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Starship Prototype Unveiled

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Re: Starship Prototype Unveiled

#111

Post by elif »

hinkley wrote: post #106
Blakestr wrote: post #97

Earlier quoted context omitted.

Not a metallurgist but doesn't tempering make steel stronger? (As long as it is quenched properly?)

Tempering is used to reduce brittleness in metal. But I think the word GP was looking for was annealing. Annealed metal bends quite easily (that's the analogy in 'simulated annealing' in optimization theory). For instance the wire bonsai practitioners use is traditionally made of annealed copper. Copper is already pretty ductile but once annealed it's positively floppy. Bending it work-hardens it, causing it to stiff…

Tempering is the correct terminology. Annealing is a slow and controlled heating, gradually reducing the heat over time.

from Wikipedia:

"Tempering [...] is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air."

Here's a good description https://www.metalsupermarkets.com/difference-annealing-tempe...

Re: Starship Prototype Unveiled

#112

Post by hinkley »

extrapickles wrote: post #72
mattlondon wrote: post #66

Earlier quoted context omitted.

I am totally with you on this - I just can't get over how utterly rudimentary and basic this thing looks! I can't wait to see it fly! I am so used to seeing space stuff done in clean rooms, and things taking years and years to come to fruition (e.g. hearing about and seeing NASA or ESA probes etc getting made) that to see what is essentially a bunch of guys in a field just welding something together blows my mind. I…

I suspect most of the structure that gets really hot or cold is steel. To save weight, they are probably also letting more of the rocket get colder/hotter than normal, thanks to the wider temperature range of steel. Once the temperatures get reasonable, it might be aluminum or or carbon fiber. The passenger/cargo/avionics section are probably the only areas where this would be true, so a bulk of the rocket will be st…

Steel can tolerate a lot more deflection before it bends, and much more stress before it cracks. And while I would never expect a space craft mechanic to employ this technique, any bike mechanic will happily offer to bend steel back into shape for you, but bent aluminum or carbon fiber is scrap. Bending it back will fracture it, if it hasn't already.

When Canondale hit the big time, they had one model year where they made the dropouts out of solid aluminum and in the next model year the derailleur hanger was bolted on. It's the easiest part to bend and there's no repairing it. Bad enough for road bikes, spectacularly dumb for mountain bikes.

Re: Starship Prototype Unveiled

#113

Post by ben_w »

DennisP wrote: post #43
hwillis wrote: post #24

Earlier quoted context omitted.

SpaceX is completely changing the opportunities of getting to space. The reduction in price has been nuts. According to NASA the space shuttle was ~$450 million per launch, or $16,364 per kg to LEO. The Delta 4 Heavy is $12,156 per kg. For some launches it's even higher- the Air Force paid $15,109 per kg for four launches. The Falcon 9 is $62 million, or $2,719 per kg to LEO. The Falcon Heavy is $2,351 per kg when ex…

It's the dawn of the true space age. And though Musk isn't a fan, this could even make solar power satellites economical. The monolithic designs from the 1970s would be absurdly expensive, but modern designs like SPS-Alpha get economies of scale by using lots of small identical parts that self-assemble in orbit. According to the book The Case for Space Solar Power , a 2GW satellite would deliver electricity at 15 cen…

Geostationary orbit is further away than the most distant part of the Earth. If you have a way to transmit power efficiently over that distance, it’s still going to be cheaper to put the panels on the ground in Nevada, the Sahara, Saudi Arabia, the Gobi, and Australia, and transmit the power from there. (Microwave towers, LEO satellite relays, superconducting wire, whatever).

It’s likely to be really hard to make it efficient to transmit the power, because either it will be microwaves or it will be lasers; lasers can be blocked by clouds, microwaves need an huge antenna at each end (the numbers I’ve seen say that the one on the ground has to be big enough that people will ask why you’re not just using building a PV solar array on the ground instead of the antenna). If the antenna isn’t big enough, transmission losses from beamed power is proportional to distance squared, whereas resistance loss in wires is only proportional to distance (P = I²R, R = distance * some_design_specific_number Ω/m).

And that’s without the geopolitical implications of anyone worrying if the enormous directed microwave/laser source could be weaponised. Just saying “trust us” isn’t going to be good enough.

Re: Starship Prototype Unveiled

#114

Post by hinkley »

balfirevic wrote: post #73
mattlondon wrote: post #66

Earlier quoted context omitted.

I am totally with you on this - I just can't get over how utterly rudimentary and basic this thing looks! I can't wait to see it fly! I am so used to seeing space stuff done in clean rooms, and things taking years and years to come to fruition (e.g. hearing about and seeing NASA or ESA probes etc getting made) that to see what is essentially a bunch of guys in a field just welding something together blows my mind. I…

> Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside? Nope, it's just steel. Outside shell is the tank.

I recall quite a while back, when titanium started first showing up outside of aerospace, that someone had created a titanium-titanium composite by layering plate titanium with titanium cloth and welding it together somehow. Was supposed to be stronger. Wonder if there's a steel equivalent possible.

I think the military was looking at a similar material to replace depleted uranium with something non-radioactive (depleted uranium still experiences alpha particle decay, which is fine if you don't aspirate or ingest it, but a shell can pulverize on impact with a target. Also it's still a heavy metal even if you don't take rads from it).

Re: Starship Prototype Unveiled

#115

Post by AimForTheBushes »

afterburner wrote: post #110
drchewbacca wrote: post #89

I am so amazed by the genius of making it out of steel. It's just so completely counter intuitive but has accelerated their progress so much. If they told you the stats of the material, better strength at cryo tempertures meaning mass reduction, higher melting point meaning minimal heat shielding and great thermal conductivity it would be easy to imagine it was some new super composite. Then your head explodes when t…

> Imo Elon is starting to get into contention for greatest engineer of all time. I don't know man, did he design it himself?

Is there any reason to believe it would be happening now if he didn't exist?

Re: Starship Prototype Unveiled

#116

Post by aperrien »

hwillis wrote: post #24
martythemaniak wrote: post #21

That was a very dense an informative presentation last night, but I think the main take away is that rapid reusability is a game changer. In fact, game-changer is probably an understatement, basically every intuition and rule-of-thumb we have about space launches and travel will have to be rethought. And this will be true even of SpaceX falls well short of meeting their stated targets (2020 orbit, 150t capability, mu…

SpaceX is completely changing the opportunities of getting to space. The reduction in price has been nuts. According to NASA the space shuttle was ~$450 million per launch, or $16,364 per kg to LEO. The Delta 4 Heavy is $12,156 per kg. For some launches it's even higher- the Air Force paid $15,109 per kg for four launches. The Falcon 9 is $62 million, or $2,719 per kg to LEO. The Falcon Heavy is $2,351 per kg when ex…

$50 a kilogram makes it almost cheap enough that immigration to the moon would be practical. Certainly if a large enough group wanted to band together and pay for the launching of their own infrastructure and passenger rides, they could do it. Forget "just" the start of a new Space Race. This would be the opening of the space version of the Oregon Trail!

Re: Starship Prototype Unveiled

#117

Post by hinkley »

tlb wrote: post #71
rout39574 wrote: post #25

Earlier quoted context omitted.

Think of it like a paper towel tube. It's a spiral. Single helical weld.

Spiral tube are a bad choice for a rocket. Because rolled steel has the grains largely aligned with the direction of rolling, it is stiffer and has less thermal expansion in one axis than the other. Large forces and temperature changes therefore cause a twisting motion, which can put weird strains on the internal components.

Pillsbury rolls come to mind. The tube is under pressure from the leavening agent, and you apply torsion on the tub until the can ruptures along the spiral seam.

Re: Starship Prototype Unveiled

#118

Post by m0zg »

JulianMorrison wrote: post #42

1950s Science Fiction illustrators are feeling so vindicated right now.

For real. I wonder how much innovation really exists because the engineers have read golden age sci-fi 25-40 years ago as kids. Could be also that human aspirations are predictable, but I do believe this link should not be ignored. Musk himself acknowledges it some by naming Space X barges after sentient spaceships from Iain M Banks "Culture" series. Or maybe not Musk himself, but whoever named the barges.

Re: Starship Prototype Unveiled

#119

Post by 35787 »

hwillis wrote: post #22
35787 wrote: post #15

Eventually the shell will be a single large roll of steel that is unrolled, bent into a tube with a seam going hotdog that is welded. It will be very strong, lighter than the current patchwork, and extremely beautiful. More similar to the renderings. Can’t wait.

Definitely not hotdog (assuming that's from stem to stern). Musk wasn't totally clear when describing it, but he said mk3 would be in three months. The circumference of starship is 28.26 meters. For a single weld the entire length of the ship, the roll itself would need to be that wide. The largest rolling mills in the world are ~4 meters wide[1]. They require backup rollers[2], ie rollers that push down the rollers…

Wow what an incredibly substantive comment. I remember pretty clearly he said that there would be a single seam weld. Maybe I’m remembering wrong. Or maybe they’ll seam weld multiple rolls into a really wide roll and the only weld required to turn the final roll into the shell is that final hotdog weld.

Re: Starship Prototype Unveiled

#120

Post by SomeOldThrow »

drchewbacca wrote: post #89

I am so amazed by the genius of making it out of steel. It's just so completely counter intuitive but has accelerated their progress so much. If they told you the stats of the material, better strength at cryo tempertures meaning mass reduction, higher melting point meaning minimal heat shielding and great thermal conductivity it would be easy to imagine it was some new super composite. Then your head explodes when t…

Steel has been used before.
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