• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.746-752
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• 2017

High test hydrogen peroxide has been widely developed as green propellant for thrusters. Hydrogen peroxide is decomposed in the catalyst bed to produce the thrust. Catalyst bed design optimization is considered through existing model for catalyst beds. To verify the model, static firing tests were conducted under various conditions using a 100 N scale $H_2O_2$ monopropellant thruster. Temperature and pressure estimations from the model were well correlated to the experimental data. The model is used to obtain optimal design parameters by analyzing the catalyst capacity and pressure drop data for various simulated conditions. Catalyst beds can be optimized from the analysis of the catalyst capacity and pressure drop correlation through catalyst bed modeling.

• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.21-25
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• 2009

The ship without thrusters and special propulsion system is supported by the tug boats during berthing and unberthing. The orders to tug boats are made by a pilot. If the positions of ship, tug boats and port are displayed in 2D map, it will be helpful to pilots. In this research, a network-based pilot supporting system(NPSS) has been conceptually designed NPSS, necessary for safe and efficient pilot, has two main functions. One is the monitoring of the situation of berthing and unberthing. And the other is the automatic calculation of the tug forces considering environmental conditions. The NPSS is designed on the basis of network system around the harbor. The NPSS will be validated using ship-handling simulator in the future.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2162-2166
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• 2016

This paper describes the implementation of AUSV system for sonar image acquisition to survey the seabed. The system is controlled by Feed Forward PID algorithm on the vessel for bearing of the thrusters composed of motion sensor and DGPS which calculates the differences between the current location and the destination location for longitude and latitude based on GPS coordinates. As experimental results, the bearing control performance is good that the error distance from the destination positions are under 6m in total survey track of 1km. And the sonar image deviation of a object is under 12 pixels from the manned survey method, which the comparison with the total image quality is almost the same as the manned survey one. Thus the proposed AUSV system is a new method of system can be utilized at the limited survey areas as the surveyor should not be able to approach on sea surface by onboard vessel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.100-103
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• 2012

The blending method that is an addition of small quantity of fuel was used to increase the performance of green propellant thruster. 90 wt.% hydrogen peroxide as a green propellant was selected, and ethanol was used as a blended fuel. The o/f ratio was chosen as 50 which has higher theoretical performance than 98 wt.% hydrogen peroxide. The chamber temperature of blended hydrogen peroxide was higher than adiabatic chamber temperature of hydrogen peroxide. Therefore, performance can be improved by ethanol blending. Several catalyst and its support were compared to find appropriate catalyst for decomposition and combustion of ethanol blended hydrogen peroxide. As a experimental results, Pt was suitable, but $MnO_2$ had a chamber instability when it was reused. The ${\alpha}-Al_2O_3$ which is high heat-resistant support showed very unstable performance in both Pt and $MnO_2$ catalyst since it has low decomposition performance.

• Journal of Ocean Engineering and Technology
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• v.35 no.5
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• pp.313-326
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• 2021

A submerged body with varied control inputs can execute large drift angles and large angles of attack, as well as basic control such as straight movement and turning. The objective of this study is to analyze the dynamic characteristics of a submerged body comprising six thrusters and six control planes, which is capable of a large drift angle and angle of attack motion. Virtual captive model tests via were analyzed via computational fluid dynamics (CFD) to determine the dynamic characteristics of the submerged body. A test matrix of virtual captive model tests specialized for large-angle motion was established. Based on this test matrix, virtual captive model tests were performed with a drift angle and angle of attack of approximately 30° and 90°, respectively. The characteristics of the hydrodynamic force acting on the horizontal and vertical surfaces of the submerged body were analyzed under the large-angle motion condition, and a model representing this hydrodynamic force was established. In addition, maneuvering simulation was performed to evaluate the standard maneuverability and dynamic characteristics of large-angle motion. Considering the shape characteristics of the submerged body, we attempt to verify the feasibility of the analysis results by analyzing the characteristics of the hydrodynamic force when the large-angle motion occurred.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.78-84
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• 2020

The performance of pintle thruster is analyzed by using the pintle thruster performance analysis model which integrating the element models introduced in Part I. To verify the performance analysis, the results of the developed program are compared with the experimental data of kerosene/hydrogen peroxide liquid pintle thrusters. Based on the results, the characteristics of the pintle thruster are analyzed. The sensitivity analysis is performed to investigate the effect of thruster shape and operation parameters on performance characteristics using both OAT and scatter plot methods. The four performance parameters such as droplet diameter, film flow rate, O/F ratio, and nozzle throat diameter are evaluated to investigate their effects on characteristic speed, combustor pressure, and specific thrust.

• Journal of Navigation and Port Research
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• v.44 no.6
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• pp.494-500
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• 2020

Maneuvering vessels in the harbor is an interesting problem in marine cybernetics. The vessel, operated by the pilot and moving very slowly in shallow water, usually is assisted by thrusters, the main propulsion system, and tugboats. In this paper, we suggest a new vessel berthing technique using dampers (cylinder-type fenders) and a system of winches for complex and dangerous berthing situations. We found that control of the fender stroke and rope tension enabled a safe and quick berthing process. The effectiveness and usefulness of this berthing system was verified using a ship of about 2,000 tons.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.69-77
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• 2020

A quasi one-dimensional multi-phase reaction flow analysis code is developed for the performance analysis of liquid pintle thrusters. Unsteady flow field, droplet evaporation, finite reaction and film cooling models are composed as the major models of the performance analysis. The droplet vaporization takes account of Abramzon's vaporization model, and the combustion employs a flamelet model based on detail chemical reactions. Shine's model is applied for the film cooling calculation. To verify each model, the Sod shock tube, single droplet vaporization, kerosene droplets combustion, and film length are evaluated.

• Journal of Space Technology and Applications
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• v.2 no.1
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• pp.30-40
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• 2022

This paper illustrates the trajectory design of drift distance recovery after initial launch and proximity operation when verifying rendezvous/docking technology using nanosatellites. The rendezvous/docking is a technology that is the basis of on-orbit servicing technology and is a preemptive process essential for approaching a target object. In particular, since it is difficult to verify in space, nanosatellites have recently been used to reduce the risk and cost of the development stage. Therefore, this paper not only introduces the configuration and specifications of thrusters for nanosatellites but also designs relative trajectories that can take into account the thrust limitations which come from the small size and low power of nanosatellites. In addition, we intend to be helpful in later designing scenarios according to the improvement of available thruster performance through comparison of trajectories and thrust usage with cases without thrust limitations.