How do you SSTO to duna?
Okay so I've tried for 2 days straight to land a plane on duna. I can build a plane that has a really good balance of center of mass and center of lift both with full fuel and no fuel, I can get to orbit, I can get to duna even with a 250 ton Mark 3 cargo plane that needs to orbit kerbin 3 times to even get out of its SOI and over to duna. And I can also land on kerbin. However, I CAN'T land on Duna. There's just no way, and it feels like I never will. I can't even control the plane anywhere nea
Well, first, ya gotta post a craft or a savegame or even just a pic. There are 18 million rules of thumb for building and flying spaceplanes, and we have no way of knowing which you understand and which are tripping you up.
Since your craft is heavy (MK3), it is absolutely going to need aerospikes on the belly to manage a horizontal landing, unless you want to land your SSTO on its tail.
And yes, the atmosphere on Duna is quite thin, so you are going to need a lot of extra time to make