Chapter 13. Creating a Mod

One of the reasons why Kerbal Space Program is so popular is the wide array of custom parts and mods that the community has put together. If you get tired of building rockets using the built-in parts, you can download a pack of additional components and build more complicated ones. On top of this, you can download mods that add extra behavior to the game, as we discussed previously in Chapter 10.

If you’re just using other people’s mods, you’re missing out on the fun of creating your own. In this chapter, you’ll learn how to create and add an entirely new part to Kerbal Space Program, and then learn how to write code that extends the behavior of the game.


Rockets are composed of parts. A part is composed of at least two elements:

  • A mesh, which is the 3D object that you see in game

  • A config file, which is a text file that describes to the game what the part is and how it works

To make a custom part, you need to create both of these files and then place them in a folder that the game will look inside at startup.

Creating a text file is easy—all you need is a text editor, like Notepad, TextMate, or emacs. Creating a 3D model is quite a bit trickier: you need a 3D model editor, as well as the knowledge of how to use it.

While we don’t have the space to teach you how to use a 3D modeling program from start to finish—we’d need a whole book for that—we can teach you how to use a specific 3D modeling program to create a specific ...

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