A small satellite propulsion method with adjustable thrust

Abstract

The application discloses a small satellite propulsion method with adjustable thrust, and belongs to the technical field of satellite propulsion systems. The method is completed by using a propulsion system. The propulsion system comprises a storage tank, a discharge valve is fixedly arranged on the side wall of the storage tank, a pressure stabilizing module and a propulsion electric control panel are arranged on the top of the storage tank, the output end of the pressure stabilizing module is fixedly connected with a thruster through a pipeline, the thruster is fixedly arranged on the top of the storage tank, and an encapsulation structure formed by a side plate and a cover plate is fixedly arranged on the top of the storage tank. The temperature closed-loop control of the storage tank and the evaporator is realized through the optimization design of the internal flow channel of the evaporator, the pressure of the pressure stabilizing module composed of the pressure stabilizing solenoid valve and the evaporator is adjusted, the thruster generates accurate thrust output, and the thrust size can be adjusted. The technical problems of the traditional cold gas propulsion system, such as large volume and high pressure bearing risk, are solved.

Description

Technical Field

[0001] This invention relates to the field of satellite propulsion equipment technology, and specifically to a propulsion method for small satellites with adjustable thrust. Background Technology

[0002] With the development of aerospace technology, microsatellites and nanosatellites are becoming increasingly smaller, and their on-orbit missions are becoming more complex and diverse. Therefore, the propulsion systems for microsatellites and nanosatellites are required to be small in size, low in power consumption, highly integrated, easy to install, and have adjustable thrust. Traditional cold gas propulsion systems have high internal pressure and low gas density in their propellant tanks. Increasing the total thrust requires increasing the size and weight of the tank, which also increases the pressure risk to the internal components of the propulsion system and reduces the satellite's payload capacity. Currently, conventional liquefied gas propulsion systems use low-density propellants, resulting in large tanks. Their high latent heat of vaporization requires significant heating power for propellant vaporization, and they lack thrust adjustment capabilities, limiting the diversity and maneuverability of microsatellites and nanosatellites in orbit. Monomeric chemical propulsion systems are relatively mature and widely used in satellite propulsion systems. However, their thrusters are heavy, have large envelope dimensions, and their metal piping is difficult to bend. The scattered components make assembly on satellites difficult, and the numerous welds increase the risk of leakage. Summary of the Invention

[0003] The purpose of this invention is to provide a thrust-adjustable propulsion method for small satellites to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a propulsion method for a small satellite with adjustable thrust, which is accomplished by a propulsion system. The propulsion system includes a tank, an injection / exhaust valve is fixedly mounted on the side wall of the tank, a voltage stabilizing module and a propulsion control board are mounted on the top of the tank, the output end of the voltage stabilizing module is fixedly connected to a thruster through a pipeline, the thruster is fixedly mounted on the top of the tank, and an encapsulation structure consisting of a side plate and a cover plate is fixedly mounted on the top of the tank.

[0005] The pressure stabilizing module includes a pressure stabilizing solenoid valve, an evaporator, and a pressure sensor. The pressure stabilizing solenoid valve and the evaporator are respectively fixedly mounted on the top of the storage tank. The input end of the pressure stabilizing solenoid valve is connected to the liquid outlet of the storage tank through a pipeline, and the output end of the pressure stabilizing solenoid valve is connected to the input end of the evaporator through a pipeline. The pressure sensor is fixedly mounted on the side wall of the evaporator.

[0006] The propulsion method includes the following steps: Step 1, with the propulsion system in a state of no power supply, hexafluoropropane propellant is added to the storage tank;

[0007] Step 2: Power on the propulsion control board and use the real-time operating system to perform closed-loop control of the temperature within the propulsion system;

[0008] Step 3: During the operation of the propulsion system, the inlet pressure of the thruster is stabilized and controlled by the operation of the voltage stabilization module through the propulsion control board, so that the thrust at the outlet end of the thruster reaches the predetermined thrust requirement.

[0009] Step 4: Activate the thruster to start the propulsion system and generate thrust.

[0010] Step 5: After the propulsion work is completed, the thruster is shut off.

[0011] Preferably, in step 1, hexafluoropropane propellant is added to the storage tank through the injection / extraction valve. Before injection, the storage tank is evacuated to control its internal pressure below 500 Pa. After injection, the injection / extraction valve is closed.

[0012] Preferably, in step 2, a real-time operating system is used to realize closed-loop control of the temperature in the entire system. The closed-loop control of the temperature receives instructions from the host computer through the CAN interface. If the instruction is "start temperature control", a preset temperature range is loaded synchronously. This range is modified by instructions from the host computer.

[0013] When the temperature inside the tank and evaporator is detected to be lower than the minimum value of the temperature range, the MCU outputs a high level on the corresponding I / O port, the MOSFET turns on, and the tank heater and evaporator heater start heating. When the temperature inside the tank and evaporator is detected to be higher than the maximum value of the temperature range, the I / O port outputs a low level, the MOSFET turns off, and the tank heater and evaporator heater stop. This achieves the real-time temperature regulation of the tank and evaporator to meet the vaporization requirements of hexafluoropropane.

[0014] Preferably, in step 3, the voltage regulation control at the thrust inlet is based on an FPGA core, which generates a PWM waveform according to the duty cycle parameters given by the software PID algorithm, and controls the switching frequency and single switching duration of the voltage regulating solenoid valve to achieve voltage regulation control.

[0015] Preferably, a tank heater and an evaporator heater are fixedly mounted on the top of the tank and the evaporator, respectively, and the tank heater and the evaporator heater are electrically connected to the propulsion control board.

[0016] Preferably, a tank temperature sensor and an evaporator temperature sensor are fixedly mounted on the top of the tank and the evaporator, respectively, and the tank temperature sensor and the evaporator temperature sensor are electrically connected to the propulsion control board.

[0017] Preferably, the number of thrusters is at least two, and the two thrusters are symmetrically distributed about the middle of the tank. The output end of the thrusters is fixedly equipped with MEMS micro-nozzles.

[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses hexafluoropropane as a propellant. Through optimized design of the internal flow channel of the evaporator, closed-loop temperature control of the tank and evaporator, and pressure regulation of the pressure-stabilizing module composed of the pressure-stabilizing solenoid valve and the evaporator, the thruster generates precise thrust output, and the thrust magnitude is adjustable. This solves the technical problems of large size and high pressure risk in traditional cold gas propulsion systems, achieving beneficial effects such as high specific impulse, high integration, high reliability, small size, light weight, and stable and adjustable thrust. This propulsion system can be applied to satellite propulsion systems such as micro / nano satellites, which are small in size, require high attitude and orbit control accuracy, have low power consumption, and have complex and diverse missions. Attached Figure Description

[0019] Figure 1 This is a perspective view of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of the present invention.

[0021] Figure 3 This is a schematic diagram of the internal flow channel of the evaporator of the present invention.

[0022] In the diagram: 1. Storage tank; 2. Storage tank temperature sensor; 3. Storage tank heater; 4. Pressure regulating solenoid valve; 5. Evaporator; 6. Evaporator heater; 7. Evaporator temperature sensor; 8. Pressure sensor; 9. Thruster; 10. MEMS micro-nozzle; 11. Propulsion control board; 12. Side plate; 13. Cover plate; 14. Addition and exhaust valve; 15. J30J connector. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] Please see Figure 1 , Figure 2 and Figure 3 This invention provides a technical solution: a propulsion method for small satellites with adjustable thrust. This method employs a propulsion system, which includes a tank 1 containing hexafluoropropane in a gas-liquid two-phase configuration. Hexafluoropropane is used as the propellant; it is green and non-toxic, has a high storage density, and a low saturated vapor pressure. Therefore, the pressure-bearing components such as the tank 1 and the evaporator 5 have high safety margins and design flexibility, enhancing compatibility with the satellite. Furthermore, the latent heat of vaporization of hexafluoropropane is 50-80% lower than other commonly used types of liquefied gas, thereby reducing the heating power of the propulsion system and expanding the application of energy-constrained micro / nano satellites.

[0025] A tank temperature sensor 2 and a tank heater 3 are fixedly installed on the top of the storage tank 1. The tank heater 3 is used to raise the temperature inside the storage tank 1, thereby improving the vaporization efficiency of hexafluoropropane in the storage tank 1. The tank temperature sensor 2 is used to detect the temperature inside the storage tank 1. A filler / drainer valve 14 is fixedly installed on the side wall of the storage tank 1. The filler / drainer valve 14 is used to add hexafluoropropane propellant into the storage tank 1.

[0026] The top of the storage tank 1 is equipped with a liquid outlet, which is connected to the input end of the pressure-regulating solenoid valve 4 through a pipeline. The output end of the pressure-regulating solenoid valve 4 is connected to the evaporator 5. The pressure-regulating solenoid valve 4 can control the flow rate of propellant entering the evaporator 5, thereby adjusting the inlet pressure of the thruster 9 and changing the thrust output of the thruster 9. The evaporator 5 is made using 3D printing technology and has a built-in S-shaped narrow vaporization channel, which does not require subsequent welding. During use, the liquid hexafluoropropane entering the evaporator is fully vaporized.

[0027] The output end of the evaporator 5 is connected to a thruster 9 via a pipeline. There are two thrusters 9, which are fixedly mounted on the top of the tank 1 by a mounting bracket. The two thrusters 9 are symmetrically arranged with the evaporator 5 as the center. Each thruster 9 is fixedly mounted with a MEMS micro nozzle 10 at its output end. The thruster 9 sprays propellant through the MEMS micro nozzle 10 to provide the thrust and impulse required by the satellite and meet the orbit control function requirements of the satellite. The nominal thrust output of the MEMS micro nozzle 10 is 5mN, which can precisely control the orbit and attitude of the micro-nano satellite.

[0028] An evaporator heater 6 is fixedly installed on the top of the evaporator 5. The evaporator heater 6 is used for further vaporization of the gas-liquid mixture of hexafluoropropane in the evaporator 5. An evaporator temperature sensor 7 and a pressure sensor 8 are fixedly installed on the evaporator 5. The evaporator temperature sensor 7 is used to detect the temperature inside the evaporator 5 and provide real-time temperature feedback for the temperature closed loop of the evaporator. The pressure sensor 8 is used to detect the internal gas pressure of the evaporator 5 and provide real-time pressure feedback for the pressure closed loop control of the evaporator 5.

[0029] The top of the storage tank 1 is equipped with a propulsion control board 11. The storage tank temperature sensor 2, storage tank heater 3, pressure regulating solenoid valve 4, evaporator 5, evaporator heater 6, evaporator temperature sensor 7, pressure sensor 8 and thruster 9 are all electrically connected to the propulsion control board 11. The power supply and pressure acquisition of pressure sensor 8, the temperature acquisition of temperature sensor, the power supply and on / off control of pressure regulating solenoid valve 4, the power supply and on / off control of thruster 9, the closed-loop temperature control of storage tank 1 and evaporator 5, the closed-loop pressure control of evaporator 5 and the thrust adjustment of thruster 9 are all realized through the propulsion control board 11.

[0030] The specific implementation method is as follows: after the power-on control board 11 is pushed, the software uses the real-time operating system FreeRTOS to realize closed-loop control of the temperature in the entire system. The closed-loop control of the temperature receives the upper-level command through the CAN interface. If the command is "start temperature control", the preset temperature range is loaded synchronously. This range can be modified by the upper-level computer command.

[0031] When the temperature in tank 1 and evaporator 5 is detected to be lower than the minimum value of the temperature range, the MCU outputs a high level on the corresponding I / O port, the MOSFET is turned on, and tank heater 3 and evaporator heater 6 start heating. When the temperature in tank 1 and evaporator 5 is detected to be higher than the maximum value of the temperature range, the I / O port outputs a low level, the MOSFET is turned off, and tank heater 3 and evaporator heater 6 stop. This achieves the real-time temperature regulation of tank 1 and evaporator 5 to meet the vaporization requirements of hexafluoropropane.

[0032] Among the aforementioned electronic components, the pressure regulating solenoid valve 4, the evaporator 5, and the pressure sensor 8 form a pressure regulating module to regulate the inlet pressure of the thruster 9. The pressure regulation control is achieved by using an FPGA core to implement PWM output and software PID algorithm to calculate the PWM duty cycle and control the switching of the pressure regulating solenoid valve 4.

[0033] The propulsion control board 11 acquires the collected values ​​of each channel of the ADS8688 chip via SPI communication. Based on the sampling accuracy (e.g., 16-bit), the voltage value is converted into a pressure value. Global variables are set to store the upper and lower pressure thresholds set in the pressure regulation command received from the CAN communication task. PID calculation is performed based on the upper and lower thresholds and the real-time data fed back by the current pressure sensor 8. The calculation result is set as the duty cycle of the output PWM to control the switching duration and frequency of the pressure regulating solenoid valve 4. The switching life of the pressure regulating solenoid valve 4 is not less than 20 million cycles, thereby providing feedback control of the inlet pressure of the downstream thruster 9 to achieve adjustable thrust. The thrust adjustment range can reach 0.1 to 2 times the nominal value.

[0034] The top of the tank 1 is fixedly equipped with an encapsulation structure consisting of a side plate 12 and a cover plate 13. The various electronic components in the propulsion system are encapsulated in the upper part of the tank 1 through the side plate 12 and the cover plate 13. The whole adopts a modular design, and all components are integrated and installed in one piece. There are no external pipelines or loose wires. Only four M4 screws are needed for mechanical connection with the satellite, and one J30J connector 15 is needed for electrical connection with the satellite, which facilitates the overall docking with the satellite and subsequent testing and installation.

[0035] A thrust-adjustable propulsion method for small satellites includes the following steps:

[0036] Step 1: When the propulsion system is not powered, hexafluoropropane propellant is added to the storage tank 1 through the fill valve 14. Before adding, the storage tank 1 needs to be evacuated to control its internal pressure below 500Pa. After adding, the fill valve 14 is closed.

[0037] Step 2: After pushing the control board 11 onto the circuit, use the real-time operating system FreeRTOS to create various sub-tasks to realize communication, temperature control, voltage regulation control, etc. Create an independent CAN communication task with a stack size of 256 bytes in the FreeRTOS real-time operating system, and use event triggering (CAN communication receive interrupt) to receive upper computer instructions (such as "start temperature control", "start voltage regulation") to set the temperature range.

[0038] Then, an independent temperature control task with a stack size of 256 bytes is created in the FreeRTOS real-time operating system. Using a periodic scheduling method, it communicates with the temperature sensors via a single-bus protocol to collect real-time temperature data from tank temperature sensor 2 and evaporator temperature sensor 7. The task then uses the MCU's I / O port to output a push-pull level, driving the MOSFETs to control the on / off state of the tank heater 3 and evaporator heater 6. Commands from the host computer are received via the CAN interface. If the command is "Start Temperature Control," a preset temperature range is synchronously loaded. This range can be dynamically modified via the host computer command: when the temperature of tank 1 and evaporator 5 is detected to be lower than the minimum value of the temperature range, the corresponding MCU I / O port outputs a high level (3.3V), the MOSFET is turned on, and the two heaters start. When the temperature of tank 1 and evaporator 5 is detected to be higher than the maximum value of the temperature range, the I / O port outputs a low level (0V), the MOSFET is turned off, and the two heaters stop heating.

[0039] Step 3: The voltage regulation control of the voltage regulating solenoid valve 4 is achieved by using an FPGA core as the core. The FPGA generates a PWM waveform based on the duty cycle parameters given by the software PID algorithm, controlling the opening and closing of the voltage regulating solenoid valve 4 to achieve voltage regulation. Specifically, a Microchip M2S series chip is selected. By using the FPGA core CorePWM as a slave device, the Cortex M3 core can call CorePWM to output a fixed frequency PWM according to a predetermined configuration. The output PWM channel is connected to the input pin of the DRV104 driver chip. The DRV104 controls the switching frequency and single switching duration of the voltage regulating solenoid valve 4 according to the frequency and duty cycle of the input PWM.

[0040] Create an independent voltage regulation control task with a stack size of 256 bytes in the FreeRTOS real-time operating system, using a periodic scheduling method. Set the input range of the enabled channels based on the measurement range of pressure sensor 8. Send an automatic scan command to cause the ADS8688 chip to sequentially sample the enabled channels. Within the task, acquire the sampled values ​​from each channel of the ADS8688 chip via SPI communication, and convert the voltage values ​​into pressure values ​​according to the sampling precision (e.g., 16-bit).

[0041] Global variables are set to store the upper and lower pressure thresholds set in the pressure regulation command received from the CAN communication task. PID calculations are performed based on the upper and lower thresholds and the current pressure value fed back by pressure sensor 8. The calculation result is constrained to between 0 and 100 and set as the duty cycle of the output PWM. The switching duration and frequency of the pressure regulating solenoid valve 4 are controlled to adjust the gas flow rate from upstream to downstream thruster 9 to achieve the predetermined thrust requirement.

[0042] Step 4: Activate thruster 9 to enable the system to operate, and thruster 9 will generate thrust.

[0043] Step 5: After the work is completed, the thruster 9 is turned off.

[0044] This invention utilizes hexafluoropropane, which has high density, low latent heat of vaporization, and low saturated vapor pressure, as the working fluid for the thruster. It integrates functions such as heating closed-loop control, pressure closed-loop control, and thrust adjustment, resulting in stable thrust output and adjustable thrust. Compared to cold gas propulsion schemes, existing liquefied gas propulsion, and single-component chemical propulsion systems, this solution makes the propulsion system safer, more reliable, more integrated, and has superior overall performance.

Claims

1. A propulsion method for a small satellite with adjustable thrust, characterized in that, The propulsion system is used to complete the task. The propulsion system includes a tank (1). The side wall of the tank (1) is fixedly equipped with a filler valve (14). The top of the tank (1) is equipped with a voltage stabilizing module and a propulsion control board (11). The output end of the voltage stabilizing module is fixedly connected to a thruster (9) through a pipeline. The thruster (9) is fixedly installed on the top of the tank (1). The top of the tank (1) is fixedly equipped with an encapsulation structure consisting of a side plate (12) and a cover plate (13). The pressure stabilizing module includes a pressure stabilizing solenoid valve (4), an evaporator (5), and a pressure sensor (8). The pressure stabilizing solenoid valve (4) and the evaporator (5) are respectively fixedly mounted on the top of the storage tank (1). The input end of the pressure stabilizing solenoid valve (4) is connected to the liquid outlet of the storage tank (1) through a pipeline. The output end of the pressure stabilizing solenoid valve (4) is connected to the input end of the evaporator (5) through a pipeline. The pressure sensor (8) is fixedly mounted on the side wall of the evaporator (5). The propulsion method includes the following steps: Step 1: With the propulsion system powered off, hexafluoropropane propellant is added to the storage tank (1); Step 2: Power on the propulsion control board (11) and use the real-time operating system to perform closed-loop control of the temperature in the propulsion system; Step 3: During the operation of the propulsion system, the pressure at the inlet of the thruster (9) is stabilized and controlled by the operation of the pressure stabilizing module through the propulsion control board (11), so that the thrust at the outlet of the thruster (9) reaches the predetermined thrust requirement. Step 4: Activate the thruster (9) to start the propulsion system and generate thrust. Step 5: After the propulsion work is completed, the thruster (9) is shut off; In step 3, the voltage regulation control at the inlet of the thruster (9) is based on the FPGA core, which generates a PWM waveform according to the duty cycle parameters given by the software PID algorithm, and controls the switching frequency and single switching duration of the voltage regulation solenoid valve (4) to achieve voltage regulation control. In step 2, after the push control board (11) is powered on, an independent temperature control task with a stack size of 256 bytes is created in the FreeRTOS real-time operating system. The task is scheduled in a periodic manner and communicates with the temperature sensor through a single bus protocol to collect the real-time temperature data of the tank temperature sensor (2) and the evaporator temperature sensor (7). The push-pull level is output through the MCU's IO port to drive the MOS tube to control the on / off state of the two heaters, the tank heater (3) and the evaporator heater (6). In step 2, a real-time operating system is used to realize closed-loop control of the temperature in the entire system. The closed-loop control of the temperature receives instructions from the host computer through the CAN interface. If the instruction is "start temperature control", the preset temperature range is loaded synchronously. This range is modified by instructions from the host computer. When the temperature in the storage tank (1) and evaporator (5) is detected to be lower than the minimum value of the temperature range, the MCU outputs a high level at the corresponding IO port, the MOS transistor is turned on, and the storage tank heater (3) and evaporator heater (6) start heating. When the temperature in the storage tank (1) and evaporator (5) is detected to be higher than the maximum value of the temperature range, the IO port outputs a low level, the MOS transistor is turned off, and the storage tank heater (3) and evaporator heater (6) stop, thereby realizing the real-time temperature regulation requirements of the storage tank (1) and evaporator (5) and meeting the vaporization requirements of hexafluoropropane.

2. The thrust-adjustable propulsion method for a small satellite according to claim 1, characterized in that: In step 1, hexafluoropropane propellant is added to the storage tank (1) through the injection valve (14). Before injection, the storage tank (1) is evacuated to control its internal pressure below 500 Pa. After injection, the injection valve (14) is closed.

3. The thrust-adjustable propulsion method for a small satellite according to claim 1, characterized in that: The tank (1) and the evaporator (5) are respectively fixedly equipped with a tank heater (3) and an evaporator heater (6), and the tank heater (3) and the evaporator heater (6) are respectively electrically connected to the propulsion control board (11).

4. The thrust-adjustable propulsion method for a small satellite according to claim 1, characterized in that: The top of the storage tank (1) and the evaporator (5) are respectively fixedly equipped with a storage tank temperature sensor (2) and an evaporator temperature sensor (7), and the storage tank temperature sensor (2) and the evaporator temperature sensor (7) are respectively electrically connected to the propulsion control board (11).

5. The thrust-adjustable propulsion method for a small satellite according to claim 1, characterized in that: The number of thrusters (9) is at least two, and the two thrusters (9) are symmetrically distributed about the middle of the tank (1). The output end of the thruster (9) is fixedly equipped with a MEMS micro-nozzle (10).

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