Applications in space travel

Ion engines provided amazing new opportunities for space travel. They are ten time as efficient as chemical rockets, while at the same time are a great deal smaller. As a result, and because the thrust can be maintained for long periods without the need for huge quantities of fuel, ion-powered spacecraft can be sent on long-distance missions.

These spacecraft are far more economical than standard types, which makes them a more attractive choice for many applications. Lower flight times and energy requirements make ion propulsion excellent for missions to comets, asteroids and both the inner and outer planets.

However, ion-based systems are of no use for missions requiring high acceleration, and are unlikely to be used for short-distance missions (such as to the moon). Additionally, ion engines do not produce enough thrust to leave Earth's atmosphere unaided - a conventional chemical launch system is necessary.

Ion engines have already been used successfully on Deep Space One, but the next likely mission to use them will be the spacecraft Rosetta. The Rosetta is due to rendezvous with comet Wirtanen in 2011: a conventional engine would take 9 years to make the journey, while an ion engine will take only 2.5 years. It could thus return with samples before a conventional craft had even arrived.