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Four battleships of the Iowa-class battleships (BB-61 through BB-64) were built in the early 1940s in the United States. Two other Iowa-class ships, Illinois and Kentucky, were scrapped prior to completion. The Iowa-class was preceeded by the South Dakota class battleships and would have been succeded by the Montana class battleships if the Montana's had not been cancelled prior to construction.
The Iowa class were constructed at two Navy Yards:
- Iowa (BB-61), built at the New York Navy Yard, Brooklyn, New York;
- New Jersey (BB-62), built at the Philadelphia Navy Yard;
- Missouri (BB-63), built at the New York Navy Yard;
- Wisconsin (BB-64), built at the Philadelphia Navy Yard;
- Illinois (BB-65), keel laid at Philadelphia Navy Yard. Cancelled 12 August, 1945;
- Kentucky (BB-66), keel laid at New York Navy Yard. Cancelled 17, February, 1947.
All four ships were recommissioned in the 1980s, only to be decommissioned after a few short years of service. Built as cost-no-object gunships, the Iowas are arguably the finest battleships ever built (their only serious competition are their predecessor South Dakota class and the Japanese Yamato class). The Iowa design was based upon the SoDaks but with more powerful engines, larger guns and an additional 200 feet of length for improved seakeeping. The Iowas are also among the most attractive battleships ever built, with a long, narrow, elegant bow and three powerful gun turrets.
Currently, three of the ships are on display at the following locations:
USS New Jersey
On October 14, 2001, USS New Jersey opened as a museum at Camden, New Jersey.
USS Missouri
Located 1,000 yards from USS Arizona at Pearl Harbor, Missouri was opened as a museum 29 January 1999. The museum is operated by the USS Missouri Memorial Association, a non-profit organization.
USS Wisconsin
Berthed in Norfolk, Virginia
The fourth ship of the class, USS Iowa, is currently part of the Naval Reserve Fleet and is currently berthed at Suisun Bay in San Francisco.
General Characteristics (USS Iowa)
- Displacement: 45,000 tons (stand); 56,500 (mean war service)
- Length: 887'3"
- Beam: 108'2"
- Draft: 37'9"
- Speed: 33 knots
- Complement: 2,800
- Armament: Nine 16" guns; twenty 5" guns; 20 40mm quads; 47-52 20mm (WWII)
- Nine 16" guns; 12 5" guns; 32 Tomahawk Cruise Missiles; 16 Harpoon Anti-Ship Cruise missiles; 4 Phalanx Close-in weapon system anti-aircraft/anti-missile. (1991)
- Max cruising radius:
- 9,600 miles @ 25 knots
- 16,600 miles @ 15 knots
- Power: 212,000 hp (shaft) forward; 44,000 hp (shaft) reverse
- Drive: 4 screws; geared turbines
- Fuel: 9,033 tons oil (max)
Engineering Plant
The Iowa-Class battleships are the fastest battleships ever launched by any nation, capable of sustained speeds of 33 knots or better. This is made possible by her design including her engineering plant which consists of 4 General Electric double-expansion steam turbine engines. Each engine feeds a single shaft which turns one of the ship's four screws. The two outboard screws on the Iowa-class are 4-bladed and just over 18 feet in diameter. The two inboard screws are 5-bladed and approximately 17.5 feet in diameter.
The engines receive the steam that turns the turbines from eight Babcock and Wilcox M-Type boilers which heat the water in tubes to a temperature of more than 800 degrees fahrenheit, which produces 650 psi of steam pressure.
The double-expansion engines consist of a high-pressure (HP) turbine and a low-pressure (LP) turbine. The steam is first passed through the HP turbine which turns at up to 2100RPM. The steam, largely depleted at this point, is then passed through a large conduit to the LP turbine. By the time it reaches the LP turbine it has no more than 50psi of pressure left. The LP turbine acts somewhat like a turbocharger, increasing the efficiency and power output of the engine by squeezing the last little bit of energy out of the steam.
After leaving the LP turbine the exhausted steam goes into a condenser where it is recondensed back into water and sent back to the boilers. There is some loss during the process, so the Iowa-class requires its evaporators to continue making more fresh water to replenish the boilers. The Iowa class have three evaporators on board which make a combined total of 60,000 gallons per day of fresh water.
After the boilers have had their fill of water, the remaining fresh water from the evaporators is fed to the ship's potable water systems for crew drinking, showers, hand washing, cooking etc. All of the urinals and all but one of the toilets on the Iowa-class flush with salt water in order to conserve fresh water.
The turbines, especially the HP turbine, turn at high speeds, much higher than you want to try to feed back to the screws. In order to reduce those RPMs to a more managable rate the shafts that come out of the turbines go into a set of reduction gears which reduce the 2000+ RPM speeds down into a more managable rate, generally in the under-225 RPM rate -- depending upon the desired speed of the ship.
Electricity
Modern warships are heavily dependant upon electricity and the Iowa-class are no exception. Much of what happens on the ship, including rotating the turrets and elevating the guns, is done by electric motors. To generate electricity each of the four engine rooms has a pair of Ship's Service Turbine Generators (SSTGs) manufactured by Westinghouse. Each SSTG generates 1,250 Kilowatts of electrical power for a total of 10,000 KW of electricity. The SSTGs are steam powered and get their steam from the same boilers that feed the engines.
For backup the ship also has a pair of 250 Kilowatt diesel generators.
During battle it is possible that your electrical circuits could be damaged and so it is essential to be able to repair or work around that damage as quickly as possible in order to restore electrical power to crucial systems. To that end throughout the lower decks of the ship there is a Casualty Power System consisting of large 3-wire cables and wall outlets called biscuits which the cables plug into. By using these cables electrical power can be dynamically rerouted around damaged circuits and electrical power restored to the ship if necessary.
Armament
The Iowas were among the most heavily armed ships the United States ever put to sea and over time their armament evolved to keep pace with the times.
Main Battery
The primary armament of the Iowa-class battleships are their nine 16", 50 caliber, guns located in three, 3-gun, turrets -- two forward and one aft. The guns are 66 feet long each, with approximately 43 feet of it protruding from the front of the gun house, and each gun weighs approximately 239,000 pounds. For perspective that is roughly the weigth of a space shuttle; so the Iowa-class ships are carrying the weight of 9 space shuttles just in the guns.
The gun house that is visible above deck is only the very top of the turret. The turret extends either 4 decks (Turrets 1 & 3) or 5 decks (Turret 2) beneath the main deck. The lower spaces contain projectile handling rooms and a powder handling room where the powder bags used to fire the guns are stored. One interesting fact about the turrets is that they are not actually attached to the ship. The turrets are simply sitting on rollers which means that if the ship were to capsize the turrets would fall out. For a good demonstration of this see the recent underwater photos of the Bismarck which show her barbettes empty because her turrets fell out as the ship sank.
The turrets are 3-gun turrets and not triple turrets because the guns can be elevated independently. The guns can also be fired independently if desired; the ship could fire any combination of its 9 guns, including all 9 at once which is known as a broadside.
Contrary to popular myth, the ship does not move sideways when a broadside is fired. The Iowa-class battelships displace 58,000 tons and draft 38 feet of seawater. It is way too much mass to move sideways just by firing the guns. For a more scientific exploration of this subject, see the link below in External Links.
The guns can be elevated from -5 degrees to 45 degrees depending upon the range to the desired target and they elevate at 12 degrees per second.
The turrets can be rotated through approximately 300 degrees at approximately 4 degrees per second and can even be fired back beyond the beam which is sometimes called over the shoulder. In fact the guns are never fired directly forward.
Secondary Battery
The secondary battery of the ship consists of 5" 38 caliber guns in a series of twin mounts. Originally the secondary battery was intended to be part of the anti-aircraft defenses, but as aircraft got faster and faster their effectiveness in that role decreased. By the time of the Gulf War the secondary batter was largely relegated to shore bombardment and littoral defense.
Until the modernization in the 1980s there were ten twin mounts, five on each side of the ship. In the modernization the aft-most two mounts from each side were removed to make room for the missiles leaving the ship with just 6 twin mounts.
The guns have a effective range of 9 miles and can be fired as fast as the crew can load and fire them. A good crew could run 16 to 23 rounds per minute through them.
Anti-Aircraft
The British attack at Taranto and the Japanese attack at Pearl Harbor made it clear that airpower was going to play a substantial role in the war. The Iowas were designed to be a fearsome anti-aircraft platform. When launched they carried twenty quad-40mm Bofors mounts, and forty-nine 20mm single mounts.
By the end of WWII the single 20mm had stopped being a very effective anti-aircraft weapon, it just didn't have enough punch to stop the bigger, heavier aircraft they were seeing and in particular the kamikazes. By 1950 almost all of the single 20mm guns had been removed.
In the modernization in the 1980s they realized that all of their enemies today are going to be flying jets and it's awfully difficult to shoot down a jet with a 40mm anti-aircraft gun so all of the 40mm gun mounts and the last of the 20mm guns were removed in the modernization. In their place the Navy installed four of the Phalanx Close-In Weapons Systems or CIWS.
Missiles
During the modernization in the 1980s three important weapons systems were added to the Iowa-class battleships. The first was the CIWS anti-aircraft/anti-missile system discussed immediately above. The other two were missile systems for use against both land and sea targets.
AGM-84 Harpoon
The Iowa-class were fitted with an anti-ship cruise missile, the AGM-84 Harpoon in 16 launch tubes. The tubes are located alongside the aft stack with 8 on each side of the ship in two pods of four.
The Harpoon has a range of up to approximately 85 nautical miles depending upon how you fire it.
BGM-109 Tomahawk
For increased range and accuracy against land targets the Iowa-class gained 32 BGM-109 Tomahawk missiles located in 8 armored box launchers. The TLAM or Tomahawk Land-Attack Missile was used extensively in the Gulf War by USS Missouri and USS Wisconsin.
Class History
The Iowa class was the last battleship line built by the United States before switching over to an aircraft carrier based navy. The Iowas were unique for several reasons. First, these ships were designed as "fast" battleships. Secondly, all of them were designed to fit through the Panama Canal with less than a foot to spare on either side. Third, all four of the Iowa class battleships were recommissioned and refitted under the Reagan administration as part of Reagan's "600-ship Navy" plan, particularly in response to the Soviet Navy commissioning the Kirov class. Fourth, these ships actively participated in the U.S. Navy thoughout the latter half of the twentieth century. Lastly, all four of the ships are still in existence, which is unusual because the Navy usually uses derelict ships to test weapons on before scuttling them or selling them for scrap.
External Links
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