Your inner rocket scientist, unleashed

A rocket engine design sim with real physics. Design, build and test rocket engines hands-on: 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 Turbopump sizes its own shafts and gears. 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.

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.

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.

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 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.

Key features

• Mission Mode with real engineering challenges. Guided builds with senior engineer Miku Aoyama, from your first model to a complete gas-generator turbopump cycle.
  
• Real physics, no shortcuts. Combustion, fluid dynamics, and heat transfer through regenerative cooling channels, all solved in real time.
  
• Recreate real engines. Build a Merlin 1D, an F-1, or a Vulcain 1 from the same components and physics.
  
• Display Units. Read every output in the units you actually think in, from kN to bar, across charts, samplers, and mission text.

Pro Content (optional add-on)

Soundtrack, technical reference PDFs, 3D-printable component models (STL/3MF), and high-resolution wallpapers. For the people who want the lore in their toolbox.

What's new

• 0.7: The Injector Head assembly, coaxial or pintle, built live in 3D. Mission 12 now teaches it on a LOX and liquid-hydrogen engine, and the Merlin 1D in Mission 13 gets its pintle. Six missions open on a plumbed bench, so you build the part each one teaches. Finish a graded mission and each result with medal tiers earns bronze, silver or gold, with the number the next tier asks for.
  
• 0.6: Engine assemblies. The Thrust Chamber builds a real Rao bell nozzle from four numbers and tiles the cooling channels for you, live in 3D; the Turbopump sizes its own shafts and gears. A brand new Mission 13: test-fire your own Merlin 1D. It also ships as a free-build template, yours to tinker with from the start. And undo/redo, everywhere in the editor.
  
• 0.5: Mission 0, your accidental first day on Miku's workstation. Three new gas-generator cycle missions (Turbopump Integration, Gas Generator Genesis, Injector Insights). Display Units, so you can finally read pressure in bar instead of pascals.
  
• 0.4: Real-time pump and turbine samplers with live performance curves. Auto-run on every edit. Pinned component editor with nudge buttons and mouse-wheel tweaking. Colorblind-safe chart colors (Okabe-Ito).

Early Access roadmap

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'd estimate the roadmap is done in 2027. I build Meco solo, so every purchase directly funds the work, and if enough people who think as you do buy it, I can do this full-time. Your support genuinely makes the difference.

Dannie Sim

Solo Indie Dev, Meco Rocket Simulator (formerly at Activision/Blizzard on Candy Crush and Sony PlayStation on Spider-Man 2)

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.

Come build something that works. Or something that doesn't, and work out why. Both are fine outcomes.