The invention relates to a method for producing (cryogenic) solid monopropellants which are cooled to below room temperature and are used for rocket drives, especially using heterogeneous liquid-solid propellants wherein at least one of the reactants in the form of an oxidizer or a fuel contains a phase which is liquid or gaseous at normal temperature, for example emulsions of liquid constituents which do not dissolve in each other, suspensions of solid in liquid constituents or liquid-impregnated feed materials. The invention also relates to a cryogenic solid propellant for rocket drives, especially heterogeneous quasi-monopropellant fuel-oxidizer combinations. The aim of the invention is to increase the efficiency of the cryogenic solid propellants compared with conventional storable solid drives, hybrid drives or liquid driving gears, and to improve in a simple manner the storage properties and economic efficiency of said propellants, avoiding costly liquid management, and simultaneously eliminating the permanent ignition of the cryogenic solid propellants. To this end, the at least one liquid or gaseous phase embodied as a reactant in the form of a fuel or an oxidizer is transferred into a solid structure comprising interconnected cavities, said structure consisting of reactants which are formed in such a way that they complement the liquid phase, and the liquid phase is converted into a cryogenic solid phase inside the solid structure by means of freezing, said solid phase being stable below normal temperature.