A new tool has been developed to make use of the MolFlow CLI to simulate the evolution of vacuum systems through an iterative procedure. The Vacuum chamber conditioning and saturation simulation tool (VacuumCOST) consists of a set of Python scripts that repeatedly call MolFlow CLI, each time updating a set of parameters based on the results of the previous simulation.

Pressure simulation following a leak starting at t=72 hours


As part of collaboration with space industry players, we got a feature request to calculate the force and the torque exerted by molecular hits on either individual facets or on an object that consists of multiple facets. This is now implemented in the 2.9.8 beta, released today. It works with both static and time-dependent simulations.

The source of the molecular force is the impulse change of an incoming molecule on the surface of the facet:


courier cover

CERN's quarterly magazine presented space uses of MolFlow+ in its 2022 fall edition. It details the history of the code and collaborations with several space players.


Welcome back!

After nearly 2 years of not being indexed by search engines due to an accidental "noindex" entry in the header, this website is once again appearing in search results.

For those who just found the site, here is a short summary:


A new update for Molflow is out!

Molflow 2.9.0 delivers major improvements to the simulation performance as well as a new secondary application:

The MolflowCLI (Command Line Interface)

Molflow Command Line Interrface

In short this gives the possibility to launch simulations on headless computers or work with custom scripts. All details and a user guide can be found in the corresponding documentation:


With the clang compiler and Homebrew updated for Apple silicon, we could compile Molflow for the new ARM architecture.

molflow mac arm


Following another user request and the wish to compare different configurations more easily, we created a new analysis tool: the Convergence plotter. As it is deeply entangled with the Formula Editor, you can open it directly from there (or via the Tools menu).


3D modeling in CAD programs requires a steep learning curve and expensive software.

Using Molflow's built-in editor to create a sequence of apertures and connect them manually is tiresome.

A helper tool, OpticsBuilder can automate the process: it takes a series of apertures (either parametric shapes like circles, racetracks, or custom imported ones).


2019 had four important changes concerning the future of Molflow:

  • In the beginning of the year, cross-platform support was added. For this, the separation of GUI (mollfow.exe) and the workers (molflowSub.exe) had to be ended, using instead a single binary with multithreading (Mollfow versions 2.7 and later)
  • In late April, the development of Molflow was put on hold, except for minor bugfixes
  • In June, a PhD student in computer science joined the Molflow team
  • In November, the development resumed, with a new build (2.7.9) released the first time in 6 months

As of the end of 2019, our plan is to...


Following user requests, a diagnostic tool has been added to Molflow, providing insight to the behavior of your vacuum system. It can show the dsitribution of the...

  • number of bounces
  • flight distance
  • flight time

...of test particles until they are pumped:

2019-04-08 08_41_28-Window.png