• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.3
• /
• pp.147-155
• /
• 2022

The accumulated ice and snow during the operation of aircraft and railway vehicles can degrade aerodynamic performance or damage the major components of vehicles. Therefore, it is crucial to predict the temporal growth of ice for operational safety. Numerical simulation of ice is widely used owing to the fact that it is economically cheaper and free from similarity problems compared to experimental methods. However, numerical simulation of ice generally divides the analysis into multi-step and assumes the quasi-steady assumption that considers every time step as steady state. Although this method enables efficient analysis, it has a disadvantage in that it cannot track continuous ice evolution. The purpose of this study is to construct a surrogate model that can predict the temporal evolution of ice shape using reduced-order modeling. Reduced-order modeling technique was validated for various ice shape generated under 100 different icing conditions, and the effect of the number of training data and the icing conditions on the prediction error of model was analyzed.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.2
• /
• pp.47-59
• /
• 2022

Liquid hydrogen/liquid oxygen rocket engines with highest specific impulse have been developed since the 1950s and used until now to maximize the capability of space launch vehicles. Domestic liquid hydrogen infrastructures for the production, transportation and distribution are being expanded at world-class level with the rise of hydrogen economy, which is a great opportunity for the performance enhancement for indigenous space launch vehicles. In this paper, feasibility of applying liquid hydrogen as a propellant is investigated in various aspects. The status of domestic liquid hydrogen infrastructure, the technologies required for liquid hydrogen engines, and operational aspects for safe handling of hydrogen are reviewed. In addition, test facilities for developing hydrogen engines are introduced briefly.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.2
• /
• pp.79-95
• /
• 2022

Since space exploration began in the 1950s, numerous upper stage engines have been developed and used based on various design concepts. In this paper, information of upper stage engines which developed or developing is analysed and their characteristics and performance are summarized. These days, there are many cases of commercial heavy launch vehicles applying upper stage engines using liquid hydrogen with expander cycle which launched recently. Engines operating by Kerosene seem to be close to its theoretical maximum performance based on past experiences. Meanwhile, engines using methane propellant, which has recently become an issue, are also undergoing many developments because of various advantages. Recently, private companies are actively participating in launch vehicle market, and there are many cases in which the government and companies jointly research of next-generation engine.

• The Journal of Korea Robotics Society
• /
• v.18 no.1
• /
• pp.1-9
• /
• 2023

This paper presents an optimal path planning strategy for aerial searching and surveying of a user-designated area using multiple Unmanned Aerial Vehicles (UAVs). The method is designed to deal with a single unseparated polygonal area, regardless of polygonal convexity. By defining the search area into a set of grids, the algorithm enables UAVs to completely search without leaving unsearched space. The presented strategy consists of two main algorithmic steps: cellular decomposition and path planning stages. The cellular decomposition method divides the area to designate a conflict-free subsearch-space to an individual UAV, while accounting the assigned flight velocity, take-off and landing positions. Then, the path planning strategy forms paths based on every point located in end of each grid row. The first waypoint is chosen as the closest point from the vehicle-starting position, and it recursively updates the nearest endpoint set to generate the shortest path. The path planning policy produces four path candidates by alternating the starting point (left or right edge), and the travel direction (vertical or horizontal). The optimal-selection policy is enforced to maximize the search efficiency, which is time dependent; the policy imposes the total path-length and turning number criteria per candidate. The results demonstrate that the proposed cellular decomposition method improves the search-time efficiency. In addition, the candidate selection enhances the algorithmic efficacy toward further mission time-duration reduction. The method shows robustness against both convex and non-convex shaped search area.

• The Journal of Bigdata
• /
• v.7 no.2
• /
• pp.129-137
• /
• 2022

With the development of the 4th industry, the logistics industry is evolving into a smart logistics system. However, ship work that transports vehicles is progressing slowly due to various problems. In this paper, we propose an stowage automation algorithm that can be used for cargo loading of vehicle carriers that shortens loading and unloading work time. The stowage automation algorithm returns the shortest distance by searching for a loading space and a movable path in the ship in consideration of the structure of the ship. The algorithm identifies walls, ramps and vehicles that have already been shipped, and can work even with randomly placed. In particular, it is expected to contribute to developing a smart logistics system for vehicle carriers by referring to the ship's master plan to search for vehicle loading and unloading space in each port and predict the shortest movable path.

• Journal of the Korean Society of Industry Convergence
• /
• v.7 no.3
• /
• pp.273-279
• /
• 2004

There are several ways to solve parking problem in the downtown One of them is to manage parking efficiently, that is, to raise use-efficiency of parking place and to help drivers to select easily. When we manage the parking place m the block efficiently, It can prevent disproportion that some parking space is over capacity and the other parking one is under. It causes not only the disproportion of economic efficiency but also the congestion of local road. The precondition to manage parking efficiently is to analyse the parking characteristics. In this study we found out the characteristics of parking vehicles by analyzing the turnover per parking mesh and occupancy rate And we build up total D/B by collecting every information about parking space. We developed the Parking Management System by using GIS with D/B and digital map. The efficient Parking Management System is for convenience of drivers and efficient usage of parking space. And this system is also the basic study to be developed as the total Parking Management System by upgrading every information.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.147-150
• /
• 2005

Space launch vehicles mainly use the liquid-propellant propulsion system which has easy thrust control ability and high specific impulse for that the payload like satellite and spacecraft should be entered into exact orbit. However, the liquid-propellant propulsion system is very difficult to develop because it is more complicate than the solid rocket propulsion system and demands very high technology. In space launch vehicle developing procedure the system design level is very important thing to reduce cost, shorten schedule, and improve the performance. The system design process was introduced for selecting the best liquid-propellant propulsion system on this paper.

• Aerospace Engineering and Technology
• /
• v.7 no.2
• /
• pp.123-130
• /
• 2008

Flight safety analysis, which includes risk estimation for the various abnormal flight modes in addition to normal flight, has to be performed necessarily to guarantee launch safety for the operation of space launch vehicles. For this purpose, a dedicated system has been developed such that all the necessary repetitive computations, result reports, and graphical presentations can be performed inside a single system for user convenience. In addition, the developed system is capable of representing computed results on a three dimensional Earth for the realistic presentation. The developed Flight Safety Analysis System will be employed for the launch operation of Korea Satellite Launch Vehicle-I.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.387-392
• /
• 2007

Turbomachinery such as turbines, pumps and compressors, which are installed in transportation systems such as warships, submarines and space vehicles, etc., often perform crucial missions and are exposed to potential dangerous impact environments such as base-transferred shock forces. To protect turbomachinery from excessive shock forces, it may be needed to accurately analyze transient responses of rotors, considering the dynamics of mount designs to be applied with. In this study a generalized FE transient response analysis model, introducing relative displacements, is firstly proposed to accurately predict transient responses of a flexible rotor-bearing system with mount systems to base-transferred shock forces. In the transient analyses the state-space Newmark method of a direct time integration scheme is utilized, which is based on the average velocity concept. Results show that for the identical mount systems considered, the proposed FE-based detailed flexible rotor model yields more reduced transient vibration responses to the same shocks than a conventional simple model or a Jeffcott rotor. Hence, in order to design a rotor-bearing system with a more compact light-weighted mount system, preparing against any potential excessive shock, the proposed FE transient response analysis model herein is recommended.

• Environmental Engineering Research
• /
• v.20 no.4
• /
• pp.397-402
• /
• 2015

SCR has been popularly approved as one of the most effective means for NOx emission control in heavy-duty and medium-duty vehicles currently. However, high urea dosing would lead to ammonia slip. And $NH_3$ sensor for vehicle emission applications has not been popularly used in real applications. This paper presents experimental studies on the diesel engine urea-SCR system by using a double NOx sensor system that is arranged in the downstream of the SCR catalyst based on ammonia cross-sensitivity. It was shown that the NOx conversion efficiency rised as $NH_3/NOx$ increases and the ammonia slip started from the $NH_3/NOx$ equal to 1.4. The increase of temperature caused high improvement of the SCR reaction rate while the space velocity had no obvious change. The ammonia slip was in advance as catalyst temperature or space velocity increase and the ammonia storage reduced as catalyst temperature or space velocity increase. The NOx real-time conversion efficiency rised as the ammonia accumulative storage increase and reached the maximum value gradually.