Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.columbia
Subject: Re: Challenger SRBs
Message-ID: <6347@utzoo.UUCP>
Date: Mon, 3-Feb-86 17:15:30 EST
Article-I.D.: utzoo.6347
Posted: Mon Feb  3 17:15:30 1986
Date-Received: Mon, 3-Feb-86 17:15:30 EST
References: <4270@mhuxd.UUCP> <437@umich.UUCP>, <121@ucdavis.UUCP>
Organization: U of Toronto Zoology
Lines: 15

> > I would be surprised if the SRBs were capable of independent guidance.
> > They have no control surfaces, and I doubt the SRB nozzles are on gimbals
> > like those of the main engines.
>           I agree. It would seem the three main engines would exert
> enough control.

Unfortunately, they don't; that is precisely the problem.  NASA would have
liked to avoid the complexity of having gimbaled nozzles in the SRBs, but
it wasn't avoidable.  The SRBs give most of the launch thrust for the shuttle,
and the main engines have only a limited gimbal range.  It turns out that
the main engines cannot exert enough side thrust for adequate control while
the SRBs are burning.  So the SRBs have nozzle gimbals.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry