A method is provided for solid-propellant engines to be dismantled safely and in accordance with environmental standards having been scrapped. For each engine to be dismantled, it is mounted on a static test rig, immersed in a tank filled with water and started such that propellant is used up under the water. The soluble part of the combustion products (gases or condensates) thus remains trapped in the water in the tank while the non-soluble solid products drop to the bottom of the tank. The body of the engine emptied of its fuel in this way and rendered pyrotechnically inert is then taken apart or disassembled. Periodically, the water in the tank is withdrawn and the tank stripped of its deposits such that subsequent dismantling operations can be carried out under proper conditions. All of the combustion products recovered are sent to appropriate reprocessing plants. The method allows high dismantling rates.