In space power propulsion systems (SPPS) based on a low-voltage power source and high-voltage electric rocket thrusters, a current conversion system (CCS) is required. As one of the elements of promising high–temperature CCS, high-temperature plasma thermal emission valves (HPTV) of plasma electric power industry are considered – grid key elements (GKE) and high-voltage plasma thermal emission diodes (HVPTD). In the work, the modeling of the energy-mass characteristics of the CCS built on the GKE and HVPTD using heat pipes (HP) for cooling is carried out, the temperature conditions in which the minimum specific mass of the current converter is achieved are determined. The specific gravity values are determined. The results of the work can be used in the development of new high-temperature CCS space power propulsion systems for electrical power from tens to thousands of kilowatts.