Nelson is shown on 23 May 1944, prior to her big refit in the United States. During her last pre-war refit (June 1937–January 1938) she was fitted with a second high-angle director atop an enlarged stub mast, evident here (because she was never heavily refitted before 1939, her sister-ship Rodney spent the war with a narrower mast carrying only a single high-angle director). The high-angle and main-battery directors, but not the 6in directors, are equipped with radar: Types 285 and 284, respectively. By this time the torpedo directors (and tubes) were gone and the ship had considerable additional light anti-aircraft firepower in the form of Oerlikon guns. The 4.7in anti-aircraft guns, replacement of which was often discussed before and during the war, had been given splinter shields (note the gun visible in front of the pom-pom abreast the funnel). The ship’s foremast carried the receiving antenna of a Type 281 air-search radar.
Gun accuracy was affected by dispersion: how well a gun could continue to put its shots into a particular place. By 1905 there was evidence that at the highest muzzle velocities guns sometimes whipped on firing, ruining their accuracy. For example, the 12in/50 Mk XII was disliked for excessive dispersion. On the other hand, the flatter a gun’s trajectory, the greater the fire-control error it could tolerate. This quality was measured by the danger space, the range error in which the target would still be hit.9 Higher velocity meant a flatter trajectory – but it could also mean much greater wear. When the Royal Navy returned to building capital ships with the King George V class, the question was whether to seek high muzzle velocity, for example using a lighter shell.
The powder charge in the gun produced, roughly, a fixed muzzle energy which could be divided between shell weight and velocity. A lighter shell would be fired at higher velocity, but it would lose velocity (energy) more quickly. The lighter shell would go further faster and would descend at a shallower angle (wider danger space). The slower, heavier shell would retain more of its velocity out to greater ranges, hence would penetrate armour better at greater ranges, it would have greater bursting effect and gun wear would be considerably less.10 This combination was the logic of the 13.5in and 15in guns in British service. The Germans opted for a much lighter shell (1653lbs) and higher velocity in their First World War 15in gun.
Photographed in Hampton Roads after a US refit on 2 June 1943, HMS Queen Elizabeth shows the next stage in British capital-ship bridge development. Like Nelson, she has a tower bridge intended to provide rigid support to her directors, in this case a main-battery DCT and two dual-purpose directors on the platform above the bridge structure. The compass platform has been brought back to the upper bridge level. Visible abreast the barbette of the main-battery director are two target designators of the air-defence position, which had to be located adjacent to the command on the fore end of this level. The level below is the admiral’s bridge. The object at the after end of the flag bridge is a pom-pom director (with Type 282 radar) controlling the octuple pom-pom visible abaft the tower bridge. At the fore end of the bridge is a barrage director with a Type 283 radar. The slits below indicate the protected steering position, a subject of considerable controversy later on. All of the directors have related radars with ‘fishbone’ antennas: Type 285 on the two dual-purpose directors, Type 284 on the main-battery director. The ‘lantern’ above the dual-purpose directors is for a Type 273 surface-search radar; the antenna for the ship’s air-search radar is not visible in this photograph. Oerlikons populate the signal bridge at the same level as the steering position.
HMS King George V is shown in the Severn River, Maryland, while delivering Lord Halifax to the United States as ambassador, January 1941. She has the open compass platform British naval officers wanted; sometimes it was covered over against weather, but the open top was wanted for anti-air actions. A shelter was provided at the after end of the platform. The wing visible jutting out from the after part of the compass platform held air lookouts, each of which could indicate a target using the devices visible here. Below the compass platform is the admiral’s bridge, with a rangefinder (for tactical plotting) visible in the bridge wing. Below that, slits indicate the protected steering position, with charthouse adjacent to it. The level below housed the admiral’s sea cabin. The two objects in tubs are pom-pom directors, as yet without their range-only Type 282 radars. The two octuple pom-poms they controlled are visible abaft the bridge structure. On the signal bridge below the admiral’s bridge can be seen two signal lights and a 44in searchlight for night action. The director visible above the compass platform controlled the ship’s main battery (two dual-purpose directors, for the 5.25in guns, were mounted on the pedestal emerging from the rear end of the tower bridge structure). It carries the two aerials (only the upper one is visible) of a Type 284 range-only main battery radar; as yet the dual-purpose directors lack any radar. Visible atop ‘B’ turret is a UP (unrotated projectile, i.e., rocket) launcher in its blast shield. (Naval Institute Collection)
The British solution was to accept limited muzzle velocities (typically about 2500ft/sec), usually with heavy shells. In 1918 DNO pointed out that the Germans seemed to be achieving at least the same accuracy with little wear at 2800ft/sec, using built-up guns. Generally the British chose a combination of shell weight and velocity offering accuracy, good performance against armour at fighting ranges and reasonable gun lifetime (usually measured in equivalent full charge shots or EFCs). Gun size and weight had to be such that it could be mounted in a turret of reasonable size.11 DNC’s account of the design of the Queen Elizabeth class, for example, stressed the considerable effort required to provide enough structure to support their unusually massive twin 15in turrets. Other navies did not always make the same choices; for example, the Italians chose very high velocity and short gun lifetime in their Second World War 15in gun.
DNO pointed out in 1935 that the extra velocity associated with a 50- rather than 45-calibre gun mattered for armour penetration only at and beyond 20,000 yds, as below that range both 45- and 50-calibre guns could defeat plates up to 13½in thick. As for danger space, the longer higher-velocity gun enjoyed an appreciable advantage only below 10,000 yds – where the danger spaces of both 45- and 50-calibre guns exceeded 100 yds. On the other hand, the extra 5 calibres would impact turret design. Lengthening the barrel would move the gun’s centre of gravity further from the breech face. In that case the gun would have to be supported further from the breech and the roller path considerably enlarged (and turret weight considerably increased). Hence the choice of 45 calibres for the 14in gun arming the 1936 battleships. What DNO did not say about the virtues of lower-velocity heavy shells is interesting. At very long ranges, such shells would hit deck armour with extra force.12 That is why the US Navy adopted them.
The builder’s model of HMS Vanguard, formerly in the Science Museum, London, shows the ship’s bridge, in effect the culmination of British thinking about battleship command. Arrangements were extensively revised both to improve command and control and to improve performance in wind (using wind-tunnel experiments). The side of the compass platform was the air defence lookout position, which in earlier ships was located abaft the compass platform. Abaft and inboard was the ADO’s position, with a target designator. Another target designator is visible at the rear of the compass platform proper, in the centre of the forward upper bridge. Slits indicated the protected steering position directly under the compass platform. Abaft it was the charthouse, with the captain’s sea cabin on the port side. Below was the admiral’s compass platform, with the bridge plotting room behind it. (Author)
HMS New Zealand shows a standard turret configuration of around 1914, with three