Personal
Noncommercial work by one named user: personal projects, coursework, hobby builds, and student members of university teams.
$10per month
or $99 per year
Buy Personal, $10/monthRPL Engine Workbench 2.0 · Windows 11 and Apple silicon Mac
Rocket engine, motor and vehicle design software
Engine Workbench is a desktop application. Version 2.0 sizes pressure-fed liquid engines and solid and hybrid motors, flies the vehicle you build around them, and solves the flow in the motor and around the vehicle. The calculations run on your computer and the project files stay there.
Personal $10/month · Business $29/month
30-day free trial with no account or license key
Watch a complete worked caseOpen your first example
The Mac app is signed and notarized. The Windows installer is not code-signed, so Windows asks you to confirm the first launch. Outputs are preliminary design data, not flight-qualification data.
What the application covers
One project holds the engine or motor, the vehicle and the flow solutions, so the flight and the CFD use the motor you solved. Each section has its own page.
- Liquid engines
- Operating point, injector, feed system, bell, conical and TIC nozzles, and test-data reduction for pressure-fed engines.
- Solid motors
- Grain burnback for BATES, star, finocyl, moon, C-slot, slotted and custom ports; chamber pressure and thrust; ignition and tail-off; erosive-burning screening; case check;
.engexport. - Hybrid motors
- Nitrous oxide blowdown, regulated oxygen, pressurized and constant-flow feeds; published regression laws with their sources; O/F shift and tank pressure through the burn.
- Vehicle and flight
- Barrowman stability, drag through Mach number, wind aloft, dual-deployment recovery, two stages, dispersion, loads, fin flutter, and build drawings.
- CFD
- Port and nozzle flow at any instant of the burn, nozzle and plume, and the air over the vehicle, axisymmetric or in 3-D with fins and jet; videos of the burn, the launch and the flow.
- Thermochemistry
- Chemical equilibrium computed by the app with NASA thermodynamic and transport data. Every report names the source used.
- Files
DXF,PDF,CSV,JSON,ENG,VTK,PNG,MP4(where applicable)- Not included
- Reacting combustion CFD, turbopump cycle analysis, conjugate heat transfer, grain structural analysis.
- Platforms
- Windows 11 (64-bit) and Apple silicon Macs on macOS 14 or later. Intel Macs, Windows 10 and Windows on Arm are not supported.
Preliminary design output. Not a substitute for qualified engineering review, testing, safety review, or export-control review.
A liquid engine case
- Define the operating point. Propellants, chamber pressure, mixture ratio, expansion ratio, ambient condition, and a sizing target: thrust, mass flow, throat diameter, injector geometry, or tank pressure.
- Solve the engine. First-pass or coupled steady-state. The convergence state and the thermochemistry source are reported with the result.
- Size feed and injector components. Orifice diameters, injector pressure drop, momentum ratio, and O/F consistency checks.
- Generate nozzle geometry. Bell, conical, or TIC contour with separation-screening context.
- Inspect the flowfield. Axisymmetric nozzle and plume cases with residual status and transient playback.
- Compare test data. Reduce measured hot-fire records and calibrate the design model against them.
- Export the case. PDF report, DXF contour, CSV/JSON data, VTK fields, and images or video of the solved fields.
Solid and hybrid motors, and the flight
Size a solid motor from its total impulse, burn time and peak chamber pressure, or a hybrid from its average thrust and oxidizer feed. Then build the vehicle around the motor and fly it with wind, recovery and dispersion. The flight uses the motor you solved.
Flowfield Studio
A 2D axisymmetric finite-volume solver for the nozzle and plume of the case you just sized: steady-state and transient runs, density and Mach-number fields, residual status, and PNG, VTK, and MP4 export.
It is a preliminary, nonreacting solver: combustion is not modelled in the flow. Every result shows its convergence state and solver settings. The CFD tab also solves the port flow of a solid motor and the air over the vehicle.
Checked against a documented engine
The published reference case is the Apollo Lunar Module Ascent Engine: pressure-fed, fixed-thrust, hypergolic, vacuum. NASA and contractor records supply the inputs; the application's outputs are compared against the same records.
| Quantity | Historical | RPL 1.0.0 | Difference |
|---|---|---|---|
| Vacuum Isp | 309.7 s | 307.97 s | −0.56% |
| Total flow | 5.08 kg/s | 5.155 kg/s | +1.47% |
| Effective c* | 1,724.7 m/s | 1,616.6 m/s | −6.27% |
The c* comparison is a diagnostic, not a match claim: Boeing's figure is a production-injector acceptance-test reduction. The package explains the difference instead of hiding it. Agreement with one reference case does not validate the whole solver. These values are from version 1.0.0. Version 2.0 computes the chamber by chemical equilibrium and gives different values for this case; they will be published with a 2.0 package.
Reports and CAD handoff
The PDF report states what was solved, which assumptions and thermochemistry source were used, and which warnings apply. The DXF contour comes from the same solved case, so the geometry you hand to CAD matches the reported case.
Pricing
Two licenses. Both unlock the complete application; they differ only in what the work is for. The license key activates the copy you already installed.
Business
Commercial work by one named user: company projects, consulting, paid engineering, and work delivered to a customer or employer.
$29per month
or $290 per year
Buy Business, $29/month- Included in both
- The whole application: liquid engines, solid and hybrid motors, vehicle and flight, and all of the CFD, with steady and transient runs and no plan-tier mesh cap; videos; DXF, VTK, PDF, CSV, JSON and
.engexport; project saving; updates released during the license term. - Billing
- These are subscriptions. Monthly plans renew each month and yearly plans renew each year at the price shown above until you cancel. Cancel in the Freemius Customer Portal; cancellation takes effect at the end of the paid term. Taxes and currency are calculated at checkout.
- Refund
- 7-day defect-based money-back guarantee on the initial purchase.
- Free trial
- 30 days, built into the download, no license key. The trial runs liquid engines, solid and hybrid motors, and the vehicle and flight. Trial PDF reports are watermarked; projects can be saved and reopened during the trial; image, DXF and VTK export are off, CFD is limited to one steady nozzle preview per launch, and videos are off.
- Several users
- Each license covers one named user and one device activation, and may not be shared. For a team, request volume pricing.
Freemius is the reseller and Merchant of Record. See full pricing and license terms, the Vendor Terms, and the Freemius EULA.
Questions people ask before buying
Can I use the results to build flight hardware?
Not on their own. Engine Workbench is preliminary design software. Its outputs need independent verification, qualified engineering review, and hardware testing before any hardware decision. The app and the reports say so, and label every estimate and fallback.
Personal or Business: which one do I need?
The dividing line is who the work is for. Coursework, hobby projects, and student team work are Personal. Work for a company, customer, or employer is Business. Both licenses unlock the same application. The pricing page covers the edge cases.
What happens when I cancel?
Cancel in the Freemius Customer Portal before the next renewal. Cancellation takes effect at the end of the current paid term, and access continues through that term.
Does it need an internet connection?
The engineering workflow runs locally and does not need an always-on connection. License activation and validation contact the licensing provider. Project files, reports, and exports are stored on your computer. See Security and local data.
Who makes it?
Rocket Propulsion Lab, a small, founder-led, independent software company that builds this one product. It has been in development since 2023. Write to contact@rocketpropulsionlab.net and a person answers. More on the About page.