In May of 2020 a container ship sailing along the eastern coast of Australia encountered a storm and lost a number of containers. The loss of containers was not unusual, about 1400 containers are lost each year on average. What was unusual was the large number of containers on this one ship. Coincidentally, MARIN releasted a report in September 2020 investigating similar losses of large number of containers from container ships going to northern Europe. Then, between October 2020 and February 2021, seven ships on a northern Pacific route from China to the USA loss between 3,000 and 4,000 containers and had a large number of container stacks roll over. This paper is a independent generic assessment of a marine forensic investigation taking a systems engineering approach to look at the broad spectrum of possible causes of container stacks rolling over and lossing containers. The paper discusses weather effects on the stability and motions of the container ships and the securing of the cargo containers. The paper goes into detail about the underlying issue of the container stacks and their heights such that at decreasingly smaller angles of heel or rll, the line of action of the weight of the higher containers passes outside the base of the stack thereby causing a overturning moment on the corners of the containers.

After almost a century the US Navy has reintroduced tumblehome into the design of naval combatants. This paper discusses some of the reasons tumblehome was originally designed into ships and why it served it owners well for many centuries. The transition from sail to steam power a little over a century ago led to a variety of problems with the combatant ships designed with tumblehome where the lack of damage stability caused a major loss of life as these ships sank so quickly. During World War I ships designed with tumblehome fell out of favor and some of the ships were actually modified to remove the tumblehome from the design. These changes in the design of tumblehome ships are discussed in this paper.

While transiting off the Southeastern Connecticut coast in 2019, F/V Emma & Maria experienced a knock down incident. This paper investigates the causal factors of this event, specifically focusing on stability challenges common to the New England commercial fishing fleet. After identifying contributing factors to the incident, an incline test was conducted to determine the center of gravity of the recently modified vessel. A stability, seakeeping and operability analysis, across a range of operational and worst-case conditions, is presented to determine the limitations of the vessel. To improve vessel operability, the addition of concrete ballast in the aft bilge is proposed, resulting in an improvement in both vessel stability and seaworthiness. Possible improvements to current fishing vessel regulations are also suggested to improve the safety of the fleet.

A simplified assessment of vessel stability is considered utilizing on-board measurement. Application to unregulated or less regulated pleasure craft and smaller passenger vessels in developing countries is of specific concern as a result of continuing accidents. Past proposals are considered and stability theory is evaluated to identify those aspects which allow for greater simplicity for arriving at an approximate measure of stability. A description of the procedure for applying a simplified test is provided. Examples are given. Application should serve to increase safety for these vessel categories.

The purpose of this paper is to discuss and document the evolution of the SOLAS subdivision and damage stability regulations, with a primary focus on recent developments to improve the survivability level of passenger ships after the SOLAS 2009 probabilistic subdivision and damage stability regulations were adopted on 20 May 2005 and subsequently entered into force on 1 January 2009. SOLAS international regulations represent a consensus standard and during their development there are frequently details that are not well documented. This paper is intended to provide that documentation and explain the recent progression of this sometimes convoluted development work.

This work assesses the impact of a reduction in sail height on a generic diesel submarine's resistance, maneuverability, and recoverability. A submarine's sail has been called hydro dynamically undesirable as it increases resistance and complicates maneuverability. Sail size is dictated by the equipement it is fairing, and its height is typically determined by the optical periscope. However, the recent availability of optronic periscopes has reduced the requirement for a tall sail, which has sparked interest in the impact of reducing sail height on hydrodynamic perfomrnace. Using generic diesel-electric submarine shapes, semi-empirical estimation methods, and a fast, validated six degree-of-freedom submarine maneuvering simulator, we examinet he impact of reducing sail height on maneuverability and recoverability following sternplane jams. We show that, while turning effectiveness and horizontal plane dynamic stability are reduced, drag is also reduced, and static stability and recoverability are enhanced. This is considered a net benefit for submarine performance.

This paper summarizes knowledge gained from a five-year study of trimaran ship design, including ship concept development, scaled model experiments and numerical simulations of hydrodynamic and structural performance. Two design concepts for trimaran warships were generated through parallel tradeoff studies and design efforts in the US and Japan. A series of trimaran hull form models were constructed which included several hull shapes and side hull positions relative to the center hull. Performance evaluations included calm-water resistance and propulsion, seakeeping in regular and irregular seas at multiple headings, wave-induced bending moments and secondary loads, and free-running maneuvering. Fatigue experiments on aluminum trimaran structural details were also conducted.

Views on unmanned or autonomous ships have evolved tremendously. A few years ago, what we considered utopian is becoming not just a vision but also reality in the form of different development projects. A large publicly funded initiative on autonomous waterborne applications (AAWA) was recently conducted in Finland. This paper will focus on the outcomes of this initiative from the perspective of stability and autonomous ships. The paper will also give a review on the rules and regulation situation regarding autonomous ships and stability.

Ships interact with the environment in several ways. The focus in this paper is on how ships interact with the wind and how this is treated in design. It is generally sufficient in most cases to model wind force as a static load. However, there may be circumstances where a more detailed description of the wind is appropriate. Some examples discussed include stability under transverse winds, aircraft flight deck operations and wind resistance. The paper summarizes key properties of the wind and recent research related to some key windship interactions. This includes discussion of the challenges and possible remedies.

Inadequate stability is the proximate cause of a significant share of passenger vessel casualties worldwide. A disproportionate majority of these incidents involve domestic ferries in developing nations, where there is little enforcement of internationally accepted standards. This paper describes an ongoing effort to develop an on-board device that monitors vessel stability in real time and provides alerts and guidance to the operator. The theoretical feasibility of the project is demonstrated through a review of previous work. Several methods of obtaining stability parameters from vessel's motions are presented. The conceptual design of the device and network make use of lowcost hardware and open-source software, intended to make the device accessible and scalable for operators. Interfaces for vessel operators, passengers, and regulatory agencies are envisioned, maximizing the utility of the data.

This document describes and proposes different configurations of inflatable air chambers placed in different compartments of (marine floating structures like) ships to reduce permeability to sea water of these compartments, in the event of collision damage, thus improving the Attained Subdivision Index of the ship calculated as per SOLAS regulations. The document further describes some supporting systems to practically achieve this objective of installing and using such airbag systems on ships to prevent sinking of ships due to collision damage of the hull.

Recent archeological investigations of the civil war submarine H.L. Hunley have changed our understanding of how the vessel conducted its final attack on the U.S.S. Housatonic. Previously, the submarine was thought to have used a standoff charge against its target, but it is now clear that the charge was bolted to the end of a short spar projecting from the submarine. This means that the submarine would have been in close proximity to the weapon when it exploded. A multi-part investigation is being conducted with the goal of determining if this reduced standoff distance could explain the mysterious loss of the vessel in the minutes or hours after the attack. Here, the results of a bottomup naval architectural analysis and numerical simulations of the final attack weapon effects are reported. Together, the results provide new insight to the vessel's stability characteristics, propulsion, and dynamic loading environment during the attack. Additionally, a discussion of possible loss scenarios, informed by both calculation results and inspections of vessel's hull, is presented. While the story of what happened to H.L. Hunley that night remains shrouded in mystery after this work, several important new research questions emerge.

This paper, which is in part an update to Beck and Reed (2001), discusses current developments in seakeeping computations for ships maneuvering in a seaway. First a brief historical background is given in order to put present computations in context. Then a detailed discussion of the necessary components for simulating maneuvering in waves in an extreme seaway is presented. As part of determining the required elements of a successful, computationally-fast model for maneuvering in extreme seas, the results of a "force study" (computational experiments designed to identify the important components of a computationally-fast model), are presented. Also discussed are the tradeoffs between high fidelity, but computationally slow, models solving the unsteady Navier-Stokes equations (often called computational fluid dynamics or CFD); and blended methods that are computationally fast but use approximations that blend linear and nonlinear potential flow calculations with empirical corrections for viscous forces.

Medium Voltage DC (MVDC) Power systems are being considered for future U.S. Navy ships to support high power sensors, electronic warfare systems, and weapon systems. This paper presents a reference MVDC Power System and provides design considerations for incorporating the reference power system into a warship design.

Current guidance for calculating US-flag towing vessel stability date from over 35 years ago. In the intervening time, towing vessel design has evolved to the point that the current guidance may not be conservative. This paper examines those changes and gives examples of how the designs have evolved. Finally, recommendations are given to naval architects calculating towing vessel stability.

A series of tests using a course-keeping model ship with an autopilot system were carried out in a towing tank for research on Safe-Return-to-Port (SRTP). The autopilot system controls the rudder angle and propeller revolution rate by a feedback system. The variation of the heading angle of the test model with different control parameters was investigated first, to ensure that the test model had sufficient course-keeping maneuverability in severe wave conditions. The wave conditions and propeller revolution rate were selected based on SRTP regulations. Tests were conducted in wave conditions corresponding to sea states 4 to 6. The six-degrees-of-freedom motion response of the test model was measured by a wireless inertial measurement unit and gyro sensors to achieve fully wireless model tests. The advance speed and motion response in various wave conditions were measured and analyzed to investigate the effects of flooding behavior in a damaged condition and of waves on the propulsion and maneuvering performance of the damaged ship model.

The use of autonomous vehicles is growing in all industries. However, there are no open-source autonomous surface vehicles available in the marine industry. This paper details the design decisions made, construction methods used, and testing performed on a low-cost, open-source vessel. The vessel was designed to cross the Atlantic Ocean as a means of proving its ability to survive the harsh marine environment. A trimaran hull form and free rotating wing sail were used because the combination provided good righting characteristics, durability and low power consumption. The vessel has been shown to navigate autonomously. Total costs were less than $4000 dollars, excluding labor. Vessels of this type could be used for long duration missions recording data in the open ocean at extremely low cost.

The new probabilistic and more risk based subdivision and damage stability rules have brought many changes and more flexibility to the subdivision requirements for passenger ship designs. Whilst designers are still adapting to the fundamentally changed SOLAS requirements, applicable January 1st 2009, many additional items remain on the agenda of IMO addressing the stability of passenger ships. Additional damage stability regulations for ro-ro passenger ships as well as requirements towards stability and sea-keeping characteristics of damaged passenger ships in a seaway when returning to port by own power or under tow are among the topics that are currently being addressed. These could have considerable impact on future passenger- and ro-ro passenger vessel designs.

This paper summarizes the results from the SNAME funded T&R grant titled Preliminary Development of the Next Generation of Stability Criteria for Small Fishing Boats. The principal goal of this project was to take a broad look at effects of head and following waves on the current still water based stability evaluation methods to focus the needs for future research in the development of new performance based stability criteria. The wave effects were calculated using an off the shelf naval architect software package of the type typically used in small fishing vessel stability evaluations to explore the ability of these software packages to perform cost effective meaningful stability research. The use of the off the shelf naval architect software package also allowed the authors to explore new performance based stability criteria formats that utilized software and basic concepts already available to the naval architect.