Date of Award
Doctor of Philosophy (PhD)
Mechanical and Aerospace Engineering
Jason T. Cassibry
Robert B. Adams
Nuclear propulsion, Pulsed power systems, Rockets (Aeronautics)--Nozzles, Magnetic fields
Pulsed nuclear (fusion, fission, and fission/fusion hybrid) propulsion systems provide the potential for 10,000 s specific impulse and specific powers of 1000 W of jet power per kg of propulsion system mass. This enables a new class of medium thrust, high specific impulse capability, resulting in 1/3 of the trip times and significantly higher payload mass fractions compared with chemical propulsion performing the same mission. One of the challenges for pulsed nuclear propulsion is the conversion of an isotropic explosion to directed thrust, another challenge is the generation of electrical power needed to run these systems. To meet both of these challenges we model the design for a pulsed power- generating magnetic nozzle. This nozzle has two functions; 1) Generate power, and 2) Generate thrust. For the first function, we develop an archetype pulsed power generation system using MATLAB and determine performance scaling given in terms of two non-dimensional parameters: the ratio of initial plasma energy to initial pickup coil energy, and the ratio of initial pickup coil inductance to primary-side transformer inductance. We find that the first ratio should be 0.01, and the second ratio should be 1 for idea system performance. We also find that for a system to provide 1.2 MJ of energy, its mass is 35 metric tons. For the second function, we leverage the software SPFMax (Smoothed Particle Fluid with Maxwell equation solver). We compare SPFMax with results from the literature for two cases: a solenoidal case and an axial case. We find good quantitative and qualitative agreement for both cases. Next, we generated three nozzle designs (7.5 MA/strut, 15 MA/strut, 30 MA/strut) and analyzed their performance. The ideal design has 15 MA/strut and generates 2,400 sec specific impulse, 16 kilo-Newton-sec total impulse, and an efficiency of 0.34. The nozzle efficiency is low, but indicates a power-generating pulsed axial nozzle design is feasible. In conclusion, further development and sub-scale testing of a power-generating magnetic nozzle would make pulsed nuclear propulsion systems more feasible, opening up an entire new class of interplanetary and interstellar missions and allowing humanity to safely explore vast new reaches of space.
Schilling, Nathan, "Modeling a power-generating pulsed nuclear magnetic nozzle" (2022). Dissertations. 249.