Annular Engine Development Status

This publication documents the development status of the Annular-Geometry Ion Engine (AGI-Engine). The AGI-Engine is the design core for a new class of electric propulsion thrusters, referred to as the Next-Generation Electric Propulsion Thruster (NGEPT). The NGEPT is a single thruster concept, implementing an annular ring architecture, which potentially can be scaled and adapted for any power level at any specific impulse of interest. The AGI-Engine itself provides a pathway to substantial increases in thrust density (≥ 9 N/m 2 ), power density (≥ 260 kW/m 2 ) and input power (10’s-100’s of kW) relative to conventional ion thrusters, at < 5000 seconds specific impulse. Progress was demonstrated in the maturation of the concept with the design, fabrication, and testing of high-perveance flat annular geometry ion optics electrodes manufactured from pyrolytic graphite. The annular electrodes exhibit high beam collimation and high beam flatness while achieving a span-to-gap ratio of less than 1⁄2 that of the NEXT ion optics with a beam area ~ 97% of that of NEXT. Sufficient data were obtained to support the development of a full-scale highpower Annular Engine of 65 cm diameter with a potential input power capability of 21-62 kW over 2730-4670 seconds Isp.