• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.4-10
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• 2012

Torque characteristics of a 75-tonf turbopump turbine was analyzed using the turbine performance test result. Specific torque of the subject turbine could be expressed as a linear function of corrected rotor speed at a fixed pressure ratio and it has been confirmed by the test result. It also found that corrected rotor speed-specific torque characteristics does not change anymore if the turbine pressure ratio is set bigger than a certain value. Using the turbine torque characteristics and pyro-starter performance test results, rotational speed development behavior of the turbopump was predicted. Prediction revealed that the lap time reaching 50% of turbopump design speed is less than 0.7 second. Effect of the thermal loss between pyro-starter and turbopump was negligible.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.515-519
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• 2011

Structural tests for the mixing head of a 75tonf class thrust chamber were performed to verify structural stability. The mixing head of a thrust chamber is loaded by high pressure with regeneratively cooled fuel and cryogenic liquid oxygen(LOx) as well as it transfers thrust load generated by liquid rocket engine. Therefore structural stability of mixing head is a very important factor to work without any plastic deformation or structural failure. In this study, two mixing heads were manufactured using different welding methods, Tungsten Inert Gas(TIG) welding and Electron Beam Welding(EBW) and evaluated a structural stability. The results of structural tests showed that the mixing head assembled by EBW can withstand the applied design load without any structural failures and be structurally more stable than that of TIG welding.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.125-130
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• 2007

Firing tests have been performed for a 30 tonf-class full-scale regeneratively cooled combustion chamber. It was the first model which has welded construction of the injection head and the combustion chamber. A number of firing tests have been performed to evaluate combustion efficiency, regenerative cooling performance and durability of the combustor. This paper describes the results of firing tests performed at the design and off-design conditions which correspond to the chamber pressure of 60 bar, 68 bar respectively and the O/F ratio of 2.5 and 2.8 respectively. The data at each test condition have provided successful results in terms of combustion performance, combustion stability and durability. The tests are considered to be quite meaningful in the sense that the technologies for kerosene regeneratively cooled combustion chamber are successfully proven.

• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.45-52
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• 2018

This paper deals with the analysis of the inner-loop algorithm of the Pixhawk which is a representative multi-copter open source. The algorithm is based on flight control-law structure. The inner-loop algorithm of the Pixhawk can be divided into a position controller and an attitude controller. The position controller generates the attitude of the multi-copter to move to the destination The position controller also generates the demand force and moment acting on each actuator. We confirm that the position controller saturates the desired acceleration and speed by using a proper relational expression. The expression can be used in order to prevent the sudden change in the attitude of a multi-copter.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.159-162
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• 2008

In this study, various cycles of liquid rocket engines were surveyed and specifically gas generator after burning cycle was investigated for upper stage motors. The engines for the upper stage can be categorized into three group based on the cycles and propellants at the diagram. Kerosene engines which adapt the gas generator after burning cycle and are located in the region II, are characterized for high combustion pressure and complexity. This cycle usually needs more than two pumps to use the turbine power efficiently. The fuel line can be divided into the gas generator line and the combustor line, and only the gas generator line is need to be pressured more because the combustion pressure in the gas generator is much higher than that of the combustor. Basically, all the oxidizer goes into the gas generator and than to the combustor, thus the auxiliary LOx pump is not critically necessary. However, for the various reasons, the LOx line requires a booster pump. A gas generator after burning cycle engines produces relatively high specific impuls than that of the open cycle engines. Thus it is suitable for upper stages of launch vehicles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.69-73
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• 2009

Combustion test results of 1/2.5-scale thrust chamber for 75tonf-class liquid rocket engine were described. The thrust chamber has chamber pressure of 60 bar, propellant mass flow rate of 89 kg/s, and nozzle expansion ratio of 12. The combustion tests were conducted to verify the combustion performance, the regenerative cooling performance and the durability of thrust chamber at design point condition, and then were performed to confirm the operation and the combustion performance at low combustion pressure condition. All the tests had been successfully executed without the damage of the hardware. These test results present a possibility of hot firing test at low combustion pressure condition, and can be used as fundamental data to predict the combustion performance at design point condition for 75 tonf thrust chamber.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.897-900
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• 2007

This paper presents a study on the DSP controller and IGBT inverter driver design for the power-by-wire(PBW) system using BLDC servo motor. This BLDC servo motor system was realized with DSP(Digital Signal Processor) and IGBT inveter module. The PBW system needs speed control of servo motor for linear thrust action. This paper implements a servo controller with vector control and min-max PWM technique. As CPU of controller, TMS320F2812 DSP was adopted because it has PWM(Pulse Width Modulation) waveform generator, A/D(Analog to Digital) converter, SPI( Serial Peripheral Interface) port and many input/output port etc.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.258-261
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• 2003

The optimal design and combustion analysis of the gas generator for Liquid Rocket Engine (LRE) were performed. A fuel-rich gas generator in open cycle turbopump system was designed for 101on1 in thrust with RP-1/LOx combination. The optimal design was done for maximizing specific impulse of main combustion chamber with constraints of combustion temperature and power matching in turbopump system. Results of optimal design show the dimension of length, diameter, and contraction ratio of gas generator. The configuration of the gas generator and the condition for performance which can maximize the objective function were determined and found to meet the design constraints. Also, the combustion analysis was conducted to evaluate the performance of designed chamber and injector of gas generator. And the effect of the turbulence ring was investigated on the mixing enhancement in the chamber.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1124-1131
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• 2015

This paper describes a 5-dof ground testbed which emulates micro-gravity environment for developing Rendezvous/docking algorithm of a nano-satellite. The testbed consists of two parts, the low part which eliminates friction force with ground and the upper part which has 3-dof rotational motion with respect to the low part. For Vison-based autonomous navigation algorithm, we use camera, LIDAR and AHRS as sensors and eight cold gas thrusters and three axis directional reaction wheels as actuators. All system software are implemented with C++ based on on-board computer and Linux OS.

• Journal of Astronomy and Space Sciences
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• v.24 no.2
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• pp.145-154
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• 2007

Antenna pointing analysis for a geostationary satellite has been performed for using the NORAD Two-Line-Elements (TLE) converted from osculating Keplerian orbital elements. In order to check the possibility of the reception of the satellite signal, the antenna offset angles have been derived for the Communications, Ocean, and Meteorological Satellite (COMS) which carries out weekly East-West and North-South station-keeping maneuvers and twice a day thruster assisted momentum dumping. Throughout the analysis, it is shown that the use of converted NORAD TLE simplifies the antenna pointing related interfaces in satellite mission control system. For a highly eccentric transfer orbit cases, further analysis presents that the converted NORAD TLE from near apogee gives more favorable results.