Naval Vessels Research Articles

Fundamental Understanding of Marine Applications of Molten Salt Reactors: Progress, Case Studies, and Safety

Marine sources contribute approximately 2% of global energy-related CO₂ emissions, with the shipping industry accounting for 87% of this total, making it the fifth-largest emitter globally. Environmental regulations by the International Maritime Organization (IMO), such as the MARPOL (International Convention for the Prevention of Pollution from Ships) treaty, have driven the exploration of alternative green energy solutions, including nuclear-powered ships. These ships offer advantages like long operational periods without refueling and increased cargo space, with around 200 reactors already in use on naval vessels worldwide. Among advanced reactor concepts, the molten salt reactor (MSR) is particularly suited for marine applications due to its inherent safety features, compact design, high energy density, and potential to mitigate nuclear waste and proliferation concerns. However, MSR systems face significant challenges, including tritium production, corrosion issues, and complex behavior of volatile fission products. Understanding the impact of marine-induced motion on the thermal–hydraulic behavior of MSRs is crucial, as it can lead to transient design basis accident scenarios. Furthermore, the adoption of MSR technology in the shipping industry requires overcoming regulatory hurdles and achieving global consensus on safety and environmental standards. This review assesses the current progress, challenges, and technological readiness of MSRs for marine applications, highlighting future research directions. The overall technology readiness level (TRL) of MSRs is currently at 3. Achieving TRL 6 is essential for progress, with individual components needing TRLs of 4–8 for a demonstration reactor. Community Readiness Levels (CRLs) must also be addressed, focusing on public acceptance, safety, sustainability, and alignment with decarbonization goals.

Law enforcement or use of force: The legal nature of activities conducted by CCG and JCG in the disputed waters

In recent years, China and Japan have been engaged in persistent maritime law enforcement competition in the waters surrounding Diaoyu Islands. There is a profound concern that the recent enhancement of their respective coast guards’ capabilities and mission scopes, coupled with a lack of mutual trust, may give rise to mutual misinterpretation of intentions. Such misjudgment has the potential to initiate a sequence of escalating reactions, ultimately culminating in armed conflict. The crucial factor in preventing this domino effect is the rational evaluation of the nature of maritime law enforcement operations conducted by both parties within the contested waters. Providing relatively objective evaluation criteria for these assessments is a critical role that international law can fulfill at this juncture. International judicial precedents have articulated a set of principles governing maritime law enforcement activities. Notably, the Guyana/Suriname case and the Detention of Three Ukrainian Naval Vessels case offered significant insights into the limitations on law enforcement operations in disputed maritime areas. Concurrently, both China and Japan have developed relatively comprehensive legal frameworks pertaining to the law enforcement activities of their respective coast guards. A better understanding of each other’s domestic legal regulations would also aid both China and Japan in avoiding misinterpretations of each other’s intentions. Indeed, through a comprehensive synthesis of the perspectives offered by international judicial bodies and a systematic analysis of each party’s domestic legal frameworks, this paper argues that, at least currently, neither party has exhibited intentions or actions that exceed the bounds of maritime law enforcement.

A Solution to Dynamic Weapon Assignment Problem Based on Game Theory for Naval Platforms

Weapon target assignment is a critical challenge in military contexts. Traditionally, commanding officers manually decide weapon assignments, but the problem’s complexity has grown over time. To address this, automated systems have been introduced. These systems fall into two categories, which are static (time-independent) and dynamic (considering changes over time). Static systems solve the problem for a single time step without considering temporal changes. Dynamic systems incorporate time as a variable, adapting to evolving scenarios. Two main approaches exist, which are asset-based and target-based. Asset-based approach maximizes the survival probability of assets, which is our focus in this study. We propose a solution using game theory that spans the entire area and all time frames. We employ game theory, treating continuous functions of time as utility functions for vessels. Continuous probability-to-kill values for weapons are defined across the area. Threat trajectories yield continuous kill probabilities for the weapons, translating to vessel utility. To avoid inefficiencies, we align individual vessel utility with global utility. The Nash Equilibrium provides the optimal weapon assignment strategy. Our study uses a naval environment for analysis. In summary, our research leverages game theory to dynamically assign weapons to naval vessels, aiming to maximize asset survival.

Development of integrated noise analysis systems for ship propellers considering hull wake

Recently, the requirements for underwater radiated noise (URN) reductions in ships have become significant issues, driven by concerns over the impact of naval vessel performance and noise on marine ecosystems. The majority of URN generated from ships is attributed to the propeller. This study developed the integrated noise analysis systems that predict and analyze all the significant noises generated from the propellers, considering the hull wake. Since each type of noise has different sources and mechanisms, it is essential to analyze all types of noise to evaluate the propeller noise performances comprehensively. The model was developed for cavitation noise by compression and expansion motion of bubbles to evaluate the radiated noise. For non-cavitation noise, a noise model on the frequency domain was derived to cover the noise generated by changes in the wake. The unsteady pressure on the rotating blade was obtained using flow fields and wall pressure spectrum, extending to high frequencies. The developed system provides a valuable tool for propeller optimization designs by minimizing URN while considering the shape of the hull and appendages.

Research on Aircraft Engines and Advanced Power in Land, Sea and Air

This paper provides a comprehensive overview of advanced propulsion technologies in military applications across land, sea, and air domains. It examines the theoretical foundations of propulsion systems, tracing the evolution of aircraft engines from early piston designs to modern jet propulsion. The study explores current state-of-the-art technologies, including advanced turbofan engines, hybrid electric systems, and nuclear propulsion for naval vessels. Special attention is given to emerging fields such as unmanned aerial vehicle propulsion, hypersonic technologies, and stealth engine designs. The research also delves into futuristic concepts like magnetohydrodynamic propulsion and pulse detonation engines. Throughout the analysis, common themes of improved efficiency, enhanced power-to-weight ratios, and increased operational capabilities are highlighted. This paper aims to provide a holistic view of the current landscape and future trajectory of military propulsion technologies, underlining their critical role in shaping modern warfare capabilities.

Spatiotemporal Analysis of Sonar Detection Range in Luzon Strait

Sonar serves as a critical submarine detection apparatus for naval vessels, with its detection range forming the foundation of its overall performance in underwater surveillance. The Luzon Strait, in the eastern part of the South China Sea, presents a complex hydrographic setting that profoundly influences sonar performance, necessitating mastery of the detection range variation for enhanced anti-submarine operational efficiency. This study employs the Bellhop acoustic propagation model to estimate the transmission loss. Subsequently, a detection probability integration approach is applied to determine the sonar detection range in the Luzon Strait from 2019 to 2023, which is then subjected to statistical analysis. The findings indicate the following. (1) During the summer and autumn, the shallow mixed layer fails to generate a surface duct, resulting in shorter detection ranges that are primarily dependent on the water depth. In the Shallow Water Zone (<150 m), frequent interactions between sound waves and the sea boundaries lead to considerable acoustic energy attenuation, maintaining a short detection range. In the Intermediate Depth Zone (150–2500 m), sound rays retain adequate energy post-seabed reflection, extending the sonar detection to 5–8 km. Beyond 2500 m, the diminishing reflective energy restricts the range to 2–5 km. (2) Conversely, in the winter and spring, the formation of a surface duct becomes the predominant determinant of the detection range, capable of exceeding 10 km, overshadowing the influence of the water depth.

Influence of stiffeners on acoustic emission monitoring of ship structures

Naval vessels are valuable assets that are expensive to build and maintain. Predictive maintenance is crucial to enhance efficiency and operability and to extend the service life of these structures. Fatigue is regarded as one of the main damage modes affecting the structural integrity of ship structures. Fatigue cracks can develop at the intersections of stiffeners and other structural elements, without being detected until they substantially grow, introducing a degree of uncertainty in the estimation of the fatigue damage. Acoustic emission (AE) is a passive ultrasound method for the detection and localization of different types of damage. AE is sensitive to crack propagation and can cover large areas, making it suitable for structural health monitoring of ship hulls. However, for accurate fatigue crack detection via AE it is crucial to understand how ultrasound waves interact with structural members i.e. stiffeners and longitudinal frames. Dispersion, scattering, reflection, and multimodality have so far hindered the application of AE in this context. This study aims to assess ultrasound wave behavior in ship structures in the presence of structural elements such as stiffeners and longitudinal/transversal frames. It investigates the ultrasound wave transmission dependence on source frequency and angle of incidence using spectral finite element (SEM) simulations and experimental measurements. The experimental setup includes a 10mm thick steel plate with a stiffener and a longitudinal beam (Figure 1). Pairs of sensors are placed on each side of the stiffener to record the incoming and transmitted waves, and to determine the transmission coefficient. By combining the results of both simulation and experiments, an expression for the transmission coefficient as a function of different frequencies and angles is presented. The results of this study can be used to maximize the coverage of AE monitoring systems and enhance their sensitivity for detection of fatigue cracks on ship structures.

Shape sensing with iFEM on a type IV pressure vessel based on experimental measurements

The service life of a ship depends on its structural integrity, which can be undermined through time via different loading conditions. The incorporation of a Structural Health Monitoring (SHM) system could enhance the safety of the vessel because information about its health condition could potentially lead to the avoidance of catastrophic scenarios by the detection of structural damages and their progression, especially when they may be unobservable via physical inspection. Within this context, a model-based SHM method called inverse Finite Element Method (iFEM) has been recently developed to assess the displacement and stress profile of vessels. iFEM offers several advantages, including the independence from material properties and loading conditions, the lack of training procedures, and the limited computational demand, which makes it suitable for real-time applications, enabling to reconstruct the complete displacement, and thus, the strain field starting from discrete strain measures. In this work, we explore the application of the iFEM in challenging scenarios, regarding repeated stress fluctuations (e.g. fatigue) or other type of mechanisms like corrosion, buckling or even externally imposed damages from collision impacts or combat type damages (explosions, ballistic, etc.), depending on the specific case of naval vessels. An anomaly index is used to highlight the health state of the structure by comparing the strain predicted by the iFEM at some test locations with the strain measured by a test sensor in the same position. The two values will match only for the healthy structure, while their departure from each other will indicate anomalous conditions. Though the formulation of the diagnostic problem is general for an arbitrary component geometry and damage type, the proposed study is accompanied by some numerical examples applied to a realistic ship case.

Effects of dynamic injection pressures on spray, combustion, and exhaust emission characteristics in a CRDI diesel engine with naval vessel fuel

Effects of dynamic injection pressures on spray, combustion, and exhaust emission characteristics in a CRDI diesel engine with naval vessel fuel

‘More Flags’ Meets Failure: Brazil, the United States, and the Vietnam War

As part of its ‘more flags’ campaign, the United States wanted Brazil to fight in the Vietnam War. No Latin American country mattered more to the U.S. effort. The United States considered leveraging an economic loan, naval vessels, and a prioritization of Brazil in inter-American affairs. Many Brazilian officials liked the idea of a greater military presence in Vietnam. They hoped to gain valuable counterrevolutionary experience in a tropical setting akin to their own, curry favor with the United States, and acquire new military technology. Brazil’s greatest proposal centered on a request for modern naval destroyers that would see Brazil baited into combat. But public opinion, self-imposed restrictions, and key individuals ultimately doomed the prospects for Brazil’s entry. This article helps to further internationalize our understanding of the Vietnam War and situate Latin America within the broader context of the global Cold War. It adds to our understanding of the limits that existed in U.S.-Latin American relations, the U.S. commitment to multi-lateralizing its military campaign in Vietnam, and the political capacity of Brazil’s military dictatorship at home.

A performance comparison of utility functions for game theory based weapon-target assignment

The weapon-target assignment problem has been considered as an essential issue for military applications to provide a protection for defended assets. The goal of a typical weapon-target assignment problem is to maximize the expected survivability of the valuable assets. In this study, defense of naval vessels that encounter aerial targets is considered. The vessels are assumed to have different types of weapons having various firepower and cost as well as the incoming targets may have different attack capabilities. In a typical scenario, in addition to protecting assets, it is also desirable to minimize the cost of weapons. Therefore, an asset-based static weapon-target assignment problem is considered in order to both maximize the expected survivability of the assets and minimize the weapon budget. Thus, a co-operative game theory based solution is proposed which relates the utilities of the individuals to the global utility and reach the Nash equilibrium.

Enhanced antifouling and antibacterial performances of novel UV-curable polysiloxane/microcapsules/Ag composite coatings for marine applications.

Marine biological fouling is a widespread phenomenon encountered by various oceanic ships and naval vessels, resulting in enormous economic losses. Herein, novel 4,5-dichloro-2-octyl-isothiazolone@sodium alginate/chitosan microcapsules (DCOIT@ALG/CS) were prepared through composite gel method using DCOIT as core materials, ALG and CS as shells, and CaCl2 as the cross-linking agent. The formed microcapsules (MCs) with Ag nanoparticles (AgNPs) were then filled in UV-curable polysiloxane (UV-PDMS), followed by UV irradiation to yield UV-PDMS/microcapsules/AgNPs (UV-PDMS/MCs/Ag) composite coatings. The constructed micro-nano dual-scale surface using the MCs and AgNPs improved the antifouling and antibacterial properties of UV-PDMS/MCs/Ag coatings. The as-obtained UV-PDMS/MCs/Ag coatings exhibited a static contact angle of about 160°, shear strength of 2.24 MPa, tensile strength of 3.32 MPa and elongation at break of 212%. The synergistic bacteriostatic effects of DCOIT and AgNPs in UV-PDMS/MCs/Ag coatings resulted in a bactericidal rate of 200 μg ml-1 towards Escherichia coli and Staphylococcus aureus with saturation at 100% within 10 min. In sum, the proposed composite coatings look promising for future marine transportation, pipeline networks and undersea facilities.

Operational Matrix Framework for Energy Balance Analysis for Early Stage Design of Complex Vessels

Considering vital ship systems or distributed ship service systems at the early stage of complex vessels is a challenging task. The recent UCL Network Block Approach aimed to enable ship designer to address ship systems design synthesis simultaneously as a logical network using MATLAB with a CPLEX Toolbox in MATLAB and representative piping, cabling, and trunking routings on the physical description of the ship using a proven CASD tool PARAMARINESURFCON. This was possible due to adopting a set of frameworks, as part of this comprehensive approach. The paper presents one of the frameworks: the Operational Matrix, to formulate distributed ship service systems network in the early stage design of complex vessels. The application of the framework could take on many forms and can be manipulated to suit a specific distributed ship service system’s design. In this paper, a tutorial is given, leading from the simplest application of the Operational Matrix Framework to an example of a complex Operational Matrix application for the 3D multiplex submarine systems problem. The use of the proposed Operational Matrix Framework is shown to reveal the relationship between objective functions, constraints, bounds, and solutions of that linear programming formulation. The Operational Matrix Framework can enable the solvers (CPLEX Toolbox in MATLAB) to be very efficient in advancing early stage ship design applications. The Framework could be developed further for investigating the analysis of energy balances for new systems to achieve net zero energy demands for future naval vessels.

An evaluation of system modularity and interface standards as a means for continued platform level relevance

This paper will develop a descriptive working definition of modularity regarding ship systems. An effort will be made to expose the underlying motivation and attractiveness of modularity in naval vessels utilizing economic salvage value and continued operational relevancy. A survey of 50 years of modern system development in support of modularity will be supported by a historical case study. The historical analogy will focus on the concurrent development of platforms and weapon systems during the age of sail. Specific focus will be given to platform developments and the advent of marine artillery and their associated technological development. The insight developed will then be applied to two modern naval corollaries.

Dual-Function Hybrid Coatings Based on Polytetrafluoroethylene and Cu2O for Anti-Biocorrosion and Anti-Wear Applications

Corrosion and wear issues of motion components exposed to water-based corrosion mediums, e.g., naval vessels and oil extraction equipment, pose challenges for the lifespan and reliability of the motion systems. In this work, epoxy-based coatings modified with polytetrafluoroethylene (PTFE) and cuprous oxide (Cu2O) nanoparticles were prepared. The anti-corrosion performance of the coatings was comparatively investigated by electrical impedance spectroscopy and Tafel tests in sterile and sulphate-reducing bacteria (SRB) mediums. Moreover, the tribological behaviors of the coatings were examined under water lubrication conditions. Our results demonstrate that the epoxy coatings lower significantly the corrosion current density icorr and the charge transfer resistance of the electrical double layer Rct of the carbon steel substrate. Interestingly, the hybrid coatings filled with both PTFE and Cu2O exhibit excellent anti-corrosion and anti-wear performance. After being immersed in the SRB medium for 18 days, the icorr of the pure EP coating and hybrid coatings are 1.10 × 10−7 Amp/cm2 and 0.3 × 10−7 Amp/cm2, and the Rct values are 1.04 × 103 Ω·cm2 and 3.87 × 103 Ω·cm2, respectively. A solid tribofilm forms on the stainless steel counterface sliding against the hybrid coating, which is surmised to be essential for the low friction coefficients and wear. The present work paves a route for formulating the dual-function coatings of anti-biocorrosion and anti-wear.

A major midlatitude hurricane in the Little Ice Age

Abstract. An unusually severe hurricane (Louisbourg Storm) struck Nova Scotia, Canada, in 1757. Historic records describing storm conditions as well as damage to ships and coastal fortifications indicate an intensity beyond any modern (post-1851) Atlantic cyclones striking the same region, yet this storm struck during a cold climate period known as the Little Ice Age (LIA). Its track and timing coincided with a British naval blockade of a French fleet at Fortress Louisbourg during the Seven Years' War (1756–1763). This provides a unique opportunity to explore growing scientific evidence of heightened storminess in the North Atlantic despite a colder climate expected to suppress hurricane intensification but which research is increasingly showing to have supported North Atlantic storms of exceptional strength. Weather attributes extracted from the logs of naval vessels scattered by the Louisbourg Storm provided multiple hourly observations recorded at different locations. Wave height and wind force estimates at ship locations were compared to extreme storm surge heights calculated for Louisbourg Harbour and a shipwreck site south of Fortress Louisbourg. Comparing these metrics to those of modern analogues that crossed the same bathymetry reflects landfall intensity consistent with a powerful major hurricane. Historical records show this storm originated as a tropical cyclone at the height of hurricane season and intensified into the northern midlatitudes along the Gulf Stream. Its intensity at landfall is consistent with established seasonal climatological models where highly baroclinic westerlies driven by autumn continental cooling encounter intensifying north-tracking tropical cyclones fuelled by sea surface temperatures that peak in autumn. Stronger seasonal contrasts from earlier and colder continental westerlies in the Little Ice Age (LIA) may have triggered explosive extratropical transition from a large hurricane resulting in a more severe strike. It suggests that tropical cyclones lasting days to weeks and the conditions that generate them are likely masked by cooler historic mean annual to multi-decadal LIA climate reconstructions.

Machine learning Based Bearing Fault Classification Using Higher Order Spectral Analysis

In the defense sector, where mission success often hinges on the reliability of complex mechanical systems, the health of bearings within aircraft, naval vessels, ground vehicles, missile systems, drones, and robotic platforms is paramount. Different signal processing techniques along with Higher Order Spectral Analysis (HOSA) have been used in literature for the fault diagnosis of bearings. Bispectral analysis offers a valuable means of finding higher-order statistical associations within signals, thus proving to detect the nonlinearities among Gaussian and non-Gaussian data. Their resilience to noise and capacity to unveil concealed information render them advantageous across a range of applications. Therefore, this research proposesa novel approach of utilizing the features extracted directly from the Bispectrum for classifying the bearing faults, departing from the common practice in other literature where the Bispectrum is treated as an image for fault classification. In this work vibration signalsare used to detect the bearing faults. The features from the non-redundant region and diagonal slice of the Bispectrum are used to capture the statistical and higher-order spectral characteristics of the vibration signal. A set of sixteen machine learning models, viz., Decision Trees, K-Nearest Neighbors, Naive Bayes, and Support Vector Machine, is employed to classify the bearing faults. The evaluation process involves a robust 10-fold cross-validation technique. The results reveal that the Decision Tree algorithm outperformed all others, achieving a remarkable accuracy rate of 100 %. The naive Bayes algorithm also demonstrated the least performance, with an accuracy score of 99.68 %. The results obtained from these algorithms have been compared with those achieved using Convolutional Neural Network (CNN), revealing that the training time of these algorithms is significantly shorter in comparison to CNN.

Thermo-fluid characteristics and lock-on range efficiency of infrared suppression (IRS) devices with diathermic funnels in the presence of surface radiation: A comparative study

This investigation examines the influence of surface radiation on the thermo-fluid characteristics of three distinct infrared suppression (IRS) mechanisms employing diathermic funnels. Managing the flow and heat transfer attributes within an IRS apparatus becomes increasingly intricate owing to the convergence of frigid ambient mass entering via inter-funnel apertures and the high-temperature flue gas generated by the turbine on naval or cargo vessels. Conducting a three-dimensional analysis involving conical, louvered conical, and louvered cylindrical funnels, computational simulations based on the Navier-Stokes equation, encompassing the energy and radiative transfer equations, are conducted. This study offers a comprehensive elucidation of how the Reynolds number (ranging from 6.1 × 105 to 3.18 × 106), FOL (negative, zero, and positive), and NOL collectively influence the temperature variations at the system’s exit. Louvered cylinder-shaped funnels, specifically in zero-overlap scenarios, emerge as the optimal configuration for the IRS system. The computations undertaken aim to gauge the ship’s lock-on range, accounting for the presence or absence of the IRS system.

Optimum design of HNBR and PCR-based isolation system to protect a sensitive article stored in a naval vessel container subjected to shock load

In naval engineering, protecting sensitive articles from shock loads is a major concern, as it may lead to adverse consequences. This paper focuses on the design of a novel Hydrogenated Nitrile Butadiene Rubber (HNBR) and Polychloroprene Rubber (PCR)-based shock isolation system to protect a sensitive article stored in a hollow cylindrical naval vessel container (NVC). Firstly, NVC is modeled as a two-degree-of-freedom lumped parameter model (LPM), wherein isolators made of HNBR and PCR materials are modeled with 5-order polynomial nonlinear stiffness and linear damping. The optimal values of the isolator parameters are obtained using a multi-objective genetic algorithm, and corresponding responses to a shock load are found using MATLAB. Furthermore, a three-dimensional (3D) finite element model (FEM) of the NVC is generated in ABAQUS and subjected to shock loading in a transverse direction to conduct a comprehensive dynamic analysis of the isolation system. In 3D simulation, HNBR and PCR materials are modeled using a hyper-viscoelastic model developed based on experimental test data. The 3D simulation results of the NVC for the optimized design of HNBR and PCR isolators agree with the optimized results of the LPM. Moreover, the proposed HNBR and PCR isolators are very effective in shock reduction.

Mesothelioma among seamen: a systematic review and meta-analysis.

Navy personnel and seafarers live and work 24 h per day in the shipboard environment and they are exposed to asbestos fibers released into the confined spaces aboard ships. We conducted a systematic review and meta-analysis to quantify the mesothelioma risk of seamen working aboard ships, either commercial or naval vessels, as compared to that of the general population. We carried out a literature search in MEDLINE through PubMed and EMBASE, from inception to 31 December 2021, of all studies on seamen working aboard ships, either commercial or naval vessels, characterized by exposure to asbestos and providing mesothelioma risk estimates. The Newcastle-Ottawa Scale was used to assess the quality of the studies included. The pooled standardized mortality ratio (SMR) was computed across eligible studies. The study protocol was registered on PROSPERO and reporting followed the preferred reporting items for systematic reviews and meta-analyses guidelines. A total of 10 studies published from 1990 to 2020 were considered eligible and included in the systematic review and meta-analysis. All the included studies were of good quality, with a median score of seven out of nine. Overall, there were 235 mesothelioma cases/deaths in the included studies versus 115.6 expected, with a pooled SMR of 2.11 (95% confidence intervals, 1.70-2.62), in the absence of a significant between-study heterogeneity ( I2 = 39%, P = 0.11). A more than double excess risk for mesothelioma among seamen working aboard ships emerged from our meta-analysis.