• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.551-558
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• 2016

We analyzed wind speed over South Korea for HALE UAV(High Altitude Long Endurance Unmaned Aerial Vehicle) flight safety. Annual variation of wind speed at 200 hPa showed that winter season was stronger than summer. According to latitude, wind speeds in January and August were found to be $52{\sim}74m\;s^{-1}$ and $15{\sim}26m\;s^{-1}$, respectively. Wind speed was stronger(weaker) at lower latitudes than higher latitudes in winter(summer). Frequency(%) of wind speed less than threshold value($18m\;s^{-1}$) for the operation date was investigated. The days showing the frequency greater than 60 % in all altitudes of surface ~ 50 hPa showed the range of 1 ~ 33 days at 7 stations. Operation date was the longest period at Gosan. The appropriate date of HALE UAV operation at Gosan and Osan is considered as the middle of July ~ middle of August and end of July ~ early August, respectively. These results can be used to determine the operation date of HALE UAV.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.666-673
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• 2023

The runway occupancy time of landing aircraft is an important factor in determining runway capacity. The purpose of this study is to suggest improvement measures for runway occupancy time to improve the operation of existing airports. In order to derive improvement measures, a comparative analysis was conducted on the effectiveness of improvement using aircraft operation status data for specific days at the case airport. The FAA REDIM model was used to analyze the improvement plan, and the improvement application function of the model was used to confirm the effect of improving runway capacity by adding a rapid escape taxiway to an airport without a rapid escape taxiway. This study's approach can be applied to the derivation of runway improvement measures and preliminary prediction of effectiveness, and it presents cases that can be applied to future airport construction projects or airport improvement projects.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.512-521
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• 2017

This paper reports development process of a university-based sounding rocket using simplified hybrid rocket propulsion system for low-altitude flight application. A hybrid propulsion system was tried to be designed with as few components as possible for more economical, simpler and safer propulsion system, which is essential for the small scale sounding rocket operation as a CanSat carrier. Using blow-down feeding system and catalytic ignition as combustion starter, 250 N class hybrid rocket system was composed of three components: a composite tank, valves, and a thruster. With a composite tank filled with both hydrogen peroxide($H_2O_2$) as an oxidizer and nitrogen gas($N_2$) as a pressurant, the feeding pressure was operated in blowdown mode during thruster operation. The $MnO_2/Al_2O_3$ catalyst was fabricated for propellant decomposition, and ground test of propulsion system showed the almost theoretical temperature of decomposed $H_2O_2$ at the catalyst reactor, indicating sufficient catalyst efficiency for propellant decomposition. Auto-ignition of the high density polyethylene(HDPE) fuel grain successfully occurred by the decomposed $H_2O_2$ product without additional installation of any ignition devices. Performance test result was well matched with numerical internal ballistics conducted prior to the experimental propulsion system ground test. A sounding rocket using the developed hybrid rocket was designed, fabricated, flight simulated and launch tested. Six degree-of-freedom trajectory estimation code was developed and the comparison result between expected and experimental trajectory validated the accuracy of the developed trajectory estimation code. The fabricated sounding rocket was successfully launched showing the effectiveness of the simplified hybrid rocket propulsion system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1353-1358
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• 2021

IoT (Internet of Things) emerges from various technologies such as communications, micro processors and embedded system and so on. The IoT has also been used to UAV (Unmanned Aerial Vehicle) system. In manned aircraft, a pilot and co-pilot should control FCS (Flight Control System) with FBW(Fly By Wire) system for flight operation. In contrast, the flight operation in UAV system is remotely and fully managed by GCS (Ground Control System) almost in real time. To make it possible the communication channel should be necessary between the UAV and the GCS. There are many protocols between two systems. Amongst them, MAVLink (Macro Air Vehicle Link) protocol is representatively used due to its open architecture. MAVLink does not define any securities itself, which results in high vulnerability from external attacks. This paper proposes the method to enhance data security in GCS network by applying cryptographic methods to the MAVLink messages in order to support safe UAV operations.

• Journal of Aerospace System Engineering
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• v.10 no.2
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• pp.14-21
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• 2016

In this study, we proposed a water rocket CULV-1 (Chosun University Launch Vehicle-1). Unlike a conventional water rocket, CULV-1 can perform the booster rocket, fairing, and payload separation like an actual launch vehicle and also the imaging data acquisition. The conceptual and critical design of the proposed CULV-1 have been performed considering the operation characteristics. The verification tests have been performed from subsystem to system level in accordance with the established test specifications and verification procedures. Through the final launch test of the flight model, we have verified the design effectiveness of the proposed separation mechanisms for water rocket applications and the mission requirements of the CULV-1 also have been complied.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.819-826
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• 2011

The proton exchange membrane fuel cell (PEMFC) is regarded as the most promising alternative power sources for unmanned aerial vehicle (UAV) due to its high energy density and silent operation. Since there are many load changes during UAV flight, thermal management is one of the important factor for the performance of PEMFC. In order to reduce the UAV weight for the stable operation of UAV, thermal management system (TMS) studied in this work does not use the fan but use the air flowing into UAV by UAV flight. In order to develop the passive type heat exchanger (HEX) for 1kW PEMFC, four types of HEXs are fabricated and their cooling performances are compared. The parametric study on the cooling performance of HEXs has performed with the variation of operating parameters such as mass flow rates and inlet temperature of air and coolant. Type 4 has the best performance in every case. This study can be helpful to achieve the optimal design of HEX for PEMFC powered UAV.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.656-657
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• 2010

The ground oxidizer supply system in the launch site of NARO space center had operated 9 times from the start of tests with ILV on May, 2009 to the 2nd flight test of the NARO vehicle. This system operated successfully for twice launches of the NARO vehicle. To judge the successful operation of the ground facility, it should have reproducibility and reliability. In this report, we have analyzed the liquid oxygen consumption of the system to judge of its reproducibility and it can be a reference for using this system for the next generation of KSLV system.

• Journal of Mechanical Science and Technology
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• v.17 no.8
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• pp.1234-1245
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• 2003

An experimental study was carried out to investigate the reduced frequency effect on the near-wake of an elliptic airfoil oscillating in pitch. The airfoil was sinusoidally pitched around the center of the chord between -5$^{\circ}$and ＋25$^{\circ}$angles of attack at an airspeed of 3.4 m/s. The chord Reynolds number and reduced frequencies were 3.3 ${\times}$10$^4$, and 0.1, 0.7, respectively Phase-averaged axial velocity and turbulent intensity profiles are presented to show the reduced frequency effects on the near-wake behind the airfoil oscillating In pitch. Axial velocity defects in the near-wake region have a tendency to increase in response to a reduced frequency during pitch up motion, whereas it tends to decrease during pitch down motion at a positive angle of attack. Turbulent intensity at positive angles of attack during the pitch up motion decreased in response to a reduced frequency, whereas turbulent intensity during the pitch down motion varies considerably with downstream stations. Although the true instantaneous angle of attack compensated for a phase-lag is large, the wake thickness of an oscillating airfoil is not always large because of laminar or turbulent separation.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.42-47
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• 2008

The power control system of Smart UAV is similar to the propeller pitch governing concept of turboprop aircraft. The pilot adjusts the engine power directly and the pitch governor controls the propeller pitch to maintain the propeller rotational speed. The electronic engine controller(EEC) of PW206C engine developed for helicopter is not fit for the power control concept of Smart UAV, and therefore the manual back-up system of PW206C engine is used for the engine power control of Smart UAV. Engine performance estimation program is used to predict the control range of power lever angle(PLA) according to the variation of engine output shaft speed, flight altitude and flight speed. These data provide a guide for the PLA control in manual mode operation.

• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.467-478
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• 2019

Purpose: The purpose of this paper is to improve quality for water infiltration to FCISA during military aircraft operation. Methods: A series of troubleshooting studies were conducted to identify the root cause of the water infiltration and reproduce the defects through various simulation tests. And design improvement measures were derived, and countermeasures were taken to prevent recurrence of moisture inflow defects. Conclusion: FCISA operates a very important role in the operation of military aircraft, and defects due to water infiltration are very fatal to flight safety. In this study, the root cause was identified and the design improvement to prevent recurrence was carried out through the failure investigation performed in this study, and the FCISA was improved so that the flight safety was not affected. The results of this study will be valuable back data that can be reflected in the design process through Lessons-Learned in the design phase of the aircraft that will be developed in the future.