BurnSim 3.3.3 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The software lies within Education Tools, more precisely Science Tools. We recommend checking the downloaded files with any free antivirus. The most popular versions of the BurnSim are 3.1 and 2.3. This tool was originally created by BlastZone. Commonly, this program's installer has the following filename: burnsim.exe.
From the developer:
BurnSim is a solid rocket steady-state ballistic simulation software package for the Windows platform. In a nutshell, input your motor, nozzle and propellant characteristics and BurnSim calculates the Kn through the burn and predicts estimated chamber pressure and motor performance.
You may want to check out more software, such as Panel, Avantage BPM Foundation or Adding Machine, which might be related to BurnSim.