Voltage generation device

Abstract

To provide a voltage generation device capable of achieving miniaturization of a power processing unit that supplies power to a Hall thruster.SOLUTION: This voltage generation device is provided in a Hall thruster system that generates thrust of a spacecraft. In the voltage generation device, a first end is connected to a first line on an anode electrode side in an anode power source for supplying power between an anode electrode and a cathode electrode that are included in a Hall thruster constituting the Hall thruster system, and a second end for outputting an output voltage corresponding to an input voltage at the first end is connected to a keeper electrode disposed close to a hollow cathode connected to the cathode electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a voltage generating device.

Background Art

[0002] The use of electric thrusters for generating thrust to control the orbits and attitudes of spacecraft such as artificial satellites has been expanding, and the market is growing rapidly. Since electric thrusters can reduce the amount of propellant gas mounted on spacecraft compared to chemical thrusters, their adoption is increasing not only for artificial satellites and geostationary satellites for deep space exploration but also for constellation satellites operating in low orbits. In recent years, the use of systems using Hall thrusters in particular has been rapidly progressing. This is due to the merit that Hall thruster systems have a high thrust generated per unit of power.

[0003] A Hall thruster generates thrust, for example, by accelerating ions extracted from plasma generated by ionizing a predetermined gas such as xenon and ejecting them into outer space. In a Hall thruster system, a discharge is caused in the Hall thruster by the power supplied from a power processing unit (PPU: Power Processing Unit), and ions are extracted from the plasma generated by this discharge. Here, the power processing unit is composed of, for example, a plurality of power supplies such as an anode power supply, a keeper power supply, a heater power supply, and a coil power supply, and a power control unit. This power processing unit occupies a large proportion of the weight and cost in the Hall thruster system. Therefore, reducing the cost and size of the power processing unit is a very important item for realizing a Hall thruster system.

[0004] In this regard, conventionally, technologies related to miniaturization and cost reduction of power processing units have been proposed. As one of the proposals, there is a technology for miniaturizing the anode power supply that accounts for most of the power supplied to the Hall thruster among the multiple power supplies that make up the power processing unit. As a technology for miniaturizing the anode power supply, for example, a technology for miniaturization by adopting a resonant converter as the anode power supply (for example, Patent Document 1), or a technology for suppressing the discharge instability peculiar to the Hall thruster by varying the output voltage of the anode power supply at a high frequency and achieving miniaturization of the filter provided in the anode power supply (for example, Patent Document 2) have been proposed. As another proposal, among the multiple power supplies that make up the power processing unit, a technology has been proposed to eliminate (delete) the heater power supply of the hollow cathode provided in the Hall thruster and start the discharge in the hollow cathode by applying a high-voltage pulse generated by the keeper power supply (for example, Patent Document 3). In this conventional technology, the electron-emitting material is not heated by the heater power supply, but a high-voltage pulse generated by the keeper power supply strongly extracts electrons from the hollow cathode, generating discharge and plasma between the hollow cathode and the keeper electrode.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the prior art where the size and cost of the power processing unit are reduced by miniaturizing the anode power supply, in order to miniaturize the anode power supply, which is an essential power supply for accelerating and injecting gas in the Hall thruster, for example, it is necessary to improve the power density of the anode power supply, and thus another problem may arise in ensuring the performance of the Hall thruster system. On the other hand, in the prior art where the size and cost of the power processing unit are reduced by eliminating the heater power supply, for example, it is necessary to suppress the material loss of the keeper electrode (or the end portion on the keeper electrode side of the hollow cathode) due to the arc of the high-voltage pulse generated by the keeper power supply and the decrease in insulation between the electrodes due to the material loss. Therefore, in the prior art, it may be difficult to miniaturize and reduce the cost of the power processing unit when considering the mission to be performed by the spacecraft.

[0007] The present invention has been made based on the above recognition of the problems, and an object thereof is to provide a voltage generation device capable of realizing miniaturization of a power processing unit that supplies power to a Hall thruster.

Means for Solving the Problems

[0008] To achieve the above object, a voltage generation device according to an aspect of the present invention is a voltage generation device provided in a Hall thruster system that generates the propulsive force of a spacecraft, and a first end is connected to a first line on the anode electrode side in an anode power supply that supplies power between an anode electrode and a cathode electrode of a Hall thruster constituting the Hall thruster system, and a second end that outputs an output voltage corresponding to the input voltage of the first end is connected to a keeper electrode disposed close to a hollow cathode connected to the cathode electrode.

Effects of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a voltage generator capable of realizing miniaturization of a power processing unit that supplies power to a Hall thruster.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the voltage generator of the present invention will be described with reference to the drawings. The voltage generator of the present invention is applied to a Hall thruster system including a Hall thruster. The Hall thruster is an electric thruster that generates a propulsive force for controlling the orbit or attitude of a spacecraft when moving in space by accelerating ions drawn from plasma generated by ionizing a predetermined gas (propulsion gas) such as xenon and ejecting them into space. The propulsion gas may be, for example, a gas such as krypton, argon, nitrogen, oxygen, vaporized iodine, or water.

[0012] A spacecraft equipped with a Hall thruster system may be an artificial satellite that orbits along a predetermined orbit while orbiting above the Earth's surface, above the surface of other celestial bodies or objects, or it may be an observation satellite that goes out to observe other celestial bodies or objects (and may also return to the Earth). Other celestial bodies include other planets different from the Earth such as Mars and Venus, satellites such as the Moon and Titan, and asteroids such as Itokawa and Ryugu. Other objects include rocks and the like.

[0013] [Configuration of Hall Thruster System] FIG. 1 is a diagram showing an example of the configuration of a Hall thruster system including a power processing unit having a voltage generation device according to an embodiment. The Hall thruster system 1 includes, for example, a Hall thruster 10 and a power processing unit (PPU: Power Processing Unit) 20. FIG. 1(a) shows an example when viewed from the side where the Hall thruster 10 ejects ions extracted from plasma into space. FIG. 1(b) shows an example of a cross-sectional view of the A-A' cross-section of the Hall thruster 10 shown in FIG. 1(a) and an example of the connection between the Hall thruster 10 and the power processing unit 20. FIG. 1(c) shows an example of the configuration of the Hall thruster system 1 with the range of region B of the Hall thruster 10 shown in FIGS. 1(a) and 1(b) enlarged.

[0014] First, the structure of the Hall thruster 10 will be described with reference to FIGS. 1(a) and 1(b). In the Hall thruster 10, a hollow cathode portion 15 is disposed at the center of a cylindrical housing, and an internal electromagnet 14a, a channel portion 11, and an external electromagnet 14b are annularly arranged in this order from the center toward the outer peripheral portion. In the following description, when the internal electromagnet 14a and the external electromagnet 14b are not distinguished from each other, they are simply referred to as "electromagnet 14". In the Hall thruster 10, the channel portion 11 is formed as a groove along the electromagnet 14, and the periphery of the groove is surrounded by a wall portion 13 made of, for example, ceramic or the like. And an anode 12 is disposed at the bottom of the groove forming the channel portion 11.

[0015] Next, with reference to Fig. 1(c), a more detailed configuration of the Hall thruster 10 and the power processing unit 20, and the connection between the Hall thruster 10 and the power processing unit 20 will be described. As described above, the Hall thruster 10 includes, for example, a channel portion 11, an anode 12, a wall portion 13, an electromagnet 14, and a hollow cathode portion 15. The hollow cathode portion 15 includes, for example, a hollow cathode body 15a, a keeper electrode body 15b, a heater 15c, and a gas supply pipe 15d. The power processing unit 20 includes, for example, an anode power supply 30, an igniter unit 40, a heater power supply 50, a coil power supply 60, and a power control unit 100. The power processing unit 20 has a configuration in which the keeper power supply included in the power processing unit in the conventional Hall thruster system is eliminated (deleted), and instead, an igniter unit 40 is provided.

[0016] Each of the anode power supply 30, the heater power supply 50, and the coil power supply 60 is a DC power supply that supplies the power required for the corresponding components included in the Hall thruster 10. More specifically, the anode power supply 30 is a switching power supply that supplies, for example, power with a maximum voltage value of 300 [V] and a current value of 3 [A] or power with a maximum voltage value of 300 [V] and a current value of 20 [A] to the anode 12 in accordance with the control from the power control unit 100. When the anode power supply 30 supplies power with a maximum voltage value = 300 [V] and a current value = 3 [A] to the anode 12, a Hall thruster 10 of the order of 1 [kW] is configured. When the anode power supply 30 supplies power with a maximum voltage value = 300 [V] and a current value = 20 [A] to the anode 12, a Hall thruster 10 of the order of 6 [kW] is configured. The power supplied by the anode power supply 30 is not limited to a maximum voltage value = 300 [V]. The anode power supply 30 may supply power with a maximum voltage value of 150 [V] or 1000 [V], etc., according to the performance of the Hall thruster 10, for example.

[0017] The heater power supply 50 is a DC power supply that supplies power to the heater 15c, such as power with a voltage value of 100 [V] and a current value of 1 [A], power with a voltage value of 10 [V] and a current value of 10 [A], or power with a voltage value of 20 [V] and a current value of 5 [A], in accordance with the control from the power control unit 100. In Fig. 1(c), a configuration is shown in which the negative electrode side of the heater power supply 50 is connected to the negative electrode side of the anode power supply 30 (connected to the cathode electrode Ec connected to the hollow cathode body 15a), but the negative electrode side of the heater power supply 50 may be configured to be connected to a dedicated electrode provided in the hall thruster 10, for example. The heater power supply 50 may be omitted when a high voltage pulse is applied to the keeper electrode body 15b by the igniter unit 40 described later, for example.

[0018] The coil power supply 60 is a DC power supply that supplies power to the electromagnets 14, that is, the internal electromagnet 14a and the external electromagnet 14b, such as power with a voltage value of 100 [V] and a current value of 1 [A], power with a voltage value of 10 [V] and a current value of 10 [A], or power with a voltage value of 20 [V] and a current value of 5 [A], in accordance with the control from the power control unit 100.

[0019] The heater power supply 50 and the coil power supply 60 may be DC power supplies with a fixed voltage value or a fixed current value whose power output is controlled to be on or off in accordance with the control from the power control unit 100. The heater power supply 50 and the coil power supply 60 may also be switching power supplies whose supplied voltage value and current value are controlled in accordance with the control from the power control unit 100.

[0020] The igniter unit 40 is a component that applies a voltage to the keeper electrode body 15b, replacing the keeper power supply provided in the conventional power processing unit. Therefore, similar to the conventional keeper power supply, the igniter unit 40 functions as a power supply circuit that performs a voltage application operation and a current supply operation. The voltage application operation is an operation of outputting (applying) a high voltage, for example, with a no-load voltage value of 100 to 300 [V], to cause a discharge between the hollow cathode body 15a and the keeper electrode body 15b. The current supply operation is an operation of flowing a current, for example, with a current value of 0.something to several [A], to maintain the discharge state between the hollow cathode body 15a and the keeper electrode body 15b from after a discharge occurs between the hollow cathode body 15a and the keeper electrode body 15b due to the voltage application operation until a discharge starts between at least the anode 12 and the hollow cathode body 15a and the extraction of ions ionized from the plasma begins. The igniter unit 40 generates a voltage to be applied to the keeper electrode body 15b based on the voltage applied by the anode power supply 30 to the anode 12. The igniter unit 40 has a first end a connected to the line La on the positive electrode side of the anode power supply 30, and a second end b connected to the keeper electrode body 15b (more specifically, the keeper electrode Ek disposed in the hollow thruster 10 and connected to the keeper electrode body 15b). The igniter unit 40 generates an output voltage with a magnitude (voltage value) corresponding to the input voltage at the first end a, that is, the voltage value of the voltage applied by the anode power supply 30 from the positive electrode side, and outputs it from the second end b. The conventional keeper power supply was a switching power supply configured by combining a large number of semiconductor components and passive elements (coil elements, resistance elements, capacitor elements) to perform a voltage application operation and a current supply operation by voltage conversion (boosting) of the voltage of the system power supply in a spacecraft, for example. In contrast, the igniter unit 40 is composed of only passive elements such as resistance elements and capacitor elements, for example.

[0021] The igniter unit 40 is an example of a "voltage generating device". The line La is an example of a "first line".

[0022] The power control unit 100 controls the power (applied voltage or flowing current) supplied from each of the anode power supply 30, heater power supply 50, and coil power supply 60 provided in the power processing unit 20 to the corresponding components provided in the Hall thruster 10. For example, the power control unit 100 controls so that the time during which the voltage value of the voltage applied from the anode power supply 30 to the anode 12 changes from 0 [V] to 300 [V], that is, the so-called voltage rise time becomes a predetermined time. For example, the power control unit 100 switches between on (for example, a state where the voltage value is 100 [V]) and off (for example, a state where the voltage value is 0 [V]) of the voltage applied from the heater power supply 50 to the heater 15c and the voltage applied from the coil power supply 60 to the coil constituting the electromagnet 14.

[0023] The hollow cathode body 15a supplies electrons for starting the operation of the Hall thruster 10 by ionizing the propellant gas supplied into the channel portion 11 and extracting ions, and during the operation of the Hall thruster 10, it is an electron source that emits electrons for electrically neutralizing the plasma and the accelerated ions. The same propellant gas as that supplied to the anode 12 is supplied to the hollow cathode body 15a from the gas supply pipe 15d. The hollow cathode body 15a ionizes the propellant gas supplied by the gas supply pipe 15d and emits the generated electrons toward the channel portion 11 side. The negative side of the anode power supply 30 is connected to the cathode electrode Ec connected to the hollow cathode body 15a. In FIGS. 1(b) and 1(c), an example is shown in which the cathode electrode Ec is disposed on the side of the housing of the Hall thruster 10 opposite to the side where the ions extracted from the plasma are ejected into space, but the hollow cathode body 15a itself (which may be the portion of the gas supply pipe 15d) may serve as the cathode electrode Ec. The keeper electrode body 15b is disposed in proximity to the tip of the hollow cathode body 15a. However, the hollow cathode body 15a and the keeper electrode body 15b are insulated from each other. Further, the outer periphery of the hollow cathode body 15a is covered by the heater 15c. The positive side of the heater power supply 50 is connected to the heater electrode Eh connected to the heater 15c. That is, the heater power supply 50 is connected between the heater 15c (heater electrode Eh) and the hollow cathode body 15a (cathode electrode Ec). The heater 15c generates heat according to the electric power supplied by the heater power supply 50, thereby heating components called emitters and electron emission materials (not shown) provided in the hollow cathode body 15a so that more electrons are emitted from the hollow cathode body 15a. The keeper electrode body 15b is supplied with the electric power generated by the igniter unit 40 connected to the keeper electrode Ek. When a high voltage is applied to the keeper electrode body 15b by the electric power supplied by the igniter unit 40, a discharge occurs between the hollow cathode body 15a and the keeper electrode body 15b, and due to this discharge, the propellant gas supplied from the gas supply pipe 15d into the hollow cathode body 15a is ionized to generate plasma.Electrons drawn from the plasma due to the potential gradient between the hollow cathode body 15a and the keeper electrode body 15b are emitted toward the channel portion 11 side. In the following description, the discharge between the hollow cathode body 15a and the keeper electrode body 15b is also referred to as "keeper ignition", and the plasma generated by this discharge (keeper ignition) is also referred to as "cathode plasma".

[0024] The anode 12 is an anode for ionizing the propellant gas supplied into the channel portion 11 by the gas supply pipe 12a and extracting ions. The presence or absence of the supply of the propellant gas into the channel portion 11 by the gas supply pipe 12a and the supply amount of the propellant gas are performed, for example, by controlling the opening and closing of a valve disposed in the gas supply pipe 12a. A valve power source (not shown) may be provided in the power processing unit 20. In this case, the power control unit 100 may control the opening and closing of the valve disposed in the gas supply pipe 12a by controlling the voltage value and current value supplied from the valve power source (not shown) to the valve. The positive electrode side of the anode power source 30 is connected to the anode electrode Ea of the anode 12. That is, the anode power source 30 is connected between the anode 12 (anode electrode Ea) and the hollow cathode body 15a (cathode electrode Ec). In FIGS. 1(b) and 1(c), an example is shown in which the anode electrode Ea is disposed at the end of the housing of the hall thruster 10 in the same manner as the cathode electrode Ec, but the anode 12 itself may serve as the anode electrode Ea.

[0025] The electromagnet 14 generates a magnetic field within the range where the anode 12 is disposed and surrounded by the wall portion 13. The electromagnet 14 has a structure in which a coil is wound around a core material made of a magnetic material. The positive electrode side of the coil power supply 60 is connected to the coil positive electrode Em+ connected to the positive electrode side terminal of the coil. The negative electrode side of the coil power supply 60 is connected to the coil negative electrode Em- connected to the negative electrode side terminal of the coil. The electromagnet 14 generates a magnetic field within the channel portion 11 according to the electric power supplied to the coil by the coil power supply 60. In FIG. 1, the detailed connection between the coil power supply 60 and the coil is omitted, but the electric power from the coil power supply 60 is supplied to each of the coils of the internal electromagnet 14a and the external electromagnet 14b. For example, the electric power from the coil power supply 60 is supplied to each of the coils of the internal electromagnet 14a and the external electromagnet 14b through a path that returns from the positive electrode side of the coil power supply 60 through the coil positive electrode Em+, the positive electrode side terminal of the coil of the external electromagnet 14b, the negative electrode side terminal of the coil of the external electromagnet 14b, the positive electrode side terminal of the coil of the internal electromagnet 14a, the negative electrode side terminal of the coil of the internal electromagnet 14a, and the coil negative electrode Em- to the negative electrode side of the coil power supply 60. The coil positive electrode Em+ and the coil negative electrode Em- are not limited to the configurations corresponding to the coils of the internal electromagnet 14a and the external electromagnet 14b, respectively. For example, it may be configured to include a coil positive electrode Em+ and a coil negative electrode Em- corresponding to the coil of the internal electromagnet 14a and a coil positive electrode Em+ and a coil negative electrode Em- corresponding to the coil of the external electromagnet 14b, that is, a configuration in which the coil positive electrode Em+ and the coil negative electrode Em- are separately provided one by one for each of the coils of the internal electromagnet 14a and the external electromagnet 14b. Furthermore, the configuration for supplying electric power to each of the coils of the internal electromagnet 14a and the external electromagnet 14b is not limited to the coil power supply 60. For example, it may be configured such that the power processing unit 20 does not include the coil power supply 60 (therefore, the coil positive electrode Em+ and the coil negative electrode Em- are not provided). In this case, for example, each of the coils of the internal electromagnet 14a and the external electromagnet 14b may be connected between the hollow cathode body 15a and the cathode electrode Ec.More specifically, the hollow cathode body 15a may be configured to be connected to the cathode electrode Ec via the positive terminal of the coil of the external electromagnet 14b, the negative terminal of the coil of the external electromagnet 14b, the positive terminal of the coil of the internal electromagnet 14a, and the negative terminal of the coil of the internal electromagnet 14a, so that power is supplied to each of the coil of the internal electromagnet 14a and the coil of the external electromagnet 14b. In this case, when the hollow cathode body 15a draws ions from the plasma in the channel portion 11, the electromagnet 14 causes a current flowing at that time to also flow through the coil, thereby generating a magnetic field corresponding to the power supplied to the coil within the channel portion 11.

[0026] In the Hall thruster 10, the anode 12 and the hollow cathode body 15a are insulated from each other. In the Hall thruster 10, while the generation of a magnetic field within the channel portion 11 by the electromagnet 14 and the application of a high voltage to the anode 12 by the power supplied by the anode power supply 30 occur in this order, or in the reverse order, or simultaneously, when electrons are drawn from the propellant gas ionized by the cathode plasma of the hollow cathode body 15a and released to the channel portion 11 side, a discharge occurs between the anode 12 and the hollow cathode body 15a. This discharge ionizes the propellant gas supplied from the gas supply pipe 12a into the channel portion 11 to generate plasma. In the Hall thruster 10, ions are accelerated and drawn from the plasma due to the potential gradient within the generated plasma, and are ejected from the channel portion 11 into outer space. In the following description, the discharge between the anode 12 and the hollow cathode body 15a is also referred to as "anode ignition", and the plasma within the channel portion 11 generated by this discharge (anode ignition) is also referred to as "anode plasma".

[0027] [Operation of Hall Thruster System] Next, the operation of the Hall thruster system 1 will be described. FIG. 2 is a diagram showing an example of the operation of the Hall thruster system 1 using a voltage generator (igniter unit 40) according to an embodiment. FIG. 2 schematically shows the components related to the extraction of ions that the Hall thruster 10 injects into outer space and their operations. More specifically, FIG. 2 shows each electrode of the anode electrode Ea, the cathode electrode Ec, and the keeper electrode Ek related to the extraction of ions from the anode plasma, which the Hall thruster 10 includes, and the anode power supply 30 and the igniter unit 40 connected to these electrodes. And FIG. 2 shows the igniter unit 40 composed of a resistance element Rig and a capacitor element Cig as an example of the configuration of the igniter unit 40. More specifically, FIG. 2 shows a configuration in which one end of the resistance element Rig becomes the first end a and is connected to the line La, the other end of the resistance element Rig and one end of the capacitor element Cig are connected in series, and the other end of the capacitor element Cig becomes the second end b and is connected to the keeper electrode Ek.

[0028] FIG. 2 shows an example in which the igniter unit 40 is composed of one resistance element Rig and one capacitor element Cig, but the respective numbers of the resistance element Rig and the capacitor element Cig included in the igniter unit 40 are not limited to one. That is, the resistance element Rig may have a configuration in which a plurality of resistance elements are connected in series and parallel. Further, the capacitor element Cig may have a configuration in which a plurality of capacitor elements are connected in series and parallel. For example, when it is assumed that a large amount of current flows through the igniter unit 40, the resistance element Rig may have a configuration in which two resistance elements are connected in parallel. For example, when increasing the capacitance of the capacitor element Cig included in the igniter unit 40 and suppressing deterioration of the frequency characteristics, a configuration in which a plurality of small-capacity capacitor elements are connected in parallel may be used.

[0029] In the following description of the operation of the Hall thruster system 1, for the sake of simplicity, it is assumed that the power related to the extraction of ions from the plasma is supplied to the corresponding components by the control of the power control unit 100. More specifically, at least, the power for controlling the valve to the open state to supply the propellant gas to the anode 12 is supplied from a valve power supply (not shown) to the valve disposed in the gas supply pipe 12a. In addition, power may be supplied from the heater power supply 50 to the heater 15c to heat an emitter or an electron-emitting material (not shown), and power may be supplied from the coil power supply 60 to the coil constituting the electromagnet 14 to generate a magnetic field in the channel section 11.

[0030] FIG. 2 shows the impedance component Zk of the space between the keeper electrode Ek and the cathode electrode Ec, and shows the impedance component Za of the space between the anode electrode Ea and the cathode electrode Ec. In FIG. 2, each of the impedance component Zk and the impedance component Za is indicated by the symbol of resistance, but each of the impedance component Zk and the impedance component Za includes an inductance component and a capacitance component in addition to the resistance component. Each of the impedance component Zk and the impedance component Za has a high resistance value of, for example, several M[Ω] or more when the voltage applied to the corresponding electrode is low (when keeper ignition or anode ignition has not occurred), and functions as an insulation resistance with an infinite resistance value, so that no current flows between the electrodes. On the other hand, when the voltage applied to the corresponding electrode becomes high and keeper ignition or anode ignition occurs, each of the impedance component Zk and the impedance component Za becomes a low resistance value of, for example, several k[Ω] (it may be several tens to several hundreds of [Ω]) due to the plasma that becomes a newly generated (appeared) conductor by this discharge, and current flows between the electrodes via the impedance component Zk or the impedance component Za.

[0031] When injecting ions extracted from plasma into space from the Hall thruster 10, the power control unit 100 controls the anode power supply 30 to output a high voltage (here, 300 [V]) and apply it to the anode 12. At this time, the power control unit 100 controls the voltage value of the voltage output from the anode power supply 30 to rise from 0 [V] to 300 [V] with a rise time of, for example, several tens of [μs]. Thereby, the voltage output from the anode power supply 30 is applied to the anode electrode Ea (that is, the anode 12). Fig. 2(a) shows a state where the anode voltage Va from the anode power supply 30 is applied to the anode electrode Ea under the control of the power control unit 100.

[0032] Then, a voltage corresponding to the rise of the anode voltage Va is applied to the keeper electrode Ek (that is, the keeper electrode body 15b) via the igniter unit 40. More specifically, when the anode voltage Va is applied to the anode electrode Ea, the capacitor element Cig included in the igniter unit 40 is charged by the anode voltage Va, and the voltage difference between the anode voltage Va and the voltage of the capacitor element Cig is applied to the keeper electrode Ek. Fig. 2(a) shows a state where the keeper voltage Vk from the igniter unit 40 is applied to the keeper electrode Ek. In the Hall thruster 10 at this stage (a state where keeper ignition has not occurred), a current corresponding to the impedance component Zk and the keeper voltage Vk flows between the keeper electrode Ek and the cathode electrode Ec, but since the impedance component Zk is extremely large, the current value is small. Fig. 2(a) shows, for reference, a state where a predetermined keeper current Ik corresponding to the keeper voltage Vk applied from the igniter unit 40 flows through the keeper electrode Ek, the impedance component Zk of the space between the keeper electrode body 15b and the hollow cathode body 15a, and the cathode electrode Ec.

[0033] Here, the keeper voltage Vk rises to the same voltage value as the anode voltage Va in a predetermined rise time determined by the anode voltage Va that rises according to the control by the power control unit 100, the resistance value of the resistor element Rig, and the capacitance value of the capacitor element Cig. For example, when the anode voltage Va is the same voltage value and the resistor element Rig has the same resistance value, the larger the capacitance value of the capacitor element Cig, the longer it takes to charge (that is, the slower the voltage of the capacitor element Cig rises), but the keeper voltage Vk, which is the value obtained by subtracting the voltage of the capacitor element Cig from the anode voltage Va (the difference), becomes higher. The keeper voltage Vk is a voltage for causing discharge (keeper ignition) between the hollow cathode body 15a and the keeper electrode body 15b, generating cathode plasma, extracting electrons therefrom, and discharging them to the channel section 11 side. Therefore, focusing on keeper ignition, it is considered better to increase the capacitance value of the capacitor element Cig to increase the voltage value of the keeper voltage Vk. However, the fact that the capacitance value of the capacitor element Cig is large means that the volume of the capacitor element Cig, which is a high withstand voltage capacitor element, becomes large and the weight also increases. For this reason, in the igniter unit 40 mounted on the spacecraft, it is considered suitable to adopt a capacitor element Cig with as small a capacitance value as possible within the range where the propellant gas can be ignited, in order to ensure the performance of igniting the propellant gas, miniaturize the igniter unit 40, reduce costs, and further reduce the weight of the spacecraft.

[0034] Thereafter, when the voltage value of the keeper voltage Vk reaches a predetermined voltage value that causes discharge between the hollow cathode body 15a and the keeper electrode body 15b, keeper ignition occurs between the hollow cathode body 15a and the keeper electrode body 15b, and plasma (cathode plasma) is generated. Then, electrons of the propellant gas are drawn out by the potential gradient in the region where this cathode plasma is generated. At this time, since an anode voltage Va (= 300 [V]) is applied to the anode 12, the electrons drawn out from the propellant gas ionized by the cathode plasma move toward the anode 12, that is, are emitted toward the channel portion 11 side. Fig. 2(b) shows a state where the electrons drawn out by the generated cathode plasma are emitted toward the channel portion 11 side.

[0035] At this time, the energy required for the generation of the cathode plasma is supplied by the capacitor element Cig. After the cathode plasma is generated, the keeper voltage Vk becomes a voltage value corresponding to the potential of the cathode plasma at the keeper electrode Ek, and the capacitor element Cig is charged up to the voltage value of the difference between the anode voltage Va and the keeper voltage Vk (anode voltage Va - keeper voltage Vk).

[0036] Incidentally, when keeper ignition occurs between the hollow cathode body 15a and the keeper electrode body 15b, a large current (inrush current) will instantaneously flow through the capacitor element Cig. The resistor element Rig reduces the inrush current that instantaneously flows through this capacitor element Cig. Therefore, focusing on reducing the inrush current flowing through the capacitor element Cig, it is considered better to increase the resistance value of the resistor element Rig to further suppress the peak of the flowing inrush current. However, a large resistance value of the resistor element Rig means that the heat generation (heat generation during steady operation) in the resistor element Rig, which is a high-voltage-resistant resistor, will increase. For this reason, in the igniter unit 40 mounted on the spacecraft, it is preferable to adopt a resistor element Rig with a resistance value such that the peak of the inrush current can be suppressed to the extent that the capacitor element Cig will not be destroyed by the flowing inrush current, in order to miniaturize the igniter unit 40, reduce costs, and further reduce the weight of the spacecraft.

[0037] Thereafter, in the Hall thruster 10, due to the electrons (electrons that have moved toward the anode 12) emitted from the hollow cathode portion 15 toward the channel portion 11 side, discharge (anode ignition) occurs between the anode 12 and the hollow cathode body 15a, and plasma (anode plasma) is generated. Figure 2(c) shows a state in which anode plasma is generated between the anode 12 and the hollow cathode body 15a, and the anode current Ia corresponding to the anode voltage Va is flowing through the anode electrode Ea, the impedance component Za of the space between the anode 12 and the hollow cathode body 15a, and the cathode electrode Ec. As a result, in the Hall thruster 10, the ions of the propellant gas drawn out by the potential gradient inside the anode plasma are accelerated and ejected from the channel portion 11 into outer space. That is, the operation of applying a propulsive force to the spacecraft in the Hall thruster system 1 is started.

[0038] Here, in the Hall thruster 10, the keeper voltage Vk during the operation of injecting ions from the channel portion 11 is fixed at a constant voltage value while vibrating. For this reason, in the igniter portion 40, the capacitor element Cig continues to be charged with the voltage of the difference between the anode voltage Va and the keeper voltage Vk (anode voltage Va - keeper voltage Vk). In other words, in the Hall thruster system 1, while the Hall thruster 10 continues the steady operation of applying thrust to the spacecraft, a small amount of alternating component current in the keeper current Ik remains flowing, but it does not cause a large loss and the spacecraft can continue to be given thrust. That is, in the Hall thruster system 1, it can continue the steady operation with almost no power loss or heat generation.

[0039] [Modification example of the configuration of the igniter portion (Part 1)] In FIG. 2, an example is shown in which the igniter portion 40 is configured by the resistor element Rig and the capacitor element Cig. However, the configuration of the igniter portion 40 is not limited to the configuration shown in FIG. 2. FIG. 3 is a diagram showing an example of another configuration in the voltage generation device (igniter portion 40) according to the embodiment. FIG. 3 shows two other examples of the configuration of the igniter portion 40.

[0040] Figure 3(a) shows an example of an igniter unit 40 (hereinafter referred to as "igniter unit 40a") composed of a capacitor element Cig. That is, Figure 3(a) shows an igniter unit 40a with a configuration in which the resistance element Rig is omitted in the igniter unit 40 shown in Figure 2. In the igniter unit 40a, one end of the capacitor element Cig serves as the first end a and is connected to the line La, and the other end of the capacitor element Cig serves as the second end b and is connected to the keeper electrode Ek. Also in the igniter unit 40a, similar to the example shown in Figure 2(a), a keeper voltage Vk corresponding to the rise of the anode voltage Va is applied to the keeper electrode Ek. Figure 3(a) also shows a state in which the keeper voltage Vk from the igniter unit 40a is applied to the keeper electrode Ek, similar to the example shown in Figure 2(a). Even in the configuration shown in Figure 3(a), at this stage (the state where keeper ignition has not occurred) in the hollow thruster 10, a current flows according to the impedance component Zk between the keeper electrode Ek and the cathode electrode Ec and the keeper voltage Vk, but since the impedance component Zk is extremely large, the current value is small. Figure 3(a) also shows, for reference, a state in which a predetermined keeper current Ik corresponding to the keeper voltage Vk applied from the igniter unit 40a flows through the keeper electrode Ek, the impedance component Zk in the space between the keeper electrode body 15b and the hollow cathode body 15a, and the cathode electrode Ec, similar to the example shown in Figure 2(a). As described above, the resistance element Rig reduces the inrush current that instantaneously flows through the capacitor element Cig when keeper ignition occurs between the hollow cathode body 15a and the keeper electrode body 15b. Therefore, if the inrush current that instantaneously flows through the capacitor element Cig when keeper ignition occurs is within the allowable range, or if the inrush power can be suppressed (reduced) by the resistance component of the capacitor element Cig, the resistance element Rig can be omitted in the igniter unit 40, and a configuration with only the capacitor element Cig can be adopted. In this case, in the igniter unit 40a, the igniter unit 40 can be further miniaturized and cost-reduced, and the spacecraft can be further lightened.

[0041] FIG. 3(b) shows an example of the igniter unit 40 (hereinafter referred to as "igniter unit 40b") constituted by the resistance element Rig. That is, FIG. 3(b) shows an igniter unit 40b having a configuration in which the capacitor element Cig is omitted in the igniter unit 40 shown in FIG. 2. In the igniter unit 40b, one end of the resistance element Rig serves as the first end a and is connected to the line La, and the other end of the resistance element Rig serves as the second end b and is connected to the keeper electrode Ek. Also in the igniter unit 40b, similar to the example shown in FIG. 2(a), the keeper voltage Vk corresponding to the rise of the anode voltage Va is applied to the keeper electrode Ek. FIG. 3(b) also shows a state in which the keeper voltage Vk from the igniter unit 40b is applied to the keeper electrode Ek, similar to the example shown in FIG. 2(a). Even in the configuration shown in FIG. 3(b), in the hollow thruster 10 at this stage (a state where keeper ignition has not occurred), a current flows according to the impedance component Zk between the keeper electrode Ek and the cathode electrode Ec and the keeper voltage Vk, but since the impedance component Zk is extremely large, the current value is small. FIG. 3(b) also shows, for reference, a state in which a predetermined keeper current Ik corresponding to the keeper voltage Vk applied from the igniter unit 40b flows through the keeper electrode Ek, the impedance component Zk of the space between the keeper electrode body 15b and the hollow cathode body 15a, and the cathode electrode Ec, similar to the example shown in FIG. 2(a). As described above, the capacitor element Cig is continuously charged with the voltage of the difference between the anode voltage Va and the keeper voltage Vk (anode voltage Va - keeper voltage Vk), so that a small amount of alternating current component flows in the keeper current Ik, but it does not cause a large loss. In other words, the capacitor element Cig suppresses the direct current component of the keeper current Ik flowing while the hollow thruster 10 is in a steady operation by combining with the resistance element Rig. Therefore, if it is possible to allow a small direct current component to flow in the keeper current Ik while the hollow thruster 10 is in a steady operation and for the loss to increase slightly due to this small direct current component, the capacitor element Cig can be omitted in the igniter unit 40 and the configuration can be made only of the resistance element Rig.In this case, in the igniter unit 40b, the igniter unit 40 can be further miniaturized and cost-reduced, and the spacecraft can be further lightened.

[0042] The igniter unit 40a and the igniter unit 40 are also examples of a "voltage generation device".

[0043] [Modification Example of the Configuration of the Igniter Unit (Part 2)] In FIG. 2, an example is shown in which the igniter unit 40 is connected (arranged) between the anode electrode Ea and the keeper electrode Ek of the hall thruster 10. However, the connection between the igniter unit 40 and the hall thruster 10 is not limited to the connection shown in FIG. 2. FIG. 4 is a diagram showing an example of still another configuration in the voltage generation device (igniter unit 40) according to the embodiment.

[0044] The igniter unit 41 shown in FIG. 4(a) has a configuration in which a protection circuit 70 is added to the igniter unit 40 shown in FIG. 2. The protection circuit 70 is a circuit that absorbs a surge current (inrush current) that transiently flows when keeper ignition occurs, that is, a so-called snubber circuit. In the igniter unit 41, the igniter unit 40 and the protection circuit 70 are connected in series. More specifically, in the igniter unit 41, the first end a of the igniter unit 40 is connected to the line La on the positive electrode side of the anode power supply 30, and the second end b of the igniter unit 40 is connected to the keeper electrode Ek. Then, in the igniter unit 41, the first end c of the protection circuit 70 is connected to the line connecting the second end b of the igniter unit 40 and the keeper electrode Ek, and the second end d of the protection circuit 70 is connected to the cathode electrode Ec. Thereby, in the igniter unit 41, the protection circuit 70 absorbs the inrush current that transiently flows between the keeper electrode Ek and the cathode electrode Ec when keeper ignition occurs, and protects the hollow cathode portion 15.

[0045] The protection circuit 70 has a configuration in which, for example, as shown in FIG. 4(b), a resistor element Rs and a capacitor element Cs are connected in series. More specifically, in the protection circuit 70, one end of the resistor element Rs serves as the first terminal c and is connected to the igniter unit 40 and the keeper electrode Ek, the other end of the resistor element Rs and one end of the capacitor element Cs are connected in series, and the other end of the capacitor element Cs serves as the second terminal d and is connected to the cathode electrode Ec. The configuration of the protection circuit 70 is not limited to the configuration shown in FIG. 4(b). The protection circuit 70 may be configured, for example, by a Zener diode element instead of the resistor element Rs and the capacitor element Cs, or may be configured to include a Zener diode element in addition to the resistor element Rs and the capacitor element Cs.

[0046] The igniter unit 41 is also an example of a "voltage generating device".

[0047] [Modification Example of Connection of Igniter Unit] In the above-described embodiments and modification examples, the configuration of the anode power supply 30 has not been described in detail. Therefore, in FIG. 2, the case where the first terminal a of the igniter unit 40 is connected to the positive-side line La of the anode power supply 30 has been described. However, depending on the configuration of the anode power supply 30, the first terminal a of the igniter unit 40 (which may be the igniter unit 40a or the igniter unit 40b) may be connected to a line different from the line La of the anode power supply 30. An example of this case will be described below. FIG. 5 is a diagram showing a configuration of an anode power supply 30 used by a voltage generating device (igniter unit 40) according to an embodiment, and an example of the connection of the voltage generating device (igniter unit 40). FIG. 5 shows two examples of the configuration of an anode power supply 30 having a maximum voltage value of 300 [V].

[0048] Fig. 5(a) shows an example in which an anode power supply 30 (hereinafter referred to as "anode power supply 30a") is configured by connecting three DC / DC converters 31 (DC / DC converters 31A to 31C) in series. Each of the DC / DC converter 31A, the DC / DC converter 31B, and the DC / DC converter 31C is, for example, a DC / DC converter that converts (boosts) the voltage of a system power supply in a spacecraft and outputs it. The system power supply is, for example, a storage battery that stores the power generated by a solar cell paddle (solar power generation device) provided in the spacecraft. In the case of the example shown in Fig. 5(a), each DC / DC converter 31 outputs a voltage with a voltage value of 100 [V]. When the first end a of the igniter unit 40 is connected to the positive electrode side of the DC / DC converter 31A that constitutes the anode power supply 30a, the operation of the Hall thruster system 1 is the same as the operation of the Hall thruster system 1 shown in Fig. 2. On the other hand, in the igniter unit 40 shown in Fig. 5(a), the first end a is connected to a line Laa in which the positive electrode side of the DC / DC converter 31B and the negative electrode side of the DC / DC converter 31A are connected, and the second end b is connected to the keeper electrode Ek. In this case, the igniter unit 40 generates an output voltage with a magnitude (voltage value) corresponding to the input voltage at the first end a, that is, the voltage value (voltage value = 200 [V]) of the voltage output from the positive electrode side of the DC / DC converter 31A, and outputs it from the second end b. Thereby, in the example shown in Fig. 5(a), while reducing the voltage of the capacitor element Cig included in the igniter unit 40 below the voltage of the capacitor element Cig included in the igniter unit 40 shown in Fig. 2 (here, the voltage value = 300 [V] is set to 200 [V]), the same operation as the igniter unit 40 shown in Fig. 2 can be performed. For this reason, in the igniter unit 40 shown in Fig. 5(a), it is possible to adopt a capacitor element Cig with low withstand voltage while ensuring the performance of igniting the propulsive gas, and the options for the capacitor element Cig included are expanded compared to the igniter unit 40 shown in Fig. 2, and there is a possibility that the igniter unit 40 can be further miniaturized and lightened. And when the miniaturization of the igniter unit 40 is realized, the spacecraft can be further lightened.

[0049] Fig. 5(b) shows an example of a case where an anode power supply 30 (hereinafter referred to as "anode power supply 30b") is configured by connecting three batteries 32 (batteries 32A to 32C) in series. Each of the battery 32A, the battery 32B, and the battery 32C stores, for example, a voltage charged by a system power supply in a spacecraft using a storage battery. Also in the example shown in Fig. 5(b), each battery 32 outputs a voltage with a voltage value = 100 [V]. When the first end a of the igniter unit 40 is connected to the positive electrode side of the battery 32A that constitutes the anode power supply 30b, the operation of the Hall thruster system 1 is the same as the operation of the Hall thruster system 1 shown in Fig. 2. On the other hand, for the igniter unit 40 shown in Fig. 5(b), the first end a is connected to a line Lab where the positive electrode side of the battery 32B and the negative electrode side of the battery 32A are connected, and the second end b is connected to the keeper electrode Ek. Also in this case, the igniter unit 40 generates an output voltage with a magnitude (voltage value) corresponding to the input voltage at the first end a, that is, the voltage value (voltage value = 200 [V]) of the voltage output from the positive electrode side of the battery 32A, and outputs it from the second end b. As a result, also in the example shown in Fig. 5(b), similar to the example shown in Fig. 5(a), while reducing the voltage of the capacitor element Cig included in the igniter unit 40 below the voltage of the capacitor element Cig included in the igniter unit 40 shown in Fig. 2 (here too, the voltage value = 300 [V] is set to 200 [V]), it is possible to perform the same operation as the igniter unit 40 shown in Fig. 2. Therefore, also for the igniter unit 40 shown in Fig. 5(b), similar to the igniter unit 40 shown in Fig. 5(a), it is possible to adopt a capacitor element Cig with low withstand voltage while ensuring the performance of igniting the propulsive gas, and the options for the capacitor element Cig included are expanded compared to the igniter unit 40 shown in Fig. 2, and there is a possibility that the igniter unit 40 can be further miniaturized and lightened. And when the miniaturization of the igniter unit 40 is achieved, the spacecraft can be further lightened.

[0050] As described above, the igniter unit 40 can be connected according to the configuration of the anode power supply 30 and the power (voltage value) supplied to the keeper electrode Ek (that is, the keeper electrode body 15b). FIG. 5 shows a case where the anode power supply 30 is configured with three DC / DC converters 31 or three batteries 32. However, even when the anode power supply 30 is configured with four or more DC / DC converters 31 or four or more batteries 32, it can be considered in the same way as the above example. In this case, the configuration and operation should be made equivalent to those shown in FIG. 5. Therefore, detailed descriptions of the configuration and operation of the hall thruster system 1 in the case where the number of DC / DC converters 31 or batteries 32 constituting the anode power supply 30 is different are omitted.

[0051] The DC / DC converter 31 and the battery 32 are examples of a "power module". The DC / DC converter 31A and the battery 32A are examples of a "first power module", and the DC / DC converter 31B and the battery 32B are examples of a "second power module". The line Laa and the line Lab are examples of a "line connecting the first power module and the second power module in series" and are also examples of a "first line".

[0052] As described above, in the Hall thruster system 1 including the power processing unit 20 to which the igniter unit 40 of the embodiment is applied, the keeper power supply included in the power processing unit in the conventional Hall thruster system is eliminated (deleted), and instead, the igniter unit 40 is configured by both or only one of the passive elements of the resistor element Rig and the capacitor element Cig. And also in the igniter unit 40 of the embodiment, similar to the conventional keeper power supply, keeper ignition is caused between the hollow cathode body 15a and the keeper electrode body 15b, and electrons drawn from the propellant gas supplied into the hollow cathode body 15a from the gas supply pipe 15d are emitted to the channel unit 11 side by the cathode plasma generated by the keeper ignition. Thereby, also in the Hall thruster system 1 including the power processing unit 20 to which the igniter unit 40 of the embodiment is applied, similar to the conventional Hall thruster system, anode ignition is caused between the anode 12 and the hollow cathode body 15a, and ions obtained by ionizing and extracting the propellant gas by the anode plasma generated by the anode ignition are accelerated by the electric field inside the anode plasma and ejected from the channel unit 11 into outer space. Thereby, also in the Hall thruster system 1 including the power processing unit 20 to which the igniter unit 40 of the embodiment is applied, similar to the conventional Hall thruster system, a propulsion force can be applied to the spacecraft. Moreover, since the igniter unit 40 of the embodiment is configured by only passive elements, it can be miniaturized and cost-reduced compared to the conventional keeper power supply, and weight reduction of the spacecraft equipped with the Hall thruster system 1 including the power processing unit 20 to which the igniter unit 40 of the embodiment is applied can be realized.

[0053] In the above-described embodiment, the case where the igniter unit 40 is provided in the power processing unit 20 has been described. However, the igniter unit 40 is not limited to the configuration provided in the power processing unit 20. For example, the igniter unit 40 may be configured to be provided in the Hall thruster 10. In this case, the configuration and operation of the Hall thruster system 1, that is, the igniter unit 40, the power processing unit 20, and the Hall thruster 10, may be made equivalent to the configuration and operation of the Hall thruster system 1 including the power processing unit 20 to which the igniter unit 40 of the above-described embodiment is applied. Therefore, detailed description of the configuration and operation of the Hall thruster system 1 in which the igniter unit 40 is provided in the Hall thruster 10 is omitted.

[0054] As described above, the embodiments for implementing the present invention have been described using the embodiments. However, the present invention is not limited to such embodiments, and various modifications and substitutions can be made without departing from the gist of the present invention.

Description of Reference Numerals

[0055] 1 ··· Hall thruster system 10 ··· Hall thruster 11 ··· Channel section 12 ··· Anode 12a ··· Gas supply pipe 13 ··· Wall section 14 ··· Electromagnet 14a ··· Internal electromagnet 14b ··· External electromagnet 15 ··· Hollow cathode section 15a ··· Hollow cathode body 15b ··· Keeper electrode body 15c ··· Heater 15d ··· Gas supply pipe 20 ··· Power processing unit (PPU) 30, 30a, 30b ··· Anode power supply 31, 31A, 31B, 31C ··· DC / DC converter 32, 32A, 32B, 32C ··· Battery 40, 40a, 40b, 41 ··· Igniter section 50 ··· Heater power supply 60 ··· Coil power supply 70 ··· Protection circuit 100 ··· Power control unit Ea ··· Anode electrode Ec ··· Cathode electrode Ek ··· Keeper electrode Eh ··· Heater electrode Em+ ··· Coil positive electrode Em- ··· Coil negative electrode Rig ··· Resistive element Rs ··· Resistive element Cig ··· Capacitor element Cs ··· Capacitor element

Claims

1. A voltage generation device provided in a Hall thruster system for generating the propulsion force of a space machine, The first end is connected to the first line on the anode electrode side in the anode power supply that supplies power between the anode electrode and the cathode electrode of the Hall thruster constituting the Hall thruster system, and the second end that outputs an output voltage corresponding to the input voltage of the first end is connected to a keeper electrode disposed close to a hollow cathode connected to the cathode electrode. Voltage generation device.

2. The first line is a line connecting the anode power supply and the anode electrode, The voltage generation device according to claim 1.

3. In the anode power supply, a plurality of power modules are connected in series, The first end is connected to a line connecting any first power module and a second power module in series, The voltage generation device according to claim 1.

4. The power module is a DC / DC converter, The voltage generation device according to claim 3.

5. The power module is a battery, The voltage generation device according to claim 3.

6. A resistance element; A capacitor element; Comprising, One end of the resistance element is connected to the first end, the other end of the resistance element and one end of the capacitor element are connected in series, and the other end of the capacitor element is connected to the second end, The voltage generation device according to any one of claims 1 to 5.

7. A capacitor element, Comprising, One end of the capacitor element is connected to the first end, and the other end of the capacitor element is connected to the second end, The voltage generation device according to any one of claims 1 to 5.

8. A resistance element, Comprising, One end of the resistance element is connected to the first end, and the other end of the resistance element is connected to the second end, The voltage generation device according to any one of claims 1 to 5.

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