The gridded ion thruster is a common design for ion thrusters, a highly efficient low-thrust spacecraft propulsion method running on electrical power by using high-voltage grid electrodes to accelerate ions with electrostatic forces.
The gridded ion thruster is a common design for ion thrusters, a highly efficient low-thrust spacecraft propulsion method running on electrical power by using high-voltage grid electrodes to accelerate ions with electrostatic forces.
The ion engine was first demonstrated by German-born NASA scientist Ernst Stuhlinger, [1] and developed in practical form by Harold R. Kaufman at NASA Lewis (now Glenn) Research Center from 1957 to the early 1960s.
The use of ion propulsion systems were first demonstrated in space by the NASA Lewis "Space Electric Rocket Test" (SERT) I and II. [2] These thrusters used mercury as the reaction mass. The first was SERT-1, launched July 20, 1964, which successfully proved that the technology operated as predicted in space. The second test, SERT-II, launched on February 3, 1970, [3] [4] verified the operation of two mercury ion engines for thousands of running hours. [5] Despite the demonstration in the 1960s and 70s, though, they were rarely used before the late 1990s.
NASA Glenn continued to develop electrostatic gridded ion thrusters through the 1980s, developing the NASA Solar Technology Application Readiness (NSTAR) engine, that was used successfully on the Deep Space 1 probe, the first mission to fly an interplanetary trajectory using electric propulsion as the primary propulsion. It later flew on the Dawn asteroid mission.
Hughes Aircraft Company (now L-3 ETI) has developed the XIPS (Xenon Ion Propulsion System) for performing station keeping on its geosynchronous satellites (more than 100 engines flying).[ citation needed ] NASA is currently[ clarification needed ] working on a 20–50 kW electrostatic ion thruster called HiPEP which will have higher efficiency, specific impulse, and a longer lifetime than NSTAR.[ citation needed ]
In 2006, Aerojet completed testing of a prototype NEXT ion thruster. [6]
Beginning in the 1970s, radio-frequency ion thrusters were developed at Giessen University and ArianeGroup. RIT-10 engines are flying on the EURECA and ARTEMIS. Qinetiq (UK) has developed the T5 and T6 engines (Kaufman type), used on the GOCE mission (T5) and the BepiColombo mission (T6). From Japan, the µ10, using microwaves, flew on the Hayabusa mission.[ citation needed ]
In 2021, DART launched carrying a NEXT-C xenon ion thruster.
In 2021, ThrustMe reported satellite orbit changes using their NPT30-I2 iodine ion thruster. [7] [8] [9]
Propellant atoms are injected into the discharge chamber and are ionized, forming a plasma.
There are several ways of producing the electrostatic ions for the discharge chamber:
Related to the electrostatic ion production method is the need for a cathode and power supply requirements. Electron bombardment thrusters require at the least, power supplies to the cathode, anode and chamber. RF and microwave types require an additional power supply to the rf generator, but no anode or cathode power supplies.
The positively charged ions diffuse towards the chamber's extraction system (2 or 3 multi-aperture grids). After ions enter the plasma sheath at a grid hole, they are accelerated by the potential difference between the first and second grids (called the screen and accelerator grids, respectively). The ions are guided through the extraction holes by the powerful electric field. The final ion energy is determined by the potential of the plasma, which generally is slightly greater than the screen grids' voltage.
The negative voltage of the accelerator grid prevents electrons of the beam plasma outside the thruster from streaming back to the discharge plasma. This can fail due to insufficient negative potential in the grid, which is a common ending for ion thrusters' operational life. The expelled ions propel the spacecraft in the opposite direction, according to Newton's 3rd law. Lower-energy electrons are emitted from a separate cathode, called the neutralizer, into the ion beam to ensure that equal amounts of positive and negative charge are ejected. Neutralizing is needed to prevent the spacecraft from gaining a net negative charge, which would attract ions back toward the spacecraft and cancel the thrust.
The ion optics are constantly bombarded by a small amount of secondary ions and erode or wear away, thus reducing engine efficiency and life. Several techniques were used to reduce erosion; most notable was switching to a different propellant. Mercury or caesium atoms were used as propellants during tests in the 1960s and 1970s, but these propellants adhered to, and eroded the grids. Xenon atoms, on the other hand, are far less corrosive, and became the propellant of choice for virtually all ion thruster types. NASA has demonstrated continuous operation of NSTAR thruster for over 16,000 hours (1.8 years) and NEXT thruster for over 48,000 hours (5.5 years). [10] [11]
In the extraction grid systems, minor differences occur in the grid geometry and the materials used. This may have implications for the grid system operational lifetime.
Electrostatic ion thrusters have also achieved a specific impulse of 30–100 kN·s/kg, or 3,000 to 10,000 s, better than most other ion thruster types. Electrostatic ion thrusters have accelerated ions to speeds reaching 100 km/s.
In January 2006, the European Space Agency, together with the Australian National University, announced successful testing of an improved electrostatic ion engine, the Dual-Stage 4-Grid (DS4G), that showed exhaust speeds of 210 km/s, reportedly four times higher than previously achieved, allowing for a specific impulse which is four times higher. Conventional electrostatic ion thrusters possess only two grids, one high voltage and one low voltage, which perform both the ion extraction and acceleration functions. However, when the charge differential between these grids reaches around 5 kV, some of the particles extracted from the chamber collide with the low voltage grid, eroding it and compromising the engine's longevity. This limitation is successfully bypassed when two pairs of grids are used. The first pair operates at high voltage, possessing a voltage differential of around 3 kV between them; this grid pair is responsible for extracting the charged propellant particles from the gas chamber. The second pair, operating at low voltage, provides the electrical field that accelerates the particles outwards, creating thrust. Other advantages to the new engine include a more compact design, allowing it to be scaled up to higher thrusts, and a narrower, less divergent exhaust plume of 3 degrees, which is reportedly five times narrower than previously achieved. This reduces the propellant needed to correct the orientation of the spacecraft due to small uncertainties in the thrust vector direction. [12]
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric entry.
In spacecraft propulsion, a Hall-effect thruster (HET) is a type of ion thruster in which the propellant is accelerated by an electric field. Hall-effect thrusters are sometimes referred to as Hall thrusters or Hall-current thrusters. Hall-effect thrusters use a magnetic field to limit the electrons' axial motion and then use them to ionize propellant, efficiently accelerate the ions to produce thrust, and neutralize the ions in the plume. The Hall-effect thruster is classed as a moderate specific impulse space propulsion technology and has benefited from considerable theoretical and experimental research since the 1960s.
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or MPD arcjet.
A pulsed plasma thruster (PPT), also known as a plasma jet engine, is a form of electric spacecraft propulsion. PPTs are generally considered the simplest form of electric spacecraft propulsion and were the first form of electric propulsion to be flown in space, having flown on two Soviet probes starting in 1964. PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy.
A pulsed inductive thruster (PIT) is a form of ion thruster, used in spacecraft propulsion. It is a plasma propulsion engine using perpendicular electric and magnetic fields to accelerate a propellant with no electrode.
Thruster may refer to:
Field-emission electric propulsion (FEEP) is an advanced electrostatic space propulsion concept, a form of ion thruster, that uses a liquid metal as a propellant – usually either caesium, indium, or mercury.
A propellant is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the engine that expels the propellant is called a reaction engine. Although technically a propellant is the reaction mass used to create thrust, the term "propellant" is often used to describe a substance which contains both the reaction mass and the fuel that holds the energy used to accelerate the reaction mass. For example, the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, although the propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two distinct concepts.
Solar electric propulsion (SEP) refers to the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft designs by the European Space Agency (ESA), the JAXA, Indian Space Research Organisation (ISRO) and NASA. SEP has a significantly higher specific impulse than chemical rocket propulsion, thus requiring less propellant mass to be launched with a spacecraft. The technology has been evaluated for missions to Mars.
The helicon double-layer thruster is a prototype spacecraft propulsion engine. It was created by Australian scientist Christine Charles, based on a technology invented by Professor Rod Boswell, both of the Australian National University.
A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast with ion thruster engines, which generate thrust through extracting an ion current from the plasma source, which is then accelerated to high velocities using grids/anodes. These exist in many forms. However, in the scientific literature, the term "plasma thruster" sometimes encompasses thrusters usually designated as "ion engines".
Spacecraft electric propulsion is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generate thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics.
SERT-1 was a NASA probe used to test electrostatic ion thruster design and was built by NASA's Lewis Research Center. SERT-1 was the first spacecraft to utilize ion engine design. It was launched on July 20, 1964 on a Scout rocket. It carried two electric propulsion engines; of the two, the first, an electron-bombardment ion engine was run for a total of 31 minutes and 16 seconds. This was the first time that an ion engine of any type had been operated in space, and demonstrated that the neutralizer worked as predicted.
The NASA Evolutionary Xenon Thruster (NEXT) project at Glenn Research Center is a gridded electrostatic ion thruster about three times as powerful as the NSTAR used on Dawn and Deep Space 1 spacecraft. It was used in DART, launched in 2021.
Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.
The NASA Solar Technology Application Readiness (NSTAR) is a type of spacecraft ion thruster called electrostatic ion thruster. It is a highly efficient low-thrust spacecraft propulsion running on electrical power generated by solar arrays. It uses high-voltage electrodes to accelerate ions with electrostatic forces.
A thruster is a spacecraft propulsion device used for orbital station-keeping, attitude control, or long-duration, low-thrust acceleration, often as part of a reaction control system. A vernier thruster or gimbaled engine are particular cases used on launch vehicles where a secondary rocket engine or other high thrust device is used to control the attitude of the rocket, while the primary thrust engine is fixed to the rocket and supplies the principal amount of thrust.
Iodine Satellite (iSat) is a technology demonstration satellite of the CubeSat format that will undergo high changes in velocity from a primary propulsion system by using a Hall thruster with iodine as the propellant. The spacecraft will also perform changes of its orbital altitude, and demonstrate deorbit capabilities to reduce space junk.
Advanced Electric Propulsion System (AEPS) is a solar electric propulsion system for spacecraft that is being designed, developed and tested by NASA and Aerojet Rocketdyne for large-scale science missions and cargo transportation. The first application of the AEPS is to propel the Power and Propulsion Element (PPE) of Gateway, to be launched in 2024. The PPE module is built by Maxar space solutions in Palo Alto, California. Two identical AEPS engines would consume 25 kW being generated by the roll-out solar array (ROSA) assembly, which can produce over 60 kW of power.
Both atomic and molecular iodine ions are accelerated by high-voltage grids to generate thrust, and a highly collimated beam can be produced with substantial iodine dissociation.
For the first time ever, a telecommunications satellite has used an iodine propellant to change its orbit around Earth. The small but potentially disruptive innovation could help to clear the skies of space junk, by enabling tiny satellites to self-destruct cheaply and easily at the end of their missions, by steering themselves into the atmosphere where they would burn up.
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