NASA is testing ion thrusters for Mars missions which use electricity to emit a gas-cloud of charged particles. The X3 thruster generated 5.4 Newtons thrust, breaking the previous record of 3.3 Newtons for electric field-propelled thrusters. Operating at 102 kilowatts power, it can propel spacecraft to 40 km/second with 10 times better mileage than chemical-powered rockets which reach 5 km/second.