The Suite · FSAP

The FSAP Suite

Design your team's liquid engine, end to end.

One host program plus six focused sizers. Each runs standalone in its own window — and each plugs into FSAP for whole-system analysis. Size the injector, the chamber, the feed lines, and the tanks; then wire them together and solve the whole thing. The physics uses the same trusted methods you meet in your textbooks and courses, made approachable, visual, and affordable for learning.

Program	Name	What it does	Typical user	Project file
FSAP	Fluid Systems Analysis Program	The host: solves whole feed systems — pressures, flows & temperatures	Every team	.fsap
OPS	Orifice / Pipe Sizer	Sizes a single orifice or run of pipe/tube	Every team	.opsproj
INJ	Injector Sizer	Sizes injector elements and face patterns	Every team	.injproj
TCC	Thrust Chamber & Combustion	Combustion performance and chamber cooling	Every team	.tccproj
TKS	Tank Sizer	Sizes propellant/pressurant tanks to ASME code	Every team	.tksproj
PASP	Pump Analysis & Sizing Program	Sizes centrifugal pumps & inducers (advanced)	Turbopump teams	.paspproj
TBS	Turbine Sizer	Sizes the turbines that drive pumps (advanced)	Turbopump teams	.tbsproj

What unifies the suite

Learn one tool, and the rest feel familiar.

Every program shares the same approach — the same real fluids, the same honest physics, the same clean single-window feel — so the second tool you open already makes sense.

Real propellant properties

CoolProp equations of state across all seven tools — liquid, gas, two-phase, and supercritical — for the propellants teams actually fly: LOX, N₂O, ethanol, IPA, methane, propane, RP-1, hydrogen peroxide, and the usual pressurants. No constant-property guesswork.

The multi-unit display

Every result is shown in all the common units at once — psi/bar/kPa, °F/°C/K, plus flow and density — and every row is editable. Students never lose points, or a test stand, to a unit-conversion mistake.

Honest, cited physics

Every correlation names its source — the same Bartz, Colebrook, Crane TP-410, NACA 1135, and ASME references taught in class — shows its accuracy band, and warns when you push out of its valid range. A learning tool, not a black box.

Approachable by design

Clean single-window apps with light/dark themes, greyed-out fields that show exactly which number the tool is solving for, worked example projects to open and explore, in-app theory pages, and a scripting mode for trade studies and coursework.

Standalone or connected

Each tool is its own program — install only what you need. When you're ready to see the whole engine, each one exports a small component pack that FSAP reads and couples into one model.

Test-gated & trustworthy

Every program ships a large automated test suite — thousands of tests across the suite — checked against textbook examples and published reference cases, so teams and instructors can rely on the numbers.

The programs

Five core tools. Two for turbopumps.

A pressure-fed team takes a design from propellant choice to a complete, analyzed engine with FSAP + OPS + INJ + TCC + TKS. Teams ready to attempt a pump-fed engine add the advanced pair.

FSAP HOST

Fluid Systems Analysis Program

Draw your feed system like a circuit, then solve it — pressures, flows, and temperatures across the whole engine.

Project file: .fsap
Typical user: Every team
References: GFSSP · CoolProp · Darcy-Weisbach / Colebrook

Build it like a schematicPlace components and draw traces between their pins. Junctions track pressure, temperature, and volume; one-click Auto-Layout turns a sketch into a readable diagram.
Steady-state & transientA Newton-Raphson solver finds the whole-network operating point; the transient solver time-marches with live plots and CSV — blowdown, pressure decay, chilldown.
Real-fluid propertiesCoolProp equations of state throughout, including cryogens (LOX, LN₂, liquid methane) and two-phase flow.
A full parts libraryPipes, orifices, valves and fittings, regulators, check/relief valves, heat exchangers, vaporizers, and first-class propellant tanks with liquid tracking.
Couples the whole engineBrings the sizers’ component packs together and solves tanks → feed lines → injector → chamber as one model, with valve-sequence scripting and per-propellant mass tracking.
Studies & goal-seekingParameter sweeps and goal-seeking from a Study panel — "what orifice gives me this chamber pressure?", "trim fuel flow to hit this mixture ratio."

Validated against

Closed-form hand calculations (regulator set-point, static head, pump and orifice operating points), built-in conservation checks, and 20+ worked examples you can open and learn from.

Why teams love it

It makes a whole feed system understandable on one screen — and grows with the team, from a single pressurized tank to a fully coupled engine model.

OPS

Orifice / Pipe Sizer

Size any orifice, tube, or line — liquid or gas — with real properties and built-in choke, cavitation, and pressure-rating checks.

Project file: .opsproj
Typical user: Every team
References: NACA 1135 · Crane TP-410 · IEC 60534 · ASME B36

Four solve modesSolve for diameter, mass flow, outlet pressure, or flow coefficient — greyed fields make it obvious what the tool is computing.
Automatic phase handlingPick a fluid once; OPS decides liquid, gas, or two-phase from your conditions, with a live indicator of how close you are to boiling.
Orifice & pipe physicsIncompressible (Bernoulli) and compressible (Crane TP-410 / NACA 1135) flow with choke detection and Mach reporting, Darcy-Weisbach friction, and a full Crane fittings catalogue.
Cavitation & boiling checksTwo-phase pressure-drop correlations, boiling and critical-heat-flux warnings, and an IEC-standard cavitation check for liquids.
Real, buyable hardwareASME/ASTM pipe schedules and Swagelok tubing tables with max-allowable-working-pressure and burst checks — size to tubing your team can actually order.
Sweeps & exportParameter sweeps with plots, a cryogenic chill-in calculator, in-app theory pages, and one-click export to FSAP.

Validated against

Crane TP-410 worked examples, NACA 1135 tables, IEC cavitation cases, and published tubing pressure ratings.

Why teams love it

The everyday workhorse — fast, honest answers for orifices and lines, with the choke, cavitation, and pressure-rating checks that keep a first build safe.

INJ

Injector Sizer

Design your injector — impinging, swirl, or pintle — in one window, with the element types and propellants student engines actually use.

Project file: .injproj
Typical user: Every team
References: Sutton · Bayvel · Rupe

Every element familyImpinging doublets (unlike and like-on-like), coaxial pressure-swirl atomizers with an auto-sizer, and throttleable pintle elements sized to a target momentum ratio.
Sizing your waySolve for hole diameter, element count, pressure drop, or mixture-ratio match, with constant, Reynolds-corrected, cavitation-limited, or cold-flow-fit discharge coefficients.
The stiffness guardrailA ΔP/Pc stiffness check with pass/warn/fail flags against the standard 15–25% rule — one of the most important early guardrails — plus per-orifice cavitation.
Face pattern & film coolingMulti-ring concentric patterns, fuel-film cooling, manufacturability spacing checks, and to-scale top-down and cross-section drawings of your face.
Propellants teams actually useN₂O, ethanol, IPA, propane, hydrogen peroxide, LOX, methane, and RP-1 — plus water for cold-flow testing — with cited, condition-dependent properties.
Learn from real designsOpen and study reproductions of well-documented injectors as teaching cases, then adapt the ideas to your own engine.

Validated against

The standard injector-design literature (Sutton, Bayvel, Rupe) and reproductions of well-documented injector cases.

Why teams love it

The injector is where many first engines succeed or fail — INJ makes the trade between elements, holes, stiffness, and mixing visible and honest.

TCC

Thrust Chamber & Combustion

Combustion performance and chamber cooling, RPA/CEA-style — Isp, c*, chamber temperature, and a real cooling estimate from your propellant choice.

Project file: .tccproj
Typical user: Every team
References: NASA CEA · Bartz · RPA

Combustion performanceA Gibbs free-energy-minimization equilibrium solver (the CEA method, on NASA thermo data) returns chamber temperature, species, Isp, c*, thrust coefficient, and thrust — shifting or frozen.
Find your operating pointSweep mixture ratio, chamber pressure, and expansion ratio, and plot altitude performance to find the sweet spot.
Nozzle & chamber geometryConical and bell (Rao) contours, method-of-characteristics for the curious, and chamber sizing by characteristic length (L*).
Cooling that saves hardwareBartz gas-side heat transfer, regenerative (coaxial & channel-wall) cooling with coolant ΔP tracking, film and radiation cooling, and a balanced wall-temperature solve.
Collegiate propellant pairsReady-to-run LOX/ethanol, methalox, N₂O/ethanol, LOX/RP-1, LOX/propane, and hydrogen-peroxide systems.
Built for class and buildNative .tccproj projects, import of RPA configuration files, and nozzle-contour export for CAD.

Validated against

NASA CEA reference results and a corpus of published engines — small research and collegiate-scale LOX/ethanol, nitrous/ethanol, and methalox engines, alongside textbook references like the RL10 and SSME.

Why teams love it

It connects propellant choice to performance and to the cooling reality of a real chamber, using the same methods taught in propulsion courses — so it doubles as a study aid.

TKS

Tank Sizer

Size your propellant and pressurant tanks to ASME pressure-vessel code — including cryogenic and vacuum-jacketed tanks.

Project file: .tksproj
Typical user: Every team
References: ASME BPVC Section VIII-1

Four tank typesHorizontal bullet tanks, spheres, bolted-cover tanks, and vacuum-jacketed cryogenic tanks with insulation and boil-off.
ASME code-based sizingBPVC Section VIII Div 1 — shell and head thickness (UG-27/32), bolted covers (UG-34), hydrotest (UG-99), and external-pressure buckling (UG-28), each result tied to its code clause.
Cryogenic analysisMLI heat leak, support-strut conduction, and steady-state boil-off (%/day, days-to-empty) for LN₂, LOX, LAr, LH₂, and LCH₄.
Accessible materialsCarbon steels, 304/316 stainless, 6061 aluminum, and cryogenic 9% Ni steel with temperature-dependent allowable stress, plus custom entry.
Solve modesSolve for wall thickness, working pressure, or the diameter needed for a target volume; export straight to FSAP’s tank model.
Teach the basicsEvery clause is traceable, so the same workflow an instructor uses to teach pressure-vessel basics is the one your team builds with.

Validated against

ASME worked examples for shells, heads, and external-pressure cases, plus cryogen boil-off reference data.

Why teams love it

It turns "how thick does this tank need to be, and is it safe?" into a traceable, code-based answer.

Advanced track · Turbopumps

When your team is ready to go pump-fed.

Most student engines are pressure-fed. Teams attempting a pump-fed engine — typically graduate or experienced groups — have two more tools. These cover real, advanced engineering; treat them as the next step, not a first build.

PASP ADV

Pump Analysis & Sizing Program

Mean-line design of centrifugal pumps and inducers — from a duty point to pump geometry and a performance curve.

Project file: .paspproj
Typical user: Turbopump teams
References: Stepanoff · Gulich · Wiesner

Mean-line pump designFrom a target flow, speed, and pressure rise, PASP produces impeller geometry, head/efficiency/power, and a pump curve you can hand to FSAP.
Cavitation & off-designNPSH margins and off-design performance curves, with the classic slip-factor models (Wiesner, Stodola, Stanitz) shown side by side.
Real stage hardwareVaneless and vaned diffusers, a volute, basic rotating-disk stress checks, and CAD export.
A learning tool for impellersReference profiles and textbook cross-checks (Stepanoff, Wright, Gulich) make it a solid on-ramp to impeller design.

Validated against

Textbook cross-checks and reference impeller profiles (Stepanoff, Wright, Gulich).

Why teams love it

A solid, honest on-ramp to impeller design for teams ready to attempt a pump-fed engine.

TBS ADV

Turbine Sizer

Mean-line design of the axial turbines that drive turbopumps.

Project file: .tbsproj
Typical user: Turbopump teams
References: NACA · standard loss models

Mean-line turbine designSingle- and multi-stage axial impulse and reaction turbines, including the velocity-compounded "Curtis" stage common to small turbopumps.
Closes the power balanceSolves the headline question — how much drive-gas flow is needed for a given pump power and pressure ratio — plus velocity triangles and off-design maps.
Honest marginsEfficiency with a loss-model uncertainty band, and blade and disk stress screening.
Drive-gas presets & exportPresets for common gas-generator and decomposed-monopropellant cases; exports a turbine curve to FSAP to close the turbine-drives-pump balance.

Validated against

Standard turbine loss models and NACA references, with the loss-model uncertainty surfaced in the results.

Why teams love it

It closes the turbine-drives-pump power balance, so a team can size a real turbopump with honest uncertainty.

How the suite works together

Size each part separately, then connect them.

The tools share one component-pack format. Size in the focused apps, assemble in FSAP, and solve the engine as a coupled system.

Component packs → coupled engine modelTKS · OPS · INJ · TCC → FSAP

Size each subsystem

OPS for lines and orifices, INJ for the injector, TCC for the chamber, TKS for the tanks — and PASP/TBS if you're going pump-fed.

Export a component pack

Each tool writes a small, standard file describing what it sized.

Assemble in FSAP

Drop the packs into an FSAP schematic and connect them with traces.

Solve the whole engine

FSAP couples tanks → feed lines → injector → chamber and solves the operating point — and the turbine/pump power balance for pump-fed engines.

Get the whole suite for your team — free during the beta.

Students, rocketry teams, schools, and nonprofit engineering orgs. Install only what you need.

Read the docs Request beta access