JP2014173534A - Microwave power source starting power-up circuit used for small-sized low power consumption ion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave power source starting power-up circuit capable of increasing a microwave output at the time of starting a small-sized low power consumption ion engine, ionizing or plasma forming through a positive ignition, decreasing output of microwave under a stabilized acceleration phase and restricting a consumption power of the ion engine.SOLUTION: There are provided an attenuator 33 for increasing an output of microwave power when a microwave power source 30 of an ion engine 1 is started and decreasing the output of microwave power when an operation reaches a normal acceleration phase, and an attenuation amount control circuit 34 for controlling the attenuator, and an engine function is promoted while restricting the power consumption of a small-sized low power consumption ion engine 1.

Description

  The present invention relates to an ion engine for performing orbit control necessary for performing a mission in a micro-satellite or the like that is required to be small and light, especially a microwave power source used for a small and low power consumption ion engine. In more detail, the power-up circuit at the time of start-up outputs microwave power that is higher than the steady state at the start of discharge, and when the steady state is reached, the microwave power is reduced to save power. The present invention relates to a power-up circuit at the start-up time of a microwave power source.

  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 connected to the microwave power source 30 by a coaxial cable 40, respectively.
Microwaves generated by the microwave power supply 30 are supplied to the plasma generation chambers 3a and 5a via the coaxial cable 40, and the propellant is turned into plasma. 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, and is emitted to the outside 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 electrically neutralize the ion beam with the same amount of electrons and prevent charging of the ion engine. Therefore, a propellant is also supplied to the neutralizer 5 and a negative voltage is applied by the power supply unit 7. Some of the positive ions generated in the plasma generation chamber 5 a of the neutralizer 5 are emitted together with the electrons, but the remaining positive ions are combined with the electrons carried from the plasma generation chamber 3 a 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.

Here, for example, Patent Document 1 discloses a technique related to the plasma formation of a propellant in miniaturization of a microwave discharge ion engine. Japanese Patent Application Laid-Open No. 2004-151561 aims to achieve a reduction in size of an ion engine by enabling a single plasma source to operate as both an ion source and an electron source in a microwave discharge ion engine.
Patent Document 2 discloses a technique for generating plasma that is used as an ion engine by generating plasma by generating cyclotron resonance with microwaves.

JP 2009-162178 A Japanese Patent Laid-Open No. 5-172038

Xenon is mainly used as a propellant for ion engines powered by microwaves on small satellites. However, when starting the plasma of propellants with certainty, it requires more power than the low-frequency microwave output. I need.
However, the conventional ion engine supplies the microwave power without reducing it even after the discharge is started by the microwave power required at the start of the discharge and the plasma of the propellant is started. Therefore, there is a problem that more power than necessary is supplied in a steady state and power is consumed wastefully. Especially for small satellites with severe power balance, waste of power must be eliminated as much as possible. In this respect, the above-mentioned Patent Documents 1 and 2 do not show recognition of such a problem.

  Therefore, the present invention has been made in view of the problems in the prior art, and it is converted into plasma only during several tens of milliseconds to several seconds when discharge is started in order to ensure the initial reliable plasma ignition in the ion engine. Provide a power-up circuit at the start-up of a microwave power source used in a small, low-power ion engine that reduces microwave power and suppresses power consumption after a sufficient amount of power is supplied and after transition to a stable discharge state For the purpose.

  In order to solve the above-mentioned problems, the present invention according to claim 1 is directed to a microwave oscillation circuit unit that generates a microwave, and an attenuation that attenuates the microwave output from the microwave oscillation circuit unit to an appropriate signal level. And a control circuit for controlling the attenuation amount from the time of starting the reactor to a predetermined time to be smaller than the attenuation amount in a steady state. Provide a power-up circuit at start-up of a microwave power source.

  In order to solve the above-mentioned problem, the present invention described in claim 2 is directed to a microwave output from a microwave oscillation circuit unit provided in a preceding stage of a microwave power source that generates microwave power for converting a propellant into plasma. An attenuator that attenuates the wave to an appropriate signal level is disposed, and an attenuation control circuit that is connected to the attenuator and can control the attenuation by Hi / Low of the bit in the attenuator is provided. By reducing the attenuation amount of the attenuator, the input to the microwave power amplifier circuit provided at the final stage of the microwave power supply is controlled to increase the output of the microwave power. When the ion engine reaches a stable discharge state after a predetermined time has elapsed, the attenuation amount of the attenuator is increased to the microwave power amplifier circuit. Reduced control the output of the microwave power, characterized in that the power control can to lower the output of the microwave power in the ion engine.

  In order to solve the above-mentioned problem, the present invention described in claim 3 is a power-up circuit for starting a microwave power source for a small-sized low power consumption ion engine according to claim 2, wherein the attenuation amount of the attenuator is set to a steady state. And a control circuit that can adjust the time to be made smaller.

  According to the start-up power-up circuit of the microwave power source for the small-sized and low-power ion engine according to the present invention, by increasing the output of the microwave power only for a predetermined short time at the initial ignition at the start-up of the ion engine. Proper ionization (plasmaization) of the propellant can be started, and in a steady operation state where the ion engine is in a stable discharge state (plasma state), the attenuation rate of the attenuator is increased to increase the micro By reducing the output of the wave power, there is an effect that the power consumption of the ion engine during steady state can be significantly suppressed.

  In addition, even in a small and low power ion engine, plasma ignition due to ionization of the propellant is surely generated when the engine is started, and after that, when the steady acceleration phase is reached, the desired microwave output with power saving can be achieved with the desired microwave output. There is an effect that the engine thrust can be continuously maintained.

1 is a system configuration diagram showing a configuration of a small low power consumption ion engine incorporating a startup power-up circuit of a microwave power source for a small low power consumption ion engine according to an embodiment of the present invention. FIG. It is a figure which shows the relationship between the microwave output of a microwave power supply, and the operation | movement phase of a small power consumption ion engine. It is a block diagram which shows the basic composition of the conventional ion engine.

  Hereinafter, the configuration and operation of the startup power-up circuit of the microwave power source for a small-sized and low-power-consumption ion engine according to the present invention will be described with reference to a preferred embodiment in a small-sized and low-power-consumption ion engine system incorporating the circuit. This will be described with reference to FIG. FIG. 1 is a system configuration diagram showing in detail the configuration of a small low power consumption ion engine incorporating a power-up circuit at startup of a microwave power source for a small low power consumption 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.

  First, as shown in FIG. 1, a small and low power consumption ion engine 1 (hereinafter simply referred to as “ion engine 1”) propulsion that stores a propellant such as xenon gas under a high pressure of about 7 Mpa, for example. A propellant storage tank 11 and a low-pressure tank 13 for storing the propellant under a low pressure of, for example, 0.03 Mpa, and a pipe 17 between the propellant storage tank 11 and the low-pressure tank 13 is used for pressure adjustment. A valve 15 is arranged. 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 restrictor 18, and the propellant supply on / off control is executed by opening and closing the thruster valve 19. Further, the ion engine 1 includes a microwave power supply 30 that supplies microwave power to the plasma generation chamber 3 a of the ion source 3 and the plasma generation chamber 5 a of the neutralizer 5, and is further output from the microwave power supply 30. A two-distributor 37 that distributes the microwave power to two systems is provided. The microwave power distributed by the two distributors 37 is sent to matching isolators 38a and 38b, respectively, and these isolators 38a and 38b are respectively supplied to the ion source 3 and the neutralizer 5 of the ion engine 1 to predetermined output levels. It is configured to supply amplified microwave power. The operation of the pressure regulating valve 15, the flow restrictor 18, the thruster valve 19, the dielectric oscillation circuit 31 and the attenuation control circuit 34 to be described later is controlled by the controller 50.

  Next, the microwave power source 30 which is the main part of the present invention and the output of the microwave power at the time of engine start-up provided in the microwave power source 30 are powered up, and the microwave output is output in the steady acceleration phase. The power-up circuit of the microwave power source that can reduce the above will be described in detail below.

  The aforementioned microwave power supply 30 generally includes a microwave oscillation circuit unit 30a that generates a microwave, an attenuator 33 that attenuates the microwave output from the microwave oscillation circuit unit 30a to an appropriate signal level, and an attenuation. The microwave amplifying circuit unit 30b amplifies the output from the device 33 to a predetermined output. The microwave oscillating circuit unit 30 a includes a dielectric oscillating circuit 31 that generates a fundamental frequency microwave and a buffer amplifier 32 that stabilizes the oscillating frequency of the dielectric oscillating circuit 31. The attenuator 33 is provided with an attenuation amount control circuit 34 that enables the attenuation amount to be controlled. As the attenuator 33, for example, a 6-bit digital attenuator is used. The microwave amplifier circuit unit 30b includes a preamplifier 35 and a final amplifier 36.

  The microwave oscillated by the dielectric oscillation circuit 31 is attenuated to a predetermined level by the attenuator 33 while the oscillation frequency is stabilized by the buffer amplifier 32. At this time, when the attenuator 33 is started, that is, when the supply of microwave power to the plasma generation chamber 3a of the ion source 3 and the plasma generation chamber 5a of the neutralizer 5 is started, the attenuation amount is controlled by the attenuation amount control circuit 34. Control is made to be smaller than a predetermined steady-state attenuation. Specifically, when the attenuator 33 is activated, the attenuation amount control circuit 34 maintains, for example, a “Hi” level at a TTL (transistor-transistor logic) level, and shifts to a “Low” level after a predetermined time has elapsed. The attenuator 33 is controlled. The transition time from “Hi” to “Low” can be selected in the range of several tens of milliseconds to several seconds. For example, the attenuator 33 is turned on / off by turning on / off the collector current with an integrating circuit inserted in the base of the transistor circuit. Control the bits of As a result, it is possible to set in advance the time until plasma ignition is reliably performed and the plasma state becomes stable and stable. In this way, by controlling the attenuator 33, sufficient power is supplied to generate plasma when the ion engine 1 is started up to ensure reliable plasma ignition, and the micro that is supplied after shifting to a stable discharge state. Since wave power is reduced, power consumption is suppressed.

  Referring again to FIG. 1, the propellant such as xenon gas filled in the propellant tank 11 as described above is connected to the plasma generation chamber 3 a of the ion source 3 and the plasma generation chamber 5 a of the neutralizer 5. 17 is supplied to the plasma generation chamber 3a and the plasma generation chamber 5a by impinging the propellant supplied to the plasma generation chamber 3a and the plasma generation chamber 5a with microwaves having a predetermined output through the isolators 38a and 38b. Or plasmatization is performed.

In the ion source 3, a propellant, for example, xenon ions, converted into plasma in the acceleration region is accelerated and ejected as an ion beam through the screen grids 4a and 4b. The reaction force of this xenon ion injection is used as the ion engine output. On the other hand, the neutralizer 5 injects electrons “e ⁻ ” generated by collecting and removing xenon ions. Thus, the xenon ions ejected from the ion source 3 are electrically neutralized by the electron beam ejected from the neutralizer 5 to prevent the satellite side from being negatively charged.

Next, the relationship between the microwave output of the microwave power source provided with the power-up circuit and the operation phase of the small power consumption ion engine will be described. When the power level of the microwave output from the final stage microwave amplifying circuit section 30b in FIG. 1 and input to the two distributor 37 is indicated as “A” as shown in the figure, this power level is indicated in the present invention. “A” is controlled as shown in FIG. That is, when attention is focused on the plasma generation performed in the ion source 3 of the ion engine 1, the isolator 38a is connected from the two distributors 37 so that the plasma ignition is surely performed during the ion engine startup phase, that is, when the ion engine 1 is ignited. The power level “A” of the microwave output that is input thereafter is maintained at a high level. When the timing for the ion engine 1 to enter the steady acceleration phase (steady state) through the start phase state is reached, the power level “A” of the microwave output input to the ion source 3 through the isolator 38a. 2 through the action of both the attenuator 33 and the attenuation control circuit 34 connected to the attenuator 33 to the power level most suitable for the operating state of the ion engine 1 operating in its steady acceleration phase, as shown in FIG. It is to reduce. At this time, it is preferable that the time t ₁ shown in FIG. 2 is selected and set in the time range from several tens of milliseconds to several seconds at the time of entering the steady acceleration phase from the starting phase of the ion engine 1. Thus, it can be selected and set using a command signal from the controller 50.

  That is, at the time of ignition by the initial ionization of the propellant, the power level “A” of the microwave output is increased through the amplification action of the microwave amplification circuit unit 30b, and after a predetermined and set time range from the initial ignition timing, When the steady acceleration phase in which the ionization of the propellant in the ion engine 1 is stabilized is reached, the microwave power level “A” is lowered from the ignition level at the start. As a result, the microwave output is maintained in a reduced state except at the time of initial engine start, and the operation of the ion engine is stably and continuously maintained, so that the power consumption by the microwave output can be sufficiently reduced. It becomes possible.

In order to select and set the time t ₁ shown in FIG. 2 from the initial ion engine start phase to the steady acceleration phase in the time range from several tens of milliseconds to several seconds, according to an input command from the controller 50. When controlling the attenuation amount of the attenuator 33 via the activated attenuation amount control circuit 34, the collector current is turned ON / OFF by the transistor circuit and the integration circuit inserted in the base of the transistor circuit in the attenuation amount control circuit 34. It can be configured such that the OFF control is performed, thereby controlling the bit of the attenuator 33 to reduce or increase the attenuation amount of the attenuator 33.

That is, at the time of initial ion ignition of the ion engine 1, the attenuation amount of the attenuator 33 is maintained at “Hi” at the TTL level so that the attenuation amount is lower than the attenuation amount in the steady operation state of the ion engine determined in advance. If a microwave with such reduced attenuation is output from the output terminal of the attenuator 33 and then amplified by the microwave amplifier circuit unit 30b, a large microwave output can be secured at the time of initial ion ignition. it can. Then, after the above-described predetermined time (selected time t ₁ between several tens of milliseconds to several seconds shown in FIG. 2), the attenuation amount of the attenuator 33 is changed to the attenuation amount in the steady operation state of the ion engine, that is, If the attenuation level is recovered and increased by returning to the “Low” level, the microwave output to the microwave amplification circuit section at the next stage is reduced as compared with the initial ion ignition, and the ion source 3 and the medium of the ion engine 1 are reduced. The microwave power sent to the summer 5 (see FIG. 1) is reduced. Thereby, the microwave power source 30 capable of reducing power consumption in the ion engine 1 is realized.

  As described above, according to the present invention, since a power-up circuit capable of controlling the output increase is provided in the microwave power source for converting the propellant into plasma in a small low power consumption type ion engine, it is small or ultra-small. The power consumption of low-power ion engines mounted on satellites and space probes can be reduced, and the life and stability of the ion engines themselves can be extended, resulting in a compact or ultra-compact power balance. Even in an artificial satellite, a desired achievement mission or mission execution can be further ensured, and reliability in mission execution can be further improved.

DESCRIPTION OF SYMBOLS 1 Small low power consumption ion engine 3 Ion source 4 Ion acceleration part 5 Neutralizer 7 Power supply unit 10 Plasma ignition gas supply system 11 Propellant tank 13 Low pressure tank 15 Pressure regulating valve 17 Pipe 18 Flow restrictor 19 Thruster valve 30 Micro Wave power source 30a Microwave oscillation circuit section 30b Microwave amplification circuit section 31 Dielectric oscillation circuit 32 Buffer amplifier 33 Attenuator 34 Attenuation amount control circuit 35 Preamplifier 36 Final stage amplifier 37 2 Distribution circuit 50 Controller

Claims (3)

A microwave oscillation circuit for generating microwaves;
Control for controlling the attenuation amount from the start of the attenuator for attenuating the microwave output from the microwave oscillation circuit unit to an appropriate signal level to a predetermined time to be smaller than the attenuation amount at the steady state Circuit,
A power-up circuit at startup of a microwave power source for a small, low-power ion engine, characterized by comprising:   An attenuator for attenuating the microwave output from the microwave oscillation circuit unit provided in the previous stage of the microwave power source for generating the microwave power for plasmaizing the propellant to an appropriate signal level, and An attenuation control circuit connected to the attenuator and capable of controlling the attenuation by Hi / Low of the bit in the attenuator is provided, and when the ion engine is started, the attenuation of the attenuator is reduced to thereby terminate the microwave power source. When the input to the microwave power amplifier circuit provided in the stage is increased to increase the output of the microwave power, and the ion engine reaches a stable discharge state after a predetermined time has elapsed since the start of the attenuator In the ion engine, the output of the microwave power to the microwave power amplifier circuit is controlled to decrease by increasing the attenuation amount of the attenuator. Definitive microwave power power controllable and starts at power-up circuit of the microwave power source for small low-power ion engine, wherein the to lower the output. In the power-up circuit at the time of starting of the microwave power source for the small-sized and low power consumption ion engine according to claim 2,
A start-up power-up circuit for a microwave power source for a small, low-power ion engine, comprising a control circuit capable of adjusting a time during which the amount of attenuation of the attenuator is smaller than that during normal operation.

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