Electric blue, that's the colour of NASA's latest high-tech spaceship engine, which uses xenon ions instead of a rocket blast. The stunning blue glow comes from photons released by the ions as they lose energy upon leaving the engine. The solar-electric propulsion thruster ditches burning chemical fuel for xenon ions accelerated by an electric field generated using solar panels. This provides a steady stream of ions that can slowly nudge a spacecraft to high speeds with minimal fuel, making it a good choice for long-range missions
NASA Explains "Since the ions are generated in a region of high positive and the accelerator grid's potential is negative, the ions are attracted toward the accelerator grid and are focused out of the discharge chamber through the apertures, creating thousands of ion jets. The stream of all the ion jets together is called the ion beam. The thrust force is the force that exists between the upstream ions and the accelerator grid. The exhaust velocity of the ions in the beam is based on the voltage applied to the optics".xenon-ion propulsion engine, and instead of using rocket fuel, it harnesses magnetic fields to create thrust
Ion engines will be fuel-efficient and more suited for space travel. And indeed, NASA plans to launch an ion-powered unmanned spacecraft to capture a small asteroid and re-locate it in the moon’s neighborhood. Afterwards, a spacewalking team will get to it via the Orion space capsule currently under development. NASA hopes to retrieve the asteroid in 2019 and explore it in 2021. This is all in preparation of larger, more important missions, including a trip to Mars. In addition, ion engines could be used to power spacecraft capable of redirecting incoming asteroids. Also called a solar-electric ion propulsion engine or Hall effect thruster, it’s powered by an inert and odorless xenon gas.