Strategies for Optical Measurements in Rocket Plumes
Abstract
An ideal rocket engine sensing system might probe several key elements of the
rocket engine including: the fuel and oxidizer supply for mass flow rate and
impurities, the combustion chamber for pressure and mole fraction of reactants,
or the plume for temperature and mole fraction of products. This thesis focuses
on the rocket plume component of a rocket engine sensing system. The rocket
plume sensor consists of a wavelength scanning laser that spatially sweeps
through the rocket plume in order to determine the temperature, water mole
fraction, and pressure at different positions in an axially symmetric plume.
Because of the low absorbance that will occur in a small rocket plume (<1% for a
2 inch diameter plume), all noise must be minimized. The three largest sources
of noise are mode noise, beamsteering, and laser intensity noise. Throughout
this research, these three sources of noise are studied in depth. Final
recommendations are given for designing a system that will successfully
measure these qualities in a rocket plume.