The energy-mass and operational characteristics of a nuclear electrorocket propulsion system based on thermionic reactor-converters largely depend on the parameters of the current converter and the onboard cable network. The decrease of the specific mass of a nuclear electrorocket propulsion system due to the choice of the temperature regime of the current converter and the onboard cable network as well as the frequency of the supply voltage is examined. Investigations have shown that increasing the working temperature of the onboard cable network and current converter makes it possible to decrease the specific mass of the nuclear electrorocket propulsion system by 33–83%, as a result of which the useful load fraction of the spacecraft increases from tens of percent to a factor of 2–3, 1 figure, 6 references.