On Saturday, February 4, 2017 at 2:54:34 PM UTC-5, Jeff Findley wrote:
In article ,
says...
Wrong. The wing leading edge was reinforced carbon-carbon composite.
This was the material on the shuttle which could withstand the most
reentry heating. This isn't something you can "MacGyver" with any spare
parts on board Columbia.

That depends on the exact nature of the damage, and given that it wasn't
surveyed by EVA or by shuttle-based camera or by telescope, we don't know
whether it was a big hole or a small hole, or whether it was on the
leading edge or behind of there. That could not be ascertained after the
fact from the debris on the ground.

True there was no direct evidence. But, based on camera video the size
of the chunk and its velocity when it hit the wing leading edge was
estimated. So, a ground test was performed which was quite shocking in
the size of the hole it created. From Wikipedia:

As demonstrated by ground experiments conducted by the Columbia
Accident Investigation Board, this likely created a 6-to-10-inch
(15 to 25 cm) diameter hole, allowing hot gases to enter the wing
when Columbia later re-entered the atmosphere.

That's a huge hole when you consider the aerodynamic heating at
hypersonic speeds encountered during reentry.

It is still unknown how large the hole was and whether it was
on the leading edge, or rearward where it would have considerably
lower reentry temperatures.

Also the nature of the damage, was there enough internal structure
to support a patch or was that severely damaged? We don't know
because nobody looked.

If they did an EVA or had a Canadarm with a remote camera, they
could have made a very accurate assessment of whether it was
repairable, and on day 2.

If clearly unrepairable, then a rescue mission would be the only
way to rescue the crew. They would have another 12 days to mount
that.

Sending another shuttle on a rescue or repair mission would have had its
own risks to that vehicle and crew, so that would need to be considered
carefully before making that decision.

So? Make it an all volunteer crew (you'd only need a minimal crew
anyway to make room for the crew being rescued).

Besides, rescue crews of all sorts are quite often at higher risk than
when performing training. When you're trying to save someone's life,
many people will take that risk. Considering many of them came to NASA
from the military, I'd wager that you'd far more volunteers than you'd
need.

I mentioned the vehicle as well, you have one in orbit that may
already be lost, and then a second one that you are rushing to
launch. If the rescue mission meets disaster then the one in orbit
doesn't get rescued, the fleet drops from four orbiters down to
two orbiters, and at Endeavour's 1992 cost we're looking at least
$3 billion per orbiter to replace the two that were just lost,
and NASA will have a very difficult time finding that kind of
funding. If the fleet stays at two orbiters then its functionality
is rather limited.

Plus the STS rescue mission will cost the typical $500+ million.

That is why I suggested sending an expendable rocket with materials to
for Columbia crew to make an emergency patch. Titanium sheets and
sheets of ablative material and fasteners, for example.

But that quite simply would not work for the RCC wing leading edge. The
best NASA could do was make a repair kit for the tiles.

Again, they didn't know whether it was the leading edge or the exact
nature of the damage. The expendable rocket could send up several tons of various materials, using whatever was deemed necessary.

As far as to whether an emergency patch would work well enough to at
least make a normal landing, NASA investigators determined that on-orbit
repair by the shuttle astronauts was possible but overall considered high
risk, primarily due to the uncertain resiliency of the repair using
available materials and the anticipated high risk of doing additional
damage to the Orbiter.

Almost certainly such a "repair" would have been higher risk than
mounting a rescue mission. Again, rescue crews routinely risk their own
lives. This wouldn't have been any different.

They had no chance of surviving with the current damage. Repairing
or attempting repairing would not have increased risk on a 0% chance
of survival. Using an expendable rocket would not have risked human
lives and it would have been far less expensive than a shuttle mission.

Again, a damage assessment could have determined whether it was
repairable.

....
I have no disagreement with the remainder that was snipped, I agree
that spaceflight is inherently risky, and about how Apollo/Saturn V
was fortunate that no lives were lost. I fully accept the fact that
it is risky and that disasters can occur.

I just find it regrettable in how Columbia was lost, more on the basis
of management failure than any technological failure.