Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: SRB question
Message-ID: <1989Jan15.051404.15350@utzoo.uucp>
Organization: U of Toronto Zoology
References: <20600@ames.arc.nasa.gov> <7089@csli.STANFORD.EDU>
Date: Sun, 15 Jan 89 05:14:04 GMT

In article <7089@csli.STANFORD.EDU> jkl@csli.UUCP (John Kallen) writes:
>I've been wondering about what would happen if, when launched, one of
>the SRB's on the shuttle fires, say, a second before the other one
>does. What prevents the whole orbiter assembly from somersaulting?

Nothing.  This is known as an "unsurvivable accident".

>Also, does anybody know if the SRB's *do* fire asynchronously? What
>are the safety precautions used to prevent the assmebly from spinning
>out of control due to thrust mismatches?

The two SRBs are matched fairly carefully, including using motor segments
from the same production batch.  Minor imbalances can be handled using
the normal steering systems, and indeed are to be expected.  Considerable
pains are taken to make ignition very reliable and to make it happen
exactly simultaneously.
-- 
"God willing, we will return." |     Henry Spencer at U of Toronto Zoology
-Eugene Cernan, the Moon, 1972 | uunet!attcan!utzoo!henry henry@zoo.toronto.edu