Magnetohydrodynamic Drag Measurements in an Expansion Tunnel with Argon Test Gas

Abstract

Magnetohydrodynamic (MHD) aerobraking experiments were conducted in the large-scale X3 expansion tunnel at the University of Queensland. The test gas was argon flowing at approximately for a quasi-steady period of . A neodymium spherical permanent magnet, suspended by string and enclosed within a 65-mm-diameter spherical forebody, was used to generate the magnetic field. An accelerometer was attached to the rear of the magnet to measure streamwise motion, allowing the Lorentz force on the magnet to be deduced according to Newton’s second law. The stagnation point magnetic flux density was varied by changing the internal streamwise location of the magnet within the forebody. Experimental results demonstrate a linear increase in MHD drag with magnetic field strength, which is in agreement with previous results from arcjet facilities. However, the MHD drag force was much lower in these experiments, even after accounting for shock density ratio and viscosity differences. This discrepancy could be due to the different freestream state generated by the two types of facilities.