: To reach the outer planets (Jool, Eeloo) with minimal fuel, launch toward Eve first. Passing behind Eve in its orbit will "pull" your craft, boosting your velocity and raising your apoapsis significantly for almost zero delta-V.
Instead of building massive, expensive rockets, learn to use planets as "free" engines. Kerbal Space Program (v1.12.5.03190) [GOG]
: For precise data on your suicide burns and delta-V. : To reach the outer planets (Jool, Eeloo)
: Always perform your major ejection burns at the lowest possible point of your orbit. Eeloo) with minimal fuel
Since KSP 1 development has ended, the mod scene is incredibly stable. For an "interesting" upgrade, consider:
The most interesting physics quirk in KSP is that your engines are more effective when you are moving fast.