Theoretical Modeling of Multiphysics for CO2 Phase-Change Ejection Power Unit

A multiphysics theoretical framework is presented for CO2 phase-change ejection power units, integrating the GERG-2008 equation of state for multiphase CO2 thermophysical properties with the Jones–Wilkins–Lee (JWL) combustion model through customized Abaqus VUEOS and VHETVAL subroutines. The Coupled Eulerian–Lagrangian (CEL) method resolves the strongly coupled interaction between high-pressure compressible CO2 and solid structures across supercritical, liquid–vapor coexistence, and gaseous phases. Validation against experimental pressure–time measurements demonstrates a maximum relative error below 10% throughout the pressurization trajectory, with peak pressure prediction accuracy of 4.1%. This validated framework offers quantitative design guidance for next-generation cold launch systems, enabling systematic optimization of high-pressure chamber configurations, release pressures, and operational parameters for enhanced energy efficiency and reliable performance in variable deployment environments.