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ION AUXILIARY PROPULSION
SYSTEM (IAPS)
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The Ion Auxiliary
Propulsion System project and other
preflight technology work took place in the
1974 to 1983 timeframe. Flight test
objectives were to verify in space the
thrust duration, cycling, and dual thruster
operations required for stationkeeping, drag
makeup, station change, and attitude
control. This implied demonstration of
overall thrusting times of 7,000 hours and
2500 on/off cycles. The 8 cm diameter,
mercury ion engine input power was 0.13 kW,
and the thrust was 5.1 mN at a specific
impulse of 2500 s. The masses of the flight
thruster-gimbal-beamshield unit, the PPU,
and the digital controller were 3.77 kg,
6.85 kg, and 4.31 kg, respectively.63 The
system stored 8.63 kg of mercury, and the
propellant storage and feed system weighed
1.56 kg. The IAPS successfully completed all
flight qualification tests and was installed
on an Air Force technology satellite. The
flight of the Teal Ruby spacecraft was
canceled by the Air Force due to lack of
funding.
During the course of the technology and
preflight programs there were a number of
endurance tests performed. A laboratory-type
8-cm engine was tested for 15,040 hours and
460 cycles at the 0.14 kW level. An
engineering model IAPS engine and PPU were
successfully tested for 9,489 hours and 652
cycles. The thruster and PPU were located in
the same vacuum chamber during this test. A
third endurance test was conducted using
another engineering model thruster and PPU.
This hardware was operated at full-thrust
for 7112 hours and had 2571 restarts. No
major changes in thruster performance, and
no life-limiting degradation effects were
observed in this test.
The preceding was an excerpt from:
Sovey, J. S., Rawlin, V. K., and Patterson,
M. J.: "Ion Propulsion Development
Projects in U. S.: Space Electric Rocket
Test 1 to Deep Space 1." Journal of
Propulsion and Power, Vol. 17, No. 3,
May-June 2001, pp. 517-526.
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