Аn analytical electrodynamic algorithm has been developed in order to study physical processes and calculate mechanical forces in an ion accelerator. This algorithm is combined with computer simulation of the electromagnetic field and charged particles’ trajectories. Computer models of ion accelerators with surface or contact ionization in the injection region were considered as an example. Ultimately, the created theoretical apparatus makes it possible to evaluate the proposed engineering solutions and diagnostic parameters of electric spacecraft propulsions as well as to compare the applicability of various working agents inside.