Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical and Aerospace Engineering

Committee Chair

George J. Nelson

Committee Member

Robert A. Frederick

Committee Member

Jason Cassibry

Committee Member

David Lineberry

Committee Member

Gabe Xu


Hybrid propellant rockets--Design and construction, Rockets (Aeronautics), Propulsion systems


Analytic Transport Network Theory (ATN), a heuristic model developed for electrochemical systems, is adapted to predict the gas pressure drop across heterogeneous porous hybrid rocket motor grains. Experimental pressure drop estimations from previous studies of these grains disagree with existing empirical correlations that assume uniform morphology. An adapted ATN model could significantly improve the gas pressure drop prediction with relatively low resource requirements. To test the applicability of ATN, porous hybrid motor grain samples with length 40 mm, diameter 20 mm, and nominal pore size (NPS) of 200 and 100 microns, based on manufacturer specifications, were studied using microstructural analysis and pressure drop measurements. Microstructural data for twenty samples was acquired via x-ray computed tomography (XCT) at a pixel size of ∼32 microns. Pore and solid regions were segmented using visual inspection and comparison to a plexiglass calibration sample. Microstructural properties including porosity, phase size distributions, and ATN-based transport coefficients were estimated from the segmented data. A baseline resistance was derived from the estimated pressure drop for an empirical correlation applied to a highly porous case. Using the baseline result in combination with the ATN predicted transport coefficient ratio, an equivalent resistance is calculated to estimate the pressure drop as a function of Reynolds number (Re). Grain porosities of approximately 50% were estimated with the XCT data. These estimates agreed well with estimates from the Archimedes method. XCT data indicated the porous 200 and 100 NPS grains had average pore diameters of 339 and 356 microns, respectively. These pore sizes were verified by comparison to higher resolution XCT data and scanning electron microscope data. After imaging, the pressure drop was measured for ten grains of each NPS for 200



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