42 - Spacecraft Simulation

This is a fork of the 42 Spacecraft Simulator. The intent of this fork is to provide an easier, deployment-friendly, and modernized version of 42. This fork builds the same as its upstream, and is also available as a docker image at https://hub.docker.com/r/sirromsystems/42 .

42 is a comprehensive general-purpose simulation of spacecraft attitude and orbit dynamics. Its primary purpose is to support design and validation of attitude control systems, from concept studies through integration and test. 42 accurately models multi-body spacecraft attitude dynamics (with rigid and/or flexible bodies), and both two-body and three-body orbital flight regimes, modelling environments from low Earth orbit to throughout the solar system. 42 simulates multiple spacecraft concurrently, facilitating studies of rendezvous, proximity operations, and precision formation flying. It also features visualization of spacecraft attitude.

Features:

• Multi-body dynamics (tree topology, rotational and/or translational joints)
• Rigid and/or flexible bodies
• Multiple spacecraft (prox ops, formation flying, or independent)
• Inter-spacecraft and spacecraft-surface contact forces support landers, rovers, and spacecraft servicing scenarios
• Two-body or three-body orbits, anywhere in the solar system
• Optional visualization
• Socket-based interprocess comm (IPC) interface to other apps
• Fast setup for concept studies
• Rigorous and full-featured to support full spacecraft life cycle

Installation

Docker

Pull the image:

docker pull sirromsystems/42

Linux

Install dependencies

sudo apt -y install make gcc g++ freeglut3-dev libglfw3-dev

Compile

make clean; make

Note: the compiler will attempt to detect what platform you're on (Linux, OSX, or Msys), but its success rate isn't great. If you have errors on the first compile or run, try editing your Makefile to manually set your 42PLATFORM.

Windows

See the file "Install-msys.txt" in the Docs folder.

OSX

For OpenGL graphics, newer Macs with Retina displays will need the GLFW graphics libraries, available from MacPorts, Homebrew, and probably elsewhere. Otherwise, you'll need the GLUT libraries, which are also readily available if not already installed on your system. Graphics are optional, settable in the Makefile by GUIFLAG.

Usage

Docker

If you're using docker, run it:

docker run -v ${PWD}/path/to/sim/input/dir:/42/testcase 42

Note: the docker image will attempt to look for the input case called "testcase", to change this simply provide the case name as the first argument:

docker run -v ${PWD}/path/to/sim/input/dir:/42/MyCoolSimName 42 MyCoolSimName

Native

The default folder for inputs and outputs is "InOut". Look there for sample input files. "Inp_Sim.txt" is the top-level input file.

The input/output folder may be changed for a sim run by running 42 with an argument. For example, enter this at the command prompt:

./42 examples/Demo

Light Reading

See the overview, "42 Overview.pdf", in the Docs folder. Also recommended:

• Nomenclature.pdf
• POV Menu.pdf
• Key Bindings.txt
• FSW Models.pdf
• Flight Regimes.pdf

Common Problems

1. 42 expects the input files to be plain vanilla text files. If your text editor adds formatting, makes straight quotes into smart quotes, etc, 42 may get confused. The most common symptom is generating the "Bogus input in DecodeString" error.

2. Also text-related, 42 is very simple-minded about reading the input files. Adding extra lines, or accidentally deleting a line, or swapping lines, will throw things out of synch. Again, the most common symptom is the "Bogus input in DecodeString" error. Use your debugger to trace back where the error was generated. (The actual mistake may be at that line, or may be somewhere upstream.)