2026-08-26

Meco 0.6: Engine Assemblies

"The nozzle carves itself out of the math now. Everything upstream of it is still your problem."

Miku

Meco 0.6 is live. You set the numbers that matter and the sim builds the hardware. And for anyone who has asked whether this is all just maths under the hood: this is the release where you can see it.

Engine assemblies

Drop a Thrust Chamber into your schematic and give it five numbers: throat radius, expansion ratio, contraction ratio, chamber length, section count. The hardware materialises. The nozzle is a real Rao thrust-optimized bell, the contour family real engines fly, not a stock curve. You set two numbers; it works out the other four hundred cooling channels.

The Turbopump gets the same treatment. Four shaft layouts, from a single shaft to a geared three-shaft, with the shafts and gears sized from the layout you picked. Change a headline number and the hardware rebuilds while you watch.

See it in 3D

All of it renders live: the Rao bell, the chamber solids, the cooling jacket, in a view you can pin and resize. Wander into geometry that would not work and the editor tells you where you left the Rao chart, before you burn an afternoon on it.

The nozzle flow field is a thing you can look at now. The method-of-characteristics solution renders as an interactive 3D volume inside your bell, so you can spin the camera through the supersonic flow. Thrust comes from integrating that field, at the mass flow your simulation actually delivered. Push a bell too far at sea level and the view shows it. The flow lets go of the wall, the field greys out past the separation point, and thrust is counted only where the flow is still pushing.

Regenerative cooling gets its own drafting table. Choose how many sections carry coolant and the channels tile themselves around the wall. The rib land you set drives the channel width, section by section, in a table you can read like a drawing. There is a cross section, so you can see the wall you are building.

Test fire a Merlin 1D

The engine that flies Falcon 9 ships as a free-build template. Load it, run it, watch it hold its operating point. Then start turning knobs: the feed pressures, the startup schedule, the bell, the cooling. Find out what breaks and why.

If you would rather earn it, Mission 13 opens Chapter V and walks you through building it: place the Turbopump and wire its slots, give the pre-placed Thrust Chamber its headline geometry, author the startup, then tune the gas generator until the whole loop holds at steady state.

The startup is the good part. Real engines start as many valves on one schedule, and you author that schedule. Each valve has its own level, width and delay; a master ramps from 0 to 1 and each valve fires as it crosses its threshold. Stacked preview charts show the sequence before you run, so you can scrub the master and watch each follower fire in order. And it is not Merlin-only. Any engine you build can start that way.

This is inspiration, not a digital twin, and the mission says so out loud. SpaceX has never published Merlin's internal geometry, so every dimension in there is derived or back-solved. The debrief puts your numbers next to the published figures.

Undo, and the numbers underneath

Undo works across the editor now. Delete the wrong component mid-tune and one keystroke puts it back, with its links, its chart traces and its samplers. One gesture is one step, so undoing a five-node drag takes one press.

The physics is written up properly now. There is a preprint on the coupled engine model behind Meco: the system solve, the nozzle flow field, and how the two agree with each other, with a Merlin 1D class engine as the case study. It has a DOI, so you can check my work: 10.5281/zenodo.21864769.

In the same spirit, the Isp on the thrust card is engine Isp: the number real datasheets quote, with the gas generator's propellant counted against it. Nozzle-flow Isp is still there, labelled as what it is. The built-in Vulcain 1 sits on its published numbers: 1140 kN of vacuum thrust, and engine Isp within 1% of 431 seconds.

Pumps report available NPSH beside their curves and cavitate when the propellant's own vapour pressure says they should. Shafts and gear meshes cost you real torque. Thrust pays for the drag along the nozzle wall.

One warning, because that last group is physics and not display. Pumps now produce roughly 9 to 13% less head and torque than they did in 0.5. A saved engine that used to close may need a retune. If yours suddenly runs lean, start there.

Also in 0.6

• The mission hub is grouped into chapters, with a line under each mission saying what you learn there. Continue drops you exactly where you left off.
• Right-click or long-press opens the menus; a single click just selects.
• Error messages name the control you can see, not an internal path.
• The node graph comes in light now. Pick your theme in Settings.
• Music and SFX have their own volume sliders, and helium joined the cold-gas options.
• Every gas path runs on a new solver that copes with layouts the old one could not.