Install

EnSim needs Python 3.10 or newer. The package comes in two sizes.

You want	Command	What it adds
The library and the command line	pip install ensim	NumPy, SciPy, Numba
The desktop application as well	pip install "ensim[gui]"	PyQt6, Matplotlib, PyVista

The library install has no graphical dependencies, so it is safe on servers, in CI and in notebooks. ensim check confirms an installation in a few seconds:

$ ensim check
EnSim 4.0.0
  species                      43
  H2O Cp(1000 K)               41.295 J/(mol K)
  LH2/LOX Tc, O/F 6, 68.9 bar  3483.5 K
  Isp vacuum, eps 40           429.3 s
OK

The chamber temperature in the third line is compared with NASA CEA 3.3.2, which gives 3483.4 K for the same case.

Desktop bundles

Each release on GitHub carries ready-to-run builds that need no Python:

• Windows: a single EnSim-<version>-Windows-x64.exe
• macOS: .dmg images for Apple silicon and for Intel
• Linux: a tar.gz with an EnSim executable

Every file has a .sha256 next to it.

First start

The numerical kernels are compiled the first time they run and cached in your user cache folder (%LOCALAPPDATA%\EnSim\Cache on Windows, ~/Library/Caches/EnSim on macOS, ~/.cache/ensim on Linux). The first calculation after an install takes a second or two longer; later sessions start straight away.

From a checkout

$ git clone https://github.com/SpaceEngineerSS/EnSim.git
$ cd EnSim
$ python -m venv .venv
$ .venv/bin/pip install -e ".[gui,dev]"     # .venv\Scripts\pip on Windows
$ python -m pytest

python main.py starts the desktop application from the source tree.

Optional pieces

• The 3D nozzle viewer uses PyVista and needs working OpenGL. Everything else works without it, and STL export of the nozzle wall does not need it either.
• ENSIM_DISABLE_3D=1 turns the viewer off, for remote desktops whose OpenGL drivers crash.
• Without Numba (for example on a Python version it does not support yet) the same code runs as plain Python, correct but several times slower.