• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.54-61
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• 2004

Miniaturization of subsystems including propulsion systems is recent trends in spacecraft technology. Small space vehicle propulsion is not only a technological challenge of a scaling system down, but also a combination of fundamental flow/combustion constraints. In this paper, physical constraints of micronozzle for cold gas micro-thruster are reviewed and discussed. Method to measure small thrust are also described.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.300-309
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• 2017

A spacecraft obtains a reaction momentum required for an orbit correction and an attitude control by exhausting a combustion gas through a small thruster in space. If the exhaust plume collides with spacecraft surfaces, it is very important to predict the exhaust plume behavior of the thruster when designing a satellite, because a generated disturbance force/torque, a heat load and a surface contamination can yield a life shortening and a reduction of the spacecraft function. The purpose of the present study is to ensure the core technology required for the spacecraft design by analyzing numerically the exhaust gas behavior of the 10 N class bipropellant thruster for an attitude control of the spacecraft. To do this, calculation results of chemical equilibrium reaction between a MMH for fuel and a NTO for oxidizer, and continuum region of the nozzle inside are implemented as inlet conditions of the DSMC method for the exhaust plume analysis. From these results, it is possible to predict a nonequilibrium expansion such as a species separation and a backflow in the vicinity of the bipropellant thruster nozzle.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.121-127
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• 2010

Neutral gas in a Hall-effect thruster in a small satellite is simulated using a molecular dynamics code. Investigated are neutral density, pressure, axial average velocity, and temperature for the variation of diffusive reflection ratio, initial gas temperature, and channel length. Expected through this research are improving of discharge simulation through the neutral simulation and understanding of real system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.84-89
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• 2011

A Xenon Feed System (XFS) has been developed for hall-effect thruster to small satellite space-propulsion system applications. The XFS delivers low pressure gas to the Anode and Cathode of thruster head unit from a xenon storage tank. Accurate throttling of the propellant mass flow rate is independently required for each channel of the thruster head unit. The mass flow rate to each channel is controlled using the accumulator tank pressure regulation through a micron orifice and isolation valve. This paper discusses the Xenon Feed System design including the component selections, performance estimation and functional test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.697-703
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• 2017

A teflon ionization modeling has been conducted to predict the performance of a PPT(Pulsed Plasma Thruster). One dimensional unsteady circuit model and Teflon ablation model were implemented. The Saha equation was adapted to predict the ionization of Carbon and Fluorine gas. The lumped circuit model including a resistance and a inductance model of a plasma was adapted to predict the magnitude of a discharge current. Numerical simulation results had good agreements with pervious research. The degree of current change according to PPT operating voltage was examined.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.188-194
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• 2006

This paper deals with the development of Engineering Model for the TCU( Thruster Control Unit) and simulation system of the reaction control system using cold gas. TCU communicates with TLM(Telemetry) and ground control console so that it transmits monitoring data of pressures and temperatures for reaction control system. The cpu/communication board performs MIL-STD-1553B communication, RS-422 communication, data input/output processing and program loading to EEPROM. We applied Intel 80386DX Microprocessor, 256Kbytes EEPROM and 256Kbytes SRAM for program storage and execution. Also, we developed the direct access interface circuit to EEPROM and simulation system for TCU.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.249-252
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• 2006

We conducted the experiment to analyze characteristics of micro-nozzle using different cold gas under two different nozzle expansion ratios in low vacuum condition. We measured thrust and chamber pressure and mass flow rate under low vacuum condition, and then compared them with those in ambient pressure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.540-543
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• 2011

This work is devoted to an experimental investigation on conceptual design of dual consecutive stage micro plasma thruster (${\mu}PT$). Optimization study on the thruster configuration has been performed for various electrode gap distances from 1 mm to 2 mm and the hole diameter from 0.3 mm to 2 mm depending on desired operating conditions and corresponding nozzle design requirement. The operation of ${\mu}PT$ at low pressure from $10^{-1}$ Torr to $10^{-4}$ Torr and at various argon flow rates ranging from 5 sccm to 300 sccm has been studied to understand the physic of plasma and the gas dynamics in details. The specific impulse can reach up to 3000-4000 seconds at low power consumptions from 1 to 5 W. Image of exhaust plume from ${\mu}PT$ will be provided and electrical characteristics is also mentioned in this paper.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.122-126
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• 2009

KSLV(Korea Space Launch Vehicle)-I is designed as a launch vehicle to enter a 100 kg-class satellite to the LEO(Low-Earth Orbit). Attitude angles of the upper-stage, including roll, pitch and yaw are controlled by cold gas thruster system using nitrogen gas. To verify the flow rate of the gas charging system and to prepare a nitrogen gas charging scenario, the development of a gas charging simulator for RCS(Reaction Control System) is required. This paper describes the orifice design, development, and test of the gas charging simulator for RCS of KSLV-I.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.649-657
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• 2019

Hydrazine, which is used as a representative monopropellant, is an extremely poisonous substance and has a disadvantage that it is harmful to the human body and is very difficult to handle. In recent years, research on the development of non-toxic and environmentally friendly propellants has attracted much attention. Ammonium dinitramide(ADN) based propellant developed by Swedish Space Corporation has superior performance to hydrazine and has been commercialized through performance verification in space environment. On the other hand, the exhaust gas from a thruster nozzle collides with a satellite while it is spreading in the vacuum space, thermal load and surface contamination may occur and may reduce the performance and lifetime of the satellite. However, a study on the effect of the exhaust gas of the green propellant thruster on the satellite has not been conducted in earnest yet. Therefore, the exhaust gas behavior in space was analyzed in this study for the ADN based green monopropellant using Navier-Stokes equations and the DSMC method. As a result, it can be expected to be used as design validation data in the development of satellite when using the ADN based green monopropellant.