KSP2 just released their first dev blog video detailing a few of their more exotic propulsion systems and the process behind implementing them into the game. There is just something really satisfying about using nuclear bombs as a form of interplanetary propulsion. Colonies will be a necessity for creating the more interesting technologies like metallic hydrogen.
https://www.youtube.com/watch?v=aR4b9EWxgWs
And here is the original trailer.
https://www.youtube.com/watch?v=P_nj6wW6Gsc