In article ,
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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.

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.

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.

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.

And again, that would depend on the exact nature of the damage, and that
is unknown due to the fact that they never made any attempt to examine it.
The smaller the hole the higher the chance of a successful emergency
repair. A huge hole might be impossible.

A huge hole was quite likely based on the data gathered and the ground
tests performed after the fact. The results shocked pretty much
everyone, because they all assumed that the RCC was "tougher" than the
silica tiles. Everyone was wrong.

The problem is that they could have known the nature of the damage on
day 2 of a 14-day flight, but there was never any effort to determine the
nature of the damage let alone try to repair it or come to a conclusion
about whether or not it could be repaired.

Agreed. The decision to not even attempt look for damage was a bad one,
especially in hindsight.

Saying stuff like, "Well given issues in the STS there was bound to be
a disaster sooner or later" is not an acceptable conclusion, IMHO.
Never the case in aviation or aerospace.

It may not be acceptable to you, but it's the facts. Spaceflight is
inherently risky and we really don't have enough experience doing it yet
to make it much safer than what it was "in the early days". This is
doubly true when SLS is going back to throwing away entire launch
vehicles instead of recovering parts of them for inspection and
refurbishment. It's triply true because SLS will be using five segment
SRBs whose thrust quite simply can't be safely terminated in an
emergency.

Yes there are risks in flying 120+ STS missions, but on this particular
mission there could have been a much better outcome, but they didn't even
-try- to assess the damage let alone make a decision about what to do
about it. That is what I meant by this mission being a management failure
and not a purely technological failure.

Yes, but you can point to the bad decisions made which led up to both
the Challenger disaster and the Columbia disaster. But you have to be
careful you don't fall into the trap of hindsight. Choosing to not fly
on those two days would *not* have eliminated all of the risk. The fact
is that NASA did write too many wavers for its own flight rules during
the shuttle program. Any one of those dodgey systems could have killed
the crew, which is why so many of those systems were improved post
Challenger and even post Columbia.

Hell, even the venerable Saturn V with its "perfect" flight record was a
hair's width away from disaster on at least one flight. Go read up on
the terrifying reality of the POGO problems it had and how close one
flight came to tearing itself apart. Did NASA get away with it?
Certainly. Could they have been more safety conscious with testing the
Saturn V instead of putting crews on top of what amounted to a launch
vehicle that still had issues? Absolutely. But we were in the Space
Race with the Soviet Union and everyone accepted the risk, even the
astronauts.

Anyone who wants perfect safety before they fly will never fly.
Luckily, there is no shortage of people willing to take the risk in an
attempt to attain the rewards.

"As safe as possible" is always a compromise.

Jeff
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