#### drewnickel

##### Resident Hybrid Nut

RPA (rocket propulsion analysis) is what I use. The free version (1.2.9) has basically all you'd ever need, version 2 limits the number of propellant components but does nozzle geometry and heat transfer, so I recommend 1.2.9 for the most part. If you mean modeling an entire engine burn, there are a couple hybrid spreadsheets floating around and then HRAP (hybrid rocket analysis program) which I developed and posted to GitHub.Solid Recommendations re Propellant Thermochemistry Modeling Software??

I have, and have worked a bit with, various free and paid 'software' for the thermochemical modeling of various propellant formulations. One example would be ProPep3. Can anyone very heartily recommend software - whether freeware or paid - that they truly feel (or, even better, know!!) is excellent and can be relied upon?