Pulsed Fission Fusion Propulsion for Faster Manned Travel Through the Solar System

Robert Adams updated the work on a phase 2 Pulsed Fission-Fusion (PuFF) Propulsion Concept. Robert works at the NASA Marshall Space Flight Center. This system should be able to achieve 15 kW/kg and 30,000 seconds of ISP. This will be orders of magnitude improvement over competing systems such as nuclear electric, solar electric, and nuclear thermal propulsion that suffer from lower available power and inefficient thermodynamic cycles. Puff will meet an unfilled capability needed for manned missions to the outer planets and vastly faster travel throughout the solar system.

A tiny lithium deuteride and uranium 235 pellet will be fired into a shell of structure that will complete a circuit and generate high voltages and pressures that will compress the pellet and cause fission and fusion to occur.

Heat from fission fuel increases the reactivity of the fusion fuel and the neutron flux may breed additional fuel to fuse. Additionally, the neutron flux from the fusion fuel will induce fission. This coupling can drastically reduce the driving energy required to initiate the burn and drastically improve output. This concept has been examined in the past by Winterberg and is being investigated in support of a Pulsed Fission-Fusion (PuFF) engine concept at Marshall Space Flight Center and the University of Alabama in Huntsville.

They are doing many experiments to validate and create designs and they are doing computational models and simulations.

There are potential spinoff materials and technology from their project. Fission Molybdenum-99 is used in nuclear medicine. The decay product of Mo-99, Tc-99m, is the workhorse isotope in nuclear medicine for diagnostic imaging. Tc-99m is used for the detection of disease and for the study of organ structure and function. This is potential a billion market.

They could also develop advances in 3d printing of metals. They will be able to work with high-temperature metals. Higher currents and pulse rates will enable 3d printing with high-temperature metals without high pressures and with better grains and finish.

Research has focused largely on Magnetic Confinement Fusion (MCF) and Inertial Confinement Fusion (ICF). MCF contains plasma at a steady state at low densities as opposed to ICF which implodes small quantities of fuel in ultra-short high-density reactions. These methods struggle to reach the temperatures required due to limitations of materials and instabilities that arise in both processes. Magnetic Confinement Fusion (MCF) also known as Magnetized Target Fusion (MTF) operates at an intermediate density regime and employs a magnetic field to trap charge particles in order to reduce energy lost. This drastically reduces the driving energy required. Research into this method suggests this approach may offer a means of achieving the conditions necessary for nuclear fusion. The PuFF engine research seeks to operate and take advantage of the MIF regime.

The Pulsed Fission-Fusion (PuFF) concept engine uses a z-pinch configuration with a fusion core and a fission liner to boost energy production and reduce power required to drive the reaction, hence a hybrid target. The fission process heats the fusion fuel, increasing the fusion reaction rate. The fusion products then enhance fission reaction. The processes boost each other’s reaction rates.

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