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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]

#491

Post by modeless »

timeon wrote: post #168
paulryanrogers wrote: post #155

Earlier quoted context omitted.

Improvements that make space flight more sustainable are welcome ... unless that means an order of magnitude more pollution in a less controllable form, like emissions. [Due to more frequent flights] Daily trips to space likely also mean more debris in space and falling to earth. I hope there is a balance that includes the lives of people near these sites and all of us sharing the same atmosphere.

I hope this is not going to be used for 'Earth point A -> Earth point B' travel.

SpaceX proposed it but I doubt there is any chance of this architecture ever achieving the airliner-level reliability needed for people to accept routine Earth-to-Earth passenger service. That's several levels beyond what you'd need to fly astronauts.

Maybe a future architecture with more redundancy could get there someday.

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

#492

Post by erikerikson »

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-…

I have been told by people who worked on them that you get radiation hardened aerospace/defence grade chips by backing off the clock speed about 20% to give signal stabilization slightly longer time. I can understand the population being confused about this but industry being confused seems to have more to do with regulatory capture and beaurocratic moats which SpaceX does seem to be bypassing.

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

#495

Post by rsync »

magicalhippo wrote: post #354
drexlspivey wrote: post #230

Earlier quoted context omitted.

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?

First off, the booster was going about 1250 km/h when it started its landing burn, it relied purely on drag to get it slowed down to that speed. Going by the telemetry of the seconds before the landing burn and noting the speed vs time, it seems drag was around 40 m/s^2 when it was going at around 3000 km/h. Since drag depends on velocity squared though, it had reduced to just above 10 m/s^2 just before the engines l…

"... Super Heavy[1] has 3400000 kg of fuel at launch ..."

So, 34M kg of fuel has to be burned (in this booster alone) to facilitate a flight ... and I see that the propellant is CH4 / LOX[1].

Burning methane is much, much better than simply releasing methane but the release becomes CO2 instead ...

What is the back-of-the-envelope conversion of 34M kg CH4 vs., for instance, 34M kg of kerosene/JP ?

[1] https://en.wikipedia.org/wiki/SpaceX_Super_Heavy#Engines

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

#497

Post by blisterpeanuts »

blackeyeblitzar wrote: post #245
ptek wrote: post #52

Very inspiring, glad I woke up to watch it. Congratulations to the SpaceX team. This is what competition looks like. It’s funny how last decade SpaceX had to sue the government to get more launches.

Well that may still continue to happen. The wonderful and competent state of California is literally trying to block SpaceX launches over Musk’s constitutionally protected political speech: https://www.politico.com/news/2024/10/10/california-reject-m... I cannot remember a more explicit case of authoritarian government abuse in a developed nation in recent memory, and it’s especially infuriating given SpaceX and Musk…

It is a state commission composed of political appointees. It's unlikely it has the jurisdiction over Vandenberg to ban any activities, except when such activities violate state environmental laws. Even then, the federal government might be able to override them. It will be interesting to see what comes of this.

Ideally, the commission will withdraw its objections and allow the launches; SpaceX obviously chose this site both for its proximity to the Pacific Ocean and for redundancy in case of poor weather in Florida (like this past week for example).

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

#498

Post by h_tbob »

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)

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.

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

#500

Post by oldpersonintx »

WalterBright wrote: post #479
philistine wrote: post #352

Earlier quoted context omitted.

> Other companies should have reusable boosters soon You're way too optimistic. Starship will deliver commercial payloads, with SpaceX phasing out Falcon 9 outside of ISS launches, before anyone has a reusable Falcon 9 equivalent. It pains me to say this, but SpaceX is in a class all its own.

Why does it pain you? Musk's SpaceX has produced several enormous advancements in space technology. SpaceX is one of the greatest, if not the greatest, private technology company in history.

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