Development of RF Plasma Thruster for Space Enabling Technologies at DLR

Abstract

Neutralizer-free or electroless thruster concept, such as the helicon plasma thruster (HPT) and electroncyclotron-resonance (ECR) thruster, relies on the electromagnetic wave to achieve plasma generation. Eliminating electrode exposure to the plasma provides superior compatibility with alternative propellants such as water or Iodine, offering promising advantages for new space applications. DLR kicked off a development project, Decentralized Energy supplied Electrical Propulsion (DEEP) in 2022, aiming to demonstrate a neutralizer-free EP system on a 12U CubeSat in 2027 to promote future space mobility and sustainability. The concept of HPT is one of the candidates, named ALFVEN thruster, within the scope of the DEEP project. The thrust efficiency of HPT has been significantly improved to nearly 30%, mainly attributed to the improvement of the electric circuitry and the understanding of the plasma dynamics in magnetic nozzles. However, the low-power HPT, i.e., few-hundredwatt class and sub-hundred-watt class, still remains relatively low in performance. One of the possible reasons is the poor power coupling between the antenna and plasma. Thus, besides the mission perspective, the ALFVEN thruster also aims to optimize radio-frequency (RF) power delivery by investigating the coupling mechanism between the antenna and plasma.