Hacker News Reader

Comment by skrebbel | Hacker News Reader

Can someone explain to me why this is more impressive than landing the rocket? To a layman like me, it looks very similar - the thing looks just like a rocket but without a pointy tip, and on the way down I don't understand why difference that matters.

(I mean I still think it's mind blowing, because I think landing a rocket is also mind blowing)

View on HN

(1) Much larger than any previous rocket landing, (2) This rocket carried no landing gear (more efficient - landing gear is heavy), (3) This rocket landed right back at the place it needs to be to launch again - right on its launch tower - which in a routine situation might make it much faster to prepare it for the next relaunch. (4) It's yet another step in control prowess - impressive in itself.

I must say though "right on its launch tower" is fun and all...

but things would have to get pretty extreme in the "routine" dimension for that to be very useful. If there are 20 first stages and 5 land/launch towers, for a first stage that only spends an hour in flight in between inspections.... well are you going to keep them parked on a scarce launch tower for maintenance? The towers with fill/launch infrastructure (such as reinforced concrete, fuel tanks, cold filling system, deluge water system) become the bottleneck. It's more likely then that the 1st stage lands, is safed, then is taken a couple hundred yards away for inspection and maintenance while the next in line is moved to be stacked for the next launch. The inspection / maintenance would have to be truly minimal (think airliner) to keep it right there on its own relaunch tower.

"No landing gear" is more key, compared to Falcon 9 - because of the effort toward minimal launch cost.

> The inspection / maintenance would have to be truly minimal (think airliner) to keep it right there on its own relaunch tower.

That's what they are aiming for, eventually.

Thanks!

It is a rocket. The biggest difference with the Falcon 9 first stage is that this one is about 6 times as big (diameter of 9m vs 3.7m), and that catching it with the tower requires a much higher precision in landing location. The drone ships that Falcon 9 lands on are about 90 x 50 meter. To catch it with the tower, they need to be accurate to within a few meters.

The big advantage of catching it with the tower is that it'll (eventually) allow them to put another Starship on top, refuel and launch again within hours, as opposed to the weeks it currently takes for Falcon 9.

The critical differences between Falcon 9 first stage and the Starship booster is that Starship booster lands using 3 engines rather than 1, and can throttle them down much further. 3 vs 1 gives Starship more directional control for precise landing (critical for this "catch" maneuver), and throttling allows it to hover, as it does right before the "catch".

Falcon 9 also lands using 3 engines on its most demanding missions. The throttling is definitely an advantage.

But as far as I know, one Merlin engine produces more thrust than the empty booster weighs which means they have to time things perfectly to get to zero velocity exactly at the ground.

Super heavy can hover and even go down by throttling down more. This gives them more control for the landing and don’t have to time it exactly perfectly

Thanks!

The tower is also how they plan to perform maintenance and re-staging for another launch. The tower can place it back on the launch structure or lower it down to the ground if it needs to be transported back to an enclosure for extensive repairs but a lot of work is just done with it at the tower. I imagine the goal is to eventually get to an automated system that catches the booster, inspects it for damage, clears it for relaunch, positions it on the launch structure, grabs another Sharship second stage and stacks it and then refuels the whole system and launches as soon as possible.

Plus it's really big https://images-bonnier.imgix.net/files/ill/production/Starsh...

This booster is significantly larger than anything landed on an orbital launch before. Here is a size comparison, previous largest landed orbital rocket stage is the SpaceX Falcon 9 (three of them launch together as Falcon Heavy) on the left. Starship is on the right.

https://upload.wikimedia.org/wikipedia/commons/7/7b/SuperHea...

Landing via tower catch versus on a pad is advantageous because the weight of adding retractable landing legs to such a large rocket would be significant.

Thanks!

This method doesn't require landing legs on the rocket, allowing their weight to be used for payload instead

It’s also already on the tower that it launches from, which drastically reduces the expense and complexity of setting it up for its next launch, making it easier and faster to reuse.

To expand on this, landing legs of Falcon 9 weigh two tons. Landing legs of SuperHeavy booster would have to be even more formidable.

Which means that the weight savings are nontrivial with the "catch the rocket!" landing method.

From what I understand, it reduces the turnover dramatically. In theory the booster should be refuelled, new second stage mounted on top and ready to go for another flight. So could cut down from weeks to days/hours. That's significant.

It's more precise than landing on the ground, there is coordination with the tower required, it is way bigger than Falcon 9.

This video goes into details pretty well: https://m.youtube.com/watch?v=OYvWYp0--bQ&t=832s

I think landing a booster is just as impressive. It's just that nobody's done this before, so it's exciting! Plus it's a lot bigger and part of a fully reusable config which has huge implications for space travel.

This one seems way harder than the others which land on legs and on a relatively larger circular landing pad, this one needs to nail the tower and its arms.

Reply on news.ycombinator.com