• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.119-126
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• 2019

For rockets using cryogenic liquid hydrogen or liquid oxygen, chilling is required to avoid cavitation and surge problems. Chilling is categorized by the initial chilling/filling stage and the low-temperature maintenance stage. In addition, to improve satellite insertion capability, a multi-ignition capability is required and accordingly chilling to prepare for the next ignition during low-gravity coasting is also required. This paper describes the overall aspects of filling and low temperature maintain marinating for the booster and the upper stage engine including chilling for multi-ignition.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.3
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• pp.54-65
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• 2022

We are developing a compact ignition device that can provide a multi-ignition capability for an upper stage methane engine of a two staged small satellite launch vehicle. Firstly, the multi-ignition device is designed and built as an integral part of an additively manufactured mixing head. Secondly, the ignition device requires no separate high-pressure vessels to store ignition propellants as they are branched out from the main feed lines for the mixing head. We performed experiments at various levels, including igniter autonomous tests, thrust chamber ignition and combustion tests on the new compact ignition device which is integrated in the thrust chamber of one-tonf class liquid oxygen/liquid methane engine, and confirmed stable ignition performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.74-86
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• 2021

The composite lattice structure is a structure that supports the required load with the minimum weight and thickness. Composite lattice structure is manufactured by the filament winding process using impregnating high-strength carbon fiber with an epoxy resin. Filament winding process can laminate and manufacture only structurally necessary parts, composite lattice structure can be applied to aircraft fuselages, satellite and launch vehicles, and guided weapons to maximize weight reduction. In this paper, the development and evaluation of the composite lattice structure corresponding to the entire process from design, analysis, fabrication, and evaluation of large-scale cylindrical and conical composites lattice structure were performed. To be applicable to actual projectiles and guided weapons, we developed a cylindrical lattice structure with a diameter of 2,600 mm and a length of 2,000 mm, and a conical lattice structure with an upper diameter of 1,300 mm, a lower diameter of 2,500 mm, and a length of 900 mm. The performance of the developed composite lattice structure was evaluated through a load test.

• Journal of Satellite, Information and Communications
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• v.2 no.1
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• pp.35-40
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• 2007

COSPAS-SARSAT is the search and rescue system for providing a distress alarm and a position identification using an international satellite and ground facilities. Aviators, mariners and land users worldwide are equipped with COSPAS-SARSAT distress beacons, which could help save their in emergency situations anywhere in the world. As the existing COSPAS-SARSAT system is generally operated by LEO(Low-altitude Earth Orbit) Satellite System, the time from the distress beacon to the rescue is more than 1 hour with average and the accuracy of the distress location is about 5 Km. Therefore, in order to overcome this problem, the development for the next generation SAR(search and rescue) system which uses the MEO(middle-altitude Earth Orbit) satellites is going on the Galileo project. EU is developing this project for the full operation capability in 2011, and this project will have SAR payloads and support to the Search and Rescue service-herein called SAR/Galileo. SAR/Galileo will have the performance of a few meter accuracy, within 10 minutes to rescue from reception of distress messages, and Return Link Service(from the SAR operator to the distress emitting beacon), thereby facilitating more efficient rescue operations and helping to reduce the rate of false alerts. As the disaster is larger every year, the ground station, MEOLUT for next generation ASR/Galileo is urgently needed for the lifesaving for the larger disaster, the research for beacon and the ground station such as MEOLUT for introducing the next generation SAR/Galileo in Korea is very timely and is important. This paper presents the procedures and the strategies for the participation, the area to develop reasonably, and the propulsion organization for developing the SAR/Galileo ground system in Korea.

• Korean Journal of Remote Sensing
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• v.38 no.4
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• pp.343-353
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• 2022

An attempt to derive the surface temperature from the Korea Multi-purpose Satellite (KOMPSAT)-3A mid-wave infrared (MWIR) data acquired over the southern California on Nov. 14, 2015 has been made using the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model. Since after the successful launch on March 25, 2015, the KOMPSAT-3A spacecraft and its two payload instruments - the high-resolution multispectral optical sensor and the scanner infrared imaging system (SIIS) - continue to operate properly. SIIS uses the MWIR spectral band of 3.3-5.2 ㎛ for data acquisition. As input data for the realistic simulation of the KOMPSAT-3A SIIS imaging conditions in the MODTRAN model, we used the National Centers for Environmental Prediction (NCEP) atmospheric profiles, the KOMPSAT-3Asensor response function, the solar and line-of-sight geometry, and the University of Wisconsin emissivity database. The land cover type of the study area includes water,sand, and agricultural (vegetated) land located in the southern California. Results of surface temperature showed the reasonable geographical pattern over water, sand, and agricultural land. It is however worthwhile to note that the surface temperature pattern does not resemble the top-of-atmosphere (TOA) radiance counterpart. This is because MWIR TOA radiances consist of both shortwave (0.2-5 ㎛) and longwave (5-50 ㎛) components and the surface temperature depends solely upon the surface emitted radiance of longwave components. We found in our case that the shortwave surface reflection primarily causes the difference of geographical pattern between surface temperature and TOA radiance. Validation of the surface temperature for this study is practically difficult to perform due to the lack of ground truth data. We therefore made simple comparisons with two datasets over Salton Sea: National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) field data and Salton Sea data. The current estimate differs with these datasets by 2.2 K and 1.4 K, respectively, though it seems not possible to quantify factors causing such differences.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.65-70
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• 2005

The KOMPSAT program is carrying out successfully in spite of the short domestic space development history, but there are still many difficulties in Koreanization of most core parts. Because the development of core parts is essential to participate in the advanced nations in space based on the mid-long term national space program, KARI has carried out development of Fill/Drain valve for propellant/pressurant supply of satellite, which has high possibilities to be koreanized, with Hanwha Corp.. This paper summarizes overall processes of development including design, manufacturing and test, and finally 4 sets of modules were successfully made. Also the satisfaction of performance requirements are verified through acceptance tests.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.291-298
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• 2011

The atmospheric infrared sounder (AIRS) sensor loaded on the Aqua satellite observes the global vertical structure of atmosphere and enables verification of the water vapor distribution over the entire area of South Korea. In this study, we performed a comparative analysis of the accuracy of the total precipitable water (TPW) provided as the AIRS level 2 standard retrieval product by Jet Propulsion Laboratory (JPL) over the South Korean area using the global positioning system (GPS) TPW data. The analysis TPW for the period of one year in 2008 showed that the accuracy of the data produced by the combination of the Advanced Microwave Sounding Unit sensor with the AIRS sensor to correct the effect of clouds (AIRS-X) was higher than that of the AIRS IR-only data (AIRS-I). The annual means of the root mean square error with reference to the GPS data were 5.2 kg/$m^2$ and 4.3 kg/$m^2$ for AIRS-I and AIRS-X, respectively. The accuracy of AIRS-X was higher in summer than in winter while measurement values of AIRS-I and AIRS-X were lower than those of GPS TPW to some extent.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1377-1384
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• 2003

An analysis has been performed for active thermal control of the KOMPSAT monopropellant rocket engine assembly, i.e., dual thruster module(DTM). The main efforts of this work have been directed at determining proper heater sizes for propellant valves and catalyst beds necessary to maintain their temperatures within specified temperature ranges under KOMPSAT environment and operational conditions. The TAS incorporated with TRASYS thermal radiation analyzer was used to establish a complete heat transfer model which allows to predict the DTM temperature as a function of time. The thermal analysis has been performed in transient mode to verify the appropriate power for catalyst bed heaters necessary to increase catalyst bed temperature to the required value within a specified period of time. Similar analysis has been executed to validate the heater power for the thermostatically controlled primary and redundant heater circuits used to prevent hydrazine freezing, i.e., single fault. Moreover the effect of the radiative property of thermal control coating of heat shield was examined. Thruster firing condition was also simulated for the heat soakback condition. As a consequence, all thermal analysis results for DTM satisfactorily met the thermal requirements for the KOMPSAT DTM under the worst case average voltage, i.e. 25 volt.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.46-56
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• 2002

In this paper, the feasibility of the attitude control of a spacecraft using pulsed plasma thrusters(PPTs) is studied. The PPT consumes less propellant mass requied for the orbit management or attitude control owing to its high specific impulse characteristics, compared with traditional gas propulsion system. The PPT is expected to be highly adequete for the missions requiring long-duration operations because it has relatively long operation time and easy implementation. The feasibility of the PPT for attitude control of a small satellite system is addressed through realistic missions. The classical PD controller and a fuzzy logic controller are tested, and fuel saving fuzzy logic controller is then proposed for more flexible mission performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.605-611
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• 2010

The geostationary satellite COMS is going to be launched in 2010, and, in the series of test, there are some high-pressure tests concerning the vessel tank filled with helium gas of hundreds atmospheric pressure. In this paper, authors evaluates risk associated with accidental rupture of the test system. Two possible scenarios are considered: 1) the 310-bar helium tank ruptures at the center of the acoustic chamber, and 2) the 116-bar reduced-pressure helium tank ruptures in the test room shielded by bullet-proof glasses. Using the theory of blast wave propagation and computational simulation, the dynamics of wave reflected in a confined space is investigated for highly complex unsteady flow physics.