• Journal of the Korean Magnetics Society
• /
• v.27 no.2
• /
• pp.63-69
• /
• 2017

Naval ships are particularly required to maintain acoustic and magnetic silence due to their operational characteristics. Among them, underwater magnetic field signals derived by ships are likely to be detected by threats such as surveillance systems and mine systems at close distance. In order to increase the survivability of the vessels, various techniques for reducing the magnetic field signal are being studied and it is necessary to consider not only the magnitude of the magnetic field signal but also the gradient of it. In this paper, we use the commercial electromagnetic finite element analysis tool to predict the induced magnetic field signal of ship's scaled model, and arrange the degaussing coil. And the optimum degaussing current of the coil was derived by applying the particle swarm optimization algorithm considering the gradient constraint. The validity of the optimal degaussing technique is verified analytically by comparing the magnetic field signals after the degaussing with or without gradient constraint.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.5
• /
• pp.638-645
• /
• 2020

The mast is the highest structure in a naval ship, and various communication and radar antennas are installed to achieve long-range communications and line of sight. The U.S. and European navy currently are adopting integrated mast to their new ships, as it can reduce the Radar Cross Section(RCS) of the new ships and thus improve survivability of the ship. In this paper, when other navies adopt integrated masts on new ships, types of antennas, according to the cases that the antennas are integrated on the integrated mast or not, are analyzed. Also the types of antennas and transmission techniques for the radio communication equipments of the Korean Navy are analyzed in various frequency bands. For adopting an integrated mast on Korean new ships, the effects of the ship RCS according to the types of antennas, the possibility of integration the antennas and the integrated mast and considerations were presented.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.5
• /
• pp.27-35
• /
• 2021

A technical review of Soviet/Russian supersonic anti-ship cruise missiles is presented. The supersonic anti-ship cruise missiles is one of the weapons for asymmetric power. The supersonic speed of the missiles is very useful both for attacking a time critical target and for improving target-penetration characteristics of the missile. The survivability of the missiles has also been increased by the improved concept of operation. Supersonic cruise missiles is greatly affected by the evolution of propulsion technology. Early supersonic cruise missiles adopt turbojet engines and rocket motors. The use of the integrated rocket-ramjet engine reduced the size of the supersonic missile, so today's supersonic cruise missiles are suitable to be deployed in various platforms. Nowadays, export versions of the missiles are actively being developed.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.4
• /
• pp.221-229
• /
• 2020

Naval ships could be seriously damaged by enemy attacks in battle. Moreover, this damage could be spread and deteriorated into a secondary accident. Secondary accidents that have adverse effects on naval ship's survivability, such as fire, flood, smoke extension, and patient occurrence, are defined as casualties. These casualties sharply degrade the survivability of naval ships. Furthermore, naval ships could be burned-out and sunk by casualties in isolated sea. Therefore, damage control and rapid suppression of the casualties in the naval ships is essential. This study was conducted in the establishment of suppression paths according to the characteristics of each casualty so that the developed system can support the rapid suppression in an emergency and even the training situation on a regular state. To establish the suppression paths, the two-dimensional numerical map is designed by converting the three-dimensional features of the naval ships, and the well known algorithms are compared to present the appropriate one for path finding problem on the naval ships. Finally, we devised a specific routing algorithm that fits the characteristics of each casualty in accordance with the Korean Navy's doctrines and handbooks of casualty suppression.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.11
• /
• pp.740-746
• /
• 2017

Infrared signatures emitted from hot exhaust gases generated by the internal combustion engine and generator of naval ships and from the metal surfaces of the funnel have become the targets of infrared homing missiles, which is the main cause of a reduced survivability of naval ships. The infrared signatures from the exhaust gas and the metal surface of a funnel can be reduced by installing an infrared signature suppression (IRSS) system on a ship. The IRSS system consists of three parts: an eductor that generates turbulent flow of the exhaust gas, a mixing tube that mixes the exhaust gas with ambient air, and a diffuser that forms an air film using the pressure difference between the inside and outside air. As a basic study to develop an IRSS system using domestic technology, this study analyzed the model test conditions of an IRSS system developed by an overseas engineering company and installed on a domestic naval ship, and a numerical heat-flow analysis was conducted based on the results of the aforementioned analysis. Numerical heat-flow analysis was performed using a commercial numerical-analysis application, and various turbulence models were considered. As a result, the temperature and velocity of the exhaust gas at the educator inlet and diffuser outlet and that of the metal surface of the diffuser were measured, and found to agree well with the measurement results of the model test.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.4
• /
• pp.103-110
• /
• 2018

Infrared signatures emitted from naval ships are mainly classified into internal signatures generated by the internal combustion engine of the ship and external signatures generated from the surface of the ship heated by solar heat. The internal signatures are also affected by the chemical components ($CO_2$, $H_2O$, CO and soot) of the exhaust plumes generated by the gas turbine and diesel engine, which constitute the main propulsion system. Therefore, in this study, the chemical composition ratios of the exhaust plumes generated by the gas turbines and diesel engines installed in domestic naval ships were examined to identify the chemical components and their levels. The influence of the chemical components of the exhaust plumes and their ratios on the infrared signatures of a naval ship was investigated using orthogonal arrays. The infrared signature intensity of the exhaust plumes calculated using infrared signature analysis software was converted to the signal-to-noise ratio to facilitate the analysis. The signature analysis showed that $CO_2$, soot and $H_2O$ are the major components influencing the mid-wave infrared signatures of both the gas turbine and diesel engine. In addition, it was confirmed that $H_2O$ and $CO_2$ are the major components influencing the long-wave infrared signatures.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.6
• /
• pp.322-330
• /
• 2020

This study deals with underwater explosion (UNDEX) characteristics of various non-explosive underwater shock sources for the development of non-explosive underwater shock testing devices. UNDEX can neutralize ships' structure and the equipment onboard causing serious damage to combat and survivability. The shock proof performance of naval ships has been for a long time studied through simulations, but full-scale Live Fire Test and Evaluation (LFT&E) using real explosives have been limited due to the high risk and cost. For this reason, many researches have been tried to develop full scale ship shock tests without using actual explosives. In this study, experiments were conducted to find the characteristics of the underwater shock waves from actual explosive and non-explosive shock sources such as the airbag inflators and Vaporizing Foil Actuator (VFA). In order to derive the empirical equation for the maximum pressure value of the underwater shock wave generated by the non-explosive impact source, repeated experiments were conducted according to the number and distance. In addition, a Shock Response Spectrum (SRS) technique, which is a frequency-based function, was used to compare the response of floating bodies generated by underwater shock waves from each explosion source. In order to compare the magnitude of the underwater shock waves generated by each explosion source, Keel Shock Factor (KSF), which is a measure for estimating the amount of shock experienced by a naval ship from an underwater explosionan, was used.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.4
• /
• pp.552-557
• /
• 2020

The Radar Cross Section (RCS) is a virtual region indicating the strength of a wavelength at which a radar signal is reflected and received. As the ship's RCS represents its own stealth performance and survivability, efforts have been made in various areas from design to construction to reduce the RCS. The RCS can be predicted using design drawings and CAD models, but it is necessary to measure the RCS at sea since sea clutter and multipath reflections occur in the sea environment. However, such RCS predictions and measured values provide only a simple relative magnitude to the user, and there has not been much research on this topic. In this paper, a missile countermeasure technique was studied using 3D RCS measurement data in an operating environment. The elevation and azimuth angle of the ship viewed from the missile were estimated using the location information of the missile, and the RCS value was inverted by mapping it to previously measured 3D RCS measurement data. In addition, by using the movement information of the missile, the RCS observed by the missile could be predicted in advance, and this method can be used to propose a response plan based on the maneuvering and chaff system.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.25 no.5
• /
• pp.495-501
• /
• 2015

Abroad warships are confronted with various menaces. The most critical threat of the warship is an Anti-Ship Missile (ASM). The ASM is able to be launched at a variety of environments and platforms. The ASM can evades conventional naval radar systems and electronic countermeasure techniques for providing a fatal damage to the warship. To cope with the ASM, an active decoy is an effective method to minimize the direct damage to the warship. The active decoy increases survivability of the warship because the ASM can lure pursuit of the active decoy instead of the warship. In this paper, our proposed method verifies an available response time of the active decoy to deal with the ASM using the active decoy of the warship in marine environments. We defined models of the warship, the ASM, and the active decoy, and executed simulation by combining the models. By the simulation result, the proposed method demonstrated the superiority of the mobile active decoy of the response time decoy among various active decoys, and estimated a protection area to prevent the ASM according the response time of the mobile active decoy against the ASM.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.06a
• /
• pp.343-345
• /
• 2011

대형 여객선은, "a ship is its own best lifeboat"라는 개념을 바탕으로 여객선의 안전성(survivability) 향상을 위한 설계가 요구되고 있으며, 이를 위하여, 사고가 발생하더라도 선박의 자체 추진력으로 안전하게 항구까지 귀항하여야 한다는, 여객선의 안전귀항(SRtP) 이라는 개념을 IMO SOLAS에 적용시켰다. SOLAS의 여객선 안전귀항 관련 조항은, 길이 120m 이상인 선박 또는 3개 이상의 주 수직격벽을 가진 선박으로서 2010년 07월 01일 이후 건조되는 여객선에 적용된다. 여객선 안전귀항 관련 조항은 화재와 침수사고에 적용되며, 사고분계점을 넘지 아니하는 사고가 발생할 경우 자체 추진력으로 여객선의 안전한 귀항을 위하여 사용 가능한 상태로 유지되어야 하는 시스템들에 대한 설계 기준, 사고분계점을 초과하는 화재 사고가 발생하였을 경우 질서 정연한 탈출 및 퇴선을 지원하기 위하여 작동상태의 유지가 요구되는 시스템 설계 기준, 사고분계점에 대한 정의, 사고 발생 후에도 여객 및 승무원의 건강을 유지 확보하기 위한 안전구역에 대한 기준들을 요구하고 있다. 본 연구에서는, 여객선 안전귀항 관련 법규들을 검토하고, 여객선 안전귀항을 위한 시스템들의 능력 평가 방법과 안전귀항 관련 조항 만족을 위한 시스템들의 요구사항들을 검토하였다.