In article ,
says...

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.

Bad enough it was starting to cause the control system to have trouble
keeping the orbiter straight due to the increased drag on the side with
the hole. You would not have gotten that with a small hole.

See page 73 of the Columbia Accident Investigation Board's report.

https://spaceflight.nasa.gov/shuttle/archives/sts-
107/investigation/CAIB_medres_full.pdf

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.

I do not believe there was a Canadarm on that mission. EVA to that
location would have been "sporty" for sure but could have confirmed the
location and size of the hole.

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.

From page 173 of the Columbia Accident Investigation Board's report:

Because the NASA team could not verify that the repairs
would survive even a modified re-entry, the rescue option
had a considerably higher chance of bringing Columbia's crew
back alive.

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.

From page 173 concerning a rescue mission using Atlantis:

This rescue was considered challenging but feasible. To
succeed, it required problem-free processing of Atlantis
and a flawless launch countdown. If Program managers had
understood the threat that the bipod foam strike posed
and were able to unequivocally determine before Flight
Day Seven that there was potentially catastrophic damage
to the left wing, these repair and rescue plans would most
likely have been developed, and a rescue would have been
conceivable.


Also, there is a heck of a lot of data in the report (mostly in Chapter
3) which led NASA to conclude that yes there was about a 6 inch diameter
hole in the RCC panel(s) on the wing leading edge. This wasn't
speculation or based solely on one test which fired foam at an RCC
panel. It was supported by a lot of data gathered on launch (ground
camera footage), on orbit (detailed radar data of debris which separated
from the orbiter) and during reentry (various sensor failures,
anomalies, and high temperature readings inside the wing).

Jeff
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