Armament of the Iowa-class battleship
The Iowa-class battleships are the most heavily armed warships the United States Navy has ever put to sea, due to the continual development of their onboard weaponry.
The secondary battery of 5-inch (127 mm) guns could hit targets nearly 9 statute miles (14 km) away with solid projectiles or proximity fuzed shells, and was effective in an anti-aircraft role as well.
The primary armament of an Iowa-class battleship consisted of nine breech-loading 16 inch (406 mm)/50-caliber Mark 7 naval guns,[1] which were housed in three 3-gun turrets: two forward and one aft in a configuration known as "2-A-1".
[3] When brought into service during World War II the guns had a barrel life of roughly 290 rounds, limited in large part by the nitrated cellulose (NC) propellant.
[3] After World War II the Navy switched to smokeless powder diphenylamine (SPD), a cooler-burning propellant, which increased the barrel life from 290 to about 350 rounds.
This was increased further by the introduction of a titanium dioxide and wax compound known as "Swedish Additive" on New Jersey for her tour in Vietnam, and later used on all four Iowas when they were reactivated in the 1980s.
[3] These measures were further augmented by the addition of polyurethane jackets, which were placed over the powder bags to reduce gaseous erosion during the firing of the guns.
[3] The major components of the Mk 38 Gun Fire Control System (GFCS) were the Director, Plotting Room, and interconnecting data transmission equipment.
The present position of the target was called the Line-Of-Sight (LOS),[12] and it was continuously sent down to the Mk 8 Rangekeeper in the plotting room by Synchro transmitters.
[13] The Mk 8 Rangekeeper was an electromechanical analog computer[14] whose function was to continuously calculate the gun's bearing and elevation, Line-Of-Fire (LOF), to hit a future position of the target.
[14] Also, before the surface action started, the FTs made manual inputs for the average initial velocity of the projectiles fired out of the battery's gun barrels, and air density.
When this key was held closed, the Mk 41 was enabled to automatically fire the guns whenever the ship's deck was parallel the horizontal plane.
[19] The assistant Gunnery Officers and Fire Control Technicians operated the equipment, talked to the turrets and ship's command by sound-powered telephone, and watched the Rangekeeper's dials and system status indicators for problems.
8 APC (Armor-Piercing, Capped) shell weighed 2,700 lb (1225 kg) and was designed to penetrate the hardened steel armor carried by foreign battleships.
These shells were born from the concept of nuclear deterrence that had begun to shape the United States armed forces as the Cold War began.
The shells entered development around 1953, and were reportedly ready by 1956; it is not known whether they were ever deployed on the Iowa-class battleships because the US Navy does not confirm or deny the presence of nuclear weapons aboard its ships.
[24] At first, this battery's effectiveness against aircraft diminished as planes became faster, but this changed toward the end of World War II through a combination of an upgrade to the Mk37 System and the development of the VT (Variable Time) proximity fuze.
[23] The mount had a crew of 13, not including the ammunition movers in the upper handling room and magazines, drawn from the sailors and Marines serving aboard the ship.
The responsibility of the men stationed in the upper handling room was to shuttle 30 to 40 projectiles and 30 to 40 powder cases per minute from the ready service racks to the hoists while avoiding the equipment rotating with the mount.
When coupled with electric-hydraulic drives for greater speed and the Mark 51 Director (pictured) for improved accuracy, the Bofors 40 mm gun became a fearsome adversary, accounting for roughly half of all Japanese aircraft shot down between 1 October 1944 and 1 February 1945.
[30] When the Iowa-class battleships were launched in 1943 and 1944 they carried twenty quad Bofors 40 mm gun mounts, which they used for defense against enemy aircraft.
These heavy guns were also employed in the protection of allied aircraft carriers operating in the Pacific Theater of World War II.
[24] During their modernization in the 1980s, each Iowa-class battleship was equipped with four of the US Navy's Phalanx CIWS mounts, two of which sat just behind the bridge and two which were forward and outboard of the after ship's funnel.
At one point the NATO Sea Sparrow was to be installed on the reactivated battleships; however, it was determined that the system could not withstand the over-pressure effects when the main battery was fired.
Designed as a long-range, all-weather, subsonic cruise missile, the Tomahawk was capable of reaching targets at a much greater range than the 16-inch (406 mm) guns on the Iowa-class ships.
[40] The TLAM could be equipped with an inertial and terrain contour matching (TERCOM) radar guidance package to find and destroy its target.
The system consisted of four Mk 141 "shock-hardened" quad cell launchers designed to carry and fire the McDonnell Douglas RGM-84 Harpoon anti-ship missile.
The stabilizing and actuator fins, which helped to guide the missile to its target, were stored folded in the canister and sprang into position after launching.
[42] After launch, the missile was guided towards the target location as determined by the ship using a three-axis Attitude Reference Assembly (ATA) in an AN/DSQ-44 guidance section.
The radar switch-on distance could be set to lower or higher values, the former requiring a more precisely-known target location but reducing the risk to be defeated by enemy Electronic Counter Measures (ECM).
