Path: utzoo!attcan!uunet!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military
From: etnibsd!denbeste@uunet.UU.NET (Steven Den Beste)
Newsgroups: sci.military
Subject: Re: Tomahawk Guidance
Message-ID: <1991Jan24.033834.20114@cbnews.att.com>
Date: 24 Jan 91 03:38:34 GMT
References: <1991Jan22.022338.22603@cbnews.att.com>
Sender: military@cbnews.att.com (William B. Thacker)
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From: etnibsd!denbeste@uunet.UU.NET (Steven Den Beste)

In article <1991Jan22.022338.22603@cbnews.att.com> faubert@cs.mcgill.ca (David FAUBERT) writes:
>
>
>From: faubert@cs.mcgill.ca (David FAUBERT)
>	Does anyone know about the oft mentioned Tomahawk's guidance
>system? I have heard that inertial guidance systems are not used, as
>they are not accurate enough over very long ranges. If the guidance is
>not inertial, what is it? Also, what kind of target recognition, if any,
>is employed by the missile while in flight. Any information would be
>appreciated.

Cruise missile guidance works by recognition of ground features.
Programmed into its guidance system are topological maps of one
or more areas over which it will pass. After a couple hundred miles,
it enters a square which it knows. Its radar then compares where it
is (by matching the shape of the ground against its on-board model)
to where it is supposed to be and corrects its course accordingly.
It then flies blind until it reaches the next area it knows.

There are good sides and bad sides to this design. The missile isn't
depending on any outside control (including sattelites) so it should
be largely immune to ECM. Its radar is pointed down (to see the ground)
and is off most of the time anyway (when between squares) so it doesn't
give itself away.

On the other hand, it requires distinctive geology to fly over so that
it can recognize terrain features to adjust its course. That means that
there are large areas of the Soviet Union which couldn't be reached via
strategic-range cruise missiles because the local geology is simply
flat, or rolling hills. That`s why, back in the good old days of the
Cold War, cruise missiles were not a replacement for ballistic missiles.

It also implies that a substantial amount of effort is required to
program a cruise missile. We're talking weeks, not hours. There simply
isn't any good way to spontaneously retarget a cruise missile to respond
to changing conditions - unless you've captured and stored an appropriate
model of the entire grand-tactical battlefield, which we seem to have
done in the case of Iraq between September and now. The word in Newsweek
this week was that General Schwarzkopf (sp?) insisted on them doing this - and
now it is paying off in spades.