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From: donch@teklabs.UUCP (Don Chitwood)
Newsgroups: net.columbia
Subject: Re: Speculation III
Message-ID: <3280@teklabs.UUCP>
Date: Mon, 10-Feb-86 18:58:29 EST
Article-I.D.: teklabs.3280
Posted: Mon Feb 10 18:58:29 1986
Date-Received: Wed, 12-Feb-86 07:47:43 EST
References: <1955@pur-phy.UUCP>
Organization: Tektronix, Beaverton OR
Lines: 39

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