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Ships in combat usually pursue zigzag courses in order to make enemy aiming dif-
ficult. Therefore, naval gunnery deals with aiming massive projectiles over very
long ranges and involves both a moving gun platform and a moving target. These
are not trivial calculations and they cannot be performed manually with anything
like the speed and accuracy required.
Prior to the development of analog fire-control computers, almost 400 shots
were needed to ensure one hit at ranges of more than three miles. Analog fire-con-
trol computers reduced the number of shots down to perhaps 40 shots per hit.
Not only is surface gunnery a task requiring many computations but also
launching torpedoes from submarines requires a great many complex calculations
that need high-speed computing. Most of the belligerents used fairly effective
torpedo-launch analog computers during World War II.
These analog computer torpedo-aiming devices were quite large for submar-
ines: Some were five or six feet tall and perhaps two feet wide and deep. The
urgency of the torpedo-aiming challenge explains why such big machines were
squeezed into the very small control rooms of World War II submarines. They also
required two extra crew members to keep them up and running.
Even more difficult than naval gunnery is the task of shooting antiaircraft guns
against enemy planes. Not only are the planes moving much faster than ships at
sea, but they can also move in three dimensions and can change directions rapidly.
Thus, antiaircraft calculations involve altitude, direction, velocity, wind speed,
wind direction, and rates of change in any or all of these factors. The essential
problem is hitting a very small target that might be traveling an erratic course at
more than 350 miles per hour at an altitude of more than 25,000 feet. This is not a
trivial set of calculations.
As anyone who has tried skeet shooting knows, the shell must be aimed at
where it will be when it arrives, not where the shell is currently located. For air-
planes, the radius of destruction from World War II explosive antiaircraft cannon
shells was only about 30 feet, which meant that the shells had to be very close to
the target to be successful.
Equally challenging and requiring sophisticated calculations is the aiming of
bombs from moving aircraft. All of the belligerents developed analog computers
for bombsights, with probably the most famous being the American Norden bomb-
sight, to be discussed later in this chapter.
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