Iodine working medium flow control device for electric propulsion

Abstract

The invention discloses an iodine working medium flow control device for electric propulsion. The iodine working medium flow control device comprises an iodine storage tank and an iodine sublimation tank which are independently arranged, an outlet of the iodine storage tank is sequentially connected with a first self-locking valve, an iodine sublimation tank, a second self-locking valve and a throttler; the iodine storage tank and the iodine sublimation tank are respectively provided with a first heater and a second heater for temperature control; a solid iodine working medium stored in the iodine storage tank enters the iodine sublimation tank to be sublimated and then is stably output outwards through the flow controller. According to the iodine working medium electric propulsion system, the storage process and the sublimation process of the iodine working medium are innovatively separated, accurate control over the temperature of the iodine storage tank is not needed, the iodine working medium electric propulsion system can be applied to a large satellite propulsion system, the efficiency of the electric propulsion system is improved, and the cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the field of space instruments and equipment, in particular to an iodine working medium flow control device for electric propulsion. Background Art

[0002] Electric propulsion systems have entered the stage of mass application on various types of spacecraft and satellite platforms at home and abroad, providing satellites with all or part of the total impulse required for tasks such as orbit raising, deorbiting, position maintenance, and momentum wheel unloading. Since electric propulsion systems have the advantage of high specific impulse, they can greatly improve the satellite's payload ratio and reduce the weight of satellite launches. The use of electric propulsion systems has become a symbol of the new generation of satellite platforms.

[0003] At present, all on-orbit electric propulsion system targets use Xe gas as a propellant. Xe gas is an inert atomic gas that can only be separated from air. The content of Xe gas in air is 0.087ppm, which is difficult to separate, resulting in its high price. At the same time, it is easily affected by supply and demand, and the price fluctuates between 20,000 and 100,000 yuan / kg. Usually, the launch of a single satellite is more than 500kg of Xe gas, and the propellant cost is more than 50 million yuan; for a low-orbit Internet satellite constellation, a single satellite carries 30kg of xenon gas, and the propellant cost of 1,000 satellites is at least 600 million yuan; in addition, deep space exploration missions such as manned space flight and Mars exploration have a greater demand for propellants for low-cost electric propulsion systems.

[0004] Therefore, replaceable low-cost electric propulsion fluids are an important direction for the long-term development of electric propulsion in the future. Starlink satellites use Kr krypton and Ar argon to solve the problem of high cost and large fluctuations of xenon gas. However, the main problem of Kr and Ar fluids is low storage density. At 20°C and 15Mpa, the storage density of Xe, Kr, and Ar is 2.045kg / L, 0.713kg / L, and 0.261kg / L, respectively. For Starlink, which has a small total impulse demand and carries a few kilograms to more than ten kilograms of work, this problem will not be prominent. However, for constellation satellites with tens of kilograms of propellant per star, high-orbit satellites, deep space exploration satellites, and other single satellites carrying tens of kilograms to hundreds of kilograms of propellant, this solution will cause the volume and weight of the gas cylinder to increase sharply, making the project unfeasible. At the same time, the efficiency of Kr and Ar thrusters is generally lower than that of Xe thrusters, which is not an optimal choice.

[0005] Iodine is also a low-cost alternative propellant. First, the atomic weight of iodine is 126, which is close to that of xenon 131. Its ionization energy of 10.4eV is lower than that of xenon 12.1eV, and it is easier to ionize. This makes the performance of the iodine electric propulsion system almost the same as that of the xenon electric propulsion system, and both can achieve high efficiency. Second, iodine is stored in solid state at room temperature. When the pressure is 0MPa, its density of 4.94kg / L is much higher than that of xenon at 15Mpa. The benefit is that it can save a lot of space inside the satellite and reduce the weight of the gas cylinder. At the same time, the absence of high pressure can make the tank design conformable, making full use of the space inside the satellite and reducing the size of the satellite. Third, solid-state storage can be pre-packaged to complete the filling of the working fluid in advance, saving the filling process and time of the base before the satellite launch. Finally, iodine is widely distributed in seawater, easy to extract, and its price is negligible compared to xenon. The ultra-pure iodine used for propulsion costs hundreds of yuan per kilogram, which can save a lot of satellite propellant costs. Therefore, using iodine to replace xenon propellant is a feasible direction to solve the long-term development of electric propulsion.

[0006] However, the difficulty of using iodine working fluid for flow control lies mainly in: the need to accurately control the sublimation surface temperature of the iodine working fluid storage tank throughout its life cycle, so that the iodine tank can output stable iodine vapor, thereby providing the thruster with a fixed mg / s-level micro-flow gaseous iodine working fluid output during its entire life cycle, without clogging and corroding the gas path or the propulsion product itself. At present, all schemes are only suitable for small-capacity iodine tanks for small satellite propulsion systems. For medium and large satellites, due to the large amount of iodine propellant required and the large volume of the iodine tank, it is difficult to accurately control the temperature. At the same time, it is difficult to ensure the real-time temperature stability of the solid interface as the solid fuel is consumed. Summary of the invention

[0007] The technical problem solved by the present invention is: to overcome the difficulty of iodine working fluid flow control, and on the basis of considering the characteristics of iodine working fluid, to provide an iodine working fluid flow control device for electric propulsion, so that satellites that need to carry a large capacity of propellant can use iodine working fluid for precise flow control, thereby improving the efficiency of the electric propulsion system and significantly reducing costs.

[0008] The technical solution of the present invention is: an iodine working medium flow control device for electric propulsion, comprising an iodine storage tank, an iodine sublimation tank, a first self-locking valve, a second self-locking valve, a first heater, a second heater and a throttle; the outlet of the iodine storage tank is connected to the first self-locking valve, the iodine sublimation tank, the second self-locking valve and the throttle in sequence; the iodine storage tank and the iodine sublimation tank are respectively provided with a first heater and a second heater for temperature control; the solid iodine working medium stored in the iodine storage tank enters the iodine sublimation tank for sublimation and is then output to the outside through the throttle.

[0009] Furthermore, the iodine storage tank is a large-capacity tank, and its capacity is enough to meet the total amount of iodine working fluid required for the electric propulsion system to work on orbit; the iodine sublimation tank is a small-capacity tank, and its capacity is enough to ensure the volume required to accommodate the iodine working fluid of the electric propulsion system for a single operation under redundancy.

[0010] Furthermore, the temperature control method of the first heater is non-precise control; the temperature control method of the second heater is precise control based on negative feedback of device output.

[0011] Furthermore, a Hall thruster is arranged at the output of the throttle, and the anode current output by the Hall thruster is collected and fed back to the second heater, so that the heating temperature of the iodine sublimation tank is maintained at a set temperature and the gaseous iodine working medium is output stably.

[0012] Furthermore, the temperature of the iodine storage tank is controlled at 0-50°C, and the temperature of the iodine sublimation tank is controlled at 50-120°C.

[0013] Furthermore, the iodine storage tank is made of a non-metallic material that does not chemically react with iodine, and the iodine sublimation tank is made of a metallic material that does not chemically react with iodine.

[0014] Furthermore, the iodine storage tank adopts a conformable design, and its appearance is made according to the internal space of the satellite and fully utilizes the internal space of the satellite.

[0015] The present invention also provides a method for controlling the flow rate of iodine working medium using an iodine working medium flow rate control device for electric propulsion, comprising:

[0016] After the electric propulsion system enters orbit, the temperature of the iodine storage tank is controlled to remain within the set range; the first self-locking valve and the second self-locking valve are kept closed;

[0017] During the intermittent period of the electric propulsion system, when the temperature of the iodine sublimation tank is lower than the temperature of the iodine storage tank, the first self-locking valve is opened to replenish the iodine working medium to the iodine sublimation tank through the iodine storage tank;

[0018] Before the electric propulsion system is ignited, the first self-locking valve is closed, the second self-locking valve is opened, and the temperature of the second heater is controlled within the set range;

[0019] After the electric propulsion system is ignited, the negative feedback amount of the second heater is controlled according to the output of the system, so that the heating temperature of the iodine sublimation tank is maintained at the set temperature;

[0020] After the electric propulsion system is ignited, the second self-locking valve is closed to keep the temperature of the second heater unchanged, waiting for the iodine working fluid in the channel to be completely output.

[0021] The advantages of the present invention compared with the prior art are:

[0022] (1) The present invention innovatively proposes to separate the storage and sublimation processes of iodine working fluid, eliminating the need for precise temperature control of the iodine storage tank, thereby achieving a large-capacity design for iodine working fluid storage, and enabling the iodine working fluid electric propulsion system to be applied to large satellite propulsion systems;

[0023] (2) The iodine storage tank designed by the present invention does not require high temperature and high-precision temperature control, and the entire iodine storage tank can be made of non-metallic materials. At the same time, no complex structure is required in the iodine tank, making it easy to implement.

[0024] (3) The iodine sublimation tank designed by the present invention can be made directly of precious metals at low cost due to its small size, has good temperature control characteristics, and has excellent compatibility with iodine working fluid.

[0025] (4) The present invention accurately controls the temperature of a small volume iodine sublimation tank through anode current feedback, thereby achieving accurate control of the flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the composition of the device of the present invention. DETAILED DESCRIPTION

[0027] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0028] The composition of the iodine working fluid flow control device for electric propulsion given in this embodiment is shown in the attached Figure 1 , including a conformal large-capacity iodine storage tank, two self-locking valves, a buffer tank for iodine sublimation, and a throttle; the outlet of the conformal large-capacity iodine storage tank is connected in sequence to the first self-locking valve, the buffer tank for iodine sublimation, the second self-locking valve, and the throttle; the conformal large-capacity iodine storage tank and the buffer tank for iodine sublimation are respectively provided with heating plate groups for temperature control.

[0029] In one possible implementation, for the conformal design of the large-capacity iodine storage tank, the core design is to set it separately from the buffer tank for iodine sublimation, so as to separate the storage and use of iodine. The conformal design of the large-capacity iodine storage tank is made of non-metallic materials, making full use of the space in the satellite cabin, and maintaining the basic temperature of 0-50°C through the heating plate group 1. It does not require precise control, so as to avoid that as the solid iodine working medium is consumed, the temperature of the iodine working medium outlet surface cannot be accurately controlled, thereby failing to achieve stable control and output of the pressure in the iodine working medium tank. In addition, taking advantage of the short-term working characteristics of the electric propulsion system, when the electric propulsion system is not working, the conformal design of the large-capacity iodine storage tank slowly replenishes the iodine working medium to the buffer tank for iodine sublimation.

[0030] In one possible implementation, for a buffer tank for iodine sublimation, for example, for a 1.35kW electric propulsion system used on a high-orbit communication satellite, the electric propulsion system only works for 2 hours a day. According to the three times working fluid demand, the buffer tank only needs 18mL of volume. Since the buffer tank for iodine sublimation is small enough and has a small heat capacity, precise iodine working fluid temperature control can be performed to achieve stable pressure output.

[0031] Preferably, a Hall thruster is provided at the output of the throttle to collect the anode current Id of the Hall sensor for rapid feedback control of the heating plate group of the buffer tank for iodine sublimation, thereby achieving high-precision control of the output pressure and thus achieving stable control output of the flow rate.

[0032] Preferably, the conformally designed large-capacity iodine storage tank is made of non-metallic material that does not chemically react with iodine, and the buffer tank for iodine sublimation is made of metallic material that does not chemically react with iodine.

[0033] The specific working process of the iodine working fluid flow control device for electric propulsion is as follows:

[0034] 1) Before launching, the self-locking valve 1 and the self-locking valve 2 are closed, and there is no air in the buffer tank for iodine sublimation and the large-capacity iodine storage tank designed in accordance with the shape;

[0035] 2) After entering orbit, control the temperature of the large-capacity iodine storage tank designed to be conformable to 40-50°C;

[0036] 3) Open the self-locking valve 1;

[0037] 4) Before the electric propulsion system works, open the self-locking valve 2, close the self-locking valve 1, and accurately control the temperature of the heating plate group 2; the specific temperature adopts the corresponding temperature of the micro-flow iodine working fluid calibrated on the ground, and the temperature control range is a precise temperature between 50 and 120°C;

[0038] 5) Ignition of electric propulsion system;

[0039] 6) Accurately control the temperature of the heating plate group 2 according to the feedback of the anode current Id, so as to achieve stable output of the electric propulsion system;

[0040] 7) After ignition, close the self-locking valve 2, maintain the temperature of the heating plate group 2 and the Hall thruster ≥ 10min, and wait for the iodine working fluid in the pipeline to completely sublimate and spray out to prevent the pipeline system from being blocked due to iodine condensation;

[0041] 8) After the temperature of the buffer tank for iodine sublimation drops to ≤ the temperature of the conformally designed large-capacity iodine storage tank, open the self-locking valve 1.

[0042] If the electric propulsion system does not work for a long time, the temperature control of the conformally designed large-capacity iodine storage tank can be turned off.

[0043] It is to be understood that the present invention is described by way of embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and embodiments that can fall within the scope of the claims of this application all fall within the scope protected by the present invention.

[0044] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An iodine working fluid flow control device for electric propulsion, characterized in that: The invention comprises an iodine storage tank, an iodine sublimation tank, a first self-locking valve, a second self-locking valve, a first heater, a second heater and a throttle; the outlet of the iodine storage tank is sequentially connected to the first self-locking valve, the iodine sublimation tank, the second self-locking valve and the throttle; the iodine storage tank and the iodine sublimation tank are respectively provided with a first heater and a second heater for temperature control; the solid iodine working medium stored in the iodine storage tank enters the iodine sublimation tank for sublimation and is then output to the outside through the throttle.

2. The iodine working medium flow control device for electric propulsion according to claim 1, characterized in that: The iodine storage tank is a large-capacity tank, whose capacity is enough to meet the total amount of iodine working fluid required for the electric propulsion system to work on orbit; the iodine sublimation tank is a small-capacity tank, whose capacity is the volume required to accommodate the iodine working fluid required for a single operation of the electric propulsion system.

3. The iodine working medium flow control device for electric propulsion according to claim 1, characterized in that: The temperature control method of the first heater is non-precise control; the temperature control method of the second heater is precise control based on negative feedback of device output.

4. The iodine working medium flow control device for electric propulsion according to claim 3, characterized in that: A Hall thruster is arranged at the output of the throttle, and the anode current output by the Hall thruster is collected and fed back to the second heater, so that the heating temperature of the iodine sublimation tank is maintained at the set temperature and the gaseous iodine working medium is output stably.

5. The iodine working medium flow control device for electric propulsion according to claim 3, characterized in that: The temperature of the iodine storage tank is controlled at 0-50°C, and the temperature of the iodine sublimation tank is controlled at 50-120°C.

6. The iodine working medium flow control device for electric propulsion according to claim 1, characterized in that: The iodine storage tank is made of non-metallic materials that do not chemically react with iodine, and the iodine sublimation tank is made of metal materials that do not chemically react with iodine.

7. The iodine working medium flow control device for electric propulsion according to claim 1, characterized in that: The iodine storage tank adopts a conformable design, and its shape is made according to the internal space of the satellite.

8. A method for controlling iodine working medium flow rate using the iodine working medium flow rate control device for electric propulsion according to claim 1, characterized in that: include: After the electric propulsion system enters orbit, the temperature of the iodine storage tank is controlled to remain within the set range; the first self-locking valve and the second self-locking valve are kept closed; During the intermittent period of the electric propulsion system, when the temperature of the iodine sublimation tank is lower than the temperature of the iodine storage tank, the first self-locking valve is opened to replenish the iodine working medium to the iodine sublimation tank through the iodine storage tank; Before the electric propulsion system is ignited, the first self-locking valve is closed, the second self-locking valve is opened, and the temperature of the second heater is controlled within the set range; After the electric propulsion system is ignited, the negative feedback amount of the second heater is controlled according to the output of the system, so that the heating temperature of the iodine sublimation tank is maintained at the set temperature; After the electric propulsion system is ignited, the second self-locking valve is closed to keep the temperature of the second heater unchanged, waiting for the iodine working fluid in the channel to be completely output.

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