Possibly with modded rotators with infinite rotations (Not actually infinite, just really much). If you just want to have a long flight, you could use an infinite fuel tank. With using XML-modding you cant make a engine that doesnt uses fuel. If you need the rotator, just tell me.
You can't you can make it extremely efficient but you need fuel
Ok found it, here is the link to it, it's the same size as a normal fuel tank.
I just remembered I have it in one of my subassemblys post as well, I'll go get a link to it now...
I have a infinite fuel tank in a lot of my builds, I found it in an subassemblys post a while back (I for got who from).
@PilotOfFuture Thanks!
Possibly with modded rotators with infinite rotations (Not actually infinite, just really much). If you just want to have a long flight, you could use an infinite fuel tank. With using XML-modding you cant make a engine that doesnt uses fuel. If you need the rotator, just tell me.