Basically the answer to all of those is SpaceX's next gen BFR rocket. It is scaled up significantly which makes second stage reuse practical. The challenge with

Basically the answer to all of those is SpaceX's next gen BFR rocket. It is scaled up significantly which makes second stage reuse practical. The challenge with a rocket the size of the Falcon 9 is that added significant fixed mass to the second stage (heat shielding, parachutes, etc.) will significantly Affect payload mass / performance. By going to a much larger class of rocket, those concessions for re-use become a smaller fraction of the total stage 2 mass.