Contactless steering of a plasma jet with a 3D magnetic nozzle

Abstract

A 3D, steerable magnetic nozzle is presented that enables contactless thrust vector control of a plasma jet without any moving parts. The concept represents a substantial simplification over current plasma thruster gimbaled platforms, and requires only a small modification in thrusters that already have a magnetic nozzle. The characteristics of the plasma expansion in the 3D magnetic field and the deflection performance of the device are characterized with a fully-magnetized plasma model, suggesting that thrust deflections of 5-10 deg are readily achievable.

Three dimensional fluid-kinetic model of a magnetically guided plasma jet

“…On the other hand and for the sake of simplicity, it will be assumed that the plasma contains a single ion species of unit charge, hence the quasineutrality condition reduces to n e = n i = n. A steady state will be considered, ∂/∂t = 0, so equation ( 5) yields E = −∇φ, where the electric potential is commensurate with the electron temperature, eφ ∼ T e . No simplifying assumptions will be made regarding the spatial geometry of the system, and a three-dimensional formulation will be maintained, to allow the analysis of non-axisymmetric MNs with thrust vector control [35].…”

“…where bothĥ i and k i are now constant along the magnetic field. Equation (72) provides a relationship between the density and the electric potential on each magnetic line which, coupled to the electric drift-kinetic system ( 27)-( 31), allows to solve the three-dimensional problem one magnetic line at a time [35,36]. In addition to the integration constantsĥ i and k i , the behavior of the plasma solution on each different magnetic line depends only on the variation B( ) of the magnitude of the magnetic field as a function of the arc length along the line, which is given by the chosen nozzle coil configuration.…”

“…1. While most MNs are axisymmetric (and plasma and magnetic tubes are well identified), some applications, such as the magnetic control of the thrust vector [35], are based on MNs with variable 3D shape. The extension of the numerical treatment from the two-dimensional (2D) to a 3D nozzle geometry is not straightforward and requires a careful analysis of the most suitable way to integrate the set of equations.…”

“…Firstly, there is a 2D/3D fullymagnetized and stationary fluid model [36], implemented in the open-source FUMAGNO code [37] with a simple closure relation for the plasma pressures (polytropic or isothermal electrons and quasi-cold ions). The model is useful to analyze the near-region of a divergent MN, where most of the thrust gain takes place, and allowed to demonstrate the feasibility of the magnetic control of the thrust vector with a 3D MN [35]. The model is surprisingly simple, as the fluid equations in the fully-magnetized limit can be integrated along each magnetic line independently.…”

Experimental characterization of a 1 kW Helicon Plasma Thruster

“…by radio-frequency (RF) radiation in the MHz range. Some advantages against other mature devices, such as the Ion Gridded or the Hall Effect Thrusters [6], have been underlined by the Electric Propulsion community [7,8,9]: the lack of electrodes, the flexibility in the propellant choice and throttleability (variable thrust and specific impulse) by tuning its operational parameters, a long lifetime (thanks to the magnetic screening of its walls), and even thrust vectoring [10].…”