By Bob Ames
ELECTRICAL SYSTEMS ARE MORE IMPORTANT THAN EVER ABOARD SHIPS. PLATFORM DESIGN AND ENERGY MANAGEMENT MUST GO HAND IN HAND.
Electric cars, renewable energy, autonomous vehicles, and consumer electronics are evidence that a new power and energy future is emerging in both the civilian and military worlds.
Recent developments in weapon systems have delivered the next-generation in defense capability and these systems are challenging existing ship design practices, theory, and engineering tools. Like hybrid or all-electric cars, Navy ships are moving to a new paradigm where electric power and energy supply is directly related to ship performance. Like smartphones, everyone wants high-power density, energy-efficient systems, speed, control, survivability, and upgradeability—all at an affordable price in a functional package.
The promise of these new weapon systems is so compelling that it will set the stage for warships for the next 50 years and push naval design toward a future centered around high levels of power and energy that can be directed wherever it is needed, whenever it is needed.
The great divide between the old and the new is the way modern systems use energy. Systems such as rail guns, electronic warfare, and lasers bring new high electric loads that have high pulse energy demands. This will require new power system architectures that include energy storage, thermal management, and specialized power converters. To make ships with these systems affordable, it also will require higher power density. Acquiring that density likely will force a change in the ships’ primary electric bus current from alternating current to direct current. The management of energy in this new system architecture will require critical controls that must operate without fault in a few milliseconds of time and interface the ship machinery systems with the combat control system. These controls must manage mission system loads, ship propulsion, auxiliary systems, and all power and energy needs for an entire ship for all conditions. It will manage the energy supply from energy storage magazines and manage the ship generators that supply it.
Ship controls also will be critical to recoverability in the event a ship is damaged and a portion of its systems are down. A ship’s vulnerability can be reduced by redundancy and redirection much like the internet. In the case of Navy ships, these systems are designed to operate across multiple zones. A zone is typically a physical subdivision of the ship. The naval architect assigns mission functions to specific zones of the ship in a manner that enhances survivability. The boundaries of the zone can be arbitrary, but to improve survivability the distributed systems zones and damage control zones are usually aligned.
Designing ships for these combinations of mission systems requires an understanding of how the ship will be operated and emerging tactics and doctrine; and requirements for power, energy, thermal management and computing.
In this new ship design paradigm, ship operations will drive power needs. The power and energy systems must deliver on this need with power dense electronics. These systems also must be arranged in the ship by zone, with all systems managed by time critical controls. The ship platform design and ship systems design are more interdependent and critical than ever.
How we leverage advanced weapons and sensors in a new ship design is best understood earlier in the engineering/ integration process where major trade studies are performed. Early-stage design is about getting the best balance between capability and affordability.
Software is at the heart of any research or design activity. In the Navy engineering community, modeling and simulation software spans many domains of knowledge at varying degrees of detail; using many software products from both the government and commercial sectors. In the case of new technology insertion, modeling and simulation tools tend to lag as knowledge must be acquired before it can be coded for analysis and decision support. The challenge is twofold. First, tools must be created or upgraded to capture the physics of the problem. Second, decisions are made from data, and this ship design data must be integrated and universally understood among stakeholders. To address many of these issues, the Office of Naval Research (ONR) formed the Electric Ship Research and Development Consortium to combine academic research institutions to address the physics of the problem, and then initiated a software development program to design and analyze system architectures. This application is called Smart Ship System Design (S3D). ONR is now integrating S3D into a common software framework used by the Navy’s early stage design tools providing data compatibility between design and analysis tools.
Recognizing the importance modeling and simulation for design tools and system simulation and testing, the 2014 Defense Department Research and Engineering Enterprise identified these relevant science and technology priorities and communities of interest:
Data to Decisions: The primary focus areas of this community of interest are human-computer interfaces, analytics and decision tools, information management, advanced computing and software development, and networks and communications. Data to Decisions incorporates the science and applications to reduce cycle time and manpower requirements for analysis and use of large data sets.
Engineered Resilient Systems: Engineering concept, science, and design tools to protect against malicious compromise of weapons systems and to develop agile manufacturing for trusted and assured defense systems.
Weapons: Develops technology-based options for weapons, and seeks excellence in weapon technologies and related research, including guidance, navigation, and control; ordnance; propulsion; undersea weapons; high-energy lasers; radio-frequency weapons; nonlethal weapons; and modeling, simulation, and test infrastructure.
The DoD Research and Engineering Enterprise also stated: “[Modeling and simulation] is a key enabler of capabilities supporting real world applications that underpin innovative technology solutions, act as force multipliers, save resources, and save lives by: promoting cooperation and collaboration to remove barriers to interoperability and reuse; and providing a common technical framework (architectures, data standards, and common [modeling and simulation] services) that improves interoperability, reuse, and cost-effectiveness.”
Data integration challenges go hand-in-hand with interorganizational communication challenges. Navy senior leaders recognized that power and energy systems research was showing great promise and individual technology was being demonstrated, but an integrated approach was needed that required coordination among several stakeholders to pursue common and more affordable solutions. The Navy feared that without coordination, stove-piped approaches would produce redundant point solutions on the same platform, thereby increasing acquisition costs and resulting in complex system integration challenges.
In 2014 the Naval Sea Systems Command’s executive steering group directed the formation of an overarching integrated project team called Combat Power and Energy Systems. Within this team are several working integrated product teams aimed at solving specific energy-related problems for high energy pulse load mission systems. One of the six teams was the Design Tools and Methodology (DTM) team headed by ONR.
The DTM team produced a comprehensive roadmap that identified modeling and simulation requirements and development activities needed by the entire combat power and energy systems community. The community concluded that the development and integration of new power and energy technology must be assessed within the constraints of total ship design using modeling and simulation software. The requirements of operations, power and energy systems, and total ship design are interdependent.
The proposed strategy for discovering the needed methods and interface standards for these new systems is through prototyping. This would involve building a portion of the system that tests the behavior of critical components and their interactions. In addition, modeling and simulation software would be developed that mimic prototype performance. This software product is commonly referred to as a “digital twin” in the industry. General Electric, for instance, uses a digital twin for many studies from wind energy power plants to wind turbines and jet engines.
The Navy prototype is formally called an advanced development model (ADM). The ADM will require real- time electric and control system simulation capabilities, including power mission systems and hardware-in-the-loop options for critical capabilities for multiple ship variants. Power and energy system design requires transient, fault, harmonic, stability, and quality of service analyses, as well as the incorporation of control system behavior. In addition, design studies will require dynamic simulation of thermal management systems to explore and determine appropriate system designs that support advanced weapons and sensors.
With appropriate forethought and resourcing, the individual software development verification and validation activities can be coordinated to result in a digital twin of the ADM. An additional requisite for a digital twin is that sufficient foundational research has been executed and data generated such that technologists understand the physical phenomena to be evaluated and may thereby model it.
This architecture has complex controls and interface details that must be resolved. Controls are critical to the success of this technology, but vulnerability and recovery also will be design requirements from the earliest stages. ONR has an upcoming Future Naval Capability intended to address controls and design integration. This will set the stage for system characterization for the early stage design tools and can be used in later stages of design, construction, operation, and service life support.
During the early stages of design, new designs are modeled by a tool called the Rapid Ship Design Environment (RSDE) where tens of thousands of designs are generated in what is called a design of experiments. These tools are expanding the decision support process, and with recent deployment on Defense Department high-performance computers the opportunity for discovery is unprecedented. Unfortunately, this design of experiments presumes that the characterization of any single design in the trade space of solutions is feasible and that the theory employed by the tools is validated.
With combat power and energy systems-equipped ships, the RSDE model is dependent on the details of the ship system power architecture and interface standards. What will be required is an iterative process of design and analysis from systems architecture to concept design to dynamic analysis returning design modifications to the system architectures, where the process repeats itself until the solution is feasible. Doing this for many ship designs and many system architectures can only be accomplished through data integration across the community. The ship design methodology must be efficient. It must be about design and analysis, not nonproductive, labor-intensive activities such as data migration, translation, and data entry.
The Navy will need to engage industry to build these complex components and systems and provide their respective digital twin models for simulation. With this new design paradigm comes many challenges. With new tools and supporting research, new warship designs for at least the next 50 years will increasingly reflect the advantages of these new power and energy systems.
About the author:
Bob Ames is a detailee from the Naval Surface Warfare Center Carderock Division with the Office of Naval Research’s ship systems and engineering division.