HOW DOES NASA’S EVOLUTIONARY XENON THRUSTER (NEXT) WORK?
NEXT is a solar-electric engine, commonly known as an ‘ion engine’. Like all engines of this type, it uses electricity harvested by solar cells to ionise atoms of a propellant – in this case the unreactive gas xenon. The ionisation process uses a strong electric field to strip away electrons from the xenon atoms, leaving them with an overall positive charge. The electrons are then expelled from the thruster by repulsion from a positively charged ‘accelerator grid’. As gas escapes from the rear, the thruster is pushed forward by a balancing force. The forces involved are tiny compared to those produced in conventional rockets, but the process is extremely efficient and the thrust can be sustained for years rather than minutes.