To start out, Masten Space Systems had this idea before SpaceX did.
The issue is not a landing cradle. The issue is a landing cradle that is also a launch mount.
"Hovering is for humans"If flight control computers could choose a bumper sticker, that'd be it.When you hover you just give winds and other unknowns more time to influence your position.The best way to increase X-y accuracy is to hit the pad at higher velocity. Less time for unknown forces to act and unlike a human, a computer doesn't need to hover nearby to estimate the IIP.The only problem is that a you try to hit the pad at higher decelerations, you increase your Z uncertainty.The remedy for this is increase Z travel on capture. Which means a heavier mechanism.This is the gain of the cradle - you don't have to carry the landing gear with you, you leave it on the ground. Make it as tall and heavy as you want, to absorb as much residual vertical velocity as you need.My bet is that we'll see more slam, and less hover, but that because of the increased physical size, it'll look about the same.
A common concern I am seeing repeated about the cradle mount has been lining up the booster in heavy cross winds. Personally I think that this would be a non issue as rockets don't usually launch with heavy wind conditions. It is often an issue when landing on an ASDS because the landing site is out at sea.
Quote from: Basto on 01/25/2017 02:24 PMA common concern I am seeing repeated about the cradle mount has been lining up the booster in heavy cross winds. Personally I think that this would be a non issue as rockets don't usually launch with heavy wind conditions. It is often an issue when landing on an ASDS because the landing site is out at sea.You need to add gas (or more powerful) thrusters in the bottom to ensure good alignment. I would forget about this concept on a small ASDS, it's been shown on ground because you require stability.http://forum.nasaspaceflight.com/index.php?topic=41249.msg1592281#msg1592281
RB - I'm pretty sure there will be a mechanical guidance structure, a set of rails or what have you, that will take care of final positioning.There is no way the rocket will settle into hold-downs all on its own.There will be some features on the rocket, in lieu of legs, that will interface with this centering structure, and as someone observed, they should be located at the height of the empty booster's CG.
Drawn on a paper napkin (Stone Age MS Paint) during my lunch break. Pure Speculation. The Cradle Ring and 8 hydro-shafts would need to be massive and blast proof.