I have an idea for how to improve the landing of the rocket stage: instead of fold-out landing-legs, why not fold-out wings? Or, a combination of both - legs with wing-like features - they function as wings until close to touch-down and then feather to support the rocket laterally upon landing?
They'd be on the wrong end of the rocket. The centre of mass is close to the engines, but not that close; the landing legs have to go at the bottom for obvious reasons, but any aerodynamic surfaces have to go near the vehicle's stern, as it moves through the air. Since it's descending vertically, this means the top. This is what the pop-out grid fins way up are for.
Fun fact: if the F9 first stage had traditional fins at the bottom, they wouldn't be able to do this. The vehicle would tumble in the upper atmosphere and end up either nosediving into the ground or breaking up.
I believe you and I understand the problem (I make planes for fun, so know a little bit about aerodynamics and CG) .. but what I think is that the wings could indeed be mounted to the rocket higher up the frame, over the legs - so when the legs deploy at the bottom, the wings deploy as well over the top - they'd be part of the same leg structure, only extended all the way to the top of the rocket body. Actually they'd need to be rotors, a kind of mini-wing, to spin the rocket body on descent, for drag .. like maple seed wings that flip out in the last stage of the flight envelope.
Well of course all this sounds easy, but KISS principles apply I suppose. Still, I could see this happening at some point in the future ..
