Arty Hues wrote in
rver.com:

We're told, that this spacewalk, is to replace a "failed power
component".
So, given the risks of spacewalks, why are any sub-system modules
placed
outside?

To minimize the number of penetrations through the pressure hull (both the
power source and the load are outside, in this case), minimize the number
of connections through hatches (lesson learned from Mir), and minimize
potential crew exposure to ammonia (used to cool external power
components).

The only reason I can see, is fire danger in an oxygen rich field.

ISS atmosphere is 20% oxygen, no more oxygen rich than sea level air, and
no higher fire hazard.

But then, during the last, (deadly), shuttle flight, at one point
I
felt, something was not right. And maybe they should seek out the
ISS, and via airlock, or spacesuit, find refuge. Even if Nasa found
that shuttle could never land, could the ISS have helped? Say, their
optics viewed a shuttle with no left wing? Was there no way, that
shuttle could not find/join the ISS, and transfer the crew?

No. Columbia was in the wrong orbit to reach ISS.

Didn't NASA have any hint, something was wrong?

They had launch video showing the foam impact, but no direct evidence of
wing damage.

If so, they could have
sent out a spacewalk. With the fatal flaw revealed. That the shuttle
could never return to earth. If the crew couldn't survive via the
ISS, they were doomed. If so, why not? Fuel, orbit, time, air,
speed, or what? Interlocks or airlocks?

The ability to remove CO2 from the atmosphere was the limiting factor. Had
STS-107 been powered down starting on flight day 7, they could have held
out 30 days (through February 15). Oxygen would have lasted one more day.

Was it a moot point? If
launch video showed insulation damage, why couldn't there have been a
spacewalk to check on this? Send out an expert, to say either, "Looks
OK", or "There are some large holes in the shuttle's insulation".
"Looks OK"; and there could be a chance for landing. If not, seems the
crew could only have looked towards the ISS, for a chance at life.

Again, Columbia could not have reached ISS. If the spacewalk showed fatal
damage, the only two options were for the crew to attempt to improvise a
patch to the wing (which almost certainly would not have worked, given the
difficulties NASA has since encountered developing RCC repair techniques),
or for the crew to power down and try to hold out until Atlantis could be
launched to rescue them (which was perhaps just barely possible, but would
have involved risking a second orbiter and crew to the same problem that
doomed the first).

We've got an International Space Station in orbit. Seems any nation
that
sends humans into space, should be able to use the ISS, as a 'safety
raft'.

There are an infinite number of possible orbital planes in low Earth orbit,
and ISS occupies only one. It is prohibitively expensive, fuel-wise, to
change planes once in orbit. Requiring that all manned spacecraft be able
to abort to ISS is tantamount to demanding that all manned missions be
planned for ISS in the first place. It is thinking such as yours that got
the Hubble servicing mission cancelled. It is thinking such as yours that
would prevent us from ever returning to the Moon, or travelling to Mars.

--
JRF

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