Diffusion Associated Neoclassical Indigenous System of Hall Assembly by Dr.A.B.Rajib...

8/3/2019 Diffusion Associated Neoclassical Indigenous System of Hall Assembly by Dr.A.B.Rajib Hazarika,Phd,FRAS,AES

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Dr. A.B.Rajib Hazarika, PhD, MIAMP (Germany), FRAS (Lond.), A.E.S.Dr. A.B.Rajib Hazarika, PhD, MIAMP (Germany), FRAS (Lond.), A.E.S.

Assistant Professor, Dept. of Mathematics,Assistant Professor, Dept. of Mathematics,

Diphu Govt. College, DiphuDiphu Govt. College, Diphu

Assam, IndiaAssam, India

DIFFUSION ASSOCIATEDDIFFUSION ASSOCIATEDNEOCLASSICALNEOCLASSICAL

INDIGENOUS SYSTEM OFINDIGENOUS SYSTEM OF

HALL ASSEMBLY (DANISHA)HALL ASSEMBLY (DANISHA)


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Dr.A.B.RajibDr.A.B.RajibHazarika,PhD,MIAMP(Germany),A.Hazarika,PhD,MIAMP(Germany),A.

The present study is related differentThe present study is related different

geometry of the Hall thrusters in which Igeometry of the Hall thrusters in which Ihave tried to get better results than thehave tried to get better results than the

simple Hall thrusters available at presentsimple Hall thrusters available at present

with the future next generation devicewith the future next generation device Duo Triad Tokomak collider (DTTC) hubDuo Triad Tokomak collider (DTTC) hub

by the using new type of code Diffusionby the using new type of code Diffusion

Associated Neoclassical Indigenous HallAssociated Neoclassical Indigenous HallAssemblyAssembly (DANISHA).(DANISHA).


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Soviet and Russian SPD thrustersSoviet and Russian SPD thrustersTohelp protectyour privacy, PowerPointprevented thisexternalpicturefrom being automatically downloaded.Todownload and display thispicture, click Optionsin theMessageBar, and then click Enableexternalcontent.


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Soviet and Russian SPD thrustersSoviet and Russian SPD thrusters

The common SPD design was largely the work of A. I. Morozov.The common SPD design was largely the work of A. I. Morozov.[1][1] SPD engines wereSPD engines wereoperated since 1972. They were mainly used for satellite stabilization in Northoperated since 1972. They were mainly used for satellite stabilization in North--South and inSouth and inEastEast--West directions. Since then until the late 1990s 118 SPD engines completed theirWest directions. Since then until the late 1990s 118 SPD engines completed theirmission and some 50 continued to be operated. Thrust of the first generation of SPD engines,mission and some 50 continued to be operated. Thrust of the first generation of SPD engines,SPDSPD--50 and SPD50 and SPD--60 was 20 and 30 mN respectively. In 1982 SPD60 was 20 and 30 mN respectively. In 1982 SPD--70 and SPD70 and SPD--100 were100 wereintroduced, their thrust being 40 mN and 83 mN. In the postintroduced, their thrust being 40 mN and 83 mN. In the post--SovietSoviet RussiaRussia highhigh--power (a fewpower (a fewkilowattskilowatts) SPD) SPD--140, SPD140, SPD--160, SPD160, SPD--180, T180, T--160 and low160 and low--power (less than 500 W) SPDpower (less than 500 W) SPD--3535

were introduced.were introduced.[2][2] Soviet and Russian DASSoviet and Russian DAS--type engines include Dtype engines include D--38 and D38 and D--55.55.[2][2]

SovietSoviet--built thrusters were introduced to the West in 1992 after a team of electric propulsionbuilt thrusters were introduced to the West in 1992 after a team of electric propulsionspecialists, under the support of thespecialists, under the support of the Ballistic Missile Defense OrganizationBallistic Missile Defense Organization, visited Soviet, visited Sovietlaboratories and experimentally evaluated the SPDlaboratories and experimentally evaluated the SPD--100 (i.e., a 100100 (i.e., a 100 mm diameter SPTmm diameter SPTthruster). Over 200 Hall thrusters have been flown on Soviet/Russian satellites in the pastthruster). Over 200 Hall thrusters have been flown on Soviet/Russian satellites in the pastthirty years. They were used mainly for station keeping and small orbital corrections.thirty years. They were used mainly for station keeping and small orbital corrections.Currently Hall Thruster research, design, and theoretical modelling is led by experts at NASACurrently Hall Thruster research, design, and theoretical modelling is led by experts at NASA

Glenn Research Center and the Jet Propulsion Laboratory. A considerable amount ofGlenn Research Center and the Jet Propulsion Laboratory. A considerable amount ofdevelopment is being conducted in industry, such asdevelopment is being conducted in industry, such as AerojetAerojet and Busek Co.and Busek Co.

This technology was used on the European lunar missionThis technology was used on the European lunar mission SMARTSMART--11 and is used on a numberand is used on a numberof commercial geostationary satellites.of commercial geostationary satellites.[3][3]


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IntroductionIntroduction

What's a Hall Thruster?What's a Hall Thruster? The Hall thruster is a type of plasmaThe Hall thruster is a type of plasma--based propulsion systems for spacebased propulsion systems for space

vehicles. The amount of fuel that must be carried by a satellite depends onvehicles. The amount of fuel that must be carried by a satellite depends onthe speed with which the thruster can eject it. Chemical rockets have verythe speed with which the thruster can eject it. Chemical rockets have verylimited fuel exhaust speed. Plasmas can be ejected at much higher speeds,limited fuel exhaust speed. Plasmas can be ejected at much higher speeds,therefore less fuel need be carried on board.therefore less fuel need be carried on board.

The Hall thruster was invented in the late 1950's. Until the mid 1990's, itThe Hall thruster was invented in the late 1950's. Until the mid 1990's, ithas been developed primarily by the Russians. During the past 30 years, thehas been developed primarily by the Russians. During the past 30 years, theRussian placed in orbit more than 100 Hall thrusters. However, the vastRussian placed in orbit more than 100 Hall thrusters. However, the vastmajority of satellites worldwide have relied on chemical thrusters and, to amajority of satellites worldwide have relied on chemical thrusters and, to alesser extent, arcjet thrusters andlesser extent, arcjet thrusters and ion thrusters.ion thrusters.

A conventional electrostatic ion thruster consists of two grids, an anodeA conventional electrostatic ion thruster consists of two grids, an anodeand a cathode, between which a voltage drop occurs. Positively chargedand a cathode, between which a voltage drop occurs. Positively charged

ions accelerate away from the anode toward the cathode grid and throughions accelerate away from the anode toward the cathode grid and throughit. After the ions get past the cathode, electrons are added to the flow,it. After the ions get past the cathode, electrons are added to the flow,neutralizing the output to keep it moving. A thrust is exerted on the anodeneutralizing the output to keep it moving. A thrust is exerted on the anode--cathode system, in a direction opposite to that of the flow.cathode system, in a direction opposite to that of the flow.


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Unfortunately, a positive charge builds up in the space between the grids, limiting theUnfortunately, a positive charge builds up in the space between the grids, limiting theion flow and, therefore, the magnitude of the thrust that can be attained.ion flow and, therefore, the magnitude of the thrust that can be attained.

In a Hall thruster, electrons injected into a radial magnetic field neutralize the spaceIn a Hall thruster, electrons injected into a radial magnetic field neutralize the spacecharge. The magnitude of the applied magnetic field is approximately 100charge. The magnitude of the applied magnetic field is approximately 100--200 gauss,200 gauss,strong enough to trap the electrons by causing them to spiral around the field lines in thestrong enough to trap the electrons by causing them to spiral around the field lines in the

coaxial channel. The magnetic field and a trapped electron cloud together serve as acoaxial channel. The magnetic field and a trapped electron cloud together serve as avirtual cathode. The ions, too heavy to be affected by the field, continue their journeyvirtual cathode. The ions, too heavy to be affected by the field, continue their journeythrough the virtual cathode. The movement of the positive and negative electricalthrough the virtual cathode. The movement of the positive and negative electricalcharges through the system results in a net force (thrust) on the thruster in a directioncharges through the system results in a net force (thrust) on the thruster in a directionopposite that of the ion flow.opposite that of the ion flow.

Existing Hall thrusters can produce large jet velocities 10Existing Hall thrusters can produce large jet velocities 10--30 km/s within the input30 km/s within the inputpower in the range from hundred watts to tens of kilowatts. For the statepower in the range from hundred watts to tens of kilowatts. For the state--ofof--thethe--artartthrusters operating in the power range of above kilowatt, 50thrusters operating in the power range of above kilowatt, 50--60% of the input electric60% of the input electric

power goes to the kinetic power of the plasma jet. These thrusters are capable topower goes to the kinetic power of the plasma jet. These thrusters are capable toproduce the thrust in the range 0.1produce the thrust in the range 0.1--1 N. Since ion acceleration takes place in a quasi1 N. Since ion acceleration takes place in a quasi--neutral plasma, Hall thrusters are not limited by spaceneutral plasma, Hall thrusters are not limited by space--charge build up. Hence, highercharge build up. Hence, highercurrent and thrust densities than conventional ion thrusters can be achieved atcurrent and thrust densities than conventional ion thrusters can be achieved atdischarge voltages from hundreds volts to a few kilovolts. With such performancedischarge voltages from hundreds volts to a few kilovolts. With such performancecapabilities Hall thrusters can be used to keep satellites on geosynchronous orbit (GEO),capabilities Hall thrusters can be used to keep satellites on geosynchronous orbit (GEO),to compensate for atmospheric drag on satellite in lowto compensate for atmospheric drag on satellite in low--earth orbits (LEO), to raise aearth orbits (LEO), to raise asatellite from LEO to GEO and for interplanetary missions.satellite from LEO to GEO and for interplanetary missions. Besides space applications,Besides space applications,Hall thrusters can be also useful for industrial applications such as plasma processing ofHall thrusters can be also useful for industrial applications such as plasma processing ofmaterials.materials.


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The Hall Thruster ConceptThe Hall Thruster Concept

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"Princeton Plasma Physics Laboratory: Fueling the Future" presents an"Princeton Plasma Physics Laboratory: Fueling the Future" presents anoverview of the Laboratory's research program. The video includes a basicoverview of the Laboratory's research program. The video includes a basicintroduction to the principles of magnetic fusion energy, a mission synopsisintroduction to the principles of magnetic fusion energy, a mission synopsisof PPPL's current major fusion experiment, the National Spherical Torusof PPPL's current major fusion experiment, the National Spherical Torus

Experiment, and descriptions of fusion devices proposed for the future.Experiment, and descriptions of fusion devices proposed for the future.These include the National Compact Stellarator Experiment, being built atThese include the National Compact Stellarator Experiment, being built atPPPL, and the international ITER project. Information on the application ofPPPL, and the international ITER project. Information on the application ofplasma physics to solve nearplasma physics to solve near--term problems is also presented.term problems is also presented.

OperationOperation

The essential working principle of the Hall thruster is that it uses anThe essential working principle of the Hall thruster is that it uses an

electrostatic potential to accelerate ions up to high speeds. In a Hall thrusterelectrostatic potential to accelerate ions up to high speeds. In a Hall thrusterthe attractive negative charge is provided by an electron plasma at the openthe attractive negative charge is provided by an electron plasma at the openend of the thruster instead of a grid. A radial magnetic field of a fewend of the thruster instead of a grid. A radial magnetic field of a fewmilliteslasmilliteslas[4][4] is used to hold the electrons in place, where the combinationis used to hold the electrons in place, where the combinationof the magnetic field and an attraction to the anode force a fast circulatingof the magnetic field and an attraction to the anode force a fast circulatingelectron current around the axis of the thruster and only a slow axial driftelectron current around the axis of the thruster and only a slow axial drifttowards the anode occurs.towards the anode occurs.


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Hall Thrusters are largely axiallyHall Thrusters are largely axially

symmetric. This is a crosssymmetric. This is a cross--sectionsection

containing that axis.containing that axis.

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A schematic of a Hall thruster is shown in the image to the right. AnA schematic of a Hall thruster is shown in the image to the right. Anelectric potential on the order of 300electric potential on the order of 300 volts is applied between thevolts is applied between the anodeanodeandand cathodecathode..

The central spike forms one pole of an electromagnet and is surroundedThe central spike forms one pole of an electromagnet and is surroundedby an annular space and around that is the other pole of theby an annular space and around that is the other pole of theelectromagnet, with a radial magnetic field inelectromagnet, with a radial magnetic field in--between.between.

The propellant, such asThe propellant, such as xenonxenon gas is fed through the anode, which hasgas is fed through the anode, which hasnumerous small holes in it to act as a gas distributor. Xenon propellantnumerous small holes in it to act as a gas distributor. Xenon propellantis used because of its highis used because of its high molecular weightmolecular weight and lowand low ionization potentialionization potential..As the neutral xenon atoms diffuse into the channel of the thruster, theyAs the neutral xenon atoms diffuse into the channel of the thruster, they

are ionized by collisions with high energy circulating electrons (10are ionized by collisions with high energy circulating electrons (102020 eV or 100,000 to 250,000eV or 100,000 to 250,000 C). Once ionized the xenon ions typicallyC). Once ionized the xenon ions typicallyhave a charge of +1 though a small fraction (~10%) are +2.have a charge of +1 though a small fraction (~10%) are +2.

The xenon ions are then accelerated by the electric field between theThe xenon ions are then accelerated by the electric field between theanode and the cathode. The ions quickly reach speeds of aroundanode and the cathode. The ions quickly reach speeds of around15,00015,000 m/s for a specific impulse of 1,500 seconds (15 kNs/kg). Uponm/s for a specific impulse of 1,500 seconds (15 kNs/kg). Uponexiting however, the ions pull an equal number of electrons with them,exiting however, the ions pull an equal number of electrons with them,

creating a plume with no net charge.creating a plume with no net charge.


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Field Emission CathodesField Emission Cathodes

Cathode ConstantCathode Constant--CurrentCurrentLifetime TestsLifetime Tests

Current:Current: LifetimeLifetime

0.1 mA:0.1 mA: 13,236 hours13,236 hours

1.0 mA:1.0 mA: 6,433 hours6,433 hours

TopTop

Standard halfStandard half--inch cathodeinch cathode

T05 PackageT05 Package

Nominal halfNominal half--inch designinch design

Fully flight qualified for ST7Fully flight qualified for ST7--DRSDRS Mission Output current 1 mAMission Output current 1 mA

Design with standard TO5 package availableDesign with standard TO5 package available


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Standard halfStandard half--inch cathodeinch cathode


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T05 PackageT05 Package

Nominal halfNominal half--inch designinch design

Fully flight qualified for ST7Fully flight qualified for ST7--DRSDRS

Mission Output current 1 mAMission Output current 1 mA

Design with standard TO5 package availableDesign with standard TO5 package available


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BHTBHT--200200Discharge Input Power:Discharge Input Power: 200 W200 W

Discharge Voltage:Discharge Voltage:250 V250 V

Discharge Current:Discharge Current:800 mA800 mA

Propellant Mass Flowrate:Propellant Mass Flowrate: 0.94 mg/sec0.94 mg/sec

Thrust:Thrust: 12.8 mN12.8 mN

Specific Impulse:Specific Impulse: 1390 sec1390 sec

Propulsive Efficiency:Propulsive Efficiency: 43.5 %43.5 %


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BHTBHT--600600

Discharge InputPower:Discharge InputPower: 600 W600 W

Discharge Voltage:Discharge Voltage: 300 V300 V

DischargeCurrent:DischargeCurrent: 2.05 A2.05 A

Prope

llant

Mass

Flowrate:

Prope

llant

Mass

Flowrate: 2.6 mg/sec2.6 mg/sec

Thrust:Thrust: 42 mN42 mN



The BHTThe BHT--600 Hall Effect Thruster is an ideal size for primary600 Hall Effect Thruster is an ideal size for primarypropulsion for small satellites. The BHTpropulsion for small satellites. The BHT--600 operates600 operatesefficiently over a power range of 300efficiently over a power range of 300--600 W and produce 15600 W and produce 15--48 mN of thrust with a specific impulse of 110048 mN of thrust with a specific impulse of 1100--1700 seconds.1700 seconds.


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BHTBHT--10001000


Discharge Voltage:Discharge Voltage: 350 V350 V

DischargeCurrent:DischargeCurrent: 2.85 A2.85 A

PropellantMass Flowrate:PropellantMass Flowrate: 3.4 mg/sec3.4 mg/sec

Thrust:Thrust: 58.5 mN58.5 mN



While optimized for operating at 1.0 kW, the BHTWhile optimized for operating at 1.0 kW, the BHT--1000 Hall1000 HallEffect Thruster employs refined magnetics allowing operationEffect Thruster employs refined magnetics allowing operationover a specific impulse range of 1200over a specific impulse range of 1200--2800 seconds.2800 seconds.


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BHTBHT--15001500


DischargeVol

tage:DischargeVol

tage: 340 V340 V DischargeCurrent:DischargeCurrent: 5.0 A5.0 A






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BHTBHT--80008000

Discharge InputPower:Discharge InputPower: 8 kW8 kW

DischargeVol

tage:DischargeVol







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BHTBHT--20K20K

Discharge InputPower:Discharge InputPower: 20.25 kW20.25 kW

DischargeVol

tage:DischargeVol



Thrust:Thrust: 1.08 N1.08 N


Propulsive Efficiency:Propulsive Efficiency: 72 %72 %


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The Physics behind the HallThe Physics behind the Hall

thrustersthrustersThe axial magnetic field is designed to be strong enough to substantiallyThe axial magnetic field is designed to be strong enough to substantiallydeflect the lowdeflect the low--mass electrons, but not the highmass electrons, but not the high--mass ions which have amass ions which have a

much largermuch largergyroradiusgyroradius and are hardly impeded. The majority of electronsand are hardly impeded. The majority of electronsare thus stuck orbiting in the region of high radial magnetic field near theare thus stuck orbiting in the region of high radial magnetic field near thethruster exit plane, trapped in Ethruster exit plane, trapped in EB (axial electric field and radial magneticB (axial electric field and radial magnetic

field). This orbital rotation of the electrons is a circulatingfield). This orbital rotation of the electrons is a circulating Hall currentHall current and itand it

is from this that the Hall thruster gets its name. Collisions and instabilitiesis from this that the Hall thruster gets its name. Collisions and instabilitiesallow some of the electrons to be freed from the magnetic field and they driftallow some of the electrons to be freed from the magnetic field and they drift

towards the anode.towards the anode.

About 30% of the discharge current is an electron current which doesn'tAbout 30% of the discharge current is an electron current which doesn'tproduce thrust, which limits the energetic efficiency of the thruster; the otherproduce thrust, which limits the energetic efficiency of the thruster; the other

70% of the current is in the ions. Because the majority of electrons are70% of the current is in the ions. Because the majority of electrons aretrapped in the Hall current, they have a long residence time inside thetrapped in the Hall current, they have a long residence time inside the

thruster and are able to ionize almost all (~90%) of the xenon propellant.thruster and are able to ionize almost all (~90%) of the xenon propellant.The ionization efficiency of the thruster is thus around 90%, while theThe ionization efficiency of the thruster is thus around 90%, while the

discharge current efficiency is around 70% for a combined thrusterdischarge current efficiency is around 70% for a combined thrusterefficiency of around 63% (= 90%efficiency of around 63% (= 90% 70%).70%).


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Experimental aspectExperimental aspect

The magnetic field thus ensures that the discharge power predominatelyThe magnetic field thus ensures that the discharge power predominatelygoes into accelerating the xenon propellant and not the electrons, and thegoes into accelerating the xenon propellant and not the electrons, and thethruster turns out to be reasonably efficient.thruster turns out to be reasonably efficient.

Compared to chemical rockets the thrust is very small, on the order ofCompared to chemical rockets the thrust is very small, on the order of8080 mN for a typical thruster. For comparison, the weight of a coin like themN for a typical thruster. For comparison, the weight of a coin like theU.S. quarterU.S. quarteror a 20or a 20--centcent Euro coinEuro coin is approximately 60is approximately 60 mN.mN.

However, Hall thrusters operate at the highHowever, Hall thrusters operate at the high specific impulsesspecific impulses that isthat isachieved with ion thrusters. One particular advantage of Hall thrusters, asachieved with ion thrusters. One particular advantage of Hall thrusters, ascompared to an ion thruster, is that the generation and acceleration of thecompared to an ion thruster, is that the generation and acceleration of theions takes place in a quasiions takes place in a quasi--neutral plasma and so there is noneutral plasma and so there is no ChildChild--Langmuir charge (space charge)Langmuir charge (space charge) saturated currentsaturated current limitation on the thrustlimitation on the thrustdensity, and thus thrust is high for electrically accelerated thrusters.density, and thus thrust is high for electrically accelerated thrusters.

Another advantage is that these thrusters can use a wider variety ofAnother advantage is that these thrusters can use a wider variety of

propellants supplied to the anode, even oxygen, although something easilypropellants supplied to the anode, even oxygen, although something easilyionized is needed at the cathode.ionized is needed at the cathode.[5][5] One propellant that is starting to beOne propellant that is starting to beused is liquidused is liquidbismuthbismuth due to its low cost, high mass and low partialdue to its low cost, high mass and low partialpressure.pressure.


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THEORYTHEORY

In this study, we developed three computational techniques for the ECEIn this study, we developed three computational techniques for the ECEradiation analysis of the Hall thruster.radiation analysis of the Hall thruster.

The first one is the single particle approximation analysis. This is theThe first one is the single particle approximation analysis. This is thesimplest one among the approaches. We modeled the plasma region of thesimplest one among the approaches. We modeled the plasma region of theHall thruster with three parameters, the magnetic field, electronHall thruster with three parameters, the magnetic field, electron

temperature, and electron density distributions. These parameters aretemperature, and electron density distributions. These parameters areconstant in a cell. We calculated the radiation with the parameterconstant in a cell. We calculated the radiation with the parameterdistributions according to the observation angle. The frequency of a cell isdistributions according to the observation angle. The frequency of a cell isdetermined by the magnetic field of the cell. This analysis is easy todetermined by the magnetic field of the cell. This analysis is easy toapproach and does not require a high computing performance. However,approach and does not require a high computing performance. However,the results of this analysis dont have detail results. The radiated electricthe results of this analysis dont have detail results. The radiated electricfield is derived from the power, so there is no polarization information onfield is derived from the power, so there is no polarization information on

the electric field. We moved on more sophisticated analysis.the electric field. We moved on more sophisticated analysis.


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SimulationsSimulations

The next one is the ParticleThe next one is the Particle--InIn--Cell (PIC) analysis. PIC is for analysis ofCell (PIC) analysis. PIC is for analysis ofmicroscopic phenomena. Particle motions in the thruster channel region ismicroscopic phenomena. Particle motions in the thruster channel region issimulated with the PIC method. We selected electrons from the Maxwellsimulated with the PIC method. We selected electrons from the Maxwell--Boltzmann distribution for the speed of electrons. The MonteBoltzmann distribution for the speed of electrons. The Monte--Carlo methodCarlo methodwas adopted in this selection. We solved the Lorentz force equation to getwas adopted in this selection. We solved the Lorentz force equation to getthe motion data of the electrons and analyzed the radiated electric field withthe motion data of the electrons and analyzed the radiated electric field withthe particle motions. Then, we took the Fourier transform of the electricthe particle motions. Then, we took the Fourier transform of the electricfield to consider the radiation in the frequency domain. This approach isfield to consider the radiation in the frequency domain. This approach isfrom definition, the radiation is from charge acceleration. It is morefrom definition, the radiation is from charge acceleration. It is morerealistic approach to the plasma. It uses same parameter distributions, butrealistic approach to the plasma. It uses same parameter distributions, butthe parameter in a cell is not constant any more because of adopting thethe parameter in a cell is not constant any more because of adopting theMonteMonte--Carlo method. It also shows the polarization information of theCarlo method. It also shows the polarization information of theradiation. However, we assume in this analysis that the radiation is in freeradiation. However, we assume in this analysis that the radiation is in freespace. The channel plasma is considered as current sources for radiation.space. The channel plasma is considered as current sources for radiation.The material constants of the plasma are concerned as free space.The material constants of the plasma are concerned as free space.


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Dr.A.B.RajibDr.A.B.Rajib

Hazarika,PhD,MIAMP(Germany),A.Hazarika,PhD,MIAMP(Germany),A.

Simulation codesSimulation codes

The last approach adopted is to consider the non freeThe last approach adopted is to consider the non freespace and inhomogeneous media. The hybridspace and inhomogeneous media. The hybridFEM/MoM (hybrid element method) was suggestedFEM/MoM (hybrid element method) was suggested

to exploit advantages of finite element method (FEM)to exploit advantages of finite element method (FEM)and method of moment (MoM), the representativeand method of moment (MoM), the representativemethods for the radiation analysis, and to compensatemethods for the radiation analysis, and to compensatetheir disadvantages. The hybrid element method wastheir disadvantages. The hybrid element method wasintroduced to analyze the ECE radiation by usingintroduced to analyze the ECE radiation by using

EMAP5. In this analysis, the plasma was consideredEMAP5. In this analysis, the plasma was consideredas dielectrics, and the source currents were from theas dielectrics, and the source currents were from theplasma parameters.plasma parameters.


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Electric Propulsion SystemElectric Propulsion System

More than three hundred electric propulsion thrusters haveMore than three hundred electric propulsion thrusters haveflown on over 100 spacecraft over the last thirty five years andflown on over 100 spacecraft over the last thirty five years anda significant increase in usage is expected over the nexta significant increase in usage is expected over the nextdecade. The 1990s have been described as the era ofdecade. The 1990s have been described as the era of

application [27] because the benefits of electric propulsion areapplication [27] because the benefits of electric propulsion arebeing realized on numerous commercial satellite missions andbeing realized on numerous commercial satellite missions andthere has been an increase in flight activity for a broadthere has been an increase in flight activity for a broadspectrum of electric propulsion devices. Advancements inspectrum of electric propulsion devices. Advancements inelectric propulsion related technologies and thruster design 3electric propulsion related technologies and thruster design 3

improvements, based on extensive ground and flight testimprovements, based on extensive ground and flight testresults, have brought some electric propulsion devices to aresults, have brought some electric propulsion devices to ahigh level of technological maturity.high level of technological maturity.


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The risk of employing electric thrusters on spacecraft hasThe risk of employing electric thrusters on spacecraft hasdiminished in recent years due to an increase in the numberdiminished in recent years due to an increase in the number

of successful electric thruster missions, improvements inof successful electric thruster missions, improvements inthruster materials and designs, and an improvedthruster materials and designs, and an improvedunderstanding of fundamental thruster operating principlesunderstanding of fundamental thruster operating principlesand spacecraft integration issues. With the increasingand spacecraft integration issues. With the increasingemphasis on lowering the mass of spacecraft propulsionemphasis on lowering the mass of spacecraft propulsion

systems, increasing spacecraft orbiting lifetimes, andsystems, increasing spacecraft orbiting lifetimes, andreducing overall costs, together with greater amounts ofreducing overall costs, together with greater amounts ofelectric power now available onelectric power now available on--board spacecraft, theboard spacecraft, theapplications for electric propulsion systems will certainlyapplications for electric propulsion systems will certainlycontinue to grow. Electric propulsion technology hascontinue to grow. Electric propulsion technology has

matured to a point where its expanded use for select spacematured to a point where its expanded use for select spacemissions is justified from both a technological and anmissions is justified from both a technological and aneconomic standpoint.economic standpoint.


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Electric thrusters can outperform conventional chemical (liquidElectric thrusters can outperform conventional chemical (liquidand solid propellant) propulsion systems for certain spaceand solid propellant) propulsion systems for certain spacemissions because of their generally higher specific impulsemissions because of their generally higher specific impulse

values.values. For select missions, replacing current chemical propulsionFor select missions, replacing current chemical propulsion

systems with high performance electric propulsion systems cansystems with high performance electric propulsion systems canprovide substantial mass and cost savings, increased orbitingprovide substantial mass and cost savings, increased orbitinglifetimes, and increased mission capabilities.lifetimes, and increased mission capabilities.

The current and likely nearThe current and likely near--term electric thruster missionsterm electric thruster missionsinclude station keeping, drag compensation, attitude control,include station keeping, drag compensation, attitude control,

station repositioning, orbit raising or lowering, orbitstation repositioning, orbit raising or lowering, orbitrepositioning, and maneuvering of interplanetary spacecraftrepositioning, and maneuvering of interplanetary spacecraft[49].[49].

Electric propulsion is the acceleration of propellant gases by anyElectric propulsion is the acceleration of propellant gases by anyof electrical heating, electric or magnetic, or both of field forcesof electrical heating, electric or magnetic, or both of field forcesto provide propulsive thrust to a vehicle.to provide propulsive thrust to a vehicle.

It involves the conversion of electrical energy into kinetic energyIt involves the conversion of electrical energy into kinetic energyof the exhaust gases.of the exhaust gases.

There are numerous electric propulsion devices described in theThere are numerous electric propulsion devices described in theliterature, which can be grouped into at least one of threeliterature, which can be grouped into at least one of threefundamental categories.fundamental categories.


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ElectroElectro--thermal Propulsionthermal Propulsion

the propellant is heated using electrical energy,the propellant is heated using electrical energy,

and the hot propellant gas is thenand the hot propellant gas is then

thermodynamically expandedthermodynamically expanded and accelerated through an exhaust nozzle, e.g.and accelerated through an exhaust nozzle, e.g.

resistojet and arcjet thrusters.resistojet and arcjet thrusters.


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ElectroElectro--static Propulsionstatic Propulsion

the propellant atoms are ionized andthe propellant atoms are ionized and

accelerated out of the thruster by electrostaticaccelerated out of the thruster by electrostatic

field forces.field forces.

The exhausted propellant ions are neutralizedThe exhausted propellant ions are neutralized

by electrons emitted from an external cathode,by electrons emitted from an external cathode,

e.g. ion thruster and field emission electrice.g. ion thruster and field emission electric

propulsion thruster.propulsion thruster.


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Electromagnetic PropulsionElectromagnetic Propulsion

the propellant is ionized and accelerated by the combinedthe propellant is ionized and accelerated by the combinedinteraction of electric and magnetic field forces on theinteraction of electric and magnetic field forces on theresultant propellant plasma, e.g. Hall thruster, pulsed plasmaresultant propellant plasma, e.g. Hall thruster, pulsed plasmathruster, and magnetothruster, and magneto--plasmaplasma--dynamic thrusters.dynamic thrusters.

New electric propulsion technologies designed to operate atNew electric propulsion technologies designed to operate athigher power (5higher power (5 50 kW) for future long range planetary50 kW) for future long range planetaryexploration and large velocity change maneuvers are underexploration and large velocity change maneuvers are understudy. This effort has in part been a response to NASAsstudy. This effort has in part been a response to NASAsProject Prometheus [42], a technology program to developProject Prometheus [42], a technology program to develop

safe, efficient high power sources for solar system exploration.safe, efficient high power sources for solar system exploration.In primary propulsion on micro spacecraft or fine positionIn primary propulsion on micro spacecraft or fine positioncontrol of conventional spacecraft has driven the interest incontrol of conventional spacecraft has driven the interest insub kilowatt thrusters [10].sub kilowatt thrusters [10].


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ResistojetResistojet

A resistojet is a device that heats a propellant stream by passing it throughA resistojet is a device that heats a propellant stream by passing it throughan ohmically heated chamber before the propellant is expanded through aan ohmically heated chamber before the propellant is expanded through adownstream nozzle. In resistojets, the propellant is fed into the thruster anddownstream nozzle. In resistojets, the propellant is fed into the thruster andheated while flowing over an immersed resistance heater or over thrusterheated while flowing over an immersed resistance heater or over thrusterchamber surfaces heated by radiation from an isolated resistance heater [27,chamber surfaces heated by radiation from an isolated resistance heater [27,38].38].

Resistojets (MRResistojets (MR--501, MR501, MR--502A, HiPEHT, etc.) have accumulated a502A, HiPEHT, etc.) have accumulated asubstantial flight history onboard at least 75 spacecraft since 1965 [27],substantial flight history onboard at least 75 spacecraft since 1965 [27],mainly performing northmainly performing north--south station keeping (NSSK) and some attitudesouth station keeping (NSSK) and some attitudecontrol, eastcontrol, east--west station keeping (EWSK), onwest station keeping (EWSK), on--orbit maneuvering, andorbit maneuvering, andlimited onlimited on--orbit boosting. Future resistojet missions include stationorbit boosting. Future resistojet missions include stationkeeping, orbit insertion, and dekeeping, orbit insertion, and de--orbit functions. Resistojets have been usedorbit functions. Resistojets have been used

on Lockheed Martin Astro Space (LMAS) Series 4000 and 5000 satelliteson Lockheed Martin Astro Space (LMAS) Series 4000 and 5000 satellitesand recently on Iridium satellites.and recently on Iridium satellites.


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Arc jetArc jet

An arcjet is a device that heats a propellant stream by passing a high current electricalAn arcjet is a device that heats a propellant stream by passing a high current electricalarc through it, before the propellant is expanded through a downstream nozzle [38].arc through it, before the propellant is expanded through a downstream nozzle [38].

In arcjets, an electrical arc discharge is initiated between a central cathode and a coaxialIn arcjets, an electrical arc discharge is initiated between a central cathode and a coaxialanode, which also acts as the thrusters nozzle.anode, which also acts as the thrusters nozzle.

The propellant is fed into the thruster and heated while flowing through and around theThe propellant is fed into the thruster and heated while flowing through and around thearc discharge.arc discharge.

A research group from the Kharkov Aviation Institute (KhAI), which was establishedA research group from the Kharkov Aviation Institute (KhAI), which was establishedwith Russian industrial companies and still keeps working relations with them, haswith Russian industrial companies and still keeps working relations with them, haspresented an analytical study of gas acceleration in the supersonic nozzle of the arcjetpresented an analytical study of gas acceleration in the supersonic nozzle of the arcjetthruster [68].thruster [68].

The heat transfer in supersonic flow under electrical discharge results in significantThe heat transfer in supersonic flow under electrical discharge results in significantdisplacement of the critical throat comparing with classic adiabatic flow. Keydisplacement of the critical throat comparing with classic adiabatic flow. Keyparameters like an expansion angle and throat position were presented as functions ofparameters like an expansion angle and throat position were presented as functions ofarc parameters. Since 1993, arcjets (MRarc parameters. Since 1993, arcjets (MR--508, MR508, MR--509, and MR509, and MR--510) have been used for510) have been used forNSSK on at least six LMAS Series 7000 and ANSSK on at least six LMAS Series 7000 and A--2100 satellites and are base lined for2100 satellites and are base lined for

several future satellites. In 1997several future satellites. In 1997--1998, arcjets were used on both an experimentalUSAF1998, arcjets were used on both an experimentalUSAForbit raising mission (26orbit raising mission (26--kW ESEX arcjet) and an orbit insertion/maintenance missionkW ESEX arcjet) and an orbit insertion/maintenance mission(ATOS arcjet).(ATOS arcjet).


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Ion ThrusterIon Thruster

An ion thruster is a device that accelerates propellant ions byAn ion thruster is a device that accelerates propellant ions byan electrostatic field [38]. In ion thrusters, neutral propellantan electrostatic field [38]. In ion thrusters, neutral propellantatoms are fed into a discharge chamber and ionized byatoms are fed into a discharge chamber and ionized by

bombardment with electrons emitted from a cathode in a lowbombardment with electrons emitted from a cathode in a lowvoltage electrical discharge. Since 1962, ion thrusters havevoltage electrical discharge. Since 1962, ion thrusters haveflown on about eleven experimental spacecraft. Several ionflown on about eleven experimental spacecraft. Several ionthrusters (XIPSthrusters (XIPS--13, XIPS13, XIPS--25, IES, and UK25, IES, and UK--10) and a10) and aradiofrequency ion thruster (RITradiofrequency ion thruster (RIT--10) were launched to provide10) were launched to provide

NSSK for several operational satellites. Hughes used theirNSSK for several operational satellites. Hughes used theirXIPSXIPS--13 ion thruster on HS13 ion thruster on HS--601, PAS601, PAS--5, and Galaxt 85, and Galaxt 8--ii

satellites and their XIPSsatellites and their XIPS--25 ion thruster on HS25 ion thruster on HS--702 and702 andGalaxy 10 satellites [27, 49]. Keldysh Research CenterGalaxy 10 satellites [27, 49]. Keldysh Research Centerpresented results of numerical simulation of a lowpresented results of numerical simulation of a low--power Xepower Xe--ion thruster with an advanced, slition thruster with an advanced, slit--type accelerating system.type accelerating system.Experiments were carried out for the power range of 50Experiments were carried out for the power range of 50--150 W150 Wand specific impulse values of 2500and specific impulse values of 2500 3500 s were achieved.3500 s were achieved.

Highest values of thruster efficiency were about 65 % [68].Highest values of thruster efficiency were about 65 % [68].


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The NSTAR electron bombardment ion thruster was provided primary propulsion forThe NSTAR electron bombardment ion thruster was provided primary propulsion forthe Deep Spacethe Deep Space--1 spacecraft on the first flight of NASAs New Millennium program in1 spacecraft on the first flight of NASAs New Millennium program in1998. The success of the Deep Space 1 technology demonstration has led to the planned1998. The success of the Deep Space 1 technology demonstration has led to the planneduse of three NSTAR ion thrusters for the DAWN mission to explore Ceres and Vesta,use of three NSTAR ion thrusters for the DAWN mission to explore Ceres and Vesta,two protoplanets between the orbits of Mars and Jupiter [10]. DAWN, rescheduled fortwo protoplanets between the orbits of Mars and Jupiter [10]. DAWN, rescheduled for

launch in September 2007, would be the first NASA space science mission to implementlaunch in September 2007, would be the first NASA space science mission to implementelectric propulsion. Boeing Electron Dynamics Division (EDD) is developing the 30 cmelectric propulsion. Boeing Electron Dynamics Division (EDD) is developing the 30 cmion thrusters for this Discoveryion thrusters for this Discovery--class mission. The NSTAR thruster extended life testclass mission. The NSTAR thruster extended life testended this year after more than 30,300 hr of operation, having processed over 230 kg ofended this year after more than 30,300 hr of operation, having processed over 230 kg ofxenon. The NSTAR program far exceeded its original goals of 8,000 hr of operation withxenon. The NSTAR program far exceeded its original goals of 8,000 hr of operation witha total xenon throughput of 83 kg. The NASA Evolutionary Xenon Thruster (NEXT) isa total xenon throughput of 83 kg. The NASA Evolutionary Xenon Thruster (NEXT) isdesigned to deliver a throttleable 7 kW, 40 cm ion thruster with a xenon throughputdesigned to deliver a throttleable 7 kW, 40 cm ion thruster with a xenon throughputcapability of over 400 kg, a specific impulse (Isp) of 2,200capability of over 400 kg, a specific impulse (Isp) of 2,200 4,120 sec, and a thrust of 504,120 sec, and a thrust of 50

210 mN. Two NASA210 mN. Two NASA--led teams continued work toward the development of a longled teams continued work toward the development of a long--lifelife

engine system for power levels greater than 20 kW and Isp in the 6,000engine system for power levels greater than 20 kW and Isp in the 6,000--8,0008,000--sec range.sec range.The High Power Ion Propulsion team, led by NASAGlenn is developing an 8,000 sec, 25The High Power Ion Propulsion team, led by NASAGlenn is developing an 8,000 sec, 25kW gridded ion thruster using a microwave ionization source and neutralizer in akW gridded ion thruster using a microwave ionization source and neutralizer in arectangular geometry. The JPLrectangular geometry. The JPL--led team is developing the nuclear electric xenon ionled team is developing the nuclear electric xenon ionsystem, which will include advanced carbonsystem, which will include advanced carbon--carbon grids and a reservoir hollowcarbon grids and a reservoir hollowcathode, in an effort to develop a 20 kW, 7,500 sec Isp thruster with high propellantcathode, in an effort to develop a 20 kW, 7,500 sec Isp thruster with high propellantthroughput capability.throughput capability.

On January 31, 2003, ESAs latest telecommunication technology demonstrationOn January 31, 2003, ESAs latest telecommunication technology demonstration

satellite, Artemis, reached its assigned geostationary orbit after an 18 month transfer.satellite, Artemis, reached its assigned geostationary orbit after an 18 month transfer.The spacecraft had used its experimental ion propulsion system, consisting of two RITThe spacecraft had used its experimental ion propulsion system, consisting of two RIT--10 and T5 thrusters, to complete the maneuver.10 and T5 thrusters, to complete the maneuver.


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Field Emission Electric PropulsionField Emission Electric Propulsion

In field emission electric propulsion (FEEP)In field emission electric propulsion (FEEP)

thrusters, the liquid propellant is fed to the tipthrusters, the liquid propellant is fed to the tip

of a needleof a needle--like emitter and intense locallike emitter and intense local

electric fields cause charged liquid droplets toelectric fields cause charged liquid droplets to

spontaneously form. The charged liquidspontaneously form. The charged liquid

droplets are extracted away from the liquiddroplets are extracted away from the liquid

surface and accelerated by the electrostaticsurface and accelerated by the electrostaticfields.fields.


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Electromagnetic PropulsionElectromagnetic Propulsion

A magneto plasma dynamic thruster is a device thatA magneto plasma dynamic thruster is a device thataccelerates a propellant plasma by an internal or externalaccelerates a propellant plasma by an internal or externalmagnetic field acting on an internal arc current [38].magnetic field acting on an internal arc current [38].

Magneto plasma dynamic (MPD) thrusters frequently useMagneto plasma dynamic (MPD) thrusters frequently use

similar electrode geometries as arcjets and also use ansimilar electrode geometries as arcjets and also use anelectrical arc discharge. However, the majority of thrustelectrical arc discharge. However, the majority of thrustgenerated in MPDTs is due to electromagnetic forces exertedgenerated in MPDTs is due to electromagnetic forces exertedon the propellant plasma by interaction with the arc and theon the propellant plasma by interaction with the arc and theselfself--induced magnetic field. In pulsed plasma, a portion of theinduced magnetic field. In pulsed plasma, a portion of the

propellant feedstock (typically solid Teflon) is ablated andpropellant feedstock (typically solid Teflon) is ablated and

ionized by an electrical arc discharge sheet initiated betweenionized by an electrical arc discharge sheet initiated betweentwo electrodes by a discharging capacitor.two electrodes by a discharging capacitor.

The resultant propellant plasma is accelerated by interactionThe resultant propellant plasma is accelerated by interactionwith the arc and the selfwith the arc and the self--induced magnetic field.induced magnetic field.


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Thrust systems and their specific impulse [75]Thrust systems and their specific impulse [75]

Engine Effective Exhaust Isp Thrust DurationEngine Effective Exhaust Isp Thrust Duration

Velocity (m/s) (s) (N)Velocity (m/s) (s) (N)

Solid rocket 1,000Solid rocket 1,000 -- 4,000 100 1034,000 100 103 --107 minutes107 minutes

Resistojet rocket 2,000Resistojet rocket 2,000 -- 6,000 106,000 10--22 -- 1010

minutesminutes Arcjet rocket 4,000Arcjet rocket 4,000 -- 12,000 1012,000 10--22 -- 1010

minutesminutes

Hall thruster 8,000Hall thruster 8,000 -- 50,000 1,500 1050,000 1,500 10--33 -- 1010monthsmonths

Ion thruster 15,000Ion thruster 15,000 -- 80,000 5,000 1080,000 5,000 10--33 -- 1010monthsmonths

VASIMR 10,000VASIMR 10,000 -- 300,000 30,000 40300,000 30,000 40 -- 1,200days1,200days --monthsmonths


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Hall ThrustersHall Thrusters

The Hall thruster is a plasma propulsion device designed in the 1960s.The Hall thruster is a plasma propulsion device designed in the 1960s.

The inventor is A. I. Morozov. They are mostly known as electricThe inventor is A. I. Morozov. They are mostly known as electricpropulsionpropulsion

thrusters for spacecraft, and are also called stationary plasma thrustersthrusters for spacecraft, and are also called stationary plasma thrusters(SPTs).(SPTs).

The advantages of the Hall thruster are higher thrust densities and specificThe advantages of the Hall thruster are higher thrust densities and specificimpulses between 1 and 2000 sec.impulses between 1 and 2000 sec.

These advantages promise to increase operating lifetime and payload mass.These advantages promise to increase operating lifetime and payload mass.Because of these advantages, the Hall thrusters are considered ideal forBecause of these advantages, the Hall thrusters are considered ideal formany onmany on--orbit applications including station keeping, orbit reorbit applications including station keeping, orbit re--phasing, andphasing, andorbit transfer of geosynchronous communication satellites.orbit transfer of geosynchronous communication satellites.

It has become clear that the physical processes in the Hall thrusters areIt has become clear that the physical processes in the Hall thrusters areextremely complicated, despite the simple construction of the devices.extremely complicated, despite the simple construction of the devices.

The discharge in the Hall thrusters is unlike any other known discharge.The discharge in the Hall thrusters is unlike any other known discharge.

It is characterized by the spatial separation of the ionization andIt is characterized by the spatial separation of the ionization andcceleration zonescceleration zones


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The Hall thruster diagram [9]. 1) Magnetic system; 2) insulator;The Hall thruster diagram [9]. 1) Magnetic system; 2) insulator;

3) anode; 4) cathode; 5) gas inlet.3) anode; 4) cathode; 5) gas inlet.

In the ionization zone, crossed electric and magnetic fields areIn the ionization zone, crossed electric and magnetic fields are

present with the radial directional magnetic field crossing the wallpresent with the radial directional magnetic field crossing the wallwhile the axial directional electric field is tangential to them.while the axial directional electric field is tangential to them.

A free path length of charged particles much higher than the size ofA free path length of charged particles much higher than the size ofsystem, and the drift of electrons is closed.system, and the drift of electrons is closed.

Electrons emitted from an external hollow cathode are hinderedElectrons emitted from an external hollow cathode are hinderedfrom directly reaching the anode by the radial magnetic fieldfrom directly reaching the anode by the radial magnetic field

increasing to the outlet of thruster and become magnetized andincreasing to the outlet of thruster and become magnetized andconfined in an azimuthal E X B drift motion.confined in an azimuthal E X B drift motion.

The neutral propellant atoms are fed into the discharge chamberThe neutral propellant atoms are fed into the discharge chamberand ionized by bombardment with the electrons.and ionized by bombardment with the electrons.

The radial magnetic field is not strong enough to make the ionsThe radial magnetic field is not strong enough to make the ionsmagnetized, because the Lamor radius of the ions is much biggermagnetized, because the Lamor radius of the ions is much biggerthan the thruster size.than the thruster size.

The ions are accelerated axially by the electric field, and the thrustThe ions are accelerated axially by the electric field, and the thrustis produced by momentum imparted to the ions.is produced by momentum imparted to the ions.

Plasma is created with a very high electron temperature of up to 20Plasma is created with a very high electron temperature of up to 20eV within the discharge [55].eV within the discharge [55].


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SPT SeriesSPT Series

Hall thrusters (SPTHall thrusters (SPT--50, SPT50, SPT--70, SPT70, SPT--100, etc.) have an extensive100, etc.) have an extensive

flight history onflight history on--board Russian spacecraft for NSSK, EWSK, attitudeboard Russian spacecraft for NSSK, EWSK, attitudecontrol,orbit injection and repositioning applications on more than 50control,orbit injection and repositioning applications on more than 50Russian satellite since 1971 [27, 55].Russian satellite since 1971 [27, 55].

Hall thrusters have continued to accumulate flight time on RussianHall thrusters have continued to accumulate flight time on Russian

satellites.satellites. Since 1994, more than eight geostationary satellites equipped withSince 1994, more than eight geostationary satellites equipped with

SPTSPT--100100--type thrusters have been launched.type thrusters have been launched.

The total number of SPTThe total number of SPT--100 thrusters operated onboard these100 thrusters operated onboard thesesatellites is more than 64.satellites is more than 64.

The maximum operation time on a single SPTThe maximum operation time on a single SPT--100 has exceeded 1,500100 has exceeded 1,500

hr (on Express 11).hr (on Express 11). Stationary plasma thrusters (SPT) were developed and qualified atStationary plasma thrusters (SPT) were developed and qualified at

DB Fakel.DB Fakel.

Main functional specifications of SPT thrusters are listed in TableMain functional specifications of SPT thrusters are listed in Table


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SPT specificationsSPT specifications

Thrust Power Isp Efficiency Life timeThrust Power Isp Efficiency Life time

mN W sec % hrsmN W sec % hrs

SPTSPT--35a 135a 1-- 10 0.2 1100 35 200010 0.2 1100 35 2000

SPTSPT--50a 20 0.35 1250 35 225050a 20 0.35 1250 35 2250 SPTSPT--70a 40 0.65 1450 48 310070a 40 0.65 1450 48 3100

SPTSPT--100a 83 1.35 1550 52 8000100a 83 1.35 1550 52 8000

SPTSPT--140b 290 4.5 1800 51 7000140b 290 4.5 1800 51 7000

PPSPPS--1350c 92 1.5 1800 52 80001350c 92 1.5 1800 52 8000


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Future applicationsFuture applications

HypersonicsHypersonics

NASA's new vision for space exploration aims to take humans back to theNASA's new vision for space exploration aims to take humans back to theMoon, and eventually to Mars and beyond. Achieving this goal will involveMoon, and eventually to Mars and beyond. Achieving this goal will involvemany missions over the coming years. Perhaps the most dangerous andmany missions over the coming years. Perhaps the most dangerous andchallenging aspect of any mission is a spacecraft's hypersonic entry into achallenging aspect of any mission is a spacecraft's hypersonic entry into aplanet's atmosphere. The physical processes occurring around theplanet's atmosphere. The physical processes occurring around thespacecraft are quite complex and involve the synthesis of chemical kinetics,spacecraft are quite complex and involve the synthesis of chemical kinetics,

quantum mechanics, radiation physics, and ablation effects with fluidquantum mechanics, radiation physics, and ablation effects with fluiddynamics. To further complicate matters, the atmosphere is often rarefieddynamics. To further complicate matters, the atmosphere is often rarefiedand conventional fluid dynamic analysis is no longer applicable. Such highand conventional fluid dynamic analysis is no longer applicable. Such highenergy, high speed, rarefied conditions are very expensive and oftenenergy, high speed, rarefied conditions are very expensive and oftenimpossible to reproduce in wind tunnels here on Earth. Actual flight testsimpossible to reproduce in wind tunnels here on Earth. Actual flight testsare even more expensive and measured data is limited to that collectedare even more expensive and measured data is limited to that collectedduring the 1960's Mercury, Gemini, and Apollo programs. If numericalduring the 1960's Mercury, Gemini, and Apollo programs. If numericalsimulation can reproduce the experimental data that is available, it can thensimulation can reproduce the experimental data that is available, it can thenbe used with confidence as a fast and inexpensive design tool for newbe used with confidence as a fast and inexpensive design tool for newspacecraft flying new missions.spacecraft flying new missions.


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At low altitudes (below ~80km for Earth) the atmosphere is sufficiently dense suchAt low altitudes (below ~80km for Earth) the atmosphere is sufficiently dense suchthat molecules undergo a vast number of collisions as they move over thethat molecules undergo a vast number of collisions as they move over thespacecraft.Under these conditions the gas can accurately be assumed to behave asspacecraft.Under these conditions the gas can accurately be assumed to behave asa continuum and the Naviera continuum and the Navier--Stokes equations can be solved using methods fromStokes equations can be solved using methods fromComputational Fluid Dynamics (CFD).Computational Fluid Dynamics (CFD).

CFD methods are very mature and are capable of incorporating advanced physicalCFD methods are very mature and are capable of incorporating advanced physicalmodels such as chemical and thermal nonmodels such as chemical and thermal non--equilibrium, radiation, and evenequilibrium, radiation, and evenablation.ablation.

For very high altitudes (above ~100km for Earth) the atmosphere is rarefied to theFor very high altitudes (above ~100km for Earth) the atmosphere is rarefied to thepoint where molecules undergo far fewer collisions invalidating the continuumpoint where molecules undergo far fewer collisions invalidating the continuumassumptions inherent in the Navierassumptions inherent in the Navier--Stokes equations.Stokes equations.

In this regime the most mature numerical method is the direct simulation MonteIn this regime the most mature numerical method is the direct simulation Monte

Carlo (DSMC) method which is also capable of incorporating advanced physicalCarlo (DSMC) method which is also capable of incorporating advanced physicalmodels.models.

Since the DSMC method simulates the gas on the molecular scale it providesSince the DSMC method simulates the gas on the molecular scale it providesaccurate results in all regimes, however under continuum conditions, largeaccurate results in all regimes, however under continuum conditions, largenumbers of particles and collisions demand impractical computational resources.numbers of particles and collisions demand impractical computational resources.

Thus, in general, the DSMC method is used to simulate atmospheric entry at highThus, in general, the DSMC method is used to simulate atmospheric entry at highaltitudes and CFD is used at lower altitudes. Of course there is a large overlapaltitudes and CFD is used at lower altitudes. Of course there is a large overlapregime in which the flow around the spacecraft exhibits regions of both continuumregime in which the flow around the spacecraft exhibits regions of both continuumflow and nonflow and non--equilibrium or rarefied flow. For this reason current research is notequilibrium or rarefied flow. For this reason current research is notonly focused on using CFD and DSMC to simulate the aerothermodynamics ofonly focused on using CFD and DSMC to simulate the aerothermodynamics ofatmospheric entry, but also focuses on incorporating these methods into a hybridatmospheric entry, but also focuses on incorporating these methods into a hybridparticleparticle--continuum code.continuum code.


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Hall Thruster Channel Wall ErosionHall Thruster Channel Wall Erosion

OverviewOverview

The main lifeThe main life--limiting factor for Hall thrusters is the erosion of the channellimiting factor for Hall thrusters is the erosion of the channelwalls. As Hall thrusters are beginning to be used on more extendedwalls. As Hall thrusters are beginning to be used on more extendedmissions (10000 hours+), lifetime issues become a priority. Characterizingmissions (10000 hours+), lifetime issues become a priority. Characterizingthis erosion experimentally in ground based vacuum chambers isthis erosion experimentally in ground based vacuum chambers isprohibitively long and expensive. Thus there is a need for quick and cheap,prohibitively long and expensive. Thus there is a need for quick and cheap,yet accurate, simulations and this is the main motivation behind thisyet accurate, simulations and this is the main motivation behind this

research.research. Modeling the erosion rates along the channel walls incorporates two majorModeling the erosion rates along the channel walls incorporates two major

parts. First, the ion current to the walls needs to be determined. Then theparts. First, the ion current to the walls needs to be determined. Then thesputter yields need to be found in order to obtain the erosion rates. Two ionsputter yields need to be found in order to obtain the erosion rates. Two ionflux models are examined. One is based on scattering collisions while theflux models are examined. One is based on scattering collisions while theother focuses more on a hydrodynamic description of the plasma. Theother focuses more on a hydrodynamic description of the plasma. The

sputter yields are obtained from an empirical model based on curve fits tosputter yields are obtained from an empirical model based on curve fits toexperimental data.experimental data.

Diffusion Associated Neoclassical Indigenous System of Hall Assembly by Dr.A.B.Rajib...

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