A Tohoku University researcher has improved the performance of a high-power electrodeless plasma thruster, bringing us closer to deeper space explorations. So far, innovations in terrestrial transportation technologies, such as cars, trains, and aircraft, have propelled historical technologies and industries; now, a similar breakthrough is taking place in space, thanks to electric propulsion technology.
Electric propulsion is a method of propelling a spacecraft that uses electromagnetic fields to accelerate a propellant and generate thrust. Electric propulsion technology has been pioneered by space agencies as the future of space exploration.
Already, several space missions have successfully been completed using electric propulsion devices, such as gridded ion thrusters and Hall thrusters. Solar power is converted into thrust energy when the propellant becomes ionized, i.e., a plasma, and gets accelerated by electromagnetic fields. Yet, the electrodes necessary for these devices limit their lifetime, since they get exposed to and damaged by the plasma, especially at a high-power level.
Applying a cusp-type magnetic field inhibited the energy loss that generally occurs to the plasma source wall. The breakthrough opens the door to advances in high-power space transportation technology.
Takahashi
To circumvent this, scientists have turned to electrodeless plasma thrusters. One such technology harnesses radio frequency (rf) to generate plasma. An antenna emits radio waves into a cylindrical chamber to create plasma, where a magnetic nozzle channels and accelerates the plasma to generate thrust. MN rf plasma thrusters, or helicon thrusters as they are sometimes known, offer simplicity, operational flexibility, and a potentially high thrust-to-power ratio.
However, the conversion efficiency of the rf power to thrust energy has stymied the development of MN rf plasma thrusters. Early experiments yielded conversion rates in the single digits, but more recent studies yielded a more modest result of 20%.
Professor Kazunori Takahashi from Tohoku University’s Department of Electrical Engineering achieved a 30% conversion efficiency in a recent study published in Scientific Reports.
Unlike mature electric propulsion devices, which frequently use xenon gas, which is expensive and difficult to obtain in sufficient quantities, the current 30% efficiency was achieved with argon propellant. This implies that a MN rf plasma thruster would lower the cost and resource load from Earth.
“Applying a cusp-type magnetic field inhibited the energy loss that generally occurs to the plasma source wall,” Takahashi said. “The breakthrough opens the door to advances in high-power space transportation technology.”
