27 -- Troy Howe - Pulsed Plasma Rocket- Developing a Dynamic Fission Process

Background: To realistically establish a human presence on Mars or to enable faster transit on any deep-space mission, high specific impulse and high thrust are key. Having each of these would allow for efficient propulsion and fast transit, eliminating restrictive launch windows and risks of long-term radiation exposure to crewed missions. The Pulsed Plasma Rocket (PPR) aims to meet these needs via a fissioning propulsion system that produces rapid plasma bursts. Previous efforts have examined pulsed propulsion methods, including the use of plasma as propellant, but the PPR achieves these plasma bursts via a fission-based system, wherein a highly moderated fuel projectile is propelled through a uranium barrel to reach supercriticality. The barrel and projectile material architecture results in much higher energy deposition in the projectile than in the barrel. After experiencing significant fission events, the projectile changes from a solid to a plasma over a period of a few microseconds, and is expelled through a magnetic nozzle. Methods: Performed for a Phase I NASA NIAC study to determine feasibility and performance. Computational modeling has been performed using MCNP, MOOSE, and SERPENT neutronics programs. Thermal systems analyzed using COMSOL Multiphysics. Plasma interactions modeled with SPFMax. Results: Neutronics modeling has determined the projectile constituents to include a high-assay low enriched uranium water-ice mix encased in a thin iron shell. Control drums generate a pulse of extreme supercriticality by rotating at different rates to create a Fourier series delta function which flashes the projectile into an ionized plasma at the end of the barrel. With the combined use of a coilgun as the initial propellant injector and a magnetic coil and nozzle for exhaust, the projectile is able to produce a thrust of roughly 100 kN with an Isp of 5,000s. Conclusions: The necessary criticality to reach plasma-generating temperatures can be achieved in the projectile, while maintaining overall system integrity. The ship is capable of a 2-month transit to Mars, consumes no highly enriched uranium material, and can power itself by recuperating energy from the propulsion system.