Ion thruster, also known asIon engine, one of the space electric propulsion technologies, which is characterized bythrustSmallSpecific impulseHigh, widely used in space propulsion, such asSpacecraft Attitude Control , position keeping, orbital maneuver andInterstellar flightEtc.[1]The principle is that the gaseous working mediumionization, and under the action of a strong electric field, accelerate the ion ejectionReaction forcePush the satelliteattitudeAdjust ortrackTransfer task.The ion thruster has the characteristics of high specific impulse, high efficiency and small thrust.Compared with the traditional chemical propulsion, the ion thruster requires less working fluid mass, which is the most suitable for long-distance navigation among the practical propulsion technologies.The ion thruster is a power device that canspacecraftProvide power.Its performance includes thrust, specific impulse and efficiency, which is usually evaluated by efficiency under the condition of ensuring thrust and specific impulse.[1]
Ion thruster is a kind of electric propulsion, which is characterized by low thrust and high specific impulse. It is widely used in space propulsion, such as spacecraft attitude control, position maintenance, orbital maneuver and interstellar flight.[1]
Ion propulsion is also called "electrostatic propulsion" because it uses the working medium to ionize to generate ions, which accelerate ejection under the action of electrostatic field to generate thrust.The acceleration principle of ion propulsion is relatively simple. Theoretically, there is no energy loss during acceleration, so the efficiency is high. Under the acceleration voltage of 1kV, the specific impulse can be obtained for thousands of seconds.Ion propulsion is the earliest development time, ground and spaceflight testIt is a kind of electric propulsion.[2]
Ion propulsion began SERT-I space flight test as early as 1965, and SERT-II space flight test was conducted in 1970;Since 1997, it has been officially used on commercial satellites;It was first used as the main propulsion system of spacecraft in 1999.[2]
With the requirement of longer and longer service life of satellites, especially large satellitesCommunication satelliteIts service life is up to 15 years. In order to maintain the orbital fixed position, more and more propellants are needed, which occupyPayloadWeight of.Therefore, large communication satellitespropulsion system It is imperative to switch to electric propulsion.In addition, the widespread rise of small satellites has also raised the demand for electric propulsion (including ion propulsion).[2]
Technical Principles
Announce
edit
Ion Thruster
The traditional rocket is propelled forward by the high-speed gas ejected from the tail.The ion thruster also uses the same jet principle, but it does not use fuel combustion to exhaust hot gas, and does not use chemical combustion. Instead, it uses electric energy to act on the working medium to stimulate high-speed ion flow and then propel.What it ejects is a bunch ofcharged particleOr ions.The propelling force it provides may be relatively weak, but the key is that this ion thruster requires much less fuel than ordinary rockets.As long as the ion thruster can maintain stable performance for a long time, it will eventually be able tospace shipAccelerate to a higher speed.
Relevant technologies have been applied to some spacecraft, such as Japan's“Hayabusa ”Space probe,European"Smart 1"Spacecraft and American”Dawn“And technology has made great progress.The future is most promisingOuter space travelThe spacecraft propeller may be VASIMRPlasma rocket。This kind of rocket is slightly different from ordinary ion thrusters.Ordinary ion thrusters use powerfulelectromagnetic fieldAnd VASIMR plasma rocket usesradio frequencyThe generator heats the ions to 1 million degrees Celsius.In the powerfulmagnetic fieldThe ions rotate at a fixed frequency, tune the RF generator to this frequency, inject strong energy into the ions, and constantly increase the propulsion force.The test preliminarily proves that if everything goes well, the VASIMR plasma rocket will be able to pushManned spacecraftReach Mars in 39 days.
characteristic
Announce
edit
Ion electric propulsion engine is characterized by low acceleration force and acceleration, which may only be tens of millinewtons and a few centimeters per square second.Some people describe this thrust as "blowing a piece of paper".But withChemical rocketThe extremely short combustion time is different, and the acceleration time provided by the electric propulsion rocket can be very long, so the specific impulse of the engine is very large, which means that the working medium of the same quality can provide greater total thrust and final speed.On the other hand, small thrust is often enough for satellite attitude adjustment and orbit change.[3]
Performance evaluation method
Announce
edit
Ion thruster is a kind of power device. The method to evaluate the performance is to evaluate the efficiency under the condition of ensuring its thrust and specific impulse. The higher the efficiency, the better the performance of the thruster. It is intuitively shown that under certain thrust and specific impulse, the smaller the power consumed by the ion thruster, the better the performance.When evaluating the performance of ion thrusters, first measure the thrust and specific impulse, then measure or calculate the efficiency, or measure the utilization of propellant and the electric power consumed.[1]
The thrust of ion thrusters is small, usually at the millinewton level. At present, there are two methods to measure the thrust of ion thrusters abroad: one is direct measurement, the other is calculation by formula.Due to the small thrust, when measuring on the ground, due to the influence of gravity, cable lead and propellant pipeline, large measurement errors will be caused.In order to improve the accuracy of thrust measurement, the method of combining direct measurement with formula calculation is generally adopted.Generally speaking, at the initial stage of product development, the thrust can be calculated by formula calculation method. After the product is basically finalized, the thrust can be directly measured and compared with the formula method.At present, small thrust measurement is widely used abroadMicrobalanceAnd laser interferometry to measure micro displacement, and in the early days, there were mechanical displacement measurement methods such as inverted pendulum and torsional pendulum.China has developed the balance method to measure the micro thrust, but when measuring the thrust of the ion thruster, due to the influence of the plasma, the measurement system will produce discharge and spark, which will affect the measurement results.thrustDirect measurement methodThe measurement systems of the ion thruster are complex, and the measurement process is also cumbersome. During the measurement, not only the system needs to be calibrated online, but also noise interference will affect the measurement accuracy. The plasma generated by the ion thruster will also affect the microbalance, and even make the balance unable to work normally, shielding treatment is also required.To evaluate the performance of ion thrusters, in addition to thrust, it is necessary to measure the specific impulse, propellant flow and power consumption.When evaluating the performance of RIT-XT radio frequency ion thruster, the EU mainly measured its thrust, specific impulse, propellant utilization (excluding neutralizer flow) and total power consumption.[1]
present situation
Announce
edit
Ion thrusters combine electrical energy withXenonConvert to Bandpositive chargeHigh speed ion current applied by metal high-voltage transmission networkElectrostatic attractionThe ion current obtains acceleration, and the accelerated ion makes the thruster obtain a speed up to 143201 kilometers per hour, pushing the spacecraft forward.Ion engineOfcombustion efficiency About 10 times higher than that of conventional chemical engines.
Since 2012, after 10000 hours of operation, China has successfully completed the test of XIPS-20 xenon ion thruster on the "Shijian 9" science satellite.The propeller is only 200 mm in diameter and weighs 140 kg.The main advantage of the ion thruster is that, although compared with the chemical fuel engine, the ion thruster has relatively weak driving force, it is stable and efficient, and uses less fuel.stayspace explorationMedium and small diameter ion thrusters can also reduce the mass of satellites.[4]The ion electric thrust technology was used for the first time on the satellite carried by the "Shijian 9" launched by China. Since then, it has beenspace technologyOpened a new door.Previously, this technology has been monopolized by space powers such as the United States and Russia[5]。
R&D Department
The research department is the scientific research team of Lanzhou Institute of Space Physics (510).510 institute is the first unit to carry out research on electric propulsion technology in China. As early as 1974, it began to develop ion electric thrust system. By 1986, it had developed 80mmmercuryIon electric propulsion, which won the first prize of the National Science and Technology Progress Award in 1987, reached the international leading level at that time, and its product level was no less than that of the United States, which has been engaged in this research since the 1950s.But this has becomeIon electric propulsion systemWhen victory turns to decline.Due to the constraints of science and technology at that time, and the fact that the United States did not start its application, the relevant national departments decided not to engage in the research of ion electric propulsion system.This release will last ten years.However, 510 institutes are optimistic about the future development of this technology and have not disbanded this scientific research team, which has been maintained through self financing.The 90mm xenon ion electric propulsion system was successfully developed from 1988 to 1993.
Device Information
The ion electric propulsion system carried by Shijian 9 A satellite successfully ignited for the first time and worked stably for 3 minutes. Then it ignited for the second time and worked stably for nearly 4 minutes. The flight test of Shijian 9 A satellite ion electric propulsion system got off to a good start.The whole ion propulsion subsystem includes one propellant storage module, one voltage regulating module and fourflowControl module, 4 sets of ion thrusters and other auxiliary equipment, the dry weight of the system is about 140 kg.The rated thrust of a single ion thruster is 40 mN, the specific impulse is about 3000 seconds, and the working life is between 10000 and 15000 hours, reaching the international advanced level[5]。
New type propeller
The development plan of the new ion thruster is based on the "Deep Space 1“detectorBased on the successful completion of the task.In 1998, the United States launched a"Shenkong 1“Detector.The probe is powered by an ion thruster with a diameter of 3.048 decimeters. During the 20 month mission, the spacecraft reached a speed of 12711 kilometers per hour.The success of the "Deep Space 1" mission is the first step towards the widespread application of high-power ion propulsion. Compared with the "Deep Space 1" ion engine, NASA's high-performance xenon propulsion ion engine can carry much more payload and has a longer life.
The space propulsion program seeks to develop advanced propulsion technology to greatly reduceNASAThe cost of scientific tasks, reduce quality and shorten travel time.
Ion engine
Plasma engine
Ion engine, which is commonly referred to as“Electric rocket”The principle is not complicated. The propellant isionizationIt forms particles, accelerates in the electromagnetic field, and ejects at high speed.From the perspective of development trend, the research scope of the United States covers almost all types ofElectric thrusterHowever, the development of ion engine is the main focus, and NASA has played the most active role in the application and preparation plan of technology ".Launched by NASA in October 1998Space probe"Shenkong 1" took the lead in realizing the ion engine system as the main propulsion system, which marks that the application of electric propulsion has entered a new stage. During the operation of the ion propulsion system, the autonomous navigator of "Shenkong 1" can select the throttling stage of the thruster and adjust the thrust according to the model of solar array generating electric energy and the power consumption of on-board equipment.In general, ballistic maneuver and mid course correction are also performed by the ion propulsion system.
ESAElectric propulsion has been regarded as one of the top ten cutting-edge technologies in the future.France is developing a steady-state plasma thruster, and ESA is preparing to apply a xenon ion thruster.ESA launches to the moonSMART－1One of the goals of the detector is to verify how to use ion propulsion technology to send future detectors into orbit around Mercury.
Russia's steady state plasma thruster has been applied in practice.Japan's arc heated thruster has passed in orbit test on a space free aircraft.
The research object of international electric propulsion has also expanded to some propulsion schemes adopting new working principles, such asMicromachining processMolded micro ionizer, usingPlasmaGasfusionThruster, etc.Most of these projects have received financial support from the government and large companies.
Nuclear propulsion rocket
Nuclear Propulsion Rocket Imagination
International research and development of nuclear propulsion technology has also emerged.The maximum speed increment provided by the nuclear propulsion rocket can reach 22 kilometers per second, which can greatly shorten the time for the probe to reach the moon.Using nuclear propulsion rockets, the detector arrivesSaturnIt only takes 3 years to fly, while the traditional spacecraft takes 7 years.The nuclear propulsion rocket is very safe and conducive to environmental protection, which is contrary to people's usual imagination, because when launching a nuclear rocket,radioactivityNot strong.The space probe with nuclear booster can be used as the head of ordinary chemical rocketPayloadIs launched when the payload entersEarth's high orbit(i.e. more than 800 km),nuclear reactorstart-up.
manufactureNuclear rocketThe technology needed for engines is not out of reach.The United States has designed a small nuclear powered rocket engine, called the micro nuclear reactor engine, which will take about 6 to 7 years to produce.NASA said that what it wants to do in lunar exploration technology is to accelerate the research and development of new propulsion technologies, including nuclear propulsion.In the draft budget of NASA for fiscal year 2003, 46.5 million dollars were used for nuclear propulsion research;$79 million was spent on spacecraft nuclear reactor development.
On the MoonprobeIn China, the requirements of shortening the time to reach the moon and enabling observation satellites to carry more observation instruments with less propellant will make efficient propulsion technologies such as electric propulsion and nuclear propulsion become the most important technologies and develop faster.
Development trend
Announce
edit
Miniaturization and portability
Small ion thruster
High efficiency energy conversion technology will move towards small and lightsolar cellDirection development.In terms of transmission technology, microwave or laser energy transmission technology will be developed in the future, includingLunar probe, energy transmission from energy stations on the moon to lunar probes, etc.
As traditional control technologies are increasingly difficult to meet the requirements of diversity of spacecraft lunar exploration missions and high performance indicators of attitude control and orbit control, advanced space faring countries began to develop spacecraft intelligent autonomous technology as early as the 1980s, and gradually increased their investment in intelligent autonomous technology in their space exploration plans.
On orbit intelligent autonomous technology
Ion thruster structure
ESAThe research on on orbit intelligent autonomous technology was carried out earlier.NASA's "New Prosperity" program puts intelligent and autonomous technology in the first place, aiming to develop autonomous spacecraft and make it deeply dependent.Space research institutions in Russia and Japan have also carried out research and development work in terms of independent technology.The Indian aerospace industry also attaches great importance to the development of software with independent functions.
Advanced aerospace countries attach great importance to the intelligent autonomous technology of detectors at all levels of "strategic planning → research and development → model application".They often develop in accordance with the three-step process of "taking one step, looking at one step, thinking about one step", that is, using advanced and mature technologies to do the current thing, while vigorously developing and testing the next advanced technology, and at the same time thinking of further needs to make strategic plans for technological development in advance.
