🚀 Ion-Propulsion: Gridded Ion Thruster Suite

A flight grade tri language (Python, MATLAB, C++) library for gridded ion thruster modeling and mission analysis, developed for space probes and GEO satellites.

Author: A Taylor

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🚀 Introduction

This repository contains the design and simulation tools for a gridded ion thruster that meets specific requirements for space probes and GEO satellites. The suite provides parity across three languages with verified precision (1e-6 tolerance).

🚀 High efficiency: Strive for a specific impulse (Isp) of at least 3,000 seconds for maneuvering and orbital raising.

🚀 Low propellant consumption: Achieved through ion extraction efficiency optimization and minimized grid erosion modeling.

🚀 Long mission lifetime: Careful material selection with grid erosion rate tracking and neutralizer performance modeling.

🚀 High thrust-to-weight ratio: Crucial for maximizing payload capacity and achieving desired mission objectives.

🚀 Grid optimization: Optimized grid design using Child-Langmuir law modeling to minimize ion divergence and maximize thrust generation.

🚀 Neutralizer performance: Ensures the neutralizer effectively compensates for charge imbalance created by the ion beam.

🚀 Thermal management: Integrated solar cell and thermal property modeling for optimal operating temperature range.

🚀 Reliability: Designed for radiation resistance, micrometeoroid impacts, and environmental stresses.

🚀 Compactness and integrability: Compact engine design for integration with spacecraft structure, power supply, and launch vehicle fairings.

🚀 Testability and maintainability: Comprehensive test suites across all three languages ensure performance and readiness.

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🛠 Project Scope

The project delivers three core modules with strict cross language parity:

🛠 dynamics: GEO/Lagrange mission profile calculations and low thrust trajectory modeling. Includes Hohmann transfer delta-v, Lagrange point estimation, spiral transfer analysis, and low thrust transfer time computation.

🛠 propulsion: High-fidelity Gridded Ion Thruster (GIT) models. Includes ion extraction efficiency, beam voltage/current modeling, Child-Langmuir current limits, grid erosion rates (molybdenum sputtering), neutralizer performance, and power processing unit integration.

🛠 optimization: Solvers for maximizing payload fraction (Tsiolkovsky rocket equation), minimizing propellant consumption, extending mission lifetime, and finding optimal Isp for power-constrained missions.

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📖 Repository Structure

📖 python/

Python package using Hatch build system with astropy.units for all physical quantities. Constructor input validation mirrors the C++ and MATLAB implementations for cross-language safety parity. Install with pip install -e ./python. Tests run with pytest.

python/
  pyproject.toml
  src/ion_propulsion/
    dynamics/mission_profiles.py
    propulsion/thruster.py
    optimization/solvers.py
  tests/
    test_dynamics.py
    test_propulsion.py
    test_optimization.py

📖 matlab/

MATLAB function-based structure with modern arguments validation blocks for type safety. Run tests with runtests('matlab/tests').

matlab/
  dynamics/
    geo_transfer_delta_v.m
    lagrange_point_l1.m
    low_thrust_transfer_time.m
    spiral_delta_v.m
  propulsion/
    GriddedIonThruster.m
  optimization/
    optimal_payload_fraction.m
    propellant_mass.m
    mission_lifetime.m
    optimize_isp_for_mission.m
  tests/
    test_dynamics.m
    test_propulsion.m
    test_optimization.m

📖 cpp/

Standard CMake project using C++20. Built with Google Test for validation. Build instructions below.

cpp/
  CMakeLists.txt
  include/ion_propulsion/
    constants.hpp
    dynamics/mission_profiles.hpp
    propulsion/thruster.hpp
    optimization/solvers.hpp
  src/
    dynamics/mission_profiles.cpp
    propulsion/thruster.cpp
    optimization/solvers.cpp
  tests/
    test_dynamics.cpp
    test_propulsion.cpp
    test_optimization.cpp

📖 docs/

Documentation and reference imagery for the project.

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🏗️ Build Instructions

🐍 Python

cd python
pip install -e ".[test]"
pytest tests/

🧮 MATLAB

addpath(genpath('matlab'))
runtests('matlab/tests')

⚙️ C++

cd cpp
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
cd build && ctest --output-on-failure

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🔬 Core Physics

All implementations share identical constants and equations:

Equation	Formula
Tsiolkovsky Rocket Equation	dv = Isp * g0 * ln(m0 / mf)
Child-Langmuir Law	J_CL = (4/9) * eps0 * sqrt(2e/mi) * V^(3/2) / d^2
Specific Impulse	Isp = (1/g0) * sqrt(2eVb/mi) * eta
Hohmann Transfer	dv1 = v_transfer_peri - v_park
Spiral Transfer	dv = sqrt(mu/ri) - sqrt(mu/rf)

📊 Physical Constants

Constant	Value	Unit
g0	9.80665	m/s^2
mu_earth	3.986004418e14	m^3/s^2
R_earth	6.371e6	m
GEO_radius	42164.0e3	m
epsilon_0	8.854187817e-12	F/m
e_charge	1.602176634e-19	C
m_xenon	2.18e-25	kg

Cross-language precision verified to 1e-6 tolerance.

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🔧 API Conventions

All three language implementations enforce the same API contracts. Key conventions to note when calling functions across languages:

🔧 geo_transfer_delta_v(r_park_km) — The r_park_km parameter is the parking orbit altitude above Earth's surface in kilometres (not the full orbital radius). The function adds R_earth internally. For example, pass 200.0 for a 200 km LEO parking orbit.

🔧 child_langmuir_current() — Computes space-charge-limited current density using V_total = V_screen + |V_accel|. The accelerator grid voltage is treated as a positive magnitude in the formula regardless of the sign convention used at construction time.

🔧 Input Validation — All three languages validate constructor and function inputs. Beam voltage, beam current, mass flow rate, grid spacing, and propellant mass must all be positive. Python raises ValueError, C++ raises std::invalid_argument, and MATLAB uses arguments blocks with {mustBePositive}.

🔧 optimize_isp_for_mission() — The optimizer is power-constrained: thrust is computed as F = 2·η·P / (Isp·g₀) and the solver searches for the Isp that maximises the resulting payload fraction. Both the power_W and eta parameters are active in the objective function across all three implementations.

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🧪 Test Summary

Language	Framework	Tests	Status
🐍 Python	pytest	36	✅ Passing
⚙️ C++	Google Test	31	✅ Passing
🧮 MATLAB	matlab.unittest	33	✅ Ready

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🤝 Contributing

Contributions are welcome. When submitting changes, please observe these project standards:

🤝 Cross-language parity: Any physics function added or modified in one language must be reflected in all three (Python, C++, MATLAB) with identical constants, formulas, and API conventions. Verify results match to 1e-6 tolerance.

🤝 Input validation: All constructors and functions that accept physical parameters must validate inputs. Beam voltages, currents, masses, and distances must be positive. Follow the existing pattern: Python uses ValueError, C++ uses std::invalid_argument, MATLAB uses arguments blocks.

🤝 Unit safety: Python functions must return astropy.units.Quantity objects. C++ and MATLAB functions document units in docstrings and header comments.

🤝 Build artifacts: The repository includes a .gitignore for Python (__pycache__, *.egg-info, .pytest_cache), C++ (build/, *.o, *.so), and MATLAB (*.mexa64, *.asv) artifacts. Do not commit generated files.

🤝 Tests: Every new function requires unit tests in all three languages. Run the full test suite before submitting.

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📋 Changelog

v1.1.0 — 2026

🔴 Bug Fixes

• optimize_isp_for_mission (Python): Wired power_W and eta into the objective function. Previously these parameters were accepted but unused, causing the optimizer to return pure Tsiolkovsky fractions instead of power-constrained results. Now matches the C++ implementation.
• child_langmuir_current (MATLAB): Corrected voltage variable from beam_voltage to screen_grid_voltage + |accel_grid_voltage|, restoring cross-language parity with the Python and C++ implementations.

🟡 API Alignment

• geo_transfer_delta_v (MATLAB): Aligned input convention to take parking orbit altitude above Earth's surface (km), matching Python and C++. Previously took the full orbital radius (km). MATLAB test updated accordingly.

🟡 Robustness

• GriddedIonThruster constructor (Python): Added input validation for beam voltage, beam current, mass flow rate, grid spacing, and propellant mass. Raises ValueError on non-positive values, matching the guards in C++ (std::invalid_argument) and MATLAB ({mustBePositive}).

🟢 Housekeeping

• constants.hpp (C++): Fixed documentation comment referencing "Rust" — corrected to "MATLAB".
• .gitignore: Added repository-wide .gitignore covering Python, C++, MATLAB, and IDE artifacts.

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📖 References

• Goebel, D.M. and Katz, I., Fundamentals of Electric Propulsion: Ion and Hall Thrusters
• Vallado, D.A., Fundamentals of Astrodynamics and Applications

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📖 Citation

If you use this repository in your research, please cite it as:

@misc{ATaylor_IonPropulsion_2026,
  author       = {A. Taylor},
  title        = {Ion Propulsion: Tri-Language Gridded Ion Thruster Suite},
  year         = {2026},
  url          = {https://github.com/ATaylorAerospace/Ion-Propulsion/},
  note         = {Accessed: YYYY-MM-DD}
}

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📖 Contact

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📖 License

This project is licensed under the MIT License. See LICENSE for details.