Ion Thruster

Ion Thrusters are one of the predominant forms of spacecraft propulsion in the solar system. They use electricity to accelerate a gas propellant, and propel a spacecraft forward in space. Due to their relatively low thrust, ion thrusters are not used for travel from the surface of a celestial body into orbit.

Types
There are two types of ion thruster commonly used:
 * Hall Effect Thruster - These are smaller, lower thrust devices which are used to maintain the orientation of spacecraft, rather than as a primary form of propulsion. Hall Effect Thrusters are also used as a means to "spin up" spacecraft which rely on centrifugal force to generate artificial gravity. One such example is on Avalon, the luxury community in lunar orbit.
 * Gridded Ion Thruster - These are larger, higher thrust devices which are used as primary means of propulsion for crafts which remain in space.

Propellant
Ion Thrusters use one of two propellants. about 90% of ion thrusters use xenon, with the other 10% using krypton. A krypton thruster can use xenon (at much lower efficiency), but a xenon thruster cannot use krypton as a propellant.

Due to the high prevalence of ion thrusters throughout the solar system, and due to the high cost of extracting xenon from the atmosphere of earth, xenon production and shipping are a major point of conflict in the solar system. There is a slightly higher than average concentration of Xenon in the atmosphere of Jupiter. The ability to mine and sell xenon in the Jovian system is one of the main paths towards independence for the United Systems of Jovia.