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From: rjnoe@riccb.UUCP (Roger J. Noe)
Newsgroups: net.columbia
Subject: Re: SRB joints
Message-ID: <636@riccb.UUCP>
Date: Mon, 24-Feb-86 18:16:42 EST
Article-I.D.: riccb.636
Posted: Mon Feb 24 18:16:42 1986
Date-Received: Wed, 26-Feb-86 20:32:07 EST
References: <8931@ucla-cs.ARPA> <9201@ucla-cs.ARPA>
Distribution: net
Organization: Rockwell International - Downers Grove, IL
Lines: 24

> If the important
> point is that the propellant should insulate the body of the booster
> from the heat of combustion, then why the concern over the O-rings as a
> line of defense?  And if the O-rings are liable to burn through before
> the SRB walls themselves, then why the great concern over cracks in the
> propellant?
> -- 
> Rich Wales // UCLA Computer Science Department // +1 213-825-5683

The O-rings are to form a pressure seal so that the putty could not be
pushed back so far that fire could reach the O-rings.  If the heat of
combustion does reach the second O-ring, it is almost certain that it
will "burn through" (really leak out) the SRB casing.  Actual burn-through
of the steel casing is far less likely than a leak out of the joint.  If
there were no joints (segments) then there would be no need for putty and
therefore no need for O-rings.  But the cold is speculated to have (1)
allowed the reactant to have contracted away from the container wall
and created a gap, and/or (2) decreased the resiliency of the O-rings so
that they did not form a good pressure seal.  These (and other factors,
all of which are just speculation so far - of course) could all have
contributed to not a burn-through of the SRB casing, but a leak-through
at one of the segment joints.
--
Roger Noe			ihnp4!riccb!rjnoe