@romanasul yep, there is a MM patch to enable it for at least the stock ion engine: You could expand it to cover any engine module that uses EC and Xenon though: @PART[*]:HAS[@MODULE[ModuleEngines*]]:HAS[@PROPELLANT[XenonGas],@PROPELLANT[ElectricCharge]]:NEEDS[PersistentThrust]:AFTER[RealismOverhaul] { !MODULE[PersistentEngine],*{} MODULE { name = PersistentEngine } }