Experimental and numerical study on high-pressure CO2 assisted high-speed launch of large mass projectiles

• An internal ballistic model for CO 2 cold launch was constructed. • 650 kg projectile CO 2 cold launch test was conducted, and the launch velocity was 109 m/s. • A CFD model was established to analyze the internal flow field during the launch process. • Analysis of cold launch impact parameters was conducted. Cold launch systems require environmentally friendly, safe, and energy-efficient propulsion methods to meet modern operational demands. High-pressure CO 2 expansion presents a promising alternative due to its significant volume expansion, environmental compatibility, and high energy density. In this work, a CO 2 phase transition driven launch system was proposed and a comprehensive theoretical and CFD model were developed. Firstly, a MATLAB-based zero-dimensional model is built to predict system behavior. Then, a launch system is constructed and high-speed launch tests are successfully performed. Launch velocity of 109 m/s is achieved for a 650 kg projectile, with a maximum cylinder pressure of 5.06 MPa. The experimental results agree well with numerical predictions, with pressure and velocity errors of only 0.98% and 2.34%, respectively. Furthermore, a computational fluid dynamics (CFD) system is established. The simulation results further verify the correctness of experimental system and theoretical model. The pressure error is only 0.59%, and the launch speed error is 1.60%. In addition, parametric analysis based on the zero-dimensional model shows that projectile mass and CO 2 mass significantly affect the pressure and launch velocity. The preliminary chamber volume has a minor effect on the launch velocity but a notable influence on the cylinder pressure. Reducing the preliminary chamber volume from 75 L to 60 L increases the launch velocity by 0.18% and decreases the maximum pressure by 1.78%. In conclusion, this study pioneers the use of a phase transition unit as the core propulsion mechanism in a CO 2 phase transition driven projectile system and provides a reference for future large‑scale launch studies.