Elon says it's in slow motion too
"High resolution, color corrected, slow motion rocket landing video https://youtu.be/BhMSzC1crr0"
"High resolution, color corrected, slow motion rocket landing video https://youtu.be/BhMSzC1crr0"
[edit] wouldn't it be easier to hover it a few meters above land and grab it with some big robot arms?
If the 'x-wings' are what I think you're referring to, they're the landing legs. They are shaped like that to have as minimal impact on the air resistance of the ascending rocket as is possible. They open just before landing.
It can't hover. Even just using a single one of the nine engines, the engine can't be throttled down enough for the rocket to hover. The landing method relies on what they call a 'hover-slam', where they fire the engine during landing to slow it down just before it touches.
Landing this is extremely impressive. It is going four times faster than the speed of sound, and they are landing it on a pad smaller than a football field. Vertical landing of a returning rocket has never been done. It's also the key step in the process of dramatically lowering the cost of spaceflight which could usher in a new era of technology around earth, and on other planets.
Of course, these barge landings are the first high-velocity tests, so there'll be kinks to work out.
I was impressed by how small the barge looked compared with the F9 it's clever that the F9 can autonomously target such a small area. If they keep targeting 'Just Read the Instructions' by the time land based landings come to be it will be nailed. Awesome stuff!
There's a "boostback burn" at altitude to slow the horizontal velocity right after separation, an entry burn to put it into the atmosphere, and a landing burn just before it hits the deck. The guidance in between those last two burns is aerodynamic from the grid fins.
The first stage mass is ~18,000kg empty (which it nearly is on landing), and it's coming in at its terminal velocity, which is, as a WAG, maybe 70m/s.
What's more, it cannot hover, as even one engine has a greater thrust at minimum throttle than the rocket weighs. So it must do what SpaceX calls a "hover-slam", and reduce its velocity vectors to 0 at the same moment its altitude gets to 0 in a single burn. Burn too short, you crash, burn too long, you go back up (and then crash.) And the horizontal vectors also need to be very small, and you can't end up too tilted either, or you fall over. And explode, because you're a thin-shelled tube with plenty of fuel and oxidizer still left. Oh, and you have to hit a very small target within a couple meters.
So it's a pretty tricky task. Plenty of rockets can hover these days, but landing a full-sized launch stage coming in from the edge of space is pretty tricky. And they almost got it. Looks like it overreacted just a hair to a gust of wind or something.
Your solution has two problems: (1) it cannot hover and (2) you'd have to design and build and test big robot arms. And put them everywhere you want to land. It's probably easier to make your big robot spacecraft, which you already have, do the landing itself on a plain concrete pad.
Edit: Or maybe 1.5 or 2x! I don't know..
Fingers crossed :)