Measurements of piston motion in a hypersonic gun tunnel using a microwave technique.

A microwave interferometer for determining piston motions in a hypersonic gun tunnel was developed. Owing to the specially designed microwave feeder, measurements of the piston motion with good accuracy was obtained in the case that the nozzle was connected at the barrel end as well as that the end was closed. Using this system to the hypersonic gun tunnel of Kyoto University, the effects of the piston weights, the nozzle throats and the initial pressure ratios across the diaphragm are analysed.