Journal of the Society of Motion Picture and Television Engineers (1950-1954)

times the cameras have stood for hours at below 0 F temperature waiting for a firing to commence, yet on the signal to fire the cameras performed faithfully. Wind direction was another important factor which had to be considered. Whenever possible, a location was chosen out of the path of corrosive acid fumes blowing toward the camera position. This was necessary for the protection of of the camera as well as for visibility. The acid clouds were thick enough to obscure the vision of the flame if they hung too long in the direct line from lens to subject. Synchronization of the camera to obtain the start or shut-down phases of the firing was controlled from the master control panel by the test engineer, by arrangement of a suitable electrical circuit. Research Applications The theory and practice of liquidpropellant rocket thrust-chamber design has been partially based on empirical data, often extrapolated or adopted from "conventional" combustion-engine data. With the postwar increase in the development of rocket thrust chambers has come an increase in some of the characteristic problems of these engines. Similarly, the adoption of new propellants (as compared with the "classical" liquid-oxygen and alcohol combination) has added to these problems. Some of the undesirable behaviorisms commonly met with in thrust-chamber-operation combustion are rough burning or "instability," low combustion efficiency and propellant ignition delays leading to explosive starting transients. The relative significance and mechanism of the interactions between the liquid propellants injected into the combustion chamber, the actual combustion processes and the chamber geometry are not yet fully understood. "Normal" instrumentation, such as pressure transducers, thrust recorders, flowmeters, and thermocouples ordin arily suffice to indicate the various fluid and combustion parameters which serve as a measure of the motor's behavior. However, when conditions such as unexplainable rough burning occur, and when the cause cannot be ascertained from the parameters measured with this instrumentation, other avenues of research must be explored — not only for the alleviation of the undesirable characteristic, but also for the gathering of new facts which could serve as a foundation for continuing motor development. High-speed motion-picture photography is one of the new but promising tools employed for this purpose. A rocket thrust chamber or "motor" consists essentially of a propellant injector and a throated cylindrical chamber. This serves as a container for the combustion of the liquid propellants, which enter at high velocities through the injector. The pressure and temperature in a typical chamber may reach 300 psi and 2600 K. At the throat the pressure is lower while the hot combustion gases are exhausted at sonic velocity and then expanded to the atmosphere in a nozzle, reaching supersonic velocity. Since the motor seems so uncomplicated, an obvious method of studying the combustion in the chamber would be the construction of a transparent chamber which could permit the direct viewing of the burning pattern within. This has, in fact, been attempted by several investigators1 within the last few years. Severe design and operating difficulties were encountered — mostly due to the high chamber pressures and temperatures and sometimes erosive qualities of the propellants (in some cases aniline and red-fuming nitric acid). Due to mechanical and optical problems flatsided chambers were usually built, or narrow strip inserts of Pyrex or quartz2 were located at strategic points in the wall. Strangely enough, Plexiglas walls proved most suitable (when "normal" photography only was desired) since the very high chamber temperatures melted 600 May 1953 Journal of the SMPTE Vol. 60