Solar-electric propulsion thruster. Cutting-edge solar-electric propulsion thruster during testing. Ion thrusters are a form of electrically powered spacecraft propulsion system that create thrust by accelerating ions. This solar-powered ion thruster uses xenon ions for propulsion. An ion thruster produces small levels of thrust relative to chemical thrusters, but does so at higher specific impulse (or higher exhaust velocities), which means that it has a fuel efficiency of 10-12 times greater than a chemical thruster. The higher the rocket's specific impulse (fuel efficiency), the farther the spacecraft can go with a given amount of fuel. This engine is being considered as part of the Asteroid Initiative, a proposal to robotically capture a small