System Analysis for a Fusion Propelled Spacecraft

Abstract

Nuclear-fusion-based power generation has a multitude of potential applications, one being spacecraft propulsion. The extreme specific impulse achievable with fusion prod- ucts provides for large total momentum changes while using substantially less propellant. Several auxiliary subsystems are required to support the application of fusion-based power to spacecraft propulsion. These subsystems include one for efficient propellant heating, one for power generation, and one for reactor shielding and structural integrity. Two centrifugally-confined magnetic mirror configurations are utilized, one to confine the fu- sion plasma and one to trap and heat an auxiliary propellant in order to increase thrust. Estimates on propellant mass requirements and design constraints on the propellant cham- ber are derived. Power generation techniques utilizing byproduct radiation from the fusion process are integrated into the reactor structure. Waste heat from neutron power conver- sion provides preheating of propellant, and a radiator was optimally sized for removing the remaining waste heat. Solid-state thermionic power conversion technology is explored to utilize bremsstrahlung radiation. Models for the magnet shielding are created, and the rate of neutron absorption and energy deposition for several different shielding materials are de- termined. In order to address the tensile and compressive stresses resulting from the fusion reactor magnets, support beam cross-sections are optimized. A system of heat pipes, mag- nets, and an enclosing shroud is designed to support reactor functions and prevent damage to system components. Comparisons are drawn between existing propulsion systems and a model fusion system. The viability of our model fusion system for solar system exploration is discussed.