Abstract <p>Within the framework of the federal project “Development of controlled fusion technologies and innovative plasma technologies”, SRC RF TRINITI JSC is working on the creation of a prototype plasma rocket thruster based on a two-stage quasi-stationary high-current plasma accelerator where the processes of propellant preliminary ionization and final high-speed flow formation are separated. The discharge characteristics of the input ionization chamber were determined when using hydrogen and helium as a propellant in the relevant flow range of 1.5–3 mg per pulse, on the basis of which recommended values of specific energy input in the range of 2.2–2.6 kJ/mg for H₂ and 1.2–1.6 kJ/mg for He were established. The plasma temperature estimation for hydrogen at 0.8 eV is consistent with the measured plasma flow velocity of 16 ± 3 km/s. The conversion coefficient of the input electrical energy into the plasma flow energy was 65% in the entire studied range. The results obtained make it possible to predict the electrical discharge characteristics, cooling requirements and erosion rate for the first stage of a plasma rocket thruster.</p>