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Design and Testing of 1 kW Hall Thruster

Design and Testing of 1 kW Hall Thruster

Nicholas Ian Denning, Nicholas Alfred Riedel

Colorado State University

Advised by: Dr. Binyamin Rubin, Dr. John Williams

19 April 2008

Design and Testing of 1 kW Hall Thruster

Background

� Advantageous for low

thrust missions

� Currently used for

station keeping, orbit

adjustments, and deep

space missions

� High specific impulse

Denning 2

Courtesy of ESA

Design and Testing of 1 kW Hall Thruster

Hall Thruster Operation

� Electrons trapped by

induced magnetic field

(Hall Effect)

� Electron/propellant

collisions cause ionization

� Propellant ions accelerate

out of thruster

� Ions are then neutralized

Denning 3

Courtesy of www.al.t.u-tokyo.ac.jp

Design and Testing of 1 kW Hall Thruster

Hall Current Measurement

� Hall current characterization

method proposed by Rubin,

Gelman, and Kapulkin in

2008

� Embedded sensors monitor

magnetic field induced by

current loop

� Hall current measurement

used to predict thrust

Denning 4

Courtesy of Dr. Binyamin Rubin

Design and Testing of 1 kW Hall Thruster

Problem Statement

� Design and test a 1 kW Hall thruster to be used for

validation of the noncontact measurement method

proposed by Rubin, Gelman, and Kapulkin in 2008

� Two additional teams worked concurrently on remaining

components required

� Thrust Stand

� Sensor Array

Denning 5

Design and Testing of 1 kW Hall Thruster

Thruster Design

� Easily modified

� Accommodating to

sensor placement

Denning 6

Design and Testing of 1 kW Hall Thruster

Dimensioning

Denning 7

� Sizing convention from

Russian Hall thruster

designers as presented at

MIT in 1991

� Discharge chamber

diameter of 100 mm was

chosen to give

approximately 1 kW

power output.

Source: http://www.engin.umich.edu/dept/aero/spacelab/pdf/1999_gulczinski_thesis.pdf

Design and Testing of 1 kW Hall Thruster

Discharge Chamber

� Multiple plate design to

accommodate sensor

placement

� Compression plates

required to hold plates

in place

Denning 8

Design and Testing of 1 kW Hall Thruster

Anode

� Spacers incorporated to

vary anode height

� Allowed for fine tuning

of thruster output

Denning 9

Design and Testing of 1 kW Hall Thruster

Thruster Cross-Section

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Design and Testing of 1 kW Hall Thruster

Thermal Analysis

� Steady state thermal modeling of the thruster was

performed in ePhysics

� Model was fit to match results published by

previous Hall thruster researchers

Denning 11

Design and Testing of 1 kW Hall Thruster

Magnetic Analysis

� Design analysis was

performed using Finite

Element Method

Magnetics (FEMM)

� Effects from coil current

and shields height

variations quickly

calculated

Denning 12

Design and Testing of 1 kW Hall Thruster

Magnetic Analysis continued

Denning 13

Design and Testing of 1 kW Hall Thruster

Magnetic Analysis continued

� Maxwell 3D magnetic modeling verified FEMM

resultsDenning 14

Design and Testing of 1 kW Hall Thruster

Magnetic Field Mapping

� Magnetic field mapped using two axis stage and

Gauss meter

Denning 15

Design and Testing of 1 kW Hall Thruster

Equipment

� Steel vacuum chamber ( 5 ft. diameter , 15 ft. in length) to simulate space vacuum

� Pumps: Edwards GV250 dry mechanical pump, Edwards EH-1200 mechanical booster pump, and two Varian HS-20 diffusion pumps (35,000 l/s pumping speed for air)

� Baseline pressure in the high 10-6 Torr range (10-5 range during thruster operation)

Denning 16

Design and Testing of 1 kW Hall Thruster

Denning 17

Equipment continued

Design and Testing of 1 kW Hall Thruster

Testing

Denning 18

Design and Testing of 1 kW Hall Thruster

Results

� The thruster demonstrated steady operation in the

following modes operating on argon

Denning 19

Cathode Flow Rate

(sccm)

Anode Flow Rate

(sccm)

Discharge Voltage

(V)

Discharge Current

(A)

Discharge Power (W)

5 55 154 2.02 311

5 60 146 2.79 407

5 100 125 4.95 618

Design and Testing of 1 kW Hall Thruster

Thermocouple Placements

Denning 20

Design and Testing of 1 kW Hall Thruster

Thermal Measurements

Thruster Operating Temperature

0

20

40

60

80

100

120

140

160

0 25 50 75 100 125 150 175 200 225 250

Thruster Firing Time (min)

Tem

pra

ture

(°C

)

Base Plate

Thrust Stand

Outer Coil

Outer Pole Piece

Outer Shield

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Design and Testing of 1 kW Hall Thruster

Problems Encountered

� Magnetic core saturation

Denning 22

1 2 3 4 5 6 7 8 9 100

20

40

60

80

100

120

Axial coordinate,cm

Br,

ga

uss

inner coil - 0.5A, outer coil - 1 A

inner coil - 0.5A, outer coil - 2 A

inner coil -1A, outer coil - 1 A

inner coil - 1A, outer coil - 2 A

inner coil - 1A, outer coil - 3 A

inner coil - 1.5A, outer coil - 2 A

inner coil - 1.5A, outer coil - 3 A

Anodelocation

Exitplane

Courtesy of www.allaboutcircuits.com

Design and Testing of 1 kW Hall Thruster

Problems Encountered

� Remaining magnet field

(remanence) inhibited

thruster restart

� Procedure implemented

to reverse field

Denning 23

Courtesy of hyperphysics.phy-astr.gsu.edu

Design and Testing of 1 kW Hall Thruster

Problems Encountered

� Conductive layer built

up on discharge

chamber

� Caused anode to short

� Prevented thruster

restart

Denning 24

Design and Testing of 1 kW Hall Thruster

Future Work

� Improve the strength of the magnetic field

(thicker central core, better magnetic material)

� Fine tuning of anode height

� Complete accurate thermal map

� Integration of sensors

Denning 25

Design and Testing of 1 kW Hall Thruster

Questions

Denning 26

Design and Testing of 1 kW Hall Thruster

Conventional Ion Thrusters

� Ions accelerated through

grids

� Space charge limited

� Ion current density

restricted

� Thrust restricted

Denning 27

Courtesy of NASA

Design and Testing of 1 kW Hall Thruster

Hall Thruster Advantage

� Formation of quasi-

neutral plasma

� Not space charge

limited

� Higher thrust to weight

ratio

Denning 28

Courtesy of Drexel University