JP7171699B2 - Field emission propulsion system and method of calibration and operation thereof - Google Patents

Description

The present invention relates to field emission propulsion for spacecraft. Further, the present invention relates to a method of operating field emission propulsion.

A number of different propulsion techniques are known for spacecraft, such as chemical propulsion, cold gas propulsion, gas ion propulsion, and plasma propulsion. These propulsion technologies are disadvantageous in that they cannot be sufficiently miniaturized for small satellites for physical or efficiency reasons. However, as the use of microsatellites increases, the need arises to provide suitable propulsion technology with high efficiency. Specifically, field emission propulsion is particularly suitable for use in microsatellites because of its very high specific impulse of several thousand seconds.

As an example, Non-Patent Document 1 discloses field emission propulsion using a liquid metal ion source with multiple liquid metal ion emitters. Since only one extraction electrode, which is common to all liquid metal ion emitters, is used, individual emitters cannot be individually controlled.

Furthermore, due to manufacturing tolerances, individual emitters do not fire simultaneously, but in an uncontrolled sequence. In addition, each liquid metal ion emitter has an individual emission behavior such that the electric field device of that liquid metal ion emitter typically produces an unpredictable thrust vector.

In addition, Non-Patent Document 2 discloses a field emission propulsion system for microsatellites.

AMR Propulsions Innovations, "IFM Nano Thruster", Data Sheet, July 26, 2017, http://www.propulsion.at Bock, D., Tajmar, M., "Highly Miniaturized FEEP Propulsion System (NanoFEEP) for CubeSat Attitude and Orbit Control (NanoFEEP) for Attitude and Orbit Control of CubeSats", Proceedings of the 67th International Astronautical Congress (IAC), IAC-16-C4.6.5, 26-30 September 2016, Guadalajara, Mexico

SUMMARY OF THE INVENTION It is an object of the present invention to provide a field emission propulsion system and method of operation suitable for microsatellite use, achieving high efficiency and operating with low losses. In addition, a variable range of thrust over several orders of magnitude is required. It is another object of the present invention to control the firing sequence to compensate for varying thrust vectors or to allow active control of the thrust vector in order to allow controlled operation of the propulsion system. is.

These objects are achieved by a method of operating a field emission propulsion system according to claim 1, a method of calibrating a field emission propulsion system and a method of operating a field emission propulsion system according to the dependent claims.

Other embodiments are described in the dependent claims.

According to one embodiment, a field emission propulsion system for a spacecraft is provided, the field emission propulsion system comprising:
a control unit;
A propulsion assembly having a plurality of field emission propulsion units, said field emission propulsion units comprising an ion source having a plurality of ion emitters and an extraction electrode associated with said ion emitters and disposed within an electric field device. a propulsion assembly comprising:
a plurality of extraction electrode voltage sources respectively assigned to the extraction electrodes for controlling the extraction electrodes with individual extraction electrode voltages by the control unit.

The field emission propulsion system described above includes an electric field device consisting of a plurality of ion emitters, each ion emitter being assigned an extraction electrode. The ion emitters can be assigned a common emitter voltage or a common emitter potential, while the extraction electrodes are isolated from each other and have individually adjustable extraction electrode voltages and individually adjustable extraction electrode potentials. Each can be controlled by an extraction electrode voltage source.

Additionally, the control unit is configured to adjust the electric field strength of the electric field between the ion emitter and the associated extraction electrode to a particular extraction electrode voltage corresponding to a predetermined ion current level. can be This particular extraction electrode voltage is determined for at least one particular propulsion unit by a calibration method that measures the current-voltage characteristics of that propulsion unit. In this calibration method, by measuring the emitter current through the ion emitter at various voltage differences between the extraction electrode and the ion emitter while simultaneously deactivating each of the other propulsion units, The current-voltage characteristics of each propulsion unit are measured and the extraction electrode voltage or potential is adjusted to produce an emitter current corresponding to a predetermined ion current level.

Thus, the calibration method described above allows individual control of the extraction electrodes of field emission propulsion units. In this method, the voltage difference between each extraction electrode and its ion emitter is varied while the current from the emitter voltage source is measured for the purpose of measuring the properties of the corresponding ion emitter. As a result, a voltage dependent ion current can be determined for each of the ion emitters, so that the desired ion current level can be specifically set by adjusting each extraction electrode voltage or each extraction electrode potential, respectively. can do. Thus, each ion emitter in the field device can be assigned the same emitter voltage (having the same emitter potential), and to adjust the ion current of each individual ion emitter, the ion The extraction electrodes assigned to the emitters can be individually controlled. Since each ion emitter is at the same potential, it can operate from the same emitter voltage source or a common potential source, thereby reducing losses in high voltage generation and reducing overall system footprint and mass. . Alternatively, the connection of the extraction electrode voltage sources to each extraction electrode to each other and to the ion emitter can be made by their positive potential terminals. Individual control of the extraction electrodes also allows for more precise adjustment of the thrust and thrust direction of the propulsion assembly.

Furthermore, a current measuring unit may be provided, arranged to measure the current flowing from one, some or all of said ion emitters and/or to said extraction electrode.

According to one embodiment, at least one of said extraction electrodes may be formed of 2, 3, 4 or 5 or more insulated extraction electrode segments, which are collectively In particular, an annular extraction electrode is formed. The extraction electrode voltage source is configured to provide individual segment voltages to the extraction electrode segments such that a predetermined direction of the emitted ion beam is adjusted during operation, and/or For the purpose of providing individual segment voltages to the electrode segments, separate segment voltage sources are provided to the extraction electrode segments such that the predetermined direction of the ion beam is adjusted during operation.

Preferably, each extraction electrode consists of a plurality of insulated extraction electrode segments, which can be controlled with different segment voltages. The level of the individual segment voltages is based on the extraction electrode voltage to be applied or the extraction electrode potential to be applied.

Specifically, the segment voltages may be either a separate segment voltage source, a voltage divider that produces segment voltages by dividing the extraction electrode voltage assigned to each extraction electrode, or an adjustable series resistor in the extraction electrode segment. can be adjusted by either

This allows compensating for possible misalignment of the resulting thrust beam during operation due to component tolerances and the like. The ability to select segment voltages that are different from each other can greatly relax the component tolerance requirements of the propulsion unit. This is because misalignment of the resulting thrust beam or geometric misalignment of the ion emitter with respect to the extraction electrode can be actively compensated for.

By repeating the above calibration process at regular intervals, undesirable changes in the ion emission behavior of individual ion emitters can be detected and compensated for if necessary during long term operation.

Additionally, a neutralizer may be provided to provide an electron current of controllable intensity.

According to one embodiment, the ion source of the propulsion assembly may comprise a fuel tank for a liquid or liquefiable electrically conductive fuel, the fuel facing each of the extraction electrodes for field ionization. It can be ejected at the tip of the ion emitter.

Preferably, said extraction electrode is annular in shape with a central opening arranged concentrically with respect to the direction of extension of said ion emitter.

According to one embodiment, the extraction electrodes may be supported and insulated from each other by an extraction plate. The extraction plate is preferably made of non-conductive material.

Further, each extraction electrode voltage source may have an adjustable voltage divider to provide an adjustable extraction electrode voltage.

Preferably, one, at least one, some or each of said extraction electrodes is a conductive first shielding structure projecting along its entire or partial perimeter in the direction of said ion emitter. and/or one, at least one or each of said extraction electrodes is a conductive A second shielding structure is provided.

The method described above is based on a field emission propulsion system with a common emitter electrode and individual extraction electrodes, where the individual extraction electrodes can be individually controlled by individual extraction potentials.

According to another aspect, there is provided a method of calibrating a field emission propulsion system as described above, wherein for each of said plurality of field emission propulsion units, an electric field between said ion emitter and said extraction electrode associated therewith. The intensity may be set to an extraction electrode voltage corresponding to a predetermined ion current to be adjusted, the extraction electrode voltage being determined by the current-voltage characteristics of the field emission propulsion unit and the corresponding ones of the plurality of propulsion units. and the predetermined ion current to be adjusted of the propulsion unit, the method comprising:
measuring current-voltage characteristics for each of said field emission propulsion units, comprising measuring emitter current through said ion emitters of said field emission propulsion units while simultaneously deactivating the remaining field emission propulsion units; measuring at various extraction electrode voltages while at or operating at a constant current;
said current-voltage characteristic and said predetermined ion current for each said field emission propulsion unit, respectively, to generate an emitter current of said respective field emission propulsion unit corresponding to said predetermined ion current to be adjusted; and setting the extraction electrode voltage according to.

According to another aspect, there is provided a method of operating the field emission propulsion system described above, wherein for each of the plurality of field emission propulsion units, the electric field between the ion emitter and the associated extraction electrode is: The intensity is adjustable to an extraction electrode voltage corresponding to a predetermined ion current to be adjusted, the extraction electrode voltage being determined by the current-voltage characteristics of the corresponding one of said plurality of field emission propulsion units and said adjustment. A predetermined thrust vector of the field emission propulsion system is derived from a predetermined ion current to be generated from each of the field emission propulsion systems such that the predetermined thrust vector results from the sum of the ion currents from the field emission propulsion units. This is done by controlling the propulsion units with individual extraction electrode voltages.

The following drawings provide detailed descriptions of various embodiments.

1 is a schematic diagram of a field emission propulsion system comprising multiple propulsion units; FIG. Fig. 3 is a cross-sectional view of propulsion units arranged side by side; FIG. 4 is a detailed cross-sectional view of the propulsion unit; 2 is a diagram of a possible arrangement of propulsion units of the propulsion system of FIG. 1; FIG. 4 is a flow chart showing a method of calibrating a propulsion unit; 4 is an example of the current-voltage characteristics of a propulsion unit; Figures 7a-7c are various perspective views of variations of the splitting of the extraction electrode.

FIG. 1 schematically shows the structure of a field emission propulsion system 1. As shown in FIG. A field emission propulsion system 1 comprises a propulsion assembly 2 , a neutralizer 3 and a control unit 4 . FIG. 2 is a detailed cross-sectional view of propulsion assembly 2 .

As shown in detail in the cross-sectional view of FIG. 2, the propulsion assembly 2 comprises a heating unit 21 for an ion source 22, the ion source 22 comprising a fuel tank 221 with fuel 223 and a and an ion emitter 222 electrically and fluidly connected to. The heating unit 21 serves to bring the fuel in the fuel tank 221 to a liquid state and keep it liquid. The heating unit 21 may be powered by and temperature controlled by a heating controller 41 as part of the control unit 4 .

Fuel tank 221 is made of a conductive material such as tantalum, rhenium, tungsten, graphite or titanium. 2 and 3, the ion emitter 222 has a needle-like, conical or pyramidal tip, in particular in shape, for field ionization from the ion emitter 222, which is shown in a detailed cross-sectional view of the propulsion unit 23 in FIGS. and a device or arrangement for pumping the electrically conductive liquid fuel 223 from the fuel tank 221 . Specifically, a fluid conduit 224 may be provided extending inwardly to the tip, the fluid conduit 224 being supplied by, for example, capillary effect, a conductive liquid for field ionization from the ion emitter 222 . Fuel is released from fuel tank 221 . Alternatively, the ion emitter 222 may be perforated with multiple channels, and the perforations are open so that the fuel 223 can be delivered to the tip of the ion emitter 222 . Ion emitter 222 may be formed of tantalum, tungsten, rhenium, titanium or other refractory or high melting point metals.

The fuel passes through the fluid line 224 of the ion emitter 222 by capillary effect. As materials for the fuel, conductive liquids or low melting point metals such as gallium, indium, bismuth, lead, gold and the like can be considered.

Above the tip of each ion emitter 222 is a respective extraction electrode 24 having a central aperture 241 substantially coaxial with the tip of the ion emitter 222 . The extraction electrodes 24 are preferably supported by an extraction plate 25 and insulated from each other by the extraction plate 25, for example formed of a non-conductive material.

Fuel tank 221 is electrically connected to ion emitter 222 and obtains a high potential from emitter voltage supply 42 . This emitter voltage supply 42 may be adjustable and sets the emitter voltage or emitter potential to a fixed value.

Each extraction electrode 24 is individually connected to a controllable extraction electrode voltage source 43 which is part of the control unit 4 . These extraction electrode voltage sources 43 are individually adjustable. This is to set the individual extraction electrode voltages and thus the individual field strengths between the ion emitter 222 and the extraction electrode 24 for each of the propulsion units 23 . As an alternative to separate extraction electrode voltage sources 43 for each of the extraction electrodes 24, a common extraction electrode voltage source 43 may be provided, with the different voltages of the extraction electrodes 24 correspondingly assigned to each. It can be set by a pressure gauge. Other options of setting individual extraction electrode voltages for each extraction electrode 24 may also be devised.

The configuration of the control unit 4 is specifically designed so that the ignition timing and level of ion emission from the individual ion emitters 222 assigned to that extraction electrode 24 can be controlled. The electrode potentials are individually controlled. Thus, individual ion emitters 222 can be turned on/off and different emission currents can be controlled for each ion emitter 222 . The potential difference between the emitter potential and the extraction potential is typically +several thousand volts.

In operation, an electron current is normally generated by the neutralizer 3 because an emitter ion current from positively charged fuel ions is emitted from the propulsion unit 23 and causes the propulsion system 1 to become negatively charged. is produced and released. The neutralizer 3 can be constructed, for example, in a manner known per se as a field emission electron source or a thermionic electron source. To this end, the control unit 4 may control and supply power to the neutralizer 3 in a manner known per se, e.g. to keep the overall charge of the propulsion system 1 as neutral as possible. A control unit 45 is provided.

FIG. 4 shows the layout of the extraction electrodes 24 in a plan view. The extraction electrodes 24 are arranged, for example, concentrically around the ion emitter 222 . At the center of the extraction electrode 24 there is a substantially circular aperture 241 arranged concentrically with the ion emitter 222 for emitting an ion beam from the ion emitter 222 . An array of extraction electrodes 24 may be provided as an electric field device, in which the extraction electrodes 24 are arranged in rows and are offset from each other to maximize placement density.

The extraction electrodes 24 are joined together on an extraction plate 25 which holds the extraction electrodes 24 in place. The extraction plate 25 may be formed of a non-conductive material, or the extraction electrode 24 may be insulated and mounted on the extraction plate 25 . One, at least one, or each of the extraction electrodes 24 comprises a conductive first shield structure 242 projecting around it towards the ion emitter 222 . This first shielding structure 242 prevents a continuous coating of fuel material deposition on the surface of the extraction plate 25 facing the ion emitter by means of the shade principle. This prevents the formation of conductive paths between the individual extraction electrodes 24 and between the electrodes and the fuel tank 221 during operation that would cause short circuits.

Alternatively or additionally, one, at least one, some or each of the extraction electrodes 24 may comprise a conductive second shield structure 245 projecting around it towards the ion beam to be emitted. This second shielding structure 245 prevents continuous fouling due to fuel material build-up on the side of the extraction plate 25 opposite to the ion emitter 222 side according to the shade principle. The second shielding structure 245 may be formed in a torus shape. This prevents the formation of conductive paths between the individual extraction electrodes 24 and between the electrodes and the fuel tank 221 during operation that would cause short circuits.

Furthermore, the extraction plate 25 may have a labyrinth-like or meandering structure, i.e., a structure protruding and/or recessed perpendicular to the surface direction of the extraction plate 25, between the extraction electrodes 24. , these structures extend along the surface direction of the drawer plate 25, thereby preventing a continuous conductive coating due to deposition of fuel material during long-term operation according to the shade principle. By way of example, the support between the heating unit 21 and the drawer plate 25 may have a corresponding labyrinthine or meandering shape or step, which again can be made continuous by providing a shade. Prevent coating.

Additionally, a conductive cover plate 27 may optionally be attached parallel to the extraction plate 25 on the side of the extraction plate 25 opposite the ion emitter side. Specifically, the cover plate 27 has a circular opening 271 above the extraction electrode 24 and positioned in the direction in which the ion emitters 222 and the extraction electrode 25 are arranged. Specifically, this circular opening 271 has a dimension (for example, radius) equal to or larger than that of the extraction electrode 25 in the surface direction of the extraction plate 25 . Cover plate 27 may be insulated from extraction electrode 24 . Insulation between the cover plate 27 and the extraction electrode 24 may be ensured by insulating spacers 28, which are also provided during long-term operation to prevent a continuous conductive coating due to deposition of fuel material. It has a labyrinthine or meandering structure. The provision of the cover plate 27 is advantageous as it prevents particles in the environment from reaching the ion emitter 222 by applying an electrical potential. Additionally, deposition of sputtered particles or bounced fuel on the upper surface of the extraction plate 25 during long term operation can be prevented.

During operation in space, cover plate 27 may prevent local environmental plasma effects on propulsion unit 23 . This prevents free/thermal electrons from, for example, the ambient plasma from being attracted to the ion emitter 222 . These electrons can damage the ion emitter. In addition, the potential of the cover plate 27 prevents such collateral electron currents from erroneously measuring the emitter current.

The control unit 4 also comprises a current measuring unit 44 for measuring the current flowing to the extraction electrode voltage source or coming from the neutralizer 3 .

In order to operate the propulsion system 1, it is desirable to set the thrust vector of the ion beam emitted from the ion emitter 222 with a uniform or defined thrust vector. Because of component and assembly tolerances, the application of the same extractor electrode voltage will produce a variety of different thrust vectors.

Accordingly, a method is provided for controlling the intensity of an ion beam in a defined manner. This method assigns ion emitters 222 and their associated ion emitters 222 by varying either the extraction electrode voltage, the extraction electrode potential, or the voltage difference between the extraction electrode 24 and its associated ion emitter 222. This is done by individually adjusting the field strength of the electric field between the extraction electrodes 24 in a defined manner. To set the extraction electrode voltage, a method is provided as shown in the flow chart of FIG.

At step S1, one of the propulsion units 23 is selected. At step S2, the current-voltage characteristic graph of the selected propulsion unit 23 is measured. This current-voltage characteristic represents the characteristic of the current passing through the voltage difference between the extraction electrode potential and the emitter potential of each corresponding propulsion unit 23, which current is set at the extraction electrode voltage of that propulsion unit 23. is generated at an electric field strength of Current-voltage characteristics are measured while the propulsion units 23 other than the object to be measured are in a non-operating state, or in a state where the propulsion units 23 are operating at a constant (known) current (that is, in an operating state). If unit 44 is running and measuring in the latter state, the ion current level measured by current measurement unit 44 will be that of all propulsion units 23 in operation. A measurement of the ion current level is made by measuring the current flowing from the emitter voltage supply 42 or the current flowing to the ion source. The ion current of the propulsion unit 23 being measured corresponds approximately to the measured current flowing into the ion source minus the known ion current of the other propulsion units 23 (i.e. the non-measuring propulsion unit 23 is in working condition). That is, if the remaining propulsion units 23 are operating at a known current, the ion current of each propulsion unit 23 can be determined by subtracting the current of the remaining propulsion unit 23 from the detected current. For each measurement, if only the propulsion unit 23 to be measured is in operation, the measured current corresponds to the ion current at the applied electric field strength or applied voltage difference between the emitter potential and the extraction electrode potential. Thus, for each propulsion unit 23 a current-voltage characteristic can be determined. FIG. 6 shows an example of such a current-voltage characteristic graph.

In step S3, it is checked whether all propulsion units 23 have completed measurement. If completed (option: yes), step S4 is continued, and if not completed, the process returns to step S1 to measure the next propulsion unit 23 that has not yet been measured. In this manner, the current-voltage characteristics are recorded for each of the propulsion units 23 .

In step S4, for each propulsion unit 23, the extraction electrode voltage is controlled to set the electric field intensity corresponding to the desired ion current intensity.

Further, referring to Figure 4 in conjunction with the various views of Figures 7a-7c, the extraction electrode 24 may be divided into segments. These extraction electrode segments 243 are insulated from each other, eg, by spacing, and form the circular extraction electrode 24 when assembled. The extraction electrode segments 243 can be arranged according to the embodiments of Figures 7a-7c, in which the extraction electrode 24 is divided into four identical extraction electrode segments 243 (see Figure 7a), two It is divided into two identical extraction electrode segments 243 (see Figure 7b) and into three extraction electrode segments 243 (see Figure 7c). By varying the segment voltage at the individual extraction electrode segments 243 of the extraction electrode 24, the asymmetry of the ion beam emitted by the ion emitter 222, i. The tilt of the beam path can be compensated for. Such asymmetry is due to propulsion unit 23 component and manufacturing tolerances.

If the extraction electrode is divided into segments, the calibration method described above can be performed by first applying to each extraction electrode segment the extraction electrode voltage required for the measurement.

Asymmetry may be determined, for example, during the calibration method described above, or in a separate procedure therefrom. For this purpose, each extraction electrode segment 243 may be provided with a separate current measurement function. Each propulsion unit 23 is measured in turn to determine the current-voltage characteristics and the parasitic current passing through each extraction electrode segment 243 at one or more specific extraction electrode voltages during ion beam formation. is measured. For example, the extraction electrode segment 243 with the highest measured current corresponds to the extraction electrode segment 243 that deflects the ion beam most strongly in that direction, and thus this extraction electrode segment 243 is positioned closest to the ion beam. there is This allows individual segment voltages to be controlled based on the desired extraction electrode voltage (or desired field strength).

By changing the segment voltage applied to some of the individual extraction electrode segments 243 of the propulsion unit 23, the direction of the ion beam can be changed while applying the extraction electrode voltage to the other extraction electrode segments 243. It can also be changed. For example, by repeatedly controlling the segment voltages on some of the extraction electrode segments 243, the direction of the ion beam can be adjusted in a desired direction, specifically parallel to the alignment direction of the ion emitters 222 and the extraction electrodes 24. direction can be adjusted. Accurately controlling the intensity of the ion beam by iteratively controlling a portion of the segment voltages based on predetermined set extraction electrode voltages and compensating for component and manufacturing tolerances of the propulsion unit 23. can also

Alternatively, all segment voltages can be altered by the adjusted extraction electrode voltage such that the average value of the individual segment voltages approximately matches the adjusted extraction electrode voltage.

As an example, control of the individual segment voltages or direction of the ion beam can be specifically performed using voltage dividers, the respective segment voltage being generated from the extraction electrode voltage. Thus, segment voltages with voltage dividers, even adjustable voltage dividers, can be generated by the extraction electrode voltage source. It is also possible to individually control each of the extraction electrode segments by individual voltage sources.

As an example, in the embodiment of FIG. 7a, if a high current is measured at one of the extraction electrode segments 243a compared to the current of the other extraction electrode segments 243, the corresponding Segment voltages can be reduced. This reduction is done by setting an adjustable series resistor or by setting an adjustable voltage divider to increase the fuel ion attraction of the ion beam by the other extraction electrode segments 243 . As a result, the ion beam is attracted towards other extraction electrode segments 243 and thus deflected away from the corresponding extraction electrode segment 243a. By appropriately calibrating the variable series resistors assigned to the extraction electrode segments 243 or the voltage dividers assigned to the extraction electrode segments 243, the propulsion unit 23 can be calibrated accordingly. In this manner, part tolerances and alignment errors of the extraction electrode 24 can be compensated for, and the accuracy of manufacturing and assembly of the extraction electrode segment 243 and the ion emitter 222 can be reduced.

The field emission propulsion system described above may operate by individually controlling the propulsion units 23 . A thrust vector control, which specifies the thrust vector, determines the ion current of the individual propulsion units 23 . Control of this individual ion current is performed by specifying the extraction electrode voltage corresponding to each ion current, and the extraction electrode voltage corresponding to the ion current is obtained from the current/voltage characteristics. Thus, not only is the total thrust intensity obtained by the sum of each ion beam, but a predetermined moment is applied to the field emission propulsion system. This moment is provided by the array of individual propulsion units and the intensity of each thrust produced by the ion beam associated with each.

1 field emission propulsion system 2 propulsion assembly 3 neutralizer 4 control unit 21 heating unit 22 ion source 23 propulsion unit 24 extraction electrode 25 extraction plate 27 cover plate 28 insulating spacer 41 heating controller 42 emitter voltage supply 43 extraction electrode Voltage source 44 Current measurement unit 45 Neutralizer control unit 221 Fuel tank 222 Ion emitter 223 Fuel 224 Fluid line 241 Extraction electrode central opening 242 First shield structure 243 Extraction electrode segment 245 Second shield structure 271 Cover plate the opening of

Claims (13)

A field emission propulsion system (1) for a spacecraft, comprising:
a control unit (4);
A propulsion assembly (2) comprising a plurality of field emission propulsion units (23), said field emission propulsion units (23) comprising a plurality of ion emitters assigned a common emitter voltage or a common emitter potential. a propulsion assembly (2) comprising an ion source having an ion emitter (222) and mutually electrically insulated extraction electrodes (24) disposed within an electric field apparatus associated with said ion emitter (222) )When,
a plurality of extraction electrode voltage sources (43) respectively assigned to said extraction electrodes (24) for controlling said extraction electrodes (24) with individually adjustable extraction electrode voltages by said control unit (4);
A field emission propulsion system (1) comprising: 2. Field emission propulsion according to claim 1, comprising a current measuring unit (44) configured to measure the current flowing from the ion emitter (222) and/or to the extraction electrode (24). system (1). The control unit (4) controls the field strength of the electric field between the ion emitter (222) and the respective associated extraction electrodes (24) with a determined extraction electrode voltage corresponding to a predetermined ion current level. configured to control the
the determined extraction electrode voltage is determined for the determined field emission propulsion unit (23) by measuring current-voltage characteristics of the field emission propulsion unit (23);
The measurement of this current-voltage characteristic was carried out by measuring the emitter current passing through the ion emitter (222) while the other field emission propulsion units (23) were simultaneously deactivated or operated at a constant current. state, by measuring at various voltages,
Field emission propulsion system (1) according to claim 1 or 2, wherein said extraction electrode voltage is set such that the emitter current of said field emission propulsion unit (23) corresponds to said predetermined ion current level. . at least one of said extraction electrodes (24) is formed of 2, 3, 4 or 5 or more extraction electrode segments (243) insulated from each other;
said extraction electrode segments (243) collectively form a particularly annular extraction electrode (24),
said extraction electrode voltage source (43) is configured to provide individual segment voltages to said extraction electrode segments (243) such that a predetermined direction of the ion beam is controlled in use, and/or
For the purpose of providing individual segment voltages to said extraction electrode segments (243), separate segment voltage sources are applied to a plurality of said extraction electrode segments (243) such that the predetermined direction of the ion beam is adjusted during use. A field emission propulsion system (1) according to any one of claims 1 to 3, provided in adjustable series resistors or adjustable voltage dividers for generating the individual segment voltages from the extraction electrode voltage assigned to each extraction electrode (24), or from another predetermined voltage; 5. A field emission propulsion system (1) according to claim 4, assigned to each part of an extraction electrode segment (243) or to each said extraction electrode segment (243). 6. A field emission propulsion system (1) according to any one of the preceding claims, wherein a neutralizer (3) is provided for outputting an electron current of controllable intensity. said propulsion assembly (2) comprising an ion source having a fuel tank (221) for a liquid or liquefiable conductive fuel (223);
7. The fuel (223) according to any one of claims 1 to 6, wherein the fuel (223) can be emitted at the tip of the ion emitter (222) facing each extraction electrode (24) for field ionization. field emission propulsion system (1). 8. Any one of claims 1 to 7, wherein said extraction electrode (24) is in particular annular in shape with a central opening arranged concentrically with respect to the direction of extension of said ion emitter (222). A field emission propulsion system (1) according to claim 1. 9. According to any one of claims 1 to 8, wherein said extraction electrodes (24) are supported and insulated from each other by extraction plates (25), said extraction plates (25) being made in particular of a non-conducting material. A field emission propulsion system (1) as described. A field emission propulsion system according to any preceding claim, wherein each extraction electrode voltage source (43) comprises an adjustable voltage divider to provide an adjustable extraction electrode voltage. (1). one, at least one or each of said extraction electrodes (24) protruding along its entire or partial perimeter in the direction of said ion emitter (222) a conductive first shield structure; (242) and/or
One, at least one or each of said extraction electrodes (24) is a conductive second electrode protruding in a direction opposite said ion emitter (222) along its entire or partial perimeter. A field emission propulsion system (1) according to any preceding claim, comprising two shielding structures (245). For each of the plurality of field emission propulsion units (23), the field strength of the electric field between the ion emitter (222) and the associated extraction electrode (24) is adjusted to a predetermined ion current to be adjusted. adjustable to a corresponding extraction electrode voltage, said extraction electrode voltage being determined by current-voltage characteristics of a corresponding one of said plurality of field emission propulsion units (23) and said predetermined ion current to be adjusted; A method of calibrating a field emission propulsion system (1) according to any one of claims 1 to 11, obtained from
measuring current-voltage characteristics for each of said field emission propulsion units (23), wherein the emitter current passing through said ion emitter (222) of said field emission propulsion unit (23) is field emission propulsion unit (23) simultaneously deactivated or operated at constant current, at different extraction electrode voltages;
said current-voltage characteristic for each of said field emission propulsion units (23), respectively, to generate an emitter current of each said field emission propulsion unit (23) corresponding to said predetermined ion current to be adjusted; and controlling the extraction electrode voltage in response to the predetermined ion current. For each of the plurality of field emission propulsion units (23), the field strength of the electric field between the ion emitter (222) and the associated extraction electrode (24) is adjusted to a predetermined ion current to be adjusted. adjustable to a corresponding extraction electrode voltage, said extraction electrode voltage being determined by current-voltage characteristics of a corresponding one of said plurality of field emission propulsion units (23) and said predetermined ion current to be adjusted; A method of operating a field emission propulsion system (1) according to any one of claims 1 to 11, obtained from
Adjustment of the predetermined thrust vector of the field emission propulsion system (1) is performed for each of the field emission propulsion units (23) such that the predetermined thrust vector results as the sum of the ion currents from the field emission propulsion units (23). ) with individual extraction electrode voltages .

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