Super-powerful new ion engine revealed

New Scientist SPACE - Breaking News - Super-powerful new ion engine revealed

Ion engines work by using an electric field to accelerate a beam of positively charged particles – ions – away from the spacecraft, thereby providing propulsion.

The conventional ion engine contains three grids perforated with thousands of millimetre-wide holes. These grids are attached to a chamber containing the charged particles.

The first grid operates at thousands of volts, while the second is kept at a low voltage. This voltage difference creates an electric field, which extracts the ions from the fuel reservoir and accelerates them out into space in one step. The third grid acts to stop electrons flying back into the ion beam.

Ideally, the voltage difference between the first two grids should be as high as possible, to maximise the speed at which the ions are expelled, and also the fuel efficiency of the engine. But when the difference approaches 5000 volts, ions collide with the second grid, and start to erode it.

The new design incorporates four grids. First, the ions are extracted from the reservoir using two closely spaced grids that both operate at an intermediate voltage of 3000 v to 5000 v.

Acceleration comes in the second stage, when the extracted ions are channelled between the second and third grids, across which a very high voltage is applied. The final, low-voltage stage, between the third and fourth grids, prevents electrons from the exhaust plume from flying backwards.