Astronomy

Sounds like it's related to field emitter arrays. Here's a more detailed article from ESA https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Shaping_the_Future/ATHENA_thruster_kicks_off_electrospray_propulsion_for_NanoSatellites

Salts as thruster fuel, now that’s outside the box.

Nobody expects the Spanish propulsion