Author(s)
Chang, Chung-Jen
Title
Electrodynamic behavior of PMG-Delta
Publisher
Monterey, California. Naval Postgraduate School
Issue Date
1994-06
URL
http://hdl.handle.net/10945/30833
This document was downloaded on May 04, 2015 at 22:01:37
NAVAL POSTGRADUATE SCHOOL
Monterey, California
THESIS
ELECTRODYNAMIC BEHAVIOR
OF PMG-DELTA
by
Cbang, Chung-Jen
June 1994
Thesi s Advisor: Richard Christopher Olsen
Second Reader: Suntharalingam Gnanalingam
Approved for public releasej distribution is unlimit ed .
Tbesis
C3 '{ 135
DUDLEY KNOX LIBRARY
NAVAl POSTGRADUATE SCHOO!
MONTEREY CA 93943-5101
REPORT DOCUMENTATION PAGE
Master's Thes is
4. TITLE AND SUBTITLE
ELECTRODYNMtIC BF.HAVIOR OF I'MG-DELTA
6. AUTIIOHIS)
CHA",G, C HU !'lG-JE",
7. PERFORMlNG ORGANIZATiON NAME(S) AND AT)DRESS(ES)
H. PERFORMING ORGA:";IZA TlO :";
HEPORT NU.\1DI::R
Naval Postgraduate School
Monterey, CA 93943-5000
9. SPONSORINGlMO:";ITOHING AGENCY NAME(S) ANU AUDRESS(ES) 10. SPONSORING/MONITORING
AGENCY REPORT NlIMDEIt
I I. SUPPI.F.MENTARY NOTES
The vie ws expressed in this thesis are those of the author and <10 nOI
Departmcnt of Dd~nst octile U,S. Goven"nenl
r~necl
the official
14. SU HJfCT TERMS
JXl1i~y
ur position of thc
15 , NL'MBER
or PAGES
73
Organimliona) Lcam in!(. Lessons Learncd. After Action Rcports.lnfommtion Systems
17.
SECU~IT\'
CLASSIFTCATION OP REPORT
V nClal'si ric d
19. Sr.CI;RITY CtAssrrlCATION OPTHIS
ABSTRACT
20. LL\11TATlO :"; OF
ABSTRACT
Sl.mllllrlForm 298 (Re¥ . 1·89)
P""rnbe~h)'
ANSI S,d 239·l.
Approved for public release; distribution is unlimited.
ELECTRODYNAMIC BEHAVIOR
OF PMG-DELTA
by
j=hang ,
Chun~-Jen
Lieutenant Commander, Talwan, R. o. C . Navy
B. S., Chinese Nava l Academy, 1979
submitted in partial fu l fil l ment
of the requirements for the deqree of
MASTER OF SCIENCE IN ENGINEERING ACOUSTICS
from the
NAVAL POSTGRADUATE SCHOOL
June 1994
Author :
i/
changP '-<'hung-Jen
Approved by:
Richard Christopher Olsen, Thesis Advisor
.-----
sun~linga~ l ingam, Seco nd Reader
------
William Boniface Colson, Chairman
Department of Physics
ii
ABSTRACT
The PMG-De l ta experiment was launched on 26 June 1993 to
t ost
basic
te the r
electrodynamic
princ i ples.
The
500
m
co nducting t ether deployed from the second stage of a Deltarocket,
and provided -3 orbits of useful information.
The
t ether was equipped at both ends with xenon hollow cathod es.
With both c ilthodes operati ng ,
currents u p to 0 . 3 11 could be
dr i ven in either direction.
Plasma impedances outside the
tethor we re as
hund red ohms at peak
low as a
few
du-::-ing daytime/perigee (200 km).
current
Lar g e impedances (10 - 100 k Q)
occurred at n i ght/apogee (900 km), or when one cathode cycle d
off .
iii
TABLB OF COHD'l'S
IHRODUC'!rIO•.
I I •
..
BACKGIlOOllD .
A. THE ENVIRONMENT OF THE EXPERIMENT.
B. GEMINI
•.
C. TETHER SATELLITE SYSTEM.
THE HOLLOW CATHODE
E.
SEDS • •
III. THE PLASMA-MOTOR-GEWBnTOR EJ:PElllMEII'r .
IV.
.
OBSERVATIOII'.
12
A. DEPLOYMENT
12
B.
12
STANDARD MODES
1. Tether current depends on environment
C.
THE EFFECTS OF HO LLOW CATHODE.
D.
SYSTEM IMPEDANCE
13
15
19
1. Plasma i mpedance .
20
21
SUMMARY AlfD CORCLUSIORS
I.ITIAL DISTRIBUTIQII LIST.
62
iv
DUDLEY KNOX LIBRARY
NAVAl POSTGRADUATE SCHOOl
MONTEREY CA 93943-5101
LIS T OF TABLES
Table 1 .
THE PMG ON-ORBIT EVENT TIMELINE .
Table 2 .
HOLLOW CATHODE "ON " ,"OFF" TIMING
15
LIS'!' OF FIGURES
Figure
1.
Figure
2 . Gemini spacecraft tethered configuration.
Plasma density with altitude in the ionosphere.
23
24
Figure
3. TSS operation concept
25
Figure
4. TSS configuration in 'cargo bay.
Figure
5. Shuttle-tether-satellite sketch.
Figure
6. TSS around Earth's ionosphere as moving conductor
Figure
7. TSS-l, deployed satellite.
29
Figure
8 . Plasma-bridge neutralizer cathode construction.
30
Figure
26
27
28
9. Hollow Cathode Assembly configuration
31
Figure 10. SEDS arrangement inside Delta I I second stage
32
Figure 11. SEDS location on Delta II launch vehicle.
33
Figure 12 . Delta second stage with deployed tether
Figure 13. PMG
demonstration
of
electrodynamic
34
tether
35
principles.
Figure 14. Location of PMG package on Delta second stage
Fi gure
PMG mechanical layout .
.
37
Figure 16. NEP anode voltage with t iming
Figure 17. Al titude of Orbiter
39
Figure 18. Orbiter trac k diagram
40
Figure 19. PMG circuit diagram
41
Figure 20. Standard data frame sequence.
42
Figure 21. PMG-De l ta deployment phase.
Figure 22 . Data frame 80
44
Figure 23 . Data frame 4 .
45
vi
Figure 24. Data f rame 9.
Figure 25. Data frame 83
Figure 26. Data frame 85
48
Figure 7.7. Data frame 145.
Figure 28 . Pote ntial summary
50
Figure 7.9. Current sununary •
Figure 30. Current change with FEP/HCA working state
52
Figure 31. Current change with FEP/HCA working state
53
Figure 32. No current change with FEP/HCA working state.
54
r' igure 33. Potential change with !-lCA working condition
Figure 34. Potential change with HCA \olOrking condition
56
Figu re 35. Potentiill change with HCA working condition
Figure 36. Plasma
jmpedance
at
different
bias
voltage
at
dif fe rent
bjas
voltage
and load resistance
f'igur-e 37. Plasma
impedance
58
and load r e sistance.
Figure 38. Impedance wi t h current.
50
Eigure 39. Impedance with current.
61
v ii
Thanks to Dr. Jim McCoy principal investigator for PMG-Delta,
for
bringing the
project to
completion.
I
wish to
express my
thanks to my Thesis Advisor, Dr. Richard Christopher Olsen, for his
understanding, infinite patience, and guidance.
I would also l ike
to thank Dr. SUntharalingam Gnanalingam, who provided a lot of help
and enthusiasm when it was greatly needed.
least,
Last, but by no means
I would like to extend deep appreciation t o my family and
friends who gave their total support throughout the entire project.
vi ii
I.
IITRODUC'rIOR
The e lectrodynamic tether is, at its most basic level, a wire
moving through a
res u lt ing
physicists
magnetic
electric
since
field.
field,
Th e
c urrents,
tho days of
Oersted
relationship between the
and
in
forces
has
fascinated
1820. [ Ref.
1:
p.
636 J
Space tethe rs emerged as a concept in the early 1970's with the
work by Mario Grossi, and with encouragement of Hannes Alfven.
long wire in s pac e, anchored (or nat) at the ends with tiatellites,
is a stable system,
due to gravity grad.ient effocts. ( Ref.
2]
As
such, an electrodynar.1ic tether offers intriguing possibilities as
both a motor and generator.
r·or the propose of s tudy ing these phenomena, a joint venture
of the !Jni t ed States' Nat.i anal Aeronaut i cs and Space Admi nistration
(NASA)
and
I taly 's Agenzia
Spaziale
ItaUana
(ASI,
the
Italian
Space Agency) developed the Tethered Sate]lite System (TSS-1).
In July
1992,
the
shuttle deployed
a
heavily instrumented
satellite as a test of tethe r electrodynamics.
unfortunately, the
20 kI1 cable jammed at 570 feet (USA Today, Aug 5,1992).
Relatively
low voltages were induced (-40 V) and t he corresponding currents
were
1010.'.(15
rnA)
(AW&ST,
August
10,1992)
One
roason
for
low
current s in such a system js poor electrical contact with the local
plasma envj ronment.
The plasma notor generator exper iment, PMG-Delta, was designed
to s tudy this electrical connectivity problem.
Using Xenon based
ho l low cathodes also termed plasma contactors, [Ret. 3J
the 500-m
tether system was deployed from the second stage of a Delta-rocket.
The work which follows considers the electrodynamic behavior
of the system.
II.
A.
BACKGROUlID
THE EIIVIROIIMBIIT OF THE EXPERIMEB'T
The
upper layer of Earth's electrically neutral
atmosphere
wh ere the experiment took: place, is characterized by the presence
of
electrically charged
extends
from 85
ionosphere.
km to
gases,
or
plasma.
approximately
This
1,000
kIn,
region,
is
which
known as the
The boundaries of the ionosphere vary according to
solar activity.
In
sunlight,
gases
in the
ionized by the radiation from thc Sun.
remains charged unti l
atmosphere will
be
Once an atom is ionized, it
it meets an electron;
it then very likely
recombines with an electron to become n eutral again.
the density of ionized gas will be lower .
In darkness
Ionized particles will
drift duo to effects of the magnetic field and elec tric fields.
Above the i onosphere is the magnetosphere, which extends from
1,000 km to 60,000 km on the side toward the S un,
more than 300,000 km away from the Sun.
and trails out
The !<1agnetosphere is the
region surrounding Earth in which the geomagnetic field plays a
dominant role in the behavior of charged particles. [Ref.
4J
Figure 1 shows the variation in plasma density with altitude
in the ionosphere. LRof. 5 : P. 128J The big difference between day
and night is important in our experiment .
GEMINI
The
first tether in space experiments took place in September
and November of 1966.
Tho Gemini XI and XII spacecraft together
with the Atlas-Agena D spent stage performed these experiments.
Figure
shows
the
spacecraft/target-vehicle
simple
tethered
connection
of
configuration.
Gemini
In
Gemini
program, one mode of operation consisted of intentionally inducing
an
angular
ve l ocity
in
the
tethered
system
by
thrusting with the spacecraft propulsion system.
involved
gravity
Those
tethered,
drifting
flight
gradient on the motion of
two
modes
of
tethered
during which
the
vehicle
translational
T he other mode
the
system was
of
operation were
effect
of
interest.
completely
successful. [ Ref. 6 J
C.
TETHERED SATELLITE SYSTEM
The
next major tether experiment was TSS-1.
Sate l lite System has five major components:
the tether,
mounted,
and
the
satellite,
sc i ence
the carrie r s
instrument s .
The Tethered
the deployer system,
on which the system is
Figure
3
shows
the
configuration of the shutt le, with the dep l oyer extended.
rough
Figure
4 shows the shuttle bay prior to extension of the dep l oyer. (Ref. 7)
Figure
5 shows the 1200 pound
Italian satellite in an artist's
sketch. (Huntsvile Times, July 27,1992)
The phys i cs of the system is simple.
6,
the
orbital
motion
of
the
deployed
As illustrated in Figure
system
results
in
electrical field of the order of 200 Vjkm along the tether.
an
The
resulting potentia l difference between the end s of the tether wi_11
nomina l ly cause the far ends to float positive and negative, with
respect to the plasma at the ends of the tether.
Hence, charges of
the appropriate sign will flow to the orbiter and satellite, and a
net current will flow through the tether.
In order for a complete circuit to exist,
through the plasma.
current mus t
flow
It is difficult for the highly magnetized
plasma to conduct such currents,
and it is believed that closure
may occur via currents along magnetic field lines dow n into the Eregion where collisions allow currents to flow perpendicular to the
magnetic field.
In July 1992, TSS-l was launched OIl STS-46.
Everything worked
reasonably weU, until -175 m out, when the cable snagged.
7 shows the deployed satellite.
(USA Today, August 5,
Figure
1992)
The
relatively short deployment restricted the VXB induced potential
drop to
(A>~&ST,
-40 V,
and the resulting currents on]y reached -13 mAo
August 10 , 1992)
The
mission
successful
was
(dynamic)
successful,
control of the
however
satellite,
,in
demonstrating
alleviating many
fears about the mechanical behavior of the tethers.
A ret light is
planned for 1995 .
D.
THE HOLLOW CATHODE
One reason for relatively low currents i n the TSS - l mi s sion
may havD been r elatively high impedances at the satellite-plasma
boundaries.
One way to deal with this problem is to put plasma
sources on the satel) ites .
as hollow cathodes,
Gas d i sc harge plasma generators, such
can provide an electrical bridge to the
mon~
diffuse ionospheric plasma. [Ref 8J
'Plasma Contactors'.
Such devices have been termed
A major purpose of the PMG-Delta experiment
was to test this technology, as applied to a tether system.
Hollow Cathodes, in space applications, have their origins in
ion engine technology . [Ref 9, 10J
due to Rawlin and Pawlik(1968).
Figure 8 shows an early design,
The primary change since that time
has been the transition from rolled foil i nserts to porous tungsten
inserts, impregnated with barium carbonate (Ba C0 3 ) .
The Hollow cathode design used for PMG provides a supply of
Xenon
gas \ wi thin
approximatel y
cathode
and
a
hollow
1300°C.
A
electron
strong
corresponding
anode
emitter
voltage
plate
discharge to create a partially ionized gas.
cathode
gradient
heated
between
establishes
a
to
the
plasma
The free expansion of
this ionized gas plume from the Hollow Cathode Assembly (HCA) into
the surrounding ionosphere creates a
region of
increased plasma
conductivity extendi ng many meters into the ambient plasma.
The
HCA system co n figuration is illustrated in Figu re
E.
SSDS
Tn the Tethered Satellite System,
the deployer is the Small
Expendable-tether Deployer System (SEDS), whose design is due to
Joe Carroll.
This design flew once previous to PMG-De l ta,
non-conducting tether,
also
second stage on March 29,
again, on March 9,
1994 .
successful l y
dep loyed
from
a
as a
Delta
It has subsequently been flown
The
concept
retrievability,
of
SEDS
10w tension,
design
minimum braking,
simplicity,
and a wide swing.
The SEDS consi sts of four key components: the tether wrapped on a
aluminum core and located in a canister; the brake/cutter assembly;
the endmass
system.
(or payload);
Delta I I second stage.
Delta I I
and the
electronics control and data
Fi gure 10 shows each component of SEDS arrangement inside
Fi gure 11 illustrates the SEDS location on
launch vehicle.
Figure 12 shows the Delta second stage
with deployed tflther_lRef_ 11, 12 J
The primary objective of the PMG-Delta flight experiment was
to verify the ability of hollow cathode plasma sources to couple
electrical
currents
from
either
end
of
a
long
wire
to
the
ionospheric plasma in Low Earth 'Orbit (LEO).
The PMG f l ight hardware cons i sted of four major subsystems:
the Far End Package (FEP), Near End Package (NEP), electronics box,
and Plasma Diagnostics Package
( PDP).
Figure 13 shows the system
deployed, with the electrical dynamics of motor and generator modes
shown. The deployer is the SEDS design described in the previous
section.
T he mechanical layout for the PMG expe r iment is illustrated in
Figures
14 and 15
Note that the dimensions
are
of order -12
inches.
This assembly was carried aboard an Air Force Delta-II rocket
and launched on June 26, 1993 at 13:27 GMT.
After separation, the
PMG system was left in an elliptical orb i t
(207X922 km) at 25.7°
inclination.
Twenty six minutes later, the PMG system was powered
on by automatic command.
The FEP was deployed 400 seconds later
and subsequently stabilized above the NEP via an 18-AWG 500-meter
copper-wire tether.
Table 1, from the PMG mission report (Jost and Stanley,1994)
shows the tir.leline of important events.
listed
here,
the
NEP
hollow cathode
apparently from spot to plume mode
In additi on to the events
changed mode
(Figure 16).
at
0 1 :00:50,
This change wa s
anticipated, and is a result of the gradual drop in gas pressure in
the supply .
rMG on-omt
~v~nt
EVENT 10
1i .... 1....
P M GT(. ..,J
GMT (hII:mm:nJ
1)2700
,
End seeond Sliilgedeplelionbum
PMGpowefOl'O
Eleelfomeler c.ahbfiilllOn(S-4.ee)
'"
'"
FEPSlar1~qut!l>Ce
..'"
S cur..ent read (242 sec)
Be9'n FEPl1etherdeploymenl
'00
En<l COnMI/OUSCUfTenl read
High CUrTenl mode
(4~
see)
FirS! slan<l"d dal" I,ame (lSI sec)
n,ghl(spKecr,,~)
1170
Geographoc equarOf (..c)
21H
Day ...
Al>OIIee(8ISBkm)
M"lInetocequIIOfClOU(ISC)
HiqII (:U!1'ent mode (44 sec)
",.
High cUffent mode (44 sec)
Nighl ... daylspececr,lI)
HighCUftern mode (4. see)
Geogr"phicequalor aon (dec)
Perigee (194 km)
Geomagnetice""alOfCfOlsldesj
Day --+nighl(spaceCl,nj
Gf!'Ographtc equalof CfOSS (nc)
AP<>QH (866k m)
Magn ellc equator Cf05S (ucj
,,,.
3259
""
"
""
''''
15:17, 5-1
-~
15_23_56
,."
"
""
9313
16:28;53
""
""
"'"
1634:32
"
"
--~
16:001 : 19
N";rhl---< dar l",,,ceaan)
High currenl rnode (44.ee)
High currenl mode (44 se<:)
lnleJeeuome\e<d.!Ilar.ame
Eleclromele' calibr.'ion(33.ec)
Highcu"ernrnode(lhroughlOSj
GeOQl'.phicequalorao. s (d<&c)
M"gnelicaquiil1OfCfon(dec)
Day_nogMt(.p.ceCfan)
Geogflphic e(!UiiI1QfCfOSS (ascj
Miilg"",icaquatoraou(uoj
Lon or lel,mel..,.
""
10,761
The system was in a high current mode at this point, and no
useful current telemetry are available to determine effects due to
t he change in cathode mode.
Figure 17 shows the altitude of the vehicle,
and Figure 18
shows the orbital track. Not e that perigee was in the middle of the
day,
so the day-night effect reinforces the altitude effects on
local plasma density.
The
PMG
experiment
was
designed
potentials across through the tether,
voltage.
to
measure
as a
currents
and
function of tether
Figure 19 shows a simplified schematic of the system.
The load resistance could be set at 2.2 MQ to make tether voltage
measurements,
and at 0,
lOa,
200,
and 500Q in current mode.
The
electrometer switched between 10 0 pA and 1 A full-scale modes for
the corresponding measurements.
from +65, +30 ,
bias,
with diodes
directions.
The applied bias could be cycled
±O, -65, - 130 V.
A
set for
"shorted"
The ±O modes correspond to zero
positive
mode
was
current
flow
available,
in
but
the
signed
electrometer
meas urements in this mode were saturated, and are not shown.
The standard data frame sequence is illustrated in Figure 20.
Each voltage,
resistance sweep too k approximately 10 seconds. The
Bias voltages was varied at
10 second intervals,
resistance stepped at 2 second intervals.
2.2
MQ
produces
a
potential
measurement
measurements provide current at 500
resistance.
There
is
-160
Q
Q,
200 0,
resistance
circui try, besides the load resistance.
with the load
The 2 second dwell at
(LHS) ;
100
Q
subsequent
and a '1 load
in the tether and PMG
Note that no current flows at -0 V bias, due to thp. diodes in
the circuit .
Curves are 1 abeled with the time tag obtained at the
end
9
of
each
to
10
second
sequence . {Timing
varies
slightly
according to the measurements, because of an antiquated CPU i n the
control electronics).
In addition to the sequence of events illustrated here, there
was sequence of the FEP hollow cathode every 10 seconds .
Discharge
powRr for the FEP was shut off for 10 seconds in every 90 seconds .
Deta .i ls of this effect wil l bp. discussed below.
IV.
OBSBRVATIC*S
The great majority of the data collected by PMG are in the
standard mode of bias voltage/load resistance sequences already
illustrated.
These data are examined i n more detail below.
First,
however, the deployment sequence is shown.
A.
DBPLODIBJI'l'
The hollow cathodes were switched on prior to deployment.
The
assembly was released, and reached its SOD-meter extension in a few
seconds.
This process was conducted with the + 6SV bias applied,
and with zero load resista nce.
Figure
21
shows
the
deployment
data.
The
current
drops
sharply once the FEP separates from the Delta second stage.
T he
initial sequence of variations is not clearly understood, but it is
apparent that the system quickly settles down to -0.075 A, with a
modulation
of
-S
to
10
rnA.
The
large
drops
at
00:07:30
00:09:10 are due to the cycling of the FEP hollow cathode.
current effectively drops to zero.
explored below.
For now,
and
The
This behavior wil l be further
it should be noted that the system is
still in day light and at a relative l y low altitude.
B.
STA)f])ARD MODES
Tbe data from the basic mode were examined [or the 2\ hour
period during which such sequences were run .
Subsequent to this,
the "high current" mode was used, where the electrometer curr ent
12
could not be measured.
at perigee,
These
Figure 22 shows the data at the 01:32 mark,
ju st af te r crossing the magnetic equator.
measurements
show
observed during the mission.
measurement
of
-125
currents
i mplying
V,
near
the
peak:
magnitude
The i65 V bias data show a potential
a
tether
voltage
of
-60
S ubsequent bias steps show appropriate drops in potential.
V.
The +OV
and -.-30 V bias show a variation due to the -38 time constant of the
bias circuit; the potential has not quite stabilized at the end of
the potential measurement at those levels.
Variation
around
changing environments,
the
behaviors
shown
here
were
driven
by
and the cycling of the FEP hollow cat.hode
power.
1.
Tether current depends on the environment
The current through the tether depended strongly on the
environment. Figure 23 shows one of first sequences.
with
the
data
shown
jn
Figure
22,
positive b ias voltage are very low.
below
the
deploynent.
values
The
relatively high,
observed
current.
-0.1 A.
fj ve
observed
the
currents
I n fa ct.,
mjnutes
for
By contrast
observed
they have
earljer
-130
V
during
bias
is
for
fallen
the
stil l
Figure 24 is a plot. of data taken five
minutes later (data frame 9)
from 0:17:55 to 0:18:52.
It is an
example that indicates the current was at as low as 0.02 A (the
electrometer resolutjon) for aJl bias Voltages except -130 V.
of t.he night-time data looked l ike this.
13
folost
The peak currents were observed in daylight in the next orbit.
Figure 25 and 26 show the data from frames 83 and 85.
shows the
most
-130 V bias.
Figure 25
negative current measurement, - - 0.3 A, taken at
Figure 26 shows the largest positive current,-0.18 A,
taken at +65 V bias. The currents again dropped as the tether was
eclipsed .
In the final orbit, currents were just rising above zero
as the sequencing ended.
Figure 27 shows the data from the last sequence, data frame
There is a modest positive current of -0.05 A at +65 V bias,
and a similar magnitude current observed at -130 V bias.
in the current observed at +65 V bias, 0
Q
The drop
load resistance occurs
when the FEP hollow cathode shuts off, as addressed below.
The complete data set is summarized in Figures 28 and 29.
The
potential measurement from the 6 bias levels are shown in Figure
28.
The top half of the figure shows,
taken at +65,+3 0 and +0 bias.
taken at -0, -65, and - 130 V.
data
are
due
to
the
slow
circuit, as shown above.
i n descending order, data
The bottom panel
shows the data
The wide spread in the +3 0 and +OV
decay
of
the
capacitor
in
the
bias
The small gap at +1 00V is due to a bit
error in the electrometer.
The non-zero values for the - 0 V bias data are something of a
mystery.
The outlying data values
are due to the
FEP cathode
cycle, as discussed below.
Figure 29 shows the currents measured at +65V bias, and -130
V bias,
negative
for zero load resistance.
direction
are
uniformly
14
Note that the currents in the
larger
in
magnitude
than
the
positive currents, even though th e net potentia) in that direct io n
i s less than the net pote n tial for t 65V bias.
Th e downward spikes
i n the -+65 V trace are again due t o the FEP cyc l ing.
C.
THE EFFECTS OF HOLLOW CA'l'HODE
/If; noted severa]
times above, t he operating condition of t he
FEP hollow cathode h as dramati c effects on the system.
be
no tnd
that when the
cont i nu es to flow .
FEP cathode d i scharge
gas
T he FEP cathode was programmed t o cycle off for
10 snconds in every 90 seconds.
Table 2.
It should
is shut off,
The "ON" ,"OFF" t j ming is shown i n
The data were surveyed for evidence of the t ransitions,
since no telemetry iF; availab le afte r deployment.
In Table 2, t he
mark "X" means that there i s no c Inar evidn nc e of thn HCA wa s u nder
"ON" or "OFF" condition .
Ta ble 2 ' Hollow cat hode "ON", "OFF" t im j ng
"ON"
PERIOD
0 : 12 : 41
0: 12: 5 1
0 : 1 /.:01
0 : 14: 11
90"
0: 15 : 39
0 : 15: 49
88"
0 : 17: 13
0: 17: 23
84"
0 : 18: 5 7
91 "
0: 21 : 58
0 : 22 : 08
0 : 25:08
0 : 25 : 17
0 : 26 : 5 0
0:32:58
0: 33: 08
0:36:05
0:37 : 50
0:40:47
0:40:57
0 : 43: 54
0: 44: 04
0 :45:3 8
94"
0 :51:4 3
0:54:58
0: 56: 23
1: 02: 46
1 :0 5 :4 3
1 :05: 53
1: 14: 57
1: 15 :07
1 : 18 :0 2
1:18: 11
1: 21: 06
1: 22: 36
1 : 22: 46
1:24: 11
1: 24: 21
95"
1 :2 5 :40
1; 25: 50
89"
1: 27: 12
1: 2 7: 22
92"
1:28:41
1: 30; 12
1 : 30: 2 2
91"
1: 31: 44
1 : 31: 54
92"
16
1 : 33: 14
1 : 33 : 24
90"
1 : 34 : 41-
1 : 34 : 54
90"
1: 36: 14
1 : 36 : 24
90 "
1:37 : 44
1: 37 : 54
90 "
1: 39: 15
1; 19: 25
91 "
1 : 40 : 44
1 : 40 : :'4
89"
1: 42: 13
1 : 42: 23
89"
1 : 43: 44
1 : 43: 54
91"
1 : 45: 13
1 : 45: 23
89"
1: 48 : 12
1 : 48 : 22
1 : .':>1 : 13
1 : 51 ; 23
1 : .':>4 13
1 : 54:23
1 ; 57
1 : 57: 20
2: 00 11
2: 00: 21
2:03:11
2: 03 : 21
2 : 06: 11
2: 06 : 21
2 : 07: 39
2 : 07:49
88 "
2 : 09: 09
2 : 09: 19
90 "
2 : 12 : 07
2 : 13: 47
2 : 15 :06
2 : Hi:45
2:18:07
2: 19: 45
2:22:45
2: 25: 35
2:25:45
2: 28: 34
II
II
II
2:28:44
2: 36: 04
2:36:13
2:39:04
2: 39: 13
The effects are studied by comparison of adjacent data frames.
Figure 30 shows data from an "OFF" cycle at 1: 25: 39.
The cathode
shuts off while the bias is set at +65V, and the load resistance at
100 ohms.
The current drops from 0.12 A abruptly to 0.03 A, with
a further slow decrease to 0.02 A.
Data from adjacent data frames
are shown to demonstrate that environmental changes are not the
cause.
These measurements occur in the time period of peak tether
current, and presumably the peak ambient electron density.
Figure
31
shows
a
second
illustration,
in
e nvironment, but with a change of the opposite phase.
a
similar
Note that
there is again a fairly l arge initi al change, with a slower (one to
two second time constant) approach to the full val ue.
18
The above two cases are for positive bias (generator mode). In
the opposite polarity, almost no change is found.
Figure 32 shows
the data for an FEP off cycle at 01 : 39: 15, and i ndicates a lack of
variation at -130 V bias.
The change in plasma impedance indicated by these data affects
the potential measurements, as well.
Figure 33 shows the contras t
HCA
was
all,
the
measured
for HCA "ON" VB "OFF". W'ben the
potential
across
the
?.2
MQ
load
resistance was approximately 20 volts higher than when HCA was off.
The system is now more obvious ly acting like a
The
potential
drop
across
the
plasma
is
voltage divider.
-15%
of
the
total,
indicating -300 KQ impedance in the plasma, when hollow cathode is
off.
Figures
Figure
34
34 and
is
35
nearly
are other examples.
identical,
illustrated is not coincidental.
bias are shown.
gradual
slope
The
shows
illustration in
that
the
effect
In Figure 35 data taken at +0 V
We can see that at
sharply at the end.
The
and
1:',8:27. the potential
rises
This is due to the hollow cathode turni.ng on.
is
again
due
to
the
bias
circuitry
slowly
decaying. Shifting the curve trace horizontally indicates a -15 to
20 V drop jn potential with the cathode off.
Similar comparisons
at -130 V showed no change.
SYSTEM IMPEDAlfCE
System impedance inc lud es load resistance, tether resistance
and the resistance of the plasma,
19
In this case, we know the tether
system resistance (equal 160
Q)
and the load resistance.
What we
want to know is how the system impedance is influenced by plasma.
1.
Plasma impedance
The impedance of the system can be estimated by dividing
the
measured
voltage
by
the
measured
resistances can be subtracted off,
primarily to plasma effects.
the
current.
The
known
remainder should be due
Figure 36 shows data from frame 80
with the inferred plasma impedance at different bias voltage and
load resistance settings.
We can see that the minus bias voltage
always gives the lower plasma impedance.
has negative resistance.
It seems that the plasma
The resistance declines as the current
increases. Data from data frame 91 are show in Figure 37.
HCA is off
during
the
+65
higher impedance estimates.
V measurements giving
Here the
substantial l y
The impedance is not as high as the
- 300 KQ obtained above at low current (2.2 MQ),
however.
It is
apparent that the impedance depends strongly on the bias voltage
and load resistance, implying a dependence on current.
The data are show as a plot of impedance vs current in Figure
38 (from data frame 80). The larger magnitude currents give lower
impedance, and negative currents show lower impedance than positive
current
of
the
environment,
OO:lB:05.
same
also.
magnitude.
Figure
39
This
shows
effect
data
depends
taken
on
earlier,
the
at
'the impedance never drops below 1 KQ, and exceeds 10 KQ.
It is a strong evidence that the system impedance depends on the
plasma density.
20
During
the
PMG
expedment,
the
flight
telemetry
system
transmitted 146 frames of electrometer current measurements.
Each
frame consisted of all combinations of 6 bias voltages and 5 load
resistances
to
characterize
the
electrical
connection
to
the
mode
is
surrounding LEO pI asma.
Reviewing, the following facts were observed.
1. The
highest
current
measured
Generator
approximately O.lB A.
2. ThR
highest
current
measured
in
Motor
mode
is
approximately 0.30 A.
3. The
higheClt
induced
potential
in
Generator
mode
is
current
in
approximate l y 120 V.
4 . The
FEP-HCA
off
Generator mode.
state
gives
almo"t
zero
It has no effect in motor mode.
S, Almost no current is observed at night .
6.
is
not
effective
for
generator or motor in night.
tether
system
be
used
as
The ionosphere will not supply
enough electrons for the power .
7. According
to
working state.
the
experiment,
the
currents
depend
The HCA effectively decreases the
between plasma and the satellite.
21
on
HCA
impedance
The current may not be proportional to the induced potential.
The limitation seems to be how many e l ectrons can be supplied by
the ionosphere.
In this experiment, the tether only deployed 500 meter.
It is
not known how a longer tether wil l affect the system efficiency.
will expect further experiment.
ELECTRONS/m)
figure 1; Plasm3 density with altitude in the ionosphere
23
Figure 2: Gemini spacecraft tethered configuratio n
24
''', r "l HHTIIOO"''''''(I ~'\\I(l, _In~,",~
OOD,
,,._" " '''1" O'Q" ""'(['
1M "~, II"" , ~) OORrr
¥~~';~"J~; ~ I ~;~O~~~Hr~~~:,
CI'rVI"'
O\J 'W'"O USI"G
'(UAS(SAl!lU 1[ NlO ("""OlV!'w• • o
' ''J[(lO' ' UII " G '(I"( "(( t ..,10'
(WII" Iwn 1.\ 'IOU '
lO'~ 0[010""(/"
\1{tP\ AT 10 tM
.'<0
1\ .~ ) ' (/)III ' n
""O<J~",H' 9 1 '''' ''I
\AI(llll(((l"·OlttOOl' . \IAlIO"
In "1lU'S
Figure 3 : TSS operatio n concept
25
Figure 4:
TSS configurati o n in cargo bay
26
Astron aut s will reel oulan l ,t40-po und spherical sat ellite 12.4
miles above Ihe shu ille on a lether no bi gger than a boot lace.
Fi gure 5 : Shuttle- tethe r-sate ll ite sketch
27
Figure 6: TSS around Earth's ionosphere as moving
conductor
28
RfLEASe ; A telheredsalelble moves away trom its l;hullle cr;tdlo;
Tuesday_ Atlantis was CNer the Pacific jLlst oH ChIMl"S coast
Figure 7: '1'SS-l, deployed satellite
11
O.45cm
L
JL
""lio,
]j'''-o.05cm
/
L.N eu trillil~r
I
... ra heat5hield
keepereleclrode
O. 32 cm
o. d,Ta
Figure 6 : Plasma- bridge neutra lize r cathode
30
Figure 9: Hollow Cathode Assembly configuration
31
Figure 1 0 : SEDS arrangement inside Del t a I I se c ond stage
32
ntIR[).STA"GE
MOTOR S.EPAllATiON
ct..AMPASSEMBLY
SECOND STAGE
Tl<RUST
AUGMENTATION
SOLIDS
Figure 11 : SEDS location on Delt a II launch vehi cle
33
Figure 12: Del ta second stage with deployed tether
34
:;"~:'O'~
"7/ / /
'H · "oSTr"'OfO.,
l'igt.:rc ",3:
d emonst ration
pri acipJ'-'5
P~G
e lectrodynanic tetr;er
~
----'\~
g
~
o
!
~
~ ---
Figure 14 : Loca1:ion of PMG package on Delta second stage
36
Figure 15 ; PMG mechanica l
layout
37
Pfi G DellO
"0
. -~,::-::-c:~T-l
1~l l
"". _ _ _
c
z
_
_
___ ---'----I
3 00
W:: T (H H.MM)
16:
J
~J
'--~--~-
F i g ur e
~
NEP anode voltage wi th timir.g
?i~\lre
: 7;
Altitude o f
orb i ~er
39
792S/GPS SPACECRAFT M1551 ON
rSTflR ,OR TIM SIIE: iOY- 2. 00 Ot9
SECONOAIlY f'AvtO,o,D . PMG
LONGITUO(-DEG
F igure 18 : orbiter track diagram
40
I
- t>: ,:
J
jr_d"~,i
<
:[1 11,
'
F~l
i
~C[:l
dt.
~-
-II
~I f---
~H
Figure 19:
PMG circuit dlagraro
0.3
- 13'J V
~
20 0
0. 2
---·~~O. l
J
Figure 20: Standard data frame sequence
42
;:O hO S E-'
=
;-65 V
Lo;:]d f'es isto rl ce =
Figure 21 : PMG -D elta deploymen t
phase
43
I
Figure 22: Data frame 80
44
1----,,-----,Pif.l21 3:~; I ~a + 65 V
I
0,3
200
r_
o,
ur=~ ~'~---
3:
00
c
(:
o,
- 200
-0 .2
2 Mil I
500 Ii I 200 II
1:]0 Il
I
,0
l ime (s)
Dyo r ro -ne
Figure 23 : Data frame 4
45
4
2CO
Figure 24: Data frame 9
200
"l=
= Rl + 1600
~~
10
33
Do ta
Figure 25 : Data f rame 83
47
0.3
- ',30 V
:
'~~c=~ ~
:: :
_200[~> ~~J<:
R'ot"
R, '"
"=
2 MO
RL + 16 00
500 0
I
200 0
I
10 0 0
-OJ
0 0
~
,0
lime (s )
J oto Fr ame
Figu re 26 : Data fr ame 85
85
P'v1G - ~ el:o
20 0
~L =
2 \10
I
Data f rame 145
49
-so l
r
l
100 1 ~~~~~~~ , .1 ~~
0 _5
1.0
1.5
2 .0
2 .5
Tim e (hours)
Figure 2B : Pote ntia l sUllUlIary
50
J . 2°1~
0 10 -
=
~ V~"5 , "J
-040 ~
CO
'"
C,~
1.0
Ti 'T1~
'~ '2' 0' ~~
1 5
(ho cl rs)
Figure 29: Current summary
51
PMG-Delta
FEP off
150
_1:25:42
FEPon _ _ l:26:45
FE~on
_ _ l :24:J9
+65 V
0.1 4
+ 65 V
+65 V
0.12
,
2:
0.10
100
3:
0 .08
J
0.06
50
0.04
lO.02
R,o,o l = R, + 1600
R, =
0
2 "0
5000
I
2000
1000
00
lo.oo
'0
-ime (5)
Figure 30 : Current change with FEPjHCA work.ing state
52
1
-, ____,
PM~G~,_D
~e~ltrO----,_--_,
_
1:43:57
+ 65 V
, 50
2:
100
50
0 .04
rim e
f'igure 31: Current change with FEP/HCA working state
PMG - De lto
FEPci!
- 50
_ i :39:2!·
- 1 30V
FF o o n _ _ 1: 40 :30
-13 0 V
rEP o n _ _ 1:38 : 19
- 130 V
-,o rr
20 _' ,0·
~
~
"" 1
0.00
-0 ,05
-0. 10
~
- 200
- 250
300
= "'l +l GOO
l~'"
-"
2-,M",
". . L =-'0,--",",,,0-,0'--L
' -"'000,,--,,
0 ..L-'O,-,0o'...J - O. JO
Time (s)
'0
Figure 32 : No current change wi th FE~/HCA working state
180
~ 160
i
~
+65 V
FEP 0"
_
1:17:12
FEP o ff
_
1:18:16
+65 V
1: 19 :21
+65 V
FEP 0'1
<XlIJlIIIV
.-:. .:r:.:••l:"';~
140
120
Time (s)
Figure 33 : Potential change wit.h HCA working condition
55
2:
14 C
50 -
60L
t ____
~__~____
_ L_ _ _ _
~
_ __ _
10
Time (s )
Figure 34: Potential change with HCA working condition
56
PMG -D elta
FEP on
50
FEF o f f
FEP o n
2:
"
o
-
1 :47:27
_=
+0 V
48 :30
+0 V
1:49:30
+0 V
-
100
J,--.
--1' -
J , ..,
\0
Tim e (5)
Figure 35: Potential change with HCA work ing cond iti on
PM G- Oelto 1:32 :0 5
f
~
to 1:32 :56
r-----------~
~
-' oeo ["" "'. .,:.:_'.~'-'V
~ '-
_ _ _ _ _ _ ==~
"4
------.-__ 1
lo:~~~E'"'";~O~O~~~-l
500
200
100
Load Resis tance
Oo to Fro me
80
Figure 36: Plasma impedance at different bias v ol tage
ond load re sis tonce
56
F~v1 G-De l t o
1 >,,3:57
~~c r
OOOO ~
r-_··
-rr-i
to 1:4 4: 48
1
dD
_____
' OOD~==:=[
Figure 37: Plasma impedance at diffe rent bias voltage
and load resistance
59
PMG - Delio 1 :32:05
~
··
~ ,
l
t o 1 :32:56
l
1
10000
1
t
l JO~~~~~~~~~hL~~hL~=~~~
- 0. 30
-::120
[J, 10
- (JiQ
C~rr""nt
D'l\a
Figure 38 : Impedance with current
60
0.20
0 30
PMG - Oel t o 0: i 8:05
to 0 ' 852
' '' I '
' 00:: 8
)
~
'J
j
1
}
t
0
;0
j
- 0.30
- 0.20
- 0. 10
010
Figure 39: Impedance with current
61
0.20
0.30
LIST OF REFERENCES
1.
David Halliday, Robert Res n ick, Jearl walker, "Fundamentals of
Physics ", 4th ed, John wiley & Sons,lnc.1993.
I. Bekey I "Tether Propulsion" I Was hington, D. C. i P. A. Penza, Jet
Propulsion Laborat ory, Pasadena, California, 1986 .
3.
D. E . Parks., and I. Katz., " Theory o f Plasma Contactors for
Electrodynamic Tethered Satellite Systems"
S-CUREO,
La
Jolla, California, 1987 .
Otto Heinz. and R. C. Olsen., "Introduction to the Space
Environment" Naval Postgraduate School, Monterey, California,
1993 .
A. D. Richmond, " The Ionosphere ", " In the Solar wind and the
Earth" edited by S .
l-Akasofu,
and Y.
Kamide,.
Terra
Scientific Co, Tokyo, 1987 .
I. Bekey, "Historical Evolution o f Tethers in Space"
Headquarters, Washington, D.C. 1986.
NASA
7.
T . D. Megna,. "Tethered Sat ellite System Capabilities". Marti n
Marietta Denver Aerospace, Denver, Co. 1986.
8.
E. Hastings, " Theory of Plasma Contact ors Used
Ionosphere",
MIT. Cambridge , Massachusetts, 1987.
9.
V. K. Rawlin, and E. V . Pawlik, irA Mercury Plasma-Bridge
Neutralizer" NASA Lewis Research Center, Cleveland, Ohio, 1968 .
10.
J . W. Ward, and H. J. King,."Mecury Hollow Cathode plasma
Bridge Neutralizers", Hughes Research Laboratories, Mal ibu ,
California, 1968 .
11.
James K. Harrison, Charles C. Rupp, (NASA) Joseph A. Carroll,
Charles M.
Alexander,
Eric
R.
Pulliam, (Energy Science
Laboratories, Inc.) "Small Expendable-tether Deployer System
(SEDS) development status", 1989.
12.
J.
M. Garvey, D. R. Marin,
"Delta II secondary payload
oppo r tunities for tether demonstration experiments ". McDonnell
Douglas Space System Company, Huntington Beach, Califori an,
1989 .
62
in
the
lWI'rIAL DIS'rRIBUTIoa' LIST
1.
Defense Technical Information Center
Cameron Station
Alexandria, VA 22304-6165
2.
Dudley Knox Library
Code 52
Naval Postgraduate School
Monterey, CA 93943 - 510 1
3.
Chairman Dr. Wil l iam Boniface Colson
Code PH
Department of Physics
Naval Postgraduate School
Monterey I
4.
CA 93943
Professor Richard Christopher Olsen
Code PH/OS
Department of Physics
Naval Postgraduate School
Monterey,
CA 93943
LCDR Chang,
chung-Jen
NO . 173-S, Hwa- Ning road,
Kaohsiung,
Taiwan, R.O . C.
6.
Nava l Academy Library
P.O. Box 90175
Tsoying, Kaohsiung,
Taiwan, R. O.C .
Jerry Jost
System Planning CORP
18100 Upper Bay Road,
HOllston, TX 77058
8.
Suite 208
Jim MCCoy
NASA/ JSCj SN3
Houston,
TX 77058
9.
Nobie Stone
NASAjMSFC
Huntsvil l e, Alabama 35812
10 .
Jim Stanley
NASAjJSC
Houston, TX 77508
63
11.
Dr. Mario Grossi
SAO Center for Astrophysics
60 Garden
Cambridge, MA 02138
12 .
Joe Carroll
Tether Applications
1813 Gotham St
Chula vista, CA 91913
13.
Roy Torbert
Space Science Center - lEDS
Univ . of New Hampshire
Purham,
14.
NH 03824
Dan Hastings
Dept, of Aeronautics and Astronautics
MI T
cambridge, MA 02 139
15 .
I ra Katz
S-C ubedjMaxwell Laboratories
P.O . Box 1620
La Jolla, CA 92038.
Myron Mandel l
S - CubedjMaxwell Laboratories
P.O. Box 1620
La Jolla, CA 92038.
Victoria Davis
S-CubedjMaxwe ll Laboratories
P.O . Box 1620
La Jolla, CA 92038
18 .
J.R. Lilley
S-CubedjMaxwell Laboratories
P . O . Box 1620
La Joll a. CA 92038
19.
Dale Ferg us on
NASA/Lewis Research Center
21000 Brookpark Rd
Cleveland, Ohio 44135
Carolyn Purvis
NASAl Lewis Research Center
21000 Brookpark Rd
Cleveland, Ohio 4413 5
64
DUDLEY KNOX LIBRARY
NAVAL POSTGRADUATE SCHOOl
MONTEREY CA 93943-5101
/
11111
1111I'~illlll!ill!111
32768000195648