South Dakota class battleship (1939)

Construction of the second "South Dakota"-class began shortly before World War II. Built with Fiscal Year 1939 appropriations, they were more compact and better protected than the preceding sclass|North Carolina|battleship|0, but had the same main battery of nine 16 inch (406 mm) 45-caliber guns in triple turrets. Commissioning through the summer of 1942, the four ships served in both the Atlantic, ready to interdict possible German capital ship sorties, and the Pacific, in carrier groups and shore bombardments.

Design

The South Dakotas achieved the remarkable goal of a 35,000 ton 'Treaty' ship mounting a main battery of nine 16 inch guns, with reasonable speed and 'balanced protection' (meaning that the armor could withstand fire from the ship's own main battery). This was accomplished in part by an unusual armor configuration, and by shortening the hull as much as possible - thereby reducing the length of armor required to cover it.

The "South Dakota"s innovative hull design featured an internal armor belt, to protect the ships' vitals against 16 inch (406 mm) shells, improved anti-torpedo side protection, and outboard propeller shafts that extended further aft than the inboard ones. The armor later came into controversy when it was maintained by some that underwater protection against torpedoes was compromised.

While the shorter hull minimized the amount of armor needed to meet the requirements without exceeding the tonnage demanded by the Second London Naval Treaty it also resulted in a smaller length-to-beam ratio that negatively affected speed and endurance. To achieve the desired 27 knots (50 km/h) the machinery was designed to produce 9,000 horsepower (7 MW) more than that of the "North Carolina"-class, no small feat considering the equipment had to be compact enough to fit within a smaller hull.

Compared with her three "sisters", "South Dakota" had extra command facilities and 40mm AA mounts in exchange for two fewer 5 inch (127 mm) twin gun mounts, as a weight-saving measure.

Armor

The "South Dakotas" have an internal main belt, a change from the previous two sclass|North Carolina|battleship|0. While an internal belt is difficult to install and repair, it was reluctantly accepted because an external belt that could ward off 16-inch shells would have required a belt incline of 19° and a beam too wide for the Panama Canal.cite web |url=http://www.battleship.org/html/Articles/IowaClass/Armor.htm |title=Iowa Class: Armor Protection |accessdate=2007-03-14 |publisher=Iowa class preservation society]

The underwater armor includes side protection and a triple bottom, both multi-layered systems designed to absorb the energy from an underwater explosion equivalent to 700 pounds of TNT — the Navy's best guess in the 1930s about Japanese weapons. But unbeknownst to U.S. Naval Intelligence, the Japanese 24-inch-diameter "Long Lance" torpedo, carried a charge equivalent to 891 pounds of TNT.

Each side of the ship is protected by one tank mounted outside the hull and loaded with fuel oil or other liquid ballast, and an empty inboard tank, all running from the third deck to the bottom of the ship. The liquid tanks are to deform and absorb the shock from the explosion and contain most of the shards from the damaged structure. The inner void is expected to contain any leakage into the interior ship spaces. The armor belt is designed to stop fragments that penetrate the second torpedo bulkhead; however, tests in 1943 showed structural defects in the system.

The follow up sclass|Iowa|battleship|0 retained a similar protection scheme; both the "South Dakota"- and "Iowa"-classes were adequately protected against the 2,240 lb (1,016 kg) Mark 5 shells that their 16-inch guns were originally designed to fire (the "North Carolina"-class was only designed to be proof against 14-inch shells), though not the "super-heavy" 2,700 lb Mark 8 shells that all three classes actually carried during the war.

ervice

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In 1942 and 1943, they stood guard in the Atlantic against possible sorties by German battleships, took part in the invasion of North Africa and in operations around Guadalcanal. USS "Massachusetts" supported Operation "Torch" and used her 16-inch guns to disable the French battleship "Jean Bart" and sink two destroyers, the only time that a US battleship had ever fired its main batteries at an Axis ship in Europe.

At the Battle of the Santa Cruz Islands, "South Dakota" was credited with downing 26 to 32 Japanese planes. During the Second Naval Battle of Guadalcanal, "South Dakota" was damaged in a gunnery engagement with a Japanese force involving the sinking of the battleship "Kirishima".

As the US went on the offensive in the Central Pacific, they joined in escorting the fast carrier task forces, a job for which speed and their heavy anti-aircraft gun batteries were well-suited. They also employed their main battery guns in shore bombardment, and were kept ready to form battle line in case their Japanese opposite numbers should appear.

Post War

All four "South Dakota"-class battleships went into reserve soon after World War II and saw no further active service. Being valuable, large ships, they were considered for many conversion schemes, including guided missile battleships and satellite control ships, but all were eventually discarded in the early 1960s. Their speed (27 knots, versus 32-35 knots for the sclass|Iowa|battleship|0 and virtually all new fleet carriers of the World War II era) worked against their retention.

USS|Massachusetts|BB-59|2 and USS|Alabama|BB-60|2 became museum ships. USS|South Dakota|BB-57|2 and USS|Indiana|BB-58|2 were scrapped. "Massachusetts" is in Fall River, Massachusetts, and "Alabama" is in Mobile, Alabama.

References

External links

* [http://www.navsource.org/archives/01idx.htm]