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Des Moines Class Heavy Cruiser

Des Moines in 1948
Des Moines in 1948
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Ship Builder Laid Down Launched Completed Fate
CA134 Des Moines Bethlehem, Quincy 28 May 45 27 Sep 46 16 Nov 48 Stricken 1 Jul 1991
CA139 Salem Bethlehem, Quincy 4 Jul 45 27 Mar 47 14 May 49 Stricken 1 July 1991, now a floating museum
CA140 Dallas Bethlehem, Quincy 15 Oct 45 not launched Cancelled 6 Jun 1946
CA148 Newport News Newport News 1 Oct 45 6 Mar 48 29 Jan 49 Stricken 31 Jul 1978

Displacement: 17,255 tons/17,531 tonnes (standard); 20,934 tons/21,268 tonnes (full load).
Length: 716ft 6in/218.39m (oa); 700ft/213.36m (wl).
Beam: 75ft 4in/22.96m; Draught: 26ft/7.92m (mean).
Machinery: 4-shaft General Electric geared turbines; 4 Babcock & Wilcox boilers.
Performance: 120,000shp=33kts; Bunkerage: 3,006 tons oil fuel.
Range: 10,500nm at 15kts.
Protection: 4in-6in main belt; 3.75in main deck; 1in upper deck; 6.3in barbettes; turrets, 8in front; 4in roof, 3.75in sides; 5.5-6.5in pilot house.
Guns: nine 8in (3x3); twelve 5in (6x2); 3in (12x2); twenty-four 20mm.
Torpedoes: nil.
Aircraft: four, two catapults.
Complement: 1,799.

Design

The drawback to the 8in gun was its relatively slow rate of fire, which had proved a distinct handicap in the close-quarters night actions fought in the Solomon Islands. This had led to the diversion of the heavy cruisers to the Aleutian campaign, leaving the fast-moving islands campaign to the destroyers and light cruisers. To redress this defect, a new rapid-fire 8in gun was designed, employing a sliding wedge breech and brass cartridge case. This gun was expected to fire seven rounds per minute, as against three for current guns, and to be fully automatic. Proposed in the spring of 1943, this gun did not become available until towards the end of 1945, eventually emerging as the 8in 55cal Mk 16. Plans to mount this weapon in the Oregon City design came to naught as a result of the extensive design changes found necessary, probably fortunately as it turned out, because the estimated weights of the new triple mounting had been greatly underestimated. Alternative plans to fit a twin turret in four of the CA122 to CA138 series and all of CA139 to CA142 also foundered. Instead, a new design specifically for the rapid-fire triple turret was prepared.

The original design requirements foresaw an improved Oregon City with increased deck armour on the lines of Worcester to give better protection against bombs. The new turrets caused considerable problems in their installation, as they were heavier than anticipated, with larger-diameter barbettes, and needed much larger ammunition spaces for the increased rate of fire. This in turn necessitated an increase in length of the armour belt, which, together with the additional bomb deck, amounted to an extra 695 tons. Further growth caused by increasingly more sophisticated fire controls for the HA function soon led to a projected increase in displacement to 16,000 tons and, later, more.

The hull of the new ship was over 40ft longer than that of the Oregon City, and had an extra 5.5ft of beam. Her displacement as finalised was 19,930 tons. The protective scheme, apart from the introduction of an upper armoured deck designed to trigger bomb fuses before they struck the main armoured deck, was not substantially different from that of the Baltimore. The water-line belt was 6in thick and 10 ft deep, tapering to 4in at its lower edge. The main armoured deck was 3.5in thick, 1in greater than Baltimore, and the upper deck was 1in thick. The armouring of the main turrets was increased on the roofs to 4in, and on the rear to 2in. There were five armoured zones within the hull; armoured bulkheads inside the armoured box to limit damage to adjacent compartments in the event of a heavy hit in any compartment. In all, some 2,189 tons were devoted to protection, or 12.6 per cent of the standard displacement, virtually the same as in Baltimore.

The main machinery remained the standard four-shaft geared turbine installation, but with the designed power remaining at 120,000shp, the maximum speed being reduced to 33.5kts. The boilers and turbines were similar to those of the preceding heavy cruiser. However, the general arrangement of the machinery spaces was different, each of the three forward machinery spaces containing a boiler and a turbine. The fourth machinery unit featured a separate turbine room and fire room, as the three shafts from the forward units precluded any other arrangement.

Her main armament comprised the new 8in Mk 16 gun as mentioned above, mounted in three triple turrets. Each turret weighed 451 tons. The guns fired a 335lb projectile, had a maximum range of 30,050yds at 41° elevation and could load at any angle. The volume of fire was impressive; 90 shells per minute, or 13.5 tons of shells. Training and elevation was electro-hydraulic. The secondary battery was the now-standard six twin 5in/38, but now with four directors. The beam guns were carried on the upper deck, only the centreline mountings being on the superstructure deck.

As originally designed, the light AA battery comprised twelve quadruple 40mm Bofors and twenty 20mm, but by the time the ships were completing it had become obvious that even a 40mm shell had difficulty in stopping a determined kamikaze, while the 20mm had proportionally less effect. As a result, the 40mm were suppressed and 3in/50 twin mountings specified instead, one to replace each quadruple 40mm. The 20mm were initially retained, Des Moines completing with ten twin mountings, but these were quickly landed. Similarly, by the time the ships entered service, the usefulness of catapulted aircraft had passed, and although the lead ship completed with catapults, only one was fully fitted, the other being incomplete. Both were landed shortly afterwards. Salem and her sister never had them.

After some juggling with the cruiser programme, orders were placed for twelve ships in total, of which CA134 was already on order with New York Shipbuilding Corp as a Baltimore/Oregon City type. Her contract was transferred to Bethlehem, Quincy, and reordered on 25 September 1943. CA139 to CA142 had been ordered from Bethlehem as Oregon City Class ships on 14 June 1943, but were built to the new design, while CA150 to CA153 were ordered from New York Shipbuilding Corp. to the new design on 22 February 1945. Three further ships were added; CA143, CA148 and CA149 had originally been programmed as light cruisers, and were ordered from New York Shipbuilding Corp (CA143) and Cramp (the other pair) on 15 June 1943. However, the approaching end of the war caused alterations to the building programmes, and the last four ships, Dallas (CA150) and CA151-153, were cancelled on 28 March 1945. At the end of the war, work was suspended on CA142, CA143 and CA149 on 12 August 1945, but the remaining four continued. (CA140 had now taken the name Dallas in place of the cancelled CA150.) The suspended ships were cancelled at the end of 1945, and CA140, the least advanced of the remaining five, was cancelled on 7 January 1946 to leave a four-ship division. However, on 27 May 1946 a new act allowed only those ships over 20 per cent complete to be finished, and, as Dallas was only some 7.8 per cent complete, she was cancelled on 6 June 1946.

Service

None of this class completed in time for war service, and they entered service well after the end of the conflict. They were extensively used as Fleet Flagships during their careers. None saw service in the Korean War, but Newport News made three tours to Vietnam, where she fired her guns in anger.

Des Moines was decommissioned on 14 July 1961, and Salem on 30 January 1959. Both were finally stricken on 9 July 1991. Newport News, the last heavy cruiser in service, was decommissioned on 27 June 1975. She was stricken on 31 July 1978 and sold to Southern Scrap Metals, arriving at New Orleans, Louisiana, for breaking up in March 1993, and had been virtually finished by the autumn of 1994.

Des Moines was scrapped in 2007, while Salem has been transferred to the US Naval Shipbuilding Museum at Quincy, Massachusetts.

Salem
Salem
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