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This paper reports on an experimental study of magnetohydrodynamic aerobraking using an expansion tube facility, which can generate the correct electrodynamic boundary conditions for spacecraft atmospheric entry. Argon test gas was selected for its relatively simple chemistry, making it well suited to develop experimental test cases for numerical code development. Test models were constructed from either spherical neodymium permanent magnets or steel balls. Ceramic paint was used as an electrically insulating surface boundary condition for experiments where this was required. Finite-rate reacting computational fluid dynamics of the experimental configuration indicates that relatively long duration argon relaxation times lead to a highly nonequilibrium shock layer in which a significant Hall effect arises. This is important because it is expected that future flight vehicles using magnetohydrodynamic aerobraking technology will also be operated at flight conditions where Hall effect is strong. Shock stand-off was measured using high-speed luminosity imaging for various magnetic and nonmagnetic model configurations. Experimental results in this paper support previous numerical studies that found that only an electrically insulated model surface can generate a significant magnetohydrodynamic interaction when Hall effect is strong. [ABSTRACT FROM AUTHOR]

In 2010, the U.S. National Research Council proposed planetary entry probe missions to Uranus and Saturn. This paper details an investigation exploring the operating limits of the X2 superorbital expansion tube at the University of Queensland for the simulation of atmospheric entry test conditions related to these missions. Theoretical calculations indicate that X2 can recreate the stagnation enthalpy of the proposed 22.3km/s Uranus entry, but not of the proposed 26.9km/s Saturn entry. Experiments were generally able to confirm the theoretical predictions; however, internal loss mechanisms caused experimentally measured shock speeds to be up to 10% slower than predicted. One test condition was shown to achieve the required 22.3km/s of the proposed Uranus entry, and it was proposed that, with a slightly more powerful driver condition, Saturn entry and scaled Uranus entry test conditions could be simulated in X2. The use of a faster response, optically based shock detection system was also proposed to lower test condition uncertainties for such high-speed conditions. [ABSTRACT FROM AUTHOR]