Grex Agora47 Conference

Item 35: NASA management screwed up BIG time. Now what?

Entered by russ on Sat Sep 27 03:15:25 2003:

It was Tuesday, Jan. 21, five days after the foam had broken loose
during liftoff, and some 30 engineers from the National Aeronautics
and Space Administration and its aerospace contractors were having the
first formal meeting to assess potential damage when it struck the
wing.

Virtually every participant -- those in the room and some linked by
teleconference -- agreed that the space agency should immediately get
images of the impact zone, perhaps by requesting them from American
spy satellites or powerful telescopes on the ground. They elected one
of their number, a soft-spoken NASA engineer, Rodney Rocha, to convey
the idea to the shuttle mission managers.

Rocha said he tried at least half a dozen times to get the space
agency to make the requests. There were two similar attempts by other
engineers. All were turned aside. Rocha said a manager told him that
he refused to be a "Chicken Little."

The Columbia's flight director, LeRoy Cain, wrote a curt e-mail
message that concluded, "I consider it to be a dead issue."

New interviews and newly revealed e-mail sent during the fatal
mission show that the engineers' desire for outside help in getting a
look at the shuttle's wing was more intense and widespread than the
Aug. 26 final report of the board investigating the accident
described.

The new information makes it clear that the failure to follow up on
the request for outside imagery -- the first step in discovering the
damage and perhaps mounting a last-ditch rescue effort -- did not
simply fall through bureaucratic cracks, but was actively, even hotly
resisted by mission managers.
 
More at http://www.chron.com/cs/CDA/ssistory.mpl/world/2120733
71 responses total.

#1 of 71 by other on Sat Sep 27 03:50:28 2003:

What the hell is the point?  It was already established that there were 
no possible options for repair or salvage.

The mission managers had already accepted a scenario in which the ship 
could be fatally damaged and nothing could be done about it, and the 
engineers bought into it and allowed it to happen.  THAT's where the 
problem is.


#2 of 71 by i on Sat Sep 27 14:33:32 2003:

Saying "the Shuttle will break up on re-entry and the astronauts die
either way, so why bother to check?" is not a position that will fly
with much of the American public.  NASA is a very public agency of
our democratic government; no NASA official should need to be told
that this idea is a no-go.

Assuming that you'd want to keep the Shuttles flying after a disaster,
getting the best data you could on the damage & its consequences would
be obvious basic engineering.

From what i've seen, that there were "no possible options for repair or
salvage" (how about just rescue of the astronauts?) was established only
in the minds of pointy-haired bosses at NASA, and only after they went
looking for excuses to cover a decision that they'd already made.  NASA
engineers have saved or partly saved a great many missions gone wrong by
sundry feats of technological make-do & heroism.  "Saving the American
Shuttle's crew" would have great world-wide appeal, with huge political
pay-offs for heroes.  What might the Russians have done for the national 
glory of pulling a Russian rocket full of emergency supplies up to 
America's crippled Shuttle two hours before the oxygen ran out?  (Whole
world glued to TV's seeing our final approach and listening to good news
phone call from Kremlin to White House, Ivan.  Make sure side with huge
Russian flag is right-side-up on cameras!) 


#3 of 71 by other on Sat Sep 27 14:52:00 2003:

Hey, I didn't make the decision.  NASA had already decided by the time 
Columbia was launched that if at launch something so compromised the heat 
shield that the shuttle would disintegrate on reentry, there was nothing 
they could do about it anyway, so why bother to find out.  That was their 
attitude.  "We can't do anything about it anyway, so we don't want to 
know."


#4 of 71 by twenex on Sat Sep 27 15:23:27 2003:

Another example of how managerial incompetence can subvert attempts to
eliminate inefficiency, no matter how much $$ is or isn't thrown at the
problem.


#5 of 71 by drew on Sat Sep 27 20:21:11 2003:

    I think they ought to put the shuttles immediately back into service,
and draft all the managers and directors that made the don't-bother-to-
find-out decision as crew.


#6 of 71 by russ on Sat Sep 27 23:11:14 2003:

Re #1:

>What the hell is the point?  It was already established that there were 
>no possible options for repair or salvage.

Yes, but nobody knew that until the post-crash analysis was done.

There are two points worth reiterating here:

1.)  The damage caused by the impact was of unknown severity.  If the
     damage was such that a modified re-entry profile could have
     saved the vehicle and crew, we should have taken that course.

2.)  If the damage was sufficiently serious that a safe return was
     impossible, at least we would have known what kind of damage
     was caused by the foam impact.  Right now we are still guessing,
     because most of the evidence was destroyed by the re-entry.

As one who believes that Columbia should have been in a museum
instead of in orbit this past January, I think that taking steps
to see if it could have been saved would have been very worthwhile.


#7 of 71 by tod on Sun Sep 28 13:53:00 2003:

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#8 of 71 by tpryan on Sun Sep 28 14:02:13 2003:

        If it was known that there was that much damage within 24 
hours of launch, then the crew could have gone into long survival
mode, possibly extending consumables beyond the mission profile
timeline (plus the safety timeline for delay in landing) while
either supplies could be sent up (food, water, oxygen) or/and
rescue attempts be made.
        If we had the 7 person space station emergcy return
vechile at the space station, instead of trash pile of 
congressional funding, could it have been used.


#9 of 71 by bru on Sun Sep 28 14:19:10 2003:

I don't believe in the no-win scenario.

About time NASA adopted that attitude.  They had it in the 60's and we made
it to the moon and back, including some incredibly close calls with changes
and repairs done with materials at hand.

Maybe they could have been saved, maybe they could not.  The point is, they
didn't want to know, asnd they didn't try.


#10 of 71 by tod on Sun Sep 28 14:26:14 2003:

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#11 of 71 by murph on Sun Sep 28 15:54:08 2003:

Even if the situation was hopeless (or, *especially* if), they should have
made every attempt to assess/analyze the damage.  If they were to tell the
crew, "we don't think you're going to get down alive, but we want you to
make every effort possible to help us figure out what happened so that we
can get the next crew up and down safely," the astronauts would have agreed
without question.  I, cynically, see the fialure to investigate the damage
as a foolish hope that the shuttle would make it back without the public
(or Congress) ever getting wind of a problem in the space program.


#12 of 71 by slynne on Sun Sep 28 17:19:33 2003:

It is really easy to look at how things could have been handled 
differently after a disaster. Certainly the decision making process 
should be examined for flaws but I dont think it is fair to say that 
management was incompetent in this case without much more information. 



#13 of 71 by happyboy on Sun Sep 28 17:27:54 2003:

they prolly really need me and slynne to stand out in their
front yard and
yell stuart smally type slogans...

"IT'S OK YOU GUYS, YOU STILL HAVE A BETTER SUCCESS RATE THAN 
 THE FORD PINTO AND WE LIKE YOU!"


#14 of 71 by slynne on Sun Sep 28 17:55:43 2003:

Well they *do* have a better success rate than the Ford Pinto ;)


#15 of 71 by tpryan on Sun Sep 28 18:37:31 2003:

        If you were on the phone to a store, talking, solving a 
problem, then suddenly heard a scream, maybe a gunshot, then 
nothing, what would you do?  Would you go into action your own,
or would you tell your manager?  If you manager took no action,
Now, what would you do?

        It was those manangers who did not listen to their 
team.  Those experts that should have concerns.  Maybe they
even pre-intimidated them into not demanding loud enough.


#16 of 71 by slynne on Sun Sep 28 18:59:07 2003:

This wasnt something as clear as that. This would be more like I am on 
the phone with a store and the person on the other line tells me 
someone creepy just walked in. Ok, does that mean anything? If that 
person is later murdered and it is discovered that they told me that 
someone creepy walked in just before something bad happened, I am sure 
there would be people saying, "That's outragous! How could she have 
done NOTHING." As they say, hindsight is 20/20

Here is a situation where foam hits the shuttle and an engineer things 
that there *might* be a possibility that could cause problems. 
Management ignores the warning most likely due to cost pressures. It is 
completely possible that the engineer never fully communicated the 
probability that the foam could have caused a problem. It is entirely 
possible that the management made a decision because they believed 
there was only a very very small chance that the foam caused a problem 
and it would cost them a lot of money to find out for sure. 


#17 of 71 by drew on Sun Sep 28 19:02:29 2003:

It would cost a lot of money to radio the ship and have them send someone out
in a vacc suit to look?


#18 of 71 by rcurl on Sun Sep 28 20:34:40 2003:

They should have a mini-robot to fly around the ship and inspect it. That
doesn't  seem like it would be much of a technical challenge, or very
expensive. 


#19 of 71 by slynne on Sun Sep 28 20:53:18 2003:

I just think it is funny how whenever something bad happens, people 
start looking around for someone to blame. Then the people who get 
blamed start acting all defensive which prevents them from taking a 
good hard look at what happened. The fact of the matter is that every 
human makes mistakes and bad decisions. It sucks when a bad decision 
has dire consequences but it isnt like the NASA management was sitting 
around thinking "Those guys up there are in real danger but we never 
liked them anyway..." 

It is easy after the fact to tell if a decision was a good one or a bad 
one. It isnt so easy before the consequences of the decision is known. 
Frankly, some of the people in this item are such morons I seriously 
doubt they would be capable of making better choices than the NASA 
management. 


#20 of 71 by murph on Sun Sep 28 21:13:35 2003:

In general, NASA is incredibly careful; I think very few shuttles have
launched on time, ever, because they don't want to risk anything going wrong
in the launch.  In a culture where anybody can stop the launch at any time
for any reason (slight hyperbole), the fact that so little investigation was
done in this case seems uncharacteristicly negligent.  I do not, for example,
blame Bush for "not putting the pieces together" about 9/11, despite my strong
leftie leanings.  I'm much more willing to blame NASA for screwing up, despite
being a fanatic supporter of the space program, because it's so unusual for
them.


#21 of 71 by tpryan on Sun Sep 28 23:56:24 2003:

        Yes, President Reagan has his state of the union speech 
tonight, congradulating the the Teacher In Space.  We really
really need to launch Challenger.


#22 of 71 by lowclass on Mon Sep 29 00:01:17 2003:

 TOp management simply blew it off. As far as the foam is concened, A prior
flight had a "DENT" in one of the solid booster casings from a foam strike.
These are the can solid fuel boosters, that after being jettisoned, fall FROM
that height, and crash into the Atlantic to be recovered AND reused. HOW much
brain power does it take to extend the shown damage to the aluninum of the
solid boosters to the fragile tiles and carbon-carbon wing edge?

        Tope management blew it. the only nice thing THIS time, is the
reassignment and forced retirement of 11 of the fifteen Managers involved in
the failure to even THINK about the issues they were paid to resolve.


#23 of 71 by tod on Mon Sep 29 05:43:54 2003:

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#24 of 71 by russ on Tue Sep 30 02:14:12 2003:

Re #17:  Yeah, it would have cost a whole 'nuther Shuttle
mission, because Columbia was not carrying any EVA suits.


#25 of 71 by gull on Tue Sep 30 14:20:07 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.


#26 of 71 by tod on Tue Sep 30 15:28:43 2003:

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#27 of 71 by slynne on Tue Sep 30 16:05:23 2003:

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


#28 of 71 by drew on Tue Sep 30 17:25:19 2003:

Re #24:
    Am I the only one who thinks this is incredibly *stupid*?


#29 of 71 by rcurl on Tue Sep 30 17:51:57 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.


#30 of 71 by tod on Tue Sep 30 17:52:54 2003:

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#31 of 71 by drew on Thu Oct 2 05:59:30 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.


#32 of 71 by tod on Thu Oct 2 15:26:46 2003:

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#33 of 71 by drew on Thu Oct 2 20:40:32 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.


#34 of 71 by tod on Thu Oct 2 20:44:14 2003:

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#35 of 71 by mdw on Fri Oct 3 05:44:01 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.


#36 of 71 by gull on Fri Oct 3 13:02:31 2003:

EVA operations are thoroughly rehearsed before flight in
neutral-buoyancy tanks.  There's a good reason for this -- working in
zero G, especially while in a restrictive pressure suit, is difficult
and stressful and has all sorts of counter-intuitive aspects.  Trying to
access a part of the shuttle that no one had ever even thought about
accessing while in orbit before would probably have been hazardous and
unlikely to succeed.  In hindsight it was probably worth the risk, but I
can see how it might not have seemed that way at the time.


#37 of 71 by tod on Fri Oct 3 15:53:49 2003:

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#38 of 71 by drew on Sat Oct 4 19:56:17 2003:

What exactly is difficult and|or hazardous about EVA, other than the obvious?
Granted, there are risks like holing the suit, running out of air, getting
separated from the ship, and so forth. But are they so severe that they can't
be managed by such things as proper care and inspection of the equipment,
diligent use of safety lines, always topping off the air tanks before entering
the lock, and just taking ones time and not panicking?

It ought not to be physically stressful. Yes, the suit probably masses about
as much as you do. But it's not like you have to actually lift and support
that mass in full gravity. The only load on either muscles or tethers should
be what the crewman decides to put on them.

If someone for some reason pushes off against the ship with all his might,
and if he were athletic enough to do a 1 meter high-jump in normal gravity
- while wearing the vacc suit - he would be moving away from the ship at about
4.5 meters per second (10 MPH). This is just over 1/2000 of the delta-V that
it took to get up there in the first place, and probably a small fraction of
reasonable maneuvering reserves once in orbit. It should be easy enough to
go after him.

EVA operations should be routine. They're going to have to be sooner or later
if we want to build things in orbit like space stations and large spacecraft.
Every spacer should get a few hours of EVA in orbit as part of his training.


#39 of 71 by scott on Sat Oct 4 20:50:55 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.


#40 of 71 by aruba on Sat Oct 4 21:34:55 2003:

Well, I think Drew has a good point, though.  If something is hard, you can
either
  1) Plan it out meticulously before doing it every time, or
  2) Work on making it easier until it is.
Sounds like NASA has taken route 1 on EVAs.  The problem with Route 1 is
that you add a huge beaurocratic burden to doing what needs to be done, and
you can't do anything that hasn't been thought about for a long time ahead
of time.
   The problem with Route 2, of course, is that there may not be a solution.
But if you find one, or a series of small ones, then you have something much
more valuable than the procedure developed for Route 1.


#41 of 71 by gull on Sat Oct 4 21:44:58 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.


#42 of 71 by bru on Sat Oct 4 23:26:02 2003:

I never realized the tile were that fragile.  I mean, the damned thing gets
a lot of stress going into orbit.  If they were worried about a spacesuited
hand or foot damaging the damned things, they sure as hell should have been
worried about foam insulation at 5000mph+


#43 of 71 by gull on Sun Oct 5 00:06:14 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.


#44 of 71 by russ on Sun Oct 5 00:51:31 2003:

The lack of MMUs is actually the critical factor in inspections.
There are no handholds on the exterior of an orbiter, so anyone
trying to look at the wing or underside would be waving around
on the end of a tether like a bungee jumper.  It would be very
easy to do plenty of damage to the tiles just from bouncing
off them or rubbing the tether on them.

I will LART anyone who suggests suction cups.


#45 of 71 by murph on Sun Oct 5 01:46:03 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?


#46 of 71 by mdw on Sun Oct 5 03:14:56 2003:

The ceramic tiles are indeed quite fragile -- I believe they are fragile
enough that you can't walk across them on earth.  There are actually
several types of tiles, and some parts have been replaced by some sort
of fiberglass mat which is stronger, which simplifies maintenance.

One of the reasons there are lots of little tiles instead of big ones,
is so that a failure of a single tile isn't necessarily fatal to the
integrity of the whole thing.  At least for the first few landings, they
*were* losing tiles in flight, and they do regular inspections now to
try to avoid this.  Of course, if you lose enough tiles you expose the
tender underframe to incendiary forces and get catastrophic failure.


#47 of 71 by scott on Sun Oct 5 04:09:37 2003:

(suction cups are useless without an atmosphere)


#48 of 71 by russ on Sun Oct 5 04:59:28 2003:

Re #42, #43:  Yes, the tiles are THAT fragile.  (The thermal
blankets used on the payload bay doors are fabric, and probably
tougher.)  I have held a Shuttle low-temperature tile in my
hand.  It bore the scars of previous handlers' experiments
with its toughness vs. that of their fingernails.

As Jim Loudon said (paraphrased due to memory lapse), "It feels
like you can score it with your fingernail.  YES, YOU CAN."

The tiles have a very difficult set of requirements; they have
to cover almost the entire exterior surface of the vehicle,
and they have to insulate the aluminum structure against
re-entry heat while being light enough to let the whole thing
fly.  At the time the Shuttle was designed, the best they
could do was sacrifice most of the mechanical strength they
might otherwise have wanted.  Since then thermal blankets
have replaced tiles in some of the lowest-temperature
regions, but the bulk of the exterior still relies on spun
silica for its integrity during re-entry.

(As a geek, I wonder about our modern materials such as
high-Tc superconductors and ponder the possibilities of using
magnetic barriers to hold the plasma flow at a safe distance
from the skin.  Unfortunately, I'll bet that nobody's even
researching this seriously due to lack of funding.)


#49 of 71 by drew on Sun Oct 5 06:16:49 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.


#50 of 71 by mdw on Sun Oct 5 06:41:48 2003:

In order for the shuttle to "move a short distance, roll, and come back"
it has to fire maneuvering thrusters, scattered in random locations
across the shuttle.  I wouldn't care to be in an EVA suit hit by the jet
of one of those things -- the jet itself *might* be harmless, but it's
probably going to impart significant random delta V and angular
momentum, and without an MMU (or SAFER), that's probably going to be
fatal.  This is a good example of the reason they reherse and plan these
things out on the ground before trying them out in space.  Without
gravity and a convenient flat surface, *everything* is much harder.


#51 of 71 by aruba on Sun Oct 5 14:11:07 2003:

But harder doesn't mean impossible, and it certainly doesn't mean "not worth
doing".


#52 of 71 by murph on Sun Oct 5 14:47:50 2003:

I think that, in the case of putting an astronaut in space and maneuvering
the shuttle around him, "harder" means "basically impossible".  The space
shuttle is not a graceful beast; trying to move it around like that would be
a laughable proposition.


#53 of 71 by gelinas on Sun Oct 5 15:29:10 2003:

(There is work being done with plasma containment, but it seems to be aimed
more at fusion power than heat shielding.  Still, things seem to spin off of
basic research. ;)


#54 of 71 by scott on Sun Oct 5 17:23:32 2003:

It might be feasible to have the shuttle and a camera satellite coincide, and
have the shuttle do a slow roll wile being photographed.  Being out of the
atmosphere should help with getting a good image.


#55 of 71 by rcurl on Sun Oct 5 19:05:18 2003:

The shuttle is  "graceful" enough orient and dock with the space station.
No more maneuverability than that would be necessary for an inspection.
The camera satellite can, as I've mentioned, be released from  the
shuttle itself.


#56 of 71 by russ on Sun Oct 5 19:13:40 2003:

Re #49:  The high-Tc superconductors I'm talking about are the
ones which run at temperatures around 80 K, not 3000 K.  The
Shuttle carries liquid oxygen (BP around 83 K) for the fuel
cells, so chilling a superconductor loop to that temperature
shouldn't require any consumables that aren't already carried.
The liquid hydrogen is another possibility, but I'm not sure
how much heat it would sop up in the boiling process; the
delta-H-fg is pretty small as the entropy increase is about
the same as for other diatomic gases but the absolute
temperature is much closer to zero.

If we could find a way to hold the hot gases at a distance
that seriously limits the heat transfer to the vehicle,
something like the Shuttle could use titanium leading-edge
skins instead of brittle carbon-carbon.  The other virtue
of a magnetic system is that you can test it before hitting
the atmosphere and be sure it's working.


#57 of 71 by rcurl on Sun Oct 5 19:37:50 2003:

That can be done with transpiration cooling. This is done by using a
porous surface and forcing a gas out through the surface, and uses
comparatively very little gas compared to that which would be required to
just cool the surface. The transpiratioin moves the hot boundary layer
further from the surface.  It has been used to protect gas turbine blades
from heat. I would think, though, this would be mechanically complicated
for the shuttle and of course would add extra weight for the piping and
gas storage and control. The tile system was probably driven mainly by
weight concerns. 



#58 of 71 by gull on Sun Oct 5 20:57:51 2003:

I recall years ago they experimented with a system for reducing the drag
of aircraft wings that involved injecting compressed air into the
airstream through small holes along the wing surface.  The system worked
great, but the problem of keeping the holes clean turned out to make it
totally impractical.  A transpiration cooling system might have similar
problems.

Maybe our primary mistake was going to a reusable spacecraft to begin
with.  I've heard it said that each shuttle launch costs *more* than a
Saturn V launch would, so it seems like a reusable spacecraft has been a
poor tradeoff.  You have a lot more heat shield options if you don't
need to reuse the shield for another launch.


#59 of 71 by other on Mon Oct 6 01:30:17 2003:

May if the vehicle was reusable but the heat shield was one-time?


#60 of 71 by bru on Mon Oct 6 02:08:11 2003:

I was thionking something similar.  What were the heat shields of previous
craft made of?  Weren't they a spray on paint like material?  Could something
like this be applied after every use of the shuttle?


#61 of 71 by gelinas on Mon Oct 6 02:21:00 2003:

"Materials: Capsule hull is titanium coated in fiberglass insulation,
covered with shingles of nickel-steel alloy. The rounded heat shield on
the base is made of fiberglass and a strong plastic called phenolic resin"
(http://www.casciencectr.org/Exhibits/AirAndSpace/HumansInSpace/Gemini11.ph
p).


#62 of 71 by gull on Mon Oct 6 02:41:38 2003:

I think some very early Soviet designs even used oak.


#63 of 71 by russ on Mon Oct 6 03:11:53 2003:

Re #58:  You've got it backwards.  The boundary-layer control
systems work by pulling the stagnant surface air in through
the holes; blowing air out causes the airflow to separate.

Re #57:  Transpiration cooling requires a coolant; it's just
another form of ablator.  NASA went from ablative heat shields
to refractories because the long, gradual descent of Shuttle
would have required way too much weight of ablator.  The
heating rate of Shuttle is low, but the total heat load is high.

The advantage of a magnetic shield is that it does not
require expenditure of mass to renew the protective layer.
Now I'm wondering how hard it would be to perform a test on
a Shuttle external tank.  You could put the superconducting
coils inside the oxygen and hydrogen tanks and energize them
with batteries after separation from the orbiter; you'd have
your test results a few minutes later when the tank hit
atmosphere over the Pacific.


#64 of 71 by scott on Mon Oct 6 13:38:20 2003:

Re 60:  The big problem with trying to use the pre-Shuttle heat shield designs
is weight.  The old space capsules were much smaller than the Shuttle, asd
so a heavier material was feasible.  If they put that stuff on the whole
Shuttle it'd never get into space.


#65 of 71 by gull on Mon Oct 6 15:54:21 2003:

But you could also save a lot of weight in other areas if you weren't
planning on re-using the spacecraft.


#66 of 71 by tpryan on Tue Oct 7 00:13:51 2003:

        'Unheard of' means not dreamed of yet,
        'Impossible' means not yet done.


#67 of 71 by russ on Wed Oct 8 02:18:17 2003:

I saw an editorial the other day (by Jake Garn?) claiming that
we needed to put the Shuttle back into service ASAP and that
any alternatives were ten years off.

Funny, I don't think it would take more than a few months for
Scaled Composites to turn out a graphite-fiber version of the
Apollo command module.  We could be flying in two years, I bet.
Given our advances with solid-state devices such as fiber-optic
gyroscopes, it should be very easy to build a vehicle that
could be flown to the station, left there for months to years,
and flown back safely.  It would just come down under a 'chute
instead of with wings, and hit water instead of pavement.  BFHD.


#68 of 71 by gull on Wed Oct 8 14:27:46 2003:

Of course, why design it ourselves when we can buy it off the shelf from
the Russians? ;>


#69 of 71 by tod on Wed Oct 8 16:52:43 2003:

This response has been erased.



#70 of 71 by albaugh on Mon Oct 27 18:32:07 2003:

http://www.unitedmedia.com/comics/peanuts/archive/peanuts-20031027.html


#71 of 71 by willcome on Thu Nov 27 07:43:30 2003:

He didn't write enough about whores.


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