BurnSim - Solid Propellant Internal Ballistics Simulation - Research Rocket Motor Design Software

BurnSim
Solid Propellant Internal Ballistics Simulation
Research Rocket Motor Design Software

8/31/2026 - BurnSim 4.0.0.18: Nozzles and altitude!
Ambient pressure can now be entered as an elevation rather than a pressure, and a new "Climbs during the burn" option lets it fall through the burn the way it does on a real flight.
The nozzle's divergence half-angle now applies a real divergence loss to Cf instead of only being drawn in the cross-section, and nozzle efficiency is applied to the momentum term where it belongs.
BurnSim 3's "find best nozzle exit diameter" is back, solving the expansion ratio properly instead of rounding it to a whole number, and it can sweep across a climb rather than answering for one fixed altitude.
Also new: a toolbar of common actions under the menu bar, motor files simulate as soon as you open them, a characterization can be saved back onto the propellant it came from - and BurnSim tells you when a fit doesn't actually reproduce the trace it was fitted to.
On Windows, an available update now installs itself from inside BurnSim.
Details and Download here.

What is BurnSim?

BurnSim is a solid rocket steady-state internal ballistics simulation package for Windows, Linux, and Mac - a rocket motor simulator and solid propellant grain design tool. In a nutshell, you input your motor, nozzle, and propellant characteristics, and BurnSim calculates the Kn through the burn and predicts estimated chamber pressure and motor performance. Once your motor design is in BurnSim, you can tweak parameters such as nozzle diameter or grain core diameter and instantly see how Kn, chamber pressure, and motor thrust are affected. Full data can be exported in CSV format.

Motor designs in BurnSim can be saved and recalled for later use. In addition, test data can be imported and graphed alongside simulation data to compare sims to results. BurnSim allows you to make notes about your propellants and motor designs, all saved in one convenient location.

Once you're happy with the your motor design, BurnSim can then export a .ENG file for use in RockSim, wRasp or other rocket flight simulators. You may also export the data to a text file (comma delimited) for use in virtually any system. You can estimate your motor's performance and rocket's flight before you even cast a grain!

Features

Now cross-platform! Runs on Windows, Linux, and Mac (Linux and Mac support is very new and still in early stages)
Supports the following grain configurations in any number and combination:
- BATES grains with 0-2 restricted ends
- End burning grains (defined as BATES grain with zero diameter core)
- Tablet (uninhibited BATES)
- Moon or Offset Core
- D Grains
- C-Slot
- Finocyl
- Star
- X-Core
- Tapered Core - an end burner with a straight or tapered core drilled part-way or all the way down its axis
- Custom Grains - draw or import your own cross-section (DXF, SVG, raster image, or the built-in shape editor)
Different propellant types can be specified for each grain
Propellant thermochemistry - compute C*, specific heat ratio, and molar mass directly from a propellant's ingredient recipe (ProPEP-style analysis, powered by NASA CEA data), with a searchable, extensible ingredient table
Instantly see a graph of Kn, chamber pressure, thrust, and see how it changes when you change motor attributes.
Graph Mass Flux over the burn, a value that can be used to monitor erosive burning
Erosive burning simulation - optionally slice each grain along its length and model burn rate rising near the nozzle end where crossflow is highest, instead of a single rate for the whole grain (Lenoir-Robillard or Mukunda-Paul models, off by default)
Grain erosion visualization
Import test data and graph it along side simulations
Save your motor designs and propellant characteristics, as well as notes and imported test data
Export predicted motor performance into .eng files for use in Rocksim or wRasp
Export predicted motor performance into .csv files (comma delimited text files) for use Excel or any other program.
Thrust estimations based on nozzle geometry

Can't tell how ya much I've benfited from your new program. Did a lot of mixing the last 2 weeks (over 75 lbs), and every motor I designed with the aide of your BurnSim tool performed as predicted. On one flight I used your .eng import feature for Wrasp, and my predicted altitude of 6281' was off 3 feet per Adept! Ya got a winner there ole buddy, thanks for your hard work. As far as I'm concerned, I still owe ya one....

-Pat Gordzelik
President Tripoli Amarillo, L3CC, TAP

Future Features

Command-line mode - simulate a motor file and export results to CSV without opening the UI, for scripting and batch processing
Pressure drop (burnout or boost-sustain) transient simulation
Your suggestions!

Dont hesitate to contact me at BurnSim@blastzone.org with any bug reports, suggestions or anything at all.

PLEASE NOTE!

BurnSim estimates chamber pressure and performance assuming steady state operation. BurnSim 4 can optionally model erosive burning effects, which can significantly raise chamber pressures in motors with high L/D ratios, but this is off by default - turn it on under Settings if your motor is a candidate for it. Either way, treat all results as estimates, not guarantees. Test all motors in a safe environment, and always assume the motor can fail. Be prepared.

What does it cost?

BurnSim is free to download and try in trial mode. Full features with a time limited license are free for the asking, just contact me.
Education licenses are free for .edu users.

A Personal license for BurnSim is only $39 - unchanged for >15 years! The Personal license entitles one person's personal, non-commercial use of BurnSim. For multiple users, volume discounts are available.
Commercial use requires a separate commercial license - details coming soon. Please contact me for details.

Please download BurnSim and try it out. Thank you for your support, license fees cover the costs of continued development and improvements to BurnSim.

License fees may be purchased with via Paypal, or with a credit card, or check / money order. Please go to the Secure Payment Page to purchase your license.

Where can I download BurnSim?

The download page is here