Voltage-Current Characteristics of Self-field Magnetoplasmadynamic Thrusters: Modeling and Application to Lithium Propellant
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Abstract
A non-dimensional voltage-current (V–J) model for self-field magnetoplasmadynamic thrusters (SF-MPDTs) is developed and compared to experimental data from a lithium- fed 30 kW-class thruster. Starting from first principles and incorporating physical scaling for thrust and dissipative sinks, the model yields a closed-form expression for the non- dimensional voltage as a function of the MPDT electromagnetic scaling number, ξ = J/Jci, where Jci is the critical ionization current. The model accounts for ionization, thermal, and electrode losses, and predicts a universal Vb(ξ) relationship valid across operating regimes with no free parameters. Validation using experimental data in the ξ ≤ 1 regime demon- strates agreement down to ξ ≃ 0.25. This universal model enables predictive scaling of SF-MPDT performance and provides a foundation for future analytical and experimental studies, including forthcoming higher-power lithium MPDT testing.