A magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster

Abstract

The present invention relates to a magnetic field-assisted radio frequency pre-ionization type induction pulse plasma thruster, comprising a radio frequency pre-ionization coil, a pre-ionization cavity, an accelerating stage cavity, an induction acceleration coil, a bias magnetic field coil group and a gas distributor. The radio frequency pre-ionization coil is wound by a copper tube and installed outside the pre-ionization cavity. The pre-ionization cavity and the accelerating stage cavity are made of high temperature resistant insulating materials, and the whole forms a "T" shape. The bias magnetic field coil group can generate a magnetic field with adjustable strength, and the magnetic field distribution is parallel to the axial direction in the pre-ionization cavity and parallel to the surface of the induction coil in the accelerating stage cavity. The induction acceleration coil adopts a double-layer, multi-helix parallel planar annular structure. The present invention uses a radio frequency induction coupling method to pre-ionize the gas working medium, and effectively guides the pre-ionized gas working medium to the surface of the induction coil in the accelerating stage cavity through a special bias magnetic field distribution, which can effectively reduce the induced electromagnetic field intensity required for ionization and acceleration of the gas working medium.

Description

Technical Field

[0001] The present invention relates to the technical field of electric propulsion, and in particular to a magnetic field-assisted radio frequency pre-ionization induction pulse plasma thruster. Background Art

[0002] Interstellar exploration missions such as Mars orbit and asteroid patrol are important components of my country's medium- and long-term aerospace science and technology development strategy, and have put forward urgent development needs for high-performance and high-power electric propulsion systems. The inductive pulse plasma thruster is an electrodeless electromagnetic thruster. It does not have the electrode ablation problem inherent in Hall and ion thrusters. It also has the advantages of high specific impulse, high efficiency, high power, and multiple working fluids. However, the existing single-stage inductive pulse plasma thruster adopts an "ionization-acceleration" integrated structure, with a high operating voltage (tens of kilovolts) and a large single pulse energy (thousands of joules), which seriously limits its feasibility in space applications. The pre-ionization inductive pulse plasma thruster adopts a two-stage structure of "pre-ionization" and "acceleration", and uses "low pulse energy and high repetition frequency" to replace the "high pulse energy and low repetition frequency" working mode, which significantly reduces the operating pressure of key components and the structural size of the device, and has good development prospects. During the operation of the thruster, efficiently pre-ionizing the gaseous working fluid and quickly and accurately guiding it to the surface of the accelerating coil is beneficial to improving the acceleration process of the gaseous working fluid by the pulsed electromagnetic field generated by the main discharge, thereby improving the thruster's key parameters such as specific impulse and energy coupling efficiency. However, the current pre-ionization method and gaseous working fluid injection method have a poor effect on improving the performance of induction pulsed plasma thrusters, and there are many scientific and technical problems, making it difficult to apply them in practice. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a magnetic field-assisted radio frequency pre-ionization induction pulse plasma thruster, which pre-ionizes the gas working fluid through radio frequency inductively coupled discharge, and guides the pre-ionized gas working fluid to the surface of the acceleration coil through a bias magnetic field with a special distribution, thereby improving the ionization and acceleration process of the induction pulse plasma thruster and enhancing its propulsion performance.

[0004] A magnetic field-assisted radio frequency pre-ionization type induction pulse plasma thruster comprises: a radio frequency pre-ionization coil, a pre-ionization cavity, an accelerating stage cavity, an induction accelerating coil, a bias magnetic field coil group and a gas distributor. The pre-ionization cavity is connected to the accelerating stage cavity, the radio frequency pre-ionization coil is arranged outside the pre-ionization cavity and coaxial with the pre-ionization cavity, the induction accelerating coil is arranged inside the accelerating stage cavity, the bias magnetic field coil group is arranged outside the pre-ionization cavity and the induction accelerating coil and coaxial with the two, and the gas distributor is installed at the upstream central axis of the pre-ionization cavity.

[0005] The radio frequency pre-ionization coil is a copper tube wound into a multi-turn coaxial spiral structure, which is installed outside the pre-ionization chamber. The coil diameter, number of turns, distance between turns and other parameters are variable and are selected according to actual needs. Generally, the coil diameter is between 5 and 20 cm, the number of turns is between 5 and 20, and the distance between turns is between 0.3 and 2 cm. The copper tube is a hollow structure, and the inner diameter and outer diameter are selected according to actual needs. Generally, the inner diameter is between 0.5 and 3 mm, the outer diameter is between 1 and 6 mm, and the outer diameter is always larger than the inner diameter. The copper tube can be connected to a water cooling device to solve the problem of heat accumulation when working in a vacuum for a long time.

[0006] The pre-ionization chamber is made of high temperature resistant insulating materials such as quartz glass or alumina ceramics. It is cylindrical in shape as a whole, with an outer diameter smaller than the RF pre-ionization coil, a length greater than the RF pre-ionization coil, and a thickness selected according to actual needs. Generally speaking, the aspect ratio of the pre-ionization chamber is greater than 1, and the thickness is between 2 and 10 mm. A circular hole is opened at the upstream axis of the pre-ionization chamber for installing a gas distributor, and the downstream is connected to the acceleration stage chamber.

[0007] The accelerating stage cavity is made of high temperature resistant insulating materials such as quartz glass or alumina ceramics. The main body is a planar annular structure, the inner edge is connected to the downstream of the pre-ionization cavity, and the outer edge is provided with a enclosure structure with a height of several centimeters to improve the distribution of the gas working medium on the surface of the induction acceleration coil. The pre-ionization cavity and the accelerating stage cavity form a "T" shape as a whole, and the connection part between the two adopts a smooth transition structure.

[0008] The induction acceleration coil is a planar ring, arranged inside the acceleration stage cavity, and adopts a basic structure of double-layer, m spiral wires in parallel. The upper and lower coils are staggered and isolated by insulating materials with a thickness of several millimeters to ensure that the induced electromagnetic field is evenly distributed over the entire coil surface. Each spiral is made of enameled copper wire and is an Archimedean spiral structure. It is extended from the inner radial to the outer diameter of the enveloping ring and rotates 360° in total. The rotation angle between two adjacent spirals differs by n° and satisfies m×n=360. The inner diameter and outer diameter of the enveloping ring are selected according to actual needs.

[0009] The bias magnetic field coil group is composed of multiple coils arranged coaxially and in parallel, and is wound on a coil frame with enameled copper wire. By adjusting the number of turns and current, an axial magnetic field with adjustable strength is generated at the central axis of the pre-ionization chamber. By adjusting the coil diameter, position, number of turns and other parameters, the magnetic field distribution is parallel to the axial direction in the pre-ionization chamber, parallel to the surface of the induction coil in the acceleration stage chamber, and smoothly transitions at the connection position of the two chambers.

[0010] The gas distributor is a "T" shaped structure, with a cylindrical hole in the center of the upstream, a truncated cone in the downstream, and several circular holes evenly distributed along the circumference on the side, which are connected to the central circular hole upstream of the gas distributor. The gaseous medium enters from the upstream of the gas distributor, is distributed by the lateral circular holes downstream, and enters the pre-ionization chamber more evenly.

[0011] The working principle of the magnetic field-assisted RF pre-ionization induction pulse plasma thruster is as follows: when the thruster is working, the gas working medium enters the pre-ionization cavity from the gas distributor and diffuses forward. Under the action of a certain power RF voltage, the RF pre-ionization coil excites a rapidly changing electromagnetic field in the space inside the pre-ionization cavity, and then pre-ionizes the gas working medium in the form of inductive coupling discharge, and generates an initial plasma of a certain density. The gas working medium containing initial electrons moves along the direction of the magnetic flux lines under the guidance of the bias magnetic field and diffuses to the surface of the induction acceleration coil inside the acceleration stage cavity. Then, the external energy storage capacitor discharges to the induction acceleration coil through a fast closing switch, thereby inducing a high-intensity, pulsed angular electric field and radial magnetic field, which promotes the further ionization of the gas working medium and forms a ring-shaped plasma current sheet. The angular plasma current is accelerated by the axial Lorentz force in the radial magnetic field and generates thrust.

[0012] The beneficial effects of the present invention are:

[0013] 1. The present invention pre-ionizes the gas working fluid by using a radio frequency inductive coupling method, which can effectively reduce the induced electromagnetic field intensity required for ionization and acceleration of the gas working fluid, reduce the working voltage and single pulse energy of the thruster, and further reduce the operating pressure of components such as switching devices and capacitors.

[0014] 2. The present invention can effectively guide the pre-ionized gas working medium to the surface of the induction coil in the accelerating stage cavity through a special bias magnetic field structure, thereby increasing the utilization rate of the gas working medium and improving the acceleration process of the gas working medium by the induction pulse electromagnetic field.

[0015] 3. The present invention adopts a smooth transition design in the connection part between the pre-ionization chamber and the acceleration stage chamber to ensure that the discharge chamber surface is parallel to the magnetic flux lines, which can reduce the interference of the chamber structure on the gas working medium diffusion process and optimize the distribution of the pre-ionization gas working medium on the surface of the induction coil.

[0016] 4. The magnetic field-assisted radio frequency pre-ionization induction pulse plasma thruster proposed in the present invention adopts a two-stage structure of "pre-ionization" and "acceleration", and uses "low pulse energy, high repetition frequency" to replace the working mode of "large pulse energy, low repetition frequency", ensuring the overall electrode-free structure of the thruster. It has the advantages of high specific impulse, high efficiency, high power, and multiple working fluids, and is expected to meet the propulsion needs of interstellar exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1a An isometric view of a magnetic field-assisted radio frequency pre-ionization type inductive pulsed plasma thruster showing an embodiment of the present invention.

[0018] Figure 1b The axial cross-sectional view of a magnetic field-assisted radio frequency pre-ionization induction pulse plasma thruster shown in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of an induction acceleration coil according to an embodiment of the present invention.

[0020] Figure 3 A schematic diagram of the thruster cavity structure and bias magnetic field distribution according to an embodiment of the present invention.

[0021] The numbers in the figure are explained as follows:

[0022] Radio frequency pre-ionization coil 1, pre-ionization chamber 2, acceleration stage chamber 3, induction acceleration coil 4, bias magnetic field coil group 5, gas distributor 6. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is described in detail below in conjunction with embodiments.

[0024] like Figure 1a and Figure 1b As shown, a magnetic field assisted RF pre-ionization type induction pulse plasma thruster according to an embodiment of the present invention comprises: a RF pre-ionization coil 1, a pre-ionization chamber 2, an acceleration stage chamber 3, an induction acceleration coil 4, a bias magnetic field coil group 5 and a gas distributor 6. Specifically:

[0025] The RF pre-ionization coil 1 is wound from a copper tube into a multi-turn coaxial spiral structure, installed outside the pre-ionization chamber 2, with a coil diameter of 110 mm, 16 turns, and a turn-to-turn distance of 10 mm. The copper tube is a hollow structure with an inner diameter and an outer diameter of 2 mm and 3 mm, respectively. The copper tube can be connected to a water cooling device to solve the problem of heat accumulation when working for a long time in a vacuum.

[0026] The pre-ionization chamber 2 is made of quartz glass, with an outer diameter of 100 mm, a thickness of 3 mm, and a length of 200 mm. Generally speaking, the aspect ratio of the pre-ionization chamber 2 is greater than 1. A circular hole with a diameter of 14 mm is opened at the upstream axis of the pre-ionization chamber 2 for installing a gas distributor 6, and the downstream is connected to the acceleration stage chamber.

[0027] The accelerating stage cavity 3 is made of quartz glass, and the main body is a planar annular structure with an inner diameter of 100 mm, an outer diameter of 300 mm, and a thickness of 3 mm. The inner edge is connected to the downstream of the pre-ionization cavity 2, and the outer edge is provided with a 50 mm high enclosure structure to improve the distribution of the gas working medium on the surface of the induction acceleration coil 4. The pre-ionization cavity 2 and the accelerating stage cavity 3 form a "T" shape as a whole, and the connection part between the two adopts a smooth transition structure.

[0028] The induction acceleration coil 4 is a planar ring. Figure 2 As shown in the figure, a basic structure of double layers and 6 spirals in parallel is adopted. The solid line is the upper coil, and the dotted line is the lower coil. The upper and lower coils are arranged alternately and isolated by an insulating material with a thickness of 5 mm to ensure that the induced electromagnetic field is evenly distributed over the entire coil surface. Each spiral is made of enameled copper wire with a diameter of 1 mm. It is an Archimedean spiral structure, extending from the inner diameter to the outer diameter of the enveloping ring and rotating 360° in total. The rotation angle between two adjacent spirals differs by 60°, and the inner and outer diameters of the enveloping ring are 100 mm and 300 mm respectively.

[0029] The bias magnetic field coil group 5 is composed of 4 coils arranged coaxially and in parallel, all of which are made of enameled copper wire wound on a coil frame. By adjusting the number of turns and current, an axial magnetic field with an intensity of 10-100Gs is generated at the central axis of the pre-ionization chamber 2. By adjusting the coil diameter, position, number of turns and other parameters, the magnetic field distribution is parallel to the axial direction in the pre-ionization chamber 2, parallel to the surface of the induction coil in the acceleration stage chamber 3, and smoothly transitions at the connection position of the two chambers, such as Figure 3 shown.

[0030] The gas distributor 6 is a "T" shaped structure, with an upstream hollow cylinder with an outer diameter of 14mm and an inner diameter of 8mm, and a downstream truncated cone with a diameter of 20mm. The side of the truncated cone is provided with 8 circular holes with a diameter of 2mm evenly distributed along the circumference, and these circular holes are connected to the central circular hole upstream of the gas distributor 6. The gaseous medium enters from the upstream of the gas distributor, and enters the pre-ionization chamber 2 more evenly after being distributed by the lateral circular holes downstream.

[0031] The working principle of the magnetic field assisted RF pre-ionization induction pulse plasma thruster is as follows: when the thruster is working, the gaseous working fluids such as xenon, nitrogen, carbon dioxide, etc. enter the pre-ionization chamber 2 from the gas distributor 6 and diffuse forward. Under the action of the RF voltage of 50W / 13.56MHz, the RF pre-ionization coil 1 excites a rapidly changing electromagnetic field in the space inside the pre-ionization chamber 2, and then pre-ionizes the gaseous working fluid in the form of inductive coupling discharge, generating a large number of electrons and ions, and the ionization degree of the gaseous working fluid reaches more than 1%. The gaseous working fluid containing the initial electrons moves along the direction of the magnetic flux under the guidance of the magnetic field generated by the bias magnetic field coil group 5, and diffuses to the surface of the induction acceleration coil 4 inside the acceleration stage chamber 3. Then, the energy storage capacitor with a capacitance of 10μF discharges to the induction acceleration coil 4 through a fast closing switch, thereby inducing a pulsed radial magnetic field of thousands of Gauss and an angular electric field of several millivolts per meter, which promotes the further ionization of the gaseous working fluid and forms a ring plasma current sheet. The angular plasma current is accelerated by the axial Lorentz force in the radial magnetic field and ejected at a speed of tens of kilometers per second. At a repetitive operating frequency of several thousand hertz, it can generate a thrust of tens to hundreds of millinewtons.

[0032] It should be understood that the above content is a further detailed description of the present invention in combination with a specific preferred embodiment, and it cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, they can also make several simple deductions or substitutions, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims

1. A magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster, characterized in that: include: Radio frequency pre-ionization coil, pre-ionization chamber, accelerating stage chamber, induction acceleration coil, bias magnetic field coil assembly and gas distributor; The preionization chamber is connected to the acceleration chamber, the radio frequency preionization coil is arranged outside the preionization chamber and coaxial with the preionization chamber, the induction acceleration coil is arranged inside the acceleration chamber, the bias magnetic field coil group is arranged outside the preionization chamber and the induction acceleration coil and coaxial with the two, and the gas distributor is installed at the upstream central axis of the preionization chamber; The bias magnetic field coil group is composed of a plurality of coils arranged coaxially and in parallel, and is wound on a coil frame with enameled copper wire. By adjusting the number of turns and the current, an axial magnetic field with adjustable strength is generated at the central axis of the pre-ionization chamber; by adjusting the coil diameter, position and number of turns, the magnetic field distribution is parallel to the axial direction in the pre-ionization chamber, parallel to the surface of the induction coil in the acceleration stage chamber, and smoothly transitions at the position where the two chambers are connected; The gas distributor is a "T"-shaped structure, with a cylindrical hole in the center of the upstream, a truncated cone in the downstream, and several circular holes evenly distributed along the circumference on the side, which are connected to the central circular hole upstream of the gas distributor; the gas working medium enters from the upstream of the gas distributor, is distributed through the lateral circular holes downstream, and evenly enters the pre-ionization chamber.

2. The magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 1, characterized in that: The radio frequency pre-ionization coil is a copper tube wound into a multi-turn coaxial spiral structure, which is installed outside the pre-ionization chamber; the coil diameter, number of turns and turn spacing are variable and are selected according to actual needs; the copper tube is a hollow structure, and the inner diameter and outer diameter are selected according to actual needs, and the outer diameter is always larger than the inner diameter; the copper tube can be connected to a water cooling device.

3. A magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 1 or 2, characterized in that: The pre-ionization chamber is made of high temperature resistant insulating material such as quartz glass or alumina ceramics, and is cylindrical as a whole. Its outer diameter is smaller than that of the radio frequency pre-ionization coil, its length is greater than that of the radio frequency pre-ionization coil, and its thickness is selected according to actual needs.

4. The magnetic field-assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 3, characterized in that: The aspect ratio of the pre-ionization cavity is greater than 1, and the thickness is between 2 and 10 mm. A circular hole is opened at the upstream axis of the pre-ionization cavity for installing a gas distributor, and the downstream is connected to the acceleration stage cavity.

5. A magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 1 or 4, characterized in that: The accelerating stage cavity is made of high temperature resistant insulating material such as quartz glass or alumina ceramics. The main body is a planar annular structure. The inner edge is connected to the downstream of the pre-ionization cavity, and the outer edge is provided with a enclosure structure with a height of several centimeters to adjust the distribution of the gas working medium on the surface of the induction acceleration coil. The pre-ionization cavity and the accelerating stage cavity form a "T" shape as a whole, and the connecting part of the two adopts a smooth transition structure.

6. A magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 1 or 5, characterized in that: The induction acceleration coil is a planar ring, arranged inside the acceleration stage cavity, and adopts a basic structure of double layers and m spiral wires in parallel. The upper and lower coils are arranged alternately and isolated by insulating materials with a thickness of several millimeters to ensure that the induced electromagnetic field is evenly distributed over the entire coil surface.

7. The magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 6, characterized in that: Each spiral is made of enameled copper wire and has an Archimedean spiral structure. It expands from the inner diameter to the outer diameter of the enveloping ring and rotates 360° in total. The rotation angle between two adjacent spirals differs by n° and satisfies m×n=360. The inner diameter and outer diameter of the enveloping ring are selected according to actual needs.

8. A method for implementing the working of the magnetic field assisted radio frequency pre-ionization induction pulse plasma thruster according to claim 1, characterized in that: When the thruster is working, the gas working fluid enters the pre-ionization cavity from the gas distributor and diffuses forward; under the action of a certain power of radio frequency voltage, the radio frequency pre-ionization coil excites a rapidly changing electromagnetic field in the space inside the pre-ionization cavity, and then pre-ionizes the gas working fluid in the form of inductive coupling discharge, and generates an initial plasma of a certain density; the gas working fluid containing initial electrons moves along the direction of the magnetic flux lines under the guidance of the bias magnetic field, and diffuses to the surface of the induction acceleration coil inside the acceleration stage cavity; then, the external energy storage capacitor discharges to the induction acceleration coil through a fast closing switch, and then induces a high-intensity, pulsed angular electric field and radial magnetic field, which promotes further ionization of the gas working fluid and forms a ring-shaped plasma current sheet; the angular plasma current is accelerated and ejected by the axial Lorentz force in the radial magnetic field and generates thrust.

Images