MHD Flow Field and Momentum Transfer Process of Magneto-Plasma Sail

Magneto-Plasma Sail is a propulsion system making use of the solar wind in the interplanetary space. This propulsion system creates an artificial magnetosphere as a sail catching the momentum of the solar wind. An artificial magnetosphere created by a superconducting coil is drastically inflated by plasma injection and this technique is called "Magnetic Field Inflation" which allows the spacecraft to produce a large magnetosphere without huge coils. Magneto-Plasma Sail is expected to reduce the mission time for deep space explorations. However, the propulsive performance has not been quantified because the momentum transfer from the solar wind to the spacecraft has not been clarified even in the ideal magnetohydrodynamic framework. In this study, the flow field of Magneto-Plasma Sail was simulated based on the ideal magnetohydrodynamics. The flow field was characterized by Alfvenic Mach number of the injected plasma flow, and it was clarified that MHD waves played important roles in the momentum transfer process. For generating thrust, the MHD wave has to propagate from the solar wind to the spacecraft and therefore the sub-wave speed flow region has to be created between the spacecraft and the solar wind.