Field emission self-neutralization grid acceleration device and control method for ion thruster

Abstract

The present invention discloses a field emission self-neutralization grid acceleration device and control method for an ion thruster. The acceleration device comprises a screen grid, an acceleration grid, an insulating pad and a neutralization discharge needle. The acceleration grid is arranged at intervals downstream of the screen grid, the insulating pad is arranged on the downstream end face of the acceleration grid, the neutralization discharge needle is arranged vertically on the downstream end face of the insulating pad, the screen grid is provided with a first circular through hole, the acceleration grid is provided with a second circular through hole corresponding to the first circular through hole, the insulating pad is provided with a third circular through hole consistent with the first circular through hole, and the neutralization discharge needle is located at the midpoint of the line connecting the centers of two adjacent third circular through holes. A positive voltage is applied to the screen grid, a negative voltage is applied to the acceleration grid, and a pulsed negative voltage is applied to the neutralization discharge needle, and the negative voltage is lower than the voltage of the acceleration grid to achieve normal operation of the acceleration device. The present invention has fewer components, a lighter thruster mass, a more uniform neutralized electron beam, less plume pollution, better specific impulse performance, and simpler theoretical research and development and simulation models.

Description

Technical Field

[0001] The invention relates to an electrostatic ion thruster used in orbit transfer and deep space exploration, and in particular to a field emission self-neutralization grid acceleration device and a control method for the electrostatic ion thruster. Background Art

[0002] Every breakthrough in the aerospace industry depends on the development of propulsion technology, and electric thrusters are gradually favored by the aerospace industry due to their advantages such as high specific impulse, long life, compact structure, small size and low pollution. At present, electrostatic ion thrusters are one of the most mature ion electric propulsion technologies, with better specific impulse performance and more suitable for deep space exploration missions.

[0003] The electrostatic ion thruster mainly consists of three parts: the ionization chamber, the grid acceleration system and the neutralizing electron gun. The propellant enters the ionization chamber and ionizes to form plasma. The grid acceleration system extracts positive ions from the plasma and accelerates the ion beam to generate thrust. The neutralizing electron gun emits electrons of equal charge to the ion beam to neutralize the ion beam and maintain the electrical neutrality of the thruster.

[0004] On the one hand, the traditional neutralization electron gun not only increases the package size of the thruster, but also limits the service life of the electrostatic ion thruster.

[0005] On the other hand, the prior art uses radio frequency or alternating voltage applied to the acceleration grid, accelerating anions or electrons in the positive potential period of the radio frequency or alternating voltage, and accelerating cations in the negative potential period, thereby maintaining the electrical neutrality of the thruster. For example, there are currently two types of electric propulsion devices that can achieve self-neutralization, namely "ion-ion thruster" and "self-neutralizing radio frequency ion thruster". Among them, the self-neutralization working principles of the two are the same, both of which apply alternating voltage to the acceleration grid, draw out negative ions or electrons in the positive voltage half cycle of the alternating voltage, and draw out positive ions in the negative voltage half cycle of the alternating voltage, and then achieve electrical neutrality by satisfying that the number of positive and negative ions drawn out in one cycle is equal. It can be seen from this that the self-neutralization of the above two does not discharge positive and negative ions or positive ions and electrons at the same time, because the cycle of the alternating voltage is very short, it can be considered to be simultaneous, but strictly speaking it is not.

[0006] Furthermore, since the "ion-ion thruster" and "self-neutralizing RF ion thruster" accelerate ions and electrons under alternating voltage, the coupling relationship between alternating voltage and plasma potential and the acceleration of plasma extraction are extremely complex and difficult to explain. In the process of research and development, the "Poisson equation" and "Helmholtz equation" need to be solved, which is not conducive to research and development and design work. In addition, the control of RF power supply also requires corresponding technical research.

[0007] However, this technology not only increases the thruster's requirements for the power system and control technology, but also increases the difficulty of the theoretical research and development model. Summary of the invention

[0008] In order to solve the above problems, the present invention aims to provide a field emission self-neutralization grid acceleration device and control method for ion thrusters, which can reduce thruster components and reduce thruster mass, and make the neutralized electron beam more uniform, with less plume pollution, better specific impulse performance, and simpler theoretical research and development and simulation models.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A field emission self-neutralization grid acceleration device for an ion thruster, comprising:

[0011] A screen grid is connected to the ionization chamber to lead out positive ions in the plasma, and a plurality of first circular through holes are formed on the screen grid;

[0012] An acceleration grid, the acceleration grid is located downstream of the screen grid, accelerates the positive ions drawn out of the screen grid and generates thrust, a plurality of second circular through holes corresponding to the first circular through holes are opened on the acceleration grid, the aperture of the second circular through holes is smaller than the aperture of the first circular through holes, there is a spacing distance between the acceleration grid and the screen grid, and the spacing distance is smaller than the aperture of the first circular through hole;

[0013] An insulating pad, the insulating pad is arranged on the downstream end surface of the acceleration grid, and a plurality of third circular through holes are opened on the insulating pad, the third circular through holes correspond to the first circular through holes one by one and have the same aperture;

[0014] The first circular through hole, the second circular through hole and the third circular through hole are coaxial;

[0015] A neutralization discharge needle, wherein a plurality of the neutralization discharge needles are vertically arranged on the downstream end surface of the insulating pad, the neutralization discharge needle is located at the midpoint of the line connecting the centers of two adjacent third circular through holes, the neutralization discharge needle is a conical structure, the needle tip curvature radius of the neutralization discharge needle is smaller than the radius of the second circular through hole, and the neutralization discharge needle releases an electron beam through the field emission effect to neutralize the ion beam to achieve the electrical neutrality balance of the ion thruster.

[0016] As a solution, the thickness of the insulating pad is smaller than the thickness of the screen grid, and the thickness of the screen grid is smaller than the thickness of the acceleration grid.

[0017] As a solution, the screen grid, the acceleration grid and the insulating pad are all in the shape of round cakes.

[0018] As a solution, the first circular through hole, the second circular through hole and the third circular through hole are all distributed in a hexagonal array, including 7 hole positions distributed at the six vertices and the center position of the regular hexagon.

[0019] As a solution, the aperture of the first circular through hole on the screen grid is 1.8-2 mm, and the thickness of the screen grid is 0.3-0.5 mm;

[0020] The aperture of the second circular through hole on the acceleration grid is 1.2-1.5 mm, and the thickness of the acceleration grid is 0.7-1 mm;

[0021] The diameter of the third circular through hole on the insulating pad is 1.8-2 mm, and the thickness of the insulating pad is 0.05-0.1 mm.

[0022] As a solution, the spacing distance between the acceleration grid and the screen grid is 1 to 1.2 mm.

[0023] As a solution, the tip curvature radius of the neutralization discharge needle is greater than 0.1 times the radius of the second circular through hole.

[0024] The control method of the field emission self-neutralization grid acceleration device for ion thrusters mentioned above comprises:

[0025] Adopt DC power supply;

[0026] Apply a positive voltage to the screen grid;

[0027] Apply a negative voltage to the acceleration grid, and the voltage value is much smaller than the voltage value on the screen grid;

[0028] A pulse negative voltage is applied to the neutralization discharge needle, and the negative voltage is lower than the acceleration gate voltage.

[0029] As a solution, the positive voltage applied to the screen grid is more than 1000V, and the negative voltage applied to the acceleration grid is -100V.

[0030] Furthermore, when the ionization chamber is in a high-power working mode, the pulse negative voltage is adjusted to a lower voltage to enhance the needle tip electric field strength and the neutralization electron beam current density of the neutralization discharge needle.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) Fewer components and lighter thruster mass. The integrated design of the neutralizer and the accelerator grid reduces the number of components and eliminates the supporting circuits and connection systems, thereby reducing mass.

[0033] (2) The neutralization electron beam is more uniform and the plume pollution is smaller. The neutralization discharge needles are evenly distributed around the accelerating grid hole on the downstream surface of the accelerating grid. The electron beam emitted is more uniform than the traditional neutralization electron gun, which is conducive to the neutralization of ions and electrons.

[0034] (3) Better specific impulse performance. Because the charge-to-mass ratio of electrons is much greater than that of ions, the electrons released by the neutralizing discharge needle will be ahead of the movement of ions and concentrate downstream of the ions, forming a virtual cathode downstream of the ions, which in turn delays the deceleration trend of the ion beam moving toward the zero potential in space, thereby improving the specific impulse performance. (4) Simpler theoretical research and simulation models. When simulating numerical analysis, the present invention only needs to solve the Poisson equation for the distribution of the electrostatic field; while the model that uses radio frequency or alternating potential to achieve self-neutralization requires solving the Poisson equation and the Helmholtz equation for the complex electromagnetic field distribution, and the difficulty of solving and the boundary conditions are more complex. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a front view of the field emission self-neutralization grid acceleration system of the present invention;

[0036] Figure 2 A side view of the field emission self-neutralization grid acceleration system of the present invention;

[0037] Figure 3 A three-dimensional diagram of the field emission self-neutralization grid acceleration system of the present invention;

[0038] Figure 4 A detailed diagram of the field emission self-neutralization grid acceleration system of the present invention;

[0039] Figure 5 It is a working principle diagram of the present invention;

[0040] In the figure, 1-screen grid; 2-acceleration grid; 3-insulation pad; 4-neutralization discharge needle. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0042] like Figure 1 to Figure 4 As shown, the field emission self-neutralization grid acceleration device for the electrostatic ion thruster in this embodiment specifically includes: a screen grid 1, an acceleration grid 2, an insulating pad 3 and a neutralization discharge needle 4.

[0043] The screen grid 1 is located at the front end of the grid acceleration system, and is connected to the ionization chamber when working to absorb the cations in the plasma; the acceleration grid 2 is located downstream of the screen grid 1, and accelerates the cations absorbed by the screen grid 1 and generates thrust; the insulating pad 3 is installed on the downstream surface of the acceleration grid 2 to prevent the neutralization discharge needle 4 and the acceleration grid 2 from generating a large current and causing invalid power consumption; the neutralization discharge needle 4 is installed on the downstream surface of the insulating pad 3, and a negative potential is applied to release an electron beam through the field emission effect to neutralize the ion beam to achieve the electrical neutrality balance of the thruster.

[0044] The screen grid 1 is in the shape of a round cake and is processed with round through holes, which are distributed in a regular hexagon. The aperture of the screen grid 1 is about 1.8-2 mm, and the thickness of the screen grid 1 is about 0.3-0.5 mm.

[0045] The acceleration grid 2 is also in the shape of a round pancake and has circular through holes corresponding to the holes of the screen grid 1. The diameter of the acceleration grid 2 is about 1.2-1.5 mm, and the thickness of the acceleration grid 2 is about 0.7-1 mm. The distance between the acceleration grid 2 and the screen grid 1 should be smaller than the diameter of the screen grid 1, about 1-1.2 mm.

[0046] The insulating pad 3 has the same structure and aperture as the screen grid 1, but is thinner, about 0.05 to 0.1 mm.

[0047] The neutralization discharge needle 4 is installed at the midpoint of the line connecting the centers of the holes of two adjacent accelerating grids 2, and its structure is a cone. The curvature radius of the tip of the neutralization discharge needle 4 should be slightly larger than 0.1 times the radius of the accelerating grid 2 hole.

[0048] like Figure 5 As shown, a positive voltage of more than kV is applied to the screen grid 1; a negative voltage of -100V is applied to the acceleration grid 2; and a pulsed negative voltage is applied to the neutralization discharge needle 4, and the negative voltage is lower than the voltage of the acceleration grid 2. When the ionization chamber is in high-power working mode, that is, when the ion beam current density increases, the pulsed negative voltage is adjusted to a lower voltage to enhance the needle tip electric field strength of the neutralization discharge needle 4 and the neutralization electron beam current density.

[0049] In the present invention, the field emission effect of the neutralizing discharge needle 4 is used to emit an electron beam to the ion beam to achieve self-neutralization, and the power supply used is direct current. In contrast, while the gate acceleration device of the present invention extracts positive ions, the neutralizing discharge needle 4 releases electrons to neutralize the plume. Therefore, the present invention is a strict sense of simultaneously emitting released ions and electrons. The physical model of the present invention is similar to the traditional gate acceleration system model, and only the Poisson equation needs to be solved, and the control system requirements are relatively low.

[0050] Traditional ion-ion thrusters and self-neutralizing RF ion thrusters use alternating voltage to accelerate positive and negative ions respectively. Because the voltage is constantly changing, the speed of the ions is determined by the effective value (mean value) of the alternating voltage. In order to avoid the gate acceleration device being electrically broken down, it is assumed that the alternating voltage is a sinusoidal function, and its peak voltage value is the breakdown voltage V between the gates. bd Therefore, the thrust and specific impulse of the two thrusters are limited by the breakdown voltage V bd of

[0051] In contrast, the thrust and specific impulse of the present invention are limited by the breakdown voltage V when the DC voltage is used to accelerate ions. bd According to the relationship between speed u and acceleration voltage V (where e represents the charge and m represents the ion mass) It can be seen that the speeds of the ion-ion thruster and the self-neutralizing RF ion thruster are The speed of the present invention It can be seen that new >u i-i It can be seen that the speed of the present invention is significantly better than the traditional self-neutralization scheme.

Claims

1. A field emission self-neutralization grid accelerator for an ion thruster, characterized in that: include, A screen grid (1), the screen grid (1) being connected to the ionization chamber and leading out positive ions in the plasma, and a plurality of first circular through holes being formed on the screen grid (1); an accelerating grid (2), the accelerating grid (2) being located downstream of the screen grid (1) and accelerating the positive ions drawn out by the screen grid (1) and generating thrust, the accelerating grid (2) being provided with a plurality of second circular through holes corresponding one to one with the first circular through holes, the apertures of the second circular through holes being smaller than the apertures of the first circular through holes, and a spacing distance being provided between the accelerating grid (2) and the screen grid (1), and the spacing distance being smaller than the aperture of the first circular through holes; An insulating pad (3), the insulating pad (3) being arranged on the downstream end surface of the accelerating grid (2), the insulating pad (3) being provided with a plurality of third circular through holes, the third circular through holes corresponding to the first circular through holes one by one and having the same aperture; The first circular through hole, the second circular through hole and the third circular through hole are coaxial; A neutralization discharge needle (4), wherein a plurality of the neutralization discharge needles (4) are vertically arranged on the downstream end surface of the insulating pad (3), the neutralization discharge needle (4) is located at the midpoint of a line connecting the centers of two adjacent third circular through holes, the neutralization discharge needle (4) is a cone structure, the needle tip curvature radius of the neutralization discharge needle (4) is smaller than the radius of the second circular through hole, and the neutralization discharge needle (4) releases an electron beam through a field emission effect to neutralize an ion beam so as to achieve electrical neutrality balance of the ion thruster.

2. A field emission self-neutralization grid acceleration device for an ion thruster according to claim 1, characterized in that: The thickness of the insulating pad (3) is smaller than the thickness of the screen grid (1), and the thickness of the screen grid (1) is smaller than the thickness of the acceleration grid (2).

3. A field emission self-neutralization grid acceleration device for an ion thruster according to claim 1, characterized in that: The screen grid (1), the accelerating grid (2) and the insulating pad (3) are all in the shape of round cakes.

4. A field emission self-neutralization grid acceleration device for an ion thruster according to claim 1, characterized in that: The first circular through hole, the second circular through hole and the third circular through hole are all distributed in a hexagonal array, including 7 hole positions distributed at the six vertices and the center position of the regular hexagon.

5. The field emission self-neutralization grid acceleration device for ion thrusters according to claim 1, characterized in that: The aperture of the first circular through hole on the screen grid (1) is 1.8 to 2 mm, and the thickness of the screen grid (1) is 0.3 to 0.5 mm; The aperture of the second circular through hole on the acceleration grid (2) is 1.2 to 1.5 mm, and the thickness of the acceleration grid (2) is 0.7 to 1 mm; The diameter of the third circular through hole on the insulating pad (3) is 1.8 to 2 mm, and the thickness of the insulating pad (3) is 0.05 to 0.1 mm.

6. A field emission self-neutralization grid acceleration device for an ion thruster according to claim 1, characterized in that: The spacing distance between the acceleration grid (2) and the screen grid (1) is 1 to 1.2 mm.

7. The field emission self-neutralization grid acceleration device for ion thrusters according to claim 1, characterized in that: The needle tip curvature radius of the neutralization discharge needle (4) is greater than 0.1 times the radius of the second circular through hole.

8. The control method of the field emission self-neutralization grid acceleration device for ion thrusters according to claim 1 is characterized in that: include, Adopt DC power supply; Applying a positive voltage to the screen grid (1); Applying a negative voltage to the acceleration grid (2), wherein the voltage value is much smaller than the voltage value on the screen grid (1); A pulse negative voltage is applied to the neutralization discharge needle (4), and the negative voltage is lower than the voltage of the acceleration grid (2).

9. The control method according to claim 8, characterized in that: The positive voltage applied to the screen grid (1) is above 1000V, and the negative voltage applied to the acceleration grid (2) is -100V.

10. The control method according to claim 8, characterized in that: When the ionization chamber is in a high-power working mode, the pulse negative voltage is adjusted to a lower voltage to enhance the needle tip electric field intensity and the neutralization electron beam current density of the neutralization discharge needle (4).

Images