Experimentally Simulating Giant Planet Entry in an Expansion Tube

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 proposed22.3 km/sUranus entry, but not of the proposed26.9 km/sSaturn 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 required22.3 km/sof 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.