Design Tools & Modeling
Thursday 11th November 2010, 1300hrs–1430hrs
Chaired by Rafael Bellido Variation in Military Vessel Shapes required by Stealth Operations Ing. Cristina Gironi, University of Genoa, Italy Stealth technology, as a discipline of military tactics, represents a new key aspect for the base line of a military design. Radar signature reduction is essential to increasing the battle-field effectiveness of any contemporary platform or long-range armament. This paper is oriented toward the naval area and represents a report of the studies developed on the influence of this operative requirement on the shape of a ship, specially on its superstructures. Through analysis of the radar signature of various important military vessels, it will outline the history of this technology and state-of-the-art developments, in order to find their origin on the principles of camouflage and assume the know-how to extrapolate the most important guidelines. Thanks to a basic design of a stealth ship, developed in order to capture the greater effect of the stealth in terms of sea keeping and stability, has been prepared a study for the optimization of the superstructure shapes, reducing effectively the Radar Cross Section, parameter of evaluation for the stealth technology advantages. The results of this study demonstrate that the stealth requirement can imply benefits in the management of the volumes representing this zone of the ship, giving it a more simple configuration than the traditional ones; this peculiarity permit to create an algorithm for its design and distribution, in order to develop an easier and faster decision making process within the functional design of the complete ship. Design Synthesis and Evaluation Tool for Small Ships and Combatant Craft Mr. David Woodward, Naval Surface Warfare Center (Carderock Division), United States Proliferation of low-cost, low-technology means of access denial threatens the effectiveness and raises costs of military force projection. Current and future naval platforms rely heavily on manned and unmanned surface vehicles to more effectively perform missions. High power-density efficient engines combined with high performance electrical generators and motors offer great flexibility in energy conversion and therefore provide a vehicle designer with attractive drive train options for a variety of applications within the Navy, Coast Guard, and other agencies. Some applications are unmanned surface vehicles, Naval Expeditionary Combat Command’s combatant craft, and Coast Guard craft and small ships. The Advanced Surface Ship and Submarine Evaluation Tool (ASSET) is the US Navy’s concept design synthesis tool for surface combatants and submarines. ASSET’s ship design capabilities do not extend to ships or craft less than several thousand tonnes displacement. To assess the performance and cost impact of new payload, power and propulsion technologies, a design synthesis modeling capability for high performance small craft and small ships is required. This paper will present an overview of the SEAQUEST – Small Craft project involving system design synthesis module development, design evaluation module development, and systems design integration of the Small Craft/Ship Evaluation Tool (SCET) Modules and the Integrated Propulsion Assessment (IPAS) Module. The SCET model architecture is being developed from an analysis, optimization and extension of the ASSET architecture using Design Structure Matrix (DSM) methods to minimize process iteration and feedback and improve computational speed for use in multi-objective optimization with maximum use of COTS tools. Multi-Objective Optimization in Naval Ship Concept Design Professor Alan Brown, Virginia Tech, United States Naval ship concept design is largely an “adhoc” process. Selection of design concepts for assessment is guided primarily by experience, design lanes, rules-of-thumb, preference and imagination. Objective attributes are not adequately defined or presented to support efficient and effective decisions. The design space is very large, non-linear, discontinuous, and bounded by a variety of constraints and thresholds. These problems make a structured search of design space difficult. Without a structured search, there is no rational way to measure the optimality of selected concepts relative to the millions of other possible concepts. Responsible decisions cannot be made without this information and perspective. This paper will address these problems in the context of a total systems approach to naval ship concept exploration. Multi-attribute value theory (MAVT) and the Analytical Hierarchy Process (AHP) are used to define a mission effectiveness function. An Overall Measure of Effectiveness (OMOE) model or function is an essential prerequisite for optimization and design trade-off. This effectiveness can be limited to individual ship missions or extend to missions within a task group or larger context. Practical and quantitative methods for measuring risk are also required. An Overall Measure of Risk (OMOR) is presented which includes schedule, production, technology performance and cost factors. A Multi-Objective Genetic Optimization (MOGO) is used to search design parameter space and identify non-dominated design concepts in terms of cost, effectiveness and risk. Design concepts are presented graphically as points on a non-dominated cost-effectiveness-risk frontier for consideration by decision-makers. A surface combatant design case study demonstrates this process.
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