• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.4
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• pp.37-43
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• 2011

Lunar exploration program has been prepared with the aim of launch in the 2020's. As part of it, a lunar lander demonstrator has been developed which is the model for verifying all the system, such as structure, propulsion and control system before launch to deep space. After verifying all the system, the demonstrator will be evaluated by flight test. This paper deals with path tracking controller based on thrusters for the demonstrator. For this, first we derive equations of motion according to the allocation of thrusters and design the path tracking controller. The signal generated from the controller is continuous so PWPF(Pulse-Width Pulse-Frequency) modulator is adopted for generating on/off signal. Finally MATLAB simulation is performed for evaluating the path tracking ability and the final landing velocity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.254-257
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• 2011

Two types of thrusters(Descent Control Thruster (DCT) for reducing landing speed and Attitude Control Thruster (ACT) for attitude control) are mounted on the propulsion system of Ground test model lunar lander. In this paper, plume impingement effect and ground effect between DCT Modules are analyzed using numerical method when the impact occurred close to the ground.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.984-997
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• 2015

Chang'e-3 consisting of a lunar lander and exploration rover was launched on December 1, 2013 aboard a Long March 3B rocket flying from Xichang space launch center. Chang'e-3 was inserted into the lunar orbit after about a 5-day transit to the Moon and landed on the targeted landing site after orbiting around the Moon for 8 days. The successful landing of the Chang'e-3 gives a lot of help to analyze the future needs of the subsystem technologies and to figure out the trajectory from launch to lunar landing as well as operation sequences in the development of Korean lunar exploration is scheduled. Therefore, the configuration and analysis of overall mission of Chang'e-3 is performed based on the public information from the press and website. As a result, overall mission trajectory is reconstructed by solving boundary condition and then estimating control variable. Visibility status and eclipse status also analyzes so communication and power charge condition is as good as to operate lunar lander. Mass budget of the lander is derived using ${\Delta}V$ according to specific impulse.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.26-34
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• 2019

In this paper, a coarse lunar soil model is developed using discrete element method and its computed physical properties are compared with those of the actual lunar soil for its validation. The surface of the actual moon consists of numerous craters and rocks of various sizes, and it is covered with fine dry soil which seriously affects the landing stability of the lunar lander. Therefore, in consideration of the environment of the lunar regolith, the lunar soil is realized using discrete element method. To validate the coarse model of lunar soil, the simulations of the indentation test and the direct shear test are performed to check the physical properties(indentation depth, cohesion stress, internal friction angle). To examine the performance of the proposed model, the drop simulation of finite element model of single-leg landing gear is performed on proposed soil models with different particle diameters. The impact load delivered to the strut of the lander is compared to test results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.208-216
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• 2014

Ground station in lunar mission is responsible to receive telemetry signal including sensor data from lunar orbiter and/or lander. At preliminary stage of developing this ground station, receiving performance such as antenna size and noise temperature should be designed on the basis of link budget analysis. When the antenna of ground station is pointing to the moon to communicate with lunar orbiter and/or lander, noise level is supposed to be increasing due to the lunar flux density. It means that the moon is working as a noise source to degrade receiving performance when antenna is pointing to the moon. Antenna noise temperature contributed by the moon was firstly calculated and secondary validated by using test configuration in this paper. Consequently, it was shown that antenna noise temperature caused by the moon was quietly matched with measured one and G/T degradation of receiving system in lunar mission can be calculated depending on antenna size and frequency.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.124-132
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• 2018

In this paper, landing stability evaluation of lunar lander considering various landing conditions was performed. The status of landing stability of the lunar lander is classified into stable landing, conditionally stable landing due to sliding and unstable landing due to tip-over. In particular, the quasi-static tip-over equation was rearranged considering the phenomena of lowering the center of gravity and extension of foot-pad interval of the landing gear. These results were compared by finite element model analysis results using a commercial software ABAQUS and its validity and accuracy were verified. The verified finite element model was used for examining the tendency of various environmental variables such as landing conditions, friction coefficient, lateral speed and slope of ground.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.314-320
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• 2011

In this work, optimization of two-stage shock absorption system for lunar lander has been carried out. Because of complexity of impact phenomena of shock absorption system, a 1-D constitutive model is proposed to describe the behavior of shock absorption system. Quadratic polynomial regression meta-model is constructed by using a commercial software ABAQUS with the proposed 1-D constitutive model, and sequential approximate optimization of two-stage shock absorption system has been carried out along with the constructed meta-model. Through the optimization, it is verified that landing impact force on lunar lander can be considerably reduced by changing the cell size and foil thickness of honeycomb structure in two-stage shock absorption system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.402-409
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• 2018

In this paper, we propose a lunar landing scenario of a robotic lunar landing mission and implements an optimal landing trajectory at the powered descent phase based on the proposed scenario. The change of attitude of the lunar lander in the power descent phase affects not only the amount of fuel used but also sensor operation of image based navigation. Therefore, the attitude angular velocity is included in the cost function of the optimal control problem to minimize the unnecessary attitude change when the optimal landing trajectory generates at powered descent phase of the lunar landing. The influence of the change of attitude angular velocity on the optimal landing trajectory are analyzed by adjusting the weight of the attitude angular velocity. Based on the results, we suggest the proper weight to generate the optimal landing trajectory in order to minimize the influence of the attitude angular velocity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.654-657
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• 2011

For the successful development of korean exploraton program, KARI started development of ground test model for lunar lander from last year. In order to secure core technology for space propulsion system, Koreanization of propellant tank is proceeding and it will be used for final assembly and test for ground test model. In this paper, the development result of titanum tank shell and verification test result was presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.42-45
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• 2012

As a basic research for the development of Korean lunar lander, propulsion system development for ground test is in progress. Design target is 220 N in ground thrust at 130 g/s flow rate, 200 psi chamber pressure. For the performance improvement, two type injector and catalyst bed was designed. For ground test, thrust measurement system using LM guide was developed and test was performed. The result shows 214.1 N thrust in atmosphere condition at 126.6 g/s flow rate.