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From: cga66@ihlpy.att.com (Patrick V Kauffold)
Newsgroups: sci.military
Subject: Re: WWII Submarine Navigation and Attack Terminology
Message-ID: <1990Sep29.155343.7943@cbnews.att.com>
Date: 29 Sep 90 15:53:43 GMT
References: <1990Sep26.024624.26984@cbnews.att.com>
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Organization: AT&T Bell Laboratories
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From: cga66@ihlpy.att.com (Patrick V Kauffold)
>From article <1990Sep26.024624.26984@cbnews.att.com>, by jabishop@uokmax.ecn.uoknor.edu (Jonathan A Bishop):
> 
> ... The TDC's on WWII
> subs were analog computers which automatically calculated this lead angle
> and transmitted it to the torpedo fire control system.  

The TDC was a _mechanical_ analog computer - no electronics (to speak of).
The mechanism included high-precision integrators and some other very
nifty and clever devices to solve differential equations.  You can see
examples of a TDC at the sub base in Groton, CT in their museum, along
with the guidance mechanism for the torpedoes.

The manual solution was done on the "maneuvering board" using some basic
vector graphics.  This same device is still used for radar navigation
and multi-ship formations.

A related device was the lead-computing AA gunsights and fire control
equipment which appeared toward the end of the war in the Pacific on
20MM, 40MM and 5" dual-purpose guns.

Surface ships also had a device called the "dead reckoning tracer" which
moved a "bug" under an illuminated frosted glass table according 
to ship' heading and speed inputs from the gyro compass and static log.
The plotter would make a dot on a paper (or chart) periodically to plot
the ship's "true" motion, and also plot range/bearing points of the
target being tracked, so you would have a "bird's eye view" on the DRT
as well as a relative view on the maneuvering board or radar/sonar plot.
(Don't know if these were on subs or not).

Pat Kauffold AT&T Bell Labs