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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]

#401

Post by christophilus »

wildzzz wrote: post #376
arijo wrote: post #323

Earlier quoted context omitted.

> Another interesting thing SpaceX is doing is to use consumer-grade chips in triple redundancy configurations instead of using $100,000+ radiation-hardened aerospace/defense grade chips. This has been known in the high availability and safety systems industry for a while and a good book to learn these reliability engineering techniques is "Reliability Evaluation of Engineering Systems". The book is available on amaz…

One downside of using non-rad hard parts is degradation from TID (gamma) and latch up effects. You can have chips monitoring other chips to reset whenever they latch up but TID is mostly permanent. The good thing is that TID in LEO, where SpaceX mostly operates, is relatively lower than GEO so they can get by with mostly commercial parts. It's not like the big defense contractors haven't figured out the same thing, t…

Could you surround your components with gamma-shielding materials and get away with off-the-shelf parts deeper in space?

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

#402

Post by HPsquared »

KORraN wrote: post #239
monkeydust wrote: post #105

Earlier quoted context omitted.

Watched several times, amazing stuff. Had flashbacks to playing Jupiter Landing on the C64! https://en.m.wikipedia.org/wiki/Jupiter_Lander Edit: SpaceX should create a simple 'catch' the rocket game. Play in browser style. Just for kicks and marketing.

This one is not from SpaceX, but gives way more fun: https://mechazilla.io/

That's great, really shows how they are "threading a needle" on the control side of things.

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

#403

Post by ErneX »

flaburgan wrote: post #76
treespace8 wrote: post #14

I'm just so happy to see this level of progress. This another big step for opening up space. To think that one day this will be considered normal. 150 Metric tons sent on a fully reusable rocket. Thats like a 747 to space.

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?

The boosters were not (or at least not with the quick turnover and lower costs like the ones from SpaceX)

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

#404

Post by avhon1 »

skizm wrote: post #252

This was insanely cool to watch. And on the first try! As a complete lay person with little to no physics knowledge: what stops the use of something dumb like a parachute, or even wings and landing gear, to "land" the booster? I assume it is impractical (since they don't do it), but what are the actual particulars that stop it from working? While super cool to watch, it seems crazy that plucking it out of the air lik…

Parachutes give little or no control over where and how the rocket lands, are unreliable (unfurling fabric behaves chaotically; modern spacecraft still don't have 100% reliability on their parachutes), and are surprisingly heavy.

Wings and landing gear are useless extra weight during launch, and excess weight on the booster has a super-linear reduction weight delivered to orbit. (the Tyranny of the Rocket Equation)

During the 1960s, NASA investigated using inflatable Rogallo Wings (basically hang gliders) to land the Gemini capsule. It worked fine, but was more complicated than parachutes, and re-use was not one of the goals of the Gemini or Apollo programs.

None of those give much margin for error on landing. Without any kind of propulsion, there's no option to come to a hover or do another go-around if the landing isn't going well. Space Shuttle pilots had to do extensive training in simulators for the landing because they only got one shot at it during the mission.

Propulsive landing doesn't require any hardware that isn't already on the launch vehicle, only a little excess propellant. (And it is a small amount; Super Heavy is like a soda can that's full of liquid at launch and only has a swig at the bottom during landing.) Propulsive landing gives Falcon 9 and Super Heavy the ability to overcome wind and other weather conditions to make pinpoint landings. Engine throttling gives Super Heavy the ability to hover, so it has a huge margin for error when coming in for a landing.

Super Heavy could have had legs, like Falcon 9, but it has such a huge payload capacity that they can simply choose to always launch with enough propellant to come back to the tower, and it saves a lot of flying weight and complexity by simply not having them. The arms on the tower can be massively overbuilt to ensure however much reliability SpaceX wants.

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

#405

Post by skrebbel »

stetrain wrote: post #295
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)

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 re…

Thanks!

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

#406

Post by skrebbel »

Denvercoder9 wrote: post #130
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)

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 th…

Thanks!

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

#407

Post by jjk166 »

drexlspivey wrote: post #230
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.

The booster was falling at 4500 Km/h 30 seconds before the catch with 2-3% fuel left. How is that amount of fuel remotely enough to stop the downward momentum?

Note that the energy of 3% of the propellant (~100 GJ) could theoretically get the empty booster (100,000 kg) to a little over 5000 km/h if properly applied.

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

#408

Post by JumpCrisscross »

Culonavirus wrote: post #357
rvnx wrote: post #346

Earlier quoted context omitted.

Edited: Was asking what were all these deleted comments. Got my answer: it's a theory that SpaceX is a partner for the US DoD and is not just an internet provider.

[flagged]

> What the f is going on in this

Genuinely curious if you find an answer.

My first thought was nuclear anxiety; it’s nice to feel like we have a secret shield in space. Then I saw Trump talked about it, so my current hypothesis is the partisan parroting that happens on both sides. (Or if someone doesn’t like military spending, maybe it’s an anti-Musk thing?)

That said, the three accounts that have been posting about it seem to really like this topic [1][2][3], so maybe it’s a niche thing. They all seem to really like one Reddit thread.

[1] https://news.ycombinator.com/threads?id=forgot-im-old

[2] https://news.ycombinator.com/threads?id=tbone902

[3] https://news.ycombinator.com/threads?id=georgeg23

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

#409

Post by mlindner »

bjamesking wrote: post #362

I was watching a youtube stream with tens of thousands of viewers and 20 seconds before launch it switched to an AI generated video of Elon on stage talking about his "crypto currency program". It was so well executed and generated, it nearly felt real. The violent anger I felt and still feel for scammers has ruined my day.

They do this every launch unfortunately. Youtube seems completely inept at stopping them. They make enough money to hire hundreds of thousands of fake accounts to subscribe.

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

#410

Post by shoxidizer »

flaburgan wrote: post #76
treespace8 wrote: post #14

I'm just so happy to see this level of progress. This another big step for opening up space. To think that one day this will be considered normal. 150 Metric tons sent on a fully reusable rocket. Thats like a 747 to space.

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?

You've got a lot of responses on the difference of reusability, but the shuttle was also more expensive because it had to carry a lot of capabilities with it every time. If you were launching a satellite, you were carrying along the crew compartment and a couple astronauts. If you were bringing a few astronauts to the space station, you brought a cargo bay. And in either circumstance, you brought big wings. Starship can be filled with all cargo. And if you're just changing crew on the ISS, you could... not use Starship and launch a Falcon 9 instead. One of the mission profiles required by the Air Force for the shuttle was that it be able to rendezvous with a satellite, put it in the cargo bay, and return to Earth, all under 2 orbits and along a path that avoided flying over the Soviet Union, which required a rather large turn in-atmosphere to make it back to landing on the west coast.
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