Mark I Fire Control Computer
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The Mark 1, and later the Mark 1A, Fire Control Computer was a component of the Mark 37 Gun Fire Control System deployed by the
United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
during
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
and up to 1991 and possibly later. It was originally developed by Hannibal C. Ford of the Ford Instrument Company and William Newell. It was used on a variety of ships, ranging from
destroyer In naval terminology, a destroyer is a fast, maneuverable, long-endurance warship intended to escort larger vessels in a fleet, convoy, or carrier battle group and defend them against a wide range of general threats. They were conceived i ...
s (one per ship) to
battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...
s (four per ship). The Mark 37 system used
tachymetric A tachymetric anti-aircraft fire control system generates target position, speed, direction, and rate of target range change, by computing these parameters directly from measured data. The target's range, height and observed bearing data are fed in ...
target motion prediction to compute a fire control solution. It contained a target simulator which was updated by further target tracking until it matched. Weighing more than , the Mark 1 itself was installed in the plotting room, a watertight compartment that was located deep inside the ship's hull to provide as much protection against
battle damage A battle is an occurrence of combat in warfare between opposing military units of any number or size. A war usually consists of multiple battles. In general, a battle is a military engagement that is well defined in duration, area, and force c ...
as possible. Essentially an
electromechanical Electromechanics combine processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focus on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each ...
analog computer An analog computer or analogue computer is a type of computation machine (computer) that uses physical phenomena such as Electrical network, electrical, Mechanics, mechanical, or Hydraulics, hydraulic quantities behaving according to the math ...
, the Mark 1 was electrically linked to the gun mounts and the Mark 37
gun director A director, also called an auxiliary predictor, is a mechanical or electronic computer that continuously calculates trigonometric firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew. N ...
, the latter mounted as high on the superstructure as possible to afford maximum visual and radar range. The gun director was equipped with both optical and radar range finding, and was able to rotate on a small
barbette Barbettes are several types of gun emplacement in terrestrial fortifications or on naval ships. In recent naval usage, a barbette is a protective circular armour support for a heavy gun turret. This evolved from earlier forms of gun protection ...
-like structure. Using the range finders and telescopes for bearing and elevation, the director was able to produce a continuously varying set of outputs, referred to as line-of-sight (LOS) data, that were electrically relayed to the Mark 1 via synchro motors. The LOS data provided the target's present range, bearing, and in the case of aerial targets, altitude. Additional inputs to the Mark 1A were continuously generated from the stable element, a
gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...
device that reacted to the roll and pitch of the ship, the pitometer log, which measured the ship's speed through the water, and an
anemometer In meteorology, an anemometer () is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti ...
, which provided wind speed and direction. The Stable Element would now be called a vertical gyro. In "Plot" (the plotting room), a team of
sailor A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor'' ...
s stood around the Mark 1 and continuously monitored its operation. They would also be responsible for calculating and entering the average
muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...
of the
projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...
s to be fired before action started. This calculation was based on the type of
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...
to be used and its temperature, the projectile type and weight, and the number of rounds fired through the guns to date. Given these inputs, the Mark 1 automatically computed the lead angles to the future position of the target at the end of the projectile's time of flight, adding in corrections for gravity, relative wind, the
magnus effect The Magnus effect is a phenomenon that occurs when a spin (geometry), spinning Object (physics), object is moving through a fluid. A lift (force), lift force acts on the spinning object and its path may be deflected in a manner not present when ...
of the spinning projectile, and
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
, the latter compensation necessary because the guns themselves were widely displaced along the length of the ship. Lead angles and corrections were added to the LOS data to generate the line-of-fire (LOF) data. The LOF data, bearing and elevation, as well as the projectile's fuze time, was sent to the mounts by synchro motors, whose motion actuated hydraulic servos with excellent dynamic accuracy to aim the guns. Once the system was "locked" on the target, it produced a continuous fire control solution. While these fire control systems greatly improved the long-range accuracy of ship-to-ship and ship-to-shore gunfire, especially on
heavy cruiser A heavy cruiser was a type of cruiser, a naval warship designed for long range and high speed, armed generally with naval guns of roughly 203 mm (8 inches) in calibre, whose design parameters were dictated by the Washington Naval Treat ...
s and battleships, it was in the
anti-aircraft warfare Anti-aircraft warfare (AAW) is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It encompasses surface-based, subsurface (Submarine#Armament, submarine-lau ...
mode that the Mark 1 made the greatest contribution. However, the anti-aircraft value of analog computers such as the Mark 1 was greatly reduced with the introduction of
jet aircraft A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by one or more jet engines. Whereas the engines in Propeller (aircraft), propeller-powered aircraft generally achieve their maximum efficiency at much ...
, where the
relative motion In geometry, a position or position vector, also known as location vector or radius vector, is a Euclidean vector that represents a point ''P'' in space. Its length represents the distance in relation to an arbitrary reference origin ''O'', and ...
of the target became such that the computer's mechanism could not react quickly enough to produce accurate results. Furthermore, the target speed, originally limited to 300 knots by a mechanical stop, was twice doubled to 600, then 1,200 knots by gear ratio changes. The design of the postwar Mark 1A may have been influenced by the Bell Labs Mark 8, which was developed as an all electrical computer, incorporating technology from the M9
gun data computer The gun data computer was a series of artillery computers used by the U.S. Army for coastal artillery, field artillery and anti-aircraft artillery applications. For antiaircraft applications they were used in conjunction with a director compu ...
as a safeguard to ensure adequate supplies of fire control computers for the USN during WW2.Annals of the History of Computing, Volume 4, Number 3, July 1982 ''Electrical Computers for Fire Control'', p218-46 W. H. C. Higgins, B. D. Holbrook, and J. W. Emling "...The development model of the Mark 8 (Figures 9 and 10) was delivered to the Naval Research Laboratory Annex at North Beach, Maryland, on February 15, 1944, whereupon extensive comparison tests of it and the Mark 1 were made, using both the Mark 37 and the Bell Labs Mark 7 radar as tracking devices. These tests were primarily photo-data runs, with actual aircraft (usually executing ordered manoeuvres) as targets; firing tests were not practicable at North Beach. These tests indicated that the two machines were comparable in the accuracy of the gun orders delivered, except in regions where mathematical approximations inherent in the design of the Mark1 sometimes resulted in substantial errors. (The Markx8 geometry was substantially free of such errors.) It was also found that the Mark 8 reached solution much faster than the Mark 1. Since one of the drawbacks observed in fleet experience with the Mark 1 was its sluggishness, it was decided to attempt to modify the Mark 1 in accordance with the principles of the Mark 8 to obtain a faster solution time..." p232 Surviving Mark 1 computers were upgraded to the Mark 1A standard after World War II ended. Among the upgrades were removing the vector solver from the Mark 1 and redesigning the reverse coordinate conversion scheme that updated target parameters. The scheme kept the four component integrators, obscure devices not included in explanations of basic fire control mechanisms. They worked like a ball–type computer mouse, but had shaft inputs to rotate the ball and to determine the angle of its axis of rotation. The round target course indicator on the right side of the star shell computer with the two panic buttons is a holdover from WW II days when early tracking data and initial angle–output position of the vector solver caused target speed to decrease. Pushbuttons slewed the vector solver quickly.


See also

*
Ship gun fire-control system Ship gun fire-control systems (GFCS) are analogue fire-control systems that were used aboard naval warships prior to modern electronic computerized systems, to control targeting of guns against surface ships, aircraft, and shore targets, with e ...
* Admiralty Fire Control Table *
High Angle Control System High Angle Control System (HACS) was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 and used widely during World War II. HACS calculated the necessary Deflection (ballistics), deflection required to place an ex ...
*
Gun data computer The gun data computer was a series of artillery computers used by the U.S. Army for coastal artillery, field artillery and anti-aircraft artillery applications. For antiaircraft applications they were used in conjunction with a director compu ...
*
Stabilisierter Leitstand A Stabilisierter Leitstand (), abbreviated SL, was a Ship gun fire-control system, fire control element in German World War II era shipborne heavy anti-aircraft defense. One to four SL's were installed on all capital ships of the Kriegsmarine. A Sta ...


References


External links


Fire Control Fundamentals








* ttp://www.navsource.org/archives/01/57o.htm Director section of Mark 1 Mod 1 computer operations at NavSource.org
Naval Ordnance and Gunnery, Vol. 2, Chapter 25, AA Fire Control Systems
{{Naval combat systems Artillery operation Mechanical computers Military computers Fire-control computers of World War II Military equipment introduced in the 1930s