Large-scale free-piston-driven multi-mode shock expansion tunnel

X3/R is a new large-scale free-piston-driven dual-mode shock expansion tube, developed and operated collaboratively by the University of Queensland (UQ) and Australia's Defence Science and Technology Group (DSTG). The facility can be converted between a long-duration reflected shock tunnel (RST), a super-orbital expansion tube (X-mode), and a non-reflected shock tube (NRST). In RST mode, the facility is currently capable of producing 600mm diameter Mach 7 test flows at 25-50kPa dynamic pressure for more than 10 ms. In expansion tube mode, the facility can reach enthalpies up to 80 MJ/kg for test times on the order of 500-1000 mu s. This paper presents the new facility, summarizes its current operational capabilities, and discusses key the technical challenges overcome during its development.