Friday, August 17, 2012

The Analog Computer & Its Place in History

Before the digital computer, there was the analog computer that would solve important problems that needed to be calculated and solved (perhaps in real time) using mechanical means. These "calculators" were often continuous in nature (unlike most digital computers which are discrete).

Some of the most important inventions of the second world war are in the area of these analog computers. Consider the very secret Norden Bomb Sight, the anti-aircraft fire control director for ships, and the amazing Torpedo Data Computer (of which only one remains in working order today). These are all analog computers that take input from an operator and calculate a continuously updating "fire solution" for the task at hand. In the case of the submarine, this would mean automatically tracking the speed and direction of the submarine, and receiving from the operator a heading to a target. From this, over time, the computer would estimate where the target will be when a torpedo could reach it, and automatically program the torpedos in their tubes to these settings. Its a very difficult trigonometry problem and it used to be done by hand by the capitain and his XO in the course of the attack.

Ben Clymer of MIT has written a paper on the history, significance, and contributors to this field. Although its day has passed, I promise you this is worth knowing something about. It was really very important in its day.

The paper by Ben Clymer is at

The manual for the Torpedo Data Computer is at:

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