Yusuke Takahashi 교수

Numerical simulations of the plasma flow and electromagnetic wave around a membrane-aeroshell type reentry vehicle were performed using various physical model combinations, and the possibility of radio frequency blackout of transceiver antenna embedded at the rear of the vehicle was investigated. The flowfield was assumed to be in thermochemical nonequilibrium, and it was described by the Navier–Stokes equations with a multitemperature model and the equation of state. The simulations were perfor

Abstract An analysis model of plasma flow and electromagnetic waves around a reentry vehicle for radio frequency blackout prediction during aerodynamic heating was developed in this study. The model was validated based on experimental results from the radio attenuation measurement program. The plasma flow properties, such as electron number density, in the shock layer and wake region were obtained using a newly developed unstructured grid solver that incorporated real gas effect models and could

A numerical simulation model that combines the plasma flows and electromagnetic waves around a reentry vehicle during atmospheric reentry was developed to evaluate the radio frequency blackout and plasma attenuation. The physical properties of the plasma flow in the shock layer and wake region were obtained using a computational fluid dynamics technique. The electromagnetic waves were expressed using a frequency-dependent finite difference time domain method with the plasma properties. Combined

Numerical simulation of a 20 kW constrictor-type arc-heated flow was carried out, and the distribution of the nonequilibrium flow-field properties was obtained. The flow field was described by the Navier–Stokes equations with a multi-temperature model, tightly coupled with the electric-field and radiation-field calculations. As a radiation model, an accurate and low-cost model was introduced into the flow-field simulation. It was confirmed that the plasma flow inside the arc-heated facility is i

Numerical simulations are carried out and the distributions of flowfield properties are obtained for nonequilibrium flows in a 20 kW constrictor-type and a 750 kW segmented-type arc-heated wind tunnel. In these arc heaters, it is confirmed that each plasma flow is highly in nonequilibrium and arc discharge plays critical roles. The flowfield is described by the Navier-Stokes equations with a multitemperature model. To validate the present numerical model, the numerical solutions are compared wit

Abstract Radio frequency (RF) blackout during atmospheric reentry leads to the cutoff of communication with ground stations and/or data-relay satellites. This causes significant problems during reentry, and thus, mitigation methods have been in high demand. In this study, we numerically demonstrate a novel method for mitigating the RF blackout using surface catalysis effects. Plasma flow behavior and electromagnetic wave propagation around a reentry vehicle were investigated in detail. The appro

A numerical analysis of electromagnetic waves around the atmospheric reentry demonstrator (ARD) of the European Space Agency (ESA) in an atmospheric reentry mission was conducted. During the ARD mission, which involves a 70% scaled-down configuration capsule of the Apollo command module, radio frequency blackout and strong plasma attenuation of radio waves in communications with data relay satellites and air planes were observed. The electromagnetic interference was caused by highly dense plasma

Turbulent plasma flow in large-scale arc heaters such as JAXA 750 kW and NASA 20 MW facilities was investigated and distributions of flow-field properties were successfully obtained. The turbulent flow field was described by the Navier–Stokes equations with a multitemperature model, which was tightly coupled with electric-field and radiation-field calculations. An accurate and low-cost radiation model, and a low Reynolds number two-equation turbulence model were introduced into the flow-field si

A demonstration flight of an advanced reentry vehicle was carried out using a sounding rocket. The vehicle was equipped with a flexible (membrane) aeroshell deployed by an inflatable torus structure. Its most remarkable feature was the low ballistic coefficient that enables reduction in aerodynamic heating and deceleration at a high altitude. During the suborbital reentry, temperatures at several locations on a backside of the flexible aeroshell and inside the capsule were measured by means of e

We have built a wireless mesh network testbed, which is tolerant of disaster and aim to resolve a digital divide issue in rural mountain areas. This testbed is located in two areas and has total 22 nodes which are installed on the power poles in these areas. Two areas are connected to a control server at Niigata university with broadband wireless access systems using 5 GHz band via a gate way node at the local-government office, which is located at the center of two areas. Each node has two wire

A communication blackout is one of the major problems that occurs during the reentry of a satellite into the Earth’s atmosphere, which is caused by the reentry plasma blocking electromagnetic waves near the satellite for telecommunication. Moreover, it prevents tracking and data transmission, resulting in inaccurate prediction of landing sites and data loss. Therefore, there is a necessity to evaluate the propagation of electromagnetic waves in the reentry plasma and to mitigate the communicatio

A flight experiment of an inflatable reentry vehicle, equipped with a thin-membrane aeroshell deployed by an inflatable torus structure, was performed using a Japan Aerospace Exploration Agency S-310-41 sounding rocket. The drag coefficient history was evaluated by analyzing the acceleration of the vehicle with the atmospheric density and temperature using a global reference atmospheric model. The vehicle successfully demonstrated deceleration. During the reentry flight, the position, velocity,