Solid propellant internal ballistics
Design the motor. See the results.
Enter the motor, nozzle and propellant. BurnSim computes Kn through the burn and predicts chamber pressure and thrust — rigorous enough for research and professional work, direct enough to learn a first motor on.
- Total impulse
- 76,652 N·s
- Burn time
- 25.01 s
- Peak pressure
- 689 psi
- Peak thrust
- 1408.5 lbf
- Designation
- P‑3066
Latest news
BurnSim 4.0.0.23: BurnSim opens normally on macOS, plus undo/redo and snapshots
The Mac app is now signed with an Apple Developer ID and notarized by Apple, on both Apple
Silicon and Intel. Unzip it, drag BurnSim to Applications and double-click — no Terminal
step and no xattr command. Earlier Mac downloads needed one; this one does not.
Also new: undo and redo under a new Edit menu, and named snapshots that save the
whole state of a motor inside the .bsx file, so they come back when you reopen it and
travel with the motor if you send it to someone. Pressure-linked throat erosion and slag
model the throat growing as the motor runs and slag narrowing it at low pressure, and openMotor
.ric import now converts those coefficients instead of dropping them.
A free 5-day trial is now available from the activation window, so BurnSim can be evaluated before buying. Download 4.0.0.23.
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. 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, or to .eng for RockSim and wRasp.
Grain geometries
Plus Tablet and Tapered Finocyl, and BATES grains with 0‑2 restricted ends. Any number and combination in one motor, each grain with its own propellant. See Grain Types on the wiki.
Features
- Instantly see a graph of Kn, chamber pressure and thrust, and how it changes when you change motor attributes.
- Import test data and graph it alongside simulations.
- Grain erosion visualization, including an interactive 3-D view — orbit, zoom and pan every grain type as a solid, slice it open with a cutaway plane, and scrub a burn-depth slider back through the burn to watch the surface burn back.
- Save your motor designs and propellant characteristics, as well as notes and imported test data.
- Export predicted motor performance to
.engfiles for RockSim or wRasp, or to CSV for Excel and anything else. - Thrust estimations based on nozzle geometry.
- Propellant thermochemistry — compute C*, specific heat ratio and molar mass directly from a propellant's ingredient recipe, instead of running an external tool and copying numbers across (ProPEP-style analysis, powered by NASA CEA data), with a searchable, extensible ingredient table whose every built-in value is checked against a published second source. The equilibrium solver and rocket driver are validated against seven of NASA's own published RP‑1311 reference cases, agreeing to within 0.5 K on flame temperature and 1 m/s on C* — see Accuracy and Validation for which cases, how BurnSim compares to ProPep3, and which numbers no calculation can give you.
- 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, Mukunda-Paul or Ma (2020) models, off by default).
- Custom grains — draw or import your own cross-section (DXF, SVG, raster image, or the built-in shape editor).
- Graph mass flux over the burn, a value that can be used to monitor erosive burning.
- Batch and command-line mode — simulate a motor file and export results to CSV without opening the UI, for scripting and sweeps.
BurnSimCLI.exeruns from a console and returns when the run is finished, so a script can wait for it and read its exit code — see Batch Mode. - Cross-platform — runs on Windows, Linux and Mac (Linux and Mac support is very new and still in early stages).
Future features
- Ignition transient simulation — chamber filling and the pressure rise from ignition up to steady state, rather than assuming the motor starts at its equilibrium pressure.
- Igniters — define, save and reuse igniters, and model what they contribute to that start-up.
- Pressure drop (burnout or boost-sustain) transient simulation.
- Your suggestions! Don't hesitate to contact us at burnsim@burnsim.com 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. For what the results are checked against and where the limits are, see Accuracy and Validation.
What does it cost?
Free to try
The full program for 5 days, so you can evaluate it on a real design. Request the trial from the activation window the first time you run BurnSim — nothing to ask for and no waiting. Every feature works and there is no limit on simulations; a trial just cannot save motor files, export, print or run batch mode.
$49 personal
A license entitles one person's personal, non-commercial use of BurnSim, on up to five computers at a time. Your BurnSim 3 license carries over. Purchase.
$149 commercial
The same license, for business and professional use — one named user, up to five computers at a time. Purchase.
Free for .edu
Student and education licenses are issued automatically to anyone with a .edu email address. No purchase required.
Where can I download BurnSim?
From the download page — installers and portable builds for Windows, Mac and Linux, plus the full change history.
“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