Fusion Propulsion

Abstract

Next to antimatter annihilation reactions, fusion nuclear reactions produce more energy per unit mass than other energy sources considered suitable for space propulsion. The mass converted to energy in fusion reactions is almost an order of magnitude larger than that in fission reactions, and several orders of magnitude larger than chemical reactions. The fusion fuel, which can also serve as a propellant, must, however, be heated to very high temperatures, comparable to those inside the sun, in order to achieve ignition, and for the reactions to become self sustaining. At such temperatures the fusion fuel becomes ionized consisting of unbound, freely moving charged particles, namely electrons and ions often referred to as “plasma.” In order to produce energy exceeding that required to heat it to ignition, the plasma must be confined long enough to allow the ions to undergo fusion reactions. Such confinement is generally achieved in one of two ways, “magnetic” or “inertial.” Both of these approaches have been investigated for utilization in space propulsion. In what follows, the underlying principles of the use of fusion energy in space propulsion will be examined, and some representative concepts of both confinement approaches will be addressed.