Electrodeless plasma thruster concepts for high-power propulsion systems

For the last decades, there have been a tremendous proliferation of low-power and low-thrust electric propulsion systems, among which Hall Effect, Ion thrusters, and electrosprays have received the most attention. With increasing interest in outer space missions; both scientific and commercial, the needs for high-thrust propulsion systems that are capable of propelling a spacecraft for long duration and distance from Earth has become critical. Currently, the chemical propulsion is the only choice when high thrust level is needed. However, the low specific impulse makes chemical propulsion impossible to propel spacecraft for a long distance due to inefficient propellant utilization. On the other hand, the modern electric propulsion can potentially provide exhaust rate up to 1/3 of the speed of light, which would enable a space travel that is a lot faster and farther away. The key for this high speed is to maintain ultra-low power-to-thrust efficiency, hence resulting a long duration of acceleration for the spacecraft. There are multiple critical physical and engineering problems with modern high-power electric propulsion systems. In case of Hall Effect and Ion thrusters, the problem is the current limitations of cathode-neutralizers, they are still far from meeting the needs for outer space thrust level, let alone their lifecycle. The modern electric propulsion systems are based on the architecture of external power sources, which will have significant power transfer loss at high power that is required for high thrust level. This paper discusses several promising electrodeless plasma thruster concepts for high-power and high-thrust propulsion systems. These concepts are proposed to address limitations and challenges of high-power propulsion systems, enabling new outer space missions that are otherwise not achievable by using conventional thruster architecture.