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Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

publications.anl.gov

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Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#31

Post by JumpCrisscross »

schiffern wrote: post #30
JumpCrisscross wrote: post #22

Earlier quoted context omitted.

> How is the elevator car in a space elevator accelerated horizontally? Momentum transfer from the cable, which is attached to an orbiting counterweight. In this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field. In general one boosts the counterweight directly or, more practically, by sending things down [1]. [1] https://space.stackexchange.com/q…

This paper's design has no orbiting counterweight, and only reaches an altitude of 200 km. A launch loop can harvest energy and momentum from the rotor to accelerate payloads, but I don't see any such mechanism here.

> This paper's design has no orbiting counterweight

Which is why I say I “in this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field.” The cable is an electrostatic counterweight because we’re using electromagnetism, not the comparably weak gravitation.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#32

Post by JumpCrisscross »

spacebacon wrote: post #29

Several prompts later … The gap between current material science and the required advancements for constructing a magnetically levitated space elevator is significant. Let's break down the key areas where advancements are needed and assess the current state compared to the required state: 1. Superconducting Materials Current State: NbTi Superconductors: NbTi (Niobium-Titanium) superconductors are among the most commo…

> major hurdle is the ability to produce continuous lengths of high-quality CNTs

What is an intermediate market for medium-length high-quality CNTs?

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#33

Post by la64710 »

What about the birds and the planes flying into the elevator cables? Is any othe thinking about it? Where do these crazy ideas come from? And what happens when they break and the cables fall to the earth? time we start thinking long term impact on the planet and its life for our ideas.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#34

Post by kimixa »

la64710 wrote: post #33

What about the birds and the planes flying into the elevator cables? Is any othe thinking about it? Where do these crazy ideas come from? And what happens when they break and the cables fall to the earth? time we start thinking long term impact on the planet and its life for our ideas.

There's already plenty of other things of a similar scale in the path of birds and planes currently. Such as other planes. But these being stationary probably makes them even easier to avoid.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#35

Post by mikewarot »

If we're pushing "out of the box" ideas, why not just use hydrogen balloons to hold up a railgun for the first 20,000 meters of altitude? The ambient pressure at the end would be about 1/10th of that at sea level. You could have outriggers with a very thin high voltage power line to enable station keeping via thrusters (repurposed quadrotor parts?)

I wouldn't be surprised it the ambient electrostatic field from the atmosphere were sufficient to power station keeping, or at least some of the instrumentation.

If that works, I'm sure they could extend it to twice as long, almost into space.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#36

Post by [deleted] »

ben_w wrote: post #19
punnerud wrote: post #17

Earlier quoted context omitted.

The Starship was only for moving coolant, not as part of the elevator. I was thinking you probably have to have extra payload to stop the end. And that it then would be better to start from the top, than from bottom

I can't visualise what you're trying to suggest. "Stop the end"?

[deleted]

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#37

Post by schiffern »

JumpCrisscross wrote: post #31
schiffern wrote: post #30

Earlier quoted context omitted.

This paper's design has no orbiting counterweight, and only reaches an altitude of 200 km. A launch loop can harvest energy and momentum from the rotor to accelerate payloads, but I don't see any such mechanism here.

> This paper's design has no orbiting counterweight Which is why I say I “in this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field.” The cable is an electrostatic counterweight because we’re using electromagnetism, not the comparably weak gravitation.

Problem is "some of the momentum" isn't nearly enough to reach orbit (climbing the tower only gains you 3% of orbital speed, or 0.1% the kinetic energy), and there's no hint of a mechanism that's supposed to accelerate a payload the rest of the way to orbital speed.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#38

Post by monkeyfun »

mikewarot wrote: post #35

If we're pushing "out of the box" ideas, why not just use hydrogen balloons to hold up a railgun for the first 20,000 meters of altitude? The ambient pressure at the end would be about 1/10th of that at sea level. You could have outriggers with a very thin high voltage power line to enable station keeping via thrusters (repurposed quadrotor parts?) I wouldn't be surprised it the ambient electrostatic field from the a…

Relatedly, have you ever heard of skyhook? Not the CIA one but the orbital infrastructure concept -- lets you literally just take a supersonic capable plane with no rocket engines whatsoever into space.

Always love that concept with how it's actually engineer-able with current materials and sounds like it shouldn't work until you look closely.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#40

Post by schiffern »

Benjammer wrote: post #27
stretchwithme wrote: post #21

How is the elevator car in a space elevator accelerated horizontally? That's what reaching orbit is, right? Horizontal acceleration? The car starts out on the ground at 465m/s. It has to accelerate to 11,068 km/h. What makes it accelerate? The cable, without any force applied to it anywhere? Or is there a rocket on that car? To put mass into orbit, you have to accelerate that mass. And do it without decelerating the…

One thing with a space elevator that makes it so much more efficient than rockets is precisely because you don't necessarily need the payload itself to supply this horizontal acceleration. The space elevator is attached to the ground at one end, and the other is way up in orbit. There must be forces in play _already_ for the entire thing to stay standing, before you get to any concept of a payload/car. Part of the id…

>you don't necessarily need the payload itself to supply this horizontal acceleration. The space elevator is attached to the ground at one end, and the other is way up in orbit.

On a conventional space elevator this is true. You just go up to 35,786 km altitude (AKA geostationary orbit) and let go.

However the structure described in this paper only goes up to 200 km altitude, so it still needs a horizontal acceleration system.

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