Dec 30, 2020


Admiralty: Shorthand terminology for the Royal Navy’s Board of Admiralty, which heads its central administration. Unlike most such boards, it includes both the civilian political appointees and the professional heads of the fleet.

Air Lock: A watertight compartment through which a diver may pass between a submarine and the sea, pausing within it while the air pressure is equalized with the external environment.

Ballast Tank: A tank that may be filled or emptied of water to increase or decrease a boat’s displacement.

Ballast Tank, Saddle: Ballast tank mounted outside the main structure of the hull, named by analogy with saddlebags.

Bridge: The ship’s navigating and control station.

Bulge: Structures built onto a ship’s side beyond the primary hull structure. Initially these were used to enhance protection against damage from a torpedo hit but they came to be employed more to enhance stability by increasing a hull’s internal volume.

Casing: A light non-pressure-resistant structure designed to improve submarine performance and/or enhance personnel access on the surface.

Catapult: A device for launching aircraft into the air.

Conseil Superieur: The French Navy’s professional leadership.

Conning Tower: Navigation station outside the main hull.

Convoy: A group of merchant vessels traveling together under escort.

Depth Charge: An explosive charge detonated at a preset depth.

Diving Planes: Horizontal control surfaces used to move a submarine in a vertical plane.

Drop-Collar: A mechanical arrangement suspending a torpedo that may be release remotely.

Dynamite Gun: A gun using compressed air as propellant for its missile, which had a dynamite explosive charge.

General Board: The professional leadership of the United States Navy until 1948.


Brake Horsepower (bhp): The measure of the power output of internal combustion engines.

Indicated horsepower (ihp): The measure of the power output of reciprocating steam

Shaft Horsepower (shp): The measure of the power output of turbine engines.

Machinery Types

Diesel: Internal combustion engines using oil fuel and compression ignition.

Triple Expansion: Reciprocating steam engines using multiple cylinders to maximize steam usage.

Turbine: Engines that use the passage of steam or hot gases to rotate encased fan blade assemblies to generate power.

Magazine: Stowage space for munitions.

Mine: An underwater explosive charge.

Monitor: A small shallow draft vessel carrying heavy guns, primarily intended for shore bombardment.

Pressure Hull: The main body of a submarine that is reinforced to withstand water pressure.

Radar: Electronic location equipment, initially for search only but rapidly developed to provide gunnery control and missile guidance.

Radome: A protective enclosure for a radar antenna.

Sail: Streamlined superstructure containing conning stations.

Sheer: The shape of the top of a ship’s hull as viewed from the side.

Sonar: Acoustic detection equipment for locating submarines.

Spar Torpedo: A warhead attached to a pole or spar, allowing it to project ahead of the attacking vessel.

Submarine: A vessel that normally operates submerged. Usually also used to describe any vessel that may operate underwater, even for a limited period.

Submersible: A vessel that normally operates on the surface but may be submerged controllably at will.

Superstructure: All a ship’s structure above the hull’s sheer.

Topweight: The component of the ship’s weight that is above its center of gravity.

Torpedo: Self propelled underwater weapon.

Torpedo, Acoustic: A torpedo that that is self-guided toward the sound of a target’s propellers.

Torpedo, Homing: A torpedo that is self-guided to its target by emissions (usually sonic).

Torpedo, Wire-guided: A torpedo guided to its target by an operator on the launching vessel using signals transmitted through a trailing wire.

Torpedo Pistol, Contact: Torpedo detonator that uses contact with its target for initiation.

Torpedo Pistol, Magnetic: Torpedo detonator that used its target’s magnetic field for initiation.

Torpedo Tube: Tube for launching torpedoes, usually by the pressure of introduced compressed air, a ram, or by allowing the torpedo to exit under its own power (swim-out tube).

Trim Tank: Small tank used for fine adjust of a submarine’s depth and inclination.

Variable Pitch Propeller: A propeller whose blades may be twisted to vary their angle according to power needs.

Warship Types

Battlecruiser: A battleship type that trades armor protection for higher speed.

Corvette: A small low-speed escort vessel.

Cruiser, Armored: A cruising warship type used until the first quarter of the 20th century that depended on an armored belt for its main protection.

Cruiser, Heavy: A cruiser armed with 8-inch guns.

Cruiser, Light: A cruiser armed with 6-inch or smaller guns.

Cruiser, Protected: A cruising warship type used until the first quarter of the 20th century that depended on an armored deck for its main protection.

Destroyer: A relatively small, fast, multi-role warship, originally designed to defend against torpedo boats but later also used for surface torpedo attack and antiaircraft and antisubmarine defense.

Dreadnought: A battleship armed primarily with eight or more very large caliber guns.

Escort Carrier: A small aircraft carrier primarily operating antisubmarine aircraft.

Frigate: A more sophisticated development of a corvette.

Pre-Dreadnought: A battleship usually armed with four large caliber guns and a substantial secondary armament.

Q-ship: A commissioned warship disguised as a merchant vessel carrying concealed weapons used to attack submarines induced to surface.

Sloop: A sophisticated antisubmarine and antiaircraft escort vessel.

Torpedo Boat: A small fast vessel, originally for attack with torpedoes but later often used as a fast antisubmarine vessel.