There was an international venture to create an SSTO, with the UK making engines and Europe making the fuselage, called Skylon. I'm not sure what the current status is, but it did indeed Work In Kerbal Space Program.

And yeah, that is a very relevant XKCD! More to the point, these days I can't look at the Millenium Falcon without thinking "NOO! They need to point the other way and burn retrograde so they won't crash into Yavin IV!!" The concepts are alien and not intuitive, like quantum mechanics, but once you accept them it becomes a new way of looking at and understanding the world.

It's pretty cool that you can bend orbital manuevers with just some little tags, and see how easily passing by a planet or moon might give you the opportunity to accelerate or decelerate and drastically alter your orbit. Pass on the inside and you can slow down and tighten your orbit, pass on the outside and you can speed up or stretch it out.