Generating High Speed Earth Re-entry Test Conditions in an Expansion Tube for Interplanetary Return Missions

Abstract

In 2010, planetary entry probe missions to Uranus and Saturn were proposed. This paper details an investigation exploring the operating limits of the X2 superorbital expansion tube at the University of Queensland for the simulation of test conditions related to these proposed entries. Theoretical calculations showed that X2 could recreate the stagnation enthalpy of the proposed 22.3 km/s Uranus entry but not the stagnation enthalpy of the proposed 26.9 km/s Saturn entry. Experiments were able to confirm the theoretical performance calculations. However, losses caused some of the experimental shock speeds to be up to 10% slower than predicted, and due to the high velocity nature of the experiments, the shock speed errors were large making it difficult to properly quantify the test conditions. Further theoretical analysis investigated the possibility of using a more powerful free piston driver to simulate the Saturn entry conditions, and the analysis showed that with a slightly more powerful driver than X2's current most powerful configuration, the stagnation enthalpy of the proposed Saturn entry or other slightly faster entries proposed in the literature could be simulated. However, a very powerful driver would be required to recreate the stagnation enthalpies of these entries with the excess enthalpy needed to perform binary scaled experiments for an X2 sized facility.