Voltage-current characteristics of self-field magnetoplasmadynamic thrusters: modeling and application to lithium propellant

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 V(ξ) relationship valid across operating regimes with no free parameters. Validation using experimental data in the ξ ≤ 1 regime demonstrates 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.