**1. Introduction**

This book is an outgrowth of the reality of the limitations of the speeds of chemical rockets. As Tsiolkovsky demonstrated over 100 years ago, the speeds achievable by chemical rockets are, in practice, limited by the exhaust speeds of their thrusters and the energy density of their propellants, because chemical rockets must push all their fuel as they accelerate [1].

Many technologies have been proposed to propel spacecraft faster than can be achieved with chemical rockets: ion propulsion, fusion propulsion, space sails, etc. This chapter is concerned only with matter/anti-matter propulsion. Based on fairly recent experiments conducted at Lawrence-Livermore National Laboratory (LLNL) [2] and the Max Planck Institute for Plasma Physics (MPIPP) [3], matter/anti-matter annihilation appears to be a promising candidate for dramatically exceeding speeds capable by chemical-rocket technologies. Most importantly, it appears that matter/ anti-matter annihilation is a likely propulsion source for generating relativistic speeds in space—speeds that are a significant fraction of the speed of light.

In order to understand the possibilities of matter/anti-matter propulsion, it is necessary to understand: (1) the nature of light, matter, and anti-matter; (2) how light and matter interact; (3) how anti-matter can be generated; and (4) how the generation and annihilation of matter with anti-matter can propel a spacecraft. With these principles established, it is possible, as a theoretical matter, to anticipate the speeds that may be reached using matter/anti-matter propulsion.

The project of realizing matter/anti-matter propulsion is exciting, and the impact of successful development of this technology would be profound. With matter/antimatter propulsion, the nearest stars are within our reach. This chapter is intended to show that the technology necessary for interstellar travel has already been demonstrated in the laboratory.

To the greatest extent possible, this chapter starts with basic concepts and works through to likely theoretical outcomes, with the intention to be readable and understandable for a general audience. It is hoped that scientists and engineers who are well-versed in these basic concepts will, with understanding, tolerate the simplest information provided here.
