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Power-generation and propulsion complexes for spacecraft, universal space platforms (US) which combine a power unit and high- and low-thrust propulsion unions, make it possible to efficiently solve problems involved in creating satellite communication systems, environmental monitoring systems, industrial technology platforms, interorbital shuttles, etc. Electrical power consumed by prospective spacecraft designed for communication or environmental monitoring may be as high as 20-30 kW. Manufacturing of semiconductors and biological materials in space may require electrical power of 30-l00 kW in the coming decades. The power required to transport loads between orbits using ion-plasma jet engines will amount to tens to hundreds of kilowatts. For all these missions, nuclear power units have important advantages over solar photoelectric power units in their mass, size, cost, and performance characteristics. There is a good reason to consider the use of thermoelectric Nuclear Power Generators (NPG) for USPs due to their small bulk, their capacity for generating greatly increased power in the high-power mode during 15-20% of the total length of the mission, and minimal disturbance of the motion of the spacecraft.

In the report the principles of nuclear power and propulsion complex (NPPC) construction are presented. NPPC considered can ensure the time of spacecraft transfer to geostationary orbit (GSO) within 1 year under electric power level no less than 40 kW at prolonged nominal mode on GSO for spacecraft loads feeding. The main power and mass and dimension performances of such NPPC are summarized. Analysis of relationship between spacedraft mass, its mission payload and transfer time also and a number of main NPPC parameters is performed. The conclusion is made about considerable promises of the NPPC for creating future satellite multi‐purpose systems by using PROTON‐ and TITAN‐class launch vehicles.

One of the important future space technologies is the space production of semiconductive substances, composite materials, medical preparations and so on. Required for this electric power will equal 20–50 kW in nearest ten‐year period with further increasing to one hundred and more kilowatt. For similar production spacecrafts the application of thermionic space nuclear power (SNPS) can be perspective because these systems have a number of important advantages as compared with solar systems for spacecrafts of this type. The possible application concepts of thermionic SNPS with electric power 25 to 30 kW production spacecrafts are considered including the next versions: automatic loading and unloading of raw materials and products; loading and unloading executed by cosmonauts when SNPS being as a part of spacecraft and its demating from spacecraft during the process fulfillment; remote power transmission for power supply of production spacecrafts. It is shown that all considered versions thermionic SNPS can provide power supply of production spacecrafts with satisfying necessary operation requirements.

Control algorithms for ‘‘Topaz’’ type thermionic space nuclear power systems (SNPS) of second generation with electrical power up to 100 kW are considered. These algorithms are based on results obtained under creation of ‘‘Topaz’’ SNPS in ground and flight conditions and develop directly control principles of that SNPS. The most general demands for SNPS under start‐up and nominal modes taking into account of limitations necessary for security of prolonged lifetime are given. These demands must include the security of nuclear and radiation safety under possible emergency situations with SNPS and spacecraft. Control algorithms answering to these demands to a high degree are formulated. Therefore these algorithms can be considered as the most expedient for thermionic SNPS. In particular it is shown that duration of start‐up mode for thermionic SNPS will be equal from 1.5 to 2 hours. The specific values of parameters for these algorithms must be optimized in each concrete case.

For long lifetime space nuclear power system (SNPS) of second generation the cesium vapor supply systems must be applied which differ on principle from system used for ‘‘Topaz’’ SNPS. The main differences are multiple usage of cesium, weak dependence of system mass and dimensions upon SNPS lifetime, essential increase of effectiveness for impurity gas removal from interelectrode gap (IEG) of thermionic fuel element (TFE). Possible schemes of cesium vapor supply systems with its multiple usage are considered. These schemes include one‐side and two‐side diffusion of impurity gases from IEG, combination of diffusion with vapor pumping through IEG. The estimates of supply system effectiveness relative to removal of impurity gases from IEG and its comparison by that criterion are given. It is shown that for long lifetime SNPS it is necessary to use regenerative supply systems with cesium vapor flowrates up to several hundreds grams per day. The selection of the most expedient supply system scheme and its parameters are determined by TFE type and gas discharge into IEG.

The region of expedient using of SNPS with in‐core thermal thermionic reactor (ITR) is limited by electric power level of about 100 kWe under SNPS lifetime from 3 to 5 years. At the same time the reactor power may be forced from two to three times during the period of about half a year. The mathematical model of SNPS mass dependence on a degree of forcing is given. The results of calculation of payload masses and transfer times for transfer from low orbit to geostationary orbit for two thermal reactors having emission area 1.6 m2 and 2.5 m2 are given for different types of electrojets.

The basic operating regimes of space nuclear power system (SNPS) ‘‘Topaz’’ are considered. These regimes include: prelaunch preparation and launch into working orbit, SNPS start‐up to obtain desired electric power, nominal regime, SNPS shutdown. The main requirements for SNPS at different regimes are given, and the control algorithms providing these requirements are described. The control algorithms were chosen on the basis of theoretical studies and ground power tests of the SNPS prototypes. ‘‘Topaz’’ successful ground and flight tests allow to conclude that for SNPS of this type control algorithm providing required thermal state of cesium vapor supply system and excluding any possibility of discharge processes in current conducting elements is the most expedient at the start‐up regime. At the nominal regime required electric power should be provided by maintenance of reactor current and fast‐acting voltage regulator utilization. The limitation of the outlet coolant temperature should be foreseen also.

The electric power of thermionic SNPS with thermal reactor is limited to about 100 kWe under lifetime of 5 or more years. The possible conceptual designs of this thermionic SNPS and its basic units are described. The mass optimization had carried out for different SNPS conceptual designs and permissible levels of ionizing radiation. The optimal lengths from the core center to the user interface module plane had defined. The dependence of specific mass of this optimized SNPS on the electric power in the range from 15 to 60 kWe under permissible radiation dozes from 105 to 106 rad are given.