For the evaluation of impulse bit for pulsed-magnetic nozzle thruster, a thrust stand having high signal to noise ratio under large pulsed current conditions and high sensitivity with the impulse bit of micronewton-second has been developed. All electric components generating large pulsed current for the magnetic nozzle are on the arm of the torsional thrust stand, in order to suppress interactions between large current cables and/or between cables and vacuum chamber. The developed thrust stand has a minimum detection limit of 3 μNs. The impulse bit of magnetic nozzle with laser produced carbon plasma was successfully measured as 𝐼𝑏=5.0±0.6 μNs with a laser energy of 520 mJ and a magnetic field strength of 0.53 T at the initial target position.

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The nano-satellite and probe R&D project is being carried out at Osaka Sangyo University (OSU). The nano-satellite OSU-1 (cubesat 1U (0.1 m cube), 1 kg), equipped with an ultra-low power pulsed plasma thruster (PPT) system for orbit transfer and attitude control, is being developed for launch in 2025. The mission is long-range powered flight with changing an altitude of 10 to 50 km on the low earth orbit using the PPT system. If altitude control is successful with the 1U cubesat, the potential for small and nano-satellites, specially below 1U cubesat and with 1-3(6)U ones, will increase. In the present research and development, an experimental 1J/1W electrithermal-PPT is repetitively operated in 104 shots resulting in decrease in an impulse bit from 30 to 20 μNs/shot and achivement in a total impulse of 300 mNs, although more improvement of performance is needed for practical use. As for bus devices, a camera system, a buttery system and a solar panel etc were successfully desinged. Furthermore, a total distarbance torque of 0.512 μNm on 400 km in altitude was evaluated from aerodynamic. gravity tilt, solar radiation pressure and geomagnetic torques, resulting in suitable design of magnetic torquer for the cubesat OSU-1.

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After the March 11, 2011 Great East Japan Earthquake, Dr. Hirofumi Shirakata, a former supervisor at Japan Atomic Energy Research Institute, appeared alongside Dr. Tetsuya Goto, President of Japan EXpert Clone Corporation at the time, to propose aluminum-based energy cycle research to Prof. Yoshihiro Arakawa’s laboratory. The project aimed to address the need for stable energy supply following the earthquake-triggered power shortage. Traditional alumina reduction methods, such as the Hall-Héroult process, were unsuitable due to CO and CO2 emissions. Overcoming this challenge required developing an efficient reduction method without CO or CO2 emissions. This study, led by Prof. Kimiya Komurasaki of Tokyo University, Prof. Makoto Matsui of Shizuoka University, and Prof. Masakatsu Nakano of Tokyo Metropolitan College of Industrial Technology, among others, has made steady progress despite its complexity, thanks to the dedicated efforts of numerous young researchers.

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Reducing alumina from lunar regolith allows in-situ aluminum and oxygen procurement. The Hall-Héroult process, reliant on scarce lunar carbon and being unfeasible, prompts the proposal to ablate alumina with a laser, selectively depositing aluminum onto a recovery plate. Previous experiments and numerical analyses have shown an increase in the aluminum ratio due to laser deposition; however, it has been reported that aluminum was not detected on the deposited layer when an alumina recovery plate is used. To elucidate these phenomena, molecular dynamics simulations were conducted, finding that oxygen moves to the surface of the deposition layer, forming an oxide layer on the deposition layer surface, and beneath that layers with high aluminum ratios are formed. These observational findings are consistent with previous experiments and numerical analyses.

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Laser alumina reduction using a kW-class CW laser has been studied for the goal of In-Situ Resource Utilization of lunar resources. When an alumina rod is irradiated by a high intensity laser, aluminum particles are precipitated on its surface. In this study, a rod was irradiated in hydrogen atmosphere to increase aluminum precipitation. As a result, pores were created at the molten edge of alumina rod, unlike in the argon atmosphere, and aluminum particles were precipitated at high density on the surface of these pores. This is thought to be the result of hydrogen dissolving into liquid alumina, reacting with oxygen, and going out as water vapor. In addition, by irradiating the moving alumina surface, pores with aluminum precipitation were generated over a large area of the surface or inside of the rod, and precipitation per laser output energy of 12 μg/kJ was achieved.

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In order to solve the problem of low maturity of in-situ lunar resource development technology, a new method of high power laser pyrolysis of ferric oxide under vacuum conditions was proposed. We used high power continuous laser irradiation of Fe2O3 and conducted theoretical calculations and experimental studies on the thermochemical and physical processes of ferric oxide components that may exist in lunar soil during laser irradiation. The experimental results show that: Fe2O3 pyrolysis deoxidization was successful, and there was a directly proportional tendency of laser density and deoxidization efficiency. The highest deoxidization rate was observed under a laser power density of 7.08 kW/cm2 and 30 s irradiation time. The main pyrolysis products were Fe (81.6%), Fe3O4 (7.4%), Fe2O3 (2.9%) and a small amount of Cu-Fe, W-Fe compounds (8.1%). Laser parameters of 3.54 kW/cm2, 30s obtained the highest energy efficiency of elemental Fe deoxidization, which was 6.33 mg/kJ. The pyrolysis results were consistent with thermodynamic analysis.

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Recently, the need for lunar exploration has increased as the first step toward future Mars exploration, and the construction of a lunar base is the key to permanent lunar exploration. In this study, we focused on alumina, which is abundant in lunar regolith, reduced to aluminum using laser diode ablation, and collected it. We aimed to improve the reduction ratio using hydrogen as a reductant and preheating the alumina before the laser irradiation. In this study, the laser intensity was 1.3 GW/m2, the wavelength was 940 nm, the ambient pressure was 100 kPa, and the hydrogen ratio was varied from 0-100% using a mixture of hydrogen and argon gases. Preheating was conducted up to 1300 K. The plume temperature estimated from the emission spectra increased up to 500 K by preheating, which corresponds to the increase in the reduction from 30 % to 63%, assuming chemical equilibrium. On the other hand, the temperature decreased with increasing hydrogen ratio due to the higher specific heat of hydrogen than argon. In the collection experiments, the preheating increased the adhesion on the collection plate by up to a factor of three. As a result of EDX analysis, the O/Al ratio on the collection plate decreased with preheating and did not change with the increase in hydrogen ratio.

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Alumina reduction by laser ablation has been researched towards aluminum acquisition from lunar regolith based on the view of in-situ resource utilization (ISRU). In the previous study, alumina dissociation into aluminum atoms in the ablation plume generated by continuous-wave laser irradiation was demonstrated. However, collection of the produced aluminum in the ablation plume using a recovery plate has a difficulty due to the recombination of produced aluminum and oxygen atoms during the cooling process with turbulence on the recovery plate. In this study, a recovery tube was applied to the aluminum collection system. The ablation plume contacted the recovery tube without causing turbulence, and 7.4% of ablated substances by mass adhered to the tube. By the SEM observation, aluminum particles were detected on the inner surface of recovery tube, which demonstrated aluminum collection from laser ablated alumina. The aluminum collection percentage was measured to 0.03% by chemical treatment using NaOH solution. Further improvement of the aluminum collection percentage could be optimizing the shape of recovery systems considering its physical interference with the ablation plume.

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