On Monday, April 12th, the US Navy christened the first of the three planned Zumwalt-class destroyers. The vessel will be delivered to the Navy later this year, and should enter the Pacific fleet in another two years. Then, and only then, will the Navy learn whether this new hull design is a triumph or a disaster.
The Zumwalt class destroyers are meant to supplement, not replace, the Arleigh-Burke class. At present, there are plans to build only three, and the home port for all three will be San Diego. These are special-purpose ships, designed to be stealthy, with the capability of operating in littoral (shallow, roughly 60′ or less) waters. Their focus will be on getting in close to shore undetected in order to support special forces operations and to conduct bombardment of targets along the coastline, as well as the traditional destroyer function of attacking enemy shipping. After becoming fully operational, they are expected to spend a lot of time patrolling the East and South China Seas, the contested zone between mainland China and Japan, in order to monitor the growth of the Chinese Navy and their territorial ambitions in the region.
The Zumwalt class is big. At 610-feet, they are better than 100-feet longer than the current Arleigh-Burke class of destroyers, and about 50-feet longer than the older Spruance class. They are even slightly larger than the Ticonderoga class of cruisers. Although displacing 15,000 tons, the ship draws only 28-feet of water, two feet less than the Burke class. And, despite it’s size, the crew will number only 142 officers and men, about half of what an Arleigh-Burke class destroyer needs.
The armaments of the Zumwalt and each of her two sister ships will eventually include two of the Navy’s 6″ Advanced Gun System, an electromagnetic rail gun that will fire rocket propelled warheads at 5,000-mph plus out to a range of over 60 miles, with a rate of fire of ten rounds per minute. She will also be equipped with laser weapons. A related feature incorporated into the Zumwalt class is the ability to take on water ballast, which can lower the ship deeper into the water in order to add vertical and lateral stability when the gun battery is being used.
Both of these weapons systems are still in the last stages of development and will not be installed for another two years or so. When they become operational, however, they both will require a great deal of electricity. On top of that, the Zumwalt class ships all employ electric propulsion. To handle this mammoth electrical generation requirement, these vessels will be equipped with generators powered by two 40-megawatt gas turbines and two 78-megawatt gas turbines, which adds up to about 318,000-horsepower. By comparison, the powerplants in the Arleigh-Burke class developed about 108,000-horsepower. The combination of gas turbines driving electric motors is expected to produce a level of operational quietness that approaches that of modern nuclear submarines. One of the measures that will be used to dissipate the heat from the gas turbines is “sleeting”, in which water is taken in from below the waterline and then pumped out onto the outer hull plates in a sort of continuously cascading “waterfall”, a technique made possible because of the tumblehome hull.
The Navy intends to be slow and cautious in bringing the Zumwalt into 
front-line duty, partly because it is the first of a new class of ship, and partly because of it’s controversial hull design. As can be seen in the photo above, the Zumwalt’s waterline to weatherdeck form is opposite of conventional ships. It has a “tumblehome” stern, as well as what can be termed an overall tumblehome contour. The difference is illustrated in the graphic at upper left. While this design has been used before by the 19th century Russian and French navies, it was associated even then with instability problems. Seven years ago, when news of the Zumwalt-class hull form first became public, the online Defense Industry Daily newspaper questioned it’s suitability, HERE, by writing this excerpt:
“At least eight current and former officers, naval engineers and architects and naval analysts interviewed for this article expressed concerns about the ship’s stability. Ken Brower, a civilian naval architect with decades of naval experience was even more blunt: “It will capsize in a following sea at the wrong speed if a wave at an appropriate wavelength hits it at an appropriate angle”… “
“…Brower explained: “The trouble is that as a ship pitches and heaves at sea, if you have tumblehome instead of flare, you have no righting energy to make the ship come back up. On the DDG 1000, with the waves coming at you from behind, when a ship pitches down, it can lose transverse stability as the stern comes out of the water – and basically roll over.”
So, triumph or disaster, only time will tell.