An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by the acceleration of ions. Electric propulsion is a form of Spacecraft propulsion used in Outer space. Spacecraft propulsion is any method used to change the velocity of Spacecraft and artificial Satellites There are many different methods An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Ion thrusters can be characterized by how they accelerate the ions, with either electrostatic or electromagnetic forces being used. Electrostatic ion thrusters use the Coulomb Force and accelerate the ions in the direction of the electric field. ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form Electromagnetic ion thrusters use the Lorentz Force to accelerate the ions. In Physics, the Lorentz force is the Force on a Point charge due to Electromagnetic fields It is given by the following equation Note that the term "ion thruster" frequently denotes the electrostatic or gridded ion thrusters only.
The thrust created in ion thrusters is very small compared to conventional chemical rockets, but a very high specific impulse, or propellant efficiency, is obtained. Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. A rocket engine is a Jet engine that uses only Propellant mass for forming its high speed propulsive jet. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines
Due to their relatively high power needs, given the specific power of power supplies, and the requirement of an environment void of other ionized particles, ion thrusters are currently only practical for in-space propulsion applications.
The principles of ion thrusters go back to the concepts developed by the German/Austrian physicist Hermann Oberth which were published in his famous 1929 work "Wege zur Raumschiffahrt” (Ways to Spaceflight). Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Austria (Österreich ( officially the Republic of Austria (Republik Österreich A physicist is a Scientist who studies or practices Physics. Physicists study a wide range of physical phenomena in many branches of physics spanning Hermann Julius Oberth ( June 25, 1894 &ndash December 28, 1989) was a Austro-Hungarian -born German ( Transylvanian A whole chapter was devoted to power and electric propulsion. There he explained his thoughts on the mass savings of electric propulsion, predicted its use in spacecraft propulsion and attitude control, and advocated electrostatic acceleration of charged gases. Spacecraft propulsion is any method used to change the velocity of Spacecraft and artificial Satellites There are many different methods The attitude of a body is its orientation as perceived in a certain Frame of reference; providing a vector along which a spacecraft is pointing is a description of its attitude 
The first working ion thruster was built by Harold R. Kaufman in 1959 at the NASA Glenn facilities. Harold R Kaufman is an American Physicist, noted for his development of Ion thrusters for NASA during the 1950s and '60s It was similar to the general design of a gridded electrostatic ion thruster with mercury as its fuel. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Suborbital tests of the engine followed during the 1960's and in 1964 the engine was sent into a suborbital flight aboard the Space Electric Rocket Test 1 (SERT 1). SERT-1 (Space Electric Rocket Test was a NASA probe used to test Ion engine design and was built by NASA's Lewis Research Center. It successfully operated for the planned 31 minutes before falling back to Earth. 
The Hall effect thruster was studied independently in the U. In Spacecraft propulsion, a Hall thruster is a type of Ion thruster in which the Propellant is accelerated by an electric field S. and the USSR in the 1950s and 60s. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 However, the concept of a Hall thruster was only developed into an efficient propulsion device in the former Soviet Union, whereas in the U. S. , scientists focused instead on developing gridded ion thrusters. Hall effect thrusters were operated on Soviet satellites since 1972. Until the 1990s they were mainly used for satellite stabilization in North-South and in East-West directions. Some 100-200 engines completed their mission on Soviet and Russian satellites until the late 1990s. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending  Soviet thruster design was introduced to the West in 1992 after a team of electric propulsion specialists, under the support of the Ballistic Missile Defense Organization, visited Soviet laboratories. The Ballistic Missile Defense Organization (or BMDO) was an agency of the United States Department of Defense.
Ion thrusters utilize beams of ions (electrically charged atoms or molecules) to create thrust in accordance with Newton's third law. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. Newton's laws of motion are three Physical laws which provide relationships between the Forces acting on a body and the motion of the The method of accelerating the ions varies, but all designs take advantage of the charge/mass ratio of the ions. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object This ratio means that relatively small potential differences can create very high exhaust velocities. This reduces the amount of reaction mass or fuel required, but increases the amount of specific power required compared to chemical rockets. Working mass is a mass against which a system operates in order to produce Acceleration. In Physics, power (symbol P) is the rate at which work is performed or energy is transmitted or the amount of energy required or expended for Spacecraft propulsion is any method used to change the velocity of Spacecraft and artificial Satellites There are many different methods Ion thrusters are therefore able to achieve extremely high specific impulses. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines The drawback of the low thrust is low spacecraft acceleration because the mass of current electric power units is directly correlated with the amount of power given. Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. This low thrust makes ion thrusters unsuited for launching spacecraft into orbit, but they are ideal for in-space propulsion applications.
Various ion thrusters have been designed and they all generally fit under two categories. The thrusters are categorized as either electrostatic or electromagnetic. Electrostatics is the branch of Science that deals with the Phenomena arising from what seems to be stationary Electric charges Since Classical Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of The main difference is how the ions are accelerated.
Gridded electrostatic ion thrusters commonly utilize xenon gas. The electrostatic ion thruster is a kind of design for Ion thrusters (a kind of highly-efficient low-thrust Spacecraft propulsion running on electrical power This gas has no charge and is ionized by bombarding it with energetic electrons. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons These electrons can be provided from a hot cathode filament and accelerated in the electrical field of the cathode fall to the anode (Kaufman type ion thruster). A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device An electrical filament is a thread of Metal, usually Tungsten, which is used to convert Electricity into light in Incandescent light bulbs (as developed Alternatively, the electrons can be accelerated by the oscillating electric field induced by an alternating magnetic field of a coil, which results in a self-sustaining discharge and omits any cathode (radiofrequency ion thruster).
The positively charged ions are extracted by an extraction system consisting of 2 or 3 multi-aperture grids. After entering the grid system via the plasma sheath the ions are accelerated due to the potential difference between the first and second grid (named screen and accelerator grid) to the final ion energy of typically 1-2 keV, thereby generating the thrust.
Ion thrusters emit a beam of positive charged xenon ions only. In order to avoid the charging-up of the spacecraft another cathode, placed near the engine, emits additional electrons (basically the electron current is the same as the ion current) into the ion beam. A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device This also prevents the beam of ions from returning to the spacecraft and thereby cancelling the thrust. 
Gridded electrostatic ion thruster research (past/present):
Hall effect thrusters accelerate ions with the use of an electric potential maintained between a cylindrical anode and a negatively charged plasma which forms the cathode. In Spacecraft propulsion, a Hall thruster is a type of Ion thruster in which the Propellant is accelerated by an electric field The bulk of the propellant (typically xenon or bismuth gas) is introduced near the anode, where it becomes ionised, and the ions are attracted towards the cathode, they accelerate towards and through it, picking up electrons as they leave to neutralise the beam and leave the thruster at high velocity. Bismuth (ˈbɪzməθ is a Chemical element that has the symbol Bi and Atomic number 83
The anode is at one end of a cylindrical tube, and in the center is a spike which is wound to produce a radial magnetic field between it and the surrounding tube. The ions are largely unaffected by the magnetic field, since they are too massive. However, the electrons produced near the end of the spike to create the cathode are far more affected and are trapped by the magnetic field, and held in place by their attraction to the anode. Some of the electrons spiral down towards the anode, circulating around the spike in a Hall current. When they reach the anode they impact the uncharged propellant and cause it to be ionised, before finally reaching the anode and closing the circuit. 
Field Emission Electric Propulsion (FEEP) thrusters use a very simple system of accelerating liquid metal ions to create thrust. Field Emission Electric Propulsion ( FEEP) is an advanced electrostatic propulsion concept a form of Ion thruster, that uses liquid Metal (usually either Most designs use either caesium or indium as the propellant. The design consists of a small propellant reservoir that stores the liquid metal, a very small slit that the liquid flows through, and then the accelerator ring. Caesium and indium are used due to their high atomic weights, low ionization potentials, and low melting points. Once the liquid metal reaches the inside of the slit in the emitter, an electric field applied between the emitter and the accelerator ring causes the liquid metal to become unstable and ionize. This creates a positive ion, which can then be accelerated in the electric field created by the emitter and the accelerator ring. These positively charged ions are then neutralized by an external source of electrons in order to prevent charging of the spacecraft hull. 
Pulsed Inductive Thrusters (PIT) use pulses of thrust instead of one continuous thrust, and have the ability to run on power levels in the order of Megawatts (MW). PITs consist of a large coil encircling a cone shaped tube that emits the propellant gas as shown in the diagram. Ammonia is the gas commonly used in PIT engines. For each pulse of thrust the PIT gives, a large charge first builds up in a group of capacitors behind the coil and is then released. This creates a current that moves circularly in the direction of jθ as seen in the diagram. The current then creates a magnetic field in the outward radial direction (Br), which then creates a current in the ammonia gas that has just been released in the opposite direction of the original current. This opposite current ionizes the ammonia and these positively charged ions are accelerated away from the PIT engine due to the electric field jθ crossing with the magnetic field Br, which is due to the Lorentz Force. In Physics, the Lorentz force is the Force on a Point charge due to Electromagnetic fields It is given by the following equation 
Magnetoplasmadynamic (MPD) thrusters and Lithium Lorentz Force Accelerator (LiLFA) thrusters use roughly the same idea with the LiLFA thruster building off of the MPD thruster. The Magnetoplasmadynamic (MPD thruster (MPDT is a form of Electric propulsion (a subdivision of Spacecraft propulsion) which uses the Lorentz force Hydrogen, argon, ammonia, and nitrogen gas can be used as propellant. The gas first enters the main chamber where it is ionized into plasma by the electric field between the anode and the cathode. This plasma then conducts electricity between the anode and the cathode. This new current creates a magnetic field around the cathode which crosses with the electric field, thereby accelerating the plasma due to the Lorentz Force. The LiLFA thruster uses the same general idea as the MPD thruster, except for two main differences. The first difference is that the LiLFA uses lithium vapor, which has the advantage of being able to be stored as a solid. The other difference is that the cathode is replaced by multiple smaller cathode rods packed into a hollow cathode tube. The cathode in the MPD thruster is easily corroded due to constant contact with the plasma. In the LiLFA thruster the lithium vapor is injected into the hollow cathode and is not ionized to its plasma form/corrode the cathode rods until it exits the tube. The plasma is then accelerated using the same Lorentz Force.  
Electrodeless Plasma Thrusters have two unique features, the removal of the anode and cathode electrodes and the ability to throttle the engine. The electrodeless plasma thruster is a spacecraft propulsion engine The removal of the electrodes takes away the factor of erosion which limits lifetime on other ion engines. Neutral gas is first ionized by electromagnetic waves and then transferred to another chamber where it is accelerated by an oscillating electric and magnetic field, also known as the ponderomotive force. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Physics, a ponderomotive force is a nonlinear Force that a charged particle experiences in a rapidly oscillating inhomogeneous electric or This separation of the ionization and acceleration stage give the engine the ability to throttle the speed of propellant flow, which then changes the thrust magnitude and specific impulse values. 
The following table compares actual test data of some ion thrusters:
|NSTAR||Xenon||2. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines 3||3300||92|
|RIT 22||Xenon||5||3000-6000||50 - 200|
|FEEP||Liquid Caesium||6x10-5-0. 06||6000-10000||0. 001-1|
The following thrusters are highly experimental and have been tested only in pulse mode.
A major limiting factor of ion thrusters is their small thrust, which however is generated at a high propellant efficiency (mass utilisation, specific impulse). Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines The efficiency comes from the high exhaust velocity, which in turn demands a lot of energy, and the performance is ultimately limited by the available spacecraft power.
The low thrust requires ion thrusters to provide continuous thrust for a very long time in order to achieve the needed change in velocity (delta-v) for a particular mission. In Astrodynamics, the term delta-v, literally "change in velocity" (see symbol delta) has a specific meaning it is a Scalar which takes To achieve these delta-vs, ion thrusters are designed to last for periods of weeks to years.
In practice the lifetime of ion thrusters is limited by several processes.
In the electrostatic gridded ion thruster design, charge-exchange ions produced by the beam ions with the neutral gas flow can be accelerated towards the negatively biased accelerator grid and cause grid erosion. End-of-life is reached when either a structural failure of the grid occurs or the holes in the accelerator grid become so large that the ion extraction is largely affected (e. g. by the occurrence of electron backstreaming). Grid erosion cannot be avoided and is the major lifetime-limiting factor. By a thorough grid design and material selection lifetimes of 20. 000 hours and far beyond are reached which is sufficient to fulfill current space missions. A test of the NASA Solar electric propulsion Technology Application Readiness (NSTAR) electrostatic ion thruster resulted in 30,472 hours (roughly 3. 5 years) of continuous thrust at maximum power. The test was concluded prior to any failure and test results showed the engine was not approaching failure either. 
The Hall thrusters suffer from very strong erosion of the ceramic discharge chamber. Due to the rather high discharge voltages of up to 1000V energetic ions can impinge to the chamber walls and erode material. Lifetimes of a few thousand hours are reached.
Ionisation energy represents a very large percentage of the energy needed to run ion drives. The ideal propellant for ion drives is thus a propellant molecule or atom with a high mass/ionisation energy ratio. In addition, the propellant should not cause erosion of the thruster to any great degree to permit long life; and should not contaminate the vehicle.
Many current designs use xenon gas due to its low ionisation, reasonably high atomic number, inert nature, and low erosion. Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. However, xenon is globally in short supply and very expensive.
Older designs used mercury, but this is toxic and expensive, and tended to contaminate the vehicle with the metal. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum
Other propellants such as bismuth show promise and are areas of research, particularly for gridless designs such as Hall effect thrusters. Bismuth (ˈbɪzməθ is a Chemical element that has the symbol Bi and Atomic number 83
Ion thrusters have many applications for in-space propulsion. The best applications of the thrusters make use of the long lifetime when significant thrust is not needed. Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. Examples of this include orbit transfers, attitude adjustments, drag compensation for low earth orbits, and ultra fine adjustments for more scientific missions. The attitude of a body is its orientation as perceived in a certain Frame of reference; providing a vector along which a spacecraft is pointing is a description of its attitude In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km Ion thrusters can also be used for interplanetary and deep space missions where time is not crucial. Continuous thrust over a very long time can potentially build up a larger velocity than traditional chemical rockets. 
Of all the electric thrusters, ion thrusters have been the most seriously considered commercially and academically in the quest for interplanetary missions and orbit raising maneuvers. An Interplanetary Mission is a voyage or trip through space involving more than one planet Ion thrusters are seen as the best solution for these missions as they require very high change in velocity overall that can be built up over long periods of time. Several spacecraft have operated with this technology.
The first was SERT (Space Electric Rocket Test) which tested two mercury ion engines for thousands of running hours in the 1970s. 
NASA has developed an ion thruster called NSTAR for use in their interplanetary missions. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program This thruster was tested in the highly successful space probe Deep Space 1, launched in 1998. Deep Space 1 is a Spacecraft launched on 24 October 1998 as part of NASA 's New Millennium program. Hughes has developed the XIPS (Xenon Ion Propulsion System) for performing stationkeeping on geosynchronous satellites. Hughes Aircraft Company was a major aerospace and defense company founded by Howard Hughes. A geosynchronous satellite is a Satellite whose orbital track on the Earth repeats regularly over points on the Earth over time These are electrostatic ion thrusters and work by a different principle than Hall effect thrusters. The electrostatic ion thruster is a kind of design for Ion thrusters (a kind of highly-efficient low-thrust Spacecraft propulsion running on electrical power
On 12 July 2001, the European Space Agency failed to launch their Artemis telecommunication satellite, and left it in a decaying orbit. Events 1191 - Saladin 's garrison surrenders ending the two-year Siege of Acre. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member Artemis is a Geostationary earth orbit satellite (GEOS for telecommunications The satellite's chemical propellant supply was sufficient to transfer it to a semi-stable orbit, and over the next 18 months the experimental onboard ion propulsion system RIT-10 (intended for secondary stationkeeping and maneuvering) was utilized to transfer it to a geostationary orbit. 
The Japanese space agency's Hayabusa, which was launched in 2003 and successfully rendezvoused with the asteroid 25143 Itokawa and remained in close proximity for many months to collect samples and information, is powered by four xenon Ion Engines. is an Unmanned space mission led by the Japan Aerospace Exploration Agency to return a sample of material from a small Near-Earth asteroid named TemplateInfobox Planet. --> 25143 Itokawa (ˌiːtoʊˈkɑːwə Japanese イトカワ from 糸川 It is using xenon ions generated by microwave ECR, and a Carbon / Carbon-composite material for acceleration grid which is resistant to erosion. 
The Hall effect thruster is a type of ion thruster that has been used for decades for station keeping by the Soviet Union and is now also applied in the West: the European Space Agency's satellite Smart 1, launched in 2003, used it (Snecma PPS-1350-G). In Spacecraft propulsion, a Hall thruster is a type of Ion thruster in which the Propellant is accelerated by an electric field In Astrodynamics orbital station-keeping is a term used to describe a particular set of Orbital maneuvers used to keep a spacecraft in assigned Orbit The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member SMART-1 was a Swedish -designed European Space Agency Satellite that Orbited around the Moon. PPS-1350 is a Hall effect thruster, a kind of ion propulsion system for Spacecraft. This satellite completed its mission on 3 September 2006, in a controlled collision on the Moon's surface, after a trajectory deviation to be able to see the 3 meter crater the impact created on the visible side of the moon. Events 36 BC - In the Battle of Naulochus, Marcus Vipsanius Agrippa, Admiral of Octavian, defeats Sextus Pompeius Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar.
Dawn was launched on 27 September 2007 to explore the dwarf planet Ceres and the asteroid Vesta. Dawn, launched on September 27 2007 is a Robotic spacecraft being sent by NASA on a Space exploration mission to the two most massive members Events 489 - Odoacer attacks Theodoric at the Battle of Verona and is defeated again Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Ceres (ˈsɪəriːz TemplateInfobox Planet. --> 4 Vesta (ˈvɛstə Vesta is the second most massive object in the Asteroid belt To cruise from Earth to its targets it will use three Deep Space 1 heritage Xenon ion thrusters (firing only one at a time) to take it in a long outward spiral. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Deep Space 1 is a Spacecraft launched on 24 October 1998 as part of NASA 's New Millennium program. An extended mission in which Dawn explores other asteroids after Ceres is also possible. Dawn's ion drive is capable of accelerating from 0 to 60 mph (97 km/h) in 4 days. 
LISA Pathfinder is an ESA spacecraft to be launched in 2009. LISA Pathfinder is the revised name for SMART-2 an ESA space probe to be launched in 2009. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member It will not use ion thrusters as its primary propulsion system, but will use both colloid thrusters and FEEP for very precise attitude control—the low thrusts of these propulsion devices make it possible to move the spacecraft incremental distances very accurately. A colloid thruster is a type of thruster which uses electrostatic acceleration of charged liquid droplets for propulsion It is a test for the possible LISA mission.
SPACE odyssey DVD(episode 6, boldly go)