than
experienced
during
test.
This
platform temperature
is
not
actively
controlled,
and
can
drift
significantly
–
perhaps
leading
to
a
low
enough
temperature
to
condense
NH,
at
the
pressure
in
the
propellant
line:
To
further
support
this
possibility,
there
were
some
variations
from
the
normal
procedure
on
the
last
firing
( F-8 )
and no
liquid
ingestion
was
observed.
For
that
encase.
the
PFS
heaters
were
turned
on
many
hours
before
the
actual
firing
attempt
as
a
result
of
waiting
for
the battery
reconditioning
to
complete.
This
may
suggest
the
cold
spot
in
the
propellant
line
had
enough
time
to
heat
up and
vaporize
the
condensed
NH,.
In
summary.
the
liquid
ingestion
proved
to
be an
irritation.
but
did
not
seriously
detract
from
the
arcjet
operation.
If
the
ESEX
mission
had
continued,
a
heater
configuration
that
alleviated
this
problem
would
almost
surely
have
been
determined.
Other
than
this
issue,
the
PFS
performed
within
specification
and,
in
general,
operated
exceptionally
well,
The
flow
rate
control
generally
operated
to
within
kO.3
mg/sec
at
steady-state
conditions
–
an
order
of
magnitude
better
than
the
design
requirement
of
+5
mg/sec. If
this
system evolved
into
an
operational
flight
design,
some
heater
world power
applied
to
the
section
of
the
propellant
line
in
question
(or
more
direct
thermal
control
of
that
section)
could
almost
assuredly
resolve
the
liquid
ingestion
issue
entirely
–
especially
in
light
of
the
results
from
the
stopping point
firing.
Conclusions The
ESEX
flight
demonstrated
high
power
electric
propulsion
is
compatible
with
generic
satellite
cjperotions.
Although
further
analyses
are
in-work,
all
of
the
data
investigated
to
date
indicate
the
thruster
and
the
high
power
components
have
no
significant,
deleterious
effect
on
any
satellite
activities.
Summarv ESEX
is
the
culmination
of
over
ten
years
of
effort
to
\-alidate
high
power
electric
propulsion
on-orbit
and
verify
its
compatibility
with
standard
USAF
satellites.
There
were
a
total
of
eight
firings
conducted
over
the
path
of
the
60-day
mission,
all
of
them
over
26
kW,
degree fahrenheit
’
or
;1
total
duration
of
2023
seconds.
There
were
two
anomalies
associated
with
the
flight
operations
–
a
liquid
ingestion
problem
that
had
only
a
minor
affect
on
the
mission.
and a
battery
failure
that
precluded
any
far
firings.
Approximately
76%
of
the
ESEX
mission
success
was
attained,
with
the
biggest
deficiencies
resulting
from
the
lack
of
GPS
data,
and
the
optical
signature
characterization.
All
of
the demonstration
aspects
of
the
experiment
were
completed,
and
all
of
this
hardware
–
the
arcjet,
PCU,
and
PFS
–
operated
very
well,
and
within
their
specifications.
All
of
the
data
analyzed
to
date
indicate
the
thruster
operated
nominally,
and
operated
completely
independently
of
the
normal
operations
of
the
host
spacecraft
(ARGOS).
Acknowledments The
authors
would
like
to
extend
their
gratitude
to
the
entire
support
team
at
the
USAF
Research
Laboratory
including
Shaughn
Tracy,
Krystin
Barker,
and
Robin
Lowder.
We
also
extend
our
thanks
to
Mary
Kriebel,
Don
Baxter,
Bob
Tobias,
David
Lee,
and
David
Huang
of
TRW
for
their
technical
expertise
on
the
ESEX
flight
hardware ;
and
to
Andy
Hoskins,
Bob
Kay,
and
Joe
Cassady
of
the
Primex
Aerospace
Company
for
their
technical
insight
into
the
arcjet,
PFS,
and
PCU.
We
would
also
like
to
extend
our
sincere
gratitude
to
the
ARGOS
program
office
and
the
entire
flight
operations
team
at
Kirtland
AFB,
NM,
as
well
as
the
staff
at
MSSS
and
CPCA
for
their
technical
expertise
and
insight
into
their
facilities
which
allowed
ESEX
to
acquire
such
a
broad range
of
data.
References : 1.
Kriebel,
M.
M.
and
Stevens,
N.
J.,
“
30-kW
Class
Arcjet
Advanced
Technology
Transition
Demonstration
(ATTD)
Flight
Experiment
diagnostic
Package,
”
AIAA
Paper
92-356
1,
July
1992. 2.
Sutton,
A.
M.,
Bromaghim.
D.
R.,
and
Johnson,
L. K.,
“
Electric
Propulsion
Space
Experiment
(ESEX)
Flight
Qualification
and
Operations,
”
AIAA
Paper
95-2503,
July.
1995.
Also
presented
as
a
JANNAF
Paper,
December,
1995.
3.
LeDuc,
J.
R.,
et.
al.,
“
Performance,
Contamination,
electromagnetic,
and
Optical
Flight
Measurement
Development
for
the
Electric
Propulsion
Space
experiment,
”
AIAA
Paper
96-2727,
July,
1996.
4.
Turner,
B.
J.
and
Agardy,
F.
J.,
“
The
Advanced
Research
and
Global
Observation
Satellite
( ARGOS )
Program,
”
AIAA
Paper
94-4580,
September
1994.
5.
Agardy,
F.
J.
and
Cleave,
R.
R..
“
A
Strategy
for
Maximizing
the
Scientific
Return
Using
a
Multi-
phased
Mission
Design
for
ARGOS,
”
AAS
93-594,
August
1993.
12 ( speed of light ) 1999 American Institute of Aeronautics & Astronautics