[meteorite-list] Successful Re-Ignition of Ion Engine C Onboard Hayabusa

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 5 Sep 2007 10:43:08 -0700 (PDT)
Message-ID: <200709051743.KAA14397_at_zagami.jpl.nasa.gov>

http://www.isas.ac.jp/e/snews/2007/0820.shtml

Successful re-ignition of Ion Engine C onboard Hayabusa
Japan Aerospace Exploration Agency (JAXA)
August 20, 2007

Hayabusa spacecraft had been on the way to Earth with the ion engines B
and/or D powered on since April 2007, though it lost the functions of
chemical thrusters and two of three reaction wheels at the proximity
operation around the asteroid. At the rescue operation in 2006 the ion
engine C was not confirmed to exhaust the plasma jet. On July 28, 2007 a
series of the restoration works and a new operation sequence revived the
ion engine C again, which are accelerating Hayabusa on behalf of the
engines B and D aiming for the Earth return on 2010. Sharing the delta-V
duty among the multiple engines will secure a safety flight for the
homeward journey.

Because the severe solar radiation seemed to increase the temperature
beyond the safety zone to prevent the fuel leak, Hayabusa was operated
with the attitude leaned against Sun so as to avoid solar heat flux in
May. It passed through the perihelion at the solar distance 0.95AU on
June 7 without any problems. During this term the engine D accelerated
continuously Hayabusa as scheduled. At the end of July after
establishment of the safety temperature, the warming up of a power
supply by electrical heaters during several days and a special
operational sequence successfully ignited plasmas again in the engine C.
Then the Hayabusa's acceleration was shifted from the engine D to C
reserving the rest of operational life.

The turn-on of the engine C is good news for the homeward journey of
Hayabusa, which is still frighten at additional malfunctions. Since May
2003 each ion engine has been operated in space as follows

    Engine A: stand-by
    Engine B: about 9,500 hours
    Engine C: about 7,000 hours
    Engine D: about 13,500 hours
    Total: 30,000 hours

Hayabusa will continue the powered flight using the engine C till
November this year and then change to the ballistic flight with
hibernation mode.
Received on Wed 05 Sep 2007 01:43:08 PM PDT