Expansion tubes in Australia

Expansion tubes are hypersonic impulse facilities which are able to produce chemically correct, high enthalpy test flows. They are ideally suited to reproducing super-orbital flight through different atmospheres, and provide an increasingly important tool for aerothermodynamic studies of planetary entry vehicles. Furthermore, their uniquely high total pressure capability makes them the only class of facility currently able to reproduce the free-stream total pressures associated with high Mach number scramjet powered access-to-space. In 1987 The University of Queensland was the first research group to use a free-piston driver to power an expansion tube, and presently operates two such facilities, X2 and X3. While the free-piston driver can maximise the performance of the expansion tube, this mode of operation relies on complex flow processes, provides short test duration, and raises many other challenges in terms of test flow characterisation, instrumentation, and so forth. In the process of developing its own facilities, The University of Queensland has identified and addressed many of these challenges, and in X2 and X3 it has established high performance and reliable capabilities for routine ground testing at hypersonic flight conditions.