Liquid engines · version 2.0
Pressure-fed liquid engine design
Enter the propellants, chamber pressure, mixture ratio and a sizing target. The app solves the operating point, sizes the injector and feed system, draws the nozzle contour, and writes the report from the same solution.
Windows 11 (64-bit) and Apple silicon Macs (macOS 14 or later), version 2.0.1. The Mac app is signed and notarized; the Windows installer is not code-signed.
What it computes
- Operating point
- First-pass or coupled steady-state solve: characteristic velocity, chamber temperature, vacuum and ambient Isp, mass flow, thrust coefficient, expansion behaviour, and separation-screening flags, with the convergence state reported.
- Thermochemistry
- Chemical equilibrium computed by the app at the exact O/F, chamber pressure and area ratio (NASA RP-1311 method, NASA thermodynamic and transport data), with species and transport properties at chamber, throat and exit. Embedded reference tables and a screening correlation cover propellants outside it; the source used is named in the results and the report.
- Injector
- Unlike doublets, triplets and showerheads: orifice sizing per stream, injector pressure drop, momentum ratio, packing and ligament checks, and O/F consistency warnings.
- Feed system
- Pressure budget from tank to chamber and the tank pressure for the solved flow rates.
- Nozzle
- Bell, conical and TIC contours with throat, exit, length and area ratio.
- Test data
- Hot-fire records reduced to effective c*, Cf, discharge coefficients, O/F and Isp, with residuals, to calibrate the design model.
What you enter
- The operating point. Propellants, chamber pressure, mixture ratio, expansion ratio and ambient condition.
- One sizing target. Vacuum thrust, total mass flow, throat diameter, injector geometry, or tank pressure.
- Thermochemistry and nozzle model. Auto, Tabulated CEA, Screening Correlation or Chemical equilibrium, and frozen or equilibrium nozzle flow.
- Injector and feed. Injector element type and its coefficients, and the feed-system pressure budget.
What you get
A solved case gives the operating point, the injector and feed sizing, the nozzle contour and the report, all from one set of inputs and assumptions. The reference case, the Apollo Lunar Module Ascent Engine, is published with its sources on the sample outputs page.
Files
.dxf- Nozzle contour for CAD or machining reference.
.pdf- Report: solved values, assumptions, thermochemistry source, warnings.
.csv/.json- Solved data for your own tools.
.vtk- Flowfield Studio fields (licensed plans).
.png/.mp4- Field images and playback videos (videos on licensed plans).
- Projects
.rplproj, reopened with the full solve context.
Limits
- Pressure-fed engines only: no turbopump cycle analysis.
- No regenerative cooling or conjugate heat transfer.
- Flowfield results are nonreacting and preliminary.
- Agreement with the reference case does not validate the whole solver.
Trial and licenses
The 30-day trial runs the liquid engine workflow, with a watermarked PDF report. Saving projects, DXF and VTK export, transient flowfield runs and videos need a license. Personal ($10/month or $99/year, noncommercial work) and Business ($29/month or $290/year, commercial work) both include the whole application: liquid engines, solid and hybrid motors, vehicle and flight, and all of the CFD, with no plan-tier mesh cap. See pricing.