BurnSim
Solid Propellant Internal Ballistics Simulation
Research Rocket Motor Design Software

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8/10/2026 - BurnSim 4.0.0.13: Erosive burning!
BurnSim can now optionally model erosive burning: each grain is sliced along its length and burn rate is augmented near the nozzle end where gas crossflow is highest, instead of a single rate for the whole grain. Two switchable models (Lenoir-Robillard and Mukunda-Paul), off by default so existing motors and sims are unaffected. Also new since the beta launch: a Custom grain type for drawing or importing your own cross-section, and an axial (side-on) motor cross-section view.
Full documentation is on the Wiki, including a dedicated Erosive Burning article.
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
    • 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
  • 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 use of BurnSim version 3.0. For multiple users, volume discounts are available. 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

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