At the present stage of space propulsion technology, the only practical propulsion system is a chemical propulsion system and an electric propulsion system, which are based on the expulsion of a mass to induce a momentum thrust. Since the maximum speed is limited by the product of the gas effective exhaust velocity and the natural logarithm of mass ratio, its speed is too slow for the spaceship to achieve the interplanetary travel. Apart from momentum thrust based on momentum conservation law, there is another pressure thrust that is pushed and advanced like a solar sail or light sail.
This paper describes the problems of conventional propulsion theory and introduces space propulsion theory beyond the conventional propulsion. In chapter 2, as a problem of the current space propulsion, we describe the momentum thrust, and then discuss the pressure thrust of a solar sail. In chapter 3, the propulsion theory using pressure thrust based on the mechanical structure of space is introduced: relatively well-considered space drive propulsion as a representative example of field propulsion is explained. In chapter 4, space propulsion physics using astrophysical phenomena such as accretion disk and astrophysical jet around a black hole is discussed.