Thermally stable materials for caseless ammunition

The use of caseless ammunition offers some advantages compared with conventional ammunition so that lighter, simpler and more powerful weapon systems can be developed. The basic principle of this concept is the use of foamed propellants based on crystalline explosives bonded in energetic reaction polymers. Due to their porous structures they are distinguished by high burning rates. Foamed propellants can be produced by the reaction injection moulding process (RIM). At Fraunhofer ICT a lot of firing tests with caseless ammunition based on foamed propellants in many configurations were successfully performed. It was possible to produce an ammunition system with high performance, e.g. a bullet velocity of about 1050 m/s at chamber pressures of about 4600 bar is reached. A very important feature of the propellant is a high thermal stability of the material. If the self-ignition of the material takes place at lower temperatures (about 160°C) a cook-off may result, i.e. a premature ignition in a hot cartridge chamber. Therefore, in order to find thermally stable ingredients and formulations a lot of investigations by accelerating rate calorimetry (ARC) are performed. In Fig. 1 the results of the ARC-measurements of different energetic materials are shown. Based on these investigations thermally stable formulations of foamed propellants for caseless ammunition can be found