• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.389-396
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• 2002

In XXI century it is necessary to expect the recommencement and development of activities on mastering the Moon. In the long term it is construction of manned lunar bases with industrial, astrophysical, procuring, repair equipment and services. Interplanetary flights from the Moon demand smaller power expenditures, than from the Earth, therefore it is favourable to use its surface for the construction of space-vehicle launching sites. Flights of devices in libration points in the system 'Earth - Moon' are considered. Experience of engineering system creation for the Moon displays the great complexity in provision of serviceability and reliability of friction units. Open friction units should operate under following conditions on the Moon: pressure of environment (vacuum) $p\;>10\;^{-10}$ Pa; wide range of temperature change $+150^{\circ}C\;...170^{\circ}C$; high evaporability of lubricants; influence of temperature gradients and warping of constructions; sublimation of elements of constructional materials; irradiation of different physical nature; effect of micrometeorites; reduced gravitation; influence of abrasive particles of lunar ground; requirements on minimization of size and weight characteristics of a construction (high tension); undesirability (impossibility) of application of liquid and plastic lubricants; vibration, shock, acoustic loadings during start and landings to the Earth; difficulties in repair-regenerative operations in conditions of the Moon etc. Adhesive interaction of conjugated surfaces is the principal reason of possible failures of rubbed units on the Moon. In the research of the Moon automatic interplanetary stations of 'Luna' (USSR), 'Surveyer', 'Apollo' (USA) series were used. Stations executed functions of flying, landing, artificial satellites of the Moon, moon-rovers and manned spacecrafts such as 'Apollo'. The experimental- theoretical researches carried out in the sixtieth years on tribology for conditions of the Moon appeared to be rather useful to engineering of an outer space exploration and the decision of complex problems for the friction units operating in extreme conditions on the Earth. For the creation of highly loaded friction units for the long service life on the Moon it is required not only to use accumulated experience and designed technologies, but also to carry out wide scientific research.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.741-757
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• 2016

Over 60 years has passed since mankinds started space exploration beyond the Earth with lunar explorer Luna 1 launched by Soviet Union. Unprecedently remarkable outcomes have been obtained by sending unmanned spacecrafts to most planets in the solar system and having the lander landed on the approaching comet toward the Earth even though any evidence of life presence has not been discovered yet. Only moon is an natural object beyond the earth on which human beings landed. Many countries are planning to send humans to the moon or mars to build colonies and to survive with substantiality. Korean lunar exploration program has officially started as of 2016 after its plan including lunar exploration has been specified in the series of National Space Promotion Plan since Korea initiated space development in early 1990s. In this paper, the plan for Korean space exploration is summarized with reviewing overseas space exploration program status and trends.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.724-730
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• 2017

SpaceWire invented for spacecrafts has Time-Code defined for time synchronization over SpaceWire network. A Time-Code suffers transmission delay of 14[bit-period] and jitter up to 10[bit-period] whenever it passes through a SpaceWire link, which is the primary cause of time synchronization error. This work presents a simple method to improve the time synchronization which uses two extended Time-Codes. Nodes on a SpaceWire network can find how much delay and jitter a received Time-Code has suffered while it passes through the network, and they can correct time synchronization error with this information. The proposed method was validated in a simulation environment developed based on OMNeT++. The simulation result showed that time synchronization error less than a few bit-periods can be achieved. The proposed method is cost effective and suitable for small-scale SpaceWire network systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.164-171
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• 2013

Since plenty of spacecrafts were launched in space after 1957, the number of space debris has been increased. According to the JSpOC, the number of space debris which diameter is bigger than 10 cm are more than 22,000. Recently there were two critical events. Which one is that China shot down their satellite using missile and the other is that two satellite, Iridium and Cosmos 2251, collied. Space environment in low-earth orbit has been severe. JSpOC analyzes the collision risk between 15,000 space debris and all operation satellites and then they send CSM to the satellite operator to utilize its orbital information if collision risk might be occurred. This paper analyzes the CSM orbit data by comparing with KOMPSAT-2 precise orbit data and shows conjunction assessment results.

• Current Industrial and Technological Trends in Aerospace
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• v.6 no.1
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• pp.44-55
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• 2008

Catalyzed by the recent development of space technology, various kinds of spacecrafts were launched and utilized with purposes in many developed countries. In case of emergency such as natural disasters, proper satellite images are required in order to help to mitigate and assess the effects of disasters on human life and property. Since there are limitations for a nation to single-handedly operate a satellite and fulfill complete demands, a development need of international cooperation organization to share satellite images among the member countries has risen. In this paper, preestablished four international organizations' background, objectives, and operating system, and their principal characteristics were analyzed and compared. Especially, the paper has focused on the analysis of on-going operating procedures and its cases for International Charter, UN SPIDER's development of local supporting network to support NFP, establishment of Web-GIS by Sentinel Asia under the goal of 'Digital Asia', and the utilization of GEO that is widely applied in natural disaster fields.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.347-350
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• 2004

A space radiation analysis has been used to evaluate an ability of electronic equipment boxes or spacecrafts to endure various radiation effects, so it helps design thicknesses of structure and allocate components to meet the radiation requirements. A comparison study of space radiation dose analysis programs SPENVIS Sectoring Tool (SST) and SIGMA II is conducted through some structure cases, simple sphere shell, box and representative satellite configurations. The results and a discussion of comparison will be given. A general comparison will be shown for understanding those programs. The both programs use the same strategy, solid angle sectoring with ray-tracing method to produce an approximate dose at points in representative simple and complex models of spacecraft structures. Also the particle environment data corresponding to mission specification and radiation transport data are used as input data. But there are distinctions between them. The specification of geometry model and its input scheme, the assignment of dose point and the numbers, the prerequisite programs and ways of representing results will be discussed. SST is a web-based interactive program for sectoring analysis of complex geometries. It may be useful for a preliminary dose assessment with user-friendly interfaces and a package approach. SIGMA II is able to obtain from RSICC (Radiation Safety Information Computational Center) as a FOR-TRAN 77 source code. It may be suitable for either parametric preliminary design or detailed final design, e.g. a manned flight or radiation-sensitive component configuration design. It needs some debugs, recompiling and a tedious work to make geometrical quadric surfaces for actual spacecraft configuration, and has poor documentation. It is recommend to vist RSICC homepage and GEANT4/SSAT homepage.

• Current Industrial and Technological Trends in Aerospace
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• v.9 no.1
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• pp.55-63
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• 2011

Space debris is the collection of objects in orbit around Earth that were created by humans but no longer serve any useful purpose. Since plenty of spacecrafts were launched in space after 1957, the number of space debris has been increased. According to USSTRATCOM, the number of space debris which are bigger than 10cm is more than 15,000. Recently two critical events were occurred. Which one was that China shot down their satellite using missile and the other was that t o satellite, Iridium 33 and Cosmos 2251, collided in space. Space debris environment in which KOMPSAT-2 is operating has been severe. This paper presents the status of space debris and international activity, and the comparison of conjunction assessment process between Korea Aerospace Research Institute and abroad satellite operation center.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1017-1026
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• 2009

The solar cell system operates by facing the sun-light. Minor cracks, static discharge, and thermal shock that can happen during production/testing phase can lead to degradation in performance during operation, since solar cells are exposed to extreme thermal/mechanical environment in space. In order to detect small cracks and internal damages in the solar cells due to thermal shocks, which are the core units of a solar cell system, expensive equipment, complicated test process, and much time are required. Therefore, a qualitative method for easily and quickly testing the 'health' of solar cell functionality is required. This dissertation describes a theoretical and technical grounds for quickly and easily evaluating the health of solar cells using electroluminescence effect of Gallium-Arsenide solar cells that are most widely used by spacecrafts in recent years. Also described in the dissertation is the technical issues and constraining factors for applying the proposed method to actual space-rated solar cell systems.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.4
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• pp.46-58
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• 2010

Hydrogen peroxide(HP) and liquid methane have deserved renewed considerations as green propellants in recent years, because main design concerns in the development of the new generation propulsion system for spacecrafts are concentrated on low operation cost and environmental cleanness. Although HP has a long history of application to aerospace propulsion systems due to high density, mono-propellant characteristics and low toxicity, it had been replaced by hydrazine and liquid oxygen due to extreme performance requirement during the cold war. But HP has received a renewed interest due to its increased stability and many researches have been conducted to develop high performance LREs(Liquid Rocket Engines) using HP. Liquid methane has also received a new interest in rocket propulsion system for the future space exploration according to its possibility of ISRU(In-Situ Resource Utilization).

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.441-450
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• 2005

The organic material is one of the most popular material for the satellites and the spacecrafts in order to perform the thermal management, and to protect direct exposure from the space environment. The present paper observes material property changes of organic material under the space environment by using ground facilities. One of the representative organic thermal management material of satellites, 2 mil ITO(Indium Tin Oxide) coated aluminized KAPTON was selected for experiments. In order to investigate the single parametric effect of protons in space environment, MC-50 cyclotron system in KIRAMS(Korea Institute of Radiological and Medical Science) was utilized for the ion beam irradiation of protons and ion beam dose was set to the Very Large August 1972 EVENT model, the highest protons occurrence near the earth orbit in history. The energy of ion beam is fixed to 30MeV(mesa electron volt), observed average energy, and the equivalent irradiance time conditions were set to 1-year, 3-year, 5-year and 10-year exposure in space. The procedure of analyses includes the measurement of the ultimate tensile strength for the assessment of quantitative degradation in material properties, and the imaging analyses of crystalline transformation and damages on the exposed surface by FE-SEM(Field Emission Scanning Electron Spectroscopy) etc.