Out of curiosity, why not make a chemical rocket that takes a neutrally charged atom and ionizes it (normal plasma thrust based off of this (https://en.m.wikipedia.org/wiki/Ionization_energy) take that negatively charged ion and confine it to a few atoms thick of a stream via magnets (pretty much the inverse of the magnetic nozzle mentioned in the below thread)  and then inject a positively charged fuel for a super heated chemical reaction in addition to the plasma thrust? You could even use the