OpenSpaceArch

Open Computational Architecture for Aerospace Hardware

A rocket engine that is computed, not drawn. Give it thrust, chamber pressure and a propellant pair; it derives the thermochemistry, sizes the chamber, solves the cooling, routes the channels, grows the metal around them and writes a watertight STL.

The reference model is a 5 kN LOX/CH4 aerospike with regenerative cooling on both the shroud and the plug.

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The idea

Conventional CAD asks you to draw a wall and then drill channels through it. This does the opposite, and the difference is the whole point:

1. Physics produces numbers. Thermochemistry → chamber sizing → Bartz heat flux → Barlow wall thickness → an iterative solve for how many cooling channels there must be and what cross-section each needs. No geometry yet.
2. The coolant voids are built first, as continuous signed-distance fields.
3. The wall grows outward from the voids by a per-station Barlow thickness, and the voids are subtracted. The metal that remains is the engine.

The outer surface is therefore a consequence of where the coolant had to go — never an input. Everything downstream (ports, manifolds, flange) hangs off computed positions.

Channel start angles use golden-ratio phyllotaxis with a deterministic seeded jitter, so the cooling jacket is aperiodic rather than an N-fold repeat — the same seed always yields the same STL.

What it currently produces

Values below come from dotnet run -- --physics at the default spec (5 kN, Pc = 110 bar, O/F = 3.2, CuCrZr):

Quantity	Value
Isp (sea level / vacuum)	323.7 s / 349.6 s
Mass flow	1.575 kg/s
Throat heat flux (Bartz, after film)	69.1 MW/m²
Throat wall (Barlow, SF 1.5)	1.01 mm
Cooling channels	32 shroud (R 0.68 → 1.24 mm) + 24 spike
Overall length	152.5 mm
Build time (0.3 mm voxels)	~36 s, ~5.4 GB RAM

The generated mesh is watertight. See Honest limitations before you send anything to a printer.

Requirements

• .NET 9.0 SDK
• Windows 10/11 x64
• 8 GB RAM for a 0.3 mm build; 24 GB+ if you push to 0.2 mm
• OpenGL 3.3+ for the interactive viewer (headless mode needs no GPU)
• Python 3.9+ with numpy, scipy, trimesh, matplotlib for analyze_stl.py (optional)

Layout

The project consumes LEAP 71's ShapeKernel by source path, so it expects a sibling directory:

your-workspace/
├── OpenSpaceArch/      ← this repository
└── PicoGK/
    └── LEAP71_ShapeKernel/

git clone https://github.com/ultrasurreality/OpenSpaceArch.git
git clone https://github.com/leap71/LEAP71_ShapeKernel.git PicoGK/LEAP71_ShapeKernel
cd OpenSpaceArch
dotnet build OpenSpaceArch.csproj -c Debug

The PicoGK kernel itself is vendored in Core/ (a headless fork — see THIRD_PARTY_LICENSES.md), so you do not need it separately.

Run

dotnet run -- --physics        # full physics chain, no voxels — a fast sanity check
dotnet run -- --headless       # build + export STL, cutaway and spec JSON at 0.3 mm
dotnet run -- --headless 0.2   # finer grid (~17 GB RAM, ~162 s)
dotnet run -- --sweep          # bounded design-space search + Pareto front
dotnet run                     # interactive viewer with a live digital twin

Exports land on your desktop: AerospikeV4.stl, AerospikeV4_Cutaway.stl and AerospikeV4_spec.json. Then:

python analyze_stl.py ~/Desktop/AerospikeV4.stl --json ~/Desktop/AerospikeV4_spec.json

Architecture

The pipeline, the invariants that must not be broken, and the parts deliberately left out of the build path are documented in ARCHITECTURE.md.

The one rule worth repeating here: every IImplicit.fSignedDistance must be spatially continuous. A per-channel step function in a distance field breaks marching cubes and silently produces a non-watertight mesh. This project learned that the expensive way.

Above the generator sits a bounded search layer: it samples a 6-dimensional box (Pc, O/F, contraction ratio, L*, safety factor, channel twist), runs the physics on each sample, discards invalid designs and computes a real non-dominated Pareto front over Isp, mass and thermal stress. Scoring weights are exposed as sliders — the human holds the weights, the machine only ranks.

Honest limitations

This is a generator, not a qualified engine. Known open items:

• ~31 disconnected shells in the last headless run, where a printable part wants one. The mesh is watertight and the fragments are small, but their origin is undiagnosed.
• Voxel mass has not converged. Between 0.4 mm and 0.2 mm the computed mass moves by 15%, so voxel-derived mass and thrust-to-weight are grid-dependent numbers — never compare them across resolutions. The Pareto front uses an analytic mass estimate instead.
• Overhang. Printed spike-tip-down, several thousand downward-facing points still sit below the 45° self-supporting angle and would need supports.
• The plug interior is modelled as longitudinal channels, not the branching truss such a geometry really wants. A skeleton router exists but is not wired in.
• No CFD, no FEA, no combustion stability analysis. The thermal model is 1-D Bartz with a film-cooling knockdown; the structural model is Barlow plus a thermal-stress warning.

License

OpenSpaceArch is licensed under the GNU Affero General Public License v3.0. You may use, modify and distribute it under those terms; a modified version made available over a network must also be offered under the same license.

Third-party components — PicoGK and ShapeKernel (Apache 2.0), Silk.NET and ImGui.NET (MIT) — are documented in THIRD_PARTY_LICENSES.md.

Export Control Notice

This software is published as open source and freely available to the general public without restriction. It implements general scientific, mathematical, and engineering principles commonly taught in schools, colleges, and universities.

This software qualifies as "publicly available" under the EAR (15 CFR §734.3(b)(3), §734.7) and as information in the "public domain" under ITAR (22 CFR §120.11).

Users are responsible for ensuring their use complies with all applicable U.S. export control laws, including ITAR (22 CFR §§120-130) and EAR (15 CFR §§730-774).

Contributors must NOT submit material subject to ITAR/EAR restrictions, including classified data, information received under NDA, or data from defense contracts.

This notice does not constitute legal advice.

Engineering Disclaimer

This software is a computational engineering tool intended solely to assist in design and development processes. It requires considerable engineering skill, expertise, and professional judgment for correct use and interpretation of computed results.

This software is not a substitute for independent engineering analysis, physical prototype testing, destructive and non-destructive testing of manufactured components, or compliance with applicable aerospace standards.

Contributing

See CONTRIBUTING.md. Contributions are accepted under the same AGPL v3.0 license; a CLA check runs on every pull request.

References

Physics and engineering sources are listed in REFERENCES.md.