response 25 of 71:

Sep 30 14:20 UTC 2003

Re #14: I think the Ford Pinto's accident rate was much less than 1 in 100.

Re #24: Not to mention that there's nothing to hold onto in that area of
the Shuttle.  It was never meant to be accessable during EVA.

response 27 of 71:

Sep 30 16:05 UTC 2003

So you see, in the Plesco family NASA has a better accident rate with 
the Shuttle than Ford has with the Pinto. 

response 29 of 71:

Sep 30 17:51 UTC 2003

Re #25: it is not necessary to hold onto anything - a tethered EVA
can provide its own maneuverability.

Perhaps even simpler than a roving miniature inspection vehicle is
one that has less maneuverability, but which can inspect the shuttle
while the shuttle is maneuvered. 

I think they should have designed the external tanks so that nothing
could come off to strike the shuttle. They knew of this problem from
earlier flights but only  showed after the fact that foam could puncture
the wing. Considering how much testing went into wing surface  design,
including using wind tunnels, this oversight is incomprehensible.

response 31 of 71:

Oct 2 05:59 UTC 2003

Re #24:
    According to the FAQ, (google search "space shuttle columbia faq"), the
crew had two (2) EVA-capable vacc suits, in addition to their 7 (one per crew
member) flight suits. Also, the airlock tunnel has a hatch to dorsal, enabling
use of the lock for EVA whether or not there is something in the cargo bay.
There were no MMUs, but there was, apparently, some tether line, as there was
a contingency plan to use 60 ft of it or so to crawl out and close the bay
doors manually in case they should jam. How much additional line there was,
I'm not clear on. But given a sufficient length it should have been possible
to push off against one of the bay doors, to either port or starboard, and
end up by the ventral surface. Two people doing this could catch each other
and maintain position there. Getting back in would be as easy as reeling in
the tether.

response 33 of 71:

Oct 2 20:40 UTC 2003

The point of this item is that the reason the crew did nothing was that people
on the ground who saw something hit the hull and should have said something
just sat there and kept their mouths shut; and had someone just sent a message
"We saw a chunk of something hit the hull on take-off. We recommend you send
someone out to have a look", they would have found the damage, maybe could
have done *something* about it, or at least would know for certain what the
damage was. At any rate it ought to be up to the captain to decide whether
they can do something on their end, not administrators on the ground who
decide to say nothing.

response 35 of 71:

Oct 3 05:44 UTC 2003

I don't think it's surprising that there are things the people in the
shuttle program don't look for, simply because they don't have time.  If
they gave into every such urge to look for problems, they'd *never* get
anything done.  People and organizations make decisions like this all
the time.  If you are driving along, and your car makes a noise it never
made before, you *might* stop and look and try to figure out what the
noise is, or you might drive on and hope it's not a problem.  If you're
driving through a bad neighborhood, are you more or less likely to stop
& look?  Space makes any bad neighborhood on earth look like paradise.

It's quite possible even if somebody had been able to look at the
outside, that they wouldn't have learned enough to decide what to do.
If I remember right, significant damage was on the inside, where it
would not have been visible - and there was almost certainly nothing on
the shuttle that could have been used to fix it.  Doing an EVA to look
at the damage would have given the ground significant clues to the cause
of the disaster afterwards, but I can well see them deciding beforehand
that the risk of the EVA itself wasn't worth the small chance they might
learn something of value, especially given the great chance it would be
nothing they could fix.

Of course, now, with hindsight, we can challenge all the assumptions,
because obviously at least one of them was "wrong".  In an organization
that is (we hope) trained to consider all probabilities of failure, it's
not surprising somebody thought things were wrong beforehand.  This
probably happens with some frequency - something goes wrong, some people
panic over some possibility, they're overruled, and the shuttle lands
and the possibility turns out to be either a false alarm, or not
critical.  In this case, though, they were right, and the interesting
question is not why didn't we stop here in this case, but how can we
improve the not why didn't we stop here in this case, but whether we
have picked the right breakpoint for false negatives vs. false
positives, and if there's anything we can do to decrease the risk of
both.

response 39 of 71:

Oct 4 20:50 UTC 2003

Yeah, you'd think that.  Some of the very first EVA missions were almost
disasters, though.  The astronauts got overexerted, their helmets got steamed
up and they couldn't see, etc.  After that they started rehearsing every EVA
in the water tank and building special equipment & tools.  It's amazingly hard
to do even simple tasks if you don't have gravity to work against.

response 41 of 71:

Oct 4 21:44 UTC 2003

Re #39: There's also the danger of damaging the spacecraft, which I 
suspect is part of the reason no one has tried to access the heat shield 
portion of the shuttle while on orbit so far.

response 43 of 71:

Oct 5 00:06 UTC 2003

I'm not sure if they're actually that fragile, though they *are* made of 
ceramic.  I'm not saying it's likely there'd be damage, but it may have 
been a consideration.

The fact that the orbiter goes through stress going into and out of 
orbit is really beside the point, because those stresses are spread out. 
 Aircraft are often fragile when exposed to concentrated stresses or 
impacts, because they're made with distributed aerodynamic forces (and 
light weight) in mind.

response 45 of 71:

Oct 5 01:46 UTC 2003

If an astronaut bouncing around like a bungee jumper could do that much damage
to the tiles, it would seem like a good argument in favor of being worried
abouthigh speed projectiles.

And, anyways, couldn't the astronaut just use suction cups to stick to the
shuttle?

response 47 of 71:

Oct 5 04:09 UTC 2003

(suction cups are useless without an atmosphere)

response 49 of 71:

Oct 5 06:16 UTC 2003

    There is an important difference between a bungee jumper on the ground
and someone performing EVA on a tether in orbit. The Earthbound bungee
jumper will inevitably and in short order reach the end of the bungee cord,
stretch, and bounce back with the same speed that gravity accelerated him
to during the drop. A crewman on a tether need not bounce or even move
with any appreciable speed. He can just sit there, with the tether being
present merely as a safety measure. And if he does bounce, it can be with
a very small and gentle rebound.

    There are other things that can be done when someone forgets to pack
an MMU. One of them is to have the person on EVA just sit there (probably
pointing a video camera at the ship) while the ship moves a short distance
away from him, then does one or more 360 degree rolls, then comes back.
This does require faith on the part of the guy outside that his crewmates
will come back for him; I admit there are people that I would be unwilling
to do this with. But presumably shuttle crewmembers trust each other well
enough for this.


Re #48:
    If we get superconductors that can work at that high a temperature, it
may no longer be necessary to have heat shielding, as we might then be able
to build ships with hundreds of KPS of delta-V, and easily be able to spare
the 8 kps needed to slow down with thrusters instead of atmospheric drag.