In essence, electricity is used in place of a chemical propellant to get a spacecraft moving. The tech is slated to be used in the upcoming Asteroid Redirect missions, which aim to explore the ways we could deflect an asteroid headed to Earth, as well as a manned trip to Mars, scheduled for around 2030.

We've already seen cars start to make the switch to electric, and now our spaceships are going the same way.

Solar panels will be used to generate an electric charge, and the on-board propellant will be ionised using the harvested electricity. These positively charged ions, created by trapping electrons in a magnetic field, are then accelerated out of the ship to provide thrust.

Electric propulsion isn't exactly new – NASA says it's been working on it for more than 50 years – but as with any technology, it needs to be made cost-effective, safe, and stable before it can be used in a mission. By awarding the new three-year contract to Aerojet Rocketdyne, NASA is hoping to to speed along the process.

"Work performed under the contract could potentially increase spaceflight transportation fuel efficiency by 10 times over current chemical propulsion technology and more than double thrust capability compared to current electric propulsion systems," said NASA.

....http://www.sciencealert.com/nasa-pushes-forward-with-its-deep-space-electric-propulsion-system