The two of the largest developments in the 20th century have been the invention of spacecraft, and the invention of nuclear power as a source of long lasting energy. Now, both technological fields have grown immensely to structure the technology of our world. These two fields are intertwined, as the future of space exploration depends on the availability of nuclear power. One of the most important requirements of a space flight mission is to be able to fly to furthest reaches of the universe. In fact, flying anywhere in our Solar System besides the moon will pose a considerable challenge as the distances that need to be travelled are great. The various means of chemical propulsion in spacecraft do not have the necessary high specific impulse and velocity to reach these long distances. But, with the availability of nuclear power, spacecrafts will have the thrust and the necessary power for exploration of interstellar distances. Nuclear propulsion poses the way for exploring our solar system and it provides the means for interstellar exploration. You can find contemporary techniques of nuclear space propulsion in this book and advanced futuristic nuclear space propulsion methods.