Some of the topics covered with respect to the Lawrence Livermore National Laboratory's (LLNL's) contributions to Magnetoplasmadynamic (MPD) Thrusters for the Space Exploration Initiative (SEI) include: an IR camera, plasma-induced erosion/redeposition, the Mirror Fusion Test Facility-B (MFTF-B), the Thruster Lifetime Test Facility, the RACE Compact Torus Accelerator Facility, and a RACE program summary. Some of the other topics addressed include: flux contours for HAM simulation, comparison of RACE data of plasma ring formation with the HAM 2-D magnetohydrodynamic code, and the 2-D Ring Acceleration Code (TRAC)

Hooper, Edwin Bickford

English

NASA Technical Reports Server

AppendixF
LLNL - Contributions to MPD Thrusters
for SEI
MPD Thruster Technology Workshop
NASA, Washington, D.C.
E. Bickford Hooper
May 16, 1991
LLNL CAN CONTRIBUTE TO MPD THRUSTER
DEVELOPMENT FOR SEI
Hear term:
• Modeling of MHD characteristics using the TRAC code, which has been
benchmarked against the RACE experiment at LLNL
• Application of tokamak "divertor" physics
o Modeling of atomic - plasma interactions (gas penetration, ionization,
excitation, radiation) using the Brahms and Degas codes
o Measurements of MHD and atomic effects
o Modeling of erosion/sputtering and redeposition of refractory materials
• Remote measurements of density, temperature, magnetic field using fusion
diagnostics
These contributions can best be made in collaboration with ongoing experiments
Lonq term:
• High power tests for lifetime validation using the MFTF-B facility
F-I
https://ntrs.nasa.gov/search.jsp?R=19920000829 2020-03-17T14:50:19+00:00Z
Divertor IR camera
Oivertor IR
camera (165 :)
i
/i
I @ .
thermocouples --" _ _
.'_- iiii
Machine elevation !1 ill1285") I" i i
a_¢ ImIB
COMPARISON OF TANGENTIAL Ha DATA WITH DEGAS
i,- Simulated Midplane TV View
Contour Plot of H, From DEGAS
|' (Log Contours)-Symmetric Te Case ..
;_o......................"_ __ Ii _
_. "' ,_ ....,,_:..,: ,1( .:
L" ",,................._' _................"'_"_ _.
." " .. o.,..- _".• :::-"-,
_'_"........s--_t • RADIU
l_)de| _H41phe emleelon
Experimental Data From
Midplane Tangential Camera-
Note Decrease From X-point
To Midplane
F-2 ORIGINAL PAGE I!
OF POOR QUALIT_
The MFE community has developed considerable
expertise in plasma-induced erosion/redeposition
=.
=;
0
w
z
I
1.2
I.O
0.8
06
0.4
02 /
i /
0
ITER Divertor Model .
TUr:GSTEh: -- _
l\ 1:;_..........- 2oJ.h*t./A_;t ;1t[ {l_
,[I _,= " -.,G
-- 75 cV -- 12
i_ R_TE-- 6 5
-0 2 -- _Ocv l ,f_
-04 -- \ //
-OE--
' /
SEP.* R_T RIX I
I[
_L____,', I j_l_, I.__LLJ
40 EO 63 ICO 120 i.;O iE0
DIV[RTOR POINT. I :>5 mmlPOPIT
]. Brooks (ANI..) l:u._ion Tcchn. I.N__(I_)9l)) 23 _)
• Cornpuler codes such its
REDEP are used to predict
he_...!erosion including
redeposit ion. e ffect s
• These calculatiq_3s are
benchmarked against
meastlremelllS ill Iokamaks
and of f line simulation
facilities
THE MFTF-B t',
Solenoids
Neutral beams,
Vacuum vessel
Axic_ls
Neutral beams,._
High energy pump beam
• ECRH 9yrotrons
840kV beam
power supply
'Yin-Yang anchor cell
'_ Transition coils
ICRH antenna
Beam clump
F-3
PROPOSED THRUSTER LIFETIME TEST FACILITY
MFTF-B: Size 35' diameter by 200' long
1000 m3 of cryopanels
11 kW of LHe cooling available for pumping
500 kW closed loop LN2 system
250 MVA power line
Example test conditions: mass flow = 0.4 gls (thruster power = 1 MW at
v = 7x10 4 m/s)
Pumping speed
Equilibrium pressure
67x106 liters/s, D2
67x106 (4/A)112 liters/s,
Mass A
Hydrogen
Argon
5.2x10-5 torr
1.6x10-4 torr
The RACE experiment test the basic
concepts of ring acceleration
II pulse
Outor solenoid -
_opump
\\-Turbomolecular
pump
cone
1=-4
RACE Compact Torus Accelerator Facility I_
F-5 ORIGINAL PAGE IS
OF POOR QUALITY
RACE program summary
Goals Predictions Results to Date
Demonstrate ring formation
Demonstrate acceleration in
linear coaxial system
Demonstrate ring focusing
Magnetic energy
Mass
Length
Velocity
Energy
Efficiency
gkll,_llclUmagnluc
R=oc.,IR 0 -
2-40 kJ
5-500 microgram
70 cm
1-2 x 10 e cm/sec
Up to 100 kJ
0.4
5
1/5
2-10 kJ
5-500 microgram
50-100 cm
1-3 x 101cmlsec
5"0 ,Ira kJ"
O.3--O.4
10
,113
ORIGINAL PAGE IS
OF POOR QUALITY
1=-6
Comparison of race data of plasma ring
formation with the HAM 2D-MHD code
.13
For these calculations HAM:
1. Calculates the initial poloidal field allowing for
diffusion through conducting electrodes
2. Calculates the time-dependent gas density
distribution from an injected puff of gas
3. Calculates gas breakdown and plasma ring
formation using the gun capacitor bank
parameters
Flux contours for HAM simulation
i._--_-I._:-_. _ i I I ] I I I _Jg 2o_;)llm)), t:2.7,,s
1- I_ '+'l"l 'U .+.....
0 I I I I I t I
0 10 20 30 40 50 60 70 80 90 100
Z (cm)
L-_: _:;-; T _---+-- +" _ /
_" _-_-;- _ -- t = 4.5 ILS-I
0 ' _ ' ' : ; ! ,J
0 10 20 30 40 50 60 70 80 90 100
Z (cm)
_ 20 _))l/_ t = 3.s _,s-I
0 I I I I I i I I
0 10 20 30 40 50 60 70 80 90 100
Z (cm)
E t = 7.0 tlS
_" 20 ' - "" .... -
-_i--_-i_. :__+..... ........0 '- -1--_ I i l i I /
0 20 40 60 80 100 120 140 160 180 200
Z (cm)
F-7
2D MHD simulations agree with the experimentally
observed current
Gun
current
(kAt
Oz
(koaus$)
Shol #1112
2.o"°_ , I ' I ' I ' 1 '
°
-2.0
•.4.0 •
4.0
4.0 I I I r_l i I i -I I -
9 11 13 15 17
1*me (microseconds)
Shot #1112
,o_ '1 I ' _.1 ' I ' I '
-0.6
-1.2 "
'" ,,, l_J'q, f ,-
9 11 13 15 17
1|me (m*croseconds)
• #tAMresult _ Espeflment_l Oata
1=-8 ORIGINAL PAGE IS
OF POOR QUALITY
RACE, the Ring ACcelerator Experiment, configuration
during precompressor tests L.I
2G.A.109G-03,40C
Gun
Solenoids electrodes
Insulators /_,q Accelerator
J'," 1 //Ii electroOes
/L_,., \ //11 I\
,_ _= _ (/l! _, I ,\
.........__,.. r--_t.._..,__.,
_..,,,,,., " ,,,.,_]J_ _" J I
._o_-_ II II Accelerator , I
_-'_ II ,,re-I i 1 ;
I I compressor
8 pulsed ! cone I
' gas valves 1 ! I _ _ _ 4<__...-.I._,_,_-..I
0 0.5 // 2.05 2.97
Z (m)
TRAC (Two-dimentional Ring
Acceleration Code) has been used to
model the RACE pre-compressor
=i_ i _ ',:_,
0 =0 i
30 - ',
! ,(cm) ,
,o __ ................,
0 100 200 10 20 30. 40
40 _ t = 10 I_S
33-
2.E,-
,, -, ITF
5¢
0 100 200
I : 12,.;S
3,0"
• Pr C1:_$
2;' i
11 (Cm;
L5
F-9 ORk_iNAL PPOE r_8
OF POOR QUALITY
Comparison of trac with shot 5554 (VAc c = 80 kV) IJ
Accelerator
current (kA)
B z (kG)
20-A.0490-0124
u¢!
400 I , l 3--_' ' = ' i i
300
200
100
0
1 ' I ' I ' I ' I
5.00 - i_,
/ I Magnetic fieJd in
4.00-J I%._d : pre-¢ompressor
, Y, --Da'-
3.00 ,/It,m .... TRAC
-2.00
1,00 i_
0! i , ,',, _ , j , ,
42.00 46.00 50.00 54.00 58.01
Time (psecs)
Comparison with shot 5554 cont'd
B Z vs. t at different locations in
straight section
a z (kG)
L
14
12
8
4
2
i iO,
-- Data
......... TRAC
Z=43
16
14
12
BzlkG) 10
8
6
4
2
O
i I * I i
Z=74
iI J ) J
O Z (kG) ,_,
(expt.) 4
42 46 50
Time (..: S)
12
8
4
54 56
- 16
kG
(TRAC) Z = 104
F-IO
CT accelerates and is stable after precompression L_
/
/
oI
/
/
o
1.91
2
1
0.12
0 I I I 0
0 35 40 45 50 55
Time (ILS)
1.53
_>
1.30 x.
"O1.04 o
0.89 ="Do
O
0.74
0.58 3
0.43
(Vertical offsets of lip probe signals proportional to axial location)
2G-A.1090-0340B
IKZ
CT in quasi-static pressure balance during
compression in conical electrodes
0
0
'1 I .I Jl
• H2 (101_s bank)
o Ar/Ne (601_s bank) • _• "• •
• H2(60_sbank ) ,•,,'' =_./.'." • •
• •._ 00 • •o •
• • o _.-0"'l_ .•oO
• o e='lJl__ •
• • ..L_._,o .
u ji--
•_.r i"be •o
I I t I J I t I I I I ' I _
0.5 1.0 1.5 2.0
Bp (T)
(Accelerator field proportional to poloidal field at 0.43 m lor three
gun conditions, consistent with line predicted by TRAC code.)
20-A- 1090-03.40A
IK=
F-II
°An Alternate Application of MPD Arc Sources:
Plasma "Tethers" for Tapping the Solar Wind EMF for Power > 10 MW
Plasma plumes generated by MPD arc sources can extend of order 1000 km across the solar wind
magnetic field. ]'he electric field, E = Uwind x B, gives a voltage drop along the plume, and
currents are induced as in the AMPTE artificial comet experiments.
The available power is:
P = 2 Mp Vp vA Mp = mass ejection rate Vp = plume velocity.
vA = Alfven velocity
An example:
Mp = 10 glsec, Vp = 60 km/sec, vA = 80 km/sec, P = 100 MW
The power could drive thrusters with a specific_npulse of about 3000 sec.
A lunar power station could extract large amounts of power since there is unlimited available
mass. The energy extracted is about 10 TM Joules/kG
®
u
_w
®
u
_'._c,,'_;c J'_r ,-,;,_ p/m,,.,<,.
!
&
F-12
Boo Solar wind rnagnet,c l,eld
Figure
/ m./-_,
_..., ._/--:_m.
SelI-sustalnlng ooa.xLal guns Serf.sustaining ancl
thn_ter oo_[lal gt.m$
Figure
F-13
T_- "?_.,_-aj_,,._ _, _: C_J_l,_-x,
F-14
1.8
1.6
1.4
1.2
1.0
0.0
0.6
.I
04 J
!
'#
O.2 L
#
0
tang
i i I l I I i I I ' i, '
,¢
0 = k ,(k'Z-,-)
! \ %.
%
_ Asymptote
Effect o "q%" "_,
Jpreadln 0 _.%
Effect ol -_'_'''_ _
-q, .
convective losses "" -%,,
I , I _ I I I I , I t I i I I I "_
0.2 0.4 0.6 O_ _ 1.2 1.4 1.6 1.8 2.0 2.2
k_/kl =
Figure 5
50-1-0491-0G: _ -a
F-15
10
Z
Zo
0.1
. _lng
%
c_onve_lve Io_ '_ %,
,%
%
%
%.
%
I I 1 t I I I I _.1
0.2 D.4 0.6 0.8 1.0 1.2 1A 1.0 1JI
kpl/kl I
2.O
Fiou)'e 6
Conclusion: LLNL has extensive expertise in physics and technology
relevant to MPD thruster development
Areas inwhich we could contribute include:
Modeling of atomic physics, plasma sudace interactions and 2D MHD llows
Results from ongoing high-power plasma accelerator experiments (RACE)
Plasma diagnostics
High pumping speed test stand for litetime validation studies (MFTF-B)
F-16


LLNL contributions to MPD thrusters for SEI

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