Cpropep is a propellant evaluation software that will let you compute rocket motor performance in function of the propellant. It works like the known software `propep' but is code in standard C, is in development and is supported. There is more information about this project on the Rocket Workbench home page.
Cpropep can compute chemical equilibrium for a fixed temperature and pressure points, adiabatic flame temperature, frozen and shifting equilibrium rocket performance evaluation.