Use of nuclear reactors in space

General problems of using nuclear reactors for space exploration and development are considered. Possibilities of nuclear reactor application as spacecraft power supplies and for propulsion are discussed and nuclear power sources are compared with traditional ones (chemical storage batteries, solar cells and radioisotope thermoelectric generators). Safety problems related to nuclear reactor launching to the space are considered as well. It is noted that the nuclear reactor application is promising for two flifght classes: flihts over trajectories far from the Sun, when the solar energy flux decreases markedly, and near-eath orbital and transport flights with large energy consumption. The most perspective space propulsion reactor concepts among those existing at present are nuclear rocket engines with irect heating working medium in the reactor core, nuclear power plant where nuclear energy is converted to electric energy and is used for ionization, heating and acceleration of working medium, as well as nuclear rocket engine using a series of nuclear explosions for propulsion. It is concluded on the basis of safety analysis for space nuclear reactors that, considering the probability of a spacecraft entering the dense atmosphere, it is necessary to use reactors of such structure that gets disintegrated to uninhalable particles upon acrodynamic heating and melting-down