Moon lander project: thrust vectoring with a PID controller

The goal of my Moon lander guidance software series is to learn and gain some experience with an end-to-end aerospace software project, especially on the topic of GNC. I have already written a few articles sharing my findings: for instance, this one about guidance. Today I want to talk about control. I will use the engine gimbal controller of my Moon lander1 project to explain how to design, tune and validate a PID controller. Read the 2049 words...

Dimensional analysis in Rust: how not to crash "Mars Climate Orbiter"

Software is complicated: ensuring that old features keep working, while holding the bugs away, is an every day’s fight. Thankfully, there are many (too often unknown) gems, either built in the language/compiler or as third-party libraries. Some time ago, I introduced SymPy, which allows one to use symbolic maths in Python, and do things such as solving equations or integrating functions. In this article, I will introduce you another nice library, for Rust this time: uom (units of measurement). Read the 1129 words...

How I'm learning Spanish and German

After finishing my studies in France, I wanted to enjoy the possibility of traveling and working in 26 countries without passport or laborious paperwork. The aerospace industry in France is also very international, and I consider it an asset to have lived in different countries and be able to speak various languages. Flag of Europe - Wikipedia, Public domain For these reasons, I searched outside France for my first job, and was able to get a job in Madrid, Spain. Read the 1418 words...

Moon lander project: PID-based vs TGO-based guidance

As part of my Moon lander guidance software, I am making several small prototypes for each subsystems, in order to test ideas, learn and choose the best option. While I progress on the overall project, I have already learned a lot of things and wanted to share some of them. In this article, I will talk about how to control the altitude and vertical velocity of a spacecraft in order to guide it to a soft landing. Read the 3922 words...

Symbolic maths in Python: Attacking a castle with SymPy

While working on my Moon lander guidance software, I am making several small prototypes to test ideas. One of them involves testing several control laws (of the acceleration), which implies quite a lot of manual calculations (to integrate to obtain the velocity and position). Doing these calculations by hand is tedious and error prone, and I thought about using a symbolic math program. Usually, a programming language can not manipulate variables without predefined values, but I found a Python library which can: SymPy. Read the 2028 words...

Software quality notes: nested "for" loops considered harmful

While working on Exomars as a software engineer, I was notified an issue to fix. I thought it was an interesting one, and spent some moments to think about how it could have been prevented in the first place. I care about code quality, and always try to build reliable software. For this purpose, I do not believe in rockstar developers (we are all fallible humans), but rather in (automatically enforced) processes and tools. Read the 1135 words...

Moon lander project: preliminary study of the guidance software

I have always struggled during my control theory classes, and almost failed one (out of the three I attended). With this history, some people would have developed a hatred for this subject, but I personally felt in love with it: I have always found it magical to be able to control physical things with software. I love making a pile of silicon1 do things by itself, and developing control algorithms makes it possible to build robots and other automated machines. Read the 2525 words...

Hello World with Rust and WebAssembly

For the second part of my Rust & WebAssembly journey, I will write a basic hello world project. Note: you can jump to the demo by clicking here. This will give me the opportunity to demonstrate how to write a simple Wasm module in Rust. I will focus on a simple frontend and ignore the backend: no complicated GET or POST requests, no websockets, etc. This article will present how to build a simple game, such as Matt’s Pont. Read the 3047 words...

Introduction to Rust and WebAssembly

In this article, I would like to talk about two technologies I’ve been playing with recently: the Rust programming language and the WebAssembly standard. I’ll start by presenting each of these two technologies and which problems they are trying to solve. Then, I’ll explain what are the advantages of a Rust-powered Wasm module, and why it can be useful. Finally, I’ll provide links to interesting documentation. WebAssembly Since many years, client side web applications, implemented in JavaScript, have been becoming larger and larger. Read the 1227 words...

"Too much precision" bug

I am currently working on the Rosalind Franklin rover, part of the Exomars 2022 mission to Mars. I develop a software layer to integrate the autonomous navigation algorithms (developed by CNES) with the hardware rover (built by Airbus). CNES has been working on image processing algorithms to give some autonomy to robots. Their expertise is being used, among other projects, in Exomars. Airbus is developing the actual rover, and has defined some APIs to be exposed to allow executing CNES’s algorithms. Read the 2831 words...