Category:Fire Control: Difference between revisions

Fire Control is the process of directing a weapon so that when it is fired, the missile will travel in such a way as to impact an intended target. Although similar methods can be applied to torpedoes, the term is generally used to describe the aiming and use of naval gunfire. Fire control is practiced in many forms and sometimes in various levels depending on the weapon type, the nationality, and the era in question.

It is a poorly understood field of endeavour, particularly in the Dreadnought Era, that one can find very few books on the subject. Many that do cover the topic have such errors of fact and vague prose that it seems clear that the author did not understand the subject deeply, if at all.

Modern naval gunnery's genesis might be identified by the emergence of some interlocking innovations in the 1890s.

Adjustable Gunsights

Before gun ranges grew beyond a few hundred yards, it was generally sufficient to sight along the barrel of the weapon and touch off the powder to secure good chances of hitting the target. Rate of fire and discretion as to when to fire the weapon were the primary measures of effective gunnery in such times.

As guns, projectiles and powders were developed that could reach longer ranges with precision, gun sights were devised that could articulate in pitch and azimuth so that the sighting line could differ from the axis of the barrel, providing a means of elevating the gun above the line of sight and also establishing a little lateral "Kentucky windage" to account for cross-wind or relative motion of the target. The general principle was that the sight trained with the mounting and elevated (but did not recoil) with the gun. A graduated range scale (often a large dial) could be set to the range the target was presumed to be at, and this would cause the sighting optics (an open sight or telescope) to be depressed by the corresponding angle of elevation that would be required to send the shell to that range. The man looking through the scope who could work the gun (and sight assembly) in elevation would then find that he was looking at the water – his job was to elevate the weapon to again place the crosshairs on target. This placed the gun at the proper elevation to hit the target, provided the range on the sight was correct. A similar process in azimuth allows the sight to be set for deflection left or right, which would rotate the optics in the opposite direction. The man who worked the mount in azimuth would then rotate it to again place his crosshairs on, and the proper lateral aim-off was thereby established.

With an adjustable gunsight of this nature, the people pointing the gun were tasked with keeping their crosshairs on the target. The process which informed the choice of range and deflection to use would become the realm of 20th century naval fire control.

Dedicated Sightsetters

One of the first innovations in gunnery as the Dreadnought Era began was the emergence of sightsetting as a separate duty deserving of the work of a crewman dedicated to ensuring the range and deflection on the sight were those desired. This concept's pervasive adoption, along with the an increasing rate of fire afforded by the use of breech loading guns, continuous aim, and improvements in drill and ammunition handling made gunnery fast and effective whereas before it had been largely a show of bellicose intentions.

Rangefinders

Finding the proper range for the sightsetting equipment became a challenge as ranges grew, as a guessing game of trial and error might allow the enemy to achieve the first, crucial hits. Short base rangefinders began to appear in the Russo-Japanese War, but they did not prove helpful owing to insufficient accuracy and the lack of a reliable means for conveying their output to the guns. Accuracy improved as rangefinders grew in size and number, but the equipment and procedures to effectively incorporate their range cuts into successful firing was slower to emerge.

One important aspect of British fire control in this period is that it relied heavily on the use of rangefinders which did not perform nearly as well as the designers of the fire control systems hoped.

Salvo Firing

A separate development suggested by uneven and chaotic gunnery during the battles of the Russo-Japanese War was that gun fire had to be made more systematic so that the results being obtained could be clearly observed and corrected. This was achieved in part by moving to ships mounting fewer types of guns (typified by the "all big gun" progeny of Dreadnought). Another helpful change was to make one group of well-situated spotters responsible for adjusting the range and deflection on the guns and providing a means by which they could conveniently communicate these spotting corrections to the sightsetters.

In this manner, the process of regulating fire built upon the foundation of sightsetting, and the fire emanating from a battleship began to look like the pulsing stream from the nozzle of a garden hose rather than the sprinkler head it had previously resembled.

Director Firing

A related innovation to the use of firing in salvoes was intended to reduce salvo pattern size by having all the guns point as though driven by the hand of a single gunlayer and a single trainer. This would not reduce or eliminate pointing errors, but it would greatly reduce their variety. The solution was to use a central director which would aim at the target and cause its elevation and training angle to be transmitted automatically and continuously to the guns which would seek to rotely match the indicated pose.

The British and Germans both deployed directors first in their dreadnoughts and battlecruisers, and later shipped smaller versions for use in their smaller vessels as well as to control the secondary batteries of their capital ships. It is worth noting that the German director handled training only, and not elevation; German dreadnoughts and battlecruisers used local laying and fired on the sound of a gong to produce a semi-simultaneous salvo. The British directors generally transmitted elevation and training, and also fired the guns by a distributed electrical circuit, giving the Royal Navy a more complete director system.

Data and Communication Circuitry

Once spotting, salvo firing and sightsetting were available, the need for special instruments to help coordinate the fighting grew rapidly. These devices ranged from common tools such as voicepipes and telephone networks to specialised data transmitters and receivers which explicitly conveyed mechanical indications germane to successful gunnery, such as orders, ranges, deflections, etc.

The nature of the data network instruments installed and the configuration of the network of wires tying them together varied widely from ship to ship. Some of these devices were intimate components of director firing, as the director had to signal angles of elevation and bearing to the guns, and this implies transmitters at the director and receivers at the guns. Other instruments such as the Evershed Bearing Indicator were simply intended to ensure that range-takers, spotters and trainers everyone were indeed all looking at the same target

The greatest determinant of how a ship's network was defined was naturally the big picture question: how did the ship and her crew intend to determine the range and deflection to hit their target? This was a considerable area of possibilities, and often made all the difference in whether a gun battle would be won or lost.

Determining Range and Deflection

There was no magic sensor to measure ranges to a target, nor was there one to determine its bearing. Even if there were, one would still need processes to quickly compute a deflection. Worse, battles in World War I soon showed that few commanders could resist the temptation of firing as soon as the enemy fell within range of the guns, and this meant that he was barely visible at all! This sparked a desire to create equipment and procedures that could allow a ship to throw as much data as could be collected into a black box to derive the likely best range and deflection for each successive salvo.

Dumaresqs and Dumaresq-like Instruments

Observers aloft could often get a fair guess of speed, bearing and inclination for even a distant target. It was natural to want a machine that could combine these estimates with a knowledge of one's ship's own speed and heading and to derive a range rate and speed-across, from which a gun deflection could be calculated (by use of graphic cards showing their relation at different ranges).

The British used dumaresqs for this. The German EU/SV Anzeiger was similar in function, but different in mechanical design.

Range Clocks

Simple range clocks soon appeared to combine an initial range estimate with a range rate to continuously generate a series of ranges over time. Suddenly, the fire control staff became the creators and maintainers of a virtual model of the range. The clocks generally only ran at a constant range rate unless adjusted further, but in long range actions this approximation of the range might be fairly good for a few salvoes while more range cuts and spotting reports being collected.

Plotting

With range and bearing data being reported sporadically, one natural choice for how to exploit it was to record it on paper so it could be seen. There were many schools of thought on the subject.

True Course Plotting

The most straightforward approach was to draw a diagram of the battle's time-track as if you were a satellite in the sky. Own ship's course would be maintained in the same manner a navigational track plot had long been managed — by referring to a compass and a speedometer of some kind and using draughting techniques to draw it on paper. Elsewhere on the paper, the estimated position and the resultant course and speed of the enemy would be attempted by using ranges and bearings being reported from above.

Although true course plotting resulted in a nice souvenir at the end of a battle, it did not prove very good at helping you win it. For one thing, one has to choose which ranges and bearings to trust, and which might be more trustworthy than others. If the plot is manually drawn, the people drawing it will be moving all about the table and getting in the way of anyone attempting to then examine the drawing to make decisions of what it implied about range rate and deflection. The biggest problem, however, is the very task of determining range and deflection from such a drawing at all; dedicating your observational data to this format has done nothing at all to advance you toward the goal of pulling out a range rate and deflection. You would need some sort of magic protractor and some very well-designed graph cards to shoot well with a true course plot. And of course some strong liniment for your back.

Straight Course Plotting

Straight course plotting depicted own ship's travel as if it were steaming in a straight line, even in the event of turning. In one variation, all plots of the enemy were taken as if own ship continued on its initial course. In another, enemy position plots would be taken up relative to a new heading after own ship completed a turn. These methods offered advantages over true course plots in that the person making the plot could stay at one edge of the plotting table.

Virtual Course Plotting

Virtual course plotting might have more accurately been called "relative course plotting", as it assumed own ship was at rest. In effect, this plot was a polar one (with own ship at center) and was maintained as simply as tossing a point onto the paper at a distance proportional to the latest range cut and at an angle equal to the latest compass bearing to the target.

This was very convenient for setting a dumaresq, as its pointer's position relative to the center of the dial plate was equivalent to the relative motion of the enemy. The enemy speed and heading could then be noted.

See Also

Footnotes

Bibliography