the plasma ignited chemical fluid discharges through perforations 48 to mix with fuel in the fuel chamber 104 the plasma temperature can be controlled to an extent by the type of material used to form the wall of the capillary 36 specifically when the wall of the capillary 36 is ablated in conjunction with the inner ablative layer 52 during plasma discharge a portion of the wall evaporates unlike the inner ablative layer 52 which evaporates completely the wall of the capillary 36 evaporates partially thereby forming a wall of vaporization arc around the plasma within the capillary 36 the plasma is therefore enclosed by a wall of vaporization arc with a structural integrity to contain the plasma while at the same time ablatively supplying fuel constituents to it accordingly the wall material of capillary 36 can be selected to ablate and evaporate partially at a predetermined rate such that the plasma temperature can be set between 25 000 u00b0 k to 30 000 u00b0 k further the wall material of the capillary 36 can be selected to have chemically reactive constituents compatible with a propellant or oxidizer such as the oxidizer in chamber 94 so that when the plasma ignited chemical fluid discharges through perforations 48 and mixes with for example fuel in the fuel chamber 104.