Aerospike Nozzle Design

This project provides a modern, fully tested implementation of the aerospike nozzle solver based on the plug‑nozzle contour algorithm developed by C.C. Lee (NASA MSFC, 1963).

It includes:

• a modular solver library (src/aerospike)
• a modern PySide6 GUI (src/aerospike_gui)
• a complete pytest suite (tests/)

The original Tkinter GUI by Matthew Vernacchia (MIT Rocket Team, 2014) is available at:
https://github.com/mvernacc/aerospike-nozzle-design-gui

This repository replaces that interface with a new PySide6 application and a rewritten solver, geometry, plotting, and export modules.

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Installation

Requires Python 3.12, NumPy, and Matplotlib.

Install the core solver:

pip install aerospike

Install the optional GUI:

pip install aerospike[gui]

The PySide6 GUI is tested on Linux (X11/Wayland).
Headless CI uses Matplotlib’s Agg backend.

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Running the GUI

After installing the GUI extras:

aerospike-gui

The interface provides panels for:

• chamber conditions
• gas properties
• propellant presets (LOX/LH₂, LOX/CH₄, RP‑1, hybrids)
• ambient pressure or altitude
• atmosphere presets (sea level, 5 km, 10 km, vacuum)
• expansion ratio or exit radius
• solver results
• embedded Matplotlib plot
• save/load (JSON)
• export (XYZ, STL, SVG)
• altitude performance sweep with bell‑nozzle comparison

Press Solve to run the solver and update all panels.

Press Run Altitude Sweep to generate a dual‑axis plot showing:

• aerospike thrust vs altitude
• bell‑nozzle thrust vs altitude
• aerospike thrust coefficient (C_f)

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Saving and Loading

Design parameters can be saved to and loaded from JSON files.
The GUI includes a dedicated panel for this.

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Exporting Geometry

The GUI supports exporting spike geometry in three formats:

• XYZ point cloud — for CAD lofting or point‑curve workflows
• ASCII STL mesh — for 3D printing, CFD meshing, or mechanical integration
• SVG 2D line art — for laser cutting, DXF conversion, or vector CAD

The STL exporter includes advanced geometry features:

• Spike truncation (0.4–1.0 of full length)
• Mounting flange extrusion with configurable thickness and radius
• Bolt circle generation (bolt count, bolt‑hole radius, bolt‑circle radius)
• Bolt‑hole cylinders modeled directly into the STL mesh

These additions allow direct export of mechanically mountable aerospike geometries, suitable for:

• test‑stand hardware
• thrust‑stand fixtures
• 3D‑printed prototypes
• CFD inlet/outlet boundary modeling
• CAD assemblies

The SVG export produces a clean mirrored 2D contour suitable for manufacturing templates.

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Solver

The solver implements the C.C. Lee plug‑nozzle contour algorithm with modernized flow physics:

• Newton–Raphson inversion of the area–Mach relation
• multi‑layer atmospheric model
• direct analytical inversion of Pe → er
• stable behavior for large expansion ratios
• improved geometry scaling
• altitude sweep helper for off‑design analysis
• bell‑nozzle comparison model

Reference documents are included in the references/ directory.

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Testing

Run the full test suite:

pytest

Tests cover:

• flow relations (Mach, Pe, er(Pe), atmosphere)
• geometry generation (XYZ, STL, SVG)
• solver behavior
• plotting (standalone and GUI‑embedded)
• type definitions
• SVG scaling, mirroring, and empty‑profile fallback

The plotting module provides two APIs:

• plot_results(result) — standalone 2×3 subplot version
• plot_results_gui(result, ax) — embedded version for PySide6

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Repository Structure

src/aerospike/
    flow.py
    solver.py
    geometry.py        # XYZ, STL, SVG export
    plotting.py
    types.py

src/aerospike_gui/
    controller.py      # solver orchestration, export helpers
    window.py          # main GUI window
    widgets/           # panels (inputs, results, export, save/load)

tests/
    test_flow.py
    test_solver.py
    test_geometry.py   # includes SVG tests
    test_plotting.py

references/
    C.C. Lee algorithm documents