The unstable operating regime of magnetoplasmadynamic (MPD) thrusters commonly known as onset manifests itself with erratic fluctuations of thruster terminal voltage and with the presence of anode spots, which are ultimately ascribable to the action of high conductivity channels emerging from the plasma core and attaching to anode surface. Depending on the anode materials employed, spots can also lead to intense ablation and erosion. Some authors have proposed, but not proved, that the fundamental mechanism behind onset could be the so called current filamentation instability (CFI), a phenomenon known to take place both in astrophysical and laboratory plasmas, which consists in the concentration of the current density pattern in to tiny conduction layers. This hypothesisis specifically investigated in this work by performing a stability analysis of a simple current-carrying plasma configuration and showing that conditions suitable for the development of the CFI and the subsequent azimuthal symmetry breaking can actually exist in MPD thrusters. Some of the results obtained in recent investigations are finally discussed in the light of the present analysis.
Filamentation Instability and Onset in MPD Thrusters
ANDRENUCCI, MARIANO
2010-01-01
Abstract
The unstable operating regime of magnetoplasmadynamic (MPD) thrusters commonly known as onset manifests itself with erratic fluctuations of thruster terminal voltage and with the presence of anode spots, which are ultimately ascribable to the action of high conductivity channels emerging from the plasma core and attaching to anode surface. Depending on the anode materials employed, spots can also lead to intense ablation and erosion. Some authors have proposed, but not proved, that the fundamental mechanism behind onset could be the so called current filamentation instability (CFI), a phenomenon known to take place both in astrophysical and laboratory plasmas, which consists in the concentration of the current density pattern in to tiny conduction layers. This hypothesisis specifically investigated in this work by performing a stability analysis of a simple current-carrying plasma configuration and showing that conditions suitable for the development of the CFI and the subsequent azimuthal symmetry breaking can actually exist in MPD thrusters. Some of the results obtained in recent investigations are finally discussed in the light of the present analysis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
