Electrothermal pulse plasma thruster

Abstract

The invention discloses an electric heating type pulse plasma thruster, which is applied to the technical field of electric propulsion and is used for solving the problems of non-uniform ablation and lower specific impulse of an electric heating type pulse plasma thruster in the prior art. Specifically, an ablation cavity extending in the axis direction of the thruster is formed in the doped working medium; a cathode is arranged at one end of the doped working medium along the axis direction, and an anode is arranged at the other end of the doped working medium along the axis direction; the anode is connected with the cathode of an external power supply, and the cathode is connected with the anode of the external power supply; an insulating shell is arranged outside the doped working medium; the spark plug is embedded into the cathode, and the injection direction of the spark plug coincides with the axis direction. The spraying direction of the sparking plug is arranged to coincide with the axis direction, so that the ablation uniformity is improved; the sparking plug is embedded into the cathode, the movement direction of the electric arc is the same as that of the peeled ablation product, the ablation product continuously obtains energy from the electric arc, higher acceleration efficiency is achieved, and the specific impulse of the thruster is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric propulsion, in particular to an electrically heated pulsed plasma thruster. BACKGROUND

[0002] With the development of commercial spaceflight, the launch quantity of microsatellites is growing explosively, and the microsatellites need to continuously adjust their orbits and attitude angles in orbit operation. The current orbit adjustment mainly relies on the power provided by thrusters (engines), among which, the electric thruster uses electric energy to ionize and accelerate the working medium to generate a high-speed jet. Due to its high specific impulse (impulse generated by unit weight of propellant) and thrust accuracy, the electric thruster is applied more and more. Among various electric thrusters, the electrically heated pulsed plasma thruster has a high thrust power ratio and a simple structure due to its coaxial front and rear structure and pulsed working principle, is suitable for application of microsatellites, and has a good application prospect.

[0003] At present, the electric spark generated by the spark plug in the conventional electrically heated pulsed plasma thruster is asymmetric about the axis, which causes the electric arc to be generated along the position close to the spark plug, resulting in uneven ablation of the working medium in the circumferential direction. In addition, the acceleration principle of electric heating leads to a low average speed of ablation products. According to the principle of momentum conservation, the impulse generated by unit mass of the working medium, i.e. the specific impulse, is low. The low specific impulse seriously limits the application of the thruster. SUMMARY

[0004] The present application provides an electrically heated pulsed plasma thruster to solve the problems of uneven ablation and low specific impulse of the electrically heated pulsed plasma thruster in the prior art.

[0005] The technical scheme provided by the present application is as follows: The present application provides an electrically heated pulsed plasma thruster, comprising: a doped working medium, a cathode, an anode, a spark plug and an insulating shell; The doped working medium is provided with an ablation cavity extending along the axial direction of the thruster. The cathode is arranged at one end of the doped working medium along the axial direction, and the anode is arranged at the other end of the doped working medium along the axial direction. The anode is connected to the negative electrode of an external power supply, and the cathode is connected to the positive electrode of the external power supply. The doped working medium is externally provided with an insulating shell; The spark plug is embedded in the cathode, and the injection direction of the spark plug coincides with the axial direction.

[0006] Optionally, the doped working medium is a working medium material sintered by a polytetrafluoroethylene doped with a target metal powder, wherein the target metal powder is a metal powder with an ionization energy lower than that of fluorine; and the mass fraction of the target metal powder is less than 5%.

[0007] Optionally, the anode is provided with an anode extension part extending away from the axis, the cathode is provided with a cathode extension part extending away from the axis, and the insulating shell is sleeved between the anode extension part and the cathode extension part.

[0008] Optionally, the outer surface of the anode extension part is a cylindrical surface, and the inner surface of the anode extension part is a conical surface.

[0009] Optionally, the electrothermal pulsed plasma thruster further comprises a magnetic element. The magnetic element is arranged inside the insulating shell, and the magnetic element is circumferentially sleeved outside the doped working substance; the magnetic element is used to generate a magnetic field in the same direction as the axis at the axis of the thruster.

[0010] Optionally, the magnetic element is a magnet or an electromagnetic coil.

[0011] Optionally, the magnet is a ring magnet.

[0012] Optionally, the insulating shell is of a split structure, and the insulating shell comprises a front insulating sleeve and a rear insulating sleeve. The front insulating sleeve and the rear insulating sleeve are detachably fixedly connected through bolts.

[0013] Optionally, the electrothermal pulsed plasma thruster further comprises an energy storage capacitor. One end of the energy storage capacitor is connected with the anode, and the other end of the energy storage capacitor is connected with the cathode.

[0014] Optionally, the electrothermal pulsed plasma thruster further comprises an ignition circuit. The center electrode of the spark plug is fixedly provided with a lead wire, and the ignition circuit is connected with the spark plug through the lead wire.

[0015] The beneficial effects of the present application are as follows: The present application sets the injection direction of the spark plug to coincide with the axis direction, enhances the symmetry of the electric spark generated by the spark plug about the axis of the thruster, can make the position of the electric arc symmetrical about the axis of the thruster, makes the ablation and peeling of the inner wall surface of the doped working substance more uniform, and improves the uniformity of ablation. The spark plug is embedded in the cathode, the electric arc moves from the spark plug to the side where the anode is located, and the electric arc continuously ablates the inner wall of the doped working substance during the process of spreading from the side where the cathode is located to the side where the anode is located, and produces ablation products. Since the rear end of the side where the anode is located is in a vacuum environment, the ablation products move to the side where the anode is located after being produced, the electric arc and the ablated ablation products move in the same direction, the ablation products can continuously obtain energy from the electric arc, achieve higher acceleration efficiency, and realize the improvement of the specific impulse of the electrothermal pulsed plasma thruster.

[0016] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The purposes and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and together with the description serve to explain the present application. In the drawings: Figure 1 The first structure schematic diagram of the electrically heated pulsed plasma thruster in the embodiment of the present application; Figure 2 The cross-sectional structure schematic diagram of the electrically heated pulsed plasma thruster in the embodiment of the present application; Figure 3 The second structure schematic diagram of the electrically heated pulsed plasma thruster in the embodiment of the present application.

[0018] In the figure, 1-doped working substance; 2-cathode; 3-anode; 4-spark plug; 5-insulating shell; 6-magnetic element; 7-front insulating sleeve; 8-rear insulating sleeve; 9-bolt of M2.5*12; 10-nut of M2.5; 11-bolt of M3*5; 12-gasket of M3; 13-ignition circuit; 21-cathode extension; 22-cathode connecting part; 31-anode extension; 32-anode connecting part. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and beneficial effects of the present application more clear, the technical scheme in the embodiment of the present application will be described clearly and completely below in combination with the drawings in the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiments of the present application, and is not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] Firstly, the application scene and design idea of the embodiment of the present application are simply introduced.

[0021] Currently, among various electric thrusters, the electrothermal pulsed plasma thruster has a high thrust power ratio, a simple structure and other characteristics due to its coaxial front-back structure and pulsed working principle, and is suitable for application in microsatellites and has a good application prospect. The electric spark generated by the spark plug in the conventional electrothermal pulsed plasma thruster is asymmetric about the axis, which causes the electric arc to be generated along the position close to the spark plug, resulting in uneven ablation of the working medium in the circumferential direction. In addition, the acceleration principle of electrothermal acceleration causes the average speed of the ablation products to be low, and according to the principle of momentum conservation, the impulse generated by the unit mass of the working medium, i.e., the specific impulse, is low. The low specific impulse seriously limits the application of the thruster.

[0022] Therefore, in the embodiments of the present application, the electrothermal pulsed plasma thruster comprises: a doped working medium, a cathode, an anode, a spark plug and an insulating shell; the doped working medium is provided with an ablation cavity extending along the axis direction of the thruster; one end of the doped working medium along the axis direction is provided with the cathode, and the other end of the doped working medium along the axis direction is provided with the anode; the anode is connected with the negative electrode of an external power supply, and the cathode is connected with the positive electrode of the external power supply; the doped working medium is externally provided with the insulating shell; and the spark plug is embedded in the cathode and the jet direction of the spark plug coincides with the axis direction. In this way, the jet direction of the spark plug coincides with the axis direction, the symmetry of the electric spark generated by the spark plug about the axis of the thruster is enhanced, the position where the electric arc is generated is symmetrical about the axis of the thruster, the ablation and peeling of the inner wall surface of the doped working medium are more uniform, and the uniformity of ablation is improved. The spark plug is embedded in the cathode, the electric arc is generated from the spark plug to the side where the anode is located, and the inner wall surface of the doped working medium is continuously ablated in the process of the electric arc spreading from the side where the cathode is located to the side where the anode is located, to generate ablation products. Since the rear end of the side where the anode is located is in a vacuum environment, the ablation products move to the side where the anode is located after being generated, the movement direction of the electric arc is the same as that of the peeled ablation products, the ablation products can continuously obtain energy from the electric arc, a higher acceleration efficiency is achieved, and the specific impulse of the electrothermal pulsed plasma thruster is improved.

[0023] After introducing the application scenarios and design ideas of the embodiments of the present application, the technical solutions provided by the embodiments of the present application are described in detail.

[0024] The embodiments of the present application provide an electrothermal pulsed plasma thruster, as shown in Figure 1 The electrothermal pulsed plasma thruster at least comprises: a doped working medium 1, a cathode 2, an anode 3, a spark plug 4 and an insulating shell 5; The doped working medium 1 is provided with an ablation cavity extending along the axis direction of the thruster; one end of the doped working medium 1 along the axis direction is provided with the cathode 2, and the other end of the doped working medium 1 along the axis direction is provided with the anode 3; the anode 3 is connected with the negative electrode of an external power supply, and the cathode 2 is connected with the positive electrode of the external power supply; the doped working medium 1 is externally provided with the insulating shell 5; The spark plug 4 is embedded in the cathode 2 and arranged with the jet direction coinciding with the axial direction.

[0025] In Figure 1 In the electrically heated pulsed plasma thruster shown, a doping working substance 1 is provided with an ablation cavity extending along the axial direction of the thruster, for accommodating an electric arc and generating plasma by ablation of the doping working substance 1 by the electric arc. The doping working substance 1 can be cylindrical or conical in shape. A cathode 2 is fixedly arranged at one end of the doping working substance 1 along the axial direction, connected to the positive pole of an external power source, and is the starting point of the electric arc. An anode 3 is fixedly arranged at the other end of the doping working substance 1 along the axial direction, connected to the negative pole of the external power source, and is the end point of the electric arc. A spark plug 4 is embedded in the cathode 2 and arranged through the cathode 2, with the jet opening of the spark plug 4 facing the axial direction of the thruster, the jet direction of the spark plug 4 coinciding with the axial direction of the thruster, and the spark plug 4 used to release an electric spark to initiate the electric arc when ignited. An insulating shell 5 is wrapped around the outer sidewall of the doping working substance 1, and the connection part of the cathode 2 to the doping working substance 1 is wrapped by the insulating shell 5, and the connection part of the anode 3 to the doping working substance 1 is wrapped by the insulating shell 5, and the insulating shell 5 is used to provide electrical insulation and protection. The insulating shell 5 can be made of boron nitride ceramic, alumina ceramic or zirconia ceramic, and the insulating shell 5 can also be made of quartz crystal ceramic or ceramic matrix composite.

[0026] In practical application, the electrically heated pulsed plasma thruster works in vacuum. An external power source applies high voltage between the cathode 2 and the anode 3. When the spark plug 4 releases an electric spark, the electric spark is generated near the cathode 2, and an electric arc is generated along the cathode 2 and reaches the anode 3. The electric arc continuously releases energy in the process of extending along the cathode 2 to the anode 3 in the ablation chamber. The current of the electric arc can reach thousands of amperes, ensuring sufficient ablation energy. The high temperature of the electric arc ablates the inner wall of the doped working substance 1, generating ablation products including neutral products and charged particles. The neutral products in the ablation products are ejected at low speed to the outside under the pressure difference between the inside and the outside, while the charged particles in the ablation products are gathered to the axis under the self-pinching effect of the large current, forming a high-temperature and high-pressure plasma, which is ejected at high speed to the outside due to the thermal pressure. In this way, the ejection direction of the spark plug 4 coincides with the axial direction, enhancing the symmetry of the electric spark generated by the spark plug 4 about the axis of the thruster, so that the position of the electric arc is symmetrical about the axis of the thruster, and the ablation and peeling of the inner wall of the doped working substance 1 are more uniform, improving the uniformity of ablation. Since the electric arc is generated from the spark plug 4 and spreads from the side where the cathode 2 is located to the side where the anode 3 is located in the ablation chamber, the wall is continuously ablated in the spreading process, and the ablation products are also simultaneously started to move. Since the rear end of the side where the anode 3 is located is in a vacuum environment, the ablation products move to the rear end after being generated. When the spark plug 4 is placed on the side where the cathode 2 is located, the electric arc moves to the side where the anode 3 is located, and the direction of movement of the ablation products is the same as that of the electric arc. The ablation products can continuously obtain energy from the electric arc, achieve higher acceleration efficiency, and improve specific impulse.

[0027] In a possible implementation, the doped working substance is a working substance material sintered by polytetrafluoroethylene doped with target metal powder, wherein the target metal powder is a metal powder with ionization energy lower than that of fluorine; and the mass fraction of the target metal powder is less than 5%.

[0028] In practical applications, polytetrafluoroethylene (PTFE) is a polymer material with excellent insulation performance, high temperature resistance and chemical stability, which can maintain stable performance in high temperature, high pressure and vacuum environment. Because the ionization energy of the target metal powder is lower than that of carbon and fluorine in PTFE, the ionization degree of the ablation product of the doped working medium is higher than that of the pure PTFE material used in the traditional electrothermal pulse plasma thruster under the same discharge energy, which improves the proportion of charged particles subjected to the acceleration effect of electrothermal and magnetic field acceleration in the overall ablation product, and the charged particles are more susceptible to the acceleration effect of electrothermal acceleration and magnetic mirror acceleration, which can make the average speed of the ablation product higher, so the specific impulse of the thruster can be effectively improved. The mass fraction of the target metal powder is less than 5%, which can avoid the breakdown of the doped working medium under high voltage, that is, the current forms a path in the doped working medium, leading to material failure, and also can improve the ionization degree of the doped working medium while avoiding the sacrifice of the insulation performance of the material, achieving a balance between ionization degree and insulation. The target metal powder can be copper powder.

[0029] In a possible implementation, referring to Figure 2 As shown in the figure, the anode is provided with an anode extension 31 away from the axis direction, the cathode is provided with a cathode extension 21 away from the axis direction, and the insulating shell is sleeved between the anode extension 31 and the cathode extension 21.

[0030] In practical applications, the cathode includes a cathode extension 21 and a cathode connection part 22, wherein the cathode extension 21 is arranged outside the insulating shell and connected with the positive pole of the external power supply, which is the starting point of the electric arc; the cathode connection part 22 is arranged inside the insulating shell and connected with the doped working medium 1. Correspondingly, the anode includes an anode extension 31 and an anode connection part 32, wherein the anode extension 31 is arranged outside the insulating shell and connected with the negative pole of the external power supply, which is the end point of the electric arc; the anode connection part 32 is arranged inside the insulating shell and connected with the doped working medium 1.

[0031] In specific implementation, the anode extension 31 has various structures to realize its functions, referring to Figure 2 As shown in the figure, the outer surface of the anode extension 31 is a cylindrical surface, and the inner surface of the anode extension 31 is a conical surface.

[0032] In practical applications, the outer surface of the anode extension 31 is a cylindrical surface, and the inner surface is a conical surface, to form an expanding nozzle structure. When the neutral product passes through the anode extension 31, the conical inner surface can gradually expand the flow cross section of the product, thereby reducing the flow rate of the product and increasing its pressure, and the kinetic energy of the product is increased, realizing the acceleration of the neutral product.

[0033] In a possible implementation, referring to Figure 2As shown, the electrothermal pulsed plasma thruster further comprises a magnetic element 6; The magnetic element 6 is arranged inside the insulating shell and circumferentially sleeved outside the doped working substance 1, and is used to generate a magnetic field parallel to the axial direction of the thruster at the axial line of the thruster.

[0034] In actual application, the magnetic element 6 is arranged inside the insulating shell and circumferentially sleeved outside the doped working substance 1, so as to ensure that the magnetic field can uniformly act on the working substance material and provide a basis for the subsequent "magnetic mirror" effect. The magnetic field generated by the magnetic element 6 at the axial line of the thruster is parallel to the axial direction of the thruster, which is helpful to form a stable magnetic field distribution in the thruster cavity and provides favorable conditions for the acceleration of charged particles. The magnetic element 6 can effectively accelerate the charged particles generated in the thruster through the "magnetic mirror" effect. In the "magnetic mirror" effect, the speed of the charged particles perpendicular to the magnetic field direction decreases, and the speed parallel to the magnetic field direction increases in the place where the magnetic field strength is weak. The magnetic field generated by the magnetic element 6 at the axial line of the thruster is parallel to the axial direction of the thruster, and the axial magnetic field is the strongest inside the ablation cavity. During the process of generating ablation products by the high-temperature arc ablation of the inner wall of the working substance, the axial speed of the charged particles parallel to the magnetic field direction will increase, effectively increasing the speed of the ablation product ejection, and realizing the improvement of the specific impulse performance of the electrothermal pulsed plasma thruster.

[0035] Specifically, the magnetic element is a magnet or an electromagnetic coil. The magnet can be a permanent magnet. The electromagnetic coil generates a magnetic field by electrification, and the strength and direction of the magnetic field can be adjusted by controlling the current. The magnet can be a ring magnet. The ring magnet can be sleeved outside the doped working substance to provide a uniform and stable axial magnetic field for the ablation cavity of the electrothermal pulsed plasma thruster. The ring magnet can provide a relatively uniform magnetic field distribution, and the strongest point of the magnetic field is located in the middle of the doped working substance, which is helpful to the stable acceleration of the charged particles in the ablation cavity.

[0036] In specific implementation, the insulating shell has various structures to realize its functions, which can be referred to in the description of the insulating shell. Figure 2 As shown, the insulating shell is a split structure, and the insulating shell comprises a front insulating sleeve 7 and a rear insulating sleeve 8. The front insulating sleeve 7 and the rear insulating sleeve 8 are detachably fixedly connected through bolts.

[0037] In practical application, the magnetic element 6 is fixed between the front insulating sleeve 7 and the rear insulating sleeve 8, the cathode extension 21 and the anode extension 31 are fixed at the front of the front insulating sleeve 7 and the rear of the rear insulating sleeve 8 respectively, and the doped working substance 1 is clamped between the cathode connecting part 22 and the anode connecting part 32. In specific assembly, the front insulating sleeve 7 and the rear insulating sleeve 8 are tightly connected through 6 M2.5*12 bolts 9 and 6 M2.5 nuts 10, and the magnetic element 6 is fixed between the front insulating sleeve 7 and the rear insulating sleeve 8. The doped working substance 1 is inserted into the hole of the magnetic element 6. There are 4 M3 threaded holes on the front insulating sleeve 7 and the rear insulating sleeve 8 respectively, the cathode extension 21 and the anode extension 31 are tightly connected with the front insulating sleeve 7 and the rear insulating sleeve 8 through 4 M3*5 bolts 11 and 4 M3 washers 12 respectively, the cathode connecting part 22 and the anode connecting part 32 are in contact with the doped working substance 1, and the cathode and the anode clamp and fix the doped working substance 1 therebetween. The cathode is fixed with a lead wire through one of the 4 M3 threaded holes, and is connected with the positive pole of the external power supply, and the anode is fixed with a lead wire through one of the 4 M3 threaded holes, and is connected with the negative pole of the external power supply.

[0038] In a possible implementation, referring to Figure 3 As shown in the figure, the electrothermal pulsed plasma thruster further comprises an energy storage capacitor C. One end of the energy storage capacitor is connected with the anode 3, and the other end of the energy storage capacitor is connected with the cathode 2.

[0039] In practical application, the external power supply VIN is generally a high-voltage power supply. When the external power supply VIN applies a high voltage between the cathode 2 and the anode 3, the energy storage capacitor stores energy for the electrothermal pulsed plasma thruster. When the spark plug 4 releases an electric spark, the energy storage capacitor releases the stored electric energy to the cathode 2 and the anode 3.

[0040] In a possible implementation, the electrothermal pulsed plasma thruster further comprises an ignition circuit 13. The center electrode of the spark plug 4 is fixedly provided with a lead wire, and the ignition circuit 13 is connected with the spark plug 4 through the lead wire.

[0041] In practical application, the spark plug 4 is fixed with a lead wire through the M2 thread of the center electrode, and the ignition circuit 13 is connected with the spark plug 4 through the lead wire. The ignition circuit 13 is used for controlling the spark plug 4 to release an electric spark.

[0042] It should be noted that, although several units or sub-units of the device are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more units described above can be embodied in one unit. Conversely, the features and functions of one unit described above can be further divided into units embodied by multiple units.

[0043] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to encompass within their scope all such variations and modifications as are included within the spirit and scope of the application.

[0044] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application encompass all such modifications and variations as fall within the scope of the claims and their equivalents.

Claims

1. An electrothermal pulsed plasma thruster, characterized by, The application relates to a thruster, which comprises the following parts: a doped working substance, a cathode, an anode, a spark plug and an insulating shell; an ablation cavity is arranged in the doped working substance and extends along the axial direction of the thruster; the cathode is arranged at one end of the doped working substance along the axial direction, and the anode is arranged at the other end of the doped working substance along the axial direction; the anode is connected with the negative pole of an external power supply, and the cathode is connected with the positive pole of the external power supply; the doped working substance is externally provided with the insulating shell; the spark plug is embedded in the cathode, and the injection direction of the spark plug is coincident with the axial direction.

2. The electro-thermal pulsed plasma thruster of claim 1, wherein, The doped working substance is a working substance material sintered by a polytetrafluoroethylene doped with target metal powder, wherein the target metal powder is metal powder with ionization energy lower than that of fluorine; the mass fraction of the target metal powder is less than 5%.

3. The electro-thermal pulsed plasma thruster of claim 1, wherein, The anode is provided with an anode extension part away from the axial direction, the cathode is provided with a cathode extension part away from the axial direction, and the insulating shell is sleeved between the anode extension part and the cathode extension part.

4. The electrothermal pulsed plasma thruster of claim 3, wherein, The outer surface of the anode extension part is a cylindrical surface, and the inner surface of the anode extension part is a conical surface.

5. Electrothermal pulsed plasma thruster according to any of claims 1 to 4, characterized in that Further comprising: a magnetic element; the magnetic element is arranged inside the insulating shell, and the magnetic element is circumferentially sleeved outside the doped working substance; the magnetic element is used for generating a magnetic field same as the axial direction at the axial line of the thruster.

6. The electro-thermal pulsed plasma thruster of claim 5, wherein, The magnetic element is a magnet or an electromagnetic coil.

7. The electro-thermal pulsed plasma thruster of claim 6, wherein, The magnet is a ring magnet.

8. The electro-thermal pulsed plasma thruster of claim 5, wherein, The insulating shell is a split structure, and the insulating shell comprises a front insulating sleeve and a rear insulating sleeve; the front insulating sleeve and the rear insulating sleeve are detachably fixedly connected through bolts.

9. The electro-thermal pulsed plasma thruster of claim 8, wherein, Further comprising: an energy storage capacitor; one end of the energy storage capacitor is connected with the anode, and the other end of the energy storage capacitor is connected with the cathode.

10. The electrothermal pulsed plasma thruster of claim 9, wherein, Further comprising: an ignition circuit; a center electrode of the spark plug is fixedly provided with a lead wire, and the ignition circuit is connected with the spark plug through the lead wire.

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