Full free-stream mach 12 scramjet testing in expansion tubes

Expanding ground test capabilities is an important point of the effort to develop efficient scramjet engines that can operate at changing Mach numbers. Rectangular-to-Elliptical-Shape Transition (REST) engines have shown to be a viable concept that can be integrated into access-to-space vehicles, operating between Mach 5 and 12. However, Mach 12 REST engines have never been tested in full free-stream mode at their design condition, as the required total pressures exceed the capabilities of reflected shock tunnels, the facilities typically used for scramjet testing. v This paper reports on new Mach 12 operating capabilitievs and subsequent full scale, free-stream REST scramjet engine experiments developed and carried out with the University of Queensland’s X3 expansion tube. This is vone of the few facilities in the world capable of reproducing the Mach 12 conditions for large scale engine testing with sufficient test time to develop steady flow. These are the first experiments with a Mach 12 scramjet engine tested at full free-stream conditions. Most importantly, the data shows successful combustion.