Charging of the lunar surface induced by solar radiation can potentially threaten in situ resource utilization. Associated issues include dust adhesion and material degradation. Photoelectric currents are the primary cause of surface charging. This work reports on the development of a unit capable of measuring photoelectric currents in a vacuum chamber, which can simulate surface charging under conditions similar to those on the moon in daytime. The main components of the unit are a mesh grid, a photocathode specimen, and a ring collector. Photoelectric currents from an aluminum sample were measured by adjusting the electric potential of these components, and the impact of the electric potential of each component is discussed. Calculating the expected electric current within the experimental setup allowed validation of the current measurements: the measured and calculated values agreed well with an error of ~5.5%. Finally, the photoelectric currents for various metals (aluminum, nickel, and copper) were measured using the same experimental setup. The results showed consistent measurement of photoelectric current values across all metals. This study offers insights into the development of units for measuring photoelectric current and methodologies to validate their results.

In situ resource utilization (ISRU) technology in lunar exploration is becoming more important, and the interest in lunar soil that covers the lunar surface is growing. However, most existing lunar environment simulation facilities mainly provide pressure and temperature conditions of the moon without considering lunar regolith. To reduce the risk of failure of systems on the lunar surface, system validation testing in the lunar surface environment including regolith bed is required. When soil is put into a vacuum, chamber and pumping-down process is started, soil disturbance phenomenon is observed, and it disturbs testing conditions and could make trouble of the vacuum chamber system. We have succeeded in creating a vacuum environment without soil disturbance by reducing pumping down speed, and we developed a lunar surface environment simulator including lunar soil. The new lunar surface environment simulation facility will enable more reliable lunar surface environment testing and foster lunar ISRU technology development.

Research on the lunar environment and payloads is actively progressing with an increasing interest in lunar exploration. When the moon orbits the earth, the electrical properties of the lunar surface change variously by sunlight and plasma. Therefore, for the payload to operate stably on the lunar surface, we should understand these electrical properties and develop a technology that can respond to these environments. In this study, a vacuum chamber is developed, which can simulate the electrical properties of the lunar day/night, and a terminator section is developed using a vacuum ultraviolet lamp and an electron beam. Further, the simulated environment is evaluated using Faraday cups and photodiodes. We intend to lay the foundation for the evaluation of the electrical impact on various devices and technologies that can be used on the lunar surface using the vacuum chamber that is capable of simulating the electrical environment on the lunar surface.

A dusty thermal vacuum chamber (DTVC) containing a regolith simulant bed is essential for testing equipment and techniques related to lunar surface exploration. Space agencies have been reluctant to operate a DTVC because of the challenge of controlling soil disturbance of the lunar regolith simulant bed during pumping down or depressurization, which may contaminate or even damage the chamber and vacuum equipment. There appears to be no previously available solution to this problem, or how to avoid it. We investigated the mechanism of soil disturbance during depressurization and established a criterion for evaluating its occurrence. The proposed criterion was validated by extensive experiments and numerical modelling to simulate air evacuation from soil voids. There is a critical pressure difference (CPD) between the top and bottom of the lunar regolith simulant bed that causes soil disturbance during depressurization. We found a simple equation estimating the CPD and further provided guideline on the optimum depressurization rate to avoid soil disturbance before the target vacuum level is achieved under varying soil conditions.

Thermal shrouds used for cryogenic temperature generation in a vacuum chamber can be manufactured using various materials and shapes. A shroud, which consists of two connected plates and a filling cooling material between the plates, has good cooling efficiency. However, it is difficult to manufacture large size shrouds, and high costs are required. In this study, a thermal shroud consisting of a stainless-steel tube and a copper plate was developed, and the shroud was simple to manufacture and exhibited high thermal conductivity. A sample shroud was manufactured, and cooling tests were performed in a small vacuum chamber to evaluate the fabrication and cooling performance of the developed thermal shroud. From the cooling test results, the shroud satisfied target performance, which was a surface temperature of -190 degrees C and a temperature uniformity within 10 degrees C, and the shroud fabrication was confirmed through thermal cycling tests and leak tests. This study verifies the suitability of applying the proposed shroud type to large size shrouds.

The scientific, economical and industrial values of the Moon have been increased, as massive ice-water and rare resource were founded from the lunar exploration missions. Korea and other major space agencies in the world are competitively developing the ISRU (In Situ Resource Utilization) technology to secure future lunar resource as well as to construct the lunar base. To prepare for the lunar construction, it is essential to develop the rover based construction spatial information technology to provide a decision-making aided information during the lunar construction process. Thus, this research presented the construction spatial information technology based upon rover’s camera system. Specifically, the conceptual design of rover based camera system was designed for acquisition of a rover’s navigation image, and lunar terrain and construction images around the rover. The reference architecture of the rover operation system was designed for computation of the lunar construction spatial information. Also, rover’s localization and terrain reconstruction methods were introduced considering the characteristics of lunar surface environments. It is necessary to test and validate the conceptual design of the construction spatial information technology. Thus, in the future study, the developed rover and rover operation system will be applied to the lunar terrestrial analogue site for further improvements.

The Korea Institute of Civil Engineering and Building Technology is currently developing a planetary surface environment simulator for the Moon and Mars. Known as a dirty thermal vacuum chamber (DTVC), this simulator contains a large volume of soil that undergoes extensive testing using special equipment. The construction of the DTVC started in 2017 and is expected to be completed by the end of 2019. The DTVC is a large vacuum chamber with an inner space measuring 4.70 m (W) x 4.70 m (H) x 4.65 m (L). The goal of the first construction stage was to achieve a target pressure of 5 x 10(-8) mbar without soil. After assembling the chamber body and the pumping system, we attempted to reduce the leakage with the help of pressure buildup analysis, helium leak testing, and residual gas analysis. After vacuum diagnosis of the chamber, the overall leakage decreased and the target pressure was achieved in approximately 93 hours after the pumping commenced.

Nowadays, many space agencies have interested in surface mission and In-Situ Resource Utilization(ISRU) technology. A thermal vacuum chamber is generally used for validation of space technology. However, ISRU technology needs to be verified in the planetary surface environment that includes regolith beds. Korea Institute of Civil engineering and building Technology(KICT) is building a lunar surface environment simulator that provides 10-4 mbar pressure with regolith bed and temperature control (-190℃-150℃). We call the facility as Dirty Thermal Vacuum Chamber(DTVC). KICT’s DTVC is being built over 3 years and will be completed in the end of 2019.