Applied-Field Topology Effects on the Thrust of an MPDT


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Applied-Field Topology Effects on the Thrust of an MPDT


Abstract

The effects of applied-field topology on the thrust of applied-field magnetoplasmadynamic thrusters are investigated. While it has been previously shown that thrust depends linearly on the anode radius, this radius has not been well-defined, and the prevalence of diverging anodes makes it important to determine which radius should be applied to a thrust calculation. The applied-field topology plays a key role in determining this radius, since the magnetic field can generate a pressure confining the plasma within a certain boundary. Because the gasdynamic pressure pushes against this boundary, this work seeks to determine how the ratio of the two pressures determines the effective anode radius. In order to make this determination, two different applied-field topologies are testedone contoured to the anode, and one which diverges more slowly than the anode. The mass flow rate is varied in order to change the gasdynamic pressure while the parameters affecting the magnetic pressure are held fixed. The resulting change in force on the solenoid, corresponding to the change in the applied-field component thrust, is measured. It is found that the effective anode radius changes by as much as a factor of two when the anode expands more rapidly than the magnetic field, but is nearly constant when the anode is contoured to the magnetic field.