• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.50-60
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• 2015

A propulsion system of a satellite provides a necessary thrust to reach to the final orbit after a separation from a launch vehicle. Also, it supplies pulse moments to maintain the satellite in a mission orbit and for its attitude controls during a mission life time. The present study investigates the development trend of bipropellant rocket engines for an orbit transfer and an attitude control of a satellite using monomethylhydrazine and hydrazine for fuel and dinitrogen tetroxide for oxidizer to derive fundamental specifications which are necessary for domestic development researches. Also, their major performance characteristics are summarized.

• Journal of Astronomy and Space Sciences
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• v.19 no.3
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• pp.207-214
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• 2002

One of the way to derive design parameters of the fuel feeding system in satellite propulsion system is to analyze unsteady flow of liquid propellant (hydrazine). During steady thruster firing the flow rate is constant: if a thruster valve is abruptly shut down among a set of thrusters, pressure spikes much higher than the initial tank pressure occur. This renders the fuel flow unsteady, and the fluid pressure and flow rate to oscillate. If the pressure spikes are high enough, there are possibilities that propellant explosively decomposes, thruster valves we damaged, and adiabatic detonation of the hydrazine propellant is potentially incurred. Reflected shockwaves could also affect the calibration and operation of the pressure transducers. These necessitate the analysis of unsteady flow in the propulsion system design, and pressure behavior inside the propellant line obtained through some governing parameter variation is presented in this work.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.24-27
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• 2016

In this study, a 1kW Solid Oxide Fuel Cell(SOFC) test system was developed. A SOFC is the most promising power system to provide the higher efficient(over 50%) for house application area(1~10kW). To develop the optimized test system, the temperature control module that controls the preprocess and reaction condition, the flow control module that controls of the mass of reactants, and the electric loader that tests the discharge performance condition, etc. The temperature control module was designed to provide the high control resolution(under $1^{\circ}C$ at $750^{\circ}C$ of operating temperature) using K-type thermal couple. The flow control module was designed control blower and heater precisely using the phase control method. And the electric loader is designed that provide CV, CC, CR discharge mode and minimized the operating error adopting the independent DC-DC converter on analog input and output module. The performance of the developed SOFC test system showed that the accuracy of stack voltage was 0.15% at 80V and stack current was 0.1% at 100A.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.157-164
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• 2007

Launch Interface Ring roles as connection department of satellite and launcher for to deliver all structure loads that occur from the satellite, and one of the most intensive load received parts. Especially COMS, the first Korean developing GEO satellite, needs Launch Interface Ring with Tank Support Beam because of dissymmetry fuel tanks. The purpose of this study is the suitable form decision of Launch Interface Ring at preliminary design of COMS. In this study, launch mass and design constraints are investigated. Moreover, optimization algorithm and simplification technique are used. At the beginning of this study, three types of launch interface ring were presented and finally model 3 was the lightest design for resistance of launch environment. Nevertheless, model 1 can be suggested for application to COMS because of the satellite gravity center control and ease of fabrication.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.112-122
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• 1995

We assume that the KOREASAT fails the entry of the geostationary orbit due to the error at the apogee kick motor firing. A simulation is done for the satellite that has a geosynochronous orbit with a non-zero degree inclination angle due to the failure at the apogee kick motor firing caused by the unbalance of the fuel storage and the spin of the thrust vector, etc. We analyzed the evolution of the orbit using the perturbation theory and calculated the changes of the eccentricity and the inclination. WHen a communication satellite has the figure eight trajectory, the beam point also traces the satellite. In this paper, We develope an algorithm to attack the above problem by stabilizing the beam point using the adjustment of the roll angle of the satellite. The spin action on the polarization plane that occurs when a satellite passes the ascending node and descending node affects the efficiency of the communication a lot, so we did another simulation for the better yaw angle adjustment for the KOREASAT to reduce the spin actino on the polarization plane.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1059-1068
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• 2017

Space exploration spacecraft carry large amounts of liquid fuel, often more than half. In such cases, the liquid fuel sloshing must be considered in the design of the spacecraft since the sloshing can affects the stability of the spacecraft. In this paper, we present the results of analyzing the sloshing of fuel and the dynamic behavior of the spacecraft. For the purpose, a model in which the maneuvering of the spacecraft causes the sloshing and a model in which the reaction force and moment due to the sloshing are transmitted to the spacecraft are developed. The dynamical behavior of the spacecraft are analyzed using a simulation program coded by Modelica.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.81-88
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• 2005

This paper analyzes the fuel consumption for the momentum dumping of the COMS which has a single solar array system. First, numerical analyses are conducted to find an optimal momentum dumping time considering the COMS configuration. It is assumed that the momentum dumping is conducted once a day and at a fixed time of a day. Secondly, in an effort to reduce the momentum dumping fuel consumption, this paper proposes a new approach which combines the momentum dumping and the ordinary north/south stationkeeping. Finally, to evaluate the proposed technique, the stationkeeping simulations are conducted and analyzed.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.1-6
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• 2015

Due to the rapid increase in air traffic worldwide, ICAO has replaced the existing navigation equipment with equipment based on satellite navigation. As a part of that work, ICAO was planning to replace conventional takeoff and landing service using ILS with GBAS. Unlike ILS, GBAS which uses precision approach service inducing aircraft to airport and satellite based augmentation system providing precise position information service surrounding airport is capable of providing a required performance by only a system, regardless of the number of systems, and has an advantage that it is possible curved approach. In this paper, fuel reduction of ILS approach procedures and GBAS curved approach procedures is estimated and determined by flight test in Taean Airport.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.48-53
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• 2005

This work discusses the numerical analysis, the design and experimental test of the SMA actuator along with its capabilities and limitations. Convective heating and cooling using water actuate the SMA(Shape memory alloy) element of the actuator. The fuel such as propane, having a high energy density, is used as the energy source for the SMA actuator in order to increase power and energy density of the system, and thus in order to obviate the need for electrical power supplies such as batteries. The system is composed of a pump, valves, bellows, a heater(burner), control unit and a displacement amplification device. The experimental test of the SMA actuator system results in 150 MPa stress(force : 1560 N) with $3\%$ strain and 0.5 Hz. actuation frequency. The actuation frequency is compared with the prediction obtained from numerical analysis. For the designed SMA actuator system, the results of numerical analysis were utilized in determining design parameters and operating conditions.

• Proceedings of the KSRS Conference
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• v.1
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• pp.263-266
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• 2006

Now, on the developing COMS(Communication, Ocean and Meteorological Satellite) has solar panel on the South panel only. Therefore, the wheel off-loading has to be performed periodically to reduce a induced momentum energy by a asymmetric solar panel. One of two East/West station keeping maneuver to correct simultaneously longitude and eccentricity, orbit corrections may be performed during one of the two wheel off-loading manoeuvres per day to get enough observation time for meteorological and ocean sensor. In this paper, we applied a linearized orbit maneuver equation to acquire maneuver time and delta-V. Nonlinear simulation for the station keeping is performed and compared with general station keeping strategy for fuel reduction.