This research describes the theoretical mode, development and testing of an all optical flow meter capable of making a direct density measurement in a single- and multiphase cryogenic fluid. The sensing method is based on the interaction of light with the physical state of the fluid. The optical sensor only minimally interacts with the fluid, thereby not perturbing the state condition of the flow and avoiding complications of existing volumetric and mass flow devices.; The theoretical basis of the device is a Bruggeman model of effective medium theory. This provides a direct density measurement of any number of fluid phase constituents and provides an effective measurement scheme to perform the necessary calculations without undue computation.; Materials for the optical sensor were qualified and tested in a relevant liquid nitrogen cryogenic environment. The theorized device was developed through a series of prototype iterations. Various prototype devices were tested and evaluated in full-scale water and full-scale liquid nitrogen flow facilities. Results verified the response predicted by the theoretical model with an approximate 0.8% error in density measurement. Data obtained by the sensor was also used to determine a secondary density measurement, fluid velocity, and bubble sizing and distribution statistics. The sensor functioned successfully in liquid nitrogen submersion and the design has been hydrostatically tested to 204 atmospheres or 3000 pounds per square inch.; Propulsion research and development has direct roots in the sensing technology available. For liquid propulsion rocket engines the ability to measure mass flow is currently limited by the environmental constraints and approximations inherent to the existing measurement technology. The optical flow sensor can provide an enabling method for supporting test and evaluation operations as part of a ground based propulsion testing in addition to supporting safe and efficient operation of space flight and launch systems.
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