Tani brought out a new motor earlier today, which NASA hoped would fix
one of two failures that have weakened the power assembly system on
the International Space Station, and threatened to forestall further
construction of the station.
Early in the spacewalk, the two NASA astronauts removed a 2.5-foot
container (a beta gimbal assembly housing) that encased the old motor.
With the Sun hidden behind the Earth, the two astronauts then removed
the fasteners that held down the defective motor, and disconnected its
Then, they installed the new motor in its place.
They were working in darkness because if sunlight (or any form of
artificial light, say from a flashlight they might be carrying) were
to fall on the solar array, 160 volts (200 amperes) of electricity
would be going through the cables that the astronauts are
disconnecting and connecting, along with the chance that the
astronauts might accidently touch a hot spot on the solar arrays.
As of about 9:30 a.m. CST (which is Houston time in Mission Control at
the Johnson Space Center, where ground controllers are directing the
spacewalk), NASA is reporting the initial testing of the new 250-pound
electric motor shows it is working properly. It has already tilted
about three degrees, showing initially that it can perform its new job.
The astronauts were a little bit over 5.5 hours into their spacewalk
when this first test occurred.
The old motor stopped working in early December 2007, which compounded
a problem that occurred about three months earlier when a solar alpha
rotary joint (SARJ) on the right (starboard) side of the main power
truss had to be turned off.
With the new solar tilting motor installed, the astronauts are now
working on the other power-generating problem outside of the space
shuttle�the SARJ. The jammed starboard joint is supposed to
continuously rotate 360 degrees to automatically keep the solar arrays
on the right side of the shuttle pointed in the direction of the Sun.
However, it was earlier found to be malfunctioning. Later, it was
discovered by Tani, while in a spacewalk, to be full of metal shards,
which supposedly somehow causing it to malfunction. NASA is still
unsure the original of this problem.
The SARJ is being now inspected by the astronauts. They removed the
blanket-like thermal covers that encase sections of the joint. They
will photograph the bearings and other parts of the joint.
At the moment they are looking at the surface of the gear teeth�seeing
just a �dusting� of metal debris. Earlier, an inspection found that
internal bearings and gears might be grinding inside the joint.
NASA has directed the new solar motor to rotate. Did it work? Please