No abstract

In order to realize a long lifetime of an electric propulsion system, we have been investigating various electrodeless electric propulsion concepts utilizing a helicon plasma source. In one of our concepts, helicon plasma is electromagnetically accelerated using a rotating electric field in the presence of a diverging static magnetic field. This acceleration concept is called the Lissajous acceleration. Plasma acceleration experiments have been conducted and plasma acceleration was evaluated using a Mach probe. Although the experiments showed some features of the electromagnetic acceleration, most increment of the plasma velocity is caused by the increment of the electron temperature. The thrust (4.95 μN) did not reach feasible values for real applications, and therefore, it is important to find a better operational condition with the aid of a theoretical thrust model. We have developed a theoretical thrust model which consists of a trajectory analysis and an electric field penetration model in the electrostatic approximation. The model shows that experimental parameters are off from an optimum operational condition which provides the maximum thrust.

Analytical thrust model for the Lissajous Helicon Plasma Accelerator (LHPA) is developed by extending previous works [1,2] in order to guide experiments for achieving feasible value of the thrust. In the LHPA, a rotating transverse electric field in an external divergent magnetic field drives azimuthal currents via electron E × B drift then the thrust is produced due to the Lorentz force. One dimensional (1D) analytical model is developed which includes the electric field penetration into the plasma and the E × B current estimation based on a trajectory analysis. Thrust as a function of parameters of the plasma density and the magnetic field is studied. The penetration of the electrical field into plasmas is examined by 1D particle in cell (PIC) simulations whose results are consistent with those of the 1D analytical model.