• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.947-958
• /
• 2021

This study was conducted to provide basic data for crop monitoring by comparing and analyzing changes in reflectance and vegetation index by sensor of multi-spectral sensors mounted on unmanned aerial vehicles. For four types of unmanned aerial vehicle-mounted multispectral sensors, such as RedEdge-MX, S110 NIR, Sequioa, and P4M, on September 14 and September 15, 2020, aerial images were taken, once in the morning and in the afternoon, a total of 4 times, and reflectance and vegetation index were calculated and compared. In the case of reflectance, the time-series coefficient of variation of all sensors showed an average value of about 10% or more, indicating that there is a limit to its use. The coefficient of variation of the vegetation index by sensor for the crop test group showed an average value of 1.2 to 3.6% in the crop experimental sites with high vitality due to thick vegetation, showing variability within 5%. However, this was a higher value than the coefficient of variation on a clear day, and it is estimated that the weather conditions such as clouds were different in the morning and afternoon during the experiment period. It is thought that it is necessary to establish and implement a UAV flight plan. As a result of comparing the NDVI between the multi-spectral sensors of the unmanned aerial vehicle, in this experiment, it is thought that the RedEdeg-MX sensor can be used together without special correction of the NDVI value even if several sensors of the same type are used in a stable light environment. RedEdge-MX, P4M, and Sequioa sensors showed a linear relationship with each other, but supplementary experiments are needed to evaluate joint utilization through off-set correction between vegetation indices.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.3
• /
• pp.163-172
• /
• 2017

Porous insulation have been frequently used in a number of industries by minimizing thermal insulation space because of excellent performance of their thermal insulation. This paper devices an effective thermal conductivity prediction model. First of all, we perform literature survey on traditional effective thermal conductivity prediction models and compare each other model with heat transfer experimental results. Furthermore this research defines advanced effective thermal conductivity prediction models model based on heat transfer experimental results, the Zehner-Schlunder model. Finally we verify that the newly defined effective thermal conductivity prediction model has better performance prediction than other models. Finally, this research performs a transient heat transfer analysis of thermal protection system with a porous insulation using the finite element method and confirms validity of the effective thermal conductivity prediction model.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.488-494
• /
• 2019

Precision Guided Missiles after production and militarization have various characteristics that enable the final performance to be identified by conducting live-fire tests after long-term storage. Likewise, the performance and reliability of ${\bigcirc}{\bigcirc}$ Missiles, which are currently used by the Korean Navy, are also verified consistently by conducting live-fire tests after militarization. Specially, the live fire test at '00 year, which was conducted by Korean Navy, showed the result that 'Ring', which is a component of the canister's front cover, was jammed with wings for propulsion and then broke away from the canister during the missile launch process. This situation led to an interruption of the deployment of wings and finally affected the missile's flight performance. The results of a survey of the canisters of those missiles whose live fire tests were conducted successfully, based on the live fire test at '00 year, showed the 'Ring's separation from canisters. This raises recognition for the need to solve the problems of 'Ring's separation and breakaway. This study suggests an improvement derived by the result of live-fire tests and introduces the effect of final launch performance of ${\bigcirc}{\bigcirc}$ Missiles and test result after applying the improvement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.5
• /
• pp.460-470
• /
• 2009

In this paper, we described the implementation of the X-Band continuous-wave doppler radar for muzzle velocity measurement. The radar is consisted of microwave transceiver, signal processor, power board, and the measuring program was developed for the operating and field test. The operating frequency of doppler radar is able to set ${\pm}3\;MHz$ with 5 channel from the center frequency, and the output power is 25 dBm. The minimum receiving power is -117 dBm. The radar would obtain the doppler frequency from the artillery, and calculate accurate velocity point and then estimate muzzle velocity. The performance test for this radar was done with 155 mm at barrel and tripod mounted, and also compared the performance with the reference radar. As a result, the performance of the our new radar is equal with the reference one.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.1
• /
• pp.54-60
• /
• 2013

This paper presents a ground altitude determination algorithm using a laser altimeter and GPS for automatic take-off and landing of UAV. The characteristics of the laser altimeter was analyzed in ground tests and a low-pass filter was designed to reduce the effect of signal interruption due to reflectivity problem. The paper shows that a single sensor cannot measure ground altitude appropriately in terms of reliability and accuracy. To complement shortcomings of the laser altimeter, the linear Kalman filter was designed using DGPS vertical speed. Designed filter was validated and tuned through the steps of simulation, ground test and flight test. It was confirmed that the accuracy for automatic landing is achievable.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.2
• /
• pp.99-107
• /
• 2016

Test research on Infra-Red Thermography(IRT) technique in a supersonic wind tunnel has been conducted. Inadvertent technical difficulties and their solutions associated with the technique in running of the facility were examined. Two flow conditions at Mach number of 3 and 4 were considered. A double compression ramp model, that replicates realistic high-speed vehicle configuration, was used as test model. The present IR data were compared with shadowgraph visualization images and laminar computational fluid dynamics(CFD) results. It has been shown that the IRT technique can be used in quantifying various fluid dynamic features such as flow transition, separation and three-dimensional phenomena around the double compression ramp model.

• Aerospace Engineering and Technology
• /
• v.6 no.1
• /
• pp.157-164
• /
• 2007

For a GPS antenna to normally receive GPS satellite signals during full flight mission of a satellite launch vehicle, it should be installed on skin of the vehicle. The surface of a launch vehicle is drastically heated up due to aerodynamic heating effect during flight, so that the GPS antenna mounted on surface of the launch vehicle is directly exposed to extremely hot temperature environment. Hot temperature test specification of the GPS antenna, therefore, is severer than inner components. This paper describes that procedures and results of performance analysis of the GPS antenna for KSLV-I under hot temperature environment. The GPS antenna was not deformed physically and inner LNA(Low Noise Amplifier) operated normally without performance degradation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.1
• /
• pp.52-58
• /
• 2018

A Study on the dynamic characteristics of a rotor driven by a tipjet system in hovering condition was carried out. The sectional modeling was performed for the tipjet blade in which the flow path was inserted, and the dynamic characteristics analysis was conducted by modeling the components of the proposed rotor system. The analysis was conducted with respect to the rotational speed and the collective pitch. As a result of the analysis, it was checked that the proposed tipjet rotor did not have aeroelastic instability within the designed operating range. The tipjet test equipment was constructed in order to verify the analysis approach. It was confirmed that the proposed rotor was driven normally by tipjet. The non-rotating eigenmode measurement test and the rotation test were performed, and the validity was proved by comparing the test results and the analysis results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.9
• /
• pp.110-120
• /
• 2003

As the wooden aircraft in the early times has no way to let lightning flow when lighting flash attaches during flight, the aircraft got damage, or caught fire. Though all metal airplane was developed with an advent of aluminum, a lightning accident still occurred including a fire of a fuel tanks. Eventually, NACA declared problems in 1938, and an artificial lightning test began. III succession, FAA established Airworthiness Requirements for certification. The FAA committed test measures study for the protection of an airplane from lightning to SAE. SAE presented the test current and voltage waveforms that simulating natural lightning, and it is utilized on lightning protection certification of an airplane by public. A lightning effects of an airplane through an analysis of lightning mechanism was made in this technical note. Especially, lightning direct effects on aircraft are analyzed and lightning strike zones are described.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.1
• /
• pp.93-100
• /
• 2012

A telemetry signal occurs the line-of-sight problem by the effect of geography in flight test. A fixed relay system or a mobile relay system is used to solve that problem in general but we propose an airborne telemetry relay system using aircraft in this paper. An airborne telemetry relay system receives the telemetry signal of the test vehicle and then retransmits it to the ground system. The receiving antenna which is a phased array antenna can be tilted to ${\pm}30^{\circ}$ beam direction by beam-forming and track the rapidly moving test vehicle in effect. The relay pod which is mounted to an aircraft consists of the front antenna and the side antenna. It receives S-band signal and then down-converts the frequency to L-band signal. As a result, that can remove the frequency interference on an aircraft while retransmitting.