The Navy May Use One Hull Design To Replace Its Cruisers And Some Destroyers
There's nowhere left to go with the Arleigh Burke design, meaning the service will have to find a new ship to meet its energy-hungry demands.
The U.S. Navy says that it has likely hit the limit of what it can do with the Flight III Arleigh Burke destroyer design and isn’t sure if the hullform will be a useful starting place in any way as it begins developing a follow-on class of ships. This could have ramifications for the final shape and construction of the service’s future Large Surface Combatant, a prospective design packed with energy-hungry advanced radars and other electronics, directed energy weapons, and railguns, which could eventually replace both its older DDG-51 Arleigh Burke-class destroyers and its Ticonderoga-class cruisers.
On July 11, 2018, U.S. Navy Rear Admiral William Galinis, head of the service’s Program Executive Office Ships, offered these and other new details about the project at a Navy League-hosted breakfast. The Large Surface Combatant, or LSC, is part of a broader fleet transformation effort that also includes the Navy’s future frigate, also known as FFG(X), and unmanned surface vessels.
“It’s going to be more of an evolutionary approach as we migrate from the DDG-51 Flight IIIs to the Large Surface Combatant,” Galinis said. With those most recent Arleigh Burkes, “you kind of get to the naval architectural limits of the DDG-51 hullform.”
The Navy chose the Flight III Arleigh Burke design after it decided to dramatically cut its planned purchases of the more advanced DDG-1000 Zumwalt stealth destroyer. These new ships will be substantially more capable than their predecessors thanks to the addition of the AN/SPY-6(V)1 Air and Missile Defense Radar (AMDR) and associated upgrades to the ship’s overall combat system.
But the hull is also longer and stronger and the deckhouse is beefier to accommodate the upgrades and the additional power generation requirements. In total, nearly 50 percent of the technical drawings associated with the ship needed changes as part of the update. At present, the Navy has 64 Arleigh Burkes in various configurations in service. There are nine additional ships, all Flight IIA types, under construction. The service expects to take delivery of the first Flight III ship in 2023.
“That’s going to bring a lot of incredible capabilities to the fleet but there’s also a fair amount of technical risk,” Galinis said at the Navy League breakfast. The Rear Admiral said that this was an important reason for the Navy to pursue an evolutionary approach to the LSC, which could leverage existing systems to help keep costs as low as possible.
The problem, as the officer noted, is that the Flight III program seems to have found the basic structural limits of the existing Arleigh Burke design. It’s not clear how useful the hullform or experience with its construction would necessarily help if the Navy decided to pursue a clean sheet-ship design for the LSC, either.
It wouldn't be the first time the service has run into these issues, either. The Ticonderoga-class cruisers, which the new ships are also set to replace, use a hullform based on the now-retired Spruance-class destroyer design. The cruisers' hulls were effectively overloaded and their aluminum superstructures became a source of persistent and costly cracking under the weight of the Aegis radar system as time went on.
“Do we use the DDG-51 hull form and maybe expand that? Do we go with a new hull form?” Galinis added, rhetorically. “[We] start with a DDG-51 flight III combat system and we build off of that, probably bringing in a new HME [Hull, Mechanical, & Engineering] infrastructure, a new power architecture, to support that system as it then evolves going forward.”
The power architecture question will be critical in the future to support further improved radars, communications equipment, and data links. If the Navy does plan to replace Arleigh Burkes and Ticonderogas with a common design, or at least a hullform with any significant commonality, then the design will have to be able to accommodate the systems necessary to support a wide range of offensive and defensive functions.
The video below gives a good overview of how the AN/SPY-6(V)1 AMDR on the Flight III Arleigh Burke-class ships works.
These would include extensive air and missile defense capabilities, as well as the cruiser's typical role as a battle management nerve center for Carrier Strike Groups and other surface task forces. Any future ship will also need to be able to run the data links associated with the Navy’s broader push network together all of its surface ships, submarines, and aircraft, as well as share information with platforms from other services and allies and facilities ashore.
Power demands will only increase even more as the Navy pushes ahead in developing directed energy weapons, including solid-state lasers, high powered microwaves, and electromagnetic railguns. The service plans to begin outfitting existing DDG-51s with the 60-kilowatt Surface Navy Laser Weapon System (SNLWS), a close-in defense weapon for destroying small drones, as well as light manned and unmanned watercraft, in 2020, which could help expose any potential issues. An existing prototype 30-kilowatt Laser Weapon System (LaWS) is on board the USS Portland, a San Antonio-class landing platform dock.
“We’re still working through what that power architecture looks like,” Galinis explained. “Do we stay with a more traditional [gas-driven] system… or do we really make that transition to an integrated electric plant – and at some point, probably, bring in energy storage magazines…to support directed energy weapons and things like that?”
An integrated electric propulsion system typically involves some combination of fossil-fuel powered turbines and generators that in turn drive electric motors to move the ship and power its onboard systems. In addition to being more efficient and potentially having lower operating costs, in part due to the elimination of long drive shafts and other complex mechanical linkages, these systems can also be more compact, freeing up hull space for other requirements and making the overall internal arrangement more user-friendly.
Unfortunately, they’ve also proven to be finicky and complex in their own ways. The Navy has already abandoned a plan to install this type of power architecture in existing Arleigh Burkes after disappointing tests on the USS Truxtun, which could be yet another strike against using any part of the hullform for a future LSC.
The prototype system reportedly could barely handle the demands of the existing Aegis radar system and running the motors propelling the ship at the same time. “At that point you are a light switch flipping on away from winking out the whole ship,” an unnamed Navy official told Defense News' David Larter in March 2018.
If the Navy can’t use the Flight III DDG-51s as a starting place for the new LSC, it has limited options if it truly wants to stick to its evolutionary approach rather than commission an all-new class of ships. This is something the Navy’s top officer, Admiral John Richardson, said was an essential part of the LSC program in an interview with Defense News in April 2018. Power generation was another.
There are very few suitably large surface combatant designs in production either in the United States or among its allies that could serve as the basis for its new ships without serious modification. Beyond the Arleigh Burke-class, there is the San Antonio-class. Shipbuilder Huntington Ingalls has pitched as a possible air and missile defense platform, along with a host of other configurations.
Another option might be a design based on BAE Systems Type 26 City-class for the Royal Navy, which, while described as a frigate, is almost as long as first generation Arleigh Burkes and will displace nearly as much as those Fight I ships with a full combat load. BAE has its own working relationship with the Navy, having gotten contracts to do more limited upgrade and maintenance work on the existing DDG-51s.
Unfortunately, the San Antonios, in their present configuration, are far too slow to keep up with a Carrier Strike Group. And if the Arleigh Burke design is maxed out in terms of power generation capability, it seems unlikely that the smaller Type 26 hullform would be any better able to handle these growing demands. Either option would almost certainly require significant modifications to be a viable basis for the LSC, which could be a costly endeavor.
But the Navy’s power demands, present and future, could actually cause them to revisit the DDG-1000 Zumwalt stealth destroyer design. It is the only design in production that fits the basic LSC description and has the desired power generation capabilities.
This choice would be somewhat ironic given that the Navy developed the Flight III Arleigh Burke design after it decided to dramatically cut its planned purchases of Zumwalts. But it too could come along with its own problems.
For one, the ship has an exotic and complex hullform that Bath Iron Works designed with stealth in mind. Its tumblehome design already presents stability concerns in rough seas, which could limit the ability of any ship based on the design to operate under those conditions. Carrier Strike Groups have to travel anywhere and a future LSC based on the Zumwalt design might not be able to accompany the other ships in certain circumstances. This, in turn, could fur force the flattops to delay their arrival time on station or continue on without a full complement of escorts.
The hullform could also limit how readily adaptable the design might be to meet Admiral Richardson’s third goal for the future surface ships, modularity, or any other LSC requirements, an issue that our own Tyler Rogoway examined in detail in the past.
The DDG-1000’s integrated electric propulsion system is the core of its impressive power generation capabilities but has had some troubles, too. A harmonic filter, which acts as a large surge protector to prevent damage from unintended power fluctuations, on board the second Zumwalt, DDG-1001, the future USS Michael Monsoor, failed on the first day of sea trials in December 2017, sending the ship back to port.
The ship then suffered damage to the blades in one of its main Rolls-Royce MT30 turbines during acceptance trials, which wrapped up in February 2018. DDG-1001 now needs a replacement turbine and was still pier side in Bath, Maine waiting for repair as of July 11, 2018.
It remains unclear whether these issues are isolated to this particular ship, though. The Zumwalt has not experienced any similar issues and the MT30 is widely used, including on the Navy’s Freedom-class Littoral Combat Ships. We don’t know if this same problem has shown up persistently in any of the other ships that use this engine.
The exact sort of ship the Navy wants probably won’t be clear until it firms up its requirements for the design. Rear Admiral Galinis said that his office hoped to begin reaching out to industry for some feedback on their initial plans before the end of 2018.
“We’re going to have the requirements discussion with Navy leadership and then we’re going to want to engage industry as we start thinking about what options might be available,” Galinis said. “Frankly, industry’s probably best suited to try to help us with the technology piece, especially if we start thinking [that] we want an innovative electric plant.”
The real question then will be if vendors can offer a variant or derivative of an in-production ship that meets those needs. If the Navy is truly interested in a common ship to replace the Ticonderogas and at least some of the existing Arleigh Burkes, an all-new hullform may be necessary and would make sense in the long term.
A clean-sheet design could give the Navy an opportunity to choose a ship that has better growth potential and will be better able to accept upgrades and additional systems in the future. Any existing design will be more limited in this regard just like the Arleigh Burke and the only one that seems at all to be a workable starting place is the Zumwalt, which may not be a cost-effective option.
If the Navy does find itself forced to go with an entirely new class of ships, though, it could easily be an expensive and time-consuming experience. The service is right to make sure it has its requirements ironed out first and then see what its available options might be, especially when considering its recent track record of procuring advanced surface ships.
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