Meco, the rocket engine design simulator

Meco is a rocket engine design simulator. Design, build and test rocket engines hands-on, with real physics.

It's a sim that won't lie to you about the numbers on the graph. Every node is inspectable. Every graph is live. The engine model behind it is described in a publicly available research paper, with a DOI and all, so you can check my work: 10.5281/zenodo.21864769.

Space games bend the physics to keep it fun. Engineering tools make you write the model before you see anything. Meco is the sim already built, with the numbers in the open.

What players say

Reviews of earlier versions.

Wire it up and test fire

Drop pumps, injectors, valves and nozzles on a node graph, wire them up, set the numbers, and test fire. Every number you change answers back on the live graphs and in the 3D hardware.

Twist a number, watch the engine answer

Twist an injector orifice, and the chamber pressure curve responds in real time. Tighten the cooling channels and watch the thermal margin shrink. Reshape the nozzle and see what it does to Isp. Pump and turbine performance curves you can sample as you tune.

Set four numbers, get a real nozzle

The Thrust Chamber builds a real Rao bell contour and tiles the regenerative cooling channels for you, live in 3D. The supersonic flow field through your bell renders as a 3D volume and grays out past the point where the flow separates. Thrust comes from integrating that field, not from a lookup table.

The turbopump sizes its own shafts and gears

Pick one of four shaft arrangements: single shaft, turbine mid-shaft, geared three-shaft or geared direct drive. The Turbopump sizes its own shafts and gears, with live 3D internals.

Coaxial or pintle, built while you type

The Injector Head is the last assembly between your propellant lines and the chamber. Pick coaxial or pintle, slot your two orifice legs, and set the element pattern. The head drives the leg geometry and builds itself in 3D, and the wells repaint as you type.

Author the startup, then light it

Put every valve on a schedule: pumps spin up, valves crack open, the gas generator lights, in the order you set. Get the sequence right, and the engine runs nominal. Get it wrong, and the graphs tell you where.

Three ways to play

Learn step-by-step (Mission Mode, start here). Fourteen guided missions, from "what's a model?" to recreating the Merlin 1D that flies Falcon 9. Senior engineer Miku Aoyama walks you through, deadpan, accurate, mostly patient. On most mission objectives a "Need a hint?" button names what's off when a build misses. Finish a graded mission and each result with medal tiers earns bronze, silver or gold.

You're an underpaid engineer at Mecodyne, the kind of propulsion company that ships rockets aggressively and has opinions about your eyebrows. On your first day, you accidentally fire up a Vulcain 1 on your coworker's workstation. The graphs come alive. The Vulcain runs. You probably shouldn't be doing this. That is Mission 0, and the missions build from there.

Take complete control (Engineering Mode). Skip the missions. Engineering Mode is free build: an empty canvas, the node-based editor, live graphs and real-time samplers. Drop in components, set every number yourself, and press Run Test. Good for "what if I just…" experiments.

Recreate real engines. Same components, same physics. Test-fire the Merlin 1D in Mission 13, or start from its free-build template. Build an F-1 from scratch. Or something that's never existed and probably shouldn't. Push propellants and geometry, and read what the graphs say.

Heads up

This isn't a casual arcade game. It's a serious engineering sim with a real learning curve, and honestly, your first designs probably won't hit their targets. That's the point. In the missions, when a build misses, a "Need a hint?" diagnostic tells you what's off and walks you to the fix one item at a time: run the test at least once; your mixture ratio is still stoichiometric, so dial the gas-generator valve richer; that component name looks like a typo. In free build it's you and the graphs. Either way, you figure out which assumption was off, and try again.

If you've spent time curious about what actually goes on inside a running rocket engine, and why a 5% change in injector geometry can ruin your whole afternoon, Meco was built for you.

What it is, honestly

Meco is in Early Access and playable today. The full core loop is here: design an engine, fire it, read the graphs, and iterate. I ship updates regularly. Here's what's already in, and what I'm building next.

Playable now:

• Missions Chapters I to IV complete, and Chapter V (Legendary GG Engines) opened with Mission 13: recreate the Merlin 1D
• Thrust Chamber, Turbopump and Injector Head assemblies with live 3D hardware, from the injector face to the gear train
• Staged startup: author every valve on a schedule
• Thrust and engine Isp measurement, the numbers real datasheets quote

Building next:

• The rest of Chapter V: A-7 Redstone and Vulcain 1 recreations
• The impinging injector configuration, plus the ducts and manifolds that connect assemblies
• Expander-cycle components
• The whole engine in 3D: every assembly joined into one machine, from propellant inlets to exhaust
• Component mass, for thrust-to-weight numbers
• Thermal and load stress limits
• Historical campaigns

I intend to finish the roadmap in 2027. I build Meco solo, so every purchase funds the work directly.

Why I build an accessible rocket engine simulator

To be a spacefaring civilization we need a lot of people who can build and maintain rocket engines, in every colony. That is a teaching problem before it is a hardware problem.

Meco is the part of the answer one person can build. My goal is to keep it commercially viable enough to sustain me, and eventually a small team.

• Meco is made by Loren Aerospace Ltd, which is me, Dannie Sim.

Come hang out

Come in and join the folks who are just as into rocket engines as you are.