JP6214874B2 - Gas supply method and system for plasma ignition of ion engine - Google Patents

Description

  The present invention relates to a gas supply method and system for plasma ignition of an ion engine, and more particularly, to a gas supply method and system for plasma ignition of an ion engine that can surely make a propellant into plasma at the start of discharge.

  An ion engine is an electric propulsion system that obtains thrust by converting a propellant, for example, xenon gas into plasma by direct current discharge or microwave discharge, and applying a voltage to the plasmaized cations (xenon ions) to release the thrust. It is used for orbit control and attitude control of satellites. A schematic configuration of a conventional ion engine is shown in FIG. A propellant such as xenon gas is stored in the propellant storage tank 11 at a high pressure, and the propellant is once sent to the low pressure tank 13 via the pipe 17 and further from the low pressure tank 13 via the thruster valve 19 to the ion source. 3 plasma generation chamber 3 a and neutralization unit 5 plasma generation chamber 5 a. A pressure regulating valve 15 for adjusting the pressure is disposed in the pipe 17 between the high pressure tank 11 and the low pressure tank 13, and a flow restrictor 18 for controlling the flow rate of the propellant is disposed upstream of the thruster valve 19. Has been. The pipe 17 communicates with the ion source 3 and the neutralizer 5.

  On the other hand, the plasma generation chamber 3a of the ion source 3 and the plasma generation chamber 5a of the neutralizer 5 are respectively connected to the microwave power source 30 by a coaxial cable 40, and the microwave generated by the microwave power source 30 is connected to the coaxial cable. The propellant is converted into plasma by being supplied to the plasma generation chambers 3a and 5a through 40, respectively. The electrons generated in the plasma generation chamber 3a of the ion source 3 are transported to the plasma generation chamber 5a of the neutralizer 5 by wiring not shown.

  The ion source 3 is provided with an ion acceleration unit 4 for accelerating the ions generated in the plasma generation chamber 3a. The ion acceleration unit 4 includes a screen grid 4a and an accelerator grid 4b. A screen grid 4a is disposed facing the plasma generation chamber 3a, and the screen grid 4a is a mesh-like member having a large number of openings (holes) having a diameter of about 0.5 to 5.0 mm. The outer accelerator grid 4b disposed adjacent to the screen grid 4a is a mesh-like member having a large number of hole diameters (opening (hole) having a diameter of about 1 mm) that is about half the hole diameter of the screen grid 4a. It is. The screen grid 4a and the accelerator grid 4b are positioned so as to be aligned with each other so that the hole centers coincide. The hole size of the screen grid 4a is formed larger than the hole size of the accelerator grid 4b. This is because the aperture area ratio is increased to extract a large number of ions and accelerate / discharge them to the outside. Note that another grid (decel grid) may be provided behind the accelerator grid 4b.

  Then, a positive voltage is applied from the power supply unit 7 to the screen grid 4a, and a negative voltage is applied from the power supply unit 7 to the accelerator grid 4b. It is attracted by and accelerated to be emitted as an ion beam.

  On the other hand, if only positive ions are emitted, the satellite side will be negatively charged, and the positive ions released will return to the satellite side and become thrust, so that the emitted ion beam A neutralizer 5 is provided to neutralize the ion beam with the same amount of electrons and prevent the ion engine from being charged. Therefore, a propellant is also supplied to the neutralizer 5 and a negative voltage is applied by the power supply unit 7. Although some of the positive ions generated in the plasma generation chamber 5a of the neutralizer 5 are emitted together with the electrons, the remaining positive ions are combined with the electrons carried from the plasma generation chamber 3a of the ion source 3. Then, it returns to neutral xenon, and is converted into plasma again by the microwave supplied from the microwave power source 30 and recycled.

  Regarding the flow rate adjustment of the propellant of the ion engine, for example, there is one shown in Patent Document 1. Patent Document 1 discloses a technique for appropriately controlling the flow rate of a propellant by correcting a calibration coefficient for propellant flow rate control on a trajectory when a deviation occurs between the flow rate signal of the propellant and an actual flow rate. It is about.

JP-A-9-287550

  In the conventional large-sized microwave discharge ion engine, the discharge chamber size is large, a sufficient volume area ratio is ensured, and a sufficiently large microwave power can be supplied. There was no. However, in a small ion engine, the plasma ignition chambers 3a and 5a are reduced in volume area ratio (relative increase in loss area) and the usable microwave power is reduced, so that the plasma ignition non-ignition is reduced. It was a big problem. That is, plasma ignition becomes difficult by reducing the plasma generation chambers 3a, 5a size, microwave power, and gas flow rate.

  As a basic method for increasing the plasma ignition probability, for example, (1) an increase in volume area ratio, (2) an increase in microwave power, and (3) an increase in gas flow rate can be considered. In this regard, in a small ion engine, a change accompanying an increase in size is essentially impossible. In the operation of an ion engine, the propellant (xenon gas) is reliably ignited (plasmaized) at the start of the initial operation, while the thrust is continuously maintained at the optimum operating point in the steady acceleration phase. There is a need. However, the flow restrictor is designed to control the flow rate of the propellant so that the flow rate becomes an optimum value in order to realize the optimum operation in steady acceleration. Furthermore, an increase in microwave power, DC discharge power, and gas flow rate is not preferable because it leads to an increase in power consumption and a decrease in specific thrust, that is, a decrease in performance. However, it is considered that if these increases are not steady, but can only be temporarily increased, the probability of plasma ignition can be significantly increased while suppressing a decrease in performance.

  Accordingly, the present invention has been made in view of such problems, and it is possible to control the flow rate of the propellant to ensure the initial reliable ion ignition while realizing the optimization of the flow rate of the propellant in steady operation. And providing a gas supply method and system for plasma ignition of an ion engine capable of reliably igniting a propellant and turning it into a plasma without greatly changing the system even in a small ion engine. Objective.

In order to solve the above-mentioned problem, the invention according to claim 1 controls the flow rate of the propellant supplied from the accumulator that temporarily stores the propellant stored in the propellant storage tank to the ion source and neutralizer. a flow restrictor which, promote gas reservoir storing the propellant is provided, pooled in the gas reservoir at discharge start between the thruster valve for controlling the supply or stop of the propellant into the ion source and neutralizer to provide an ion engine method of a plasma ignition gas supply, characterized in that the plasma ignition by supplying agent temporarily higher flow rate than the steady state.

In order to solve the above-mentioned problem, the present invention described in claim 2 is the method of supplying gas for plasma ignition of an ion engine according to claim 1, wherein the propellant is radiated to a plasma generation chamber irradiated with microwaves in advance. Thus, plasma ignition is performed.

  In order to solve the above-mentioned problem, the present invention according to claim 3 is configured to control the flow rate of the propellant supplied from the accumulator that temporarily stores the propellant stored in the propellant storage tank to the ion source and the neutralizer. Plasma ignition of an ion engine, characterized in that a gas reservoir for storing propellant is provided between a flow restrictor to be controlled and a thruster valve for controlling supply or stop of propellant to the ion source and neutralizer. A gas supply system is provided.

  According to the gas supply method and system for plasma ignition of an ion engine according to the present invention, a gas reservoir is provided between the flow restrictor and the thruster valve, and the propellant stored in the gas reservoir is released at a stroke only at the time of initial ignition. As a result, it is possible to ensure reliable ignition, and at the time of steady acceleration operation, an optimal acceleration operation can be performed by the propellant flow restrictor. Thereby, even if it is a small ion engine, there exists an effect that plasma ignition can be carried out reliably. The temporary increase in gas flow rate decreases the specific thrust, but the time is about 0.1 to 1.0 seconds, which is extremely short compared to the operation time of the ion engine in the normal mode. There is almost no influence.

1 is a block diagram showing one embodiment of a gas supply system for plasma ignition of an ion engine according to the present invention. It is sectional drawing which shows one Embodiment of a gas reservoir. It is a schematic block diagram of the conventional ion engine.

  Hereinafter, a preferred embodiment of a gas supply method and system for plasma ignition of an ion engine according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a gas supply system for plasma ignition of an ion engine according to the present invention. In addition, about the structure part similar to the conventional ion engine, the same code | symbol as FIG. 3 is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 1, the plasma ignition gas supply system 10 constituting the ion engine 1 includes a propellant storage tank 11 that stores a propellant such as xenon gas at a high pressure, for example, about 7 Mpa, a low pressure propellant, For example, a low-pressure tank (accumulator) 13 for storing at 0.03 Mpa is provided, and a pressure regulating valve 15 for adjusting pressure is disposed in a pipe 17 between the propellant storage tank 11 and the low-pressure tank 13. The propellant is sent from the low-pressure tank 13 through the thruster valve 19 to the plasma generation chamber 3a of the ion source 3 and the plasma generation chamber 5a of the neutralizer 5, and on the upstream side of the thruster valve 19, A flow restrictor 18 for controlling the flow rate of the propellant is disposed.

  Since the plasma generation chamber 3a of the ion source 3 and the plasma generation chamber 5a of the neutralizer 5 are directly connected to vacuum, the propellant flows in at a flow rate corresponding to the pressure in the low-pressure tank 13. Then, the relationship between the pressure and the flow rate is determined by the flow rate restrictor 18, and the propellant supply ON / OFF control is executed by opening and closing the thruster valve 19.

  In the present invention, a gas reservoir 20 is provided between the downstream side of the flow restrictor 18 and the upstream side of the thruster valve 19. For example, as shown in FIG. 2, the gas reservoir 20 includes a storage chamber 21 in which a predetermined amount of propellant is temporarily stored. In such a configuration, the gas reservoir 20 is in a state where the thruster valve 19 is closed. The propellant having the same pressure as the low-pressure tank 13 is accumulated. Since the propellant stored in the gas reservoir 20 is downstream of the flow restrictor 18, the plasma generation chamber 3a and the ion source 3 of the ion source 3 are not affected by the flow restrictor 18 the next time the thruster valve 19 is opened. It is discharged toward the plasma generation chamber 5a of the neutralizer 5. In the gas reservoir 20 shown in FIG. 2, the diameter of the pipe 17a on the side communicating with the flow restrictor 18 and the diameter of the pipe 17b on the side communicating with the thruster valve 19 are the same. By making the size larger than the diameter size of the pipe 17a, a propellant having a high flow rate can be discharged into the plasma generation chamber 3a of the ion source 3 and the plasma generation chamber 5a of the neutralizer 5 in a short time. . The power supply unit 7, the pressure regulating valve 15, the flow restrictor 18, the thruster valve 19, and the microwave power supply 30 are controlled by the control device 50. The control device 50 is a so-called computer, and includes a central processing unit, a storage device, an input / output interface, a communication device, and the like (not shown), but since the specific contents thereof are publicly known, detailed description thereof is omitted.

  This gas flow is determined by the gas conductance from the thruster valve 19 to the ion source 3 and the neutralizer 5 and can release a much higher flow rate of propellant than through the flow restrictor 18. The duration and maximum value of this temporarily large gas flow can be adjusted by the size of the gas reservoir 20 and the gas conductance from the thruster valve 19 to the ion source 3 and to the neutralizer 5. The required time is about 0.1 to 1.0 seconds. And after discharge | release of the propellant temporarily stored in the gas reservoir 20 is complete | finished, the setting flow volume by the flow restrictor 18 flows, and it transfers to normal operation mode. Thus, the time required for plasma ignition is very short compared to the typical ion engine operating time (several hours to one year), and therefore there is almost no influence on the reduction of the specific thrust.

  According to the present invention, in a small ion engine directly related to orbit control necessary for reliable mission execution in an ultra-small artificial satellite or the like that is required to be extremely strict and lightweight, it is temporarily in a steady state when the engine is started. Plasma ignition can be reliably performed by flowing a higher gas flow rate.

  As described above, the preferred embodiment of the present invention has been described in detail. However, the present invention is not limited to the specific embodiment, and within the scope of the gist of the present invention described in the claims, Needless to say, various modifications and changes are possible. For example, the propellant is converted into plasma, not limited to microwave discharge, but may be discharge electrode type.

DESCRIPTION OF SYMBOLS 1 Ion engine 3 Ion source 3a Plasma generation chamber 4 Ion acceleration part 4a Screen grid 4b Accel grid 5 Neutralizer 5a Plasma generation chamber 7 Power supply unit 10 Plasma ignition gas supply system 11 Progressive agent storage tank 13 Low pressure tank 17 Pipe 18 Flow rate Limiter 19 Thruster valve 20 Gas reservoir 21 Storage chamber 30 Microwave power source 40 Coaxial cable 50 Control device

Claims (3)

A flow restrictor for controlling the flow rate of the propellant supplied to the ion source and neutralizer from an accumulator that temporarily stores the propellant stored in the propellant storage tank, and propulsion to the ion source and neutralizer by providing a temporary higher rate than the steady state provided reservoir gas accumulating propellant, the propellant pooled in the gas reservoir at discharge start between the thruster valve for controlling the supply or stop of agents A plasma ignition gas supply method for an ion engine, characterized by performing plasma ignition. The method for supplying gas for plasma ignition of an ion engine according to claim 1,
Ion engines method of a plasma ignition gas supply, characterized in that the plasma ignition by emitting the plasma generation chamber which is irradiated in advance microwaves the propellant.   A flow restrictor for controlling the flow rate of the propellant supplied to the ion source and neutralizer from an accumulator that temporarily stores the propellant stored in the propellant storage tank, and propulsion to the ion source and neutralizer A gas supply system for plasma ignition of an ion engine, wherein a gas reservoir for storing a propellant is provided between a thruster valve for controlling supply or stop of the agent.

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