Misplaced Pages

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93-453: For warships of the 20th century, the director is part of the fire control system ; it passes information to the computer that calculates range and elevation for the guns. Typically, positions on the ship measured range and bearing of the target; these instantaneous measurements are used to calculate rate of change values, and the computer ("fire control table" in Royal Navy terms) then predicts

186-528: A Mark 4 fire-control radar added to the roof of the director, while others had a Mark 4 radar added over the open director. With the Mark 4 large aircraft at up to 40,000 yards could be targeted. It had less range against low-flying aircraft, and large surface ships had to be within 30,000 yards. With radar, targets could be seen and hit accurately at night, and through weather. The Mark 33 and 37 systems used tachymetric target motion prediction. The USN never considered

279-547: A car, about 3,125 pounds (1,417 kg), with the Star Shell Computer Mark 1 adding another 215 pounds (98 kg). It used 115 volts AC, 60 Hz, single phase, and typically a few amperes or even less. Under worst-case fault conditions, its synchros apparently could draw as much as 140 amperes, or 15,000 watts (about the same as 3 houses while using ovens). Almost all of the computer's inputs and outputs were by synchro torque transmitters and receivers. Its function

372-556: A computer, stabilizing device or gyro, and equipment in a plotting room. For the US Navy, the most prevalent gunnery computer was the Ford Mark 1, later the Mark 1A Fire Control Computer , which was an electro-mechanical analog ballistic computer that provided accurate firing solutions and could automatically control one or more gun mounts against stationary or moving targets on the surface or in

465-478: A density of approximately 1.204 kg/m (0.0752 lb/cu ft), according to the International Standard Atmosphere (ISA). At 101.325   kPa (abs) and 15 °C (59 °F), air has a density of approximately 1.225  kg/m (0.0765  lb/cu ft ), which is about 1 ⁄ 800 that of water , according to the International Standard Atmosphere (ISA). Pure liquid water

558-419: A local control option for use when battle damage prevented the director setting the guns. Guns could then be fired in planned salvos, with each gun giving a slightly different trajectory. Dispersion of shot caused by differences in individual guns, individual projectiles, powder ignition sequences, and transient distortion of ship structure was undesirably large at typical naval engagement ranges. Directors high on

651-473: A main armament of one size of gun across a number of turrets (which made corrections simpler still), facilitating central fire control via electric triggering. The UK built their first central system before the Great War. At the heart was an analogue computer designed by Commander (later Admiral Sir) Frederic Charles Dreyer that calculated range rate, the rate of change of range due to the relative motion between

744-460: A mechanism in part like that of a traditional computer mouse, converted the received corrections into target motion vector values. The Mark 1 computer attempted to do the coordinate conversion (in part) with a rectangular-to polar converter, but that didn't work as well as desired (sometimes trying to make target speed negative!). Part of the design changes that defined the Mark 1A were a re-thinking of how to best use these special coordinate converters;

837-459: A new target. Up to four Mark 37 Gun Fire Control Systems were installed on battleships. On a battleship, the director was protected by 1 + 1 ⁄ 2 inches (38 mm) of armor, and weighs 21 tons. The Mark 37 director aboard USS  Joseph P. Kennedy, Jr. is protected with one-half inch (13 mm) of armor plate and weighs 16 tons. Stabilizing signals from the Stable Element kept

930-638: A potential adversary through The Great Game , and sent Lieutenant Walter Lake of the Navy Gunnery Division and Commander Walter Hugh Thring of the Coastguard and Reserves, the latter with an early example of Dumaresq , to Japan during the Russo-Japanese War . Their mission was to guide and train the Japanese naval gunnery personnel in the latest technological developments, but more importantly for

1023-628: A role in Center Force's battleships' dismal performance in the Battle off Samar in October 1944. In that action, American destroyers pitted against the world's largest armored battleships and cruisers dodged shells for long enough to close to within torpedo firing range, while lobbing hundreds of accurate automatically aimed 5-inch (127 mm) rounds on target. Cruisers did not land hits on splash-chasing escort carriers until after an hour of pursuit had reduced

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1116-557: A separate plotting room as in the RN HACS, or the later Mark 37 GFCS, and this made it difficult to upgrade the Mark 33 GFCS. It could compute firing solutions for targets moving at up to 320 knots, or 400 knots in a dive. Its installations started in the late 1930s on destroyers, cruisers and aircraft carriers with two Mark 33 directors mounted fore and aft of the island. They had no fire-control radar initially, and were aimed only by sight. After 1942, some of these directors were enclosed and had

1209-513: A solution on a target even during maneuvers. By the start of World War II British, German and American warships could both shoot and maneuver using sophisticated analog fire-control computers that incorporated gyro compass and gyro Level inputs. In the Battle of Cape Matapan the British Mediterranean Fleet using radar ambushed and mauled an Italian fleet, although actual fire was under optical control using starshell illumination. At

1302-673: A straight-line path at a constant speed, to keep complexity to acceptable limits. A sonar rangekeeper was built to include a target circling at a constant radius of turn, but that function had been disabled. Only the RN and USN achieved 'blindfire' radar fire-control, with no need to visually acquire the opposing vessel. The Axis powers all lacked this capability. Classes such as Iowa and South Dakota battleships could lob shells over visual horizon, in darkness, through smoke or weather. American systems, in common with many contemporary major navies, had gyroscopic stable vertical elements, so they could keep

1395-447: Is 1,000 kg/m (62 lb/cu ft). Air density is a property used in many branches of science, engineering, and industry, including aeronautics ; gravimetric analysis ; the air-conditioning industry; atmospheric research and meteorology ; agricultural engineering (modeling and tracking of Soil-Vegetation-Atmosphere-Transfer (SVAT) models); and the engineering community that deals with compressed air. Depending on

1488-418: Is 75%, while for oxygen this is 79%, and for carbon dioxide, 88%. Higher than the troposphere, at the tropopause , the temperature is approximately constant with altitude (up to ~20   km) and is 220   K. This means that at this layer L = 0 and T = 220 K , so that the exponential drop is faster, with H TP = 6.3 km for air (6.5 for nitrogen, 5.7 for oxygen and 4.2 for carbon dioxide). Both

1581-788: Is approximately constant with altitude in the atmosphere, the pressure at height h is proportional to the integral of the density in the column above h , and therefore to the mass in the atmosphere above height h . Therefore, the mass fraction of the troposphere out of all the atmosphere is given using the approximated formula for p : 1 − p ( h = 11  km ) p 0 = 1 − ( T ( 11  km ) T 0 ) g M R L ≈ 76 % {\displaystyle 1-{\frac {p(h=11{\text{ km}})}{p_{0}}}=1-\left({\frac {T(11{\text{ km}})}{T_{0}}}\right)^{\frac {gM}{RL}}\approx 76\%} For nitrogen, it

1674-432: Is constant for a particular volume (see Avogadro's Law ). So when water molecules (water vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure from increasing or temperature from decreasing. Hence the mass per unit volume of the gas (its density) decreases. The density of humid air may be calculated by treating it as a mixture of ideal gases . In this case,

1767-410: Is for the Mark 12 FC radar, and the parabolic antenna on the left ("orange peel") is for the Mark 22 FC radar. They were part of an upgrade to improve tracking of aircraft. The director was manned by a crew of 6: Director Officer, Assistant Control Officer, Pointer, Trainer, Range Finder Operator and Radar Operator. The Director Officer also had a slew sight used to quickly point the director towards

1860-426: Is found considering partial pressure , resulting in: p d = p − p v {\displaystyle p_{\text{d}}=p-p_{\text{v}}} where p {\displaystyle p} simply denotes the observed absolute pressure . To calculate the density of air as a function of altitude, one requires additional parameters. For the troposphere, the lowest part (~10 km) of

1953-942: Is given by: p = p 0 ( 1 − L h T 0 ) g M R L {\displaystyle p=p_{0}\left(1-{\frac {Lh}{T_{0}}}\right)^{\frac {gM}{RL}}} Density can then be calculated according to a molar form of the ideal gas law : ρ = p M R T = p M R T 0 ( 1 − L h T 0 ) = p 0 M R T 0 ( 1 − L h T 0 ) g M R L − 1 {\displaystyle \rho ={\frac {pM}{RT}}={\frac {pM}{RT_{0}\left(1-{\frac {Lh}{T_{0}}}\right)}}={\frac {p_{0}M}{RT_{0}}}\left(1-{\frac {Lh}{T_{0}}}\right)^{{\frac {gM}{RL}}-1}} where: Note that

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2046-552: Is identical to the isothermal solution, except that H n , the height scale of the exponential fall for density (as well as for number density n), is not equal to RT 0 / gM as one would expect for an isothermal atmosphere, but rather: 1 H n = g M R T 0 − L T 0 {\displaystyle {\frac {1}{H_{n}}}={\frac {gM}{RT_{0}}}-{\frac {L}{T_{0}}}} Which gives H n = 10.4   km. Note that for different gasses,

2139-492: Is identical to the isothermal solution, with the same height scale H p = RT 0 / gM . Note that the hydrostatic equation no longer holds for the exponential approximation (unless L is neglected). H p is 8.4   km, but for different gasses (measuring their partial pressure), it is again different and depends upon molar mass, giving 8.7 for nitrogen, 7.6 for oxygen and 5.6 for carbon dioxide. Further note that since g , Earth's gravitational acceleration ,

2232-601: Is possible to control several same-type guns on a single platform simultaneously, while both the firing guns and the target are moving. Though a ship rolls and pitches at a slower rate than a tank does, gyroscopic stabilization is extremely desirable. Naval gun fire control potentially involves three levels of complexity: Corrections can be made for surface wind velocity, roll and pitch of the firing ship, powder magazine temperature, drift of rifled projectiles, individual gun bore diameter adjusted for shot-to-shot enlargement, and rate-of-change of range with additional modifications to

2325-437: Is used to determine or estimate the altitude or slant range of the aerial target. Two observers then track the aircraft through a pair of telescopes on opposite sides of the director. The trackers turn handwheels to keep the crosshairs of their respective telescope on the aircraft image. The rotation of the handwheels provides the director with data on the aircraft's change in elevation and change in azimuth in relation to

2418-510: The Sims class employed one of these computers, battleships up to four. The system's effectiveness against aircraft diminished as planes became faster, but toward the end of World War II upgrades were made to the Mark 37 System, and it was made compatible with the development of the VT (Variable Time) proximity fuze which exploded when it was near a target, rather than by timer or altitude, greatly increasing

2511-621: The Battle of Tsushima during 27–28 May 1905. Centralized naval fire control systems were first developed around the time of World War I . Local control had been used up until that time, and remained in use on smaller warships and auxiliaries through World War II . Specifications of HMS  Dreadnought were finalized after the report on the Battle of Tsushima was submitted by the official observer to IJN onboard Asahi , Captain Pakenham (later Admiral), who observed how Kato's system worked first hand. From this design on, large warships had

2604-764: The Imperial Japanese Navy (IJN), they were well aware of the experiments. During the 10 August 1904 Battle of the Yellow Sea against the Russian Pacific Fleet , the British-built IJN battleship Asahi and her sister ship, the fleet flagship Mikasa , were equipped with the latest Barr and Stroud range finders on the bridge, but the ships were not designed for coordinated aiming and firing. Asahi ' s chief gunnery officer , Hiroharu Kato (later Commander of Combined Fleet ), experimented with

2697-473: The Naval Battle of Guadalcanal USS  Washington , in complete darkness, inflicted fatal damage at close range on the battleship Kirishima using a combination of optical and radar fire-control; comparisons between optical and radar tracking, during the battle, showed that radar tracking matched optical tracking in accuracy, while radar ranges were used throughout the battle. The last combat action for

2790-780: The ideal gas law as an approximation. The density of dry air can be calculated using the ideal gas law , expressed as a function of temperature and pressure: ρ = p R specific T R specific = R M = k B m ρ = p M R T = p m k B T {\displaystyle {\begin{aligned}\rho &={\frac {p}{R_{\text{specific}}T}}\\R_{\text{specific}}&={\frac {R}{M}}={\frac {k_{\rm {B}}}{m}}\\\rho &={\frac {pM}{RT}}={\frac {pm}{k_{\rm {B}}T}}\\\end{aligned}}} where: Therefore: The following table illustrates

2883-748: The partial pressure of water vapor is known as the vapor pressure . Using this method, error in the density calculation is less than 0.2% in the range of −10 °C to 50 °C. The density of humid air is found by: ρ humid air = p d R d T + p v R v T = p d M d + p v M v R T {\displaystyle \rho _{\text{humid air}}={\frac {p_{\text{d}}}{R_{\text{d}}T}}+{\frac {p_{\text{v}}}{R_{\text{v}}T}}={\frac {p_{\text{d}}M_{\text{d}}+p_{\text{v}}M_{\text{v}}}{RT}}} where: The vapor pressure of water may be calculated from

Director (military) - Misplaced Pages Continue

2976-600: The platoon commander. The range section's leader is also called a range setter; he guides the preparation of the director and generator for firing, verifies the orientation and synchronisation of the gun and the director, and supervises fire control using the M5 director (or by the carriage when the M7 Weissight is used). The range section that uses the M5 director consists of the range setter, elevation tracker, azimuth tracker, power plant operator and telephone operator. The M5 director

3069-846: The saturation vapor pressure and relative humidity . It is found by: p v = ϕ p sat {\displaystyle p_{\text{v}}=\phi p_{\text{sat}}} where: The saturation vapor pressure of water at any given temperature is the vapor pressure when relative humidity is 100%. One formula is Tetens' equation from used to find the saturation vapor pressure is: p sat = 0.61078 exp ⁡ ( 17.27 ( T − 273.15 ) T − 35.85 ) {\displaystyle p_{\text{sat}}=0.61078\exp \left({\frac {17.27(T-273.15)}{T-35.85}}\right)} where: See vapor pressure of water for other equations. The partial pressure of dry air p d {\displaystyle p_{\text{d}}}

3162-478: The 1960s, warship guns were largely operated by computerized systems, i.e. systems that were controlled by electronic computers, which were integrated with the ship's missile fire-control systems and other ship sensors. As technology advanced, many of these functions were eventually handled fully by central electronic computers. The major components of a gun fire-control system are a human-controlled director , along with or later replaced by radar or television camera,

3255-629: The 1990s removed the need for directors. Directors were mounted on a field tripod and oriented in relation to grid north of the map. If time was short this orientation usually used an integral compass, but was updated by calculation (azimuth by hour angle or azimuth by Polaris) or 'carried' by survey techniques from a survey control point. In the 1960s gyroscopic orientation was introduced. For anti-aircraft use, directors are usually used in conjunction with other fire control equipment, such as height finders or fire control radars . In some armies these 'directors' were called 'predictors'. The Mark 51 director

3348-570: The Mark 1, design modifications were extensive enough to change it to "Mark 1A". The Mark 1A appeared post World War II and may have incorporated technology developed for the Bell Labs Mark 8, Fire Control Computer . Sailors would stand around a box measuring 62 by 38 by 45 inches (1.57 by 0.97 by 1.14 m). Even though built with extensive use of an aluminum alloy framework (including thick internal mechanism support plates) and computing mechanisms mostly made of aluminum alloy, it weighed as much as

3441-439: The Mark 33 to be a satisfactory system, but wartime production problems, and the added weight and space requirements of the Mark 37 precluded phasing out the Mark 33: Although superior to older equipment, the computing mechanisms within the range keeper ([Mark 10]) were too slow, both in reaching initial solutions on first picking up a target and in accommodating frequent changes in solution caused by target maneuvers. The [Mark 33]

3534-422: The Mark 33, it supplied them with greater reliability and gave generally improved performance with 5-inch (13 cm) gun batteries, whether they were used for surface or antiaircraft use. Moreover, the stable element and computer, instead of being contained in the director housing were installed below deck where they were less vulnerable to attack and less of a jeopardy to a ship's stability. The design provided for

3627-576: The Type 98 Hoiban and Shagekiban on the Yamato class were more up to date, which eliminated the Sokutekiban , but it still relied on seven operators. In contrast to US radar aided system, the Japanese relied on averaging optical rangefinders, lacked gyros to sense the horizon, and required manual handling of follow-ups on the Sokutekiban , Shagekiban , Hoiban as well as guns themselves. This could have played

3720-577: The U.K.). In battleships, the Secondary Battery Plotting Rooms were down below the waterline and inside the armor belt. They contained four complete sets of the fire control equipment needed to aim and shoot at four targets. Each set included a Mark 1A computer, a Mark 6 Stable Element, FC radar controls and displays, parallax correctors, a switchboard, and people to operate it all. (In the early 20th century, successive range and/or bearing readings were probably plotted either by hand or by

3813-511: The US Navy's Mark 37 system required nearly 1000 rounds of 5 in (127 mm) mechanical fuze ammunition per kill, even in late 1944. The Mark 37 Gun Fire Control System incorporated the Mark 1 computer, the Mark 37 director, a gyroscopic stable element along with automatic gun control, and was the first US Navy dual-purpose GFCS to separate the computer from the director. Naval fire control resembles that of ground-based guns, but with no sharp distinction between direct and indirect fire. It

Director (military) - Misplaced Pages Continue

3906-533: The accuracy of the directors fell off sharply; even at intermediate ranges they left much to be desired. The weight and size of the equipments militated against rapid movement, making them difficult to shift from one target to another.Their efficiency was thus in inverse proportion to the proximity of danger. The computer was completed as the Ford Mark 1 computer by 1935. Rate information for height changes enabled complete solution for aircraft targets moving over 400 miles per hour (640 km/h). Destroyers starting with

3999-422: The air density–temperature relationship at 1 atm or 101.325 kPa: The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molar mass of water vapor (18   g/mol) is less than the molar mass of dry air (around 29   g/mol). For any ideal gas, at a given temperature and pressure, the number of molecules

4092-618: The air. This gave American forces a technological advantage in World War II against the Japanese, who did not develop remote power control for their guns; both the US Navy and Japanese Navy used visual correction of shots using shell splashes or air bursts, while the US Navy augmented visual spotting with radar. Digital computers would not be adopted for this purpose by the US until the mid-1970s; however, it must be emphasized that all analog anti-aircraft fire control systems had severe limitations, and even

4185-467: The analog rangekeepers, at least for the US Navy, was in the 1991 Persian Gulf War when the rangekeepers on the Iowa -class battleships directed their last rounds in combat. The Mark 33 GFCS was a power-driven fire control director, less advanced than the Mark 37. The Mark 33 GFCS used a Mark 10 Rangekeeper , analog fire-control computer. The entire rangekeeper was mounted in an open director rather than in

4278-625: The atmosphere, they are listed below, along with their values according to the International Standard Atmosphere , using for calculation the universal gas constant instead of the air specific constant: Temperature at altitude h {\displaystyle h} meters above sea level is approximated by the following formula (only valid inside the troposphere , no more than ~18   km above Earth's surface (and lower away from Equator)): T = T 0 − L h {\displaystyle T=T_{0}-Lh} The pressure at altitude h {\displaystyle h}

4371-425: The clear superiority of US radar-assisted systems at night. The rangekeeper's target position prediction characteristics could be used to defeat the rangekeeper. For example, many captains under long range gun attack would make violent maneuvers to "chase salvos." A ship that is chasing salvos is maneuvering to the position of the last salvo splashes. Because the rangekeepers are constantly predicting new positions for

4464-406: The command to commence firing. Unfortunately, this process of inferring the target motion vector required a few seconds, typically, which might take too long. The process of determining the target's motion vector was done primarily with an accurate constant-speed motor, disk-ball-roller integrators, nonlinear cams, mechanical resolvers, and differentials. Four special coordinate converters, each with

4557-461: The computer were closed, and movement of the gun director (along with changes in range) made the computer converge its internal values of target motion to values matching those of the target. While converging, the computer fed aided-tracking ("generated") range, bearing, and elevation to the gun director. If the target remained on a straight-line course at a constant speed (and in the case of aircraft, constant rate of change of altitude ("rate of climb"),

4650-462: The coordinate converter ("vector solver") was eliminated. The Stable Element, which in contemporary terminology would be called a vertical gyro, stabilized the sights in the director, and provided data to compute stabilizing corrections to the gun orders. Gun lead angles meant that gun-stabilizing commands differed from those needed to keep the director's sights stable. Ideal computation of gun stabilizing angles required an impractical number of terms in

4743-525: The correct firing solution, taking into account other parameters, such as wind direction, air temperature, and ballistic factors for the guns. The British Royal Navy widely deployed the Pollen and Dreyer Fire Control Tables during the First World War, while in World War II a widely used computer in the US Navy was the electro-mechanical Mark I Fire Control Computer . On ships the director control towers for

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4836-418: The crowded wartime production program were responsible for the fact the [Mark 33's] service was lengthened to the cessation of hostilities. The Mark 33 was used as the main director on some destroyers and as secondary battery / anti-aircraft director on larger ships (i.e. in the same role as the later Mark 37). The guns controlled by it were typically 5 inch weapons: the 5-inch/25 or 5-inch/38 . The Mark 34

4929-411: The density close to the ground is ρ 0 = p 0 M R T 0 {\textstyle \rho _{0}={\frac {p_{0}M}{RT_{0}}}} It can be easily verified that the hydrostatic equation holds: d p d h = − g ρ . {\displaystyle {\frac {dp}{dh}}=-g\rho .} As

5022-1036: The director also provides the flight time for the projectile so the fuze can be set to detonate close to the target. Early anti-aircraft artillery batteries located the directors in the middle of the position, with the firing sections (guns) located at the corners of the position. Before the introduction of radars , searchlights were used in conjunction with directors to allow night target engagement. 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 either optical or radar sighting. Most US ships that are destroyers or larger (but not destroyer escorts except Brooke class DEG's later designated FFG's or escort carriers) employed gun fire-control systems for 5-inch (127 mm) and larger guns, up to battleships, such as Iowa class . Beginning with ships built in

5115-430: The director was not located near the gun sections, a correction for parallax error could also be entered to produce even more accurate firing direction calculations. Directors transmit three important calculated firing solutions to the anti-aircraft gun firing crew: the correct firing azimuth and quadrant elevation calculated to determine where exactly to aim the gun, and for guns that use ammunition with timed fuzes ,

5208-506: The director. As the mechanisms inside the director respond to the rotation of the handwheels, a firing solution is mechanically calculated and continuously updated for as long as the target is tracked. Essentially, the director predicts future position based on the aircraft's present location and how it is moving. After their introduction, directors soon incorporated correction factors that could compensate for ballistic conditions such as air density , wind velocity and wind direction . If

5301-561: The directors, with individual installations varying from one aboard destroyers to four on each battleship. The development of the Gun Directors Mark 33 and 37 provided the United States Fleet with good long range fire control against attacking planes. But while that had seemed the most pressing problem at the time the equipments were placed under development, it was but one part of the total problem of air defense. At close-in ranges

5394-424: The fire control devices (or both). Humans were very good data filters, able to plot a useful trend line given somewhat-inconsistent readings. As well, the Mark 8 Rangekeeper included a plotter. The distinctive name for the fire-control equipment room took root, and persisted even when there were no plotters.) The Mark 1A Fire Control Computer was an electro-mechanical analog ballistic computer. Originally designated

5487-437: The fire control system early in World War II provided ships with the ability to conduct effective gunfire operations at long range in poor weather and at night. In a typical World War II British ship the fire control system connected the individual gun turrets to the director tower (where the sighting instruments were) and the analogue computer in the heart of the ship. In the director tower, operators trained their telescopes on

5580-413: The fire control system was initially installed, a surveyor, working in several stages, transferred the position of the gun director into Plot so the stable element's own internal mechanism was properly aligned to the director. Although the rangefinder had significant mass and inertia, the crosslevel servo normally was only lightly loaded, because the rangefinder's own inertia kept it essentially horizontal;

5673-562: The firing and target ships. The Dreyer Table was to be improved and served into the interwar period at which point it was superseded in new and reconstructed ships by the Admiralty Fire Control Table . The use of Director-controlled firing together with the fire control computer moved the control of the gun laying from the individual turrets to a central position (usually in a plotting room protected below armor), although individual gun mounts and multi-gun turrets could retain

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5766-459: The firing solution based upon the observation of preceding shots. More sophisticated fire control systems consider more of these factors rather than relying on simple correction of observed fall of shot. Differently colored dye markers were sometimes included with large shells so individual guns, or individual ships in formation, could distinguish their shell splashes during daylight. Early "computers" were people using numerical tables. The Royal Navy

5859-427: The first director system of fire control, using speaking tube (voicepipe) and telephone communication from the spotters high on the mast to his position on the bridge where he performed the range and deflection calculations, and from his position to the 12-inch (305 mm) gun turrets forward and astern. With the semi-synchronized salvo firing upon his voice command from the bridge, the spotters using stopwatches on

5952-467: The first installation of a Mark 33. The objective of weight reduction was not met, since the resulting director system actually weighed about 8,000 pounds (3,600 kg) more than the equipment it was slated to replace, but the Gun Director Mark 37 that emerged from the program possessed virtues that more than compensated for its extra weight. Though the gun orders it provided were the same as those of

6045-604: The gun turrets, he was steps away from the ship commander giving orders to change the course and the speed in response to the incoming reports on target movements. Kato was transferred to the fleet flagship Mikasa as the Chief Gunnery Officer, and his primitive control system was in fleet-wide operation by the time the Combined Fleet destroyed the Russian Baltic Fleet (renamed the 2nd and 3rd Pacific Fleet) in

6138-443: The introduction of indirect artillery fire. In US service these directors were called 'aiming circles'. Directors could also be used instead of theodolites for artillery survey over shorter distances. The first directors used an open sight rotating on an angular scale (e.g. degrees & minutes, grads or mils of one sort or another), but by World War I most directors were optical instruments. Introduction of digital artillery sights in

6231-448: The main battery are placed high on the superstructure, where they have the best view. Due to their large size and weight, in the World War II era the computers were located in plotting rooms deep in the ship, below the armored deck on armored ships. Directors were introduced into field artillery in the early 20th century to orient the guns of an artillery battery in their zero line (or 'centre of arc'). Directors were an essential element in

6324-449: The mast could identify the distant salvo of splashes created by the shells from their own ship more effectively than trying to identify a single splash among the many. Kato gave the firing order consistently at a particular moment in the rolling and pitching cycles of the ship, simplifying firing and correction duties formerly performed independently with varying accuracy using artificial horizon gauges in each turret. Moreover, unlike in

6417-480: The mathematical expression, so the computation was approximate. To compute lead angles and time fuze setting, the target motion vector's components as well as its range and altitude, wind direction and speed, and own ship's motion combined to predict the target's location when the shell reached it. This computation was done primarily with mechanical resolvers ("component solvers"), multipliers, and differentials, but also with one of four three-dimensional cams. Based on

6510-431: The measuring instruments used, different sets of equations for the calculation of the density of air can be applied. Air is a mixture of gases and the calculations always simplify, to a greater or lesser extent, the properties of the mixture. Other things being equal (most notably the pressure and humidity), hotter air is less dense than cooler air and will thus rise while cooler air tends to fall. This can be seen by using

6603-513: The optical sight telescopes, rangefinder, and radar antenna free from the effects of deck tilt. The signal that kept the rangefinder's axis horizontal was called "crosslevel"; elevation stabilization was called simply "level". Although the stable element was below decks in Plot, next to the Mark 1/1A computer, its internal gimbals followed director motion in bearing and elevation so that it provided level and crosslevel data directly. To do so, accurately, when

6696-406: The predictions became accurate and, with further computation, gave correct values for the gun lead angles and fuze setting. The target's movement was a vector, and if that didn't change, the generated range, bearing, and elevation were accurate for up to 30 seconds. Once the target's motion vector became stable, the computer operators told the gun director officer ("Solution Plot!"), who usually gave

6789-597: The predictions, the other three of the three-dimensional cams provided data on ballistics of the gun and ammunition that the computer was designed for; it could not be used for a different size or type of gun except by rebuilding that could take weeks. Air density The density of air or atmospheric density , denoted ρ , is the mass per unit volume of Earth's atmosphere . Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmospheric pressure, temperature and humidity . At 101.325 kPa (abs) and 20 °C (68 °F), air has

6882-461: The probability that any one shell would destroy a target. The function of the Mark 37 Director, which resembles a gun mount with "ears" rather than guns, was to track the present position of the target in bearing, elevation, and range. To do this, it had optical sights (the rectangular windows or hatches on the front), an optical rangefinder (the tubes or ears sticking out each side), and later models, fire control radar antennas. The rectangular antenna

6975-515: The range to 5 miles (8.0 km). Although the Japanese pursued a doctrine of achieving superiority at long gun ranges, one cruiser fell victim to secondary explosions caused by hits from the carriers' single 5-inch guns. Eventually with the aid of hundreds of carrier based aircraft, a battered Center Force was turned back just before it could have finished off survivors of the lightly armed task force of screening escorts and escort carriers of Taffy 3. The earlier Battle of Surigao Strait had established

7068-480: The rangekeeper's commands with no manual intervention, though pointers still worked even if automatic control was lost. The Mark 1 and Mark 1A computers contained approximately 20 servomechanisms, mostly position servos, to minimize torque load on the computing mechanisms. During their long service life, rangekeepers were updated often as technology advanced and by World War II they were a critical part of an integrated fire control system. The incorporation of radar into

7161-467: The rangekeepers would generate the necessary angles automatically but sailors had to manually follow the directions of the rangekeepers. This task was called "pointer following" but the crews tended to make inadvertent errors when they became fatigued during extended battles. During World War II, servomechanisms (called "power drives" in the US Navy) were developed that allowed the guns to automatically steer to

7254-462: The same for bearing. When the guns were on target they were centrally fired. The Aichi Clock Company first produced the Type 92 Shagekiban low angle analog computer in 1932. The US Navy Rangekeeper and the Mark 38 GFCS had an edge over Imperial Japanese Navy systems in operability and flexibility. The US system allowing the plotting room team to quickly identify target motion changes and apply appropriate corrections. The newer Japanese systems such as

7347-454: The servo's task was usually simply to ensure that the rangefinder and sight telescopes remained horizontal. Mark 37 director train (bearing) and elevation drives were by D.C. motors fed from Amplidyne rotary power-amplifying generators. Although the train Amplidyne was rated at several kilowatts maximum output, its input signal came from a pair of 6L6 audio beam tetrode vacuum tubes (valves, in

7440-420: The superstructure had a better view of the enemy than a turret mounted sight, and the crew operating it were distant from the sound and shock of the guns. Unmeasured and uncontrollable ballistic factors like high altitude temperature, humidity, barometric pressure, wind direction and velocity required final adjustment through observation of fall of shot. Visual range measurement (of both target and shell splashes)

7533-421: The target, it is unlikely that subsequent salvos will strike the position of the previous salvo. The direction of the turn is unimportant, as long as it is not predicted by the enemy system. Since the aim of the next salvo depends on observation of the position and speed at the time the previous salvo hits, that is the optimal time to change direction. Practical rangekeepers had to assume that targets were moving in

7626-560: The target; one telescope measured elevation and the other bearing. Rangefinder telescopes on a separate mounting measured the distance to the target. These measurements were converted by the Fire Control Table into bearings and elevations for the guns to fire on. In the turrets, the gunlayers adjusted the elevation of their guns to match an indicator which was the elevation transmitted from the Fire Control Table—a turret layer did

7719-1270: The temperature varies with height inside the troposphere by less than 25%, L h T 0 < 0.25 {\textstyle {\frac {Lh}{T_{0}}}<0.25} and one may approximate: ρ = ρ 0 e ( g M R L − 1 ) ln ⁡ ( 1 − L h T 0 ) ≈ ρ 0 e − ( g M R L − 1 ) L h T 0 = ρ 0 e − ( g M h R T 0 − L h T 0 ) {\displaystyle \rho =\rho _{0}e^{\left({\frac {gM}{RL}}-1\right)\ln \left(1-{\frac {Lh}{T_{0}}}\right)}\approx \rho _{0}e^{-\left({\frac {gM}{RL}}-1\right){\frac {Lh}{T_{0}}}}=\rho _{0}e^{-\left({\frac {gMh}{RT_{0}}}-{\frac {Lh}{T_{0}}}\right)}} Thus: ρ ≈ ρ 0 e − h / H n {\displaystyle \rho \approx \rho _{0}e^{-h/H_{n}}} Which

7812-409: The two computers is their ballistics calculations. The amount of gun elevation needed to project a 5-inch (130 mm) shell 9 nautical miles (17 km) is very different from the elevation needed to project a 16-inch (41 cm) shell the same distance. In operation, this computer received target range, bearing, and elevation from the gun director. As long as the director was on target, clutches in

7905-481: The ultimate addition of radar, which later permitted blind firing with the director. In fact, the Mark 37 system was almost continually improved. By the end of 1945 the equipment had run through 92 modifications—almost twice the total number of directors of that type which were in the fleet on December 7, 1941. Procurement ultimately totalled 841 units, representing an investment of well over $ 148,000,000. Destroyers, cruisers, battleships, carriers, and many auxiliaries used

7998-973: The value of H n differs, according to the molar mass M : It is 10.9 for nitrogen, 9.2 for oxygen and 6.3 for carbon dioxide . The theoretical value for water vapor is 19.6, but due to vapor condensation the water vapor density dependence is highly variable and is not well approximated by this formula. The pressure can be approximated by another exponent: p = p 0 e g M R L ln ⁡ ( 1 − L h T 0 ) ≈ p 0 e − g M R L L h T 0 = p 0 e − g M h R T 0 {\displaystyle p=p_{0}e^{{\frac {gM}{RL}}\ln \left(1-{\frac {Lh}{T_{0}}}\right)}\approx p_{0}e^{-{\frac {gM}{RL}}{\frac {Lh}{T_{0}}}}=p_{0}e^{-{\frac {gMh}{RT_{0}}}}} Which

8091-505: The world at that time, only three percent of their shots actually struck their targets. At that time, the British primarily used a manual fire control system. This experience contributed to computing rangekeepers becoming standard issue. The US Navy's first deployment of a rangekeeper was on USS  Texas in 1916. Because of the limitations of the technology at that time, the initial rangekeepers were crude. For example, during World War I

8184-529: Was aware of the fall of shot observation advantage of salvo firing through several experiments as early as 1870 when Commander John A. Fisher installed an electric system enabling a simultaneous firing of all the guns to HMS Ocean , the flagship of the China Station as the second in command. However, the Station or Royal Navy had not yet implemented the system fleet-wide in 1904. The Royal Navy considered Russia

8277-449: Was difficult prior to availability of radar. The British favoured coincidence rangefinders while the Germans and the US Navy, stereoscopic type. The former were less able to range on an indistinct target but easier on the operator over a long period of use, the latter the reverse. During the Battle of Jutland , while the British were thought by some to have the finest fire control system in

8370-412: Was thus distinctly inadequate, as indicated to some observers in simulated air attack exercises prior to hostilities. However, final recognition of the seriousness of the deficiency and initiation of replacement plans were delayed by the below decks space difficulty, mentioned in connection with the [Mark 28] replacement. Furthermore, priorities of replacements of older and less effective director systems in

8463-572: Was to automatically aim the guns so that a fired projectile would collide with the target. This is the same function as the main battery's Mark 8 Rangekeeper used in the Mark 38 GFCS except that some of the targets the Mark 1A had to deal with also moved in elevation—and much faster. For a surface target, the Secondary Battery's Fire Control problem is the same as the Main Battery's with the same type inputs and outputs. The major difference between

8556-456: Was used by the US Navy for 40 mm guns and later for 3"/50 caliber guns . The Kerrison Predictor was also designed to be used with the Bofors 40 mm gun . The Bofors 40 mm gun (called a fire unit) used in its anti-aircraft role has the M5 director for its fire-control system . The director is operated by a member of the range section who reports to the chief of section, who in turn reports to

8649-557: Was used to control the main batteries of large gun ships. Its predecessors include Mk18 ( Pensacola class ), Mk24 ( Northampton class ), Mk27 ( Portland class ) and Mk31 ( New Orleans class ) According to the US Navy Bureau of Ordnance, While the defects were not prohibitive and the Mark 33 remained in production until fairly late in World War II, the Bureau started the development of an improved director in 1936, only 2 years after

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