Rangekeepers were electromechanical fire control computers used primarily during the early part of the 20th century. They were sophisticated analog computers whose development reached its zenith following World War II, specifically the Computer Mk 47 in the Mk 68 Gun Fire Control system. During World War II, rangekeepers directed gunfire on land, sea, and in the air. While rangekeepers were widely deployed, the most sophisticated rangekeepers were mounted on warships to direct the fire of long-range guns.
Figure 1: The Ford Mk 1 Ballistic Computer. The name "rangekeeper" began to become inadequate to describe the increasingly complicated functions of rangekeeper. The Mk 1 Ballistic Computer was the first rangekeeper that was referred to as a computer. Note the three pistol grips in the foreground, which are the firing keys of the main guns. The left sounds an alarm that the guns are about to fire, the center fires in automatic mode (Range Keeper controlled), and right is manual firing.
A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more accurately.
A German anti-aircraft 88 mm Flak gun with its fire-control computer from World War II. Displayed in the Canadian War Museum.
Admiralty Fire Control Table in the transmitting station of HMS Belfast.
Ford Mk 1 Ballistic Computer. The name rangekeeper began to become inadequate to describe the increasingly complicated functions of rangekeeper. The Mk 1 Ballistic Computer was the first rangekeeper that was referred to as a computer. Note the three pistol grips in the foreground. Those fired the ship's guns.
Accurate fire control systems were introduced in the early 20th century. Pictured, a cut-away view of a destroyer. The below deck analog computer is shown in the centre of the drawing and is labelled "Gunnery Calculating Position".