A micro cathode arc thruster

Abstract

The present invention discloses a micro-cathode arc thruster, which relates to the technical field of micro-cathode arc thrusters and includes an anode structure, an insulating structure, a cathode emission structure, and a cathode metal tube structure. The cathode emission structure is located inside the anode structure, and the insulating structure is provided between the cathode emission structure and the anode structure. The front end of the cathode emission structure is provided with a plurality of cathode channels, and the cathode emission structure is provided with channels for filling liquid metal. The cathode channels are connected to the channels, and the rear end of the cathode emission structure is used to connect to the cathode metal tube structure. The micro-cathode arc thruster of the present invention improves the total impulse of the micro-cathode arc thruster by changing the physical form of the propulsion medium of the micro-cathode arc thruster and adjusting the supply form of the propulsion medium.

Description

Technical Field

[0001] The present invention relates to the technical field of micro cathode arc thrusters, in particular to a micro cathode arc thruster. Background Art

[0002] Microcathode arc thrusters, with their high specific impulse, low power, compact size, and low mass, are suitable for CubeSat propulsion and hold great promise. Extensive research has been conducted on optimizing the performance of conventional μ-CAT configurations. Key optimization areas include promoting propellant ablation, increasing propellant velocity, and enhancing thruster pulse discharge stability. To improve propellant ablation, some researchers have employed the addition of ablative anodes. Their goal is to increase the amount of propellant ablated per unit time without changing the existing structure, thereby enhancing thrust and total impulse. Improving the accelerating structure is a currently popular approach to μ-CAT. By combining an external structure with the conventional μ-CAT, the velocity of the emitted ions can be increased, boosting thrust and specific impulse, for example, in a two-stage (μ-CAT-MPD) thruster. The cathode is the most important part of the microcathode arc thruster as the conductive structure and working fluid. At present, as the discharge time of the microcathode arc thruster continues to increase, the traditional solid propulsion working fluid has a complex working fluid supply system and a very limited working fluid supply, which makes it difficult for the microcathode arc thruster to achieve a high total impulse. Summary of the Invention

[0003] The purpose of the present invention is to provide a micro cathode arc thruster, which improves the total impulse of the micro cathode arc thruster by changing the physical form of the propulsion medium of the micro cathode arc thruster and adjusting the supply form of the propulsion medium.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a micro cathode arc thruster, comprising an anode structure, an insulating structure, a cathode emission structure and a cathode metal tube structure, wherein the cathode emission structure is located on the inner side of the anode structure, the insulating structure is arranged between the cathode emission structure and the anode structure, a plurality of cathode channels are arranged at the front end of the cathode emission structure, a channel for filling liquid metal is provided in the cathode emission structure, the cathode channels are connected to the channels, and the rear end of the cathode emission structure is used to be connected to the cathode metal tube structure.

[0006] Preferably, it also includes a supporting structure and a connecting structure, both of which are located outside the cathode emission structure, the supporting structure is located between the anode structure and the connecting structure, and the connecting structure is used to connect the cathode emission structure and the cathode metal tube structure.

[0007] Preferably, the insulating structure includes a first insulating structure and a second insulating structure, the interior of the first insulating structure is a hollow structure, the first insulating structure is provided with a first insulating step, the first cathode step of the cathode emission structure is offset against the first insulating step, the interior of the second insulating structure is a hollow structure, the front end of the second insulating structure is offset against the second cathode step of the cathode emission structure and the rear end of the first insulating structure, and the second insulating step of the second insulating structure is offset against the first anode step of the inner wall of the anode structure.

[0008] Preferably, the anode structure includes an anode body and a lead wire, the anode body is made of brass, the interior of the anode body is a hollow structure, the inner wall of the anode body is provided with the first anode step, the front end of the lead wire is connected to the rear end of the anode body, and the lead wire passes through the supporting structure and the connecting structure in sequence.

[0009] Preferably, the cathode emission structure is made of brass, and a protrusion is provided at the front end of the cathode emission structure. The protrusion is provided with a plurality of coaxial annular grooves and a plurality of cathode channels. Two adjacent annular grooves are connected by a plurality of channels, and the bottom surface of the channel is flush with the bottom surface of the annular groove.

[0010] Preferably, the interior of the support structure is a hollow structure, the front end of the support structure abuts against the rear end of the anode structure, the rear end of the support structure abuts against the front end of the connecting structure, and the support structure is provided with a first through hole for the lead wire to pass through.

[0011] Preferably, the interior of the connecting structure is a hollow structure, the connecting structure is provided with a second through hole for the lead-out wire to pass through, the inner wall of the connecting structure is provided with a connecting step, the front end of the cathode metal tube structure is abutted against the connecting step, the inner wall between the connecting step and the front end of the connecting structure is provided with a first threaded segment, the inner wall between the connecting step and the rear end of the connecting structure is provided with a second threaded segment, the first threaded segment is threadedly connected to the first cathode threaded segment of the outer wall of the cathode emission structure, and the second threaded segment is threadedly connected to the second cathode threaded segment of the outer wall of the cathode metal tube structure.

[0012] Preferably, the cathode metal tube structure includes a first metal tube assembly and a second metal tube assembly, the interior of the first metal tube assembly and the interior of the second metal tube assembly are both hollow structures, the first metal tube assembly and the second metal tube assembly are vertically connected, the inner wall of the first metal tube assembly is provided with a cathode metal tube step, and the rear end of the cathode emission structure is against the cathode metal tube step.

[0013] Preferably, the liquid metal is a gallium-indium alloy.

[0014] Preferably, the diameter of the cathode channel is 0.05 mm, and the length of the cathode channel is 6 mm.

[0015] Compared with the prior art, the present invention has achieved the following technical effects:

[0016] The present invention utilizes liquid metal as the propulsion fluid of the micro-cathode arc thruster. The cathode emission structure acts as an electrode and also as a storage device for the liquid metal, thereby greatly simplifying the propulsion fluid supply system and effectively reducing the structure of the micro-cathode arc thruster, solving the propulsion fluid supply problem of the micro-cathode arc thruster. A plurality of cathode channels are used at the front end of the cathode emission structure to ensure that the thruster inter-electrode pulse arc can reach the liquid metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the micro cathode arc thruster of the present invention Figure 1 ;

[0019] Figure 2 Schematic diagram of the micro cathode arc thruster of the present invention Figure 2 ;

[0020] Figure 3 An exploded view of the micro cathode arc thruster of the present invention;

[0021] Figure 4 is a cross-sectional view of a micro cathode arc thruster according to the present invention;

[0022] Figure 5 Schematic diagram of the anode structure of the present invention;

[0023] Figure 6 A side view of the anode structure of the present invention;

[0024] Figure 7 is a cross-sectional view of the anode structure of the present invention;

[0025] Figure 8 This is a schematic diagram of a first insulating structure of the present invention;

[0026] Figure 9 is a side view of a first insulating structure of the present invention;

[0027] Figure 10 is a cross-sectional view of a first insulating structure of the present invention;

[0028] Figure 11 Schematic diagram of the second insulation structure of the present invention;

[0029] Figure 12 is a side view of a second insulating structure of the present invention;

[0030] Figure 13 is a cross-sectional view of a second insulating structure of the present invention;

[0031] Figure 14 Schematic diagram of the cathode emission structure of the present invention;

[0032] Figure 15 A side view of the cathode emission structure of the present invention;

[0033] Figure 16 is a cross-sectional view of the cathode emission structure of the present invention;

[0034] Figure 17 Schematic diagram of the support structure of the present invention;

[0035] Figure 18 A side view of the support structure of the present invention;

[0036] Figure 19 is a cross-sectional view of the support structure of the present invention;

[0037] Figure 20 Schematic diagram of the connection structure of the present invention Figure 1 ;

[0038] Figure 21 Schematic diagram of the connection structure of the present invention Figure 2 ;

[0039] Figure 22 A side view of the connection structure of the present invention Figure 1 ;

[0040] Figure 23 A side view of the connection structure of the present invention Figure 2 ;

[0041] Figure 24 is a cross-sectional view of the connection structure of the present invention;

[0042] Figure 25 This is a schematic diagram of the cathode metal tube structure of the present invention;

[0043] Figure 26 A side view of the cathode metal tube structure of the present invention;

[0044] Figure 27 This is a cross-sectional view of the cathode metal tube structure of the present invention;

[0045] Figure 28 Schematic diagram of the cathode structure size of the present invention;

[0046] Wherein: 100-micro cathode arc thruster, 1-anode structure, 2-first insulating structure, 3-second insulating structure, 4-cathode emission structure, 5-cathode metal tube structure, 6-support structure, 7-connecting structure, 8-first insulating step, 9-first cathode step, 10-second cathode step, 11-second insulating step, 12-first anode step, 13-anode body, 14-lead-out wire, 15-cathode metal tube step, 16-protrusion, 17-annular groove, 18-cathode channel, 19-channel, 20-first through hole, 21-second through hole, 22-connecting step, 23-first thread segment, 24-second thread segment, 25-first cathode thread segment, 26-second cathode thread segment, 27-first metal tube assembly, 28-second metal tube assembly. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The purpose of the present invention is to provide a micro cathode arc thruster, which improves the total impulse of the micro cathode arc thruster by changing the physical form of the propulsion medium of the micro cathode arc thruster and adjusting the supply form of the propulsion medium.

[0049] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] like Figures 1 to 28As shown: This embodiment provides a micro cathode arc thruster 100, including an anode structure 1, an insulating structure, a cathode emission structure 4 and a cathode metal tube structure 5. The cathode emission structure 4 is located on the inner side of the anode structure 1, and an insulating structure is provided between the cathode emission structure 4 and the anode structure 1. A plurality of cathode channels 18 are provided at the front end of the cathode emission structure 4. The diameter of the cathode channel 18 is 0.05 mm, and the length of the cathode channel 18 is 6 mm. A channel for filling liquid metal is provided in the cathode emission structure 4. The liquid metal is a gallium-indium alloy. The cathode channel 18 is connected to the channel. The rear end of the cathode emission structure 4 is used to connect with the cathode metal tube structure 5. The cathode emission structure 4 and the cathode metal tube structure 5 form a cathode structure. The cathode metal tube structure 5 is also used to fill the liquid metal. The cathode metal tube structure 5 acts as a wire, and brass with good conductivity is selected as the manufacturing material. The cathode emission structure 4 of this embodiment acts as both an electrode and a storage device for liquid metal, thereby significantly simplifying the propulsion fluid supply system and effectively reducing the structure of the micro-cathode arc thruster. During the operation of the micro-cathode arc thruster 100, the liquid metal is distributed on the surface of the cathode emission structure 4 driven by the pressure difference between the inside and outside of the cathode emission structure 4. The micro-cathode arc thruster of this embodiment adjusts the supply form of the propulsion fluid by changing the physical form of the micro-cathode arc thruster. By using liquid metal as the propulsion fluid, the liquid fluid in the pipeline reaches the surface of the cathode emission structure 4 of the thruster under the action of gravity. The amount of fluid on the surface of the cathode emission structure 4 increases, thereby improving the total impulse of the micro-cathode arc thruster and solving the problem of low total impulse of the micro-cathode arc thruster 100.

[0051] Specifically, this embodiment also includes a support structure 6 and a connecting structure 7, both of which are located outside the cathode emission structure 4, and the support structure 6 is located between the anode structure 1 and the connecting structure 7, and the connecting structure 7 is used to connect the cathode emission structure 4 and the cathode metal tube structure 5.

[0052] In this embodiment, the insulation structure includes a first insulation structure 2 and a second insulation structure 3. The first insulation structure 2 and the second insulation structure 3 are made of boron nitride ceramic. The surfaces of the first insulation structure 2 and the second insulation structure 3 are both coated with a conductive coating to ensure communication between the cathode emission structure 4 and the anode structure 1. The conductive coating is mostly made of a carbon-based material. During thruster operation, a pulsed high voltage of hundreds of volts is applied to the cathode emission structure 4 and the anode structure 1. Under the influence of the high voltage, an arc breaks through the conductive coating, resulting in the generation of plasma around the interface between the cathode emission structure 4 and the insulation structure. Under the influence of the external magnetic field, the plasma is guided away from the thruster. The interior of the first insulation structure 2 is a hollow structure and is provided with a first insulation step 8. The first cathode step 9 of the cathode emission structure 4 abuts against the first insulation step 8. The interior of the second insulation structure 3 is also a hollow structure. The front end of the second insulation structure 3 abuts against the second cathode step 10 of the cathode emission structure 4 and the rear end of the first insulation structure 2. The second insulation step 11 of the second insulation structure 3 abuts against the first anode step 12 on the inner wall of the anode structure 1, preventing the insulation structure from falling off and improving the stability of the overall structure. When the micro cathode arc thruster 100 is working, a voltage of several hundred volts penetrates the gap of the conductive coating to form an arc, resulting in the generation of plasma around the cathode-insulator interface. Under the action of an external magnetic field, the plasma is guided to the far side.

[0053] In this embodiment, the function of the anode structure 1 is to provide high voltage for discharge. The anode structure 1 includes an anode body 13 and a lead wire 14. The anode body 13 is made of brass. The interior of the anode body 13 is a hollow structure. The inner wall of the anode body 13 is provided with a first anode step 12. The front end of the lead wire 14 is connected to the rear end of the anode body 13, and the lead wire 14 passes through the support structure 6 and the connecting structure 7 in sequence.

[0054] In this embodiment, the cathode emission structure 4 is made of brass, and a protrusion 16 is provided at the front end of the cathode emission structure 4. The surface of the protrusion 16 is flush with the front end of the first insulating structure 2. The protrusion 16 is provided with a plurality of coaxial annular grooves 17 and a plurality of coaxial layers of cathode channels 18. Each layer of cathode channels 18 includes a plurality of cathode channels 18. Two adjacent annular grooves 17 are connected by a plurality of channels 19. The bottom surface of the channel 19 is flush with the bottom surface of the annular groove 17. The arrangement of the channel 19 and the annular groove 17 ensures that no matter where the liquid metal flows out from the cathode channel 18, it will eventually cover the entire surface of the cathode emission structure 4, and the arc can act more on the liquid metal during the discharge process. During operation of the micro-cathode arc thruster 100, the arc ablates the cathode emitter structure 4, causing the temperature of the cathode emitter structure 4 to rise, thereby melting the low-melting-point metal within the cathode channels 18. Because the pressure inside the cathode channels 18 is greater than the pressure outside the cathode channels 18, the liquid metal is forced out of the channels 18. At the surface of the cathode emitter structure 4, the pressure difference between the two ends of the liquid metal reaches equilibrium with the surface tension of the liquid droplet. The liquid metal flows out of the cathode channels 18, forming a liquid column under the action of surface tension, with the height of the liquid column flush with the front end of the first insulating structure 2.

[0055] In this embodiment, the interior of the support structure 6 is a hollow structure, the front end of the support structure 6 is against the rear end of the anode structure 1, and the rear end of the support structure 6 is against the front end of the connecting structure 7. The support structure 6 is provided with a first through hole 20 for the lead wire 14 to pass through.

[0056] In this embodiment, the interior of the connecting structure 7 is a hollow structure, and the connecting structure 7 is provided with a second through hole 21 for the lead wire 14 to pass through. The inner wall of the connecting structure 7 is provided with a connecting step 22. The front end of the cathode metal tube structure 5 is abutted against the connecting step 22. The inner wall between the connecting step 22 and the front end of the connecting structure 7 is provided with a first thread segment 23, and the inner wall between the connecting step 22 and the rear end of the connecting structure 7 is provided with a second thread segment 24. The first thread segment 23 is threadedly connected to the first cathode thread segment 25 on the outer wall of the cathode emission structure 4, and the second thread segment 24 is threadedly connected to the second cathode thread segment 26 on the outer wall of the cathode metal tube structure 5.

[0057] In this embodiment, the cathode metal tube structure 5 is L-shaped, and the cathode metal tube structure 5 includes a first metal tube component 27 and a second metal tube component 28. The interior of the first metal tube component 27 and the interior of the second metal tube component 28 are both hollow structures. The first metal tube component 27 and the second metal tube component 28 are vertically connected. The inner wall of the first metal tube component 27 is provided with a cathode metal tube step 15. The rear end of the cathode emission structure 4 is against the cathode metal tube step 15. The inner diameter of the cathode emission structure 4 is the same as the inner diameter of the cathode metal tube structure 5.

[0058] In this embodiment, the liquid metal is restrained by the self-generated gravity of the liquid metal, the friction of the cathode structure, the surface tension, etc. Figure 28 As shown, assuming the vertical section of the cathode structure is L1 high, the horizontal section of the cathode structure is L2 long, the inner diameter of the cathode structure is D, the inner diameter of the cathode channel 18 is d, and the external ambient pressure is P0, the liquid enters the cathode structure from end A, fills the entire cathode structure, and flows out from the cathode channel 18 at end B. In the case considered, the liquid metal is an incompressible fluid, and its flow is similar to a typical circular tube laminar flow. Assuming that its viscosity coefficient does not change with flow rate, considering the flow in the horizontal section of the cathode structure, we have:

[0059] PS1=F+P0S2

[0060] Wherein, P is the liquid pressure at the cathode channel 18, F is the liquid surface tension, and P0 is the ambient back pressure. is the cross-sectional area of ​​the cathode channel 18, and S2 is the liquid surface area;

[0061] When the above equation reaches equilibrium, the liquid is stable.

[0062] And for F:

[0063] F=γ / r

[0064] Where γ is the wetting potential energy and r is the curvature radius of the metal droplet.

[0065] P is related to L1 and L2, F and S2 are closely related to the liquid height H and the aperture d of the cathode channel 18 (that is, the surface tension of the liquid is closely related to the surface area of ​​the liquid). In other words, the height of the liquid column of the liquid metal propulsion fluid at the cathode channel 18 is closely related to L1, L2 and d (the liquid column height is positively correlated with L1 and negatively correlated with L2 and d). When designing the thruster structure, these three structural parameters are related to the normal supply of the thruster propulsion fluid and are extremely important.

[0066] This embodiment analyzes the physical properties of liquid metal working fluid and, based on the structure of a conventional solid metal working fluid micro-cathode arc thruster 100, incorporates the properties of liquid metal and relevant fluid mechanics knowledge to develop a micro-cathode arc thruster 100. The cathode emitter structure 4 employs a plurality of cathode channels 18 at the front end to ensure that the inter-electrode pulse arc can reach the liquid metal surface, allowing the inter-electrode arc to ablate the liquid metal, thereby generating directional thrust. Through a rational design, the internal and external pressure differential of the cathode structure is balanced with the surface tension of the liquid metal at the cathode channels 18, ensuring a stable supply of propulsion fluid during operation. The liquid metal supply is controlled by the cathode channels 18 at the front end of the cathode emitter structure 4. This embodiment significantly improves the total impulse of the micro-cathode arc thruster 100 and simplifies its propulsion fluid supply system.

[0067] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A micro cathode arc thruster, characterized in that: The cathode emitting device comprises an anode structure, an insulating structure, a cathode emitting structure and a cathode metal tube structure, wherein the cathode emitting structure is located inside the anode structure, the insulating structure is provided between the cathode emitting structure and the anode structure, a plurality of cathode channels are provided at the front end of the cathode emitting structure, a channel for filling liquid metal is provided in the cathode emitting structure, the cathode channels are connected to the channels, and the rear end of the cathode emitting structure is used to connect to the cathode metal tube structure; The insulating structure includes a first insulating structure and a second insulating structure. The interior of the first insulating structure is a hollow structure. The first insulating structure is provided with a first insulating step. The first cathode step of the cathode emission structure is offset against the first insulating step. The interior of the second insulating structure is a hollow structure. The front end of the second insulating structure is offset against the second cathode step of the cathode emission structure and the rear end of the first insulating structure. The second insulating step of the second insulating structure is offset against the first anode step on the inner wall of the anode structure.

2. The micro cathode arc thruster according to claim 1, characterized in that: It also includes a supporting structure and a connecting structure, both of which are located outside the cathode emission structure. The supporting structure is located between the anode structure and the connecting structure, and the connecting structure is used to connect the cathode emission structure and the cathode metal tube structure.

3. The micro cathode arc thruster according to claim 2, characterized in that: The anode structure includes an anode body and a lead wire. The anode body is made of brass. The interior of the anode body is a hollow structure. The inner wall of the anode body is provided with the first anode step. The front end of the lead wire is connected to the rear end of the anode body, and the lead wire passes through the support structure and the connecting structure in sequence.

4. The micro cathode arc thruster according to claim 1, characterized in that: The cathode emission structure is made of brass, and a protrusion is provided at the front end of the cathode emission structure. The protrusion is provided with a plurality of coaxial annular grooves and a plurality of cathode channels. Two adjacent annular grooves are connected by a plurality of channels, and the bottom surface of the channel is flush with the bottom surface of the annular groove.

5. The micro cathode arc thruster according to claim 3, characterized in that: The interior of the support structure is a hollow structure, the front end of the support structure abuts against the rear end of the anode structure, the rear end of the support structure abuts against the front end of the connection structure, and the support structure is provided with a first through hole for the lead wire to pass through.

6. The micro cathode arc thruster according to claim 3, characterized in that: The interior of the connecting structure is a hollow structure, and the connecting structure is provided with a second through hole for the lead wire to pass through. The inner wall of the connecting structure is provided with a connecting step, and the front end of the cathode metal tube structure is abutted against the connecting step. The inner wall between the connecting step and the front end of the connecting structure is provided with a first threaded segment, and the inner wall between the connecting step and the rear end of the connecting structure is provided with a second threaded segment. The first threaded segment is threadedly connected to the first cathode threaded segment of the outer wall of the cathode emission structure, and the second threaded segment is threadedly connected to the second cathode threaded segment of the outer wall of the cathode metal tube structure.

7. The micro cathode arc thruster according to claim 1, characterized in that: The cathode metal tube structure includes a first metal tube assembly and a second metal tube assembly. The interior of the first metal tube assembly and the interior of the second metal tube assembly are both hollow structures. The first metal tube assembly and the second metal tube assembly are vertically connected. The inner wall of the first metal tube assembly is provided with a cathode metal tube step, and the rear end of the cathode emission structure is against the cathode metal tube step.

8. The micro cathode arc thruster according to claim 1, characterized in that: The liquid metal is a gallium-indium alloy.

9. The micro cathode arc thruster according to claim 1, characterized in that: The diameter of the cathode channel is 0.05 mm, and the length of the cathode channel is 6 mm.

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