cea

CEA computes the equilibrium composition of mixtures via free-energy minimization, and uses the resulting product concentrations to determine thermodynamic and transport properties. It includes a large database of species with thermodynamic curve-fit data, and can be used for rocket performance, detonation parameters, and shock-wave analysis. Maintained by nasa on GitHub, where it has earned 157 stars from the community.

It's actively developed around cea, combustion, detonation, and is a solid reference for anyone building with these tools.