A parametrical study is performed of coolant dump gas ejectors for a sandwich rocket nozzle design. Five geometrical variations are simulated in four ambient conditions (static, subsonic, supersonic, vacuum) using an in-house CFD solver. The test cases are compared with a baseline case and the resulting thrust and ISP are evaluated on a local and global level. A longer dump wall is found to give the best performance in all ambient cases, with a second possibility of reducing the circumference of the nozzle end stiffener. The possibility of post-ejection coolant gas combustion is encountered for high ambient pressure, high subsonic velocity flight.

<p>Additive manufacturing of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Gun propellants are manufactured using wetted extrusion, which uses volatile solvents and dies of limited and constant geometries. On the other hand, additive techniques are faced with the challenges of maintaining the gun propellant’s energetic content as well as its structural integrity during high pressure combustion. The work presented in this thesis demonstrates the feasibility of producing functioning gun propellant grains using vibration-assisted 3D printing, a novel method which has been shown to extrude extremely viscous materials such as clays and propellant pastes. At first, the technique is compared to screw-driven additive methods which have been used in printing gun propellant pastes with slightly lower energetic content. In chapter two, diethylene glycol dinitrate (DEGDN), a highly energetic plasticizer, was investigated due to its potential to replace nitroglycerin in double base propellants with high nitroglycerin content. A novel isoconversional method was applied to analyze its decomposition kinetics. The ignition and lifetime values of diethylene glycol dinitrate were obtained using the new isoconversional method, in order to assess the safety of using the plasticizer in a modified double base propellant. In chapter three, a modified double base propellant (M8D) containing DEGDN was additively manufactured using VAP. The printed strands had little to no porosity, and their density was nearly equal to the theoretical maximum density of the mixture. The strands were burned at high pressures in a Crawford bomb and the burning was visualized using high speed cameras. The burning rate equation as a function of the M8D propellant as a function of pressure was obtained. Overall, this work shows that VAP is capable of printing highly energetic gun propellants with low solvent content, low porosity, with high printing speeds, and which have consistent burning characteristics at high pressures. </p>