Hall effect propulsion system and method for controlling its electrical supply

Abstract

Hall effect propulsion system and method for controlling its power supply. Hall effect propulsion system comprising a Hall effect thruster (10), a cathode (40), and a power supply (80) including a motor power supply (81) providing a motor discharge current (Id) to the cathode (40) which creates a motor discharge (DM) in a gas contained in the Hall effect thruster (10), and a secondary power supply (82) providing a secondary discharge current (Ik) to the cathode (40). The Hall effect propulsion system includes means (90) for controlling the power supply (80) configured to control the supply of a secondary discharge current (Ik) by the secondary power supply (82) to the cathode (40) in order to maintain the cathode (40) at a minimum operating temperature between two activations of the motor power supply (81). Figure for the abstract: Fig. 1.

Description

Title of the invention: Hall effect propulsion system and method for controlling its electrical power supply technical field

[0001] The present invention relates to the field of satellite propulsion. More particularly, it relates to the use of Hall effect propulsion to perform orbital rendezvous maneuvers. Previous technique

[0002] Orbital satellite rendezvous are delicate maneuvers that require precise propulsion control. In particular, the propulsion system must be able to rapidly modulate the satellite's thrust.

[0003] There are systems that use a chemical propellant in pulsed mode, such as Monergol N2H4 or Diergols MMH / N2O4. These propulsion systems are massive, consume a lot of fuel, and do not allow for fine characterization of the thrust.

[0004] Other propulsion systems are based on pulsed plasma thruster technology. These propulsion systems provide precise, pulsed thrust but do not deliver significant thrust over a long period and consume a lot of fuel.

[0005] A Hall-effect thruster consumes significantly less fuel. However, such an electric thruster is generally not considered for orbital rendezvous maneuvers due to its significant reaction time in its known use, which limits its responsiveness. In particular, starting a Hall-effect thruster involves a thermalization delay, that is, a cathode preheating delay that prevents any reactive use of the Hall-effect thruster.

[0006] It would therefore be desirable to have a solution enabling the use of a Hall-effect thruster adapted to the needs of orbital rendezvous maneuvers of satellites. In particular, a means is sought to make the electric Hall-effect propulsion sufficiently versatile and available to create a significant variation in thrust, without risking a shutdown or excessively lengthening the restart time during the final approach phase of an orbital rendezvous, especially if the cathode is not in the appropriate thermal and fluid supply conditions. Description of the invention

[0007] To this end, the present invention proposes a Hall effect propulsion system comprising a Hall effect thruster, a cathode, and a power supply comprising a motor power supply providing a motor discharge current to the cathode, which creates a motor discharge in a gas contained within the Hall effect propellant, and a secondary power supply providing a secondary discharge current to the cathode, characterized in that it comprises means for controlling the power supply configured to control the provision of a secondary discharge current by the secondary power supply to the cathode in order to maintain the cathode at a minimum operating temperature between two activations of the motor power supply. The "minimum operating temperature" is understood to be the minimum temperature at which the cathode is able to release a flow of electrons.

[0008] The invention thus proposes a Hall-effect propulsion system adapted to the needs of orbital rendezvous maneuvers for satellites. Indeed, the invention makes electric Hall-effect propulsion sufficiently versatile and available to create a significant thrust variation without a long restart delay. More specifically, the means for controlling the electrical power supply not only make it possible to keep the cathode constantly active, in other words, in temperature conditions allowing for the maintenance of propulsion or a resumption of propulsion at any time, but also to vary the thrust provided by the Hall-effect thruster over a range from 2% to 100% of the nominal thrust value.

[0009] According to a particular feature, the power supply control means include a secondary discharge current control device configured to regulate the secondary power supply to a current equal to the discharge maintenance value in the cathode when the propulsion system is in standby mode. This feature makes it possible to maintain the cathode in the thermal conditions necessary for propulsion, so that its activation is not delayed by a thermalization delay.

[0010] According to a particular feature, the secondary discharge current control device provides a command to increase the secondary discharge current to the secondary supply when said secondary discharge current oscillates with a time period greater than 1 second. This feature makes it possible to maintain the secondary discharge current at a value that ensures continued discharge in the cathode.

[0011] The discharge thus maintained in the cathode makes it possible to ionize part of the gas flow to maintain an adequate temperature and thus remain in conditions allowing a resumption of propulsion at any time, the valve being kept open during standby mode in order to maintain the gas flow.

[0012] According to a particular feature, the secondary discharge current control device provides a command to increase the discharge current to the secondary supply when the absolute variation of the cathode reference voltage over 10 to 20 seconds exceeds 10%. This feature makes it possible to maintain the secondary discharge current at the discharge maintenance value in the cathode.

[0013] According to a particular feature, the means for controlling the power supply are further configured to, in a propulsion mode, activate the motor power supply and deactivate the secondary power supply, and, in a standby mode, deactivate the motor power supply and activate the secondary power supply.

[0014] According to a particular feature, the power supply control means are further configured to ensure the transition from propulsion mode to standby mode by activating the secondary power supply while the motor power supply is active, and then deactivating the motor power supply when the motor discharge current is below a threshold motor discharge current. This feature allows for a rapid variation of the thrust provided by the Hall effect thruster, from a high thrust regime, on the order of 70% to 100% of the nominal value, to a very low thrust regime, on the order of 2% of the nominal value.

[0015] According to a particular feature, the power supply control means are configured to ensure the transition from standby mode to propulsion mode by activating the motor power supply while the secondary power supply is active, and then deactivating the secondary power supply when the motor discharge current is greater than twice the threshold discharge current. This feature allows for a rapid variation of the thrust provided by the Hall effect thruster, from a very low thrust regime, on the order of 2% of the nominal value, to a high thrust regime, on the order of 70% to 100% of the nominal value.

[0016] According to a particular feature, the power supply control means are configured to keep the engine power supply and the secondary power supply active simultaneously for a time delay of less than 1 second during the transition phases between propulsion and standby modes. This feature prevents cathode overheating.

[0017] The invention also relates to a satellite comprising at least one Hall effect propulsion system according to one of the preceding particular characteristics.

[0018] The invention further relates to a method for controlling the power supply of a Hall effect propulsion system, the Hall effect propulsion system comprising a Hall effect thruster, a cathode, and a power supply including a motor supply providing a motor discharge current to the cathode which makes it possible to create a motor discharge in a gas contained in the Hall effect thruster, and a secondary power supply providing a secondary discharge current to the cathode, characterized in that the method comprises, between two activations of the motor power supply, a control of a supply of a secondary discharge current by the secondary power supply to the cathode to maintain the cathode at a minimum operating temperature.

[0019] According to a particular feature of the control method of the invention, said method includes a control of the secondary power supply to a current equal to the discharge maintenance value in the cathode when the Hall effect propulsion system is in standby mode.

[0020] According to a particular feature of the control method of the invention, said method comprises delivering to the secondary supply a command to increase the secondary discharge current when said secondary discharge current oscillates over a time period greater than 1 second.

[0021] According to a particular feature of the control method of the invention, said method includes, in a propulsion mode, an activation of the motor power supply and a deactivation of the secondary power supply, and, in a standby mode, a deactivation of the motor power supply and an activation of the secondary power supply.

[0022] According to a particular feature of the control method of the invention, the transition from propulsion mode to standby mode includes an activation of the secondary power supply while the motor power supply is active, then a deactivation of the motor power supply when the motor discharge current is less than a threshold motor discharge current.

[0023] According to a particular feature of the control method of the invention, the transition from standby mode to propulsion mode includes an activation of the motor power supply while the secondary power supply is active, then a deactivation of the secondary power supply when the motor discharge current is greater than twice the threshold discharge current.

[0024] According to a particular feature of the control method of the invention, the motor power supply and the secondary power supply are kept active at the same time for a time delay of less than 1 second during the transition phases between propulsion and standby modes. Brief description of the drawings

[0025] [Fig-1] Fig. 1 is a diagram of the architecture of a propulsion system Hall effect.

[0026] [Fig.2] Fig.2 is a flowchart of the power supply control process electric of a Hall effect propulsion system according to an embodiment of the invention.

[0027] [Fig. 3] Figure 3 is a graph showing different propulsion regimes of the Hall effect propulsion system according to one embodiment of the invention. Description of embodiments

[0028] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0029] Fig. 1 schematically illustrates a Hall effect propulsion system comprising a Hall effect thruster 10 and a cathode 40. The Hall effect thruster 10 is a thruster using a neutral gas type propellant which is supplied from a tank 1 by a pressure regulating block PRG and a flow regulating block RDX.

[0030] The pressure control block PRG comprises a valve 6, a restrictor 7, and a volume 2 whose pressure is regulated by actuation of the valve 6. The restrictor 7 is fluidly connected between the valve 6 and said pressure-regulated volume 2, and the valve 6 is fluidly coupled directly to the reservoir 1 via a conduit 51. The pressure control block PRG further comprises a pressure sensor 54 coupled to the pressure-regulated volume 2 and a control unit 53 coupled to the various elements of the pressure control block PRG, in particular to regulate the pressure inside the volume 2 by controlling the valve 6.

[0031] The RDX flow control block comprises three valves VI, V3, and V4, a flow regulator 52, and two restrictors 3 and 4, each mounted on a separate conduit. The RDX flow control block thus includes, at its inlet, a first valve VI fluidically connected between the outlet of the pressure control block PRG and the inlet of the flow regulator 52. The RDX flow control block includes two conduits coupled to the outlet of the flow regulator 52. The first conduit is connected between the flow regulator 52 and the Hall effect thruster 10, and the second conduit is connected between the flow regulator 52 and the cathode 40. A first restrictor 4 and a second valve V3 are mounted on the first conduit. The first restrictor 4 is coupled between the outlet of the flow regulator 52 and the second valve V3 of the RDX flow control block, this second valve V3 being coupled at its outlet to the Hall effect thruster 10.On the second conduit is mounted a second restrictor 3 and a third valve V4. The second restrictor 3 is coupled between the outlet of the flow regulator 52 and the third valve V4 of the flow regulation block RDX, this third valve V4 being coupled at the output to the cathode 40.

[0032] The Hall effect thruster 10 is further powered by an electrical power supply 80 comprising a motor power supply 81, a secondary power supply 82 and a preheating power supply 83. The motor power supply 81 is configured to provide A motor discharge current Id is applied to the cathode 40, creating a motor discharge DM in a gas contained within the Hall effect propellant 10. The secondary power supply 82 is configured to provide a secondary discharge current Ik to the cathode 40, maintaining the cathode 40 at a minimum operating temperature. The secondary discharge current Ik is typically between 2 and 5 A. The preheating power supply 83 is configured to supply a heater 42, preheating the cathode 40 during its startup.

[0033] The Hall effect propulsion system according to the invention further comprises means 90 for controlling the power supply 80, the control means 90 being able to be formed from logic modules embedded in a microcontroller or microprocessor, or from electronic modules. The control means 90 are configured to control, in particular, the motor power supply 81, the secondary power supply 82, and the preheating power supply 83 to provide the currents necessary for the operation of the cathode 40 in its various operating modes.

[0034] In an ignition mode of the Hall effect thruster 10, the control means 90 are configured to activate the preheating power supply 83 to start the heater 42 of the cathode 40, and thus prepare the cathode for its use to start the Hall effect thruster 10. In this ignition mode, the control means 90 are also configured to control the secondary power supply 82 to generate voltage pulses on an electrode 44 in order to ignite the cathode through an electron emitter 46 by creating a DA discharge.

[0035] In a propulsion mode, the control means 90 are configured to activate the engine power supply 81 and deactivate the secondary power supply 82, the preheating power supply 83 being kept deactivated.

[0036] In standby mode, the control means 90 are configured to deactivate the motor power supply 81 and activate the secondary power supply 82, with the preheating power supply 83 remaining deactivated. During the transition from propulsion mode 211 to standby mode 212, the control means 90 initially activate the secondary power supply 82 while the motor power supply 81 is active. Then, the control means 90 deactivate the motor power supply 81 as soon as the motor discharge current Id is less than a threshold discharge current. During the transition from standby mode 212 to propulsion mode 211, the control means 90 initially activate the motor power supply 81 while the secondary power supply 82 is active. Then, the control means 90 deactivate the secondary power supply 82 when the motor discharge current Id is greater than twice the threshold discharge current.Furthermore, in a . Example of implementation, the means 90 for controlling the electrical supply 80 are configured to keep the motor supply 81 and the secondary supply 82 active at the same time for a time delay of less than 1 second during the transition phases between propulsion and standby modes.

[0037] In standby mode 212, the Hall effect thruster provides low thrust, on the order of 2% of the nominal value, mainly due to residual thrust resulting from exhaust gas because valve 6 is not closed. In propulsion mode 211, the Hall effect thruster provides high thrust, on the order of 70% to 100% of the nominal value.

[0038] The means 90 for controlling the power supply 80 include a control device for the secondary discharge current Ik. The control device is active when the Hall-effect propulsion system is in standby mode 212. The control device regulates the secondary power supply 82 so that the intensity of the secondary discharge current is sufficient at all times for the rapid activation of the cathode 40, which is then not delayed by a thermalization delay. The control device allows for a rapid transition from standby mode 212 to propulsion mode 211.

[0039] In standby mode 212, a command to increase the secondary discharge current Ik is provided by the secondary power supply control system 10 as soon as the cathode 40 is not in an activation condition without thermalization delay. The cathode activation condition implies that the cathode is thermally stable.

[0040] The stability of the intensity of the secondary discharge current Ik is an indicator of the thermal stabilization of the cathode 40. In one example embodiment, the setpoint to increase the secondary current Ik is applied when the latter oscillates with a time period greater than 1 second.

[0041] The temporal variation of the cathode reference voltage 40 is also an indicator of the thermal stabilization of the cathode 40: a decrease in cathode temperature induces an increase in the cathode reference voltage, and an increase in cathode temperature induces a decrease in the cathode reference voltage. The cathode reference voltage 40 is typically between -5V and -35V. In one embodiment, the setpoint to increase the secondary current Ik is applied when the absolute variation of the cathode reference voltage over 10 to 20 seconds is greater than 10%.

[0042] Figure 2 presents a logic diagram of the method for controlling the electrical supply of a Hall effect propulsion system according to an embodiment of the invention.

[0043] During the start-up 200 of the Hall effect propulsion system, the cathode 40 is preheated using a heater 42 and the power supply 83. Fluid is supplied by opening valve 6 of the pressure regulating block PRG and the pressure regulator 2, and by opening valves VI, V3, V4 of the flow regulating block RDX and the flow regulator 52. The distribution of the flow towards the anode of the Hall effect propellant 10 and towards the cathode 40 is achieved by means of restrictors 3 and 4. Voltage pulses are also created on the electrode 44 by the secondary power supply 82 to ignite the cathode through the electron emitter 46 by creating the discharge DA.

[0044] Following the start-up step 200, the Hall effect propulsion system can perform ON / quasi-OFF thrust modulation cycles 210. First, in propulsion mode 211, the DA discharge is maintained by the power supply 82, which switches to current supply. The electrical voltage supply 81 creates a DM discharge in the gas. The acceleration of the ions under a discharge voltage enables thrust through electron / ion dissociation and a radial magnetic field that forces the lighter electrons to transfer their energy as Hall currents in the magnetic circuit of the Hall effect thruster 10. In propulsion mode 211, the thrust delivered by the Hall effect thruster 10 is modulated by the voltage applied to it. Propulsion mode 211 allows for rapid thrust variation, which is, however, limited to a narrow operating range, on the order of 70% to 100% of the nominal value.The propulsion mode 211 can be followed by the standby mode 212, which allows a rapid reduction of the thrust supplied to a very low level, on the order of 2% of the nominal value. From standby mode 212, the motor can be quickly restarted by energizing the anode. The transition time from standby mode to propulsion mode is determined by the transmission time of commands by the PPU and the OBC, on the order of a second. The alternation between propulsion mode 211 and standby mode 212 thus allows for a rapid variation of the thrust supplied by the Hall effect thruster 10, over a wide operating range, as illustrated in [Fig. 3].

[0045] Figure 3 represents the evolution of the thrust, as a percentage of the nominal value, for three propulsion regimes.

[0046] In a single propulsion mode regime A, the Hall effect propulsion system 10 remains in the propulsion mode 211 where the thrust is modulated by voltage modulation of the Hall effect propellant 10. The single propulsion regime A, is the typical operating regime of known Hall effect propulsion systems.

[0047] In a single standby mode regime B, the Hall effect propulsion system 10 remains in standby mode 212 where the thrust remains at a minimum value of around 2% of the nominal value (residual thrust).

[0048] In the ON / quasi-OFF propulsion mode C, the Hall effect propulsion system 10 rapidly alternates between the propulsion mode 211 and the standby mode 212. The ON / quasi-OFF propulsion mode C is particularly suited to the needs of orbital rendezvous maneuvers of satellites. Returning to zero thrust, i.e., 0%, would imply a shutdown of the gas flow via the closure of valve 6, and therefore a cooling of the cathode, which would necessitate a "long" sequence (typically 3 minutes) of reignition involving preheating the cathode to reignite it and return to standby or propulsion mode.

Claims

Demands

1. A Hall effect propulsion system comprising a Hall effect thruster (10), a cathode (40), and a power supply (80) including a motor power supply (81) providing a motor discharge current (Id) to the cathode (40) which creates a motor discharge (DM) in a gas contained in the Hall effect thruster (10), and a secondary power supply (82) providing a secondary discharge current (Ik) to the cathode (40), characterized in that it includes means (90) for controlling the power supply (80) configured to control the supply of a secondary discharge current (Ik) by the secondary power supply (82) to the cathode (40) in order to, between two activations of the motor power supply (81), maintain the cathode (40) at a minimum operating temperature.

2. Hall effect propulsion system according to claim 1, wherein the means (90) for controlling the power supply (80) include a secondary discharge current (Ik) control device configured to regulate the secondary supply to a current equal to the discharge holding value in the cathode (Ikl) when the Hall effect propulsion system is in standby mode (212).

3. Hall effect propulsion system according to claim 2, wherein the secondary discharge current (Ik) control device provides a secondary discharge current (Ik) increase command to the secondary supply (82) when said secondary discharge current (Ik) oscillates with a time period greater than 1 second.

4. Hall effect propulsion system according to any one of claims 1 to 3, wherein the means (90) for controlling the power supply (80) are further configured to, in a propulsion mode (211), activate the motor power supply (81) and deactivate the secondary power supply (82), and, in a standby mode (212), deactivate the motor power supply (81) and activate the secondary power supply (82).

5. A Hall-effect propulsion system according to claim 4, wherein the means (90) for controlling the power supply (80) are further configured to ensure the transition of the mode propulsion (211) to standby mode (212) by activating the secondary power supply (82) while the motor power supply (81) is active, then deactivating the motor power supply (81) when the motor discharge current (Id) is less than a threshold motor discharge current.

6. Hall effect propulsion system according to any one of claims 4 or 5, wherein the means (90) for controlling the power supply (80) are configured to ensure the transition from standby mode (212) to propulsion mode (211) by activating the motor power supply (81) while the secondary power supply (82) is active, and then deactivating the secondary power supply (82) when the motor discharge current (Id) is greater than the threshold discharge current.

7. Satellite comprising at least one Hall effect propulsion system according to any one of claims 1 to 6.

8. Method of controlling the power supply of a Hall effect propulsion system, the Hall effect propulsion system comprising a Hall effect thruster (10), a cathode (40), and a power supply (80) comprising a motor power supply (81) providing a motor discharge current (Id) to the cathode (40) which makes it possible to create a motor discharge (DM) in a gas contained in the Hall effect thruster (10), and a secondary power supply (82) providing a secondary discharge current (Ik) to the cathode (40), characterized in that the method comprises, between two activations of the motor power supply (81), a control of a supply of a secondary discharge current (Ik) by the secondary power supply (82) to the cathode (40) to maintain the cathode (40) at a minimum operating temperature.

9. A control method according to claim 8, comprising a control of the secondary supply to a current equal to the discharge maintenance value in the cathode (Ikl) when the Hall effect propulsion system is in standby mode (212).

10. A control method according to claim 9, comprising delivering to the secondary supply (82) a command to increase the secondary discharge current (Ik) when said secondary discharge current (Ik) oscillates with a time period greater than 1 second.

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