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Super Heavy has splashed down in The Gulf of Mexico

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Re: Super Heavy has splashed down in The Gulf of Mexico

#251

Post by bagels »

notact wrote: post #250
tocs3 wrote: post #228

Earlier quoted context omitted.

They use the atmosphere to help slow the ship down. It takes most of the tank of fuel to get up there and moving so fast. It would take most a tank to slow down. So, they would need about double the fuel plus some for landing. P.S. I have not done any of the math (I might be able to figure it out but it might take a week or two to figure it out). P.S.S : Maybe if they could refuel in space efficiently (asteroid minin…

I understand the atmosphere is used to slow the vehicle - it's basically free brakes that you don't have to carry with you. I never suggested using rockets in reverse to slow the vehicle down. What I am asking is, instead of effectively standing on the breaks and generating enormous amounts of friction in a short period of time, why can't the vehicle ease onto the breaks and spread the friction out over time so it ca…

They already use a shallow angle. There's just a lot of energy involved. As soon as the drag kicks in, the angle gets steeper and steeper on its own as the drag slows the craft down.

Re: Super Heavy has splashed down in The Gulf of Mexico

#253

Post by mrandish »

Just watched the recorded live stream and... wow! What a show. Incredible views of a test that appears to have successfully achieved all potential objectives through reentry, rotation maneuver, relight, landing burn and upright water landing in the Indian Ocean.

The only unfortunate bit was some debris cracking the camera lens during the last part of reentry so the view for spectators was occluded but SpaceX maintained their live data feed all the way through, which is the important part. As they say, for these tests "the data is the payload."

Re: Super Heavy has splashed down in The Gulf of Mexico

#255

Post by HPsquared »

ryandvm wrote: post #221
api wrote: post #120

Earlier quoted context omitted.

I’ve said for a while that we won’t be ready for the real space age until you can have a rusty pickup in space. What I mean by that is that we have it down well enough that the tech exceeds tolerances and can degrade gracefully. You see this in some sci-fi where there are rust bucket old ships that work.

You have to be careful how much wisdom you glean from fiction. The sheer hostility of space kind of precludes the "she's a good ol' ship" trope. When your door doesn't shut on your pickup, you can bang on it a bit. When your door doesn't shut on your spacecraft, you've got a ship full of corpses that look like a blob fish brought up from the Marianas Trench.

The oceans are very hostile to humans too, really not much less than space, and a lot of ocean-going vessels are rusty hulks.

Re: Super Heavy has splashed down in The Gulf of Mexico

#256

Post by notact »

bagels wrote: post #247
notact wrote: post #217

Earlier quoted context omitted.

Can someone explain why reentry must be so hellish? The energy gained during the rocket burn into orbit must be bled off during reentry, and that energy is enormous. However, why must reentry occur so quickly? It seems if the descent into the atmosphere was slower, the heat shield would be able to radiate the heat energy away more effectively, thus lowering skin temperatures, and significantly reducing the engineerin…

It would take a tremendous amount of fuel to do what you're imagining, probably to the point of making the craft impossible to build with current technology. Your orbit would have to be high enough to do a burn to cancel your orbital velocity (lots of fuel), then you have to burn against gravity for a slow vertical descent (lots of fuel). The rocket equation says... you'll need a larger craft and more fuel to carry t…

I'm not sure why people are misunderstanding my question as "Why not bring more fuel and burn the rockets in reverse". I am simply asking: why not reenter the atmosphere at a shallower angle, spreading the atmospheric braking friction over a longer period of time, which I'd expect would allow more time for the accumulated heat to radiate away before it becomes catastrophic.

Re: Super Heavy has splashed down in The Gulf of Mexico

#257

Post by HPsquared »

mulmen wrote: post #88
thanzex wrote: post #74

Seeing the fin still moving and keeping attitude despite being chewed trough was amazing

As soon as I saw heat on that fin I knew it was over. Then it was… fine? Clearly I’m not a rocket scientist.

It was like that on the earlier test launch with the flying concrete and several failed engines.

Re: Super Heavy has splashed down in The Gulf of Mexico

#258

Post by HPsquared »

krustyburger wrote: post #128

That flap showed the kind of tenacity and courage under (literal) fire we need in our leadership. I hope it will consider entering the presidential race.

Funnily enough, the Simpsons did it:

https://simpsons.fandom.com/wiki/Inanimate_carbon_rod

Re: Super Heavy has splashed down in The Gulf of Mexico

#259

Post by mrandish »

kevstev wrote: post #230
themgt wrote: post #94

Earlier quoted context omitted.

That was seriously some of the most dramatic television I've ever watched. Video of Starship being melted/torn apart by supersonic plasma, the broadcast stream dying multiple times maybe due to ship destruction, then finally back online, peeking through the cracked camera to see the nearly destroyed grid fin STILL ACTUATING. The announcers laughing about the ship being "maybe held together by some nuts and bolts" and…

I have never rooted for a flap so hard, and likely never will. I am ready to buy flap merch. The energy of the SpaceX employees gave me goosebumps, this was great, it was hard not to get caught up in it- you know this is the culmination of years of hard work that is mostly theoretical until tests like these.

Yes, Flappy McFlapFin for the win on that flight!

Re: Super Heavy has splashed down in The Gulf of Mexico

#260

Post by verzali »

93po wrote: post #232
yalue wrote: post #229

Earlier quoted context omitted.

The velocity of a spacecraft in low earth orbit is over 15,000 miles per hour. Smashing into the atmosphere is perhaps the most fuel- and cost-efficient way to slow down to a speed at which landing is possible.

It doesn't really answer the question though. Why not descend slower so that the 15k MPH isn't meeting so much air? And bleed it off much slower so there is less heat

It's hard to do that. What you suggest would mean losing all your orbital speed before you hit the thicker layers of the atmosphere. You could probably do that, but you'd use a lot of fuel to decelerate. And then you are still being accelerated downwards by gravity, so you need something to counter that, which means you need to burn fuel all the way down. All that fuel adds a lot of weight, which cuts down on the amount of useful stuff you can take with you.
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