[net.columbia] Speculation III

piner@pur-phy.UUCP (Richard Piner) (02/04/86)

   I have seen the NASA films on the right SRB and there is no doubt
that the fuel burned through the skin. However, I still have doubts
about this causing the explosion the destroyed the Challenger.
   The reason is this, the external tank contains LIQUID H2 and O2.
In order for the burning solid fuel to rupture the ET, it would first have
to burn through the ET insulation. This insulation is holding liquid H2
at around 20 degrees Kelvin. That's cold. The insulation has to
have a huge R value. After you burn through that, you still have to
get through the aluminum tank. That tank contains liquid. Try this
experiment. Take a paper cup and fill it with water. Now take a propane
torch, and try burning a hole through the bottom. What happens? The
water boils but the cup does not burn. If indeed the SRB "torch"
burned through the ET insulation, it would have boiled the liquid
H2. This would have caused an increase in pressure in the tank.
Long before it could burn a hole in the aluminum tank, pressure
sensors in the Challenger would have been screaming bloody murder.
I'm almost sure this information would have been in the down link.
But NASA says the telemetry data shows nothing unusual. I doubt
they are lying about that.
   The only way that a flame from the SRB could have caused the
ET to explode instantly, would be if there were an internal leak
inside the ET. Such leaks are not uncommon in cryogenic systems.
But doesn't the ET have leak sensors in it? Or is there a nominal
leak rate. A small leak could be ignored if there aren't any flames
about. But of course this time there was.
   I can't help but have an uneasy feeling that there were two failures
in the shuttle system. One was the SRB, and the other was the one
that blew up the ET. I hope that NASA does not just assume the SRB
at fault and stop at that. I also feel that we are not getting enough
information from NASA. See my next posting.

					Richard Piner
					piner@pur-phy.UUCP

dday@gymble.UUCP (02/07/86)

In article <1955@pur-phy.UUCP> piner@pur-phy.UUCP writes:
>   The only way that a flame from the SRB could have caused the
>ET to explode instantly, would be if there were an internal leak
>inside the ET. Such leaks are not uncommon in cryogenic systems.
>But doesn't the ET have leak sensors in it? Or is there a nominal
>leak rate. A small leak could be ignored if there aren't any flames
>about. But of course this time there was.
 
I've seen speculation in both the Washington Post and Newsweek that the
errant flame might have either burned through the feed line from the 
liquid hydrogen tank or ignited the self-destruct mechanism attached to
the ET.  I have no idea, just reporting what I read.



-- 

UUCP:	seismo!umcp-cs!dday                      Dennis Doubleday
CSNet:	dday@umcp-cs				 University of Maryland
ARPA:	dday@gymble.umd.edu			 College Park, MD 20742
Fan of: Chicago Cubs, Chicago Bears, OU Sooners	 (301) 454-6154

mahar@fear.UUCP (mahar) (02/08/86)

>    The only way that a flame from the SRB could have caused the
> ET to explode instantly, would be if there were an internal leak
> inside the ET. Such leaks are not uncommon in cryogenic systems.
The External Fuel tank is the only part of the shuttle system
that is not recovered after a flight. That means no one has ever
examined a used external tank. How much they leak and how much strain
damage they receive is speculation. I suspect NASA has a good idea
what the state of the external tank is after a launch but the solid
rocket boosters had some suprises so I don't think anybody knows
for sure.

ix742@sdcc6.UUCP (James Hayes) (02/08/86)

Richard Piner writes in article <1955@pur-phy.UUCP>:

>
>   I have seen the NASA films on the right SRB and there is no doubt
>that the fuel burned through the skin. However, I still have doubts
>about this causing the explosion the destroyed the Challenger.
.
. READ ON
.
>   The only way that a flame from the SRB could have caused the
>ET to explode instantly, would be if there were an internal leak
>inside the ET. Such leaks are not uncommon in cryogenic systems.
>But doesn't the ET have leak sensors in it? Or is there a nominal
>leak rate. A small leak could be ignored if there aren't any flames
>about. But of course this time there was.
.
.
.
>
>					Richard Piner
>					piner@pur-phy.UUCP

There was talk of the Challengers "destruct pack" detonating.
The theory aparently accounts for the red-orange cloud that
appeared.  Also: What about the small explosion toward the front of
the Challenger.  Isn't that where the destruct pack is detonated?

-Jim Hayes
ix742%sdcc6@SDCSVAX.ARPA

peterb@pbear.UUCP (02/08/86)

/* Written  4:50 am  Feb  4, 1986 by pur-phy!piner in pbear:net.columbia */
/* ---------- "Speculation III" ---------- */

   I have seen the NASA films on the right SRB and there is no doubt
that the fuel burned through the skin. However, I still have doubts
about this causing the explosion the destroyed the Challenger.
   The reason is this, the external tank contains LIQUID H2 and O2.
In order for the burning solid fuel to rupture the ET, it would first have
to burn through the ET insulation. This insulation is holding liquid H2
at around 20 degrees Kelvin. That's cold. The insulation has to
have a huge R value. After you burn through that, you still have to
get through the aluminum tank. That tank contains liquid. Try this
experiment. Take a paper cup and fill it with water. Now take a propane
torch, and try burning a hole through the bottom. What happens? The
water boils but the cup does not burn. If indeed the SRB "torch"

 . . . . . . .

Ok, this is true. But there are other things that can fail causing the
"instant" explosion that was seen.

From my memory, The ET's weight was reduced, and pressure biasing was
used to provide the surface rigidity not provided by the lighter structure.

This pressure bias exists between the feul/oxidizer tanks, and the skin of
the ET. So if you take your blowtorch to a presurized can that contains
cyrogenic fluids. Between the extreme temperature differentials, and the
internal prerssure, the surface metal will flow and finally rupture.

Once ruptured, the rigidity of the tank is reduced, and so is the resonance
of it. This could be the ''secondary'' cause of the ET explosion that you
were looking for.

Peter Barada
ihnp4!ima!pbear!peterb

henry@utzoo.UUCP (Henry Spencer) (02/09/86)

> In order for the burning solid fuel to rupture the ET, it would first have
> to burn through the ET insulation... The insulation has to
> have a huge R value. After you burn through that, you still have to
> get through the aluminum tank. That tank contains liquid [which cools it,
> and would increase tank pressure due to boiling]...

You are assuming that the jet gets through the insulation by heat.  Don't
forget sheer mechanical force.  Rocket engines have been used, experimentally
at least, for cutting tunnels through solid rock.  The main exhaust jet from
an SRB has a force of (I forget the exact number) something like a couple of
*million* pounds.  If even a small fraction of that hits a small area of a
thin-walled metal tank, it will go straight through.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry

donch@teklabs.UUCP (Don Chitwood) (02/11/86)

With regard to the question of how the SRB exhaust leak could have
ignited/precipitated the main fuel tank explosion, here's an old
observation of mine.

I've worked with liquid nitrogen as used with high vacuum systems for
several years.  One time, while working with a "sorbtion pump" (a type
of vacuum pump that requires immersing the pump chamber in a bath
of liquid nitrogen), I observed how readily liquid nitrogen
could be brought to a boil.

It happened like this:

After pumping with a sorption pump, it should be baked
at some elevated temperature to drive off all the gaseous products
trapped within it.  This is commonly facilitated by having a built-in
tunnel into which a heater element (just like on an electric stove, except
they are usually rod-shaped) is placed.

I had finished pumping my system, and was preparing to plug in the heater
to bake out the pump.  The whole thing was immersed in a bath of liquid
nitrogen and, of course, was equilibrated thermally with the bath. 

Well, the very INSTANT I plugged in the heater,
the liquid nitrogen began boiling furiously, just like the initial immersion
of the pump into the bath.  Certainly, there was a time lag, but it was less
than I could detect visually.  Repeating the experiment several times produced
the same effect.

So, I would suggest that it doesn't take much heat to make liquid hydrogen
boil.  The insulation is designed for a given temperature gradient across from
the inside to the outside.  Once the temperature on the outside starts to rise,
its just a matter of time (and temperature, for that matter) until the inside
temp begins going up, too.  Add erosion of the insulation by the rocket
flame from the SRB leaky seal, and things can happen in a hurry.

Don Chitwood
Tek Labs
Tektronix, Inc.
Beaverton, OR

lmc@cisden.UUCP (Lyle McElhaney) (02/12/86)

> 
> Once ruptured, the rigidity of the tank is reduced, and so is the resonance
> of it. This could be the ''secondary'' cause of the ET explosion that you
> were looking for.
> 
The latest theory, from Aviation Week as reported in the local papaer
here, is that the lower support of the right SRB broke loose under the
side-wise pressure from the plume, and the SRB pivoted on its upper
support, hitting the oxygen tank with its tip, crushing it and causing a
leak which lead to the explosion. It does explain how the oxygen tank
suddenly became involved in the accident.