This paper introduces a framework for analyzing distributed ship systems. The increase in interconnected and interdependent systems aboard modern naval vessels has significantly increased their complexity, making them more vulnerable to cascading failures and emergent behavior that arise only once the system is complete and in operation. There is a need for a systematic approach to describe and analyze distributed systems at the conceptual stage for naval vessels. Understanding the relationships between various aspects of these distributed systems is crucial for uninterrupted naval operations and vessel survivability. The framework introduced in this paper decomposes information about an individual system into three views: the physical, logical, and operational architectural representations. These representations describe the spatial and functional relationships of the system, together with their temporal behavior characteristics. This paper defines how these primary architectural representations are used to describe a system, the interrelations between the architectural blocks, and how those blocks fit together. A list of defined terms is presented and a preliminary set of requirements for specific design tools to model these architectures is discussed. A practical application is introduced to illustrate how the framework can be used to describe the delivery of power to a high energy weapon.

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Over the past decades, ship design has seen an increased digitalization and the use of more powerful computers to assist in design tasks, such as concept design generation or analysis. Also, the application of concurrent engineering or concurrent design processes shows an attention for ship design as a field of multi-actor decision-making. Contrary to traditional `over-the-wall’ approaches, such concurrent, or collaborative, design processes are applied to involve all relevant stakeholders and design disciplines in the decision-making. The aim is to be better able to integrate disparate knowledge, experience, and preferences, as well as to build consensus among stakeholders. This is essential, since early stage naval ship design has frequently been described as a wicked problem, as it is not only the product (i.e. the ship) which is still fluid, but more importantly the required performance (i.e. the requirements) which are fluid. From a general multi-actor decision-making perspective, wicked problems can be described as a type of problems where there is a lack of consensus on both the problem and solution to the problem. In naval ship design, wicked problems involve an inherent relationship between defining requirements and generating concepts designs to fulfil these requirements. Such concept designs are essential to investigate technical and financial feasibility of these requirements. Earlier research in early stage ship design has focussed on developing tools and processes to help naval architects generate concept designs for varying requirements. Over time, such tools have become increasingly applicable for real-time collaborative design-decision making by providing rapid insights into consequences of design decisions. Other research concentrated on understanding concept designs, by analysing performance of generated concept designs or by identifying design drivers based on basic design input information. Research on design rationale, i.e. reasons behind design decisions, has shown that such rationale 1) can be made explicit, 2) can be used to analyse designs, and 3) can be used to identify design drivers. However, how such design rationale is best applied within the design task itself, in the context of real-time collaborative design, is yet to be fully understood. This paper investigates the key challenges and opportunities for incorporating design rationale capturing and reuse during collaborative design. The primary focus is on ship layout design. Then, a set of method requirements, aiming to overcome identified key challenges, will be deduced. Subsequently, a method integrating interactive ship layout design tools and real-time design rationale capture, analysis and feedback, will be introduced. Specifically, a rationale representation has been developed that requires low capturing effort and yet provides useful context for design discussions. These rationales are 1) captured in an overview next to the layout under consideration, 2) added as annotations to the design, 3) used in first-order performance calculations, and 4) evaluated for satisfaction and conflicts with other rationales. Finally, a qualitative proof-of-concept case study will be presented to illustrate how the developed method can support collaborative design during early stage ship design. The paper will close with suggestions for further development and field testing of the methodology.

Vulnerability reduction is an important topic during the design of naval ships because they are designed to operate in hostile environments and because their on-board distributed systems are becoming increasingly complex. The vulnerability needs to be addressed in the early design stages already, in order to prevent expensive or time-consuming modifications in later, more detailed design stages. However, most existing methods for assessing the vulnerability are better suited for more detailed design stages. Furthermore, existing methods often rely on pre-defined damage scenarios, while damage -or system failure in general -may also occur in ways that were not expected beforehand. This paper proposes a method that addresses these gaps. This is done by incorporating several additions to an existing vulnerability method that has been developed by the authors, using a Markov chain. With this method, there is no longer a need for modelling individual hits or failure scenarios. The additions are illustrated by two test cases. In the first one, a notional Ocean-going Patrol Vessel is considered, and damage is related to physical locations in the ship. The second test case considers a chilled water distribution system in more detail, with failures modelled independent from the physical architecture. The quantitative nature of the results provide an indication of the generic, overall vulnerability of the distributed systems, which is meant to be used in the early design stages for identifying trade-offs and prioritising capabilities.

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.