Fire-control system

• 1. Naval Fire Control Origins

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  In 1800, most naval engagements occurred at ranges so short that gunners could see their targets clearly. The American Civil War saw the famous battle between the USS Monitor and CSS Virginia take place at distances under one thousand yards. Rapid technical improvements in the late nineteenth century changed this reality forever. Rifled guns fired explosive shells lighter than all-metal balls but with much greater range. These new weapons grew to calibers exceeding twelve inches by the 1890s. The primary limitation became seeing the target while the ship moved on rolling waves. Engineers solved this problem by introducing the gyroscope to correct motion and provide sub-degree accuracies. Steam turbines replaced reciprocating engines, increasing ship speeds from sixteen knots to over twenty knots. A target moving several ship lengths away during shell flight time made eyeballing aim impossible. Naval fire control evolved through three levels of complexity: local control, director control, and coordinated gunfire from fleet formations. Corrections for surface wind velocity, firing ship roll, pitch, powder magazine temperature, and drift of rifled projectiles fed into a central computer. Observers worked out how far rounds missed and fed that information back to adjust future shots. Artillery spotting involved firing a gun, observing the projectile's point of impact, and correcting aim based on where the shell landed. High masts allowed optical rangefinders and spotters to see the battle. Manned observation balloons launched from ships helped spot naval gunfire points of impact. Between 1865 and 1905, telescopic sights and optical rangefinders improved accuracy. Plotting boards manually predicted ship positions during engagements. Mechanical calculators like the Dreyer Table and Argo Clock began appearing around 1905. Arthur Pollen developed a plotting unit to capture target data after noting poor artillery accuracy near Malta in 1900. Lord Kelvin proposed using an analog computer to solve equations arising from relative motion between ships. Trials in 1905 and 1906 showed promise despite initial failures. Admiral Jackie Fisher and Director John Jellicoe encouraged Pollen's work. Frederic Charles Dreyer designed a similar system that eventually found favor with the Royal Navy. By mid-1916, most British capital ships carried director control systems. The Admiralty Fire Control Table replaced earlier designs for ships built after 1927.

• 2. World War II Technological Shifts

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  Radar integration into fire-control systems early in World War II enabled effective long-range operations in poor weather or darkness. The US Navy used servomechanisms to automatically steer guns in both azimuth and elevation. German systems steered guns only in elevation while Britain introduced Remote Power Control for four-inch, four-and-a-half-inch, and five-and-a-quarter-inch guns starting in 1942. The battleship HMS Belfast displayed its Admiralty Fire Control Table in transmitting stations during the war. Gun directors sat high on superstructures where operators enjoyed superior views above gunlayers in turrets. These elevated positions coordinated turret fire so combined shots worked together. Dispersion caused by differences in individual guns, projectiles, powder ignition sequences, and transient ship structure distortion became undesirably large at typical engagement ranges. Visual range measurement proved difficult before radar availability. British forces favored coincidence rangefinders while Germans preferred stereoscopic types. The Ford Mk 1 Ballistic Computer marked the first instance when rangekeepers were called computers. Submarines equipped with torpedo data computers calculated proper lead given relative vessel motion since torpedoes took one to two minutes to reach targets. A typical British ship connected individual gun turrets to a director tower housing sighting instruments and an analog computer heart of the vessel. Operators trained telescopes on targets; one measured elevation, another bearing. Rangefinder telescopes on separate mountings measured distance to target. Measurements converted by the Fire Control Table into bearings and elevations for firing. In turrets, gunlayers adjusted elevation to match indicators transmitted from the table. When guns aligned correctly, they fired centrally. The Transmitting Station for HMS Hood's main guns housed twenty-seven crew members. Directors remained largely unprotected from enemy fire due to weight constraints placing armor high on ships. Night naval engagements at long range became feasible when radar data entered rangekeepers. The Third Battle of Savo Island in November 1942 demonstrated this effectiveness when USS Washington engaged Japanese battleship Kirishima at night. Kirishima suffered explosions and was scuttled after receiving nine hits out of seventy-five rounds fired. This twelve percent hit rate proved devastating. The wreck discovered in 1992 showed the entire bow section missing. Japanese forces lacked radar or automated fire control development levels matching US Navy capabilities. By the 1950s, gun turrets increasingly operated unmanned with remote laying controlled from ship centers using radar inputs.

• 3. Aircraft Bombing Systems Evolution

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  Early bomber aircraft utilized computing bombsights accepting altitude and airspeed information to predict bomb impact points. The Norden bombsight represented the best-known United States device during World War II. Simple lead computing sights appeared inside aircraft late in the war as gyro gunsights. These devices measured turn rates using gyroscopes and moved aim-points accordingly through reflector sights. Manual input required dialing target wing span size at known ranges. Small radar units added post-war period automation but took time to satisfy pilots. The B-29 marked the first centralized fire-control system implementation on a production aircraft. Low Altitude Bombing System integration began by Vietnam War start dates for nuclear-capable aircraft. This computerized bombing predictor revolutionized operations because release commands came from computers rather than pilots. Pilots designated targets via radar or targeting systems then consented to weapon release. Computers calculated precise release points seconds later allowing accurate drops even while planes maneuvered. Previous systems required constant plane attitude usually level though dive-bombing sights existed commonly. LABS originally facilitated toss bombing tactics keeping aircraft outside weapon blast radius ranges. Calculated release point principles eventually integrated into fire control computers of later bombers and strike aircraft enabling level, dive, and toss bombing capabilities. Fire control computers interfaced with ordnance systems taking flight characteristics of weapons launched into account. Modern digital fire-control computers handle inputs ranging from air density and wind to barrel wear and heating distortion effects. Tanks automated gun laying using laser rangefinders and barrel-distortion meters early in this evolution. Fire-control computers now appear on smaller platforms including machine guns, small cannons, guided missiles, rifles, grenades, and rockets. Some grenade launchers developed for Fabrique Nationale F2000 bullpup assault rifles incorporate these systems. Technology progressed through analog stages vacuum tubes transistors replacing earlier designs.

• 4. Anti-Aircraft Defense Innovations

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  By World War II start dates, aircraft altitude performance increased so much that anti-aircraft guns faced similar predictive problems. Early High Angle Control System versions of Britain's Royal Navy predicted based on assumptions target speed direction and altitude remained constant during prediction cycles. USN Mk 37 systems made similar assumptions except predicting constant rate of altitude change. Kerrison Predictor solved laying in real time by pointing directors at targets then aiming guns at pointers they directed. Deliberately designed small and light, it allowed easy movement along with served guns. The radar-based M-9/SCR-584 Anti-Aircraft System directed air defense artillery since 1943. MIT Radiation Lab's SCR-584 became the first radar system with automatic following capabilities. Bell Laboratory's M-9 electronic analog fire-control computer replaced complicated mechanical computers like Sperry M-7 or British Kerrison predictors. Combined with VT proximity fuzes, this system accomplished shooting down V-1 cruise missiles using fewer than one hundred shells per plane. Thousands typically required in earlier anti-aircraft systems. This achievement proved instrumental defending London and Antwerp against V-1 attacks. Although listed under land-based sections, anti-aircraft fire control systems also appeared on naval and aircraft platforms. Coast Artillery forts bristled with armament ranging from twelve-inch coast defense mortars through three-inch and six-inch mid-range artillery to larger fourteen-inch railroad artillery and sixteen-inch cannon installed prior to and up through World War II. Fire control in Coast Artillery became sophisticated correcting firing data for weather conditions powder condition Earth rotation factors. Provisions adjusted firing data for observed shell fall of shots fed back to plotting rooms on finely tuned schedules controlled by time interval bells ringing throughout harbor defense systems. Electro-mechanical gun data computers connected to coast defense radars began replacing optical observation manual plotting methods controlling coast artillery only later in World War II. Manual methods retained as backups through war end.

• 5. Coastal Defense Plotting Boards

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  United States Army Coast Artillery Corps developed fire control systems beginning late nineteenth century progressing through World War II. Early systems used multiple observation or base end stations finding tracking targets attacking American harbors. Data passed to plotting rooms where analog mechanical devices like plotting boards estimated target positions deriving firing data for coastal gun batteries assigned interdicting them. Figure 2 diagrams conceptual flow showing forward point target generated using plotting board then corrected for range azimuth affecting factors finally adjusted for actual shell fall observations sending new firing data to guns. U.S. Coast Artillery forts bristled with variety armament including twelve-inch coast defense mortars three-inch six-inch mid-range artillery ten-inch twelve-inch barbette disappearing carriage guns fourteen-inch railroad artillery sixteen-inch cannon installed prior and up through World War II. Fire control became sophisticated correcting firing data weather conditions powder condition Earth rotation factors. Provisions adjusted firing data observed shell fall of shots fed back plotting rooms finely tuned schedule controlled system time interval bells rang throughout each harbor defense system. Only later in World War II electro-mechanical gun data computers connected coast defense radars began replacing optical observation manual plotting methods controlling coast artillery. Even then manual methods retained backup through war end. Modern digital fire-control computers handle inputs ranging air density wind barrel wear heating distortion effects noticeable any sort gun. Fire-control computers started appearing smaller platforms tanks one early use automated gun laying laser rangefinder barrel-distortion meter. Fire-control computers useful aiming large cannons machine guns small cannons guided missiles rifles grenades rockets kind weapon launch firing parameters varied. Typically installed ships submarines aircraft tanks even some small arms grenade launcher developed Fabrique Nationale F2000 bullpup assault rifle.

• 6. Modern Digital Integration

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  Modern fire-control computers function as high-performance digital machines handling virtually any input from air density wind to barrel wear heating distortion effects. These effects noticeable any sort gun fire-control computers started appearing smaller platforms tanks one early use automated gun laying laser rangefinder barrel-distortion meter. Fire-control computers useful aiming large cannons machine guns small cannons guided missiles rifles grenades rockets kind weapon launch firing parameters varied. Typically installed ships submarines aircraft tanks even some small arms grenade launcher developed Fabrique Nationale F2000 bullpup assault rifle. Technology progressed analog stages vacuum tubes transistors replacing earlier designs. Fire-control systems often interfaced sensors sonar radar infra-red search track laser range-finders anemometers wind vanes thermometers barometers cut down eliminate information manually entered calculate effective solution. Sonar radar IRST range-finders give system direction distance target alternatively optical sight provided operator point target easier inputting range using methods giving target less warning tracked. Weapons fired long ranges need environmental information farther munition travels more wind temperature air density affect trajectory accurate information essential good solution. Sometimes very long-range rockets environmental data obtained high altitudes between launching point target satellites balloons used gather information. Once firing solution calculated many modern fire-control systems aim fire weapons interest speed accuracy vehicle like aircraft tank allow pilot gunner perform other actions simultaneously tracking target flying aircraft. Even if system unable aim weapon itself fixed cannon aircraft able give operator cues how aim. Typically cannon points straight ahead pilot maneuver aircraft oriented correctly before firing. In most aircraft aiming cue takes form pipper projected heads-up display shows pilot where target must be relative aircraft hit it. Pilot maneuvers aircraft so target pipper superimposed fires weapon or on some aircraft weapon fires automatically overcome delay pilot. Case missile launch fire-control computer may give pilot feedback whether target in range missile likely hit launched particular moment. Pilot waits until probability reading satisfactorily high before launching weapon.