Date of Award

5-2019

Degree Type

Report

Degree Name

Master of Science (MS)

Department

Mechanical and Aerospace Engineering

First Advisor

Stephen Whitmore

Abstract

Chamber pressure, as it develops during rocket combustion, strongly correlates with many of the internal motor ballistics, including combustion stability, fuel regression rate, and mass flow. Chamber pressure is also an essential measurement for calculating achieved thrust coefficient and characteristic velocity. Due to the combustion environment hostility, sensing chamber pressure with high-fidelity presents a difficult measurement problem, especially for solid and hybrid rocket systems where combustion by-products contain high amounts of carbon and other sooty materials. These contaminants tend to deposit within the pneumatic tubing used to transmit pressure oscillations from the thrust chamber to the sensing transducer. Partially clogged transmission tubes exhibit significant response latency and damp high frequency pressure oscillations that may be of interest to the testers. A maximum-likelihood method for fitting a second order model to chamber pressure response is presented. The resulting model was used to reconstruct a high-fidelity motor response via optimal deconvolution. The method was applied to small hybrid-thruster results from three separate testing campaigns. Key performance parameters such as thrust coefficient, characteristic velocity, and specific impulse were re-calculated using the reconstructed data. Results were compared to the unreconstructed data, and are shown to exhibit consistently better agreement with theoretical predictions.

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