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Starship Flight 5: Launch and booster catch [video]

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Re: Starship Flight 5: Launch and booster catch [video]

#561

Post by lutorm »

jader201 wrote: post #298

Can I hijack this thread for an almost completely unrelated question that I have observed in nearly every simulation of movement in space, even from sources like NASA and SpaceX which “should know better”? And I’m mostly asking this out of scientific curiosity, not as a criticism. Why do they always portray movement in space by showing stars moving past the view at variable rates, or even at all? The opening screen o…

As others have said, you're correct. But one reason for doing this, beyond just looking cool, is to give a visual cue for motion. The aim isn't primarily to look realistic, but to make it as easy as possible to interpret the outputs. Motion cues help with this.

As an example, if you're watching an airshow against a clear blue sky, especially filmed with a long lens where you can't see the ground, it is very hard to understand what's actually happening because you can only see attitude changes, but not the velocity vector. Add just a few clouds in the background and the impression is very different.

Re: Starship Flight 5: Launch and booster catch [video]

#562

Post by nilsherzig »

afh1 wrote: post #383
nomilk wrote: post #212

Earlier quoted context omitted.

10 minutes from 3h25m of this video shows launch and catch. Historic viewing :) https://www.youtube.com/watch?v=YC87WmFN_As&t=3h25m14s

This angle is even more impressive IMO https://x.com/kimbal/status/1845451222750306344

It's very impressive to see the buildings next to it, the original video lacks any sense of scale

Re: Starship Flight 5: Launch and booster catch [video]

#563

Post by fpoling »

fastball wrote: post #367
flaburgan wrote: post #76

Earlier quoted context omitted.

So, reusable is supposed to reduce the cost. But the space shuttle was reusable and it has been shutdown because it was too expensive. What is the differences between the two?

Shuttle itself was refurbishable, but not rapidly re-usable. It was also incredibly expensive to build and refurbish. A shuttle launch also utilized boosters that were not re-usable. Starship is supposed to be (and clearly well on the way to being) fully rapidly re-usable . That means all stages (in this case two) are re-usable, and that the capital and time required to get either stage flight ready again after a fli…

The boosters for the Shuttle were reusable, but it turned out the cost of refurbishing them was similar if not higher than simply building new ones. Plus it contributed to the Challenger crash, see "Mr. Feynman Goes to Washington", https://calteches.library.caltech.edu/3570/1/Feynman.pdf

Re: Starship Flight 5: Launch and booster catch [video]

#564

Post by schiffern »

dtquad wrote: post #183
ghc wrote: post #23

Nothing could have prepared me for how that catch looked. I was sure the rocket was careening into the tower at the last second before it straightened out. The control algorithms must be incredible for the landing system to work within those small tolerances.

MIMO and nonlinear control theories are probably some of the hardest topics in all of engineering. SpaceX control system also has to compensate for the fuel moving inside their rockets so the control algorithms probably involve some kind of fast numerical fluid simulation. Another interesting thing SpaceX is doing is to use consumer-grade chips in triple redundancy configurations instead of using $100,000+ radiation-…

  >probably involve some kind of fast numerical fluid simulation
Sometimes even a simple approach can work. On Apollo they developed (at the time cutting-edge) passive RC filter networks, to avoid the control system "exciting" the rocket at frequencies of the slosh/bend/torsion modes.

https://ntrs.nasa.gov/api/citations/19700023342/downloads/19... (search for "slosh" or "shaping network")

Re: Starship Flight 5: Launch and booster catch [video]

#568

Post by creer »

creer wrote: post #316
skrebbel wrote: post #123

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)

(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.

Re: Starship Flight 5: Launch and booster catch [video]

#569

Post by cryptonector »

shirro wrote: post #199
teractiveodular wrote: post #19

It's difficult to overstate how important the milestone of catching the booster is. Now we have a reusable rocket an order of magnitude larger than anything we've had before, and the cost of kg to orbit just nosedived.

Second stage reuse seems the far more challenging problem. Other companies should have reusable boosters soon but if significant amounts of Starship continue to ablate on the way down they could be faced with a disposable Starship competing with smaller and cheaper second stages that are well sized for typical payloads. We already knew boosters can be flown back to launch sites reliably with high accuracy. We don't k…

> Second stage reuse seems the far more challenging problem.

Sure, SpaceX has been doing first stage reuse for a long time now. But they have demonstrated landing the second stage successfully at sea twice now with the same sort of smoothness that they demonstrated once for the booster before they then caught the booster on the first real try.

A partial list of unbelievably hard things that SpaceX has so far made seem easy:

  - building a rocket from scratch
  - landing Falcon 9 boosters
  - landing Falcon 9 boosters *reliably*
  - 3x weekly launch cadence (Falcon)
  - the bellyflop manoeuver
  - mass manufacturing(!) a rocket engine
  - catching the booster
  - simulated landings of the ship
Catching the booster is really just like landing a Falcon 9 booster w/o legs, but clearly much harder.

Anyways, if they can do all those things then it's pretty clear that they can catch-land the ship.

There's still a huge list of crazy-difficult things that SpaceX say they want to do that are hard to believe are possible, except for the fact that SpaceX has already done so many unbelievably difficult things already.

Re: Starship Flight 5: Launch and booster catch [video]

#570

Post by spacesanjeet »

diebeforei485 wrote: post #472
moffkalast wrote: post #336

Earlier quoted context omitted.

Well I mean going to Mars isn't that hard per se, a fair few countries have done it... but carrying enough supplies and shielding to last people 2 years until the return trip and then actually getting back are way harder problems. Seeing Starship get burnthrough on these suborbital launches really shows how hard it'll be to do Mars return entry with a fair few extra km/s.

Only the US and China have landed successfully on Mars. China achieved this in 2021. Russia/USSR tried multiple times and didn't succeed. Other countries have sent satellites to orbit around Mars, which is not the same thing.

I think that the number of countries reaching Mars (lander or orbiter) is in single digits and thus when talking about how hard it is to reach Mars and then come back, both of the scenarios kind of hold similar weights.
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