Naval Sea Systems Command (NavSea) has stepped up the pace of developing and testing power generation and management technologies for surface ships and submarines, following the release in June 2019 of the Naval Power and Energy Systems Technology Development Roadmap.
The roadmap identifies the obstacles to greater shipboard power-generation capability to support advanced weapons (such as electromagnetic railguns and lasers) and large sensor systems, especially the SPY-6(V) air- and missile-defense radar. Raytheon is building the SPY-6(V) for fielding on Flight III Arleigh Burke–class destroyers, with variants planned for the future frigate and Gerald R. Ford–class carriers. All of these, the study says, demand leaps forward in technologies for energy storage, power conversion, prime movers, power distribution controls, and rotating machinery.
Vice Admiral Thomas Moore, NavSea commander, says the roadmap “aligns electric power and energy system development with increasing warfighter power needs. . . . Fundamentally evolving the system requires an exceedingly careful and thorough . . . development process.”
“Power and energy systems” represent an expansion of the Navy’s quest for efficient, affordable shipboard power architectures that encompass concepts referred to for decades as “electric drive.” In the mid-1980s the Navy unveiled a “Revolution at Sea” initiative that it said aimed at radically new ship designs for the 21st century. In September 1988, Chief of Naval Operations Admiral Carlisle A. H. Trost told the Navy League, “Integrated electric drive [IED], with its associated cluster of technologies, will be the method of propulsion for the next class of surface battle force combatants.”
The 1990–94 shipbuilding plan anticipated IED entering the force with DDG-82, planned to be the first Flight III ship in the Arleigh Burke class. (As things have turned out, the first Flight III ship will be DDG-125, the Jack H. Lucas.)
Through the 1990s, work at Navy labs and in industry homed in on components that could function as IED architecture, including digitally controlled power- conversion modules, permanent-magnet motors, and new switches, among others. In the late 1990s, NavSea’s Integrated Power Systems program office developed management architecture. The NSWC Carderock Division in 1998 demonstrated a power converter using software-controlled power electronic building blocks, based on work sponsored by the Office of Naval Research.
In January 2000, then–Navy Secretary Richard Danzig announced that the planned DD-21 land-attack destroyers, which became the Zumwalt-class, would be powered by integrated electric drive. He declared that the system represented a “fundamental change of direction” for the Navy comparable to the shift from sail to steam power.
Not all the work was successful. The Navy struggled to manage a so-called “Smart Ship” initiative for the Ticonderoga-class cruisers aimed at integrating new damage-, machinery-, and fuel-control systems, and integrated condition assessment. The work, started in 1996 on board the USS Yorktown (CG-48) with Litton Integrated Systems as integrator, fell far behind schedule and over budget. The Navy gave the work to Northrop Grumman, which then acquired Litton.
But the Navy pushed on, through production of a hybrid-electric drive (HED) system (combining gas turbines, electric motors, motor drives, control software, and other components) for installation on 36 Arleigh Burke–class destroyers. In 2012, L-3 Communications won an award for two prototype systems, with options for follow-on production of two shipsets that the Navy exercised in 2015.
The HED uses electric drive motors fitted to the propeller shaft reduction gears and powered by the same generators that power ship’s services. At low speeds, the system is considerably more efficient than the gas turbines used at higher speeds. The Navy fielded an HED system on board the USS Makin Island (LHD-8)—the only LHD not powered by diesels—and America (LHA-6). The future Tripoli (LHA-7) also has an HED.
As Danzig anticipated, the three Zumwalt-class DDGs are the first IED-powered ships. They have an integrated fight-through power system that distributes propulsion and ship systems’ energy from four Rolls-Royce gas turbines generating 78 megawatts of power, using advanced induction motors to turn the drive shafts.
“The key to future success is continued close engagement between government, academia, and industry,” says Stephen Markle, NavSea’s Electric Ships program office director. “The [roadmap] is our guidebook.”