Rangekeeper
More info
- Creator
- Hannibal Ford, Ford Instrument Company
- Released
- 1916
- Type
- Analog fire-control computer
- Owner
- US Navy
The US Navy's mechanical fire-control computer, which from 1916 solved gunnery's founding problem: where the ship will be by the time the shell gets there.
A shell from a 16-inch gun spends close to a minute in the air. In that time a target making 30 knots travels a kilometre, and the firing ship travels as far in some other direction. The rangekeeper tracked both courses continuously and integrated them forward in time, so the turrets could be laid on a point where nothing yet existed.
The arithmetic was done in gears, cams and Hannibal Ford's disc-ball-roller integrator, a mechanism that integrates by letting a ball roll against a spinning disc. Results went to the turrets as electrical angles over synchros. The Mark 8 of the 1930s was tied into fire-control radar and served throughout the Second World War — on the night of 15 November 1942, USS Washington used one to take apart the battlecruiser Kirishima in darkness, with nobody aboard ever seeing the target by eye.