High Thrust Efficiency MPD Thruster

Period of Performance: 01/01/2011 - 12/31/2011


Phase 1 SBIR

Recipient Firm

Tethers Unlimited, Inc.
11711 N. Creek Pkwy S., Suite D113 Array
Bothell, WA 98011
Principal Investigator


Magnetoplasmadynamic (MPD) thrusters can provide the high-specific impulse, high-power propulsion required to support human and robotic exploration missions to the asteroids, Moon, Mars, and the outer planets. MPD thrusters, however, have traditionally been plagued by poor thrust efficiencies due primarily to power lost into the anode caused by the Hall effect. We propose to combine three innovative techniques to create a high thrust efficiency MPD thruster. The first is an unconventional applied magnetic field geometry that counter the Hall effect near the anode surface, the second is shaping of the electrodes to optimize current uniformity, and the third is "through-anode" propellant injection to prevent depletion of the anode plasma. In prior experiments we demonstrated elimination of the anode fall using these novel magnetic fields, and in recent simulation efforts we developed novel magnetic nozzle designs that succeed in counteracting the current concentrations and plasma starvation effects that cause the anode fall. These magnetic nozzles also showed the ability to increase the amount of axial thrust extracted from the accelerated plasma by over 50%. In the Phase I, we will test the effect of a prototype 'optimized' magnetic nozzle on the thrust efficiency of a MPD thruster; both the magnetic nozzle prototype and thruster test article are already constructed. Additionally, we will develop technology for through-anode propellant injection, and evaluate its performance through tests and simulations.