A solid propellant boost generator for generating a boost regime comprising two boost pulses separated by a time interval ΔT, said boost generator comprising: - a rigid structure comprising a booster body formed by a side wall, a closed end and a free end typically terminated by a nozzle; - two solid propellant charges (66, 67) successively poured into said booster body and moulded so as to form two nested coaxial tubular elements, separated by a flexible partition (64, 65) made of a combustion inhibitor material and respectively delimiting a first central channel and a second central channel; - a first and a second combustion initiator element capable of successively igniting said first and then said second charge on command, characterised in that: - said first combustion initiator element is arranged in contact with said first charge so as to initiate the combustion of said first charge via a surface S 1 delimiting said first central channel; - said second combustion initiator element is arranged in contact with said second charge so as to initiate the combustion of said second charge via a surface S2 delimiting said second central channel formed after the combustion of said first charge; said second combustion initiator element being positioned behind said flexible partition (64, 65) so as to be in contact with said second charge; - said flexible partition (64, 65) conforms to the shape of the contact surface between said second charge and said first charge and adheres at least to said second charge; said flexible partition (64, 65) being configured so that a pressure increase generated by the combustion of said second charge initiated via said surface S2 by means of said second combustion initiator element causes part of said flexible partition facing said second central channel to detach and said partition to fracture, which releases the combustion gases inside said second central channel. - a rigid structure comprising a booster body formed by a side wall, a closed end and a free end typically terminated by a nozzle; - two solid propellant charges (66, 67) successively poured into said booster body and moulded so as to form two nested coaxial tubular elements, separated by a flexible partition (64, 65) made of a combustion inhibitor material and respectively delimiting a first central channel and a second central channel; - a first and a second combustion initiator element capable of successively igniting said first and then said second charge on command, characterised in that: - said first combustion initiator element is arranged in contact with said first charge so as to initiate the combustion of said first charge via a surface S 1 delimiting said first central channel; - said second combustion initiator element is arranged in contact with said second charge so as to initiate the combustion of said second charge via a surface S2 delimiting said second central channel formed after the combustion of said first charge; said second combustion initiator element being positioned behind said flexible partition (64, 65) so as to be in contact with said second charge; - said flexible partition (64, 65) conforms to the shape of the contact surface between said second charge and said first charge and adheres at least to said second charge; said flexible partition (64, 65) being configured so that a pressure increase generated by the combustion of said second charge initiated via said surface S2 by means of said second combustion initiator element causes part of said flexible partition facing said second central channel to detach and said partition to fracture, which releases the combustion gases inside said second central channel.