• Journal of Astronomy and Space Sciences
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• v.41 no.2
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• pp.79-85
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• 2024

Nowadays, the trend in lunar exploration missions is shifting from prospecting lunar surface to utilizing in-situ resources and establishing sustainable bridgehead. In the past, experiments were mainly focused on rover maneuvers and equipment operations. But the current shift in trend requires more complex experiments that includes preparations for resource extraction, space construction and even space agriculture. To achieve that, the experiment requires a sophisticated simulation of the lunar environment, but we are not yet prepared for this. Particularly, in the case of lunar regolith simulants, precise physical and chemical composition with a rapid development speed rate that allows different terrains to be simulated is required. However, existing lunar regolith simulants, designed for 20th-century exploration paradigms, are not sufficient to meet the requirements of modern space exploration. In order to prepare for the latest trends in space exploration, it is necessary to innovate the methodology for producing simulants. In this study, the basic framework for lunar regolith simulant development was established to realize this goal. The framework not only has a sample database and a database of potential simulation target compositions, but also has a built-in function to automatically calculate the optimal material mixing ratio through the particle swarm optimization algorithm to reproduce the target simulation, enabling fast and accurate simulant development. Using this framework, we anticipate a more agile response to the evolving needs toward simulants for space exploration.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.62.1-62.1
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• 2015

Polarization of the light reflected off the Moon provides information on the size and composition of the particles in the lunar regolith. The mean particle size of the regolith can be estimated from the combination of the albedo and degree of polarization, while the color ratio of the parallel-component polarization (CP) has been suggested to be related to the amount of nanophase metallic iron (npFe^0) inside the regolith particles. Both the mean size and npFe^0 abundance of the particles have been used as maturity indicators of the regolith since sustained impacts of high energy particles and micro-meteoroids cause comminution of particles and production of npFe^0. Based on our multispectral polarimetric observations of the whole near side of the Moon in the U, B, V, R, and I bands, we compare the maps of the mean particle size, CP, and the optical maturity (OM). We find that the mean particle size map is sensitive to the most immature (~0.1 Gyr) soil, the OP map to the intermediate immaturity (a few 0.1 Gyr) soil, and the CP map to the least immature (~1 Gyr) soil.

• Advances in Computational Design
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• v.4 no.2
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• pp.141-153
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• 2019

This research is comprised of virtually simulating behavior while experiencing low gravity effects in advance of real world testing in low gravity aboard Zero Gravity Corporation's (Zero-G) research aircraft (727-200F). The experiment simulated a drill rig penetrating a regolith simulant. Regolith is a layer of loose, heterogeneous superficial deposits covering solid rock on surfaces of the Earth' moon, asteroids and Mars. The behavior and propagation of space debris when drilled in low gravity was tested through simulations and visualization in a leading dynamic simulation software as well as discrete element modeling software and in preparation for comparing to real world results from flying the experiment aboard Zero-G. The study of outer space regolith could lead to deeper scientific knowledge of extra-terrestrial surfaces, which could lead us to breakthroughs with respect to space mining or in-situ resource utilization (ISRU). These studies aimed to test and evaluate the drilling process in low to zero gravity environments and to determine static stress analysis on the drill when tested in low gravity environments. These tests and simulations were conducted by a team from Texas A&M University's Department of Construction Science, the United States Air Force Academy's Department of Astronautical Engineering, and Crow Industries

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.45.3-46
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• 2015

Space weathering agents such as micrometeoroids and solar wind particles continuously age the uppermost regolith of the lunar surface by comminuting as well as darkening and reddening. Among several maturity indices, we investigate median grain size () and optical maturity (OMAT) of the crater rim walls. Crater rim wall is the most immature place among the impact crater features because the vertical mixing process by mass-movement can enhance the gardening of regolith and the supply of immature materials in the deeper layer to the surface. More than 140 simple and complex craters were considered. Both and OMAT values of the inner rim wall initially increase as the crater size increases until ~10-20 km, then decrease. This transition crater size happens to correspond to the transition diameter from simple to complex craters. For larger craters, i.e., complex craters, it is clear that the inner rim wall of the craters formed in recent eras tend to remain fresh and become mature along with time. For the simple crater case, smaller craters are more mature, which is opposite to the case of complex craters. This is thought to be because smaller craters become flattened more quickly, thus have smaller vertical mixing in the regolith due to mass-movement. We will also discuss on the maturity indices of the crater rim walls at high latitudes as a function of the position angle to see the latitude dependence of the space weathering process.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.93.2-93.2
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• 2013

Polarization of the light scattered by the lunar surface contains information on the mean particle size of the lunar regolith, which gradually decreases by continued micro-meteoroid impact over a long period and thus is an age indicator of the surface. We performed multi-band (U, B, V, R and I) polarimetric observations toward the whole near side of the Moon at the Lick observatory using a 15-cm reflecting telescope with 1.1km/pixel spatial resolution at the center of the lunar disk. We analyze the color dependence of the polarization properties of the lunar regolith and discuss its implication for the study of lunar swirls.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.284-290
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• 2014

To successfully explore the moon by lunar lander, it is essential to guarantee the safe landing of lunar lander. Therefore, efficient shock absorption system of lunar lander should be designed in order to reduce landing impact force. Also, for more practical design of lunar lander, it is important to consider the effect of lunar regolith. In the line of thought, finite element model of lunar lander considering the effect of lunar regolith is developed. To reduce landing impact force, optimization of shock absorption system for lunar lander has been carried out. In optimization, sequential approximate optimization method based on meta-model is used. Through the result of optimization, it is verified that landing impact force on lunar lander can be efficiently reduced by the present optimization procedure.

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.53-63
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• 2015

For the success of future missions to the Moon and other similar cosmic environments, understanding and utilization of the lunar regolith has become essential. However, due to the scarcity and unaffordability of real lunar regolith on Earth, a number of lunar regolith simulants (e.g., JSC-1; NASA) have been developed for experimental purposes. However, Korea does not have its own lunar regolith, even though the country is planning to actively pursue lunar and space missions in the 2020s. Thus, this study has been conducted to develop a Korean lunar simulant prototype via basic feasibility attempts (e.g., raw material selection, particle size and chemical composition simulation). Finally, the first prototype of Korea's own lunar simulant has been obtained, and denominated as KLS-1.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.49-55
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• 2023

The discovery of lunar ice in the lunar polar region has fueled international interest in in situ resource utilization (ISRU) and the construction of lunar habitats. Unlike Earth's atmosphere, the Moon presents unique challenges, including frequent meteoroid impacts, direct exposure to space radiation, and extreme temperature variations. To safeguard lunar habitats from these threats, the construction of a protective shield is essential. Lunar regolith, as a construction material, offers distinct advantages, reducing transportation costs and ensuring a sustainable supply of raw materials. Moreover, it streamlines manufacturing, integration schedules, and enables easy repairs and modifications without Earth resupply. Adjusting the shield's thickness within the habitat's structural limits remains feasible as lunar conditions evolve. Although extensive research on protective shields using lunar regolith has been conducted, unresolved conflicts persist regarding shield requirements. This study conducts a comprehensive analysis of the primary lunar threats and suggests a minimum shield thickness of 2 m using lunar regolith. Furthermore, it outlines the necessary technology for the rapid construction of such protective shields.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.45.2-46
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• 2020

Various processes, such as space weathering and granular convection, are occurring on asteroids' surfaces. Estimation of the surface exposure timescale is essential for understanding these processes. The Hayabusa mission target asteroid, (25143) Itokawa (Sq-type) is the only asteroid whose age is estimated from remote sensing observations as well as sample analyses in laboratories. There is, however, an unignorable discrepancy between the timescale derived from these different techniques. The ages estimated based on the solar flare track density and the weathered rim thickness of regolith samples range between 102 and 104 years [1][2]. On the contrary, the ages estimated from the crater size distributions and the spectra cover from 106 to 107 years [3][4]. It is important to notice that there is a common drawback of both age estimation methods. Since the evidence of regolith migration is found on the surface of Itokawa [5], the surficial particles would be rejuvenated by granular convection. At the same time, it is expected that the erasure of craters by regolith migration would affect the crater size distribution. We propose a new technique to estimate surface exposure age, focusing on the bright mottles on the large boulders. Our technique is less prone to the granular convection. These mottles are expected to be formed by impacts of mm to cm-sized interplanetary particles. Together with the well-known flux model of interplanetary dust particles (e.g., Grün, 1985 [6]), we have investigated the timescale to form such mottles before they become dark materials again by the space weathering. In this work, we used three AMICA (Asteroid Multi-band Imaging Camera) v-band images. These images were taken on 2005 November 12 during the close approach to the asteroid. As a result, we found the surface exposure timescales of these boulders are an order of 106 years. In this meeting, we will introduce our data analysis technique and evaluate the consistency among previous research for a better understanding of the evolution of this near-Earth asteroid.

• Journal of Space Technology and Applications
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• v.3 no.3
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• pp.199-212
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• 2023

In contrast to the short-term nature of lunar missions in the past, lunar missions in new space era aim to extend the presence on the lunar surface and to use this capability for the Mars exploration. In order to realize extended human presence on the Moon, production and use of consumables and fuels required for the habitation and transportation using in-situ resources is an important prerequisite. The Global Exploration Roadmap presented by the International Space Exploration Coordination Group (ISECG), which reflects the space exploration plans of participating countries, shows the phases of progress from lunar surface exploration to Mars exploration and relates in-situ resource utilization (ISRU) capabilities to each phase. Based on the ISRU Gap Assessment Report from the ISECG, ISRU technology is categorized into in-situ propellant and consumable production, in-situ construction, in-space manufacturing, and related areas such as storage and utilization of products, power systems required for resource utilization. Among the lunar resources, leading countries have prioritized the utilization of ice water existing in the permanent shadow region near the lunar poles and the extraction of oxygen from the regolith, and are preparing to investigate the distribution of resources and ice water near the lunar south pole through unmanned landing missions. Resource utilization technologies such as producing hydrogen and oxygen from water by hydroelectrolysis and extracting oxygen from the lunar regolith are being developed and tested in relevant lunar surface analogue environments. It is also observed that each government emphasizes the use and development of the private sector capabilities for sustainable lunar surface exploration by purchasing lunar landing services and providing opportunities to participate in resource exploration and material extraction.