10/28/10 3:18 PMIon thruster - Wikipedia, the free encyclopedia

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NASA's 2.3 kW NSTAR ion thruster during a hot fire test at

the Jet Propulsion Laboratory on the Deep Space 1

spacecraft.

Ion thruster

From Wikipedia, the free encyclopedia

An ion thruster is a form of electric propulsionused for spacecraft propulsion that creates thrustby accelerating ions. Ion thrusters arecategorized by how they accelerate the ions,using either electrostatic or electromagneticforce. Electrostatic ion thrusters use theCoulomb force and accelerate the ions in thedirection of the electric field. Electromagneticion thrusters use the Lorentz force to acceleratethe ions. Note that the term "ion thruster"frequently denotes the electrostatic or griddedion thrusters only.

The thrust created in ion thrusters is very smallcompared to conventional chemical rockets, buta very high specific impulse, or propellantefficiency, is obtained. This high propellantefficiency is achieved through the very frugalpropellant consumption of the ion thrusterpropulsion system. They do, however, use alarge amount of power. Given the practicalweight of suitable power sources, theaccelerations given by these types of thrusters is of the order of one thousandth of standard gravity.

Due to their relatively high power needs, given the specific power of power supplies, and the requirement ofan environment void of other ionized particles, ion thrust propulsion is currently practical only in outer space.

Contents

1 Origins

2 General description

3 Electrostatic ion thrusters

3.1 Gridded electrostatic ion thrusters

3.2 Hall effect thrusters

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3.3 Field emission electric propulsion (FEEP)

4 Electromagnetic thrusters

4.1 Pulsed inductive thrusters (PIT)

4.2 Magnetoplasmadynamic (MPD) / lithium Lorentz force accelerator (LiLFA)

4.3 Electrodeless plasma thrusters

4.4 Electrothermal thrusters

4.5 Helicon double layer thruster

5 Comparisons

6 Lifetime

7 Propellants

8 Applications

9 Missions

9.1 SERT

9.2 Deep Space 1

9.3 Artemis

9.4 Hayabusa

9.5 Smart 1

9.6 Dawn

9.7 GOCE

9.8 GSAT-4

9.9 LISA Pathfinder

10 See also

11 Articles

12 References

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Soviet and Russian Hall effect

thrusters

Origins

The official father of the concept of electric propulsion is Konstantin Tsiolkovsky as he is the first to publishmention of the idea in 1911.[1] However, the first documented instance where the possibility of electricpropulsion is considered is found in Robert H. Goddard's handwritten notebook in an entry dated 6 September1906.[2] The first experiments with ion thrusters were carried out by Goddard at Clark University from 1916–1917.[3] The technique was recommended for near-vacuum conditions at high altitude, but thrust wasdemonstrated with ionized air streams at atmospheric pressure. The idea appeared again in Hermann Oberth's"Wege zur Raumschiffahrt” (Ways to Spaceflight), published in 1923, where he explained his thoughts on themass savings of electric propulsion, predicted its use in spacecraft propulsion and attitude control, andadvocated electrostatic acceleration of charged gases.[1]

A working ion thruster was built by Harold R. Kaufman in 1959 at the NASA Glenn Research Centerfacilities. It was similar to the general design of a gridded electrostatic ion thruster with mercury as its fuel.Suborbital tests of the engine followed during the 1960s and in 1964 the engine was sent into a suborbitalflight aboard the Space Electric Rocket Test 1 (SERT 1). It successfully operated for the planned 31 minutesbefore falling back to Earth.[4]

The Hall effect thruster was studied independently in the U.S. and theUSSR in the 1950s and 60s. However, the concept of a Hall thrusterwas only developed into an efficient propulsion device in the formerSoviet Union, whereas in the U.S., scientists focused instead ondeveloping gridded ion thrusters. Hall effect thrusters were operated onSoviet satellites since 1972. Until the 1990s they were mainly used forsatellite stabilization in North-South and in East-West directions. Some100-200 engines completed their mission on Soviet and Russiansatellites until the late 1990s.[5] Soviet thruster design was introducedto the West in 1992 after a team of electric propulsion specialists, underthe support of the Ballistic Missile Defense Organization, visited Sovietlaboratories.

General description

Ion thrusters use beams of ions (electrically charged atoms ormolecules) to create thrust in accordance with momentum conservation.The method of accelerating the ions varies, but all designs takeadvantage of the charge/mass ratio of the ions. This ratio means thatrelatively small potential differences can create very high exhaustvelocities. This reduces the amount of reaction mass or fuel required, but increases the amount of specificpower required compared to chemical rockets. Ion thrusters are therefore able to achieve extremely highspecific impulses. The drawback of the low thrust is low spacecraft acceleration because the mass of currentelectric power units is directly correlated with the amount of power given. This low thrust makes ion thrustersunsuited for launching spacecraft into orbit, but they are ideal for in-space propulsion applications.

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Figure 2: A diagram of how a gridded

electrostatic ion engine (Kaufman type) works

Various ion thrusters have been designed and they all generally fit under two categories. The thrusters arecategorized as either electrostatic or electromagnetic. The main difference is how the ions are accelerated.

Electrostatic ion thrusters use the Coulomb force and are categorized as accelerating the ions in the

direction of the electric field.

Electromagnetic ion thrusters use the Lorentz force to accelerate the ions.

Electrostatic ion thrusters

Gridded electrostatic ion thrusters

Gridded electrostatic ion thrusters commonly utilize xenongas. This gas has no charge and is ionized by bombarding itwith energetic electrons. These electrons can be providedfrom a hot cathode filament and accelerated in theelectrical field of the cathode fall to the anode (Kaufmantype ion thruster). Alternatively, the electrons can beaccelerated by the oscillating electric field induced by analternating magnetic field of a coil, which results in a self-sustaining discharge and omits any cathode (radiofrequencyion thruster).

The positively charged ions are extracted by an extractionsystem consisting of 2 or 3 multi-aperture grids. Afterentering the grid system via the plasma sheath the ions areaccelerated due to the potential difference between the firstand second grid (named screen and accelerator grid) to thefinal 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 charging-up the spacecraft,another cathode is placed near the engine, which emits electrons (basically the electron current is the same asthe ion current) into the ion beam. This also prevents the beam of ions from returning to the spacecraft andthereby cancelling the thrust.[4]

Gridded electrostatic ion thruster research (past/present):

NASA Solar electric propulsion Technology Application Readiness (NSTAR)

NASA’s Evolutionary Xenon Thruster (NEXT)

Nuclear Electric Xenon Ion System (NEXIS)

High Power Electric Propulsion (HiPEP)

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Schematic of a Hall Thruster

EADS Radio-Frequency Ion Thruster (RIT)

Dual-Stage 4-Grid (DS4G)[6][7]

Hall effect thrusters

Hall effect thrusters accelerate ions withthe use of an electric potential maintainedbetween a cylindrical anode and anegatively charged plasma which forms thecathode. The bulk of the propellant(typically xenon gas) is introduced near theanode, where it becomes ionized, and theions are attracted towards the cathode, theyaccelerate towards and through it, pickingup electrons as they leave to neutralize thebeam and leave the thruster at high velocity.

The anode is at one end of a cylindricaltube, and in the center is a spike which iswound to produce a radial magnetic fieldbetween it and the surrounding tube. Theions are largely unaffected by the magnetic field, since they are too massive. However, the electrons producednear the end of the spike to create the cathode are far more affected and are trapped by the magnetic field, andheld in place by their attraction to the anode. Some of the electrons spiral down towards the anode, circulatingaround the spike in a Hall current. When they reach the anode they impact the uncharged propellant and causeit to be ionized, before finally reaching the anode and closing the circuit.[8]

Field emission electric propulsion (FEEP)

Field emission electric propulsion (FEEP) thrusters use a very simple system of accelerating liquid metalions to create thrust. Most designs use either caesium or indium as the propellant. The design consists of asmall propellant reservoir that stores the liquid metal, a very small slit that the liquid flows through, and thenthe 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 fieldapplied 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 theaccelerator ring. These positively charged ions are then neutralized by an external source of electrons in orderto prevent charging of the spacecraft hull.[9][10]

Electromagnetic thrusters

Pulsed inductive thrusters (PIT)

Pulsed inductive thrusters (PIT) use pulses of thrust instead of one continuous thrust, and have the ability to

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run on power levels in the order of Megawatts (MW). PITs consist of a large coil encircling a cone shapedtube that emits the propellant gas as shown in the diagram. Ammonia is the gas commonly used in PITengines. For each pulse of thrust the PIT gives, a large charge first builds up in a group of capacitors behindthe coil and is then released. This creates a current that moves circularly in the direction of jθ as seen in thediagram. The current then creates a magnetic field in the outward radial direction (Br), which then creates acurrent in the ammonia gas that has just been released in the opposite direction of the original current. Thisopposite current ionizes the ammonia and these positively charged ions are accelerated away from the PITengine due to the electric field jθ crossing with the magnetic field Br, which is due to the Lorentz Force.[11]

Magnetoplasmadynamic (MPD) / lithium Lorentz force accelerator (LiLFA)

Magnetoplasmadynamic (MPD) thrusters and lithium Lorentz force accelerator (LiLFA) thrusters use roughlythe same idea with the LiLFA thruster building off of the MPD thruster. Hydrogen, argon, ammonia, andnitrogen gas can be used as propellant. The gas first enters the main chamber where it is ionized into plasmaby the electric field between the anode and the cathode. This plasma then conducts electricity between theanode and the cathode. This new current creates a magnetic field around the cathode which crosses with theelectric field, thereby accelerating the plasma due to the Lorentz Force. The LiLFA thruster uses the samegeneral idea as the MPD thruster, except for two main differences. The first difference is that the LiLFA useslithium vapor, which has the advantage of being able to be stored as a solid. The other difference is that thecathode is replaced by multiple smaller cathode rods packed into a hollow cathode tube. The cathode in theMPD thruster is easily corroded due to constant contact with the plasma. In the LiLFA thruster the lithiumvapor is injected into the hollow cathode and is not ionized to its plasma form/corrode the cathode rods until itexits the tube. The plasma is then accelerated using the same Lorentz Force.[12][13]

Electrodeless plasma thrusters

Electrodeless plasma thrusters have two unique features: the removal of the anode and cathode electrodes andthe ability to throttle the engine. The removal of the electrodes takes away the factor of erosion which limitslifetime on other ion engines. Neutral gas is first ionized by electromagnetic waves and then transferred toanother chamber where it is accelerated by an oscillating electric and magnetic field, also known as theponderomotive force. This separation of the ionization and acceleration stage give the engine the ability tothrottle the speed of propellant flow, which then changes the thrust magnitude and specific impulse values.[14]

Electrothermal thrusters

Electrothermal thrusters use electric power to accelerate propellant. There are several types:1. Resistojet2. Arcjet3. Microwave electrothermal thrusters4. Ion Cyclotron Heating thrusters (VASIMR)

Helicon double layer thruster

Main article: Helicon Double Layer Thruster

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A helicon double layer thruster is a type of plasma thruster, which ejects high velocity ionized gas to providethrust to a spacecraft. In this thruster design, gas is injected into a tubular chamber (the source tube) with oneopen end. Radio frequency AC power (at 13.56 MHz in the prototype design) is coupled into a speciallyshaped antenna wrapped around the chamber. The electromagnetic wave emitted by the antenna causes the gasto break down and form a plasma. The antenna then excites a Helicon wave in the plasma, which further heatsthe plasma. The device has a roughly constant magnetic field in the source tube (supplied by Solenoids in theprototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region,and might be thought of as a kind of magnetic nozzle. In operation, there is a sharp boundary between the highdensity plasma inside the source region, and the low density plasma in the exhaust, which is associated with asharp change in electrical potential. The plasma properties change rapidly across this boundary, which isknown as a current free electric double layer. The electrical potential is much higher inside the source regionthan in the exhaust, and this serves both to confine most of the electrons, and to accelerate the ions away fromthe source region. Enough electrons escape the source region to ensure that the plasma in the exhaust is neutraloverall.

Comparisons

The following table compares actual test data of some ion thrusters:

Engine Propellant Required Power(kW)

Specific Impulse(s)

Thrust(mN)

NSTAR Xenon 2.3 3,300 92

NEXT[15] Xenon 7.7 4,300 327

NEXIS[16] Xenon 20.5 6,000-7,500 400

HiPEP Xenon 25-50 6,000-9,000 460-670

RIT 22[17] Xenon 5 3,000-6,000 50 - 200

Hall effect Bismuth 25 3,000 1,130

Hall effect Bismuth 140 8,000 2,500

Hall effect Xenon 25 3,250 950

Hall effect Xenon 75 2,900 2,900

FEEP Liquid Caesium 6x10−5-0.06 6,000-10,000 0.001-1

VASIMR Argon 200 3,000-30,000 ~5000

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The following thrusters are highly experimental and have been tested only in pulse mode.

Engine Propellant Required Power(kW)

Specific Impulse(s)

Thrust(mN)

MPDT Hydrogen 1,500 4,900 26,300

MPDT Hydrogen 3,750 3,500 88,500

MPDT Hydrogen 7,500 6,000 60,000

LiLFA Lithium Vapor 500 4,077 12,000

Lifetime

A major limiting factor of ion thrusters is their small thrust; however, it is generated at a high propellantefficiency (mass utilisation, specific impulse). The efficiency comes from the high exhaust velocity, which inturn demands high 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 theneeded change in velocity (delta-v) for a particular mission. To achieve these delta-vs, ion thrusters aredesigned 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 theneutral 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 becomeso large that the ion extraction is largely affected (e.g. by the occurrence of electron backstreaming). Griderosion cannot be avoided and is the major lifetime-limiting factor. By a thorough grid design and materialselection, lifetimes of 20,000 hours and far beyond are reached, which is sufficient to fulfill current spacemissions. 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 failureeither.[18]

The Hall thrusters suffer from very strong erosion of the ceramic discharge chamber. Due to the rather highdischarge voltages of up to 1000V energetic ions can impinge to the chamber walls and erode material.Lifetimes of a few thousand hours are reached.

Propellants

Ionization energy represents a very large percentage of the energy needed to run ion drives. The idealpropellant for ion drives is thus a propellant molecule or atom with a high mass/ionisation energy ratio. In

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addition, the propellant should not cause erosion of the thruster to any great degree to permit long life; andshould not contaminate the vehicle.

Many current designs use xenon gas due to its low ionisation energy, reasonably high atomic number, inertnature, and low erosion. 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 themetal.

Other propellants such as bismuth show promise and are areas of research, particularly for gridless designssuch as Hall effect thrusters.

VASIMR design (and other plasma based engines) are theoretically able to use practically any material forpropellant. However, in current tests the most practical propellant is argon, which is a relatively abundant andcheap gas.

Applications

Ion thrusters have many applications for in-space propulsion. The best applications of the thrusters make useof the long lifetime when significant thrust is not needed. Examples of this include orbit transfers, attitudeadjustments, drag compensation for low earth orbits, transporting cargo such as chemical fuels betweenpropellant depots and ultra fine adjustments for more scientific missions. Ion thrusters can also be used forinterplanetary and deep space missions where time is not crucial. Continuous thrust over a very long time canbuild up a larger velocity than traditional chemical rockets.[8][12]

Missions

Of all the electric thrusters, ion thrusters have been the most seriously considered commercially andacademically in the quest for interplanetary missions and orbit raising maneuvers. Ion thrusters are seen as thebest solution for these missions as they require very high change in velocity overall that can be built up overlong periods of time. Several spacecraft have operated with this technology.

SERT

Ion propulsion systems were first demonstrated in space by the NASA Lewis (now Glenn Research Center)missions "Space Electric Rocket Test" (SERT) I and II.[19] The first was SERT-1, launched July 20, 1964,successfully proved that the technology operated as predicted in space. These were electrostatic ion thrustersusing mercury and cesium as the reaction mass The second test, SERT-II, launched on February 3,1970,[20][21] verified the operation of two mercury ion engines for thousands of running hours.[22]

Deep Space 1

NASA has developed an ion thruster called NSTAR for use in their interplanetary missions. This xenon-propelled ion thruster was tested in the highly successful space probe Deep Space 1, launched in 1998. Thiswas the first use of electric propulsion as the interplanetary propulsion system on a science mission.[19] Based

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on this NASA-developed technology, the contractor, Hughes, developed the XIPS (Xenon Ion PropulsionSystem) for performing stationkeeping on geosynchronous satellites.

Artemis

On 12 July 2001, the European Space Agency failed to launch their Artemis telecommunication satellite todesired altitude, and left it in a decaying orbit. The satellite's chemical propellant supply was sufficient totransfer it to a semi-stable orbit, and over the next 18 months the experimental onboard ion propulsion systemRIT-10[23] (intended for secondary stationkeeping and maneuvering) was utilized to transfer it to ageostationary orbit.[24]

Hayabusa

The Japanese space agency's Hayabusa, which was launched in 2003 and successfully rendezvoused with theasteroid 25143 Itokawa and remained in close proximity for many months to collect samples and information,was powered by four xenon ion engines. It used xenon ions generated by microwave electron cyclotronresonance, and a carbon / carbon-composite material (which is resistant to erosion) for its acceleration grid.[25]

Although the ion engines on Hayabusa had some technical difficulties, in-flight reconfiguration allowed one ofthe four engines to be repaired, and allowed the mission to successfully return to Earth.[26]

Smart 1

The Hall effect thruster is a type of ion thruster that has been used for decades for station keeping by theSoviet Union and is now also applied in the West: the European Space Agency's satellite Smart 1, launched in2003, used it (Snecma PPS-1350-G). This satellite completed its mission on 3 September 2006, in a controlledcollision on the Moon's surface, after a trajectory deviation to be able to see the 3 meter crater the impactcreated on the visible side of the moon.

Dawn

Dawn was launched on 27 September 2007 to explore the asteroid Vesta and the dwarf planet Ceres. To cruisefrom Earth to its targets it uses three Deep Space 1 heritage xenon ion thrusters (firing only one at a time) totake it in a long outward spiral. An extended mission in which Dawn explores other asteroids after Ceres isalso possible. Dawn's ion drive is capable of accelerating from 0 to 60 mph (97 km/h) in 4 days.[27]

GOCE

ESA's Gravity Field and Steady-State Ocean Circulation Explorer was launched on March 16, 2009. It willcontinue to use ion propulsion throughout its twenty month mission to combat the air-drag it experiences in itslow orbit.

GSAT-4

Indian Space Research Organisation will utilize ion thrusters in its GSAT-4 satellite. This will increase the life

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of satellite from the present 10 years to 15 years.[28]

LISA Pathfinder

LISA Pathfinder is an ESA spacecraft to be launched in 2011. It will not use ion thrusters as its primarypropulsion system, but will use both colloid thrusters and FEEP for very precise altitude control—the lowthrusts of these propulsion devices make it possible to move the spacecraft incremental distances veryaccurately. It is a test for the possible LISA mission.

See also

Electric propulsion

Colloid thrusters [29]

Spacecraft propulsion

Nuclear electric rocket

Hall effect thruster

Magnetoplasmadynamic thruster

Electrodeless plasma thruster

Field Emission Electric Propulsion

Pulsed inductive thruster

VASIMR

Articles

The Daily Galaxy: NASA Trumps Star Trek: Ion Drive Live! (April 13, 2009)

(http://www.dailygalaxy.com/my_weblog/2009/04/nasa-trumps-star-trek-ion-drive-live.html)

The Daily Galaxy: The Ultimate Space Gadget: NASA's Ion Drive Live! (July 7, 2009)

(http://www.dailygalaxy.com/my_weblog/2009/07/the-ultimate-space-gadget-nasas-ion-drive-live-a-

galaxy-classic.html)

CanWest News: New rocket engine could make trips to Mars realistic (Oct. 19, 2009)

(http://www.canada.com/technology/rocket+engine+could+make+trips+Mars+realistic/2119300/story.html)

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(PDF). The Industrial Physicist 6 (5): 16–19. http://www.aip.org/tip/INPHFA/vol-6/iss-5/p16.pdf. Retrieved 2007-

06-29.

ElectroHydroDynamic Thrusters (EHDT) (http://www.rmcybernetics.com/science/propulsion/ehdt.htm) ,

RMCybernetics.

1. ^ a b E. Y. Choueiri. "A Critical History of Electric Propulsion: The First 50 Years (1906–1956)"

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2. ^ Mark Wright,http://science.nasa.gov/newhome/headlines/prop06apr99_2.htm, April 6, 1999, science.nasa.gov, Ion

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3. ^ Robert H. Goddard - American Rocket Pioneer

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4. ^ a b "Innovative Engines - Glenn Ion Propulsion Research Tames the Challenges of 21st Century Space Travel"

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kosmonavtiki.ru/content/numbers/198/35.shtml) , Novosti Kosmonavtiki, 1999, No.7

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(http://www.esa.int/esaCP/SEMOSTG23IE_index_0.html) . Press release.

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breakthrough"

(http://web.archive.org/web/20070627103001/http://prl.anu.edu.au/SP3/research/SAFEandDS4G/webstory) . DS4G

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(http://gltrs.grc.nasa.gov/reports/2001/TM-2001-210676.pdf) . http://gltrs.grc.nasa.gov/reports/2001/TM-2001-

210676.pdf. Retrieved 2007-11-21.

9. ^ Marcuccio, S.. "The FEEP Principle" (http://www.centrospazio.cpr.it/FEEPPrinciple.html) .

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10. ^ Colleen Marrese-Reading, Jay Polk, Juergen Mueller, Al Owens. "In-FEEP Thruster Ion Beam Neutralization with

Thermionic and Field Emission Cathodes" (http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/11649/1/02-0194.pdf) .

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11. ^ Pavlos G. Mikellides. "Pulsed Inductive Thruster (PIT): Modeling and Validation Using the MACH2 Code"

(http://gltrs.grc.nasa.gov/reports/2003/CR-2003-212714.pdf) . http://gltrs.grc.nasa.gov/reports/2003/CR-2003-

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12. ^ a b K. Sankaran, L. Cassady, A.D. Kodys and E.Y. Choueiri. "A Survey of Propulsion Options for Cargo and

Piloted Missions to Mars" (http://alfven.princeton.edu/papers/Astrodyn-Finalabstext.htm) .

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13. ^ Michael R. LaPointe and Pavlos G. Mikellides. "High Power MPD Thruster Development at the NASA Glenn

Research Center" (http://gltrs.grc.nasa.gov/reports/2001/CR-2001-211114.pdf) .

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(http://www.elwingcorp.com/files/IEPC05-article.pdf) . http://www.elwingcorp.com/files/IEPC05-article.pdf. Retrieved

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15. ^ http://space.newscientist.com/article/dn12709-nextgeneration-ion-engine-sets-new-thrust-record.html

16. ^ http://en.scientificcommons.org/20787584

17. ^ http://cs.astrium.eads.net/sp/SpacecraftPropulsion/Rita/RIT-22.html

18. ^ "Destructive Physical Analysis of Hollow Cathodes from the Deep Space 1 Flight Spare Ion Engine 30,000 Hr Life

Test" (http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/39521/1/05-2793.pdf) . http://trs-

new.jpl.nasa.gov/dspace/bitstream/2014/39521/1/05-2793.pdf. Retrieved 2007-11-21.

19. ^ a b J. S. Sovey, V. K. Rawlin, and M. J. Patterson, "Ion Propulsion Development Projects in U. S.: Space Electric

Rocket Test 1 to Deep Space 1," Journal of Propulsion and Power, Vol. 17, No. 3, May–June 2001, pp. 517-526.

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(http://www.grc.nasa.gov/WWW/ion/past/70s/sert2.htm) (Accessed July 1, 2010)

21. ^ SERT (http://www.astronautix.com/craft/sert.htm) page at Astronautix (Accessed July 1, 2010)

22. ^ Space Electric Rocket Test (http://www.grc.nasa.gov/WWW/ion/past/70s/sert2.htm)

23. ^ EADS Astrium, performance data on RIT-10, RIT-XT and RIT-22

(http://cs.astrium.eads.net/sp/SpacecraftPropulsion/IonPropulsion.html)

24. ^ ESA. "Artemis team receives award for space rescue" (http://www.esa.int/esaTE/SEM1LT0P4HD_index_0.html) .

http://www.esa.int/esaTE/SEM1LT0P4HD_index_0.html. Retrieved 2006-11-16.

25. ^ ISAS. "小惑星探査機はやぶさ搭載イオンエンジン (Ion Engines used on Asteroid Probe Hayabusa)"

(http://www.ep.isas.ac.jp/muses-c/) (in Japanese). http://www.ep.isas.ac.jp/muses-c/. Retrieved 2006-10-13.

26. ^ Hiroko Tabuchi, "Faulty Space Probe Seen as Test of Japan’s Expertise

(http://www.nytimes.com/2010/07/02/business/global/02space.html) ", New York Times, July 1, 2010.

27. ^ Dawn (http://www.jpl.nasa.gov/news/features.cfm?feature=1468)

28. ^ ISRO develops tech to boost satellite life by five years (http://www.deccanchronicle.com/national/isro-develops-

tech-boost-satellite-life-five-years-362)

29. ^ Martinez-Sanchez, Manuel. "Collodal Engines" (http://ocw.mit.edu/NR/rdonlyres/Aeronautics-and-Astronautics/16-

522Spring2004/F342AA44-6F9A-413E-8054-F276524D5F23/0/lecture23_25.pdf) .

http://ocw.mit.edu/NR/rdonlyres/Aeronautics-and-Astronautics/16-522Spring2004/F342AA44-6F9A-413E-8054-

F276524D5F23/0/lecture23_25.pdf. Retrieved 2007-11-21.

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Categories: Spacecraft propulsion | Magnetic propulsion devices | Ions

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