The ionic afterburner was designed by the Syndicate to compensate for the primary weakness of an ordinary afterburner: namely, that it consumes hyperspace fuel at a prodigious rate. Ionic afterburners instead use a small amount of fuel combined with a large burst of energy from your ship's batteries to achieve the same effect.
-Outfitter DescriptionTemplate:Endless Sky - Ionic Afterburner
The Ionic Afterburner burns fuel and energy to give you a speed boost. Possibly developed in response to the New Greenpeace movement's protests against the damaging environmental effect of the Afterburner, or just to make loads of money.
The Ionic Afterburner can be purchased at the following ports: