Metal Plasma Thruster for Small Satellites

Abstract

This paper describes a metal plasma thruster (MPT) that is suited to nano- and microsatellites. The MPT uses solid metal propellant (hence requires no liquids, gases, flow valves, or flow controls), has no moving parts, generates approximately $5000\mathrm{N}·\mathrm{s}/\mathrm{U}$ , and may be packaged into $½\text{-}\mathrm{U}$ , 1-U, and multiple-U increments. A vacuum arc generates a metal plasma plume that accelerates into space at $6.8\mathrm{km}/\mathrm{s}$ (platinum, Pt) to $30.6\mathrm{km}/\mathrm{s}$ (magnesium, Mg) to generate thrust ($\sim 10\mu \mathrm{N}/\mathrm{W}$ ). The range of specific impulse is from 693 s (Pt) up to 3119 s (Mg). Spacecraft interface is simple: the autonomous MPT requires only a DC input (7–28 V) and a start/stop control pulse from the satellite. The MPT is simpler and more rugged than ion engines and Hall thrusters, which are not easily scaled down in mass and power for $<100\mathrm{kg}$ satellites, and provides superior total impulse per kilogram. The MPT is easier to operate than equivalent-sized alternatives: field emission electric propulsion thruster, xenon gas radiofrequency thruster, and pulsed plasma thruster.