I'm not keen on any sort of space plane or similar idea. The main issue is the forces acting on the vehicle along multiple axes. For a VTVL rocket like the Fa

I'm not keen on any sort of space plane or similar idea. The main issue is the forces acting on the vehicle along multiple axes. For a VTVL rocket like the Falcon 9, there is just one main axis along which acceleration and load-bearing is going through: straight up and down. For a space plane, you have at least two. One along the thrust line, and another when it is supporting itself on the ground and in flight. So now you have to reinforce the structure more, which adds a lot of weight. And that's disregarding the thermal protection system which is more complicated too.