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Temperature Measurements of Rocket Flames

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A field-type instrument for indirectly measuring rocket flame temperature by measuring its spectral emissivity and emission in the ultra- violet spectrum is described. Emission is measured by focusing an image of a selected point of the flame upon the entrance slit of a monochromator and recording the output of a photo multiplier placed at the monochromator exit slit. Emissivity is taken to be equal to the absorptivity, measured through the flame at the same selected point. These quantities are substituted into Wiens radiation law and temperature is calculated. Incorporated in the instrument are two chopper wheels which Interrupt the light beam, allow essentially simultaneous recording of both quantities, and permit the use of ac amplifiers. The data is presented upon a cathode-ray tube and recorded upon 35-mm film. The optical portion of the instrument is mounted on a heavy iron stand to withstand the vibration produced by the motor and is transportable along the axis of the flame. Data is recorded as a function of distance from the motor throat. Difficulty with unwanted noise signal was encountered and minimized while using the instrument on an oxygen-alcohol reaction motor. Further reductions of noise effects were obtained by averaging data over a time interval of a tenth of a second, which resulted in a temperature determination for every inch of travel from the throat. Preliminary temperature values of approximately 2400 degrees K to 2600 degrees K were measured. The possibility of further reduction of noise signal is indicated, and plans to modify the existing instrument are in process. It is also planned to provide electronically averaged data recorded on ink recorders in addition to the unaveraged data recorded on film.

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  • Combustion and Ignition

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