Reconnecting Plasmoid Propulsion

Author: Fatima Ebrahimi

Description: A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The magnetic reconnection process here converts magnetic energy of the applied fields to kinetic energy of the plasmoids, accelerating them to a velocity of tens to hundreds of km/s, adjustable by varying the magnetic fields strength. Our novel electromagnetic thruster concept, the Alfvenic reconnecting plasmoid thruster has been shown to produce an exhaust velocity in the range of 20 to 500 km/s controlled by the coil currents in our first sets of three-dimensional simulations. The plasmoids carry large momentum, leading to a thruster design capable of producing thrusts from tenths to tens of newtons. The optimal parameter range for this new thruster is expected to be ISP (specific impulse) from 2,000 to 50,000 s, power from 0.1 to 10 MW and thrust from 1 to 100 N. It would thus occupy a complementary part of parameter space with little overlap with existing thrusters, and be suitable for long-distance travel with high Delta-v, including the solar system beyond the Moon and Mars. Because the Alfvenic plasmoid thruster can use a wide range of gases as fuel, it will be ideal for asteroid mining, since, for example, hydrogen could be extracted from asteroids. The next steps include performing more detailed computer simulations to both develop a reduced size (50 kW or less) solar-powered thruster version, more suitable for lab testing and with more near-term commercial viability, as well as a larger (tens of MW) fission-powered version.