[AkradantousAdoxastous]

Standard airships use helium in order to be buoyant. And hot air balloons use heat to reduce the density of the air. However, it seems plausible that electrically charging a volume of air would result in it self-repelling leading to increased pressure. If the air is sealed in a balloon, the increased pressure would lead to increased volume and therefore decreased density.

So using a simple spark plug, or any electrostatic generator capable of ionising the air, to ionise the air within a normal balloon will cause it to rise. Hopefully should be easy to test this theory, and if it works it can easily be scaled up to blimps.

Why is this better than a normal dirigible? Because helium is rare, expensive and it leaks.

Reward: This idea is free to use, if it works.