This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Microwave ion engine prototype model achieved 18000 hrs of autonomous
endurance running!

ISAS, Japan
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.


http://www.isas.ac.jp/e/new/release/2002/12_04.html

-END OF FILE-
=============

---