High Thrust-to-Power Electric Propulsion through Neutral Entrainment

ABSTRACT: State of the art Orbital Transfer Vehicle systems and GEO transfer missions require the demanding combined requirements of both high Thrust-to-Power (greater than 150 mN/kW) and high specific impulse (greater than 3000 s), all at constant power. The 9 kW PROTEAN system is a two-stage plasmoid thruster which adds secondary Neutral Entrainment (NE) to the ElectroMagnetic Plasmoid Thruster (EMPT) to dramatically increases the total Thrust-to-Power. This NE stage injects neutral propellant into the plasma path, which are accelerated to high velocity through resonant charge exchange collisions. The NE stage then highly efficiently adds kinetic energy to the engorged plasmoid through Peristaltic Dynamic Acceleration, in which sequenced magnetic coils provide a large magnetic pressure gradient. In total, this system allows for very efficient acceleration of a plasmoid as well as the addition of active propellant mass, all without significant further ionization or plasma frozen flow losses. By simply varying the secondary propellant input flow rate, thrust and specific impulse can be dynamically varied at constant input power and without affecting the initial plasma formation. PROTEAN is therefore a thruster system with less than 5 eV/ion plasma frozen flow losses and can provide mission designers an almost infinitely variable Isp and thrust range. BENEFIT: The PROTEAN thruster system will be able to provide greater than 150 mN/kW and operate from 800-5000 s specific impulse. Additionally, this system will be lightweight (a specific power of greater than 1 kW/kg) and be able to operate at constant power across a wide range of specific impulse conditions. This thruster will have the ability to operate with lower than 5 eV/ion, dramatically less than any Electric Propulsion system in existence. These combined abilities yield a thruster system that has numerous mission benefits and, thus, commercial benefits. The 9 kW PROTEAN operating on Xenon would enable wide-ranging Orbital Transfer Vehicles and GEO/GTO orbit raising missions. A PROTEAN system operating on lightweight or chemically reactive gases would truly allow for high thrust-to-power multi-mode operation. For non-DOD missions, the ability to efficiently use In-Situ Resources has tremendous benefits to interplanetary missions.