Plasma jets created by a discharge of current density in the range of 20-200 kA/cm/sup 2/ were studied experimentally. Time-of-flight, spectroscopy, and X-ray imaging techniques were used to measure the velocity, temperature and the density of the plasma jet. These techniques were applied to the plasma of a free jet both in air and in vacuum, resulting in reliable and interrelated values that coincide and confirm each other. The results are pertinent to the use of high-pressure discharges to generate plasma jets for electrothermal launchers. >