@realcaseyrollins Think a space elevator would be bad for society or something? Or is there a joke int here that went over my head?

@freemo Over your head 😂😂😂

@realcaseyrollins

Wouldnt be the first time :)

@robryk

As I said in my post the height would be "outer space"... basically high enough that something slightly above it can maintain an orbit with low enough drag it is sustainable... basically the lower bounds of an LEO.

So LEO is ~1.2K miles

For relevance the GEO point is 22.2K miles... this is the height something needs to exceed and be fixed to earth in order to fell a force opposite to gravity at any point in its structure... The part beyond 22.2K would be pull out away from earth, and the part below pulled into earth. Since we only are discussing something of a height of about 1.2K then all of the stresses, as far as I know, should be compressive.

@robryk Keep in mind 1.2K is generous and puts you at the upper limit of LEO... if we want something more doable the lower limit of LEO is like 150 miles or so up, which would get you past the ISS.

@ech

> How high would it have to be? 100km to "space", but what application does a 100km space elevator have?

130 miles to be at the lower end of LEO and service the ISS.

1.2k miles to be at the top of LEO and service all things in LEO..

I'd say that since it facilitates easily bringing fuel to space putting it at the lower end is fine since now there is enough fuel for them to get to a higher orbit anyway.

> I found something saying that 10 miles is the max mountain height, but I think that was taking into account how fast mountain growth processes are vs. erosion, so I don't think it applies to this project: we can probably go quite a bit higher.

Yea its hard to say how this might translate over to a man made structure though, thats the problem.

> I agree it seems like if you go wide enough the rocks can probably support 100km without basically liquefying and squishing outward? I think? But I think the crust will deform a ridiculous amount, so be sure to take that into account. :)

Yea it is both these effects im not sure about... I know if you dig even 1 mile down the pressures are so high that the walls of your tunney will slowly move like a liquid and close in unless you reinforce them... go too much deeper and even reinforcement doesnt work.

The depest we ever dug was 7.6 miles.. but im not sure if the limiting factor has any relationship to this...

@freemo "130 miles to be at the lower end of LEO and service the ISS." But it's whizzing by at 5 miles/sec; most of the work is just getting up to speed, isn't it?

I guess the higher up you go the better, (less air etc?), but unless your elevator is quite a bit higher than these numbers you don't really get the main savings of a space elevator.

@ech Do you though? The point of a space elevator is to save you fuel.

avoiding the most fuel expensive part (getting out of the atmosphere where drag is significant) seems it would be a huge save, especially since now you can pump fuel to that point and not need to lift it there via rocket.

@freemo I think the expensive part is getting enough horizontal speed. Taking off at LEO-heights, you avoid air and the need to gain potential energy. This is like a fifth of the fuel or something. But sure: not nothing.

@ech I was thinking more in terms of something already in orbit being able to pick up supplies from the elevator, including fuel, and then taking that to a higher orbit or escape velocity.

But now that i think of it your right, the thing would be moving so fast past the space elevator it wouldnt have time to pick up the items, and even if it had some sort of hook or something the speed would just not be managable...

That said if it could somehow pick up the supplies it could work, it would just have to pick the up the fuel then immediately use it to speed up as it would get slowed down by trying to pick it up.