Ever wished of having homemade asteroids?
Might seem impossible without mods, but actually, it's really easy. You are just gonna want to do a back-up to avoid corruption risks...
To help me explain how to do it, the entire guide is in the form of an Imgur album
Here is the full guide
Have fun! I will leave the secrets of what you can do with it up to you!
Go here to see the list of secrets (spoilers)!
Check out my KerbalGuides tutorial series here
It seems like placing down this asteroid on any multiplayer server will crash the game.
EDIT 6/2/16: This guide still works perfectly, although I've updated some of the thread.