The liquid rocket power plant has at tained a position of importance which was hardly imaginable a few years ago to most of the engineering profession and the public. Its continued advancement can be expected as long as man persists in want ing to go higher, farther and faster. One aspect of rocket development which is of fundamental importance is, of course, testing. The major problems of rocket testing — problems which differentiate it from other engineering test — arise from the presence, in combination, of high pressures, high temperatures, high velocities, high noise levels, high flow rates, high heat transfer rates, high forces, high design stresses, short times, and novel and dangerous working fluids. It is clear that the old a d a g e "One test is worth a thousand expert opinions" could hardly find a better application.