Ion engines are a type of electric propulsion system used in spacecraft. They work by using electricity to accelerate ions, which are charged particles, to create thrust. This method is highly efficient, allowing spacecraft to travel long distances in space with less fuel compared to traditional chemical rockets. These engines produce a small amount of thrust over a long period, making them ideal for deep space missions. For example, the Dawn spacecraft used ion engines to explore the asteroid belt, demonstrating their effectiveness in reaching distant targets while conserving fuel and extending mission duration.