There are several technological problems in designing and constructing a hyper-velocity wind tunnel:
*supply of high temperatures and pressures for times long enough to perform a measurement
*reproduction of equilibrium conditions
*structural damage produced by overheating
*fast instrumentation
*power requirements to run the tunnel
Simulations of a flow at 5.5 km/s, 45 km altitude would require tunnel temperatures of as much as 9000 K, and a pressure of 3 GPa.