Python interfaces to cpropep, a project started ~15 years ago by Antoine Lefebvre and Ray Calkins to implement the classic Gordon and McBride chemical equillibrium code in C.
The RocketWorkBench (and hence cpropep) project hasn't seen any activity in close to 15 years and yet I still found myself prefering cpropep over CEA for a number of reasons including accessibility, it's C-heritage (rather than Fortran) and the extensive propellant library distributed with all flavors of PROPEP. Calling it manually from the command line or writing and compiling new C executables for every analysis task is cumbersome to say the least. The goal of this project is to bring cpropep into the 21st century with a clean, useful Python interface.
Today, this module is at v0.1. It is only tested and guaranteed to work on Python 2.7 (something I hope to fix for the next release) and requires the users machine to have a compiler available for installation (also hope to fix for 0.2). Otherwise, it is fairly functional.
Currently the two methods for installing pypropep are pip and from source using setuptools. Pip is recommended.
Not much to it -
pip install pypropep
git clone https://github.com/jonnydyer/pypropep.git
cd pypropep
python setup.py install
Coming soon...
Here is a brief example of how to use pypropep::
>>> import pypropep as ppp
>>> ppp.init()
Loaded 1921 thermo species
Loaded 1030 propellants
>>> o2 = ppp.PROPELLANTS['OXYGEN (GAS)']
>>> ch4 = ppp.PROPELLANTS['METHANE']
>>> sp = ppp.ShiftingPerformance()
>>> OF = 2.8
>>> sp.add_propellants_by_mass([(ch4, 1.0), (o2, OF)])
>>> sp.set_state(P=50., Pe=1.) # Pressure in atm
>>> print sp.performance.cstar # in m/s
1892.82959658
>>> print sp.performance.cf
1.57123484882
>>> print sp.performance.Isp/9.8 # in seconds
303.477533166
>>> print sp.performance.cstar * sp.performance.cf / 9.8 # in seconds
303.477533166
More detailed examples demonstrating the utility of the library are given in the form of two Jupyter notebooks (kindly rendered here by Git!)
There are several things I'd like to add to this module for the v0.2 release including:
- Set up Python Wheels distribution so that installation doesn't require local compiling
- Set up an Anaconda distribution for the module
- Support Python versions other than 2.7 in both test and deployment
- Add Finite Area Contraction-ratio (FAC) support to cpropep library and python interface