• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.104-109
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• 2023

The Cube Satellite Contest has been held six times as of August 2023, and a total of 21 teams have been selected. Fifteen Cube Satellites selected in previous contests were successfully launched and entered into low-Earth orbit. The six Cube Satellites selected in the sixth contest in 2022 are currently undergoing detailed design, and are scheduled to be launched in 2025 using a Korean launch vehicle. In this study, we analyzed the initial operation reports submitted by the selected teams of the Cube Satellite Contest in 2012, 2013, 2015, 2017, and 2019 to assess mission performance and identify causes of mission failure. Based on the submitted reports, an improvement scheme to enhance mission success for future Cube Satellites is proposed.

• Journal of Astronomy and Space Sciences
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• v.40 no.2
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• pp.79-88
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• 2023

On Aug. 4, 2022, at 23:08:48 (UTC), the Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, was launched using a SpaceX Falcon 9 launch vehicle. Currently, KPLO is successfully conducting its science mission around the Moon. The National Aeronautics and Space Administration (NASA)'s Deep Space Network (DSN) was utilized for the successful flight operation of KPLO. A great deal of joint effort was made between the Korea Aerospace Research Institute (KARI) and NASA DSN team since the beginning of KPLO ground system design for the success of the mission. The efficient utilization and management of NASA DSN in deep space exploration are critical not only for the spacecraft's telemetry and command but also for tracking the flight dynamics (FD) operation. In this work, the top-level DSN interface architecture, detailed workflows, DSN support levels, and practical lessons learned from the joint team's efforts are presented for KPLO's successful FD operation. Due to the significant joint team's efforts, KPLO is currently performing its mission smoothly in the lunar mission orbit. Through KPLO cooperative operation experience with DSN, a more reliable and efficient partnership is expected not only for Korea's own deep space exploration mission but also for the KARI-NASA DSN joint support on other deep space missions in the future.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.104-116
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• 2024

A satellite is ultimately verified by performing a coupled load analysis with the launch vehicle. To increase the accuracy of the coupled load analysis results, it is important to have good accuracy of the finite element model. Therefore, finite element model correlation is essential. In general, model correlation is performed by changing the material properties and thickness one by one, but this process takes a lot of time and cost. The current paper proposes an efficient model correlation method using optimization. Significant variables were selected through analysis of variance, and the time and cost required for analysis and optimization were reduced by using the Kriging surrogate model. The method proposed in this paper can be applied only with the vibration test results, and it has a great advantage in terms of efficiency in that it can significantly reduce the numerical calculation cost and time required.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.69-75
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• 2016

This paper covers the result of construction and start-up tests of the KSLV(Korea Space Launch Vehicle)-II combustion chamber hot-firing test facility. This facility was constructed from 2012 to 2014. Start-up test of this facility began in the second half of 2014. Oxidizer cold flow test, fuel cold flow test and cooling water cold flow test were carried out as start-up test. Afterward, ignition test of combustion chamber was accomplished. The result of ignition test is applied to set up start-up sequence of KSLV-II combustion chamber and utilized as base line data for hot-firing test of low and normal design point.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.109-118
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• 2018

Korea Aerospace Research Institute has developed a staged combustion cycle rocket (SCCR) engine with high specific impulse to send a 3-ton class satellite into geostationary orbit while conducting a Korean Space Launch Vehicle (KSLV) II project. The SCCR engine is different from the KSLV-II engine, which is an open cycle engine using a gas-generator. The SCCR engine with a closed cycle engine is composed of a pre-burner, a turbo pump, and a main combustor. The technology demonstration model (TDM0) was assembled and tested in the 7ton-class engine combustion test facility of Naro Space Center, and the combustion test was successfully conducted.

• Journal of the Korea Society for Simulation
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• v.24 no.1
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• pp.35-43
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• 2015

This research proposed a new method to evaluate the objective validity to launch smart transportation services that various stakeholders are complicatedly inter-connected. First of all, we have designed the fundamental business model to form the smart transportation services and defined the stakeholders taking part in the services. Also, the criteria to evaluate the economical validity has been proposed based on the relationship among stakeholders. Especially, in the case EV drivers and charging service providers, the economical validity depends on the scale of spreading. Therefore, we have compared the two extreme scenarios, the poor and stable level of EV spreading. According to the result, it may be said that EV drivers and charging service providers cannot be guaranteed the economical validity due to the burden of initial investment. On the contrary to this, suppliers of EV and charging gears may secure more than a certain level of profit. In addition, the government may have great profit due to reducing the CO2 emission and cost for importing energy sources. Therefore, it is needed to enhance the level of supporting EV drivers and charging service providers at the first stage. Also, the impact of the ratio of EV and charging service stations on the economical validity of smart transportation should be further investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.35-42
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• 2020

Electromechanical Actuator(EMA) for flight vehicles generally serves to control the fin deflection angle or the thrust vector angle. This paper deals with design and development of EMA for both aerodynamic control and thrust vector control. In this paper, a novel compact EMA is proposed that can simultaneously control both the tail fin and the jet vane with one actuator and detach the jet vane after vertical launch and rapid turn of the flight vehicle so as to increase efficiency during flying to target. To do this, we designed the EMA using a push-push link mechanism and derived a mathematical model. The mathematical model is validated by comparing simulation result and experimental data. The performance and reliability of the proposed EMA have been verified through performance test, environmental test and ground test. The proposed EMA is expected to be useful as an EMA for flight vehicles because of its simple and compact structure, as well as its performance and reliability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.738-746
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• 2019

Instead of hydraulic actuation systems, an electromechanical actuation system is more efficient in terms of weight, cost, and test evaluation in the thrust vector control of the 7-ton gimbal engine used in the Korea Space Launch Vehicle-II(KSLV-II) $3^{rd}$ stage. The electromechanical actuator is a kind of servo actuator with position feedback and uses a BLDC motor that can operate at high vacuum. In the case of the gimballed rocket engine, a synthetic resonance phenomenon may occur due to a combination of a vibration mode of the actuator itself, a bending mode of the launcher structure, and an inertial load of the gimbals engine. When the synthetic resonance occurs, the control of the rocket attitude becomes unstable. Therefore, the requirements for the stiffness have been applied in consideration of the gimbal engine characteristics, the support structure, and the actuating system. For the 7-ton gimbal engine of the KSLV-II $3^{rd}$ stage, the stiffness requirement of the actuation system is $3.94{\times}10^7N/m$, and the direct drive type electromechanical actuator is designed to satisfy this requirement. In this paper, an equivalent stiffness analysis model of a direct drive electromechanical actuator designed based on the stiffness requirements is proposed and verified by experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.20-25
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• 2019

In this paper, the structural weakness analysis and quality improvement of small fixed wing UAV of the hard landing type were studied. Unlike conventional aircraft, small UAV does not use runways because of its small size. Instead, small UAV use hand launch takeoff and hard landings. This type has many operational advantages because it can take off and land in a narrow space. But, the hard landing has a strong impact on the structure of the UAV and can cause serious damage. In order to analyze the exact cause of this phenomenon, the structural analysis was carried out using the 3D structural analysis program (ABAQUS) to identify the location of the fracture. And to improve the accuracy of the structural analysis, properties of the material were obtained through specimen test. As a result of the analysis, structural weaknesses were identified and improved. Thus, the validity of the study was verified by demonstrating the quality of enhanced structure through a real impact test at a higher level of 1.5 times the maximum impact during operation.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.1-11
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• 2021

POGO is a dynamic axial instability phenomenon that occurs in liquid-propelled rockets. As the natural frequencies of the fuselage and those of the propellant supply system become closer, the entire system will become unstable. To predict POGO, the propellant (oxidant and fuel) tank in the first stage is modeled as a shell element, and the remaining components, the engine and the upper part, are modeled as mass-spring, and structural analysis is performed. The transmission line model is used to predict the pressure and flow perturbation of the propellant supply system. In this paper, the closed-loop transfer function is constructed by integrating the fuselage structure and fluid modeling as described above. The pogo suppressor consists of a branch pipe and an accumulator that absorbs pressure fluctuations in a passive manner and is located in the middle of the propellant supply system. The design parameters for its design optimization to suppress the decay phenomenon are set as the diameter, length of the branch pipe, and accumulator. Multiple-objective function optimization is performed by setting the energy minimization of the closed loop transfer function in terms of to the mass of the pogo suppressor and that of the propellant as the objective function.