Gradient Field Imploding Liner Fusion Propulsion System

Human exploration of the solar system beyond our immediate neighborhood requires significantly faster transit times than offered by current or near term in-space propulsion systems. Crewed missions to Mars, Saturn, or other deep space destinations must balance the benefits of exploration against concerns for crew health and survivability; at present there are no implementable countermeasures against the high energy radiation associated with solar flares and cosmic radiation, or the deleterious effects of long duration weightlessness on the human body. Reducing astronaut trip times will help mitigate these survivability issues, while simultaneously reducing crew logistics mass and overall mission cost. Deep space robotic missions such as the notional Thousand Astronomical Unit mission will also benefit from more rapid trip times by delivering instruments and providing data within the career lifetimes of the scientists at home. This Phase I project has evaluated the dynamics associated with a novel magnetized target fusion system proposed for rapid solar system exploration. Replacing the standard Θ-pinch geometry of a static target within a rapidly rising axial magnetic field to generate radial compressive forces, the concept under investigation injects a target at high axial velocity into a static axial magnetic field, creating similar radial compression forces in a geometry more suitable for in-space propulsion. During the Phase I effort, a semi-analytic model was developed to simulate the key physics of target injection, radial liner compression, and conditions for gainful fusion energy release. A number of simulations were performed to define optimum target and field conditions, which were used to inform mission analysis and vehicle design studies. Concurrently, substantial progress was made in the development of a significantly more accurate 3D physics based simulation, which will be used to further refine the target and field conditions required for sensible fusion gain. Preliminary results of the advanced simulation have demonstrated that liner currents are indeed induced due to rapid target injection into a strong magnetic field, underpinning the fundamental physics of the concept. Using the results of the analytic model, mission analysis has been performed for both Mars and Saturn missions, showing significantly reduced trip times for crewed missions and the capability for substantial cargo delivery supporting sustained exploration. Preliminary vehicle designs have been developed based on estimated parameters for the proposed system, forming a baseline against which more detailed designs will be developed as the modeling results are further refined. The rapid human exploration of destinations within our solar system requires significantly more energetic propulsion systems than current chemical engines or nuclear thermal propulsion can provide. The pulsed fusion propulsion system described in this Phase I report may offer a practical, viable method to achieve the accelerations required for fast interplanetary transits. If successful, the concept will enable a new class of crewed exploration missions less constrained by the frailties of the human physique, opening the solar system to our ever expanding need for human exploration.