,

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_ .. _

NASA/TM-2003-211879 AIAA- 2002-4257 

! . High Voltage TAL Erosion Characterization 

David T. Jacobson 

Glenn Research Center, Cleveland, Ohio 

. ! 

d 

February 2003 

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NASA/TM-2003-211879 AIAA-2002-4257 

High Voltage TAL Erosion Characterization 

David T. Jacobson 

Glenn Research Center, Cleveland, Ohio 

Prepared for the 

38th Joint Propulsion Conference and Exhibit 

cosponsored by AIAA, ASME, SAE, and ASEE 

Indianapolis, Indiana, July 7-10, 2002 

National Aeronautics and 

Space Administration 

Glenn Research Center 

February 2003 
NASA Center for Aerospace Information 

7121 Standard Drive 

Hanover, MD 21076 

Available from 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22100 

Available electronically at http: //gltrs.grc.nasa.gov 
High Voltage TAL Erosion Characterization 

David T. Jacobson 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

Extended operation of a D-80 anode Layer thruster at high voLtage was investigated. The thruster was operated fo r 

1200 hours at 700 Volts and 4 Amperes. Laser profilometry was employed to quantify the erosion of the thruster's 

graphite guard rings and electrodes at 0, 300, 600, 900 and 1200 hours. Thruster performance and electricaL 

characteristics were monitored over the duration of the investigation. The guard rings exhibited asymmetric 

erosion that was greatest in the region of the cathode. Erosion of the guard rings exposed the magnet poles between 

600-900 hours of operation. 

Introduction 

In 1999, the NASA Glenn Research Center began 

investigating Hall thrusters with specific impulses 

greater than the 1500 to 1700 seconds of state-of-theart thrusters. l

--1 This increase in specific impulse over 

conventional xenon Hall thrusters was achieved by 

increasing discharge voltages from 300 Volts up to 

1700 Volts. Operation at these elevated discharge 

voltages substantially increased the kinetic energy of 

the ions produced during thruster operation. At any 

discharge voltage, some small fraction of the ions 

accelerated by the thruster impinge upon the thruster 

itself, eroding critical components, eventually 

causing the thruster to wear out. While experiments 

have shown this experimentally, the effect of 

discharge voltages in excess of 500 Volts on thruster 

lifetime has not been comprehensively investigated. 

Past experiments at lower discharge voltages include 

qualification testing of the SPT -100 thruster for over 

7000 hours at Fakel, and over 5000 hours at JPL.S-<i 

Both of these tests were conducted at discharge 

voltages of 300 Volts. A similar test of the SPT-1 40, 

at a discharge voltage of 300 Volts, is also currently 

underway.7 Published anode layer life tests include a 

636 hour test conducted at a discharge voltage of 300 

Volts using the 0 -55 thruster,S and a 1000 hour test 

of the TAL-110 thruster operating at a discharge 

voltage of 350 Volts.

9 A 1000 hour erosion 

characterization test of the SPT-type T-220 thruster 

was conducted at a discharge voltage of 500 Volts.

IO 

This investigation was the first published extended 

duration test of a Hall thruster at elevated discharge 

voltages. The results of each these tests confirmed 

that thruster erosion due to ion impingement 

determines thruster operational lifetime for both SPTtype and TAL-type Hall thrusters. 

NASAfTM-2003-211879 

The objecti ve of the current investigation was to 

evaluate the effect of high voltage operation on 

thruster erosion. Specifical ly, a 0-80 anode layer 

thruster was operated at a discharge voltage of 700 

Volts. A 700 Volt discharge voltage was selected 

because a previous performance investigation of the 

thruster demonstrated maximum thruster efficiency at 

discharge voltages between 500 and 800 Volts. 1 

Furthermore, thruster efficiency was shown to 

increase linearly with thruster power. A 4 Amperes 

discharge current was selected for extended operation 

because this was the maximum value that could be 

achieved while maintaining the desired steady state 

thermal conditions. The anode efficiency and 

specific impulse at this operating point were 57% and 

2625 seconds, respectively. While efficiency over 

70% and specific impulse over 4000 seconds were 

demonstrated at higher discharge voltages and 

currents, high thruster temperature prohibited 

operation for extended peliods of time. The thruster 

was operated for a total duration of 1200 hours in this 

investigation. Erosion of critical thruster components 

was evaluated every 300 hours. The results of this 

evaluation are presented. 

Apparatus and Procedure 

The 0-80 was built under contract with Boeing 

Rocketdyne and was fabricated by their 

subcontractor, the Central Research Institute of 

Machine Building (TsNIMASH). The 0-80 was 

capable of two-stage operation, but was operated in 

the single stage configuration for the erosion test. 

The performance test results indicated that singlestage performance was equivalent or better than twostage performance in the high voltage, high 
efficiency regime. Details of the thruster design and 

the performance data were previously described. 1. 11 

This investigation was conducted in Vacuum Facility 

12 at NASA Glenn Research Center. The chamber 

was 3 meters in diameter and 9 meters in length. The 

pumping capability was approximately 4.6xlOs 

liters/sec calculated fo r xenon. The facility pressure 

during testing was approximately 1.0 x 10-0 torr. The 

pressure was measured using an ionization gauge 

located on the chamber waH, in the same plane as 

thruster. 

A laboratory power system consIstmg of 

commercially avail able power supplies was used to 

operate the discharge, cathode heater, keeper, inner 

and outer magnets. A PC based data acquisition 

system was used to record data throughout testing. 

Unattended operation was implemented using upper 

and lower limits set on the discharge current, which 

shut down the thruster in the event of an anomaly. 

Xenon propellant was supplied to the anode and 

cathode using a laboratory feed system consisting of 

two commercially avai lable mass flow controllers. 

Constant volume flow calibrations were performed 

before and after the erosion test. 

An inverted pendulum thmst stand, previously 

described in detail, was used to monitor thrust over 

the course of the investigation. 12-13 To minimize the 

error resulting from zero drift, the inclination was 

adjusted once per 24 hours to the initial position and 

thrust recorded. The thrust stand calibration weights 

were cycled and a true zero was recorded each time 

the thruster was shutdown. While the infrequency of 

recording the zero and performing a calibration did 

increase the uncertainly in the tluust measurement, a 

performance investigation was previously conducted 

over a wide range of operating conditions. I The 

thrust was measured in this investigation only as an 

indication of nominal thruster operation over the test 

duration. 

Guard ring erosion was quantified after discrete 

periods of thruster operation. The thruster was 

operated in increments of 300 hours between 

voluntary shutdowns. Four test sequences were 

conducted for a total operating time of 1200 hours. 

Prior to the fust sequence and at the conclusion of 

each 300 hour increment, the thruster was removed 

from the vacuum chamber and a laser line profiling 

measurement technique was used to quantify the 

guard ring erosion. 

The laser line profiling technique was developed by 

Correlated Solutions, Incorporated for a previous 

Hall thruster erosion investigation. 10 A cylindrical 

lens was used to create a plane of light, which was 

NASAfTM-2003-211879 2 

projected on the guard ring and anode electrode. At 

the intersection of the object and light plane, a line of 

light was produced. The object was viewed from a 

different angle with a standard charge coupled device 

(CCD) camera and the depth of the object was 

directly related to the position of the line in the 

camera's inlage. A telecentric lens was used on the 

CCD camera to minimize the effect of image 

magnification. A generic representation of the 

method is depicted in Figure 1. A calibration system 

was used to relate the location of the line in the image 

and its depth in space. The calibration also 

established the zero point and magnification for the 

range of the measurement. The coordinates of the 

tluuster geometry images were resolved using the 

images collected during calibration. Each resolved 

image consisted of 480 x-y coordinates with an 

estimated error of less than 0.05 mm. 

The thruster was mounted to a rotation stage affixed 

to an aluminum frame. The laser was positioned so 

the laser line was perpendicular to the side of the 

thruster and the line crosses through the center of the 

thruster. This established a radial section of the ring 

being studied. A depiction of the apparatus is shown 

in Figure 2. 

After the system was setup and calibrated, the 

thruster was rotated in 10 increments and images of 

the inner guard ring and electrode were taken at each 

position. The apparatus was then reconfigur ed and 

images of the outer guard ring and electrode were 

collected in a similar fashion. 

Results and Discussion 

Five sets of images of the thruster channel were 

collected. Each set includes 360 images of the inner 

geometry and 360 images of the outer geometry. The 

first set of images was collected before the engine 

was operated for the erosion test. The engine had 

been operated for 26 hours during the performance 

test before the initial images were collected. 

Subsequent images were collected after 300, 600, 

900, and 1200 hours of operation. 

The profile of the tluuster magnet pole, guard ring, 1

st 

and 2

nd stage anode electrodes are captured in each 

image. The thruster components are labeled in a 

sample image in Figure 3. All fi ve of the profiles 

taken at each progressive time interval are included 

in the image. The profiles taken at 0 hours and 1200 

hours are also labeled in Figure 3. While the sample 

image depicts only inner geometry, images of both 

the inner and outer portions of the channel were 

collected at each azimuthal position. The zero 

reference was located at the 12 o' clock position, 

shown in Figure 4. All angles are measured counter 
clockwise from the zero reference. The locations at 

which the lines of each feature are connected are a 

result of the coordinate reduction process, and not 

true geometric features of the thruster. 

Images of the inner and outer geometry collected at 

the 0° and 180° positions, respecti vely, are presented 

in figures 5a and 5b. These figures reveal differences 

in the erosion around the circumference and also 

between the inner and outer geometry at the sanle 

angular location. Both the inner and outer ring 

profiles exhibit progressive erosion of the thruster 

components with time as expected. There are 

differences in the inner profiles taken at 0 and 180°. 

While the two inner profiles presented have a similar 

appearance for the first 300 hour increment, 

differences begin to appear over the later increments. 

The inner ring profile at the 0 degree location 

indicates that a larger amount of inner guard ling 

erosion had occurred compared to that at 180°. The 

900 hour increment profile taken at 0 ° indicates that 

the sufficient guard ring erosion occurred to expose 

the inner magnet pole to ion impingement causing 

inner magnet pole erosion. At the 180° location, the 

inner guard ring erosion was low enough to protect 

the magnet pole for the entire duration of the 

experiment. While the magnitude of the differences 

in erosion are smaller, the same erosion phenomenon 

exists in the case of the outer guard ring. A larger 

amount of material was removed at the 0 degree 

location compared to that at 180 0 . 

Figures 5a and 5b also show a change in the 2

nd stage 

anode electrode geometry with time. The 

downstream tip of the electrode increased in length 

by approximately 0.5 mm over 1200 hours. This 

phenomenon was also evident on the surface of the 

electrode although to a lesser magnitude. The change 

was consistent around the circumference and present 

on both the inner and outer portions of the anode. A 

visual inspection of the hardware revealed that the 

anode surface was coated with a loosely affixed 

material, which appeared to be graphite. While the 

D-80 had a graphite anode, the surface appearance 

changed over time. The downstream tip appeared to 

have small cracks or separation of the surface, which 

caused the change in geometry seen in the profiles. It 

is possible that this condition was a result of long 

term, high temperature operation. While less likely, 

the loosely affixed material on the anode surface 

could have been caused by deposition. The material 

could have originated from the thruster's graphite 

guard rings or the facility. Because the guard rings 

and the anode were both made from graphite, 

determining the origin of the coating on the anode 

was not possible. No tests were conducted to 

definitely understand the phenomenon. 

NASAITM-2003-211879 3 

Using the images of the thruster geometry, the 

volume of material eroded over each 300 hour 

increment was calculated for each location around the 

circumference of the thruster channel. A numerical 

integration was performed for each degree, assuming 

a constant erosion profile over the arc length. The 

eroded volume calculation was performed for inner 

and outer guard rings and the inner and outer magnet 

poles. The region selected for the calculations is 

depicted in Figure 6. The region selected for the 

magnet pole volume calculation was smaller than that 

used for the guard ring volume calculation. The 

magnet pole regions were restricted due to reflections 

of laser light and discontinuities caused by screw 

holes on the surface of the pole. 

The calculated volumes of eroded inner and outer 

thruster components are provided in Table 1. The 

volume is a summation of the individual values 

calculated at each degree over each 300 hour time 

increment. The volume of graphite removed from the 

inner and outer guard rings are tabulated separately 

from the volume of metal removed from the poles. 

The volume of guard ring material removed was 

added to the volume of magnet pole material 

removed for the inner and outer geometry. These 

values of the total erosion are also presented in the 

Table. The volume of graphite that eroded from the 

inner and outer guard rings decreased with time, as 

the amount of graphite exposed to energetic ions 

decreased. As the guard rings eroded, the magnet 

poles were exposed to ion impingement, and the 

amount of magnet pole material eroded increased as 

expected. 

The volume of graphite eroded from the inner and 

outer guard rings at each degree is presented in 

Figures 7 and 8, respectively. Similar plots of the 

metallic volume removed from the inner and outer 

magnet poles are presented in Figures 9 and 10. The 

eroded volume of the outer ring is fairly consistent 

around the circumference over the first 300 hours. 

One exception is an unexplained sharp decrease in 

eroded volume observed between 270° and 310°. 

During subsequent operation intervals, the erosion 

became increasingly Jess consistent around the 

circumference. The eroded volume gradually 

decreased from 40° to a minimum at 200°, then 

increased to 270° where it remained fairly constant to 

40°. Similar trends are exhibited in the case of the 

inner component erosion. This asymmetric guard ring 

erosion caused erosion of the inner magnet pole. 

Figure 9 shows the eroded volume of the inner pole, 

which occurred almost exclusively between 0° to 80° 

and 310° to 360°. Figure 10 indicates that the outer 

magnet pole erosion was more consistent around the 

circumference than the inner pole. The sharp change 
in eroded volume between 270° and 310° observed in 

the outer guard ring erosion was also present in the 

outer pole erosion. 

It is evident that the erosion rate was elevated in the 

vicinity of the cathode. For both the inner and outer 

rings, a larger volume of materi al was eroded 

between 40° and 270°. A previous Hall thmster 

erosion test identified discharge chan1ber 

misalignment with respect to the magnetic field as 

the cause for asymmetric erosion. ' 0 Misalignment of 

the channel caused elevated erosion on the inner 

portion of the channel, and lower erosion on the outer 

portion, wruch is not observed in trus case. A 

previous TAL erosion study correlated the location of 

peak thmster erosion with local magnetic field 

minimums at locations between the electromagnets." 

In that investigation, the eroded volume was periodic 

with maximum erosion in regions of low radial 

magnetic field and minimum erosion in regions of 

high magnetic field strength. The D-SO erosion was 

not periodic, nor was the magnetic circuit design 

suspected as a cause for the asymmetric erosion. . 

In trus case, the localized elevated erosion was likely 

caused by heavy particle impingement to wruch the 

other portions of the channel were not subjected. The 

particles are thought to be either ions generated in the 

cathode, or charge exchange ions created by 

collisions with neutrals escaping from the discharge 

or cathode. Simple kinetic theory calculations were 

made to understand the competing effects of the 

different particles. The path length for charge 

exchange was estimated using the background 

pressure and charge cross section for 700 e V ions. '5 

The percentage of charge exchange ions was then 

calculated for the distance between the cathode and 

the region of elevated erosion. The calculation 

revealed that only a fraction of a percent of the 

discharge ions exchange charge.' The calculation was 

also performed using an estimated neutral pressure at 

the exit of the cathode. At the elevated pressure, a 

more significant percentage of ions exchange charge. 

Because the ionization fraction of hollow cathodes is 

assumed to be small, the dominant effect could 

potentially be charge exchange ions due to cathode 

operation. A calculation using the charge exchange 

ion flux to the region of elevated erosion would need 

to be made to determine if these particles are 

responsible for the localized erosion phenomenon. 

Cathode flow rate had an effect on thruster operation. 

Discharge current oscillations ranged from O.S to 1.4 

Amperes. At cathode flow rates below 0.6 mg/s 

significantly larger discharge current oscillations 

were measured. Short duration,S Ampere oscillatory 

bursts were measured. These bursts were also 

NASAlTM-2003-211S79 4 

observed visually as the cathode plasma increased in 

luminosity. The oscillatory operati ng mode was not 

observed when the cathode mass flow rate was 

increased to O.S mg/s. A correlation between cathode 

operation, discharge current oscillations and erosion 

rate was discovered in a previous, long duration TAL 

experiment. 9 In that experiment, the cathode 

operating mode was shown to have an effect on 

discharge current oscillations. Additionally, the 

measured erosion rate was 3 times higher over the 

operating interval with elevated discharge current 

oscillations. While unlikely that the cathode flow 

rate and corresponding discharge current oscillations 

caused the asymmetric erosion, there may be some 

correlation with the overall erosion rate. Additional 

experiments would be required to definitely 

understand the effect of cathode operation on thruster 

erosion. 

The measured thmst remained constant over the 1200 

hours of operation. The thrust produced was lIS roN 

at the beginning and end of the experiment. The 

variation in thmst over the course of the experiment 

was less than ± 2%, wruch is within the measurement 

accuracy. The erosion of the guard rings and 

magnetic pole had a negligible effect of the 

performance of the D-SO over 1200 hours of 

operation. 

Conclusions 

A TAL thruster was operated for 1200 hours at 700 

Volts to assess the effect of rugh voltage operati9n on 

thmster erosion. A discharge voltage of 700 Volts 

was selected because peak thmster efficiency was 

previously demonstrated between 500 and SOO Volts. 

Because efficiency was also found to increase with 

thruster power, the thmster was operated at the 

ru ghest discharge current below the thruster's 

maximum desired temperature. 

A laser profilometry method was used to quantify the 

guard ring and magnet pole erosion. Five surveys of 

the discharge channel were made at 0, 300, 600, 900, 

and 1200 hours of operation. Both the inner and 

outer guard rings exrubited asymmetric erosion, 

which was elevated in the region of the cathode. 

Charge exchange collisions were suspected to have 

contributed to tbe localized erosion. While simple 

kinetic theory calculations were made to assess the 

plausibility of this scenario, additional experiments 

and calculations would be required to definitely 

determine the cause. 

The measured thmst remained constant over the 

duration of the experiment, indicating that the erosion 

of the guard rings and pole pieces did not affect the 

_J 
performance of the device. While the guard ring' 

effectiveness was compromised between 600 and 900 

hours, nominal thru ter operation was maintai ned up 

to 1200 hours. 

References 

l. Jacobson, D.T., Jankovsky, R.S., Rawun, V.K. , 

Manzella, D.H., "Performance of a High Voltage 

TAL," AlAA- 01 -3777, July 2001. 

2. Manzell a, D.H. , Jacobson, D.T. , "High Voltage 

SPT Performance," AlAA- 2001-3774, July 

2001. 

3. Jankovsky, R.S., et aI., "NASA's Hall Thruster 

Program," ALAA-O l- 3888, July 2001. 

4. Hofer, R.R., Peterson, P.Y., Gallimore, A.D., "A 

High Specific Impul e Two-Stage Hall Thruster 

with Pia rna Len Focusing," IEPC- 01-036, 

October 200 I . 

5. Day, D. , Maslenniov, ., Randolph, T. , Rogers, 

W., "SPT- IOO Subsy tern Qual ification Status," 

AIAA-96-27 13, July 1996. 

6. Garner, C.E., Brophy, J.R. , Polk, I.E. , Pless, 

L.c. , "A 5730 Hr Cyclic Endurance Te t of The 

SPT-100," AlAA- 95- 2667, July 1995. 

7. Spanjer , G.G., et aI. , "The USAF Electric 

Propulsion Research Program," AlAA- 3146, 

July 2000. 

ASAffM-2003-21 1879 5 

8. Gamer, C.E., et aI. , "Experimental Evaluation of 

Russian Anode Layer Thrusters," AlAA- 94-

3010, June 1994. 

9. Semenkin A.V. , et ai. , "Development program 

and preliminary re ults of the TAL- I 10 

thruster," AlAA- 99-2279, June 1999. 

10. Mason, L.S., Manzella, D.H., "1000 Hour of 

Testing on a 10 J(jlowatt Hall Effect Thru ter," 

AlAA- 01 - 3773, July 200 1. 

II . Butler G. W., et aI., "Multi-Mode High Specific 

Impulse Hall Thruster," AIAA-2000-3254 July 

2000. 

12. Haag, T.W., Manzella, D.M., "RHETTIEPDM 

Performance Characterization." IEPC-97- I07, 

August 1997. 

13. Jacob on, D.T., Jankov ky, R.S., "Te t 

Results of a 200 W Class Hall Thruster," 

ASAffM- 1999-209449. 

14. Marrese, C., et aI. , "Analysi of Anode Layer 

Thruster Guard Ring Ero ion," IEPC- 95- 196, 

September 1995. 

15. Pullins, S., et aI., "Ion Dynamics in Hall Effect 

and Ion Thrusters: Xe+ + Xe Symmetric Charge 

Transfer," AIAA 2000-0603, January 2000. 

-- --- --
Hours 

300 

600 

900 

1200 

Table 1: Volume of eroded material from inner and outer thruster geometry. 

Inner 

Graphite 

(mm3

) 

3 19 

122 

72 

53 

Inner Pole 

Metal 

(mm3

) 

31 

-3 

22 

78 

Scan 

hod 

Laser Line 

Source 

Inner Total 

(mm3

) 

350 

11 9 

94 

131 

Outer Outer Pole Outer Total 

Graphite Metal (mm3

) 

(mnl) (mm3

) 

528 - 1 527 

358 37 395 

200 143 343 

120 353 473 

Figure I : Generic representation of laser line profiling measurement method employed. 

Scan CCDc:am~ra 

) Laser Une source 

~ t----

~, ... ;',,~: .. 

.. ::::\::: 

~ I I ::l ~ l 

PC with digitizer 1. Rotation Stage 

Figure 2: Schematic of the circumferential measurement apparatu . 

NASAlTM-2003-2 11 879 6 
_ ........ _ ...... . 

Magnet Pole T=O hours 

Guard Ring 

e:-

-6 

I 1r 2"StageAoode 

! T= 1200 hours 

N 

1" Stage Anode 

~ 30 ~ 

Y(mm) 

Figure 3: Sample image with geometric feature of D-80 Hall thru ter labeled. 

Figure 4: Zero position denoted on the 0 -80 Hall thruster used in the ero ion in vestigati on. 

ASArrM-2003-2ll879 7 
I nner Ring Profile 

30 35 

Y(mm) 

Outer Ring Profile 

45 50 

Y(mm) 

Hours 

o 

300 

600 

900 

1200 

.55 

Figure Sa: Ax ial coordinate versus radial coordinate for magnet pole/anode/guard ring profile measured at 0, 300, 

600, 900, 1200 hour . (0 0 azimuthal location) 

Inner Ring Profile 

25 30 35 

Y(mm) 

Outer Ring Profile 

45 50 

Y(mm) 

Hours 

o 

300 

600 

900 

1200 

55 

Figure Sb: Axial coordinate vers us radi al coordinate for magnet pole/anode/guard ring profile measured at 0, 300, 

600, 900, 1200 hours. ( 1800 azimuthal location) 

ASNTM-2003-2 11 879 8 
.::--

E 

E 

'-" 

-0 

Q) 

-0 

0 

..... 

\l.l 

~ .c 

a. 

(\l 

..... 

0 

..... 

<!) 

c 

c 

...... 

<!) 

E 

::J 

(3 

> 

----- ----------

Inner Ring Profile 

2 

.A i Volume 

;: Calculation 

Region 

"f ~ 

-16 

-18 2~ I I 

30 35 

Y(mm) 

2 

o 

-2 

_ -8 

E 

E -a N 

-10 

-12 

.... ~ ... 

Oular Ring Profile 

Region 

5 50 55 Y(mm) 

Figure 6: Region selected for volume calculation of eroded material. 

4 

Time Increment 

0-300 

3 300-600 

600-900 

900-1200 

2 

00 100 200 300 

Discharge chamber location (degrees) 

Figure 7: Volume of inner guard ring graphite removed at azimuthal locations between 0-360 degrees. 

3 

2 

. '1~~ j 1. " 1'~ 't'lIvJJ~~ , Time In V'~~fI" 0-300 

300-600 

600-900 

900-1200 

1 00 200 300 

Discharge chamber location (degrees) 

Figure 8: Volume of outer guard ring graphite removed at azimuthal location between 0-360 degrees. 

ASArrM-2003-2l1879 9 
---. 

1 

"0 

o 

"0 

8 

w 

o 

4 

3 

o 2 0... 

to 

c: 

c: 

...... 

o 

E 

:::l 

o 

> 

Time Increment 

0-300 

300-600 

600-900 

900-1200 

0 0 100 200 

Di charge chamber location (degree) 

Figure 9: Volume of inner magnet pole removed at azimuthal locations between 0-360 degree _ 

"0 

o 

"0 

~ o 

4 

3 

o 

0... 2 t8 

:::l 

o 

o 

E 

.2 

o 

> 

o ' 

o 

Time Increment 

0-300 

300-600 

600-900 

900-1200 

A, '." f'v' 

r 

.-" , { 

200 

Discharge chamber location (degrees) 

300 

Figure 10: Volume of outer magnet pole removed at azimuthal locations between 0-360 degrees_ 

ASAlTM-2003-21 1879 10 
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4. TITLE AND SUBTITLE 5. FUNDING NUMBERS 

High Voltage TAL Erosion Characterization 

6. AUTHOR(S) VVBS-22-755-04-12 

David T. Jacobson 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8 . PERFORMING ORGANIZATION 

REPORT NUMBER 

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field E-13561 

Cleveland, Ohio 44135-319 1 

9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORINGIMONITORING 

AGENCY REPORT NUMBER 

National Aeronautics and Space Administration 

Washington, DC 20546-0001 NASA TM-2003-211879 

AIAA-2002-4257 

11 . SUPPLEMENTARY NOTES 

Prepared for the 38th Joint Propulsion Conference and Exhibit cosponsored by AIAA, ASME, SAE, and ASEE, 

Indianapolis, Indiana, July 7-10, 2002. Responsible person, David T. Jacobson, organi zation code 5430, 216-433-3691. 

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE 

Unclassified - Unlimited 

Subject Category: 20 Distribution: Nonstandard 

Available electronically at http://gltrs.grc.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 301-621-0390. 

13. A BSTRACT (Maximum 200 words) 

Extended operation of a D-80 anode layer thruster at high voltage was investigated. The thruster was operated for 

1200 hours at 700 Volts and 4 Amperes. Laser profilometry was employed to quantify the erosion of the thruster's graphite 

guard rings and electrodes at 0,300, 600, 900, and 1200 hours. Thruster performance and electrical characteristics were 

monitored over the duration of the investigation. The guard rings exhibited asymmetric erosion that was greatest in the 

region of the cathode_ Erosion of the guard rings exposed the magnet poles between 600 to 900 hours of operation. 

14. SUBJECT TERMS 15. NUMBER OF PAGES 

16 

Electric propulsion; Electrostatic thruster; Spacecraft propulsion 16. PRICE CODE 

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT 

OF REPORT OFTHIS PAGE OF ABSTRACT 

Unclassified Unclassified Unclassified 

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) 

Prescribed by ANSI Std. Z39-18 

2 9B-l02