he purpose of the paper is to identify the most likely trends in interannual changes of the ice cover thickness on sections of the Northern Sea Route in the Laptev Sea in the winter-spring months under conditions of further climate warming. A hypothesis that in the modern period such changes can be significantly impacted by melting of submarine permafrost layers located inside the sea shelf, — a process caused by their heat exchange with bottom sea waters, is put forward. To verify the hypothesis, trends in interannual changes in ice thickness are compared with trends in variations in sea level and surface salinity. As factual material, data from the global reanalysis GLORYS12v1 is used. The research methodology is based on the standard methods of mathematical statistics. A correlation between the trends of the above processes has been found. It allows us to confirm the hypothesis put forward. The results obtained indicate that, under the conditions of ongoing climate warming, there remains a high probability that the average thickness of the ice cover will not decrease, and the ice situation in the Laptev Sea in the winter-spring months will not improve significantly. The latter confirms the need and feasibility of further development of the Russian icebreaker fleet

The problem of navigation safety is considered, in particular, the problem of developing an algorithm for an adaptive dynamic safety domain for various navigation conditions is investigated. The risk assessment of a ship approach situation is based on the safety domain as the minimum area around the ship into which an oncoming ship should not enter. Navigation conditions are considered in accordance with the rules of COLREG‑72 for navigation of vessels with limited visibility and being in sight of each other. To solve this problem, the navigation areas are classified. For further analysis, a table for the conditions and areas of navigation to identify the shape of the domains is created. The hydro meteorological situation, which takes into account the navigation conditions, and as a consequence, the need to increase the size of the safety domain, is considered. Changes in the parameters and shape of ship safety domains for different navigation conditions have been identified. For each district and navigation conditions, an original configuration of the security domain is proposed. The dynamic changes of the domain during movement in traffic separation systems and channels are separately considered. Using an example, a situation when the bow of the domain crosses the dividing line, which can lead to the appearance of false dangerous targets, is simulated. To avoid such situations, a dynamic domain with a changing shape in the form of an ellipse for swimming in a traffic separation system and channels, taking into account sailing conditions with limited visibility and in sight of each other is proposed. For the calculation, an algorithm to determine the shape of the domain under different visibility conditions and navigation areas has been compiled. Calculations for the case when the vessel enters a turn in traffic separation systems and narrow spaces have been performed. The deformation of the domain during rotation is shown.

The issues of applying basic navigation parameters (bearing and distance), and their isolines traditionally used in navigation practice in coastal waters are studied in the paper. A new distinctive feature is the use of isolines combinations (three distance arcs, two isoazimuths, a hyperbola and an ellipse) based on measured bearings and distances to the pair of landmarks to obtain the vessel fixed positions with high precision. The traditional navigation methods (the theory of isolines, the generalized method of lines position, the method of least squares) are involved as a mathematical framework. The mathematical argumentation and the isolines characteristics of bearings and distances, their combinations (difference and sum of distances, difference of bearings) are given. The solutions of the surplus equations of the lines position under random error influence by the least squares method and the accuracy assessment of the vessel fix position by the radial error including the reduced variant to compensate the systematic errors are suggested. The principal points of the research are supported by the graphic interpretation, and the given expressions are adjusted to the practical application and navigation systems software development. The computer simulation that shows the radial error of the fixed position by seven position lines is at least two times less than by any pair of position lines has been carried out. The formalization of the proposed methods in the automatic navigation systems or in autonomous ship control systems will enable the navigator on board or at operating the vessel remotely to solve the problems of the navigation information processing in coastal and congested waters on a new level.

Many engineering problems could be either reduced to or directly involve the mathematical problem of finding the shortest path in some confined space with obstacles. To solve this problem, graph theory and dynamic programming offers quite a lot of exact and heuristic algorithms that work with directed and undirected, weighted and unweighted, connected and disconnected graphs. All these methods are based on their own techniques of calculating the distance between the vertices, the choice of which is dictated by the convenience of implementation and methodological considerations. As a result, the resulted paths found by the algorithms usually are characterized by a certain abstract length, which is often difficult to convert into Euclidean one. Nevertheless, spatial problems in engineering practice often require an answer in terms of real physical distances. Specifically, such a task fully arises in engineering applications related to the design of seaports, namely, in the laying of routes of intra-terminal transport, power supply networks, in the design of approach channels. A modification of the most common method for finding the shortest paths, the wave orthogonal-diagonal algorithm, is described in the paper. It allows you to include the geometric characteristics of its individual sections in the calculation of the length of the found route, which makes it possible to accurately estimate the length in the sense of the Euclidean distance.

The influence of oil and its derivatives transportation processes, especially against the background of positive dynamics of their production, on the probability of environmental pollution is considered in the paper. It is noted that in such conditions it is very important to ensure timely preparedness for response and the ability to choose the most effective strategies, mainly using preventive measures to ensure emergency preparedness. The basis for the necessary set of measures is a forecast of the potential volume of a spill, allowing only the necessary number of technical or other assets to be planned for each area. It is emphasised that such a forecast is possible if the type of distribution by which it is described is understood. The type of distribution that best describes the behaviour of the oil spill volume as a random variable is defined in the paper. Statistical analysis methods have been used to examine the data presented in various databases. It is found that none of the common distributions that could theoretically describe the spill volume behaviour fulfil the accuracy condition. The observed chi-square (Pearson) criterion of agreement absolutely for all types of distributions exceeds the critical one many times, and it is obvious that the lognormal distribution law describes the behaviour of the considered random variable in the best way, which is visually confirmed by the frequency polygon and the smallest observed Pearson criterion. Using modern methods of hybridisation of distributions, it is proposed to conduct a study aimed at creating a universal distribution, presumably based on the lognormal distribution, which would accurately describe the behaviour of the random variable of oil spill volume. In addition, an approximate step function with a very high confidence coefficient can be used to predict the volume in each specific area.

The results of experimental studies of the process of bottom erosion during the construction of bridge supports under the protection of a sheet pile structure are presented. To protect the sheet piling box from the influence of ice floes during the period of ice drift, it is planned to install an ice-cutting protective device located upstream of the sheet piling box. In the process of conducting research, the principles of modeling the processes of river sediment transport taking into account the size of transported particles, non-erosive velocities and channel slopes are substantiated. Laboratory studies of the processes of forming erosion and alluvium are carried out for two cycles of parameters. At the same time, the influence of the ice-cutting device position relative to the sheet piling box on the amount of erosion and alluvium is studied. Experiments were carried out for various options of the ice cutter position relative to the sheet piling box; the ice cutter moved upstream along the axis of the tray with a step of 0.1 m (5 m for natural conditions). Based on measurements of bottom surface marks, two-dimensional erosion plans are constructed. For several options for the location of structures, the trajectories and directions of flow movement are determined by photographing the movement of surface floats, which makes it possible to create a grid of streamlines and determine the values of surface current velocities. An analysis of the velocity distribution over the surface and in the flow volume has shown that a horseshoe-shaped vortex is formed around the structure, with riffles and ridges appearing along its wings. A stagnation zone is established inside the “horseshoe”; in this zone the bottom remains relatively smooth. In the absence of an ice cutter, the main zones of soil erosion arise in the vicinity of the corners of the front face of the box, and alluviums form in the rear part of the structure. When installing an ice-cutting device in the shape of a triangle in front of the box, directed at an acute angle towards the oncoming flow, the erosion zones move to the vicinity of the corners lying at the base of the triangular ice cutter facing the box. The absolute values of erosion depth and alluvium height are reduced compared to the option without the ice cutter. When the ice cutter moves upstream relative to the box, a washout zone appears in the gap between the ice cutter and the box. The maximum values of erosion and alluvium occur in the absence of ice cutter and when placing the ice cutter at a distance of 200–300 mm from the box. The minimum values of erosion and alluvium are recorded when the ice cutter is placed close to the support box. With increasing flow rates and depths, the values of erosion and alluvium increase. Installing the ice-cutting device improves the hydraulic conditions of flow around the sheet piling box structure, which leads to a decrease in washout depths.

The approaches used by different classification societies to standardize calculated acceleration under ship motion during heavy lift cargoes transportation are analyzed in the paper. The methods of estimating the efficiency of securing devices of “non-standardized cargoes” carried on ships are investigated. The analysis of the parameters taken into account in determining the design accelerations at ship motion is carried out. Five representative vessels, which had previously carried heavy lift cargoes under different conditions, are selected. Computer modelling of these vessels motion at different course angles is performed in “SafeSea” programme, and calculated (conditional) amplitudes of motion regulated by the Rules of the Russian Classification Society are determined by “Stabedit” programme. The forced and own periods of onboard rolling are calculated in the specialised software complex “Anchored Structures” at variation of wave modes, loading states and values of metacentric height. The calculation results for representative vessels have shown a satisfactory matching of own and forced rolling periods. It is noted that in the range of 1.5 m ≤ h_{3 %} ≤ 4.5 m for the considered intervals of metacentric height, in most cases the forced rolling periods are slightly longer than the own ones. Based on the results of the research, the recommendations for determination of rolling amplitudes of inland and mixed navigation vessels of “P”, “O”, “M”, “O-PR”, “M-PR”, “M-SP” classes carrying heavy lift cargoes are given. The proposals on standardised design acceleration at motion of a ship carrying heavy lift cargo are also given for the mentioned classes of ships. The results of the research are included in the draft Guidelines for the assignment of design acceleration at rocking of mixed (river-sea) and inland navigation vessels and safety margins of heavy lift cargoes securing systems, developed for the Russian Classification Society

The topic of the work is the research of the problem of the practical realization of opportunistic navigation, which actually consists in the fact that the “signals of opportunity” are not optimized for global navigation according to their original purpose. A hypothesis about the possibility of strategic application of the navigation concept based on the principles of data integration with the objective existence of tactically surmountable difficulties is put forward. In the conditions of vulnerability of the global satellite system, an approach to use an additional source of combined signals in order to continuously ensure accurate geolocation of water transport vehicles is proposed. The comparative assessment confirms the comparability of the positioning error of alternative navigation with the data of classical satellite observations of mobile objects. An assumption about the effectiveness of spline modeling of the cartographic standard of informativeness for the practical organization of the basic principle of opportunistic positioning by analogy with the paradigm of correlation-extreme navigation is made. A computer visualization of a fixed fragment of the ocean gravitational field based on spline approximation is performed in order to optimize the problem of simultaneous localization and three-dimensional representation of the ship movement in a graphical environment unaffiliated with foreign software. A hybrid algorithm for mathematical synthesis of the navigational isosurface has been tested as a harmonized support for the navigation staff to implement the “terrain-referenced procedure” in the landscape coordinate space. The variants of the “ambiguity resolution” problem implementation in the issue of maximum integration of heterogeneous navigation data are considered. The probability of practical use of the opportunistic navigation postulates in marine applications, taking into account the “navigation gap” factor for leveling local satellite incapacity with a real possibility of countering malicious interception of ship control, is estimated. The expediency of using the factor of observational reckoning of the vessel path as an additional condition for navigation safety in the aspect of packet processing of the “signals of opportunity” slot is substantiated.

The problems of modeling the operation of classic (constant configuration) and variable vessel combination of barges by matrix routing methods are discussed in the paper. Regrouping the combination directly on the route allows you to operate a larger number of barges compared to a permanent combination, which increases its load capacity. The efficiency of water transport is determined by the volume of cargo delivered in relation to operating costs, which depend on the time the vessel is on the route. Additional stops during the voyage of the vessels combination for its reformation allow to increase the total cargo turnover, but lead to an increase in the voyage time, which is a certain contradiction, the solution of which is possible through the use of a variable approach to organizing the work of barge-tug combinations. The results of the mathematical apparatus development for describing the model of the barge-tug combinations movement on inland waterways are presented; the influence of turns on the change in the combinations speed and on the total voyage time is taken into account, and a particular task of regrouping the combination is additionally considered. The route from the Nizhnesvirsky lock to Ladoga Lake, on which turning points and places, where it is necessary to change the barge-tug combinations configuration to pass it are identified, is analyzed. For the mathematical description of the vessel movement along the route, a system of calculation matrices, which allows us to generalize the change and relationship of the speed and time parameters of the vessel movement with its route, including taking into account the time of regrouping the combination, is proposed. The main factors influencing the effectiveness of the combinations operation organization with their reorganization along the route are identified. As a basis for constructing matrices, it is proposed to use turning points, the system of which is formed in the form of a three-level model. The complex of matrices allows to obtain a quantitative presentation of the vessel movement and voyage time, while providing detailed parameters for the combination passage along the individual sections of the waterway, which in general is the basis of the developed information technology for intelligent control of the barge-tug combinations operation.

A methodology for assessing the possibility of ensuring salvage and rescue operations and oil and oil product spills response throughout the entire water area of the Northern Sea Route has been proposed. From 2024, it is planned to systematically develop year-round navigation along the Northern Sea Route, which will be associated with the need to ensure safety. At the moment, this possibility is severely limited due to the lack of multifunctional vessels of high ice class and technical means for spills response in ices. The methodological basis for determining the response time to marine oil spills in the Polar waters is laid down in the Polar Code, documents of the Maritime Safety Committee of the International Maritime Organization and documents of the Arctic Council, but their application is determined only by the hydrometeorological and geographical conditions at the place of the accident liquidation. Despite their broad and practical focus, the proposed approaches are only of a general methodological nature, which does not take into account the peculiarities of navigation in the waters of the Northern Sea Route, its length and zoning. The developed methodology largely overcomes these limitations and allows, at a qualitative level, to zone the waters of the Northern Sea Route according to three classification criteria. Two model examples are provided in the paper. The first example assumes that shipping occurs only in the western part of the Northern Sea Route, i. e. in the Kara Sea, the Ob Bay and the Yenisei Gulf, and in the eastern sector, shipping is completely absent; the second example assumes that navigation occurs throughout the entire water area. For each option under study, the entire water area is zoned according to the level of readiness, which is assessed as “high”, “medium” and “low” and depends on the presence of icebreakers and multifunctional vessels in the area. In the future, this methodology can be supplemented by an assessment of other factors, such as the influence of hydrometeorological conditions, ice conditions, navigation risks, forecasting the intensity of shipping and the selection of the necessary technical means for oil and petroleum product spills response.

Improving the process of fault detection of metal ship hull elements by using a probabilistic approach is considered in the paper. The most labor-intensive part of the defect detection report, namely, measurement and assessment of hull structures individual elements wear, accounting for more than 90 % of the total measurements, is reviewed. Defect detection of a ship hull means the examination, measurement and assessment of defects in each element of the ship hull in order to establish method and volumes of repairs that ensure its reliable operation until the next survey under specified operating conditions. The necessity of carrying out a preliminary calculation stage for defect detection is substantiated. It allows you to significantly reduce the number of measurements of hull structures elements, which will have a positive effect on reducing the cost of repair both due to a smaller number of measurements and the duration of repairs. It has been proved that using the probability approach to predict the residual thickness of individual elements also takes into account the effect on the total strength, which guarantees the reliability of the ship hull in operation. Tables to assess the technical condition of individual hull elements based on their level of wear have been developed, and a method for filling them has improved. The tables are made in two versions, namely, paper and electronic, the most convenient for a specific user — the designer of the defect detection report tables. A test example of using the electronic tables for assessing technical condition by wear level, which proves that the predicted residual thicknesses obtained by calculation will in all cases, be less, than similar ones obtained from measurements results, is carried out using a representative vessel. This proves the reliability and feasibility of using the preliminary defect detection stage, which is essentially an analogue of the concept of the zero stage in ship repair. Using the probability approach to determine the residual thicknesses will allow you not only to reduce the costs of defect detection of the hull itself, but also at early stages (before placing the ship on a slip or dock) to reduce the volume of hull structures repairs, and to choose the most appropriate and effective method of repair.

In the work to determine the spectrum of critical loads and the corresponding forms of a rectangular clamped panel (plate) buckling under the action of balanced tangential forces on its contour, the Bubnov-Galerkin method using polynomials in two coordinates is proposed. This problem of the ship skin element pure shift does not have an exact closed solution, and the known approximate solutions require an analysis of their accuracy and reliability. The aim of the work is to obtain and analyze analytical solutions using polynomials of various degrees. Approximating deflection functions satisfying all the boundary conditions of the problem are represented sequentially by polynomials of 10^th, 12^th, 14^th, 16^th and 18^th degrees in two coordinates with undefined coefficients. The solution of the main differential equation of the problem is found approximately in the integral sense, as a result of which homogeneous systems of linear algebraic equations with respect to unknown coefficients of polynomials are obtained. These systems contain a shear load as a parameter. To obtain eigenvalues (critical loads), the determinants of the systems are equated to zero. Numerical results are obtained in the Maple analytical computing system. For each approximation (polynomial), a power equation with respect to the critical load, the solution of which is paired values differing in signs is obtained. The forms of buckling are oblique waves. For a ship skin square panel, the first form of buckling is a single bulge along the diagonal of the panel. The second form is obtained in the form of two bulges directed in opposite directions (symmetrically-antisymmetrically with respect to the diagonals), etc. The numerical results are compared with the results of other authors. It is established that with an increase in the number of the polynomial terms, the initial critical loads and forms of buckling are specified, first of all.

The course instability problem of towed objects is discussed in the paper. It is noted that many non-selfpropelled vessels do not have directional stability, as a result of which they make oscillatory movements relative to the course of the towing ship. Increased yaw rate leads to a decrease in towing speed, an increase in loads on the elements of the towing device and a significant increase in the width of the running lane. These factors can lead to an emergency and significantly complicate the towing process, especially on inland waterways. Two main ways to increase directional stability are considered. These are towing “on V-line”, that is a system in which the towing rope is divided into two parts and attached to two points of the towed barge, located symmetrically relative to the centerline, and the installation of skegs in the stern. To determine the effect of these methods, tests of a model of the mixed riversea navigation oil barge 2731 are carried out in calm deep water conditions in the experimental tank of the Admiral Makarov State University of Maritime and Inland Shipping. The root end of the towing rope is attached to the pylon of the towing tank trolley and, thus, the reverse influence of the barge on the characteristics of the tug movement is not taken into account. Sixteen options are considered. The half-width of the running lane is taken as a criterion for the stability of barge movement. As follows from the test results, with increasing towing speed and towing rope length, the width of the running lane increases slightly. The installation of end washers on the skegs has no effect on the stability of the barge. To reduce the width of the running lane occupied by the barge, it is recommended to use towing “on the V-line” and use skegs with fixed flaps.

It is noted that during the flushing of ship systems and their elements, the mixed flow of water and air has proven itself well as a flushing medium. It has been experimentally established that there is a significant acceleration of the washing process and an increase in the number of flushed-out dirt particles. At the same time, the two-phase flushing method currently has a number of unsolved theoretical and practical problems. One of such tasks is to ensure a cavitation-free flushing regime. The issue of ensuring a cavitation-free regime when flushing ship pipelines with a twophase mixture during the passage of narrownesses stream is considered in the paper. It is known that the cavitation occurrence depends on a number of factors. The degree of each factor influence on the probability of cavitation occurrence is investigated. In this paper, an attempt to theoretically assess the development of cavitation in narrow technological jumpers is made. The main theoretical dependence of the maximum permissible diameter of the jumper on the main parameters of the mixed flow, as well as on the initial pressure of the flushing flow is determined. The main parameters of the mixed flow are the mass flow rate of the flushing water, the densities of the mixture phases, the mass content of air in the flow, the initial diameter of the pipeline and the compression ratio of the jet in a narrow section. A homogeneous mixture model is used in the theoretical study of cavitation phenomena in a two-phase flow. The main design dependencies for determining the maximum allowable diameter of the jumper depending on the main factors of the two-phase flow are defined in the paper. The influence of various factors on the development of cavitation phenomena is evaluated. Particular attention is paid to the choice of the flow diameter of the technological jumper depending on the mass flow rate of the flushing stream, the air content and the initial pressure.

The output and state regulators synthesis for ship control systems based on linear matrix inequalities using the CVX software package for solving optimization problems by the method of semi-definite programming is considered. Estimates parameters for regulators providing asymptotically stable systems regimes on Lyapunov inequalities solutions sets are obtained. An algorithm for controlling the ship course using a robust regulator in state feedback, followed by the use of CVX technologies to implement the minimum energy consumption control algorithm, is presented. The control vector estimation is reduced to the minimization of the L2 norm and it is performed in two stages, namely, the best mode is first determined, and then the mode under constraints is defined. The use of Lyapunov inequalities with the calculations implementation in CVX format on proprietary solvers has allowed us to obtain compact program texts and expand the set of restrictions introduced. In the algorithm for solving the boundary value problem of controlling a discrete model of an object, in contrast to existing optimization methods, a mode of transfer from the initial state to the final one with the right boundary, not necessarily equal to zero, is implemented. For a class of observable and controllable time–invariant systems, using the Krylov’s function contained in the MATLAB gallery of functions, L2‑norms to be minimized are formed. Examples of regulator calculations with a given degree of stability and optimal systems, confirming proposed solutions correctness, are given.

The purpose of the work is to ensure the monitoring and reliability of statistical data used for the analysis and forecasting of the production development on the basis of generalized indicators that take into account the volume of resources used and the ways of their use. An algorithm for parametric identification of production functions models from time series of statistical data using generalized regression, which provides the best estimation of the parametric optimization error by the method of least squares, is proposed. In contrast to existing assessment methods, neural networks are used to build models, which significantly expand the technical capabilities of modeling and contribute to improving the accuracy of calculations through the use of neural network technologies. It is shown that in order to solve the problems of this class, it is advisable to use generalized regression neural networks with simple training modes and high modeling accuracy. As a result, it is possible to propose an algorithm for quantitative assessment of the production functions parameters, which consists in the construction of a neural model with its subsequent use to fit the trajectory of the production model of a given structure to the obtained data by means of recurrent estimates of the vector of the desired coefficients at a given initial approximation. The proposed algorithm is demonstrated by estimating the parameters of the Cobb-Douglas production function and the discrete-dynamic model of the consumption function according to the corresponding statistical series. The calculations are performed using the functions of the Neural Networks package of the MATLAB software environment. The algorithm is applicable for quantitative estimation of the production models parameters with complex logical-probabilistic relationships, as well as for obtaining numerical values of target indicators and indicators for assessing the inland water transport development by statistical series and monitoring.

In the context of increasing digitalization of sea and river transport, the immersion of the entire transport infrastructure in the digital environment, the volume of information flows serving the transport process is increasing, and the requirements for information protection are increasing in conditions of an aggressive external information environment. In the digital environment, a software product must not only serve the document flow of transport chains, but also ensure its confidentiality. Automation of transport facilities (ships, platforms, berths, warehouses) management increases their potential vulnerability from unauthorized access to control systems; the latter must be taken into account in servicing programs, increasing their size (for example, there is a need to fragment coherent information blocks and their alternative routing). This, in turn, increases the risk of errors in the software products themselves and significantly complicates their structure. Risks of failures (including confidentiality violations) during the software operation that implements information exchange can entail significant material and reputational losses for the developer. If the developer is legally and functionally involved in the industry, such losses can and should be considered among the general range of risks in water transport. An important aspect of risk management, which until recently was practically not considered in a quantitative aspect within the framework of mathematical models, is the joint consideration of losses when a risk situation occurs and the developer’s costs associated with reducing the likelihood of such occurrences; the latter may entail a reduction in the total expected losses, formalized as the corresponding mathematical expectation. As a result, risk management can be formulated in terms of mathematical programming problems with different (discrete or continuous) sets of constraints and with different properties of objective functions.

The option of introducing an automated control system to ensure the safe passage of unmanned vessels on inland waterways has been explored. An analysis of domestic and foreign scientific and technical literature was carried out to determine conceptual provisions that allow choosing a rational way of interaction of this system with known ones. It is noted that the automated ships locking control system should provide the necessary level of navigation safety, and the implementation of this system should not affect the operation of other subsystems and metasystems. Currently, cases of constructing such systems for automated mooring of unmanned vessels at navigational hydraulic structures are unknown. Therefore, based on the engineering-cybernetic approach, a list of provisions that contribute to the successful organization of research of a conceptual and operational nature has been formulated. Conceptual provisions for the synthesis of structure and factors that allow you to develop a rational version of the system structure to obtain the greatest efficiency and safety of its operation are proposed. In addition to the development of locking control systems, an equally important task is the creation of technical means in the lock chamber, the operation of which can ensure the required level of security. Therefore, the process of mooring an unmanned vessel to an automated mooring ring, for a utility model of which the authors of this study had received a patent, is theoretically described. To achieve the goal of formulating the problems of developing and constructing an automated locking control system, an analysis of mooring devices used at shipping locks, including abroad, which confirms that fixed and movable mooring devices with vacuum grips are currently used, is carried out. A review of scientific and technical literature on the use of automatic and automated mooring systems makes it possible to develop proposals for organizing an auto-mooring system of a shipping lock to ensure the unmanned vessels passage, as well as to formulate the main problems and tasks that must be solved to ensure the passage of both unmanned and ordinary vessels.