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From: AI.CLIVE@MCC.ARPA (Clive Dawson)
Newsgroups: net.space
Subject: SRB Destruction
Message-ID: <8601312006.AA00727@s1-b.arpa>
Date: Fri, 31-Jan-86 14:51:27 EST
Article-I.D.: s1-b.8601312006.AA00727
Posted: Fri Jan 31 14:51:27 1986
Date-Received: Sat, 1-Feb-86 20:24:49 EST
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Organization: The ARPA Internet
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One aspect of the SRB self-destruct mechanism which has bothered me the
most is the fact that a single action will destroy BOTH SRB's (and perhaps
the external tank as well?).  It is clear that recovery of the intact
casings would have been invaluable in the NASA investigation.  News reports
tell us that one of the SRB's was headed on a dangerous course toward
popluated areas and had to be destroyed.  Fair enough.  But why destroy
the other one unless and until it was also proved necessary??

Thinking about this further reveals it may not be that simple.  First of
all, I can imagine scenarios in which both SRB's would need to be destroyed
as quickly as possible, especially in the early phases of the launch.  You
would certainly want to have a mechanism for doing this as exists now.
On the other hand, last Tuesday's events show that it would be very
valuable to be able to destroy them individually as well.  This would imply
modifying the hardware/software such that each SRB responded to two destruct
commands: a common one for both and an individual one.  Perhaps a simpler
scheme would be to simply have two different frequencies which could be
used simultaneously or separately.

Those of us discussing this were momentarily satsified until somebody
asked, "Yes, but how do you tell which SRB is which??!"  In this case, it
was reasonably easy to answer that question when they emerged from the 
fireball, but this might not always be the case.  Furthermore, it's not
clear that the task would be any easier when watching them on a radar
screen.  (What does the Range Safety Officer use?)  This difficulty
can presumably be overcome by electronic equipment on each SRB that would
tag its radar image in some fashion.

I'm wondering if this is a case of "good hindsight" or if there are
other considerations we didn't think of.

Clive
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