After a seven year journey, the NASA spacecraft Dawn has returned the first images and data from the mysterious dwarf planet Ceres. The information gathered by the mission will provide new insight into the nature of Ceres, which NASA has described as a time capsule from the dawn of the solar system (this is where the spacecraft gets its name). But the spacecraft itself is newsworthy in its own right as it is the first exploratory space mission to use an electrically-powered ion engine.
Dawn’s ion propulsion system uses xenon gas as a propellant. The system works by using electric power to create charged particles that are electrostatically accelerated to high velocities. The spacecraft is then propelled in the opposite direction. Electrically-powered thrusters are much more fuel efficient than traditional chemical ones, so large amounts of mass can be saved with lighter fuel needed onboard, which significantly reduces the cost of spacecraft. The concept of electric propulsion has existed for more than 50 years, but it is only now beginning to move beyond experimental applications. It is likely that electric spacecraft engines will be used much more frequently in the future, for example, to reduce the cost of deploying satellites.