Activity on numerical plasma simulations by JAXA’s Engineering Digital Innovation (JEDI) Center is overviewed. Currently, R&D of two major numerical tools is conducted. First one is spacecraft charging analysis tool that can compute charging status of a spacecraft solving charged particle motions precisely. Using this information, we can evaluate onboard measurement of electrostatic probes or consider better configuration of onboard equipment of a spacecraft. Computation example of the interactions between solar wind plasma and a solar sail is shown in this paper. Second one is a numerical tool called JIEDI (JAXA’s Ion Engine Development Initiative), which aims to reduce the cost and the time required for an ion thruster life test. The JIEDI tool can numerically estimate ion bombardment to an ion thruster’s grid material to predict the erosion rate of the grid material, and preliminary analysis by the JIEDI tool showed good agreement with the real-time life test of a microwave ion thruster.

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We have developed a two-dimensional numerical code based on the Particle-In-Cell with Monte Carlo Collision (PIC-MCC) method, with representative reactions for N₂ to perform discharge dynamics in a dielectric barrier discharge (DBD) plasma actuator and to estimate generated force resulting from ion-neutral collision. Depending on the sign of the applied voltage, discharge pro-cess is observed as streamer mode or glow mode in the plasma actuator. The dielectric surface potential drastically changes as time advances due to the effect of the generated plasma on the electric field. These flow properties should be included appropriately in a macroscopic model for computational fluid dynamics (CFD). Moreover, the plasma generation process and high current generation are examined for an alternating voltage which increases the electric potential of the exposed electrode respect to the buried electrode from negative to pos-itive (positive-going). After the voltage phase changes, the discharge process changes from glow mode to streamer mode; the high current observed in past experiments may originate from this transition of the discharge mode.

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An overview of advanced space propulsion researches based on electromagnetic three-dimensional (3D) hybrid (ion particle and electron fluid) Particle-In-Cell (PIC) simulation is presented. Comparison between numerical simulation and ground experiment is conducted for two advanced propulsion concepts, MPS (Magneto Plasma Sail) and LFR (Laser Fusion Rocket), which are expected to achieve large thrust to power ratio and high specific impulse. Numerically obtained thrust levels for both systems show good agreement with that from ground experiments within a factor of two. It is found that simulation including the neutral-ion collision effect shows good agreement of thrust between numerical simulation and laboratory experiment for MPS. For LFR, non-isotropy in velocity distribution of laser ablated plasma is suggested to be a reason of the difference between the simulation and experimental result. Those findings are useful to tune the 3D hybrid PIC code for feasibility study of advanced plasma propulsion.

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We have carried out numerical simulations of MHD heat shield at several flight altitudes in a region of 48 to 72 km along the real reentry flight trajectory of OREX for examining the influence of induced magnetic field on the MHD heat shield. Thermochemical nonequilibrium effects, the Hall effect, and induced magnetic field have been taken into account in the numerical simulations. Numerical results show that the influence of induced magnetic field on the MHD heat shield can be neglected over the whole flight altitude region covered in the present study, although the magnetic Reynolds number estimated by the conventional manner in the study field of MHD heat shield is larger than unity at the altitudes above 60 km. We, therefore, declare that the magnetic Reynolds number estimated by the conventional manner cannot be used as the index parameter for assessing the necessity to consider the induced magnetic field under the situation of MHD heat shield.

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