The U.S. Navy is slowly preparing the first of its massive, 15,500-ton Zumwalt-class stealth destroyers for sea next year. But questions remain about many of the technologies onboard the new ships. First and foremost: can the thing even stay afloat?
The vessel—which is the largest American surface warship since the 1950s--brings a new untried “tumblehome” hull design, new power systems and gun technology that have not been used on a modern warship before. The ship is highly automated with a crew of just 142 -- compared to older ships that have a complement of about 300. But despite its massive size, the stealthy warship appears on an enemy’s sensors as something no larger than a small fishing boat.
The 600-foot long ship is armed with 80 missiles tubes, two massive 155mm guns that can lob guided shells 80 miles away and a pair of 30mm guns for self-defense. Theoretically, the ship can take on all comers in the air, sea, underwater or on land. In the future, the ship could be fitted with futuristic lasers and electro-magnetic rail-guns too. Additionally, the so-called DDG-1000 can also carry either a pair of helicopters or a single helicopter and a trio of drones.
But it all comes at a steep price—the first two ships cost $4.2 billion dollars each while the third costs $3.5 billion. The DDG-1000 is so expensive—and there are so many doubts about its technology—that the Navy is building only three of the ships before in favor of buying an improved version of its older Arleigh Burke-class destroyer.
One those doubts includes a potential Achilles’ heel –the ship’s bizarre stealthy hull—which is the most obvious new feature of the new destroyer. The hull looks like it is upside down. Unlike a normal ship, the bow slopes upward from the water up to the deck. Meanwhile, the rest of hull is wide at the waterline and slopes inward. If one were to look at the ship directly from the front, it would resemble a bell rather than the traditional “flared hull” with a V or U shape that is most common. There have been persistent concerns about how stable the tumblehome design is in any sort of rough seas—in fact, one of the concerns about the design is that it could capsize if it is hit by a large wave from the wrong angle. “This is an area that the Navy is taking seriously,” one naval architect familiar with the design told The Daily Beast.
The Navy declined requests for interviews—and would not directly address the issue. However, slides presented by the Naval Sea Systems Command in April show that the service has not yet completed certifying the hull for stability. The Navy recently upgraded a maneuvering and sea-keeping lab facility in Carderock, Md., where the ship’s design is being tested. “This is a high priority for that facility,” the architect said.
There might be reason for concern. A 2007 engineering paper presented at the 9th International Ship Stability Workshop in Hamburg, Germany, shows that tumblehome designs are more prone to capsizing especially went the ship is hit from behind. “The number of capsizes for the most- probable sea state 8 [30 to 46 ft waves] conditions increased drastically for the tumblehome topside for following, stern-quartering, beam and head seas,” the report reads. “The capsize risk for the tumblehome geometry had a greater increase for small increases in KG [center of gravity] than the flared topside geometry.”
However, there has been a lot of work done since the report was released, the naval architect said. The tests in the study assumed that the ship would displace about 9690-tons; the Zumwalt is a 15,500-ton vessel. “Sea-keeping performance improves with increasing displacement and since the DDG 1000 is significantly bigger than this, that would improve the results,” the naval architect said. “I would expect that as the design evolved and more knowledge was gained from tests and analysis, the hull form would be modified to improve the sea-keeping performance.”
Either way, the Navy is proceeding full steam ahead in preparing the DDG-1000 for sea. Late last month, the Navy activated the Zumwalt’s enormous Rolls-Royce MT-30 and RR450 gas turbine engines as it started testing of the ship’s unique “integrated power system”—which dispenses with having the engines connected directly to the propeller and instead turns an electric motor.
Unlike a normal warship, where the gas turbine engines are connected to directly to the propellers, the Zumwalt uses an entirely new concept. The engines actually turn generators that produce a total of about 80 mega-watts of electrical power that supplies the vessel’s electrical grid. A portion of that electrical power is then used to turn the ship’s propellers using advanced induction motors—which are spun using electromagnets. The motors are powerful enough to push the massive warship along at better than 30 knots.
That might not seem like a big deal, but the using the engines to generate electricity instead of directly driving the ship frees up a lot of juice for future weapons like lasers and rail-guns from some sort of science fiction movie. In the meantime, the ship is equipped with the range of missiles carried by Navy warships.
One thing the ship won’t be able to do is defend against ballistic missile attacks—which is one of the reasons the Navy ditched the design in favor of the older Burke-class design. While the ship’s AN/SPY-3 radar is capable, it does not operate in the proper frequency band for that mission.
That’s a major deal. There’s a rising threat of ballistic missiles in the West Pacific, where China is deploying such weapons. Ultimately, the changing threat and enormous price tag doomed the program and only three ships will be built at exorbitant cost.