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Space Elevator

neal.fun

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Re: Space Elevator

#371

Post by LorenPechtel »

ben_w wrote: post #308
adwn wrote: post #275

Earlier quoted context omitted.

> If you somehow manage to get magnetic fields involved, so you are not afraid of friction with the cable itself, at 1.3 max apparent acceleration […] This means that half-way after 58 minutes, the climber is traveling at 0.3 * 9.81 m/s² * 60 * 58 ~= 10.2 km/s ~= 36,720 km/h (!!!) relative to the cable. A tiny imperfection or wobble is going to make the climber crash into the cable, destroying both. A climber with a…

> A tiny imperfection or wobble is going to make the climber crash into the cable, destroying both. A maglev train is several centimeters from the rail; if someone made the carbon nanostructures (the only known material strong enough are atomically precise carbon nanotubes or graphene, but the entire length has to be atomically precise you can't splice together the shorter tubes we can build today) this badly wrong,…

Have you ever seen a megavolt power line? Note how far apart the wires are. They are actually a bit farther apart than they really need to be because it is designed to tolerate a large bird with spread wings, but they still need quite a bit of distance. I believe you can tolerate a closer spacing once you're out in space and have no possibility of a plasma arc.

Re: Space Elevator

#372

Post by LorenPechtel »

ben_w wrote: post #325
adwn wrote: post #312

Earlier quoted context omitted.

> A maglev train is several centimeters from the rail […] No maglev train I ever heard of travels at 36,000 km/h. This is about two orders of magnitude faster. > We already have megavolt powerlines. That's transmission over long distances , but you need to handle and transform all that power in a relatively small enclosure. Have you seen the length of isolators on high-voltage powerlines? What do you think is going t…

> No maglev train I ever heard of travels at 36,000 km/h. This is about two orders of magnitude faster. You think the problem is the speed itself, and not the fact that trains are close to sea level and at that speed would immediately explode from compressing the air in front of them so hard it can't get out of the way before superheating to plasma, i.e. what we see on rocket re-entry only much much worse because the…

Dielectric strength of vacuum is 20kv/inch. Thus your megavolt needs 50 inches of separation at an absolute minimum. And you're operating this in space where you have ionizing radiation. Free electrons with a big voltage differential? You're describing a vacuum tube.

Re: Space Elevator

#374

Post by FiatLuxDave »

hinkley wrote: post #299
jvanderbot wrote: post #143

Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth. In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are clos…

In a parallel universe where Africa is covered by world powers, Mount Kilimanjaro would make a pretty good launch facility. Reduced rocket equation needs for being nearly 3 miles high. If you start in thinner atmosphere you need less fuel to punch through it. You’re also higher when you hit Max Q. This is essentially what Scaled Composites and Virgin Galactic were trying to do with their cargo plane system, only you…

Sounds like the plot of The Dabare Snake Launcher: https://www.amazon.com/Dabare-Snake-Launcher-Joelle-Presby/d...

Re: Space Elevator

#375

Post by neuronic »

mrec wrote: post #115
neuronic wrote: post #95

Congrats, first time I noticeably hear my MBP M4 Pro fans and can feel the temperature through the keyboard. Amazing work, as always. I love neal.fun Edit: also good to know that paper airplanes have officially beat the SR-71, F-104 or X-43B with altitude record.

I dunno, by that rationale you could argue that Tesla Roadsters have officially beaten the X-43B's altitude record, couldn't you?

Yes, absolutely but I found it funny anyway!

Re: Space Elevator

#376

Post by mkl »

243423443 wrote: post #12

I just clicked the temperature thingy in annoyance because I don't use Fahrenheit and to my delight, it just switched to Celcius

Unfortunately that doesn't change the "mph" in the info boxes.

Re: Space Elevator

#377

Post by rich_sasha »

arkmm wrote: post #322
rich_sasha wrote: post #264

Earlier quoted context omitted.

Likewise, it is crazy to me when I realised how thin our oceans are. I used to think of them as super deep (I mean, they are) but even the Mariana trench is a mere 0.2% of the Earth's radius. Average ocean depth is more like 0.05%.

As a follow-up to this, even though water makes up 70% of the Earth's surface, it's only 0.02% of the Earth's mass.

I might have messed it up, but as a follow up to your follow up, I think the depth of the ocean is comparable to the width of a single human hair compared to the head.

If you inflate a 18cm diameter head to the size of our planet, a 75um hair would be about 5km wide - which is about the average depth of our oceans.

It's one hair, not a whole head of hair!

Re: Space Elevator

#380

Post by ben_w »

LorenPechtel wrote: post #371
ben_w wrote: post #308

Earlier quoted context omitted.

> A tiny imperfection or wobble is going to make the climber crash into the cable, destroying both. A maglev train is several centimeters from the rail; if someone made the carbon nanostructures (the only known material strong enough are atomically precise carbon nanotubes or graphene, but the entire length has to be atomically precise you can't splice together the shorter tubes we can build today) this badly wrong,…

Have you ever seen a megavolt power line? Note how far apart the wires are. They are actually a bit farther apart than they really need to be because it is designed to tolerate a large bird with spread wings, but they still need quite a bit of distance. I believe you can tolerate a closer spacing once you're out in space and have no possibility of a plasma arc.

Indeed, I have not, however, I have looked up the breakdown voltage of vacuum at those altitudes, as long as the graph wasn't completely fictional, in that part of space even just 2 cm (barely, but it does) support a megavolt.
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