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Having problems with the circulator turbine again, the
Cryo-Cooler was cut-open and reworked with repairs and
the HOST testing mission, the NCS was returned to
Goddard and was prepared for its target purpose
- installation into Hubble.
During a spin test after the HOST mission, the circulator
again failed to start. Investigation revealed substantial
damage to the surfaces between the shaft and bearings.
The damage was attributed to the effects of the
frozen contaminants during prior ground tests.
In response, the circulator was removed from the
NCS. New rotors and bearings were fabricated and
installed, and the machine was re-welded into the
assembly. The shaft and bearings of the circulator
were replaced with a new design incorporating a
diamond-like-coating to improve margin against wear
from contaminants. Improved contamination control
procedures were also implemented to reduce the potential
for contaminants entering the loop.