Technical report | A Ship Performance Modelling and Simulation Framework to Support Design Decisions throughout the Capability Life Cycle: Part 1 – Risk Mitigation and Requirement Setting
Modelling and Simulation (M&S) presents the opportunity to support Australian Department of Defence endeavours toward becoming a smarter buyer in naval vessel acquisitions. Evaluating ship performance using M&S allows capability design activities to be conducted early during the Risk Mitigation and Requirement Setting phase of the Australian Capability Life Cycle (CLC). These activities support an improved understanding of a design space based on robust analysis that can be used by acquisition stakeholders to develop requirements and aid defensible design trade-off decisions. This report proposes an M&S framework for evaluating ship performance in support of Royal Australian Navy acquisitions. The M&S framework facilitates generation of an indicative design space for a defined capability need. Exploring this design space, acquisition stakeholders gain knowledge of a more thorough definition of requirements. Implementing the M&S framework ensures that the requirements released to industry, the primary output of this phase of the CLC, constrains the technical solutions to only those Off-the-Shelf designs that adequately meet the capability need. Thereby, the M&S framework can contribute to Defences ambition of becoming a smart buyer in an Off-the-Shelf naval vessel acquisition.
The Australian Department of Defence (ADOD) has adopted a smart buyer approach for Defence acquisitions to maximise capability and value for money for the Australian taxpayer. In the context of Royal Australian Navy (RAN) ship acquisitions, two guiding principles were adopted in light of the smart buyer approach: selecting a mature design and limiting the amount of Australian design changes. Stemming from these two principles, Defence has adopted an Off-the-Shelf (OTS) acquisition strategy for their surface ship capability needs. Reinforcing the smart buyer approach, the ADOD has the opportunity to utilise advances in Modelling and Simulation techniques to support definition of fit-for-purpose requirements in a robust and repeatable manner. Consequently, the requirements released to industry ensure only the most suitable OTS ship designs with respect to the capability needs will be received for down-select.
Modelling and Simulation (M&S) presents the opportunity to support the ADOD endeavours to become a smart buyer by facilitating capability design activities. Capability design activities conducted early during the Risk Mitigation and Requirement Setting phase of the Australian Capability Life Cycle (CLC) support an improved understanding of the design space. Knowledge gained can be used by acquisition stakeholders to assist development of requirements and aid design trade-off decisions.
In this report a ship performance M&S framework for RAN vessel acquisitions is proposed. The M&S framework facilitates generation and exploration of a design space based on defined naval vessel capability needs. The M&S framework can be aligned with a Model-Based Systems Engineering (MBSE) methodology to facilitate traceability between requirements, design variables and ship performance. A case study is presented for application of the M&S framework during the Risk Mitigation and Requirement Setting phase. The case study involved the acquisition of an indicative hydrographic survey capability into the RAN. The aim of the study was to analyse the impact of vessel type and hullform design for the suitability to meet an optimal hydrographic survey capability. Key Performance Parameters (KPPs) were derived from an exemplar mission scenario. Three KPPs were established relating to the launch and recovery seakeeping performance, transit based seakeeping performance, and resistance at transit speed. Design spaces of three different vessel types were considered for meeting the capability needs: a hydrographic survey vessel (HSV), an offshore patrol vessel and a frigate.
Results showed that the HSV hullform achieved optimal performance based on the three KPPs. Further analysis of the hullform was conducted to gain an understanding of the hull design variables that contributed to optimal performance. Results showed that the vessels length and length/beam ratio had the greatest influence on all three KPPs in various sea states. Consequently, increasing vessel length and decreasing the vessels length/beam ratio contributed to improved performance of all KPPs. It was shown how an understanding of the relationship between design variables and KPPs, and the strength of these relationships could assist acquisition stakeholders during the requirements definition process and support design trade-off decisions.
Knowledge gained from exploration of the HSV’s design space was used to scrutinise the existing Off-the-Shelf (OTS) naval vessel marketplace and assist in identification of possible capability risks. OTS designs were ranked based on their likely mission performance according to relationships established from exploration of the design space, discussed above. This capability design activity was able to highlight the improvement in performance of an optimised hullform as opposed to those in the current marketplace. Comparing results of the top ranked OTS naval vessels to those optimised hullforms from the generated design space, capability risks as a result of any performance gaps were able to be identified. Understanding the significance of these capability risks could drive requirements for design changes to ensure a design is fit-for-purpose. If design changes are affordable, it is logical to pursue modifications that could increase performance of the KPPs for the naval vessel being acquired. If the capability risk is too high, that is a performance gap has been identified, the requirements released to industry could drive necessary design changes to minimise the gap in performance. Otherwise, requirements should reflect the combination of parameters that contribute to improved mission performance.
Implementing the Ship Performance M&S framework during the Risk Mitigation and Requirement Setting phase of the CLC provides acquisition stakeholders with an improved understanding of a design space for a proposed capability need. Through application of the case study, it was demonstrated how the ship performance M&S framework could be used in a robust and repeatable manner. Knowledge gained from implementing the M&S framework assists acquisition stakeholders with requirements setting activities and aids defensible design trade-off decisions. Conducting these capability design activities ensures the requirements released to industry represent only the most suitable OTS ship designs with respect to the capability needs. Therefore, applying the ship performance M&S framework during this phase of the CLC can contribute to Defence’s ambition of becoming a smart buyer in an OTS naval vessel acquisition.