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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.columbia
Subject: Re: Challenger SRBs
Message-ID: <6339@utzoo.UUCP>
Date: Thu, 30-Jan-86 16:44:36 EST
Article-I.D.: utzoo.6339
Posted: Thu Jan 30 16:44:36 1986
Date-Received: Thu, 30-Jan-86 16:44:36 EST
References: <4270@mhuxd.UUCP>
Organization: U of Toronto Zoology
Lines: 27

> ...reports that at least one of [the SRBs] descended by parachute...
> ... Yet today, NASA said that
> they were destroyed by the range safety officer because one of them
> was headed toward a populated area...

What probably happened is that a fragment of one stayed attached to one
of the chutes, which managed to open.  The destruct system doesn't reduce
them to atoms.

> ...  Am I correct in my understanding that,
> under less catastrophic conditions, the SRBs are capable of
> independent guidance, at least to keep them clear of the orbiter
> after jettisoning following burnout or during an abort?

I believe this is not the case.  They are moved clear of the orbiter
after burnout by smaller solid-fuel rockets that are present specifically
for the purpose, as I recall.  Their control comes entirely from the
orbiter, and in any case after burnout they have little or no independent
maneuverability.

My recollection (which may be wrong) is that there basically is *no* abort
available until SRB burnout, because there is no way to shut them down
(short of destruction) and the jettison system can't safely cut them loose
while the attachment points are carrying millions of pounds of thrust.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry