1. Introduction
Required levels of safety with respect to damage ship stability are typically guaranteed by the consideration and evaluation of the effectiveness of proper passive measures at the design stage against applicable regulatory provisions. These measures are in the form of potential design alternatives (hull shape, subdivision, systems redundancy and availability, etc.) and for acceptable loading conditions.
Concerted research and development efforts in the period of the last 30 or so years have mobilised the international maritime community to research on the theoretical understanding of the flooding process and to focus and act on the development of new probabilistic rules for damage stability for all ship types, new ship designs extending and challenging known design limitations, and the Safe Return to Port (SRtP) regulations. Recent related research and development efforts include the activities of the EC-funded research projects SAFEDOR (Breinholt et al., 2009), with developments and refinement of probabilistic methods for the assessment of damage stability and survivability of passenger ships, and GOALDS (Papanikolaou et al., 2013), with significant results in formulating a rational, goal-based regulatory framework properly accounting for damage stability properties of RoPax ships and large cruise ships. Risk-based approaches and cost-effectiveness considerations have been extensively used in this process. A major finding is that the overall level of safety of a ship can only be guaranteed when considering passive design measures in conjunction with active operational measures, in a holistic, balanced and cost-effective manner.
The concepts of time to flood and time to evacuate and how they interrelate are fundamental notions in determining safety thresholds with respect to ship stability and flooding. Fundamental research on this specific topic has been reported by (Jasionowski et al., 2011) in addressing the compound problem of the absolute time available for passenger evacuation on a damaged RoPax vessel undergoing large scale flooding of vehicle deck spaces. The time for the abandonment of flooded passenger ships due to collision damages, for RoPax and for cruise ships, has been examined by Spanos and Papanikolaou (2014). Vassalos (2014) details an overall probabilistic framework for flooding risk analysis, time to capsize, time to abandon ship and the evaluation of casualty thresholds/return to port/safety level and their link to systems availability post-casualty. In principle, vulnerability to flooding relates to the cumulative probability for time to capsize in the operational environment of the vessel. This also provides the key input for vulnerability monitoring, which in turn offers all the essential information for damage control and emergency response.
There are therefore many further opportunities for research and development associated with the idea of giving a more systematic and quantifiable importance to operational measures. At the same time, however, there are also numerous challenges. Some ideas regarding opportunities and challenges have been collected in the following, where the material is split in three sections, namely: operational guidance and procedures; systems availability post-damage; active measures for damage containment. It is noted that operational guidance and system availability post-damage relate to maintaining the design safety envelop through the monitoring and decision-support, facilitating operational intervention. In this paper, we provide elaborations on open challenges and food for thought for elaborating on the topic of operational measures, with specific attention to the damaged ship condition.