The concept and feasibility study of multimode acceleration coaxial (MAC) thruster

A multimode propulsion concept, termed the Multimode Acceleration Coaxial (MAC) thruster, is proposed for in-space servicing, assembly, and manufacturing (ISAM) missions. These missions require three key capabilities: high impulsive thrust for proximity operations, high specific impulse for orbit maneuvers, and electrostatic discharge (ESD) mitigation for safe docking. The MAC thruster adopts a coaxial architecture consisting of a “nozzled” hollow cathode, an annular discharge channel, and magnetic circuits. The key novelty lies in the integration of Hall, CC discharge, and gas-jet modes within a single device, enabled by the dual use of the hollow cathode as both a neutralizer and a high-flow-rate propellant injector. A breadboard model (BBM), developed based on the ν800 JAXA 1 kW-class Hall thruster technology, was experimentally investigated, achieving a specific impulse of up to 1620 s and a thrust exceeding 0.5 N. The results demonstrate that each operating mode exhibits distinct performance characteristics tailored to corresponding ISAM mission requirements, highlighting the capability of a single thruster to operate across a wide operational envelope. It is thus demonstrated that the MAC thruster provides an integrated propulsion solution with shared propellant, enabling enhanced mission flexibility while reducing spacecraft system complexity in future ISAM applications.