CALCULATION OF NONLINEAR DRIFT INSTABILITIES IN MAGNETOPLASMADYNAMIC THRUSTER FLOWS

This paper presents the latest results from calculations of the nonlin ear development of instabilities in magneto-plasmadynamic (MPD) thrust er flows. Linear instability analysis carried out at the Institut fur Raumfahrtsysteme of the Universitat Stuttgart yielded three basic inst abilities for stationary MPD thruster flows: a space charge instabilit y, an acoustic wave instability and an electron drift instability. Non linear analysis using the quasi-analytical method (QAM) developed by t he authors not only yields these instabilities in the lower orders of the QAM hierarchy but also shows their nonlinear evolution in the high er order development, particularly that of the space charge instabilit y which is actually shown to lead to current chopping. Calculation res ults for the normalized current density and electric field strength as functions of time for various relative gradients are presented.