Hall-effect propulsion system and method for controlling the supply of electrical power thereto

Abstract

Disclosed is a Hall-effect propulsion system comprising a Hall-effect thruster (10), a cathode (40), and an electrical power supply (80) including an engine power supply (81) delivering an engine discharge current (Id) to the cathode (40) allowing an engine discharge (DM) to be created in a gas contained in the Hall-effect thruster (10), and a secondary power supply (82) delivering a secondary discharge current (Ik) to the cathode (40). The Hall-effect propulsion system comprises means (90) for controlling the electrical power supply (80), which are configured to command delivery of a secondary discharge current (Ik) by the secondary power supply (82) to the cathode (40) in order to keep the cathode (40) at a minimum operating temperature between two activations of the engine power supply (81).

Description

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] Satellite orbital rendezvous are delicate maneuvers requiring 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 long periods 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 applications, which limits its responsiveness. In particular, starting a Hall-effect thruster involves a thermalization delay, meaning a preheating delay of the cathode that prevents any reactive use of the 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 for satellites. In particular, a way to make the electric propulsion with Hall effect sufficiently versatile and available to create a significant variation in effort, 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 proper 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 including a motor power supply providing a motor discharge current to the cathode which creates 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 it includes means for controlling the power supply configured to control the supply 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 means for controlling the power supply comprising a secondary discharge current control device configured to regulate the secondary supply to a current equal to the discharge holding value in the cathode when the Hall effect propulsion system is in standby mode, said secondary discharge current control device providing a secondary discharge current increase command to the secondary supply when the absolute variation of a cathode reference voltage over 10 to 20 seconds is greater than 10% or when a secondary discharge voltage oscillates over a time period greater than 1 second or drifts by a value greater than 1V / min.

[0008] The term "minimum operating temperature" refers to the minimum temperature from which the cathode is able to release a flow of electrons.

[0009] The cathode reference voltage is known as the "cathode reference potential" in English.

[0010] The secondary discharge voltage is measured across the cathode terminals.

[0011] 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 readily available to create a significant thrust variation without a lengthy restart delay. More specifically, the means of controlling the electrical power supply not only allow the cathode to remain constantly active—that is, in temperature conditions that permit sustained or resumed propulsion at any time—but also allow the thrust provided by the Hall-effect thruster to be varied over a range from 2% to 100% of the nominal thrust value.

[0012] The discharge current control device allows the cathode to be kept in the thermal conditions necessary for propulsion, so that its activation is not delayed by a thermalization delay.

[0013] The instruction to increase the secondary discharge current that the control device provides to the secondary supply, when the absolute variation of the reference voltage of the cathode for 10 to 20 seconds is greater than 10% or when a secondary discharge voltage oscillates over a time period greater than 1 second or drifts by a value greater than 1V / min, allows the secondary discharge current to be kept at a current value ensuring the maintenance of a discharge in the cathode.

[0014] 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.

[0015] Preferably, the preheating power supply is configured to power a heater enabling preheating of the cathode when the latter is started and is kept disabled between two activations of the motor power supply.

[0016] 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 discharge current The secondary winding oscillates with a period greater than 1 second. This characteristic allows the secondary discharge current to be maintained at a value that ensures continued discharge in the cathode.

[0017] According to a particular characteristic, the means of controlling the power supply are further configured to, in propulsion mode, activate the engine power supply and deactivate the secondary power supply, and, in standby mode, deactivate the engine power supply and activate the secondary power supply.

[0018] According to a specific 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 engine power supply is active, and then deactivating the engine power supply when the engine discharge current is below a threshold engine 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.

[0019] According to a specific feature, the power supply control means are configured to ensure the transition from standby mode to propulsion mode by activating the engine power supply while the secondary power supply is active, and then deactivating the secondary power supply when the engine discharge current exceeds 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.

[0020] According to a specific feature, the power supply control means are configured to maintain both 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.

[0021] The invention also relates to a satellite comprising at least one Hall effect propulsion system according to one of the preceding particular characteristics.

[0022] 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 comprising a motor power 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 in order to maintain the cathode at a minimum operating temperature,the method further comprising controlling 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, and delivering to the secondary power supply a setpoint to increase the secondary discharge current when the absolute variation of a reference cathode voltage for 10 to 20 seconds is greater than 10% or when a secondary discharge voltage oscillates over a time period greater than 1 second or drifts by a value greater than 1V / min.

[0023] 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.

[0024] According to a particular feature of the control method of the invention, said method includes 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.

[0025] According to a particular feature of the control method of the invention, said method includes, in a propulsion mode, an activation of the power supply motor and a deactivation of the secondary power supply, and, in standby mode, a deactivation of the motor power supply and an activation of the secondary power supply.

[0026] 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, and then a deactivation of the motor power supply when the motor discharge current is less than a threshold motor discharge current.

[0027] 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, and then a deactivation of the secondary power supply when the motor discharge current is greater than twice the threshold discharge current.

[0028] According to a particular feature of the control method of the invention, the engine 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

[0029] [Fig. 1] Figure 1 is a diagram of the architecture of a Hall effect propulsion system.

[0030] [Fig. 2] Figure 2 is a logic diagram of the method for controlling the electrical supply of a Hall effect propulsion system according to an embodiment of the invention.

[0031] [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 the implementation methods

[0032] 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.

[0033] Figure 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.

[0034] The PRG pressure control unit comprises a valve 6, a restrictor 7, and a pressure-regulated volume 2, which is actuation by valve 6. The restrictor 7 is fluidly connected between valve 6 and the pressure-regulated volume 2, and valve 6 is fluidly coupled directly to the reservoir 1 via a conduit 51. The PRG pressure control unit 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 PRG pressure control unit, in particular to regulate the pressure within volume 2 by controlling valve 6.

[0035] 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. On the first conduit are mounted a first restrictor 4 and a second valve V3. 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 block. RDX flow regulation, this third V4 valve being coupled at the output to cathode 40.

[0036] The Hall effect thruster 10 is further powered by a 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 to the cathode 40, which creates a motor discharge DM in a gas contained within the Hall effect thruster 10. The secondary power supply 82 is configured to provide a secondary discharge current Ik to the cathode 40, which maintains 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 power a heater 42, which preheats the cathode 40 during its startup.

[0037] 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.

[0038] 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.

[0039] In propulsion mode, the control means 90 are configured to activate the engine power supply 81 and deactivate the secondary power supply 82, with the preheating power supply 83 being kept deactivated.

[0040] In standby mode, the control means 90 are configured to deactivate the motor power supply 81 and activate the secondary power supply 82, while the preheating power supply 83 remains 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 one embodiment, the means 90 for controlling the power supply 80 are configured to keep the motor power supply 81 and the secondary power 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.

[0041] In standby mode 212, the Hall effect thruster provides low thrust, approximately 2% of its nominal value, primarily due to residual thrust from exhaust gases because valve 6 is not closed. In propulsion mode 211, the Hall effect thruster provides high thrust, approximately 70% to 100% of its nominal value.

[0042] 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 thus not delayed by a thermalization delay. The control device allows for a rapid transition from standby mode 212 to propulsion mode 211.

[0043] 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.

[0044] The temporal variation of the cathode 40 reference voltage is an indicator of the cathode 40's thermal stabilization: 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 reference voltage variation range is typically around 40V. Under satellite ground test measurement conditions, the reference voltage is typically between -5V and -35V.

[0045] The reference voltage of cathode 40 is known as the "cathode reference potential" in English.

[0046] The secondary current increase instruction Ik is applied when the absolute variation of the cathode reference voltage over 10 to 20 seconds is greater than 10%.

[0047] The temporal variation of the secondary discharge voltage is also an indicator of the thermal stabilization of cathode 40. In one embodiment, the setpoint to increase the secondary current Ik is applied when this voltage oscillates with a period greater than 1 second or drifts by a value greater than 1 V / min. The secondary discharge voltage is measured across cathode 40.

[0048] The stability of the intensity of the secondary discharge current Ik is also 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.

[0049] Figure 2 presents a logic diagram of the method for controlling the electrical power supply of a Hall effect propulsion system according to an embodiment of the invention.

[0050] 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 pressure regulator 2, and by opening valves VI, V3, V4 of the flow regulating block RDX and flow regulator 52. The distribution of the flow to the anode of the Hall effect propellant 10 and to the cathode 40 is achieved by restrictors 3 and 4. Voltage pulses are also created on the electrode 44 by the secondary power supply 82 to ignite the cathode 40 through the electron emitter 46 by creating the discharge DA.

[0051] 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 applied voltage. 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 for 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 Figure 3.

[0052] Figure 3 shows the evolution of the thrust, as a percentage of the nominal value, for three propulsion regimes.

[0053] In a single propulsion mode A regime, the Hall effect propulsion system 10 remains in propulsion mode 211 where the thrust is modulated by voltage modulation of the Hall effect thruster 10. The single propulsion regime A is the typical operating regime of known Hall effect propulsion systems.

[0054] 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).

[0055] In the ON / quasi-OFF C propulsion regime, the Hall effect propulsion system 10 rapidly alternates between the propulsion regime 211 and the standby regime 212. The ON / quasi-OFF C propulsion regime is particularly suited to the needs of orbital rendezvous maneuvers for satellites. Returning to zero thrust, i.e., 0%, would require stopping the gas flow by closing valve 6, and therefore cooling the cathode. This would necessitate a lengthy restart sequence (typically 3 minutes) 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 maintain the cathode (40) at a minimum operating temperature between two activations of the motor power supply (81),the means (90) for controlling the power supply (80) comprising 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 a standby mode (212), said secondary discharge current (Ik) control device providing a secondary discharge current (Ik) increase command to the secondary supply (82) when the absolute variation of a cathode reference voltage for 10 to 20 seconds is greater than 10% or when a secondary discharge voltage oscillates over a time period greater than 1 second or drifts by a value greater than 1V / min.

2. Hall effect propulsion system according to claim 1, 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 standby mode (212), deactivate the motor power supply (81) and activate the secondary power supply (82).

3. A Hall effect propulsion system according to claim 2, wherein the means (90) for controlling the electrical power supply (80) are configured in addition to ensure the transition from propulsion mode (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.

4. Hall effect propulsion system according to any one of claims 2 or 3, 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.

5. Hall effect propulsion system according to any one of claims 2 to 4, wherein the means (90) for controlling the power supply (80) are configured to keep the motor power supply (81) and the secondary power supply (82) active at the same time for a time delay of less than 1 second during the transition phases between the propulsion (211) and standby (212) modes.

6. Satellite comprising at least one Hall effect propulsion system according to any one of claims 1 to 5.

7. A method for 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 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 the method comprises, between two activations of the motor power supply (81), a command to supply a secondary discharge current (Ik) by the secondary power supply (82) to the cathode (40) to maintain the cathode (40) in temperature at a minimum operating temperature, the method further comprising controlling 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), and delivering to the secondary supply (82) a setpoint to increase the secondary discharge current (Ik) when the absolute variation of a reference voltage of the cathode for 10 to 20 seconds is greater than 10%.

8. A control method according to claim 7, comprising in a propulsion mode (211), an activation of the motor power supply (81) and a deactivation of the secondary power supply (82), and, in standby mode (212), a deactivation of the motor power supply (81) and an activation of the secondary power supply (82).

9. A control method according to claim 8, wherein the transition from propulsion mode (211) to standby mode (212) includes an activation of the secondary power supply (82) while the motor power supply (81) is active, and then a deactivation of the motor power supply (81) when the motor discharge current (Id) is less than a threshold motor discharge current.

10. A control method according to any one of claims 8 or 9, wherein the transition from standby mode (212) to propulsion mode (211) includes an activation of the motor power supply (81) while the secondary power supply (82) is active, and then a deactivation of the secondary power supply (82) when the motor discharge current (Id) is greater than twice the threshold discharge current.

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