DD-21
In 1997, plans for the Littoral Combatant (3B1) were revived under the SC-21 banner. It was initially renamed the Power Projection Ship, and then DD-21, Destroyer for the 21st century. Influenced by the Arsenal Ship, it would have a stealthy hull with a significant land attack capability. At first the plan was to install a twin-barreled Vertical Gun for Advanced Ships (VGAS), developed from experiments on advanced projectiles for the Iowa battleships, but this was dropped in favour of a conventional 5" gun and two 64-cell VLS. It would also feature a revolutionary cross-layer active sonar. An Operational Requirements Document was signed in November 1997, and an Advanced Development Memorandum on 11 December. A Program Executive Office was established on 25 February 1998. As with the Burke class, the construction of the DD-21 ships would be split between Bath Iron Works and Ingalls to preserve the industrial base. However there would be a competition between the two yards to design DD-21 and to be the full-service contractor for the class, which would mean the winning team receiving 85% of the total program costs of around $70 billion. BIW partnered with Lockheed Martin as the combat system designer and integrator, forming the "Blue" team; Ingalls partnered Raytheon in the "Gold" team.
The new design was compared to the current Burke hull and possible developments of it, and it was decided to go ahead with a new hull to be called DD-21 (or DD 21), the 21st century Land Attack Destroyer. The new hull was judged to have more potential for stealth and reductions in manning than the Burkes. This was important, as one aim of the program was to reduce manning and operational costs by 70%, while providing scope for a follow-on cruiser class. On 4 July 2000 it was announced that the lead ship of the class would be named after Admiral Elmo Zumwalt, who had died earlier that year. The name would be inherited by subsequent versions of the design, culminating in USS Zumwalt.
The ship's delivery schedule was delayed by a year following the decision in January 2000 to use electric drive in the ship. But by early 2000 a "tumblehome" design had emerged that resembles that of the eventual Zumwalt class, albeit with differences in the weapons carried. Sources disagree on the displacement of the DD-21, and indeed it probably varied during the design process, but around 16,000 tons seems most likely. As of July 2001, 32 DD-21s were planned, with construction planned to start in FY05.
Many of the weapons planned for the DD-21 were to be trialled in existing ships, increasing the land attack capability of the existing fleet in FY05 before the delivery of DD-21 in FY10. Rocket-boosted Extended Range Guided Munitions (ERGM) for existing 5"/62 guns would have a range of 63 nautical miles (117 km), while the long-range Block IV Tactical Tomahawk missile could be fired from existing Mk 41 vertical launching systems. It was also planned to turn old Standard Missile SAMs into Land Attack Standard Missiles (LASM) with 150 nautical miles (278 km) range.
Initially it was planned to use the Vertical Gun for Advanced Ships (VGAS), but this was abandoned in favor of a more conventional Advanced Gun System fore and aft, each with a separate magazine of 600-750 rounds. The guns would fire a 155 mm version of the ERGM which would double the payload and increase the range to 100 nautical miles (185 km). Together the two guns would give the ship a rate of fire of 24 rounds/minute, giving them the throw weight of two 6-gun 155 mm artillery batteries. Precision munitions make gunfire three times more effective than unguided shells, hence the DD-21 was said to have the destructive power of six batteries. The Navy's goal was to have 256 VLS cells on the DD-21, but the final number may have been 128 - some sketches show missiles being launched from fore and aft but the aft launchers appear to have been replaced by a second gun system and/or a helicopter pad. As well as LASM and Tactical Tomahawk, the DD-21 would receive the Advanced Land Attack Missile (ALAM), a new missile with a variety of warheads and a design range of up to 300 nautical miles (556 km).
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