Design of Experiments for Expansion Tube Evaluation of Magnetohydrodynamic Aerobraking for Earth Return from Deep Space

Abstract

In this paper a series of experiments are designed aiming to test the MHD aerobraking concept in an expansion tube, where the operating conditions are representative of a realistic Earth reentry flight condition. An expansion tube can generate the flow properties relevant to Earth reentry conditions, matching the associated velocity and density. These facilities can also ensure that ionization is confined to the shock layer, which is a major characteristic of a reentry flight, and which arcjet facilities cannot provide. In the first part of this paper several Earth return trajectories are considered, including Low Earth Orbit, Moon, Mars and Asteroid return missions. It was found that a significant MHD interaction can be expected to occur for a large portion of the studied trajectories, provided that the vehicle size and velocity is sufficient, which is true for most of these missions. In the second part, the flow processes that take place in an expansion tube are modeled analytically, using NASA’s CEA2 equilibrium chemistry solver, and with the Navier-Stokes flow solver, Eilmer4. It is shown that a suitable non-ionized freestream can be provided by UQ’s X2 and X3 facilities, along with a high MHD interaction, while matching real flight conditions from past Earth reentry missions. Two scaled reentry experiments are proposed, based on NASA’s Stardust, one in X2, the other one in X3. More detailed analysis with Eilmer4 shows that chemical non-equilibrium effects in the shock layer are significant, especially for the X3 condition, hence finite-rate chemistry will be needed to analyze these experiments.