HSIM -- An Open Source Simulator for Amateur Nitrous Hybrid Rocket Motors

HSIM Source Code


HSIM is a pair of programs written in C. The simulator takes an input file containing a text description of the motor in a simple, one parameter per line format. It generates a description of the motor and the burn as its output. The report generator takes the simulator output and produces the formatted report. Both are written in C, coded in a style that should be straightforward to read or to port.

HSIM sources are available in two forms. At present this web interface drives version 0.3 of the simulator. The C modules and Makefile can be downloaded as a Zip flie.

HSIM does not run as a standalone program. It depends on the freely available program CPROPEP to simulate combustion. A slightly older version of HSIM, version 0.2, is available as a combined source and binary download. This version includes CPROPEP and can be installed on a windows system as a program that runs from the command prompt. The download also includes the modest documentation.

HSIM 0.2

Full download package. Includes source, binary, CPROPEP, and documentation.

HSIM 0.3 Source-only download. This version is the C code currently running this web site.


Each of the fields names on the input screen to this web interface links to a brief description of that field. In addition, an on-line copy of the documentation distributed with HSIM 0.2 is available here.



HSIM was developed by Steve Daniel.

The physical models for HSIM were developed by Evan Daniel or taken from Sutton's book on rocket engine design.

Fuel regression coefficients come from Tod Moore's HDAS hybrid design assistant.

The chemical data on nitrous oxide comes from the NIST database.

Information on Rocksim 8 file formats came from the very helpful folk at Apogee Components.

Contributing to HSIM


If you would like to contribute to HSIM, whether you have source code changes, measured data, or simply ideas, feel free to contact me, Steve Daniel. My email address is swd in the domain pobox dot com. Evan and I would welcome anything that can make the simulator more useful or more accurate.

The one thing we are most actively seeking is measured data on fuel regression coefficients.

I also read and occasionally contribute to the hybridrocketmotor mailing list. Suggestions sent to that list will likely come to my attention.