G-FOLD
├─ demo.png
├─ demo_data.html
├─ demo_traj.html
├─ LICENSE
├─ README.md
├─ requirements.txt
├─ src
│  ├─ plot.py
│  ├─ solver_util.py
│  └─ trajectory_solver.py
├─ vessel_parameters_earth.json
└─ vessel_parameters_mars.json

G-FOLD

G-FOLD (Guidance for Fuel-Optimal Large Diverts) algorithm implementation in Python 3. This code first solves a minimum-landing-error guidance problem for a closest landing point and then solves a minimum-fuel guidance problem to reach the landing point.

Table of Contents

• Installation
• Usage
• Features
• License
• Contact
• Reference

Installation

It's recommended to use venv to set up the environment.

python3 -m venv env
source env/bin/activate
(or for windows, double click "Activate.ps1" in env/Scripts/)
pip install -r requirements.txt

And there you go! We are good to go.

Usage

python3 solver_util.py 
   -f [Path to JSON file containing vessel parameters] 
   -N [Numbers of intervals (default: 20)]

There are two vessel parameters provided already, you can change some of it to see how the trajectory changes accordingly.
Higher N values lead to greater accuracy at the cost of performance, though generally, 20 to 60 suffices.

Features

Utilizes a Golden-section search to determine the optimal flight time.
(Since it's Python, it could be a bit of slow).

TODO

• Implement Successive Convexification.
• Generate C code for a better performance.
• Build a control module to run test in Kerbal Space Program.

License

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

Contact

For questions or feedback, please create issues!

Reference

[1] Acikmese, B., & Ploen, S. R. (2007). Convex programming approach to powered descent guidance for Mars Landing. Journal of Guidance, Control, and Dynamics, 30(5), 1353–1366. https://doi.org/10.2514/1.27553

[2] Blackmore, L., Açikmeşe, B., & Scharf, D. P. (2010). Minimum-landing-error powered-descent guidance for Mars landing using convex optimization. Journal of Guidance, Control, and Dynamics, 33(4), 1161–1171. https://doi.org/10.2514/1.47202

[3] Acikmese, B., Carson, J. M., & Blackmore, L. (2013). Lossless convexification of nonconvex control bound and pointing constraints of the Soft Landing Optimal Control Problem. IEEE Transactions on Control Systems Technology, 21(6), 2104–2113. https://doi.org/10.1109/tcst.2012.2237346