Reproduction of Plasma Conditions during Atmospheric Re-entry by Injecting Gun-Generated Plasmoids into a Gas Atmosphere

Reentry capsules of space probes and reusable launch vehicles (RLVs) generate shock waves when they re-enter the atmosphere at supersonic velocity, and plasma is generated due to aerodynamic heating in front of the fuselage. Plasma can affect the radar's radio-reflective properties and communication with ground stations during radar tracking. However, especially in Japan, actual flight data accumulation is not enough, and investigations are mainly conducted through simulations and experiments with test vehicle launches. The goal of this study is to reproduce the plasma conditions during atmospheric re-entry in the laboratory and measure the interaction between the radar and the plasma under these conditions. The first step is to reproduce the plasma conditions. The experimental device consists of a magnetized coaxial plasma gun (MCPG) connected to a quartz chamber. When a hydrogen plasmoid is injected into a vacuum space using this MCPG, the plasma density is 10¹⁹ m^-3 and the velocity is 50 km/s. To reproduce the plasma conditions during atmospheric re-entry, the density and velocity should be 10¹⁸–10²⁰ m^-3 and 2–6 km/s, respectively. To approach this, a high-speed plasmoid is ejected into a vacuum chamber filled with neutral gas. By ionizing the neutral gas, it is expected that the plasmoid decelerates. Plasma parameters will be measured using a triple probe, interferometer, and a high-speed camera.