

[0038] 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 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, such as a dielectric material such as fiberglass, epoxy, or another electrical insulator, to -5- 4930-5135-2865Atty. Dkt. No.: 143360-0102provide 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.

[0039] 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.Electrostatic Thruster

[0040] Referring to the remaining figures generally, embodiments of the present disclosure relate to electrostatic thrusters that are configured to increase the thrust and efficiency relative to existing designs. The electrostatic thrusters of the present disclosure include a collector that is structured to increase utilization of a charged particle and / or ion cloud generated by the emitter to thereby generate static force in a single direction for a longer duration than can be achieved using existing designs. Stated differently, the electrostatic thrusters of the present disclosure can maintain electrostatic force for a longer period of time without necessarily increasing the amount of charged particles (e.g., a greater force for the same amount of charged particles as an uninsulated collector).

[0041] According to at least one embodiment, the electrostatic thruster includes a collector having an electrical insulator (e.g., an electrical insulation layer) applied along a portion of the collector that faces toward the emitter. In some embodiments, the insulator is applied across, and covers, a substantial portion of the collector body that extends away from the emitter. Such an arrangement can reduce discharge of charged particles along the forward and / or leading edge of the collector, and provide a larger area along the collector (in a streamwise direction, e.g., a flow direction of fluid flow across the collector when generating thrust, a direction extending from the emitter toward the collector, etc.) across which the charged particles are attracted.

[0042] The collectors of the present disclosure include an insulator that is arranged along the collector body so that the attractive force is maintained across a length of the collector moving away from the emitter in a stream wise direction, and without increasing the distance between the emitter and the collector. Such an arrangement can increase the period-6- 4930-5135-2865Atty. Dkt. No.: 143360-0102of time during which the charged particles remain in front of the non-insulated portion of the collector (remain in front of portions of the collector that are attracted to the charged particles), which can increase system efficiency. Application of the insulator across the collector body can also enable the use of a larger voltage potential between the emitter and the collector, or closer spacing between the emitter and the collector without causing dielectric breakdown. Such an arrangement can increase thrust generated by the electrostatic thruster as compared to a non-insulated collector design.

[0043] 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 enough voltage to cause an electrical shorting between the emitter and the collector (e.g., to cause arcing / sparks and an electrical short through the plasma in the gap between the emitter and the collector).

[0044] Referring to FIG. 2, an electrostatic thruster 100 is shown, according to an embodiment. The electrostatic thruster 100 (which may also be referred to as an electrostatic thrust device, an electrostatic thrust system, or an electrostatic thrust assembly) includes an emitter 102 (which may also be referred to as an exciter or an ion source), a collector 104 (which can also be referred to as an attractor, a collector device, or a collector assembly), a support structure 106, and a power source 108. In other embodiments, the electrostatic thruster 100 may include additional, fewer, and / or different components. For example, the electrostatic thruster 100 can include more than one support structure 106 and / or power source 108 in some embodiments.

[0045] The emitter 102 is configured to generate electrically charged particles (e.g. ions) responsive to a voltage potential applied between the emitter 102 and the collector 104. The voltage potential applied to the emitter 102 by the power source 108 produces corona discharge (an electrical discharge) caused by ionization of the fluid surrounding the emitter 102. In the embodiment of FIG. 2, the emitter 102 is a conductor, such as a metal wire extending along a lateral direction 110 (e.g., into and out of the page as shown in FIG. 2). In some embodiments, the emitter 102 (e.g., the overall structure of the emitter 102 between lateral ends of the emitter 102) extends substantially parallel to a leading edge 118 of the collector 104. In some embodiments, the emitter 102 is metal wire that follows a sawtooth path or another non-linear path such that a gap between the emitter 102 and the collector 104 varies across the lateral direction (into and out of the page as shown in FIG. 2), as -7- 4930-5135-2865Atty. Dkt. No.: 143360-0102described in Dutch Pat. Appl. No. 2036471, filed December 8, 2023, the entire contents of which are hereby incorporated by reference herein for any and all purposes.

[0046] The emitter 102 has a smaller surface area than the collector 104. For example, the emitter 102 may be an electrically conductive wire having a diameter of about 0.2 mm or less (e.g., 0.1 mm, 0.05 mm, or any value between and including any two of the foregoing values), which can reduce the voltage potential necessary for ionization and reduce the risk of arcing. In other embodiments, the diameter of the wire may be different. In other embodiments, the emitter 102 may be another type of ion source. For example, the emitter 102 may include a needle electrode that includes multiple conductive needle-like (acicular) extensions (e.g., wires, extenders, etc.) spaced apart from one another that are oriented towards the leading edge 118 of the collector. In other embodiments, the emitter 102 may be configured as a dielectric barrier discharge (DBD) ion source (e.g., a DBD emitter), as will be further described with reference to FIG. 3. In some embodiments, the emitter 102 includes multiple electrodes including an intermediate electrode as described in Dutch Pat. Appl. No. 2036471, filed December 8, 2023, the entire contents of which are hereby incorporated by reference herein for any and all purposes.

[0047] The power source 108 is electrically coupled to the emitter 102 and the collector 104 (e.g., a collector body 120 of the collector 104). The power source 108 is configured to generate a voltage potential between the emitter 102 and the collector 104 (e.g., the collector body 120).

[0048] In the embodiment of FIG. 2, the power source 108 is a direct current (DC) power supply having a first end that is electrically connected to the collector 104 and a second end that is electrically connected to the emitter 102. In some embodiments, the first end is a negative terminal, and the second end is a positive terminal. In other embodiments, the polarity at the first end and the second end may be reversed. In some embodiments, and as shown, the first end, and the collector 104, are electrically connected to ground, which in some embodiments may be a common electrical potential instead of an actual ground connection.

[0049] In some embodiments, the power source 108 includes a pulsed DC power supply, such as a nanosecond pulse power supply, that is configured to limit operation of the power source 108 at a rated voltage (e.g., about 20 kV to 60 kV, 5 kV to 150 kV, 20 kV to 150 kV,-8- 4930-5135-2865Atty. Dkt. No.: 143360-0102or 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). The power supply can limit the power source 108 to be within the rated voltage for time scales that are less than the time required for arcing between the emitter 102 and the collector 104 resulting from dielectric breakdown (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 electrical shorting between the emitter 102 and the collector 104. In other embodiments, the electrostatic thruster 100 includes a current limiter 114, such as a resistor rated to the voltages of above rated voltage for the electrostatic thruster 100.

[0050] Referring to FIG. 3, an electrostatic thruster 200 is shown in which the emitter 202 includes an active ion source, shown as a DBD source 203 (which also may be referred to as a DBD emitter). The DBD source 203 is configured to produce charged particles in a controlled area or region forward of the collector 204. The DBD source 203 includes a first electrode 205 (e.g., an insulated electrode) and a second electrode 207 (e.g., an emitter electrode) that are spaced apart from one another. In some embodiments, the first electrode 205 and the second electrode 207 are spaced apart from one another along a direction that is perpendicular to both the lateral direction and a streamwise direction (e.g., a flow direction of fluid flow across the collector when generating thrust, left to right as shown in FIG. 3). In other embodiments, the arrangement of the first electrode 205 and the second electrode 207 may be different.

[0051] The electrostatic thruster 200 also includes multiple power sources 208 including a DC power supply, as described with reference to FIG. 2, and an alternating current (AC) power supply 209. The AC power supply 209 is electrically coupled to the first electrode 205 and is configured to apply a time varying voltage between the first electrode 205 and the second electrode 207. In the embodiment of FIG. 3, a first terminal of the AC power supply 209 is connected to the first electrode 205 and a second terminal of the AC power supply 209 is coupled to ground, or a common voltage potential. In some embodiments, the ground or common voltage potential is shared with the DC power supply. In other embodiments, the AC power supply 209 and the DC power supply are electrically connected to different voltage potentials.-9- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0052] In the embodiment of FIG. 3, the emitter 202 also includes an optional capacitor 211 that is electrically connected in series between the AC power source 209 and the first electrode 205. The use of a DBD ion source can increase production of charged particles for the electrostatic thruster 200 without substantially increasing the risk of dielectric breakdown between the emitter 202 and the collector.

[0053] Referring again to FIG. 2, the electrostatic thruster 100 also includes a support structure 106 coupled between the emitter 102 and the collector 104 and configured to at least partially electrically isolate the emitter 102 from the collector 104 (e.g., to prevent an electrical connection between the emitter 102 and the collector 104 through the support structure 106). The support structure 106 is coupled to a lateral end of the emitter 102 and the collector 104 and supports the emitter 102 and the collector 104 a distance apart from one another. In some embodiments, the support structure 106 includes a panel and / or framework made at least partially from an electrical insulator, such as fiberglass. In other embodiments, the support structure 106 includes a different material having high electrical resistivity.

[0054] The collector 104 is configured to generate a force responsive to a voltage potential between the charged particles and the collector 104. The collector 104 is coupled to the emitter 102 and is spaced apart from the emitter 102 along a streamwise direction 116 (e.g., a flow direction of fluid flow across the collector 104 when generating thrust, left to right as shown in FIG. 2) that is substantially perpendicular to the lateral direction 110. In some embodiments, and as shown, the collector 104 extends substantially parallel to the emitter 102 such that a separation distance between the emitter 102 and the collector 104 is substantially uniform across the lateral direction 110. In the embodiment of FIG. 2, the emitter 102 includes an electrically conductive wire that extends substantially parallel to a leading edge 118 of the collector 104 along the lateral direction 110.

[0055] The collector 104 includes a collector body 120 and an insulator 122 that is coupled to the collector body 120. The collector body 120 extends away from the emitter 102 along the streamwise direction 116, from the leading edge 118 to a trailing edge 124 of the collector body 120. The leading edge 118 of the collector body 120 is spaced apart from the emitter 102 along the streamwise direction 116 by a first distance (e.g., a first distance 425 as shown in FIG. 7) that may vary depending on the voltage potential applied by the power-10- 4930-5135-2865Atty. Dkt. No.: 143360-0102source 108 to the emitter 102 and the collector 104, as well as the arrangement and size of the insulator 122.

[0056] In some embodiments, the collector body 120 includes an elongated element that includes an electrically conductive material. For example, the conductor body 120 may include a lightweight material supporting a conductive material layer or coating. In the embodiment of FIG. 2, the collector body 120 may have an airfoil shape that is configured to reduce drag and improve the overall efficiency of the electrostatic thruster 100. In embodiments in which the electrostatic thruster 100 is used in an aircraft application, the airfoil shape can also be configured to generate lift across the collector 104. The collector body 120 is streamlined and has a rounded leading edge and a sharp trailing edge forming a point directed along the streamwise direction 116. Such an arrangement can increase aerodynamic efficiency (e.g., reduces drag) during operation.

[0057] The collector body 120 is symmetric across a reference plane that extends parallel to the streamwise direction 116. In other embodiments, the airfoil shape may be asymmetric about the reference plane. Such arrangements can be particularly beneficial in the context of an aircraft or other vehicle application, such as for solid state (e.g., silent or low noise) aircraft and drones. In such an implementation, the support structure 106 may include at least part of a thruster housing (e.g., thruster body) of the aircraft and / or a wing of the aircraft.

[0058] In other embodiments, the collector body 120 may have another shape or profile, such as an elongated shape extending along the streamwise direction 116, a rounded or curved shape, or another shape.

[0059] Although parts of the description herein refer specifically to aircraft applications, it should be understood that the same or similar electrostatic thruster design may be used in other types of systems, such as: 1) solid state (e.g., silent) ventilation systems, 2) electrostatic air purification systems (e.g., to both purify and provide thrust to move air through the purification system), 3) ionizers, and others. The electrostatic thruster designs of the present application may also be used in other vehicle applications, such as cars, boats, and other vehicles.-11- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0060] The insulator 122 covers the leading edge 118 of the collector body 120 and extends from the leading edge 118 toward the trailing edge 124 of the collector body 120 on both sides of the collector body 120. In the embodiment of FIG. 2, the insulator 122 extends from the leading edge 118 and across both a first side 126 (e.g., an upper side as shown in FIG. 2) and a second side 128 (e.g., a lower side as shown in FIG. 2) of the collector body 120 that faces away from the first side 126.

[0061] In some embodiments, the insulator 122 includes an electrical insulation material, which may be in the form of at least one insulating material layer (e.g., film, sheet, etc.), that is applied to the collector body 120. The insulator 122 may be bonded (e.g., glued, adhered), or otherwise affixed directly to the collector body 120, to an exterior surface of the collector body 120. For example, the insulator 122 can include or be provided with an adherent. The adherent can be tape having an adhesive material or layer applied to one side of the tape to facilitate bonding of the tape to the collector body 120. In other embodiments, the insulator 122 may be overmolded onto the collector body 120. In other embodiments, the insulator 122 may be formed from one or more flexible printed circuit boards (PCBs) including layers of copper and gold combined with layers of polyimide or another core material. In some embodiments, the insulator 122 is formed from a single flexible PCB. In other embodiments, the insulator 122 may be formed from a folded sheet of flexible PCB, or a sheet of flexible PCB that is wrapped around a collector core material of the collector body. Such an arrangement enables controlled variation of different layer thicknesses and / or numbers of layers in different regions across the collector, and can be used to control the dielectric strength across the collector body without requiring multiple separate sheets or layers of insulator material.

[0062] In some embodiments, the insulator 122 has a low dielectric constant and is configured to store a minimal amount of charge. For example, the insulator 122 may include a dielectric film having a dielectric constant (in a range from about 3 to 6, 3 to 4, or any value between and including the foregoing ranges of values). The insulator 122 may have a high dielectric strength to withstand the large voltage potentials between the emitter and the collector. For example, the dielectric strength of the insulator 122 may be about 100 kV / mm or greater in various embodiments. A thickness of the insulator 122 may be adjusted to range in dielectric strength by a factor of about 3, 4, 5, 6, 7, 8, 9, 10, or more across the collector in various embodiments (e.g., so that the dielectric strength of the -12- 4930-5135-2865Atty. Dkt. No.: 143360-0102insulator 122 is about three times greater at the leading edge of the collector as compared to the dielectric strength of the insulator 122 proximate to a trailing edge of the collector, etc.).

[0063] The insulator 122 may also have an electrical resistance that is high enough to provide dielectric strength while low enough to discharge particles and / or to prevent an induced electrostatic charge within the insulator 122. For example, the insulator 122 may include cellulose electrostatic discharge (ESD) tape that is configured to resist electrostatic charge, such as Desco 81230, or a polyimide film with dissipative additives.

[0064] In at least one embodiment, the insulator 122 includes an electret material that is configured to maintain an at least quasi-permanent electrical polarization (e.g., to induce molecular dipoles in the insulating material) under an applied electrical field across the insulator 122. The voltage produced by the bound charges in the electret material can be deducted from the required voltage provided by the power source 108 to reduce the voltage required from the power source 108. In some embodiments, the electrostatic thruster may be configured to modulate the power source 108 based on an induced polarization of the insulator 122, which can reduce the required voltage from the power source 108 under certain conditions. The electret material can include but is not limited to quartz, silicon dioxide, and / or one or more synthetic polymers, alone or in any combination.

[0065] The insulator 122 is wrapped around (e.g., folded over, etc.) the exterior surface of the collector body 120 at the leading edge 118 of the collector body 120. The insulator 122 covers a substantial portion of the collector body 120 extending from the leading edge 118. The collector body 120 includes an insulated portion 130 (e.g., a covered surface portion) that is covered by the insulator 122, and an uncovered (exposed) portion 132 (e.g., an exposed portion, a non-insulated portion) that is exposed to an environment surrounding the collector 104. In the embodiment of FIG. 2, the insulated portion 130 that is covered by the insulator 122 is larger than the uninsulated portion 132 of the collector body 120.

[0066] The application of the insulator 122 to the collector body 120 provides various improvements over existing electrostatic thruster designs. For example, the insulator 122 enables controlling the strength of the electric field lines between the emitter 102 and the collector 104 and across different portions of the collector 104.-13- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0067] Referring to FIGS. 4 and 5, an electric field diagram for two different electrostatic thrusters is shown for an uninsulated thruster 300 (FIG. 4), and an insulated thruster 400 (FIG. 5). The insulated thruster 400 includes an insulator 422 covering a leading edge of the collector 404. The insulator 422 reduces the strength of the electric field between the emitter 402 and the leading edge of the collector 404 as compared to the strength of the electric field between the emitter 402 and the upper and lower surfaces (e.g., the first and second sides) of the collector 404. The insulator 122 also enables the emitter 402 to be positioned much closer to the collector 404 as compared to the uninsulated thruster 300 for a same or approximately equivalent voltage potential between the emitter 402 and the collector 404. Alternatively, or in combination, the insulated thruster 400 can also enable the use of larger voltage potentials between the emitter 402 and the collector 404 as compared to the uninsulated thruster 300.

[0068] FIGS. 6 and 7 show contour plots approximating electric field lines for the uninsulated thruster 300 (FIG. 6) and the insulated thruster 400 (FIG. 7). The distribution of electric force across the surface of the collector 404 can increase the time duration of thrust, and reduce the effects of negative forces acting on charged particles that have moved past the leading edge of the collector 404. Referring to FIG. 6, and due to the concentration of electric field strength at the leading edge of the collector, charged particles 338 leaving the emitter are directed primarily and disproportionately toward the leading edge relative to other regions of the collector. As the charged particles 338 move toward and past the leading edge, a force vector 340 between the charged particles 338 and the leading edge reverses.

[0069] In contrast, the insulator 422 in FIG. 7 distributes the electric force more uniformly across the collector 404 (e.g., across a second distance corresponding to a insulated portion of the collector, and a third distance between the trailing edge of the insulator 422 and the trailing edge of the collector 404), reducing the negative force component of the force vector 440 between the charged particles 438 and the collector 404 as the charged particles 438 move past and across the collector 404. In such an arrangement, the force vector 440 can be maintained in the intended direction (e.g., the streamwise direction, left to right as shown in FIG. 7) for a longer time period relative to the uninsulated collector 300 (FIG. 6).

[0070] In some embodiments, and depending on the size of the insulated portion of the collector, the efficiency (e.g., the thrust to power ratio) of the insulated electrostatic thruster -14- 4930-5135-2865Atty. Dkt. No.: 143360-0102400 can be increased by about 8 times, or more, relative to the uninsulated thruster 300. Additionally, and depending on the size and arrangement of the collector, the emitter, and the insulator (e.g., the first distance between the emitter and the collector, the size of the insulated portion or the second distance, the dielectric strength of the insulator, and / or the voltage potential applied between the emitter and the collector), different ranges of performance can be obtained from relatively low thrust with high efficiency (e.g., about 8 times increase in efficiency with a reduction in approximately 60% in thrust as compared to the uninsulated thruster 300) to more than double the thrust while still having twice the efficiency of the uninsulated thruster 300 (e.g., about 3.5 times increase in thrust at double the thrust to power ratio as compared to the uninsulated thruster 300).

[0071] Referring to FIG. 7, the insulator 422 extends a second distance 434 (e.g., a covered chord distance) across the collector body 420 along the streamwise direction 416, from the leading edge 418 toward the trailing edge 424 on both sides of the collector body 420. In some embodiments, and as shown, the second distance 434 is greater than the first distance 425 between the collector 404 and the emitter 402. In the embodiment of FIG. 7, the second distance 434 is greater than about 50% of the first distance 425. Such an arrangement can be particularly beneficial in designs in which an insulator 422 having uniform dielectric strength is used across the collector body 420 (e.g., so that the dielectric strength of the insulator 422 is approximately the same at different points along the collector body 420 in the streamwise direction 416). In such arrangements, the size of the covered area can provide a significant increase in the overall efficiency of the electrostatic thruster 400. In other embodiments, a smaller insulated portion may be used while still providing a net increase in the overall efficiency of the system.

[0072] In some embodiments, the uninsulated portion 432 extends over a relatively small proportion of the overall surface of the collector body 420 across the trailing edge 424 of the collector body 420. For example, and as shown in FIG. 7, a third distance 436 (e.g., an uncovered chord distance) between the trailing edge of the insulator 422 and the trailing edge 424 of the collector body 420 may be less than the first distance 425 and the second distance 434. Positioning the uninsulated portion 432 at the trailing edge 424 can enable discharge of at least some of the charged particles passing across the collector 404, which can reduce forces opposing movement of the collector 404 toward the emitter 402 (e.g., reverse thrust).-15- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0073] In some embodiments, the application of the insulator to the collector body can provide an aerodynamic benefit as compared to an uninsulated thruster. For example, referring to FIGS. 8 A and 8B, contour plots of fluid velocity are shown that illustrate enhanced flow due to an insulated thruster 400 (FIG. 8B) as compared to an uninsulated thruster 300 (FIG. 8 A). As shown in FIG. 8 A, the angle of attack of the collector 304 can cause flow separation and turbulence across the upper surface of the collector 304, due to the pressure difference between the upper and lower sides of the collector 304, which can increase drag. The shape of the collector 304 (e.g., forming the collector in a shape such as a cylinder, etc.) can also cause flow separation and turbulence by creating large changes in pressure between the leading edge and trailing edge, or across other areas of the collector 304.

[0074] FIG. 8B shows an insulated thruster 400 arranged at a similar angle of attack as the uninsulated thruster 300 of FIG. 8 A. As shown in FIG. 8B, the insulated collector 404 spreads out the high voltage potential across the upper surface of the collector 404. The increase in the electric field across the surfaces of the collector can pull in air particles around the collector on both sides of the collector. In some embodiments, the insulator is configured to provide a difference in voltage potential between a leading edge and a trailing edge of the collector on the order of about 5 to 10 kV, 5 to 15 kV, 10 to 20 kV, or greater across the collector. As shown in FIG. 8B, pulling in air particles around the collector 404 can reduce turbulence and / or delay flow separation to a point along the upper surface that is farther away from the leading edge, reducing drag.

[0075] The arrangement of the insulator along the collector body can differ in various embodiments. In some embodiments, the insulator has a dielectric strength that varies along the streamwise direction. For example, referring to FIG. 8C, a portion of a collector 504 is shown that includes an insulator 522 having variable thickness along the length of the collector body 520 in a streamwise direction. A thickness 542 of the insulator 522 decreases moving away from the leading edge 518 of the collector body 520 such that a first thickness 542a of the insulator 522 at the leading edge 518 is greater than a second thickness 542b of the insulator 522 in at least one location moving away from the leading edge 518. In some embodiments, and as shown, the thickness 542 of the insulator 522 decreases continuously moving away from the leading edge 518 of the collector body 520-16- 4930-5135-2865Atty. Dkt. No.: 143360-0102(e.g., the insulator 522 has a continuously variable thickness moving away from the leading edge 518).

[0076] Such an arrangement, as shown in FIG. 8C, can spread the strength of the electric field lines more uniformly between the leading edge and the trailing edge of the collector body 520. Stated differently, the reduction in dielectric strength across the collector in a streamwise direction can de-focus the electric field strength on the edge of the insulator 522, which can enable a more controlled flow of the charged particles across the collector 504. The reduction in the thickness 542 of the insulator 522 can also reduce the amount of insulating material required for the electrostatic thruster, which can reduce the overall weight of the electrostatic thruster. In other embodiments, the thickness 542 of the insulator 522 may vary in a semi-continuous manner between adjacent sections of the insulator 522 across the streamwise direction, which can elicit a similar performance effect but without requiring a continuous reduction in material thickness across the insulator 522.

[0077] In the embodiment of FIG. 8C, the insulator 522 extends across a second distance 534 of the collector body 520 that is approximately equal to a first distance 525 between the emitter 502 and the collector 504. Such an arrangement, which includes a reduction in dielectric strength across the collector 504 in the streamwise direction, can result in an increase in both thrust and efficiency as compared to uninsulated collector designs, due at least in part to the gradual increase in strength of the attractive force moving toward the uninsulated portion (e.g., the uninsulated portion) of the collector 504. For example, in certain arrangement with fixed input power (e.g., in which the first distance 525 is approximately 7 cm, the second distance 534 is approximately 7.5 cm, and the dielectric strength varied by a factor of 3 across the collector), the thrust can increase by a factor of approximately 3.5 times as compared to an uninsulated collector design, while increasing the overall efficiency by a factor of about 2 times or greater.

[0078] Referring to FIG. 9, an embodiment of a collector 604 is shown that includes an insulator 622 having multiple insulating material layers applied across the leading edge of the collector body. The insulator 622 includes a first insulating material layer 622a, and a second insulating material layer 622b applied over the first insulating material layer 622a. In some embodiments, and as shown, the first insulating material layer 622a extends a greater distance across the collector body than the second insulating material layer 622b, from the leading edge toward the trailing edge of the collector body. In some embodiments,-17- 4930-5135-2865Atty. Dkt. No.: 143360-0102the first insulating material layer 622a and the second insulating material layer 622b are made from the same type of insulating material. In other embodiments, the first insulating material layer 622a and the second insulating material layer 622b are made from different materials. In other embodiments, the insulator 622 may include more insulating material layers stacked on top of one another at the leading edge.

[0079] Referring to FIG. 10, another embodiment of a collector 704 is shown that includes multiple different insulating layers arranged in discrete sections across the surface of the collector body. The insulator 722 includes a first insulating material layer 722a engaged with the leading edge of the collector body, a second insulating material layer 722b extending from the first insulating material layer 722a and across an intermediate portion of the collector body, and a third insulating material layer 722c extending from the second insulating material layer 722b toward the trailing edge of the collector body. In the embodiment of FIG. 10, a dielectric strength of the first insulating material layer 722a is greater than a dielectric strength of both the second insulating material layer 722b and the third insulating material layer 722c. In some embodiments, the dielectric strength of the insulating material layers decreases across the collector body along the streamwise direction, which can improve uniformity of the electric field strength across the collector 704. In other embodiments, the insulator 722 may include additional or fewer insulating material layers. The relative lengths of adjacent sections of the insulating material layers may also differ in various embodiments.

[0080] In some embodiments, the insulator 722 includes a material with a gradual (e.g., continuous) change in dielectric strength in the streamwise direction across the collector, along the chord of the collector, for example, without a substantial change in thickness of the insulator 722.

[0081] Referring to FIG. 11, in some embodiments, the insulator 822 may include only a single insulating material layer 822a. In other embodiments, and as shown in FIG. 12, the insulator 922 may substantially cover the entire outer surface of the collector body, including an entire first side 926 (e.g., an upper side as shown in FIG. 12) of the collector body and an entire second side 928 (e.g., a lower side as shown in FIG. 12) of the collector body, from the leading edge to the trailing edge of the collector body.-18- 4930-5135-2865Atty. Dkt. No.: 143360-0102

[0082] In some embodiments, and as shown in FIG. 12, the trailing edge 924 is at least partially uninsulated, such as at a slit and / or narrow opening defined between opposing ends of the insulator 922 on the first side 926 and the second side 928. Such an arrangement can enable discharge of at least some charged particles across the trailing edge 924. The sized of the uninsulated portion across the trailing edge 924 may be different in various embodiments. For example, the uninsulated portion may extend adjacent to the trailing edge 924 and / or slightly forward of the trailing edge 924 on one or both sides. In other embodiments, the insulator 922 may include perforations (e.g., small holes, openings, etc.) and / or an elongated opening at the trailing edge 924 on one or both sides of the collector body. In some embodiments, the number and / or size of the perforations and / or opening(s) at or proximate to the trailing edge 924 may be insufficient to discharge all of the particles moving past the trailing edge, allowing at least some of the charged particles to propel past the collector, which may be beneficial in some (e.g., staged) electrostatic thruster assembly designs.

[0083] In some embodiments, the collector may be fully covered by the insulator on all sides of the collector body. Such an arrangement can enable greater voltage potentials between the emitter and the collector, in a more compact electrostatic thruster. In such embodiments, the power source may be configured to apply a larger voltage potential between the emitter and the collector, and / or may include a DBD ion source or an intermediate electrode between the emitter and the collector to improve the pull of charged particles away from the emitter during operation.

[0084] The electrostatic thruster may be arranged in various different configurations to increase the overall thrust produced by the system. Referring to FIG. 13, an electrostatic thruster assembly 1000 is shown that includes an array of electrostatic thrusters 1001 arranged in series with one another along the streamwise direction. At least one of the electrostatic thrusters 1001 (e.g., each of the electrostatic thrusters 1001) may be arranged in a similar manner as any one of the individual electrostatic thrusters described herein.

[0085] In the embodiment of FIG. 13, the electrostatic thruster assembly 1000 also includes a support structure 1006 and at least one power source 1008 coupled to the array of electrostatic thrusters 1001. The support structure 1006 may be configured to at least partially electrically isolate the emitter of at least one of the array of electrostatic thrusters from the collector of the at least one electrostatic thruster. In other embodiments, the -19- 4930-5135-2865Atty. Dkt. No.: 143360-0102support structure 1006 is configured to support multiple electrostatic thrusters so that the collectors of adjacent ones of the array of electrostatic thrusters extend substantially parallel to one another along a lateral direction (e.g., into and out of the page in FIG. 13) that is substantially perpendicular to the streamwise direction.

[0086] The power source 1008 may be electrically coupled to at least a portion of the array of electrostatic thrusters and may be configured to generate a voltage potential between (i) the emitter of the at least one electrostatic thruster, and (ii) the collector body of the at least one electrostatic thruster. In other embodiments, and as shown, the at least one power source includes multiple power supplies (e.g., one individual power supply for each electrostatic thruster, etc.) that may be configured to operate adjacent stages of the electrostatic thruster array using alternating polarities. The position and alignment between adjacent ones of the electrostatic thrusters may be different in various embodiments. The staged arrangement of electrostatic thrusters can increase the overall thrust generated by the electrostatic thruster assembly.

[0087] Referring to FIG. 14, a method 1100 of making an electrostatic thruster is shown, according to an embodiment. The method 1100 may be used to manufacture any of the electrostatic thrusters described herein, and will be described using the same terminology. In other embodiments, the method 1100 may include additional, fewer, and / or different operations.

[0088] At operation 1102, at least a portion of a collector body is covered with an insulator to form a collector. In some embodiments, operation 1102 includes providing the collector body, which may be formed in an airfoil shape or another shape depending on application requirements. Operation 1102 may also include providing an insulator, which may include a dielectric material such as dissipative polyimide film, or any of the other types of insulator materials described herein. In some embodiments, operation 1102 includes providing an insulating material layer having variable thickness across the insulating layer.

[0089] In some embodiments, operation 1102 includes covering a leading edge of the electrostatic collector (e.g., a forward edge of the electrostatic collector that is configured to face toward an emitter) with the insulator so that the insulator extends from the leading edge toward the trailing edge on both sides of the collector body. Operation 1102 may include aligning a central region of the insulator with the leading edge of the collector body.-20- 4930-5135-2865Atty. Dkt. No.: 143360-0102Operation 1102 may also include wrapping the insulator over the leading edge so that opposing sides of the insulator extend across opposing sides of the collector body.

[0090] In some embodiments, operation 1102 may include applying multiple layers of insulating material onto the collector body. In such embodiments, at least one of the insulating material layers may have a different dielectric constant and / or other material properties as compared to the other insulating materials layers.

[0091] In some embodiments, operation 1102 includes arranging the one or more insulating material layers so that a dielectric constant of the insulator decreases across the collector in the streamwise direction (e.g., so that the thickest portion of the insulator is disposed at the leading edge of the collector).

[0092] In some embodiments, operation 1102 include bonding the one or more insulating material layers to the external surface of the collector body using glue or another adhesive material (e.g., by an adhesive material applied to one side of the insulating material layer(s)). In some embodiments, operation 1102 includes applying multiple sections of insulating material to the collector body across a streamwise direction and without any gaps between adjacent sections.

[0093] The method 1100 may also include coupling the collector to an emitter, at operation 1104. In some embodiments, operation 1104 includes coupling the collector to an emitter that is spaced apart from the collector along the streamwise direction using a support structure (e.g., a spacer, a plurality of spacers, a framework, etc.). The support structure may be configured to electrically isolate the emitter from the collector. In some embodiments, operation 1104 includes mounting the emitter and the collector to the support structure at opposing lateral ends of the emitter and the collector, and so that the emitter extends substantially parallel to the collector. In some embodiments, operation 1104 includes mounting multiple electrostatic thrusters including a collector (e.g., a collector and an emitter, multiple collectors and one or more emitters, etc.), to the support structure and so that each of the electrostatic thrusters are spaced apart from one another (e.g., along the streamwise direction).

[0094] The method 1100 may also include electrically connecting the collector body to the emitter, at operation 1106. In some embodiments, operation 1106 includes electrically-21- 4930-5135-2865Atty. Dkt. No.: 143360-0102connecting a power source (e.g., a DC power supply) to the emitter and the collector body so that activation of the power source generates a voltage potential between the emitter and the collector body. In some embodiments, operation 1106 includes electrically coupling the collector body and / or a negative terminal of the power source to ground or another common voltage potential.

[0095] In some embodiments, the method 1100 also includes activating the electrostatic thruster. For example, the method 1100 may include activating the power source (e.g., switching the power source from an OFF state to an ON state) to apply the voltage potential between the emitter and the collector body. In some embodiments, method 1100 includes pulsing, by the power source, the voltage potential provided between the emitter and the collector body so that a time period of operation of the power source in an ON state is less than a time period required for dielectric breakdown between the emitter and the collector body. In some embodiments, and in scenarios in which the emitter includes a DBD ion source, the method 1100 may include activating an AC power supply to apply a second voltage potential between a first electrode of the emitter and a second electrode of the emitter.

[0096] 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.

[0097] 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 -22- 4930-5135-2865Atty. Dkt. No.: 143360-0102“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%.

[0098] 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 upper 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.

[0099] 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.

[0100] 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,-23- 4930-5135-2865Atty. Dkt. No.: 143360-0102and 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.

[0101] 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 according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0102] 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.

[0103] It is important to note that the construction and arrangement of the electrostatic thruster systems as shown in the various exemplary embodiments is 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.-24- 4930-5135-2865

Claims

Atty. Dkt. No.: 143360-0102WHAT IS CLAIMED IS:

1. An electrostatic thruster comprising:an emitter;a collector coupled to the emitter and spaced apart from the emitter along a streamwise direction, the collector comprising:a collector body extending away from the emitter along the streamwise direction from a leading edge of the collector body to a trailing edge of the collector body; andan insulator covering the leading edge of the collector body and extending from the leading edge toward the trailing edge of the collector body on both sides of the collector body;a spacer coupled between the emitter and the collector and configured to at least partially electrically isolate the emitter from the collector; anda power source electrically coupled to the emitter and the collector body, the power source configured to generate a voltage potential between the emitter and the collector body.

2. The electrostatic thruster of claim 1, wherein an insulated portion of the collector body that is covered by the insulator is larger than an uninsulated portion of the collector body.

3. The electrostatic thruster of claim 1, wherein the insulator covers both an upper side and a lower side of the collector body so that only the trailing edge of the collector body is uncovered.

4. The electrostatic thruster of claim 1, wherein the insulator covers an entire upper side and an entire lower side of the collector body between the leading edge and the trailing edge.

5. The electrostatic thruster of claim 1, wherein the leading edge of the collector body is spaced apart from the emitter along the streamwise direction by a first distance, wherein the insulator extends a second distance along the streamwise direction from the leading edge toward the trailing edge, and wherein the second distance is greater than the first distance.-25- 4930-5135-2865Atty. Dkt. No.: 143360-01026. The electrostatic thruster of claim 1, wherein a first thickness of the insulator at the leading edge of the collector body is greater than a second thickness of the insulator in at least one location between the leading edge and the trailing edge.

7. The electrostatic thruster of claim 1, wherein a dielectric strength of the insulator decreases moving away from the leading edge of the collector body.

8. The electrostatic thruster of claim 1, wherein the thickness of the insulator decreases continuously moving away from the leading edge of the collector body.

9. The electrostatic thruster of claim 1, wherein the insulator comprises an electret material that is configured to maintain a quasi-permanent electrical polarization under an applied electrical field.

10. The electrostatic thruster of claim 1, wherein the insulator comprises a plurality of insulating materials.

11. The electrostatic thruster of claim 1, wherein the collector has an airfoil shape that is configured to reduce drag across the collector.

12. The electrostatic thruster of claim 1, wherein the emitter includes a dielectric barrier discharge emitter powered by one of an alternating current power source and a pulsed power source.

13. The electrostatic thruster of claim 1, wherein the emitter comprises a conductive wire that extends substantially parallel to the leading edge of the collector along a lateral direction that is substantially perpendicular to the streamwise direction.-26- 4930-5135-2865Atty. Dkt. No.: 143360-010214. An electrostatic thruster assembly comprising:an array of electrostatic thrusters, at least one electrostatic thruster of the array of electrostatic thrusters comprising:an emitter;a collector coupled to the emitter and spaced apart from the emitter along a streamwise direction, the collector comprising:a collector body extending away from the emitter along the streamwise direction from a leading edge of the collector body to a trailing edge of the collector body;an insulator covering the leading edge of the collector body and extending from the leading edge toward the trailing edge of the collector body on both sides of the collector body; anda support structure coupled to the array of electrostatic thrusters, the support structure configured to at least partially electrically isolate the emitter of the at least one electrostatic thruster from the collector of the at least one electrostatic thruster.

15. The electrostatic thruster assembly of claim 14, further comprising at least one power source electrically coupled to at least a portion of the array of electrostatic thrusters, the at least one power source configured to generate a voltage potential between (i) the emitter of the at least one electrostatic thruster and (ii) the collector body of the at least one electrostatic thruster.

16. The electrostatic thruster assembly of claim 14, wherein an insulated portion of the collector body of the at least one electrostatic thruster is larger than an uninsulated portion of the collector body.

17. The electrostatic thruster assembly of claim 14, wherein a thickness of the insulator of the at least one electrostatic thruster decreases moving away from the leading edge of the collector body of the at least one electrostatic thruster.

18. The electrostatic thruster assembly of claim 14, wherein the emitter of the at least one electrostatic thruster comprises a dielectric barrier discharge power source comprising an insulated electrode, an emitter electrode, and an alternating current power source.-27- 4930-5135-2865Atty. Dkt. No.: 143360-010219. The electrostatic thruster assembly of claim 14, wherein the array of electrostatic thrusters is mounted onto the support structure so that the collectors of adjacent ones of the array of electrostatic thrusters extend substantially parallel to one another along a lateral direction that is substantially perpendicular to the streamwise direction.

20. A method compri sing :covering at least a portion of a collector body with an insulator to form a collector, the collector body extending along a streamwise direction from a leading edge of the collector body to a trailing edge of the collector body, wherein covering the portion of the collector body comprises covering the leading edge of the collector body with the insulator so that the insulator extends from the leading edge toward the trailing edge on both sides of the collector body;coupling the collector to an emitter that is spaced apart from the collector along the streamwise direction using a spacer that is configured to electrically isolate the emitter from the collector; andelectrically coupling a power source to the emitter and the collector body so that activation of the power source generates a voltage potential between the emitter and the collector body.

21. The method of claim 20, wherein covering the portion of the collector body with an insulator comprises arranging the insulator across the collector so that the dielectric strength of the insulator decreases moving away from the leading edge of the collector body.

22. The method of claim 20, further comprising generating charged particles in a fluid surrounding the emitter by activating the power source to apply the voltage potential between the emitter and the collector body.

22. A method of using the electrostatic thruster of any of the preceding claims.-28- 4930-5135-2865

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