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

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

#81

Post by dredmorbius »

throw310822 wrote: post #20
dredmorbius wrote: post #18

Earlier quoted context omitted.

Do you have any idea which mission that was? Wikipedia has a listing, if that helps: https://en.wikipedia.org/wiki/Space_tether_missions >

TSS-1R mission, 1996 "TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation." "Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three"

Thanks, I seem to remember that vaguely.

I've also had the idea for a while (probably inspired by that mission) that any actual space elevator would be hugely influenced by magnetic and electrical influences, becoming a tremendously long conductor and/or static-charge accumulator.

You'd probably want it to be exceptionally well grounded, and want to take precautions embarking or disembarking.

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

#82

Post by hinkley »

throw310822 wrote: post #20
dredmorbius wrote: post #18

Earlier quoted context omitted.

Do you have any idea which mission that was? Wikipedia has a listing, if that helps: https://en.wikipedia.org/wiki/Space_tether_missions >

TSS-1R mission, 1996 "TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation." "Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three"

What I was never clear on is whether that makes them more interesting or less realistic.

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

#83

Post by pfdietz »

This was an extension of the MCKESR (Magnetically Confined Kinetic Energy Storage Ring) concept Hull was exploring at ANL. The idea here is a ring-shaped flywheel where the centripetal force is supplied by magnetic forces rather than strength of the rotating ring. The advantage is that the stored energy per mass of ring + magnets scales linearly with radius, unlike in a conventional flywheel where (by the virial theorem) the ratio is limited by a constant factor proportional to the strength of the flywheel material divided by its density.

The original MCKESR concept had a ring-shaped conductor orbiting in a magnetic field, but a later concept had a chain of ferromagnetic objects being attracted magnetically. The latter was kept passively stable by alternating segments of magnets, one segment where the attraction was stable radially and unstable vertically, the next the opposite. If the ring was moving in the right speed range this would cause dynamic stability in both directions. This Alternating Gradient principle is used (via magnetic forces on moving charged particles) to focus beams in most modern particle accelerators.

https://ieeexplore.ieee.org/document/4765896

https://digital.library.unt.edu/ark:/67531/metadc173309/

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

#85

Post by dredmorbius »

hinkley wrote: post #82
throw310822 wrote: post #20

Earlier quoted context omitted.

TSS-1R mission, 1996 "TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation." "Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three"

What I was never clear on is whether that makes them more interesting or less realistic.

The one thing that's clear is that this makes tethers a more challenging engineering problem than a naive / uninformed view might have suggested.

This is almost always the situation in engineering applications. The simple approach based on first principles turns out to be massively influenced by second- and higher-order effects. See Admiral Hyman Rickover's "Paper Reactors" for a classic take on this:

https://whatisnuclear.com/rickover.html>

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

#86

Post by spacebacon »

ben_w wrote: post #75
JumpCrisscross wrote: post #32

Earlier quoted context omitted.

> major hurdle is the ability to produce continuous lengths of high-quality CNTs What is an intermediate market for medium-length high-quality CNTs?

Presumably anything that wants a "medium"* length very strong cable; civil infrastructure comes to mind, might be useful for suspension bridges? * quotes because all things are relative, by "medium" in the context of a space elevator you may have meant "continent sized"?

Current maximum continuous length is about a foot.

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

#87

Post by chmod775 »

askvictor wrote: post #54
tadfisher wrote: post #52

Earlier quoted context omitted.

The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.

Depends where the tether breaks. If it's somewhere along the middle, then the Earth-side section would fall to Earth. KSR's Mars trilogy examines the impacts (pun intended) of this.

Even an optimal space elevator needs to support a sizable portion of its own tether weight with the tether itself.

For a solid non-magnetic tether to be at all realistic, the tether material would likely be so light relative to it's length/volume, it'll never be at all dangerous regardless of how high you drop it from - its terminal velocity would be tiny.

I can drop some yarn, fishing line, whatever, from whichever height I want and it will never be dangerous to anything on the ground. Same principle.

I dont know about magnets, but I suppose the same applies here: If your tether isn't light, its own weight will add a stupid amount of stresses that would likely deform any load-bearing metal. Probably the magnets themselves in this case.

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

#88

Post by ben_w »

spacebacon wrote: post #86
ben_w wrote: post #75

Earlier quoted context omitted.

Presumably anything that wants a "medium"* length very strong cable; civil infrastructure comes to mind, might be useful for suspension bridges? * quotes because all things are relative, by "medium" in the context of a space elevator you may have meant "continent sized"?

Current maximum continuous length is about a foot.

At present. From context, I infer the question is "we know what we can use 1cm long carbon nanotubes for, and what we can use 36,000 km long carbon nanotubes for, but what economic value is there for stuff between such that we may try to monetise the R&D pathway to the latter?"

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

#89

Post by amy-petrik-214 »

s1artibartfast wrote: post #62
pdonis wrote: post #50

Earlier quoted context omitted.

> thats what the railgun is for A railgun that can provide a delta-v of 8 kilometers per second?

Yes, that would be the proposal. Existing ship mounted railguns already shoot projectiles around 3km/s. It is generally thought that they could be scaled up to 8 km/s and larger size. The main problem is that if you fire human sized objects that fast at sea level you end up with a plasma ball due to air friction. This isn't an issue with chemical rockets because they start at 0 and accelerate to Vmax, whereas the rai…

[flagged]

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

#90

Post by RecycledEle »

more_corn wrote: post #59
tadfisher wrote: post #52

Earlier quoted context omitted.

The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.

But if you break the tether halfway down the bottom half falls at 16,000 mph right? And then it’s burning and then it cracks like a whip. I don’t know about extinction, but not a fun time for anyone.

Not 16,000 mph. A very lightweight tether (thing tie down straps) will drift down and land softly.
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