The topics are presented in viewgraph form and include the following: overall strategy for magnetoplasmadynamic (MPD) thruster development; high power MPD flows; moderate power MPD thrusters and components; qualitative spectroscopic studies of magnetic nozzle flow; hollow cathode studies; and anode flow studies

Turchi, Peter J.

English

NASA Technical Reports Server

N93"
MAGNETOPLASMADYNAMIC THRUSTER FLOWS: PROBLEMS AND PROGRESS
Peter J. Turchi
The Ohio State University
Columbus, Ohio
1 642
MPD THRUSTER WORKSHOP
OVERALL STRATEGY FOR MPD THRUSTER DEVELOPMENT
NEEDS
Efficiency
Lifetime
PROBLEMS
Exhaust flow
-- Angular spread
-- Frozen flow
hRREQECK_
Magnetic nozzle
-- Flow collimation
-- Expansion control
Design/control of
thrust chamber plasma
Electrodes
-- Voltage drops
-- Heat transfer
-- Erosion
Design/control of
near-electrode plasma
-- Hollow cathode
-- Anode MPD flow
117
https://ntrs.nasa.gov/search.jsp?R=19930009453 2020-03-17T07:52:14+00:00Z
MPD THRUSTER WORKSHOP
ACTIVITIES IN THE OSU AERO/ASTRO ENGINEERING DEPARTMENT
HIGH pOWER MPD FLOWS
-- Godzilla
Gigawatt, quasi-steady, LC-ladder pulseline
(3 kV matched-load, with 333 kA for 1.6 msec;
also iii kA for 4.8 msec, etc.)
MODERATE POWER MPD THRUSTERS AND COMPONENTS
-- Magnetic nozzle experiments
Qualitative spectroscopic studies
Long pulse, applied field (York)
-- Hollow cathode studies
Theoretical modeling
Experiments at NASA LeRC in both MPD and ion
engine regimes
-- Applied-field MPD flow modeling
MACH2 code adapted to steady, applied-field
operation
Examination of flow near the anode
118
_PD THRUSTER WORKSHOP
TOPIC PARTICIPANT
Magnetic nozzle spectroscopy T. Umeki, MS student, Ohio Stats
Hollow cathode studies A. Salhi, PhD student, Ohio State
R. Myers, M. Man_enieks, NASA LeRC,
(for experimeacs)
Anode flow studies P.G. Mikellides, PhD student, Ohio St
N.F. Roderick, Professor, Dept. of
Chemical and Nuclear Engineering,
University of New Mexico
MPD THRUSTER WORKSHOP
QUALITATIVE SPECTROSCOPIC STUDIES OF MAGNETIC NOZZLE FLOW
MOTIVATION
--B
APPROACH
Build on earlier studies, based on electrostatic
probes, pressure probes, magnetic probes, and
single-point laser scattering, to estimate
energetics of magnetic nozzle flow field.
Attempt to capture larger region of flow field
through spectroscopic flow-visualization.
Combine spectroscopy with photographic imaging in
order to obtain (qualitatively) line intensities as
function of position in flow field.
Perform photoelectric measurements of selected lines.
Compare with available probe data ( at downstream
positions).
Examine distributions of derived plasma parameters
(e.g., electron temperature, electron and heavy
particle densities).
119
Pyrex Duct
A
U
6
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III
14
,,=4
1=-4
4
-f-I
al
Anode
Ca Chode
iS
Applied Hagneclc
Field Coil
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0
0 5 10 IS 20 2 "_
Axial Dtscanca (c=)
Applied maRnetie Eie[d lines
B,
u
,I
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m
3.0
2.0
1.0
HI (Applied & Self) Wl (Applied & Self)
[, I _ i [
0.0 1.O 2.0 3.0 4.0 S.0
NII (Self)
NII (AppI ied)
Axial position(z) [ca]
Species distribution
120
0.10
>=
_._
1.00
C
0
L
_J
®
, 3919 
%
%
' 4227A
- ,
0.01 I ,, I I I
0.01.02.03.04.05.0
App. field case
Self field case
App. field case
Self field case
Axial position [cm]
Chordal averaged radiator
number density on the
axial position
® App. field case
® Self field case
>
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=
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t;
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%
%
%
K
| &, I
0.0 1.0 2.0 3.0 4.0 5.0
Axial position [cm]
Electron temperature
on the axial position
(chordal averaged on axis)
121
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l
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for the electron number
density
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@
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Applied field case
Self field case
%
' ' . I ,, ,I
0.0 1.0 2.0 3.0 4.0 5.0
Axial position[cm]
Electron number density
on the axial position
from Stark broadening
(chordal averaged on axis)
122
MPD THRUSTER WORKSHOP
HOLLOW CATHODE STUDIES
MOTIVATION
Improve cathode performance in MPD arcjets by
controlling the plasma near the cathode surface,
(rather than merely accepting the plasma conditions
provided by the thrust chamber flow).
Extend understanding of hollow cathode design to
embrace both low current and high current regimes.
Start theoretical modeling from the notion of
reducing losses from the vicinity of the cathode by
operating in a hohlraum, and at high current
density.
Cast model in terms of operating values of current,
and mass flow rate, material properties, and cathode
dimensions. Extend from first-principles only as
needed to encompass new aspects of operation.
Compare theory with existing data, and generate new
data to test model.
123
• &i4odol FOr Ko!low Cathode Dimoharge
I
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FIGURE 31: Equipotent;ot ond Current Lines ( Io = 3.3 A )
124
_600
1500
1400
1300
(..)
v 1200
1100
1000
9OO
800
0
Mercury
;_ow Rote: 4,00 mA
Orifice Oiometer 0.96 mm
L/O = 56 -- ]'neory ( _s -- !.ga eV )
0 = 3.9 mm C Exc, eriment
C
Figure 1
1 2 3 4 5
'o (A)
Effect of Discncrge Current on Emission Surfcce
Temperature
1.8
f.6
1.4
1.2
> 1,0,
v
0.8
p-
0.6
0.4
0.2
0.0
0
Mercury
_low Rote: 100 mA
Orifice Diameter: 0.96 mm
L/O = 56 -- Theory ( ;o I _ _.94 eV )
0 = 3 9 r_,m 0 Exper;met'l
1 2 3 4
o (A).
F;gure 2 : Effect of D;sc'_or(:je Current on Fllectror_
Temoeroture
125
16
14
2
0
0
:2
_.0
>_
8
6
MercLry
t-'lowRcte: _3(3 n"A
Or;fTce Diome_er: 096 mm
L/D = ..56 -- Theo,y ( ;#_ _ '94 eV )
?_ = 3.3 mrn 0 Expe,'_er"
L ,, i L i
! 2 .3 ¢ 5
F;gure 3 : Effec: of D;schc-ge Currer_t on P!csmc -_,"):e't,:cl
4
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L]
3v
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x
(#
Z 2
0
0
Merc{jry
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Or;f;ce O;cmeter: 096 mm
L/O = 56 -- T_ec:ry ( ¢,_ = 194 eV )
O = .3 _).ram C E,oe,irre_:
0
i L i ,
1 2 .3 4
C (A;
Figure 4 : Effect of 0;scr:.orge C,sr,'e_' or" _'csmo .]e_sty
126
1600
1500
1400
1300
L)
1200
_ooo
900
Mercury
O;schorge Co,re^_: .],3 A
C)rlf;ceZ);ome|er:0.95 mm
L/O = 56 -- "rheo,'y( _, = ' 94 ev }
O E x,-"}_, r _ en t
0 0
800 ' ' '
0 1 2 3 4 5
Figure 5 : Effec: of Pressure o_ Er_;ssion Surface
Temperoture
]lell Ja_ 6
Id _< 3O A
Probe
__ 8 lh_rn gwaged Heate_ I
Impregnated Insert / /__ Molybdenum-Rhenium I
_.21_..0_1.o-)\ / /c._od. _o_y I
// . /_ /--296 _horLated Tungsten
// // // Origice Plate
i '--/ Plasma /
t ILl
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& _rypical lb{perimemtal &_rangement og HCA
127
__:.Z
"_'_'_ Impregnated
[0.SQ u ZD
___ Anode
8ahematla Representation of Hollow Ca_hod_
128
MPD THRUSTER WORKSHOP
ANODE FLOW-FIELD STUDIES
MOTIVATION
Present moderate power MPD arcjets appear to be
losing substantial fractions of the input power near
the anode. We need to understand the MPD flow field
near the anode in order to improve performance.
APPROACH
Accept that there are too many competing mechanisms
in the vicinity of the anode surface to proceed
confidently in predicting the flow-field densities,
temperatures, Hall parameters, etc.
Use a state-of-the-art MHD code (MACH2) to perform
the arithmetic in a self-consistent fashion to
describe the flow-field. Develop and extend models
(and MACH2) from this description of the flow-field.
Explore flow-field behavior to develop candidates for
improved performance.
MPD THRUSTER WORKSHOP
NEW THINGS IN MACH2 SINCE LAST YEAR'S WORKSHOP
Two-temperature (heavy-particle vs electron)
equation-of-state is now available within SESAME
tables.
Magnetic field generation routines and boundary
conditions for steady-F_ poloidal (rz) magnetic
fields due to both plasma currents and external
field coils have been added.
-- Magnetic fields due to external coils with
(specified) time-varying currents are also included.
129
MACHZ STUD[E% OP APPLIED FIELD HPb ARCUET
PROPELLANT : ARGON
MASS FLOW RATE : 0.t _/s
DISCHARGE CURRENT: 1OOO Amp
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130
STUDIES OF APPLIED FIELD
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TEMPERATURE
131
MPD THRUSTER WORKSHOP
ISSUES
PHILOSOPHICAT.T.y
"Ah Love, if you and I with Fate but could conspire
To grasp this sorry scheme of things entire,
Would not we shatter it to bits,
And remold it nearer to the heart's desire"
- Omar/Fitzgerald
PROGRAMMTICAT.T.y
Designing what we want vs Cataloging what we have
132


Magnetoplasmadynamic thruster flows: Problems and progress

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