[w_t_payne]

If we can land the rocket accurately enough to put it down on a tiny barge only slightly larger than the rocket itself, then why do we need to tolerate the weight of the landing legs?

We already have industrial robots that can move and grasp heavy weights relatively quickly over distances of several metres -- it doesn't take much imagination to conceive of a similar contraption being used to arrest the descent of the rocket over the final few tens of metres of its' descent - a sort of brobdingnagian robotic catcher's mitt.

Granted, this might be a bit on the expensive / elaborate / bizarrely over-engineered side -- but it would look utterly awesome.

[ggreer]

There are several reasons why landing legs make more sense:

– Any flat chunk of cement is a landing spot. That means more places to land in case of contingencies. For yesterday's mission, SpaceX had one primary and four alternate landing zones.[1]

– I doubt industrial robots can withstand rocket exhaust. As helicopter footage shows, the landing pad got lit-up pretty good.[2] Remember, the first stage is over 40 meters tall. Those are some massive flames.

…and most importantly:

– Landing legs work on other planets.

1. Map: http://www.americaspace.com/wp-content/uploads/2015/12/LZ1.j... (from http://www.americaspace.com/?p=89910)

2. https://www.youtube.com/watch?v=ZCBE8ocOkAQ

[w_t_payne]

Who cares about what makes more sense ... giant robots, dude! :-)

[grecy]

Every time these discussions come up, people immediately come up with "other" suggestions for landing.

Parachutes, "catching" devices, etc. etc.

It all comes down to one thing, and one thing only.

Whatever the solution, it has to work on other planets with no infrastructure on that planet, and it has to leave the booster in a state that it's ready to go again with only a fuel fill up.

[mcbutterbunz]

I was under the assumption the primary reason is reusability on earth only. This would drastically reduce the cost for building new rockets and would decrease turn around time for new launches. Having it work on other planets is a nice plus but there's no demand for that and likely wont be for decades.

[grecy]

> Having it work on other planets is a nice plus but there's no demand for that and likely wont be for decades.

Elon has made it very, very clear and continues to reiterate.

The entire purpose of SpaceX is to get to Mars.

Launching satellites and other near-earth stuff is nothing more than a needed step to achieve the goal.

[w_t_payne]

... or (as a less mechanically complex solution ...) use the same concept as the arrester cables on an aircraft carrier flight deck -- but upended to catch a vertically descending vehicle.

(No flight deck required -- just cables suspended between two towers and an arrester hook at the top of the rocket -- which just has to be lighter than folding legs at the bottom).

[mrfusion]

That's a great idea. But I think they want something really general purpose that can land anywhere and possibly even on Mars.

Also the empty rocket might be too weak to be grabbed by anything. They compare the thickness to a tin can.