• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.72-86
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• 2019

SpaceX is currently leading the global launch market with the successful launch and recovery of Falcon 9 v1.2 Block 5. SpaceX developed Merlin engine, a kerosene gas generator engine, and continuously upgraded the engine from Falcon 1 to Falcon Heavy to increase payload weight. SpaceX suffered a lot of failures early on, but with the help of NASA, it was possible to overcome many crises and develop vehicles. In addition, it successfully developed reusable vehicles, which drastically reduced operating costs. Subsequent launch vehicles in Korea also need to be developed with reference to SpaceX's development strategy.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.137-147
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• 2015

Hypersonic vehicles exhibit distinct dynamic and static characteristics, such as unstable dynamics, strict altitude angle limitation, large control bandwidth, and unconventional system sensitivity. In this study, compromise relations between the dynamic features and static performances for hypersonic vehicles are investigated. A compromise optimal design for hypersonic vehicles is discussed. A parametric model for analyzing the dynamic and static characteristics is established, and then the optimal performance indices are provided according to the different design goals. A compromise optimization method to balance the dynamic and static characteristics is also discussed. The feasibility of this method for hypersonic vehicles is demonstrated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.855-862
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• 2017

Due to the weight reduction and miniaturization of satellites, there is a growing interest in low-cost launch vehicles, which are cheaper to launch than larger launch vehicles. One of the most cost-effective ways to reduce the cost of launch vehicles is the reuse of vehicles. Most companies that are developing low cost launch vehicles are also adopting a vehicles reuse approach. Along with this reuse purpose, the demand for environmentally friendly space launch vehicles has increased, so the choice of fuel used for low cost launch vehicles has also become very important. Methane and hydrogen-enriched compressed natural gas (HCNG), which makes more energy-efficient by adding hydrogen to methane, are considered to be the most suitable when considering other factors such as energy density among the fuels that are eco-friendly and capable of reusing the launch vehicles. This study investigated the trends of low-cost launch vehicle and rocket fuel in the world as a reference for setting up domestic space development after the development of Korea Space Launch Vehicle-II.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.59-66
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• 2016

India and China are capable of developing indigenous space launch vehicles, with the rocket technology transferred from the U.S., Western countries, and the Soviet Union, in the 1950s and 1960s. Barring the early 1990s, both countries are absent in the missile nonproliferation regime, and have no major space cooperation records with the U.S., since the establishment of the Missile Technology Control Regime in 1987. With the advent of the $21^{st}$ century, historic progress has been made in the U.S.-India space cooperation, which includes using Indian launch vehicles to launch U.S.non-commercial satellites. However, the U.S. is skeptical with regards to space cooperation and using Chinese space launch vehicle services. In this paper, we present the U.S. nonproliferation policy applied on launch vehicles of India and China, and different aspects of the policy will be examined to draw implications on Korean space activities.

• KIEAE Journal
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• v.14 no.4
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• pp.27-33
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• 2014

This study analyzed the electric vehicle recharging station status with recharging time limitation due to long waiting time, and figured out the user status by user interviews. And then this study verified the validity of hypothesis in terms of environmental design perspective and suggested layout of recharging station model. 21 recharging stations in Korea and station operation cases of 7 countries were examined. Except for the USA, the reality of electric vehicle recharging station today is the 1st proving stage focusing on the infrastructure construction of electric vehicle recharging station. It focuses on performance of recharging facility, use efficiency and operation environment of electric vehicle. About the effective waiting time of the user to use it should be studied. The current conditions of recharging station are as follows: Lack of independent recharging space, lack of facility that reduces external effect of recharging space, and lack of lounge for users during the waiting time. These three are essential factors constructing a suggesting model after basic layout, which needs proper measurement on the long recharging time and long waiting time. The essential factors are applied to electric vehicle recharging station layout so that users might use 'digital refresh" i.e. lounge and information contents service during the waiting time which provides convenience of recharging and emotional space with users. Such upgrade recharging station environmental model might resolve the burden of long recharging time which may contribute to the popularization of electric vehicles.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.91-102
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• 2020

Recently, a new space era has evolved in which commercial companies' led space development has begun. In this era, commercial companies actively participate in space development as the size of the small satellite market and small launch vehicle market is expanding. Through space development, developed countries are making efforts to reduce development, production, and operation costs to secure the competitiveness of small launch vehicles. In this study, the development trend of small launch vehicles and required technologies for space development were analyzed and summarized. Thus, research and development is urgently needed so that spin-on technologies, such as electric pumps and additive manufacturing, can be utilized for space development.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.9-16
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• 2019

In the present study, to investigate flows around space launch vehicles at mid-high altitudes efficiently, a three-dimensional unstructured mesh Navier-Stokes solver employing a Maxwell slip boundary condition was developed. Validation of the present flow solver was made for a blunted cone-tip configuration by comparing the results with those of the DSMC simulation and experiment. It was found that the present flow solver works well by capturing the velocity slip and the temperature jump on the solid surface more efficiently than the DSMC simulation. Flow simulations of space launch vehicles were conducted by using the flow solver. Mach number of 6 at the mid-high altitude around 86km was considered, and the flow phenomena at the mid-high altitude was discussed.

• Journal of KSNVE
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• v.6 no.6
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• pp.843-849
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• 1996

Locations and emission characteristics of noise source of motor vehicles are great important factors to control the road traffic noise in effective ways. From results of this study on emission characteristics of engine and exhaust noise, we could find that every noise emission of different kind of vehicles has smilar pattern. The main emission locations of engine noise for the front of vehicle became the space between the road surface and bottom of the body and radiator grill, and for the side of vehicle became the space between the road surface and bottom nearby the front wheel. In case of exhaust noise of passenger-car and light truck, all the highest sound intensity level located near surface of road. But it is hard to conclude the height of noise source of driving vehicles with only results of this study. So further studies are needed to check the emission characteristics of noise.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.522-534
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• 2017

According to the characteristics of salvo attack for the multiple flight vehicles (MFV), the design of cooperative guidance law can be converted into the consensus problem of multi-vehicle system through the concept of multi-agent cooperative control. The flight vehicles can be divided into leader and followers depending on different functions, and the flight conditions of leader are independent of the ones of followers. The consensus problem of leader-follower multi-vehicle system is researched by graph theory, and the consensus protocol is also presented. Meanwhile, the finite time guidance law is designed for the flight vehicles via the finite time control method, and the system stability is also analyzed. Whereby, the guidance law can guarantee the line of sight (LOS) angular rates converge to zero in finite time, and hence the cooperative attack of the MFV can be realized. The effectiveness of the designed cooperative guidance method is validated through the simulation with a stationary target and a moving target, respectively.

• Industrial Engineering and Management Systems
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• v.9 no.2
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• pp.178-194
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• 2010

To improve the ship operation in automated container terminals, it is important to schedule different types of handling equipment to operate synchronously. For example, a vehicle with container receiving and lifting capabilities is used to transport containers from a storage yard to a vessel and vice versa, while a triple quay crane (QC) can handle up to three 40-ft containers simultaneously. This paper discusses the manner in which vehicles should be assigned to containers to support such multi-lifts of QCs by using information about the locations and times of deliveries. A mixed-integer programming model is introduced to optimally assign delivery tasks to vehicles. This model considers the constraint imposed by the limited buffer space under each QC. A procedure for converting buffer-space constraints into time window constraints and a heuristic algorithmfor overcoming the excessive computational time required for solving the mathematical model are suggested. A numerical experiment is conducted to compare the objective values and computational times of the heuristic algorithm with those of the optimizing method to evaluate the performance of the heuristic algorithm.