Physics of the high specific impulse alternative low power hybrid ion engine (<i>alphie</i>): Direct thrust measurements and plasma plume kinetics

The Alternative Low Power Ion Engine (alphie) is a high specific impulse plasma thruster different from conventional gridded ion engines (GIEs). It uses only one external cathode and ions electrons flow through the open spaces of its two grids, whereas are transported GIE optics. Ionizing move inward to alphie ionization chamber ions, which neutralized by same cathode, exit along opposite direction. These currents together with voltages applied grids produce self-consistent electric field that accelerates charges. one-dimensional velocity distribution electron energy spectra in collisionless plume studied axial axis symmetry. produces mesothermal non-monotone potential profile populations observed those accelerated low group results charge exchange collisions thruster. Both remain essentially unaltered flow. Conversely, groups merge direction following changes potential. temperatures neutral gas heating inside high-energy ionizing electrons. direct measurement thrusts 0.8–3.5 mN for argon gives 13 900–20 000 s impulses. values might be explained additional contribution thrust remaining non-ionized hot effusion apertures grids.