Electric Rockets and Satelite Proplsion

Electrospray Propulsion is a new invention in which research began in the 20th century and eventually two types emerged: "Hall thrusters," and "gridded ion engines."   They are now using liquids to create a third type of propulsion and that was the Electrospray Propulsion which was weak at first although in research and didn't make it past the 1960s and 1970s but finally became the most inadvertent "Propulsion in a bottle," in which electric fields are used to create energy in conductive liquids.  "The propellant is stored within a porous material, which brings the liquid into the thruster's electric field through an array of sharp microstructures on its surface. The porous material which acts as a wick, drawing the propellant out of a reservoir and into the thruster.  The microstructures pre-deform the liquid so the electric field only has to perform at the tips pulling the liquid out further and extracting it a few ions or molecules at a time.  Then, the  extractor (the part that generates the electric field) is made with micro-emitter holes that lie up material.  Its field is designed to extract ions from each tip separately although together." - ([Electric Rockets and the Future of Satellite Propulsion]: Aerospace & Defense Technology, April 2017)