System-Of-Systems Modelling and Simulation in Warship Design for Operations

Abstract

Naval ships, or more generically naval systems, rarely operate as a single asset, most often they operate in small or large task-groups. Individual ships are thus part of a larger complex interacting system-of-systems performing a variety of tasks and missions in support of national and international naval operations. In such a system-of-systems composition naval systems are mutually supportive. For example, a replenishment ship is there to support task-group combatants, while the combatants in turn protect the replenishment ship which typically has few self-defence measures. Timely insight into system interactions and trade-offs driving the performance, effectiveness and affordability of these system-of-systems is crucial in achieving balanced designs which work and operate effectively in naval operations. A NATO Research Task Group (RTG) was initiated to investigate how systems-of-systems technical, operational and cost modelling can help in identifying and understanding such insights aiding requirements elucidation. In support of this RTG, the Netherlands Defence Materiel Organization has worked on a test-case to demonstrate the benefits and possibilities of assessing alternative naval ship designs, and their individual technical requirements, in a system-of-systems modelling approach. In this test-case, a small task-group performing two consecutive naval operations, mine clearance and a non-combatant evacuation, was modelled with the purpose of investigating the influence of ship design requirements on the overall mission effectiveness. Specifically, the interactions of varying requirements on ship signatures and mine clearance sonar performance were investigated. Also, the difference between a single large or two smaller amphibious assault ships was included. This was done to investigate the trade-off between a single large ship with concentrated but possibly vulnerable landing capacity versus two smaller ships with distributed and less vulnerable landing capacity. Each system-of-systems alternative was evaluated in terms of the overall mission effectiveness, which is defined as the number of evacuees rescued, and total acquisition cost. The results of the test-case indicate that indeed a significant trade-off in mission effectiveness and cost exists between investing in mine clearance sonar performance versus reducing the vulnerability of the task-group ships, either by distributing the landing capacity over two assault ships, or by reducing the ship signatures. The cost-benefit results clearly show these distinct trade-offs giving the supporting information for setting the task-group ships requirements. In conclusion, the applied system-of-systems modelling approach has made it possible to identify and quantify important interactions in the test-case. Traditional single ship, single operation modelling and simulation would not have captured these essential insights. Hence, designing effective and affordable (war) ships requires a broadening of scope from a single ship and single operation perspective to a system-of-systems performing multiple (consecutive) operations.