The possibility of varying at will the rate of burning of solid propellants, after ignition, by the use of electric fields, is considered. Two methods seem possible; varying the normal burning rate and varying the rate of flame spread over surfaces. The latter, which can be used to control the total consumption rate by varying the rate at which 'internal area' can be opened up, is shown to be by far the most promising. Ionic winds can be used to increase it by making the propellant one electrode, or decrease it by using an electrode contacting the flame, in an enclosed system, so as to maintain the propellant surface cool by a flow of entrained air. In simple systems at atmospheric pressure increases of about 200 fold and decreases of approx. 10 fold, with respect to the unperturbed value, are achieved. Theory indicates that larger effects should be possible at the higher pressures relevant to combustion in rockets.