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From: adamsd@crash.UUCP (Adams Douglas)
Newsgroups: sci.space
Subject: Re: questions about Challenger commission report
Message-ID: <343@crash.UUCP>
Date: Sun, 19-Oct-86 18:32:54 EDT
Article-I.D.: crash.343
Posted: Sun Oct 19 18:32:54 1986
Date-Received: Tue, 21-Oct-86 22:34:11 EDT
References: <358@petrus.UUCP>
Reply-To: adamsd@crash.UUCP (Adams Douglas)
Distribution: net
Organization: JPL/NASA
Lines: 38

In article <358@petrus.UUCP> karn@petrus.UUCP (Phil R. Karn) writes:
>..."Fracture mechanics analysis indicates that a hole in the case
>larger than one inch would cause the entire case to rupture in a few
>milliseconds...My question is, once the joint burned through, why didn't the
>entire case quickly rupture, given the comment on page 55? Is there something
>different about the behavior of a hole in the joint versus one between the
>joints?

Yes, considering that by "case membrane failure" they were referring to a
fatigue or flaw induced crack in the casing. A crack with sharp edges
would propagate rapidly across the casing under the stresses from the
gas pressure. The hole burned in the case at the joint was burning
where there already was a 'crack' (the joint) to absorb the strain.

>By the way, note what appears to be a grounding strap attached to the
>recovered SRB pieces shown in page 80. Was this a safety precaution to avoid
>the possibility of igniting any remaining propellant? Having never actually
>seen SRB propellant, I don't know if the brown stuff on the inside of the
>piece is propellant or case liner. I thought the propellant was supposed to
>be "battleship gray" in color, though.
>
>Phil

The strap was indeed there to guard against igniting the propellant
remaining on the case wall. I don't know what color it is supposed to
be, but remember it had been immersed in seawater for awhile AND you
are looking at the burned surface, not virgin propellant.



-- 
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Adams Douglas	ARPA:crash!adamsd@nosc.arpa  AT&T:818-354-3076
JPL/NASA	UUCP:{akgua | hplabs!hp-sdd | sdcsvax | noscvax}!crash!adamsd

My opinions! Do you hear? MINE! Not JPL's.

"Do not be angry with me if I tell you the truth." -- Socrates