• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.499-506
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• 2015

Global navigation satellite systems (GNSS) is operating widely in civil and military area. GNSS signals, however, can be easily interfered because its signal is vulnerable to jamming. Thus, a sort of backup or alternative system is needed in order that the navigation performance is assured to a certain degree in case of GNSS jamming. In order to suggest a series of backup or alternative system of regional navigation, in this paper, we introduced a high altitude long endurance unmanned aerial vehicle (HALE UAV) with pseudolites using inverted GPS and transceiver system. We simulated the positioning error of the regional navigation system using HALE UAV with inverted GPS or transceivers concepts. We estimated the position error of HALE UAV calculate user position errors based on the position error of HALE UAV and general pseudorange error.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.922-931
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• 2017

This research paper describes design procedures and those verification with multi-body dynamic analysis and an experiment for the development of an unprecedented type of canister cover, named as the separating cover. In order to overcome drawbacks from the precious rupture type and actuator driven cover, the separating cover was suggested. It has the simplest structure composed of the previously developed explosive bolt and a spring-lever driven system. First of all, mechanical feasibility with proposed design parameters based on mathematical modeling was confirmed through dynamic analysis and then its results showed good agreement with the followed empirical results acquired from a high speed camera. On top of that, a parametric study was conducted to identify the effect of each design parameter on separating performance. It is highly expected that this research contributes to provide military industries with a brand new canister cover having simplicity and cost efficiency and thus it will be very useful in MLRS(Multiple Launch Rocket System).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.590-596
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• 2020

The fabric used for military winter inner clothing(top) is quilted with padded cotton to provide warmth. This quilting fabric is generally manufactured with yarns that intersect and are sewn substantially between the fabric and cotton. Thus, it is impossible to separate the fabric and cotton once after the quilting fabric is manufactured, which can result in a significant loss of fabric and cotton when separated. In this study, after fabricating the quilting fabric, we investigated a method to stabilize change rate of thickness and increase the warmth keeping property through subsequent processing without damaging the fabric. A relatively method of passing the quilting fabric through a part of the cotton production facility was used generally, and the following results were obtained. This indicates that after the quilting fabric was manufactured, the warmth keeping property was improved through the subsequent processing steps, so that the change rate of thickness due to washing was stabilized.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.84-92
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• 2020

This paper describes the estimation method of cable fault location in rocket motors using M-sequence (Maximal Length Sequence). In order to estimate the location of a cable fault, three methods have been usually used: TDR (Time Domain Reflectometry), FDR (Frequency Domain Reflectometry), and TFDR (Time-Frequency Domain Reflectometry). However, these methods suffer the disadvantage of requiring users to be close to a test field, which is dangerous. The estimation method of cable fault location using M-sequence is proposed to solve this problem. The proposed method can make use of DAS (Data Acquisition System). The experiments were three cases: damaged, open, and short. The RG-58 coaxial cable was used in the experiments. As a result, the proposed method has better performance than that of conventional methods such as TDR and TFDR.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.623-629
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• 2020

This study examined the airflow field around a gun port on the flight condition of gunfire to verify the aircraft performance and safety effects and gun gas rate, path according to the options of diverter configuration. The gun port diverter not only effectively lowered the heat generated by gunfire but also effectively discharged the gun gas upwards. The path of gun gas can be changed according to its configuration. According to the optional configuration of the rear-gun-port diverter, the flow rate, path, and pressure of the gun gas were analyzed during gunfire. An analysis of the internal velocity distribution and the temperature change of the gun port revealed a rapid decrease in flow rate through the rear diverter according to the option configuration. The forward flow rate showed a similar tendency with little change. This ensures that the gun gas generated during gunfire has a sufficient flow distance from the aircraft surface, regardless of the rear gun port diverter's optional configuration. The flow stagnation of gun gas according to the option configuration of diverter had a great influence on the internal temperature rise of a gun port.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.10-15
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• 2014

For hypersonic aircraft, increase of flight speeds causes heat loads that are from aerodynamic heat and engine heat. The heat loads could lead structural change of aircraft's component and malfunctioning. Endothermic fuels are liquid hydrocarbon fuels which are able to absorb the heat loads by undergoing endothermic reactions, such as thermal and catalytic cracking. In this study, methylcyclohexane was selected as a model endothermic fuel and experiments on endothermic properties were implemented. To improve heat of endothermic reaction, we applied zeolites and confirmed that HZSM-5 was the best catalyst for the catalytic performance. The objective is to investigate catalytic effects for heat sink improvement. The catalyst could be applied to system that use kerosene fuel as endothermic fuel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.441-450
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• 2016

Wireless multi-hop communication is one of the key technologies to operate Unmanned Ground System (UGS) networks efficiently. Conventionally a lot of routing protocol has been developed and studied for multi-hop networks like Mobile Ad-hoc Network (MANET). However, the routing protocol for the unique environment of the UGS requires further studies, since conventional routing protocols cannot be used itself for UGS networks. In this paper, we propose the Betweenness Centrality based Geographic Routing (BCGR) which considers the main function of UGS. BCGR utilizes expanded ego betweenness centrality, mobility and location information error, respectively. We have conducted a simulation study for evaluating the performance of the BCGR using ns-3, and our simulation results show that BCGR outperforms the conventional routing protocols such as AODV and GPSR in terms of end-to-end transmission reliability, throughput and delay.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.167-179
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• 2017

In this paper, a simplified Cubature Kalman Filter (SCKF) is proposed to reduce the computation load of CKF, which is then used as a filter for transfer alignment of shipboard INS. CKF is an approximate Bayesian filter that can be applied to non-linear systems. When an initial estimation error is large, convergence characteristic of the CKF is more stable than that of the Extended Kalman Filter (EKF), and the reliability of the filter operation is more ensured than that of the Unscented Kalman Filter (UKF). However, when a system degree is large, the computation amount of CKF is also increased significantly, becoming a burden on real-time implementation in embedded systems. A simplified CKF is proposed to address this problem. This filter is applied to shipboard inertial navigation system (INS) transfer alignment. In the filter design for transfer alignment, measurement type and measurement update rate should be determined first, and if an application target is a ship, lever-arm problem, flexure of the hull, and asynchronous time problem between Master Inertial Navigation System (MINS) and Slave Inertial Navigation System (SINS) should be taken into consideration. In this paper, a transfer alignment filter based on SCKF is designed by considering these problems, and its performance is validated based on simulations.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.94-101
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• 2017

Tow Prepreg is the intermediate material for filament winding process that has been "pre-impregnated fiber tow" with resin system. As "dry filament winding" process emerges as a reliable alternative to conventional filament winding (called "wet filament winding") process, interest in tow prepreg as a material for dry filament winding is rising as well. In this article, we have reviewed the recent research trends in carbon fiber tow prepreg for high-performance rocket motor cases, fuel tanks for hydrogen vehicles and other high-quality commercial pressure vessels.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.69-74
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• 2016

A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.