http://www.isas.ac.jp/e/new/release/2002/12_04.html
Microwave ion engine prototype model achieved 18000 hrs of autonomous
endurance running!
ISAS
January 24, 2003
The spacecraft for asteroid sample return mission, MUSES-C, scheduled for
launch in May 2003, will have an ISAS-developed microwave ion engine
onboard for interplanetary navigation. The prototype model of this engine
has achieved 18000 hours of autonomous endurance running. The ion engine
that started the endurance test on March 30, 2000 to verify its performance
for the mission requirement of 18000 hours has continued autonomous running
over approx. 2 and a half years. It successfully achieved the original goal
of 18000 hours at 2:00AM on October 25, 2002, and still keeps running at
present. The engine used for the endurance test is a prototype model of
MUSES-C and has been produced in complete accordance with the design,
material and manufacturing of the flight model.
[Image]
Figure: Cumulative running hours and screen current over calendar time
The figure shows the cumulative time (graduations on the left) from the
start of the test up to the achieving point of 18000 hours and the screen
current corresponding to thrust (graduations on the right) over calendar
time. As shown in the figure, there are some breaks in the sequence of
cumulative time. They indicate the engine cutoff due to the following
reasons and do not indicate in any way malfunctioning of the engine: use of
endurance test facilities for flight model testing and adjusting; legally
scheduled power cut and regular maintenance and inspection of the engine;
troubles in the ground support equipment such as a cooling system.
Moreover, through the entire test period, the engine has successfully
maintained the required thrust performance level, which clearly proves its
high potential as a reliable engine in the future.
[Image]
Picture: Running ion engine
The picture shows the running engine after it has achieved the target 18000
hours. Xenon is used as the propellant, and electrons are emitted from the
luminescent point, neutralizer, in front. Some wear due to Xenon sputtering
shown around the ion beam acceleration and outlet areas is well within
expectation and has no impact on the performance of the engine.
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