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TheImmortalLS t1_ixy6xy9 wrote

Reply to comment by fitzroy95 in Space Elevators Are Less Sci-Fi Than You Think by Sorin61

If a material strong enough to hold existed, we would have other tech instead. Such strong materials can improve compression ratios, improve engine efficiency via less moving weight, tank warfare would be dramatically different, etc.

Space elevators are built along the premise there is a material strong enough to anchor; everything else in its design is trivial. We are probably 100+ years away from a material, maybe 30 if a world war breaks out soon

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sector3011 t1_ixy7cmq wrote

It still doesn't solve the problem of elevators getting hit by debris be it space rock or junk. There is no way to avoid this since the elevator is stationary.

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dgriffith t1_ixyh54v wrote

They can be stationary but flexy.

If you can build a cable for a 40Mm long space elevator, then bending said cable sufficiently to avoid space debris by a few kilometres should also be doable.

You'd end up with waves travelling up and down the cable as it oscillates due to natural resonance anyway, you could probably augment or dampen that resonance as needed to ensure the cable avoids the big stuff along its entire length. These waves would be basically unnoticeable to cars riding the cable due to the sheer scale of things.

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NinjaFenrir77 t1_ixyagh5 wrote

That’s a problem, but not one that will prevent space elevators from being built/used. The chances of this happening are relatively small, and the damage being much less impactful than the impact of having an operational space elevator.

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TomSwirly t1_ixyg485 wrote

> The chances of this happening are relatively small,

Can we see the math?

> and the damage being much less impactful than the impact of having an operational space elevator.

Having a 35,000km structure collapse onto the Earth sounds pretty darn "impactful".

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NinjaFenrir77 t1_ixyib4o wrote

There’s not a lot of math to show until we start talking specifics of the elevator and know the materials we are working with. In general, space is pretty empty.

Are you taking about the orbiting station? Because that won’t crash into Earth, it will fly away (slowly) because it is orbiting faster than it should to have a stable orbit in order to balance out the elevator cable. A few thrusters can help it stay in a stable orbit if the cable breaks.

The cable itself isn’t a huge threat. It could potentially kill some people if it landed on them, but the scenario of it whipping into the Earth at supersonic speeds isn’t going to happen due to wind resistance and basic safety precautions.

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Harabeck t1_ixz6vua wrote

> Having a 35,000km structure collapse onto the Earth sounds pretty darn "impactful".

I might damage your roof, and it'd be a huge pain in the ass, but it's not like it'd be a tower that crushes everything beneath it.

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TheImmortalLS t1_ixz9z4v wrote

It’s the same probability as ISS getting hit, +/- a bit since the iss can go up and down. Maybe a space elevator can dodge a bit too.

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drysart t1_iy1p5nu wrote

Of all the practical problems facing a space elevator, dealing with debris is by far the easiest of them.

You don't run one cable from the ground up to orbit; you run several of them parallel to each other, spaced far enough apart from each other that no piece of debris could sever more than a certain amount of them at once. And at regular intervals down the cables, they'd be linked to each other such that if any subset of cables gets severed, the remaining cables would continue to hold the entire structure upright.

How many cables you'd need and how far apart they'd need to be would need to decided upon by dedicated research into the nature of the debris problem -- how much debris, how big it can be, etc. And then you just engineer in redundancy for the unavoidable failures to reduce their impact into being a bothersome maintenance task to repair/replace severed cables rather than a complete catastrophic disaster collapse.

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