42 - Spacecraft Simulation

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

If you’re installing on Windows, see the file “Install-msys.txt” in the Docs folder.

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.

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.

Getting Started

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

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 Demo

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.)