The Bremen University Hypersonic Tunnel is a facility for the experimental investigation of fluid flow phenomena in the hypersonic speed range between Ma = 6 to 11. The Wind Tunnel is a special kind of pressure vacuum tunnel called Ludwig tube. In a pressure vacuum tunnel high-pressure air is stored as in blowdown tunnels and vacuum is stored as in indraft tunnels, for tunnel operation. The high pressure air is introduced in the test section and exhausts into the vacuum chamber. Pressure vacuum tunnels are used when the pressure required for operating a blow-down tunnel become too high. By exhausting the tunnel to a low pressure, the overall tunnel pressure ratio required for operation at a given Mach number can be achieved at a greatly reduced operating pressure.