LHD 8 - A Step Toward the All Electric Warship

The recently commissioned Iwo Jima (LHD 7) is the last ship with conventional steam propulsion that the U.S. Navy plans to build. The LHD 8 is the next ship of the class and will be built as a modified repeat design of the LHD 7. The key modifications are steam propulsion being replaced with a hybrid propulsion system of main gas turbine engines augmented with auxiliary propulsion motors and electric powered auxiliaries replacing those powered by steam. The LHD 8 will also be the first USN surface ship to implement a 4160 VAC Zonal Electrical Distribution System (AC ZEDS) as well as the integrated power system concept for electrical power generation, distribution and propulsion. These modifications embody the intent of the all electric warship concept for the future U.S. Navy. This paper presents the constraints and issues involved in the design process by addressing major design impacts and significant design concerns. This text explores the design options within the available trade space and illustrates specifically how the Fleet/mission requirements, LHD 7 hull design and propulsion shafting constraints, schedule and funding drove the propulsion system design.