Ion Engines are the most exciting new rocket propulsion system since the Chinese invented the rocket about a thousand years ago. Most rocket engines use chemical reactions for power. They combine various gases and liquids to form explosions which push the rocket through space. Chemical rocket engines tend to be powerful but have a short lifetime.
Ion propulsion gets its push from electric fields instead of chemical reactions. Its forces are gentler, but they are so efficient, a mission can last for years before running out of fuel.
Interactives and associated readings unpack how ion propulsion works.
The full story: Ion Propulsion Content Module