Subscribe to download
X-Wing VTOL SSTO

Very robust and stable, userfriendly Single Stage to Orbit Space Plane.

LANDING/TAKE-OFF
Starts and lands vertically on its wings. There is no landing gear.
Use parachute for landing assist on atmosphere planets/moons (don't forget to repack the chute afterwards).

PROPULSION/FUEL
Turn on atmospheric scoops. Switch with (1) between Nitrogen and Liquid Fuel.
Make new Liquid Fuel with drills + ISRU (inside the loading bay)

This is a "proof of concept". I'm sure a lot can be done to make it more efficient and/or beautiful. Comments welcome!

IMPORTANT: Requires Kerbal Space Program version 1.5.1 and KSP Interstellar Mod for KSP 1.5.1

https://kerbal.curseforge.com/projects/ksp-interstellar-extended/files/2651246/download
(Edit: Actually requires KSPIE+1.20.13+for+KSP+1.5.1, if you can find it.)

1) Download
2) Unzip
3) Copy everything from the zip's "GameData" folder straight into KSP's "GameData" folder

Don't forget to switch KSP to version 1.5.1 (in the "Beta" settings)

(you will receive an error message regarding the "Filter Extensions", which you can ignore--it doesn't affect the game)