Experimental Investigation of Magnetoplasma Sail with High Beta Plasma Jet

Abstract

Magnetoplasma Sail (MPS) is one of the next generation in-space propulsion systems that utilize the interaction between the solar wind and the magnetosphere inflated by the plasma injection around a spacecraft. An important issue of MPS is thrust increase by the plasma injection. Experimental validation of the thrust characteristics is very important before applying the idea of the thrust increase by the plasma injection to realistic spacecraft design. In order to conduct a scale model MPS experiment, a laboratory simulator was designed and constructed inside the space chamber (2 m in diameter). As a solar wind simulator, a triple magnetoplasmadynamic arcjet generates a high-speed (>20 km/s), high-density (>10 17 m -3 ) hydrogen plasma jet of 0.8 ms duration. A small coil (76 mm in a diameter) and Mini-MPD arcjet as a MPS simulator was immersed inside the simulated solar wind. The thrust characteristics of MPS with plasma injection have been experimentally investigated as a function of the magnetic moment M and the dynamic pressure of the injected plasma P inf .The thrust gain is growing both with β β β β k value which is ratio of the dynamic pressure of the injection plasma to the magnetic pressure, but the thrust saturation was observed at the high β β β β k condition at the injection point (β β β β k~1 ). The maximum thrust gain in this paper which is the ratio between the thrust with plasma injection and the thrust without plasma injection was about 4.1. Nomenclature ∆t= operation time (0.8 ms) C d = thrust coefficient F = Thrust, N L = magnetospheric size, m M = magnetic moment, Tm 3 P = dynamic pressure, Pa r c = radius of coil, m Rm = magnetic Reynolds number S = blocking area of magnetosphere, m 2 u = velocity, m/s β k = β k value (P/B 2 /2µ 0 ) δ = skin depth, m µ 0 = magnetic permeability, H/m ρ = density, kg/m 3