PEGAS

Powered Explicit Guidance Ascent System, from here referred to as PEGAS, is an ascent autopilot for Kerbal Space Program made and ran in kOS, designed to control launch vehicles under a modified version of the game running Realism Overhaul. Its unique feature is the implementation of a real-word rocket guidance algorithm: Unified Powered Flight Guidance, as used in the Space Shuttle GN&C computer for the standard ascent flight mode. Short list of what PEGAS is capable of:

• estimation of a launch window,
• calculation of a launch azimuth,
• simple atmospheric ascent by pitching over and holding prograde with zero angle of attack,
• automatic guidance to orbits defined by:
  • apoapse
  • periapse
  • inclination
  • longitude of ascending node
  • or, alternatively, selecting an existing target,
• executing timed events (engine ignition, payload fairing jettison, or anything you want - via delegates),
• automatic staging, complete with ullage handling.

More info on my KSP forum thread, also see my prototype repository.

Version 1.2 is here! <== ORIGINAL

Version 1.2b is here! <== CUSTOM

What's different from the original script from Noiredd ?

• The script remove the need for pitching/rolling at launch and provide a basic gravity turn for atmospheric and vacuum flight (only tested on Kerbin with/without atmospheric effect)
• A new logs system has been added to provide you with a scrolling history with timestamp (relative to the launch event)
• For atmospheric flight, no need to worry about the UPFG activation timer. The script estimate when to start it for you during the flight (the countdown will become more precise as you approach it's best starting point)
• Advanced abort system inspired that work with user input or with automatic security:
  • Lost of steering control
  • Not enough thrust and negative vertical speed
  • Explosion/failling pieces are detected (manual STAGE trigger that one too!)

Original code are credited to Noiredd where abort system and part of the new early ascent code are credited to /u/only_to_downvote

How to use

1. Make sure you have kOS installed. Note: basic knowledge of kOS will be very handy.
2. Dowload files from this repository's kOS folder and place them in your Script folder.
3. Define your vehicle and mission - see tutorial and reference.
4. Once on the launch pad, load the definitions from pt. 2. and type run pegas. in kOS terminal.

How to get help

PEGAS is not a magical do-it-all, it needs some effort to set up and get running. It has been tested with several launch vehicles, from real-world launchers like Atlas V or Saturn V, through user-made vehicles, both in RO and vanilla settings. However, I cannot guarantee that it will handle any vehicle or that it is entirely bug-free. Likely, it will take you several tries before you get your rocket flying - and maybe you will find yourself unable to do that at all. I am willing to provide support, correct bugs and (to some extent) introduce new functionalities to PEGAS. In case of problems: read the how to submit issues page and then visit the issue tracker.

Demo

Here is a video demonstration of the initial release of PEGAS in action, flying an Atlas V to a parking orbit aligned with the International Space Station. It mostly focuses on explanation of the underlying guidance algorithm, only showcasing what functions PEGAS has instead of explaining how to use them. For that I strongly recommend reading the tutorial.

Note about this repository

I have been using tabs throughout the whole code, having its length set to 4 spaces in all my editors. I was unaware that github uses length of 8 - as a result, some of the .ks files look really bad. If your eyes hurt, you can force github to display them with tab size of 4 spaces by adding ?ts=4 to the URL of the file you're viewing. Unfortunately, I know of no way to make it a global setting (or even configure it for the repository).