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Lord_Parbr t1_ixy8dqi wrote

The idea of something tethered to Earth and extending out into space, especially if it’s tethered on that end to something in orbit triggers my anxiety, and it doesn’t even exist yet

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grat_is_not_nice t1_ixy9zl1 wrote

It is actually tethered to a counterweight that is beyond geosynchronous orbit. The center of mass of the entire elevator system is at about geosynchronous orbit level.

In Arthur C Clarke's The Fountains Of Paradise, a space construction engineer dies after stepping off the counterweight, because it is not in orbit. If you step off something in orbit, you stay in the same orbit and rescue is trivial. If you are not in a stable orbit, you are going to have a completely different trajectory that will either end up hitting atmosphere or escaping (depending on the non-orbit you start from).

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Lord_Parbr t1_ixybti1 wrote

It’s not so much the possibility of death that makes me anxious. It’s the idea of some massive structure that is extending from the Earth out into space. Just the very idea of a massive tube sticking out of the planet as it spins, however slowly. It’s completely irrational. I get the same feeling when I can hear 2 different songs playing at the same time

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DGolden t1_ixyli1o wrote

> It’s not so much the possibility of death that makes me anxious.

I mean maybe it should? What happens when the damn thing breaks? whether by accident or terrorist attack, it could fail.

https://www.wired.com/story/what-happens-if-a-space-elevator-breaks/

> So, what's going on? Notice that the lower part of the cable just falls to Earth and probably causes some severe destruction. In this model, it wraps about a third of the way around the equator, even though its full length would almost make it all the way around the Earth, which has a circumference of 40,000 kilometers.

It may be that I actually qualified as an engineer a long time ago so was taught to be extremely pessimistic (or realistic, there are so many ways innocent-looking stuff can turn you into meaty chunks) about how damn near everything we make can suddenly fail and kill everyone, but I'm certainly very wary of the whole space elevator idea. It's cool, but also ... things go wrong. Would need a more detailed simulation than some back-of-the-envelope wired article, but still.

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danielravennest t1_ixyryor wrote

I'm an actual space systems engineer. Any illustration you see of a single cable going up from Earth is wrong. Earth orbit is filled with artificial debris, and the rest of space has natural meteoroids. You see those as meteors at night as they hit the atmosphere and burn up.

So any large space structure will get hit by stuff. In fact, both the Space Shuttle and Space Station have taken hits, fortunately not a big one.

But a 60,000 km space elevator will have a lot of exposed area to take hits. At orbit speeds, everything turns to plasma and makes a crater. A big enough crater cuts the cable.

The only way to design something like this that lasts is to have many cable strands, and space out the strands so they can't all be cut at the same time. You can build it in segments with load sharing. Then impact damage (which WILL happen) means replacing one broken segment of one strand, which is a maintenance task.

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Twister_Robotics t1_iy04ctm wrote

This is the way.

Not a single cable, more likely a truss like structure oriented vertically, with the load carrying members at the corners tied together diagonally to share the load in case of failure.

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IvorTheEngine t1_ixyif7m wrote

In Red Mars a space elevator on Mars is sabotaged, and it is long enough to wrap right around the planet when it falls...

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