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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.columbia
Subject: Re: SRB's
Message-ID: <6435@utzoo.UUCP>
Date: Wed, 26-Feb-86 13:44:36 EST
Article-I.D.: utzoo.6435
Posted: Wed Feb 26 13:44:36 1986
Date-Received: Wed, 26-Feb-86 13:44:36 EST
References: <699@ihwpt.UUCP> <345@quest.UUCP>, <3311@hplabsb.UUCP>
Organization: U of Toronto Zoology
Lines: 16

> That may happen eventually, but not right away.  The launch vehicle is held
> down to the pad until all engines are ignited.  The three main liquid engines
> are ignited first, then the SRBs.  If one did not ignite, I suspect the
> procedure is to shut down the main engines and not release the vehicle...

Alas, not so.  I thought so too, but on looking it up in the Space Shuttle
News Reference (available from NSI), it turns out that SRB ignition and the
blowing of the hold-down nuts are simultaneous.

It is very unlikely that one SRB would quietly fail to ignite.  They are
ignited by a substantial rocket motor up in the top of the SRB firing down
into the center hole; this is pretty positive ignition!	 The actual ignition
system that ultimately gets things going is multiply redundant.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry