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Comment by bewaretheirs | Hacker News Reader

First attempt to catch the booster back at the launch site.

The "mechazilla" launch tower has two "chopstick" arms which are used to pick up and stack both stages and which are intended to be able to catch the returning booster and maybe also the returning Starship upper stage.

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> has two "chopstick" arms ... which are intended to be able to catch the returning booster

Do you mean this literally? As in something like Mr. Miyagi catching a fly with chopsticks in the orig Karate Kid?

How could it possibly be meant literally? Do you consider it possible for a rocket to be caught by a literal person with literal wooden sticks?

I guess I don't really understand what you are asking. There's a tower with some huge metal arms that is meant to catch the rocket. They call them chopsticks in a joking manner. Obviously, I would have thought.

>How could it possibly be meant literally? Do you consider it possible for a rocket to be caught by a literal person with literal wooden sticks?

in ordinary English there are many degrees of "literally".

In ordinary English literally is a synonym of figuratively since 2013

https://www.youtube.com/watch?v=4-ImRMJX68s

Yeah I totally envisioned a person holding wooden chopsticks trying to catch a booster /s

You missed the quoted part about > which are intended to be able to catch

Which would be the unique thing to clarify. As in "something like" the "chopsticks" moving to > catch < the thing -- Like Mr. Miyagi moving the chopsticks to > catch < the thing

Main difference (besides scale) is that the booster is cooperating with the chopsticks, navigating to hover at a point between the arms.

Yes, literally, but the arms are massive and not directly controlled by humans.

Yes. The booster has two pins that stick out at the top that are designed to hold the weight of the entire booster when empty. The plan is for the booster to return to the launch tower, position itself between the arms which will close on it and then the pins will “land” on the arms, completing the catch.

I’d say the main difference, then, is that the booster will be supported by those pins resting on top of the arms. Chopsticks use friction to hold up their load.

yes the booster’s structure is very strong vertically but not nearly as strong horizontally. There may be some “squeezing” forces from the chopsticks but this is effectively for fine positioning only. It will not support the weight. The booster will “land” by getting its pins (which stick out a bit) on the top rail of the arms.

Thanks for the explanation! That makes it much more interesting than simply another launch

The arms are also used to lift the rocket onto the pad, so can carry the full weight, not "just" the empty.

The rocket is not filled until the last minute, by fueling arms on the tower. And the weight is like 90% fuel, so it makes a pretty big difference.

It should be better described as having the booster land on the arms. The arms will probably be able to adjust a little to assist in alignment, but the booster is doing most of the work to be 'caught'.

They do have to be wide open and close pretty fast once the end on the booster had passed them.

What benefit does catching the booster provide? (Or, what's a good written guide to that system?)

Don’t need landing legs/gear on the ship. Saves weight

It allows removing the landing gears on the booster, which saves wheight, which saves fuel, which increases efficiency and reduces costs. It also avoid having to fetch the booster from wherever it would have landed.

What others said is true, but I think the endgame is also to literally land on the launchpad, allowing for a quick turnaround.

Given that a lot of the landing failures we've seen started with a near perfect landing followed by the rocket tipping over, I suspect one benefit is that the contact point is now above the center of gravity and thus it can't really tip over.

Of course, it can't tip over unless something fails or the rocket ends up in the wrong spot (and fails to get caught) and the previous tip-overs also had to involve failures (of the landing strut, in the latest loss) or landing in some way that isn't perfectly aligned.

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