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Conceptual problems of development of two-mode multi-cell thermionic fuel element (TFE) for nuclear electric power and propulsion system are considered. The results of analysis of the design and TFE output parameters are presented. It is shown that application of advanced high effective materials and technologies provides operating of the TFE in two modes: a) in nominal mode of power generation for power supply of spacecraft payload at operational orbit and b) in forced mode of power generation for power supply of electric thrusters under spacecraft orbit transfer from intermediate to operational one.

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.

Choice of unified optimal radial dimensions for thermionic fuel elements (TFE) is considered for the use of TFE with five‐layer collector assembly in in‐core thermionic reactors (ITR) on thermal and fast neutrons of space nuclear power systems (SNPS) with long (no less 5 years) lifetime and ITR electric power in the range from 30 to 300 kW. A series of optimum conditions has considered taking into account ITR core volume, given values for area of ITR emission surface and ItR effective multiplication factor, characteristics of core structure (average moderator portion in core of ITR on thermal neutrons, fuel pin porosity, coolant portion in core and so on), TFE hookup in thermionic generator and so on.On the base of analysis of these conditions the conclusion has made that in aforesaid range of ITR electric power the TFE optimal radial dimensions unified for use in ITR on both thermal and fast neutrons is in the range: TFE external diameter is from 22 to 25 mm, fuel diameter from 15, 5 to 17,5 mm. Under greater electric power the to lesser radial dimensions is expedient.

The paper considers the concept of power propulsion systems‐universal space platforms (USPs) on the basis of second‐generation thermionic nuclear power system (NPSs) and stationary plasma electric thrusters (SPETs). The composition and the principles of layout of such a system, based on a thermionic NPS with a continuous power of up to 30 kWe allowing power augmentation by a factor of 2–2.5 as long as during a year, as well as SPETs with a specific impulse of at least 20 km/s and a propulsion efficiency of 0.6–0.7 are discussed. The layouts and the basic parameters are presented for a power propulsion system ensuring cargo transportation from an initial radiation‐safe 800 km high orbit into a geostationary one using the ‘‘Zenit’’ and ‘‘Proton’’ launch systems for injection into an initial orbit. It is shown that the mass of mission‐oriented equipment in the geostationary orbit in the cases under consideration ranges from 2500 to 5500 kg on condition that the flight time is not longer than a year.The power...

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 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.