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CA-134 Des Moines

During World War II American cruisers were designed for two general purposes: fleet support in combination with destroyers, both for defense against hostile destroyers and for torpedo attack on an enemy battle line; and in a combination of independent operations including cruising in hostile waters, raiding, and protecting the long lines of communications across the Pacific. By early 1942 American cruisers screened the first fast carrier raids against Japanese held islands in the Pacific. The cruisers Houston, Marblehead, and Boise fought with the American-British-Dutch-Australian (ABDA) command under Dutch Admiral Karel Doorman in a vain attempt to stop the victorious Japanese advance into the Java Sea in February 1942. In the Battle of Savo Island in August 1942 three American cruisers Astoria, Quincy, and Vincennes as well as the Australian cruiser Canberra were lost in a Japanese night attack.

By 1942 the cruiser had become the principal surface combat ship in the Pacific. In addition to screening the fast carrier attack forces, cruisers carried out gunnery raids on enemy held shores, provided fire support for amphibious operations, and were given many assignments in support of general fleet operations. From her original role as a scout and surface raider, the cruiser became an essential component of task force operations in the Pacific. During the war the United States completed large numbers of cruisers to meet the demands of fleet operations in the Pacific. These ships continued to bear the brunt of the action in the Pacific until the end of the war. The last major combat ship lost by the United States in World War II was the cruiser USS Indianapolis, sunk by a Japanese submarine on July 29, 1945.

The design of the Des Moines class was influenced by the need to build a heavy cruiser with rapid firing 8" guns that could engage and successfully sink Japanese cruisers. In repeated actions, during the early part of the war, American cruisers had found it almost impossible to hit fast Japanese ships in night actions. The navy designed USS Des Moines to solve this problem by providing her with rapid firing 8" guns that would easily outrange Japanese cruisers that mounted 6" rapid fire guns. The Des Moines class was also provided with extensive batteries of antiaircraft guns to provide protection for Essex class aircraft carriers then roaming the Pacific. Des Moines class cruisers were the last class of heavy cruisers designed by the United States during World War II and represent the culmination of wartime cruiser design.

Preliminary design plans for the "CA 139-142, 134 - 8"/55 Rapid Fire Cruisers" - what became the Des Moines (CA-134) class heavy cruiser design -- were prepared by the Bureau of Ships. One plan, dated 1 December 1943, included details on the ship's armor protection and internal subdivision. The original plan was in the 1939-1944 "Spring Styles Book".

CA-134 Des Moines Class was a new heavy cruiser intended to carry the RF 8" gun. Design AA armament was 12 quad 40 mm, 20 20 mm. The main guns were directed by the Mk24 GFCS with Mk13 radar. Mk25/35 radars controlled the 5-inch guns, and the Mk56 GFCS with Mk35 radar controlled the 3-inch/50 AA guns. They were equipped with SPS-6C and SPS-8A surface search radars.

These were the largest American heavy cruisers ever built, 716 feet in length and displacing almost 21,000 tons at full load. They were designed to carry the new 8-inch Mk16 gun which was the first auto-loading 8-inch gun deployed by the US Navy. The rate of fire that these ships could sustain made them more than a match for any contemporary cruiser. The World War II vintage Mark 16 8-inch (203-mm) weapon was found aboard the heavy cruisers of the DES MOINES class. The guns met many penetration, range and rate-of-fire requirements. But because they were in heavy triple turrets, they did not lend themselves to modern naval construction.

The key to the postwar heavy cruiser design was the fully automatic 8-inch 55cal. gun. The Bureau of Ordnance (BuOrd), even prior to the war, had been working on larger guns firing cased ammunition, a 6-inch 47 dual purpose, and later (May 1943) the 8-inch 55. The automatic loading equipment allowed a much higher rate of fire (7 rounds per minute per barrel by design, about twice what previous heavy cruisers could achieve); reloading could occur at any elevation, giving even this major caliber gun a limited antiaircraft capability.

In the design of the new heavy cruiser, both length and beam were allowed to increase to handle the added weight of the new gun turrets and better protection. Power remained the same at 120,000 SHP through 4 shafts, but because the hull was so much larger, it was possible to re-arrange the machinery spaces to have one boiler and one turbine set in each, similar to contemporary battleship practice. Increased length of the hull reduced the wave drag enough that there was little effect on speed in spite of the increase in displacement compared to Oregon City class cruisers. The new machinery arrangement provided increased redundancy with reduced need for cross connects that could be damaged in the destroyer (and previous cruiser) arrangement "in echelon", where boiler rooms and engine rooms alternated (usually, in cruisers, with two turbine sets per engine room).

In addition, subdivision bulkheads within the central citadel were extra-thick at .75 inch and made of STS, highly resistant to splinters. The armor belt was 6 inch to 4 inch in thickness, with 5-inch bulkheads at fore and aft ends of the citadel, and a 3.5 -inch protective deck with, as in US battleships, a 1-inch "bursting deck" over it. Internal subdivision was elaborate even above the V-lines, where an extensive series of fire doors could isolate damaged areas.

Like most World War II cruisers, the aircraft hangar was in the stern to reduce the risk of gasoline-fueled fires such as those that had engulfed many US cruisers in the surface actions of the war. The hangar was accessed through a deck hatch with the aircraft lowered into it by a crane. Two catapults were provided in the original design, but seem never to have been installed. By 1948 the Sikorsky HO3S helicopter had begun to supplement the floatplanes on cruisers and had completely replaced them by 1949. The ships spent most of their sea time using the afterdeck as a boat facility (the aircraft crane served admirably for launching and recovering boats). Scouting functions had shifted to aircraft carriers.

By the time the name-ship Des Moines was commissioned (November 1948), the probability of a surface action with enemy cruisers was very small. However, the three-ship class was admirably suited as fleet flagships and for shore bombardment. All three ships served as flagships of the Sixth Fleet. Only Newport News (CA 148), commissioned in Jan 1949, used her big guns extensively, and that was on the gun line in Vietnam. Newport News and Salem (CA 138) were air conditioned; the name-ship Des Moines (CA 134) was not.

As classic heavy cruisers, these ships displayed superior firepower, speed, seakeeping, and protection. They could have served as anti-surface raider screens for convoys or task forces in World War II type combat, although they lacked the speed to escape from the fastest of WWII battleships at 32+ knots on trials, and could not stand up to a Deutschland or Scharnhorst class surface raider. They did good service as flagships and were effective in shore bombardment, although for that mission it is questionable if the rapid fire feature of their big guns was of much benefit. It should be noted that their ammunition capacity was not enhanced compared to WWII production heavy cruisers. In fact, they were obsolescent at commissioning.

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Page last modified: 22-07-2011 17:36:16 ZULU