All experiments were carried out in the T5 hypervelocity shock tunnel (Figure 2) at GALCIT. The facility operates in the standard reflected shock tunnel mode with the exception that the high pressure and temperature on the driver side are produced by free-piston adiabatic compression.
Figure 2: Sketch of the T5 hypervelocity shock tunnel. Not depicted is the test section and dump
tank to the right of the nozzle.
The piston is launched by high pressure air from a secondary air reservoir, compressing the driver gas, a mixture of Helium and Argon, to the desired diaphragm burst pressure. Typical secondary reservoir pressures vary from 5 MPa to 13 MPa and burst pressures from 30 MPa to 120 MPa. Once the diaphragm bursts, a shock wave travels at speeds from 2 km/s to 5 km/s through the shock tube part of the tunnel, compressing and heating the test gas. When the shock wave reflects off the end of the tube, a high pressure, high temperature reservoir is produced. For air and nitrogen runs, reservoir pressures vary from 10 MPa to 85 MPa and enthalpies from 4 MJ/kg to 27 MJ/kg. For carbon dioxide runs, reservoir pressures vary from 40 MPa to 95 MPa and enthalpies from 3 MJ/kg to 10 MJ/kg.
The reservoir gas is then accelerated through a contoured nozzle into the test section. The useful test
time is approximately 1 ms but varies with reservoir enthalpy[8]. The nozzle is designed to
produce a freestream around Mach 5 with air. Freestream unit Reynolds numbers vary from
2 
10 
m 
to 10 10 m in air and nitrogen, and from
4 10 m to 20 10 m in carbon dioxide.
Pressure transducers at various locations inside the shock tube give the shock speed v 
, initial shock tube
pressure P 
, and stagnation pressure P 
. From these numbers, an equilibrium calculation gives the
rest of the reservoir conditions such as composition and enthalpy. These are then used the find the
freestream conditions using a quasi 1D nonequilibrium nozzle code.
Further details on the performance and operation of the T5 shock tunnel are given in Hornung[9].